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Safe manriding in minesSecond Report of the National Committee for Safety of Manriding in Shafts and Unwalkable Outlets Parts 2A and 2B

This is a web-friendly version of Safe manriding in mines: Second Report of the National Committee for Safety of Manriding in shafts and Unwalkable Outlets, originally produced by HM Inspectorate of Mines

The National CommitteeA National Committee for Safety of Manriding in Shafts and Unwalkable Outlets was formed and first met on 3 December 1973 and their first report was published in 1976. The Committee commenced work on their second report on 23 March 1976, the members being as follows:

Chairman J D Blelloch Director of Engineering, National Coal Board

Deputy S Luxmore, HM Principal Electrical Inspector of Mines and Chairman Quarries, Health and Safety Executive

Members T K Clanzy HM Principal Inspector of Mechanical Engineering in Mines and Quarries, Health and Safety Executive

J B Hall Chief Mechanical Engineer, National Coal Board

H M Harrison Mechanical/Electrical Inspector, National Union of Mineworkers

R Hartill Chief Electrical Engineer, National Coal Board

L C James Head of Technical Services, Mining Research and Development Establishment, National Coal Board

E Loynes Representing the Association of Mining Electrical and Mechanical Engineers

H D Munson Head, Engineering Group, Safety in Mines Research Establishment, Health and Safety Executive

A Rushton Representing the British Association of Colliery Management

A J Williams Chief Maintenance and Energy Engineer, National Coal Board

Secretary G Scott HM District Inspector of Mines and Quarries, Health and Safety Executive


Safe manriding in mines: Second report of 177

This is a web-friendly version of Safe manriding in mines: Second Report of the National Committee for Safety of Manriding in Shafts and Unwalkable Outlets, originally produced by HM Inspectorate of Mines

London: Her Majesty’s Stationery Office

© Crown copyright 1980

First published 1980

ISBN 0 11 883281 6




ForewordIn publishing this second report the committee has completed work on its terms of reference. A section on unwalkable outlets has not been included as many of the principles and recommendations for shafts are considered to apply. The report is in two parts: Part 2A contains considerations, conclusions and recommendations on other items of winding equipment and installations not specifically referred to in the first report; Part 2B contains supporting technical information and guidance on practice.

A new committee, having similar representation to the National Committee has been formed to review periodically experience on the application of the first and second Reports on Safe Manriding in Mines, and to make proposals, as appropriate. Information on the work of this committee will be included in the HSE Annual Reports on health and safety in mines.

I wish to thank the representatives of all the interested parties for their valuable help and co-operation in fulfilling the committee’s terms of reference. I have no doubt that these two reports will make a positive contribution to the safety aspects of manriding in mines.

J S MARSHALL HM Chief Inspector of Mines and Quarries

Note: The Mines and Quarries Inspectorate is now part of the Health and Safety Executive, consequently Mines and Quarries forms referred to in the text will in future be issued by the Health and Safety Executive,




Contents of Report – Part 2A 1 Introduction 7

2 Winding engines 8

General statement 8 The design guide 8 Guidelines for fabricated, cast and forged components 9 Bolted anchorages for winding engine brakes 10 Contamination of winding engine brake lining materials 10 Retention of electrical braking 11 Automatic application of dynamic braking on AC winding engines 11 Automatic application of electric braking on DC winding engines 12 Brake torque sensing 12 Automatic contrivances: electrical aspects 12 Supervisory devices for automatic contrivances 13 Conveyance position monitoring 13 Emergency brake solenoids 14 Control system safety 15 Electric winding engine drums and drives 17 Steam winding engines and auxiliaries 19 Friction between rope and drum 19 Assessment of reliability of systems 20 Emergency winding apparatus 20

3 Headframe and shaft equipment 21

Design principles for arresstors in friction winding installations 21 Pit bottom buffers 23 Conveyance suspension gear 24 Conveyances for manriding 26 Winding ropes 27 Rope and rigid guides 28 Balance ropes 31 Control of balance rope loops 32 Monitoring of balance rope loops 32 Termination of wire ropes 33 Shaft side equipment 33 Shaft signalling systems 38 Headframe pulleys 40

4 Maintenance, testing and training 41

Statutory reporting 41 Planned activities related to mining environment 41 Maintenance procedures and documentation 41 Maintenance of foundations, buildings, structures and shaft linings 43 Maintenance of equipment in towers, headframes and sumps 43 Maintenance of ropes in winding installations 44 Lasers and other devices for aligning shaft equipment 45




Protection of steelwork from corrosion 45 Shaft air heating 45 Non-destructive testing of components of winding apparatus 46 Reassessment of non-destructive testing 46 Monitoring of mechanical equipment 49 Testing of friction winding engines 50 Brake performance test 50 Training for work in shafts 52

5 Other winding practices 53

Control systems: push button winding 53

6 Abstract of recommendations 54

7 Further work 58

Part 2B (including list of contents) 59




PART 2APrinciples and recommendations for Shafts




1 Introduction2 The first report, Parts 1A and 1B, of Safe Manriding in Mines was published in one volume in 1976 following the Public Inquiry into the winding accident at Markham Colliery, Derbyshire, in 1973. A new philosophy of braking for winding engines is set out in the first report with recommendations for implementing that philosophy. Information is also provided, and recommendations are made, on headframe and shaft equipment, maintenance, testing and training, and other winding practices.

2 The first report was published as soon as possible so that guidance on improving standards of braking and associated equipment of winding engines could be provided in advance of more general considerations. Items then outstanding, including incomplete work and some new subjects, are scheduled in section 7 of Part 1A. The terms of reference given to the National Committee for Safety of Manriding in Shafts and Unwalkable Outlets were moreover TO CONSIDER ALL SAFETY ASPECTS OF MANRIDING IN SHAFTS AND UNWALKABLE OUTLETS AND TO MAKE RECOMMENDATIONS.

3 This second report is similarly published in Parts 2A and 2B in one volume, and generally follows the arrangement of Parts 1A and 1B. It contains the necessary supplementary information and recommendations to comply substantially with the terms of reference. Furthermore, as a result of experience in implementation of recommendations in the first report, it has been felt necessary to make changes in respect of non-destructive testing; and these are referred to in the text.

4 The sub-committees and working groups, formed by the National Committee for the production of the first report, were reconstituted to produce the second report and have now been disbanded. The National Committee recommends however that a committee remains in being and meets periodically to review developments in manriding in shafts and the further work scheduled in section 7 of Part 2A.

5 Safe manriding in unwalkable outlets has not been separately considered because many of the standards applicable to winding in shafts apply equally to winding in unwalkable outlets and major drifts. With regard to safe manriding in underground roadways, a Haulage and Transport National Steering Committee was formed in 1975 to make recommendations and produce a Safety Catalogue of information on safety standards, practices and design of systems and equipment, with the object of reducing accidents resulting from transport operations.




2 Winding engines

General statement

6 Part 1A discusses the philosophy of winding engine braking with the objective that a mechanical brake should be capable of bringing a winding system safely to rest even in the event of failure of one component. Bringing a winding system safely to rest is primarily defined as reducing the speed at least to that which can be accepted by pit bottom arresting devices. For these purposes, the emergency braking force is assumed to be reduced by not more than 50% and this is further discussed in paragraph 83.

7 Part 1A also discusses related matters including initiations of mechanical braking, but safe manriding in shafts is affected by failure or malfunction of all relevant components of winding engines: and this section extends the discussion to a wider range of such components including their operational aspects.

The design guide

8 In Part 1A paragraphs 4, 13(5), 14 and 111(4) there is reference to a design guide for winding engine brake components. A description of the proposed content and an explanation of the Reserve Factor concept are in section 1 Part 1B. Since the publication of Part 1, a draft of the design guide prepared by the National Coal Board and SMRE* has been issued to the Health and Safety Executive and British suppliers of winding engines and brake gear components.

9 An introduction in the guide sets out its aims, includes some fundamental design considerations, draws attention to the importance of fatigue and defines the Reserve Factor concept. After the introduction the guide is divided into basic chapters, working chapters and background information chapters. The content of these is shown in the following lists:

(1) Basic chapters

Fatigue design Bending and dynamic factors for fatigue design Theoretical fatigue strength of a pin in a pin joint Fatigue of welded components Adjacent and superimposed stress concentrations Resolution of forces in a caliper brake Structural analysis moment distribution method (Hardy-Cross).

(2) Working chapters

Screwed rods Analysis of fatigue of shafts Design for welding Compression members Determination of stresses in brake shoes Analysis of stress in typical welded brake shoe Fatigue strength of a pin in a socket Bushes for linkages

* Safety in Mines Research Establishment, Health and Safety Executive.




(3) Background information chapters

Examples of good and bad design for machined and welded components General requirements for mechanical brakes Recommended materials for mechanical brakes Stress concentration data Proformae for calculations.

10 Development of the guide is continuing on the basis of comments received and experience of utilisation; it is being refined, amended and, where appropriate, supplemented. Progress has already been made in establishing a common approach to the problem of design of mechanical brake components. Computer programmes which have been compiled will contribute to this and also ease the burden of calculation, including calculation of safe definitive life for components where necessary. Typical programmes are as follows:

Resolution of forces in a caliper brake Analysis of stresses in screwed rods Determination of stresses in brake shoes Analysis of fatigue of brake shafts Analysis of fatigue of pins Design of compression members Design of actuating levers Design of brake actuating springs.

11 The guide is now at the stage where the first edition will shortly be available. Additional chapters giving information on brake holding down bolts and brake actuating springs have been included.

12 The scope of the guide will be widened by the preparation of association monographs to cover stress analysis and material data for disc brakes, data for analysis of stresses in headframe pulleys and shafts, and data for analysis of stresses in drum shafts. For drum shaft analysis the existing brake shaft computer programme will be extended.

13 Specific investigations into mechanical brake components using methods and data from the guide have resulted in amendment of some designs to increase the Reserve Factor. Analysis of components withdrawn from service in which cracks have been detected showed good correlation between actual life and that which would have been predicted by design guide methods.

Guidelines for fabricated, cast and forged components

14 In Part 1A, principles of selection of materials for the construction of mechanical brakes are discussed and a list of recommended materials is in section 4 of Part 1B. Experience of use of these materials for both new and replacement parts has been successful but the list has been enlarged and is in Part 2B, section 1.

15 The need for manufacturing mechanical brake parts to a satisfactory standard to ensure reliability in service is referred to in Part 1A paragraphs 18 and 19. Guidelines to be observed to achieve satisfactory quality are in Part 1B sections 6 and 7. These guidelines should be adopted for the manufacturer of winding engine main drive components and headframe pulleys.

16 Where there is high risk of lamellar tearing in fabrications, the use of plate with adequate resistance to this mode of failure is required. Suitable steels are available and it is recognised that the reduction of area of a tensile test specimen taken from




a plate in the short transverse direction (ie plate thickness direction) provides a guide to plate susceptibility to this risk. To avoid lamellar tearing, plates specified should have a minimum reduction of area of 20% in the short transverse direction.

17 Large forgings from which items such as shafts are made should be ultrasonically tested after forging to detect flaws. These forgings would normally be in carbon or carbon manganese steel and to appropriate requirements of BS 29: 1976 when above 6 in (150 mm) ruling section.

Bolted anchorages for winding engine brakes

18 For thirty years there has been no evidence of significant failure of foundation or holding down bolts in brake anchorages in NCB winding installations. Nevertheless, because of the importance of brake anchorages, present foundation bolt practice has been reviewed and holding down bolts for brake posts, calipers and unit brakes have been studied so that existing installations may be checked and new anchorages designed to consistent standards. Attention has been focussed on two aspects of such anchorages: namely, the design of individual holding down bolts; and the determination of the distribution of anchorage loads amongst bolt positions.

19 Firstly, each bolt is subject to load fluctuation as a mechanical brake is operated and must therefore have adequate fatigue strength. Load fluctuation at each bolt position is taken partly at joint faces and partly by the bolt itself. Fluctuation of stress imposed upon each bolt can be minimised by providing stiff anchor brackets and a suitable pre-load to maintain positive pressure at joint faces under all service load conditions. Bolts can also be subject to bending stresses, arising from practical factors such as lack of squareness of nut faces or slight deformation of mating parts. Under fluctuating loads these additional bending stresses can contribute significantly to the total service stress range. By careful design and installation, this stress range can be kept within limits which should ensure that holding down bolts have infinite fatigue life.

20 Secondly, it may occasionally be difficult to estimate the share of total anchorage load taken at each bolt position. Many anchorages have bolts in small groups where the nominal loading at each bolt position can readily be estimated by conventional methods; but in larger groups of bolts, especially where asymmetric loading is involved, theories available provide only rough estimates. Considering a practical case of asymmetric loading, such as illustrated in Part 1B, section 3, fig 3.4, measured bolt stresses were compared with several calculated values and lack of good correlation indicated that further study of design methods is required.

21 A chapter has therefore been included in the design guide, as referred to in paragraph 11, with information on anchor bolt design, pre-load levels and methods of estimating distribution of anchorage loads amongst bolts in a group. Complex cases may require individual study. Also included is a reference to methods available for limiting variation in pre-loads; this is often difficult to achieve in practice as, for instance, identical applied torques can produce different pre-loads depending on frictional conditions at the threads and nut faces.

Contamination of winding engine brake lining materials

22 Occasional incidents are reported of temporary loss of mechanical braking performance due to contamination (see paragraphs 3 and 6 of Part 1A): causes and precautions against it are listed in appendix 8.6 of Part 1B. Priority should be given to the prevention of contamination by careful positioning of oil pipes, design of lubricating systems, shielding of brake paths and control of winding engine house environments. Total prevention is however difficult to achieve and should




contamination of a brake path or lining occur it is essential that it be detected. It is also important that materials used for winding engine brake linings should have performance characteristics that are least affected by contamination.

23 Laboratory tests have been carried out, in conjunction with manufacturers of brake lining materials, to assess the effects of contamination on a range of moulded and woven brake lining materials by water, hydraulic mineral oil and rope lubricant. The test results exhibited the wide scatter typically encountered in friction measurements but brought out the following points:

(1) Mineral oil caused the greatest reduction in performance in all tests and this reduction was not recoverable.

(2) Rope lubricant also caused substantial and non-recoverable reductions in performance.

(3) Water caused substantial reductions in performance but this could be recovered by drying out. Furthermore, moulded lining materials operate at higher pressures, disperse water more rapidly and absorb less water. Therefore, loss of friction was generally less than with woven materials and recovery more rapid.

24 Conclusions:

(1) None of the brake lining materials tested was sufficiently superior to the others in its resistance to contamination to enable changes to present practice to be recommended. Since contamination by rain water or condensate can affect all brake paths simultaneously, the lower absorption and rapid recovery characteristics of moulded linings are advantages.

(2) Apart from visual inspection and testing the most satisfactory method of detection of contamination would be measurement of mechanical brake performance by brake torque sensing devices, as described in Part 2B, section 2, or other means.

Retention of electrical braking

25 It is recommended in paragraph 71(v) of the Markham Official Report that ‘the control systems of electric winding engines be reviewed with the object of making electrical braking available after the initiation of an emergency or automatic trip at least until the application of the mechanical brake has been proved’. It was subsequently recommended in paragraph 33(1) of Part 1A that ‘The objective be pursued for DC and AC winding engines that after the initiation of an emergency or automatic trip, electrical braking is retained without the intervention of the winding engineman until the mechanical brake is proved substantially effective’.

Automatic application of dynamic braking on AC winding engines

26 At present, dynamic braking on AC winding engines is available to the winding engineman for manual application after an emergency trip except in the case of total power failure. The scheme described in section 11 of Part 1B, for automatic application of dynamic braking following an emergency trip, has the disadvantage that, in the event of failure of the mechanical brake to retard the winding engine after removal of dynamic braking, the winding engineman cannot regain dynamic braking. Re-examination of this scheme has shown that it can be modified so that dynamic braking can be automatically re-applied in this event. Paragraph 33.2 of Part 1A indicated that trials should be pursued with the automatic application of




dynamic braking and in consequence of this a system has been installed at a colliery, which provides a satisfactory approach to automatic application of dynamic braking without the intervention of the winding engineman, following an emergency trip and possible reduction in the effectiveness of the mechanical brake.

27 This system monitors drum retardation after an emergency trip, using a DC tachogenerator to compare actual speed with desired speed following the trip, to bring the conveyances down to creep speed at a pre-programmed rate of retardation. Since these trials show satisfactory results, the system should be further developed and trials extended. A brake torque sensing device is not required for this system.

Automatic application of electric braking on DC winding engines

28 Electric braking on DC winding engines is inherent in their control schemes, but its automatic application following an emergency trip required development of a transducer to sense effectiveness of mechanical braking. Development of a mechanical brake torque sensing transducer is now considered to be successful as referred to in the next subsection. The next stage is to incorporate this development into existing DC winding engines to achieve automatic application of electric braking following an emergency trip. Winding engine manufacturers are currently involved with the NCB in engineering application of this apparatus to DC winding engines.

Brake torque sensing

29 Paragraph 34 of Part 1A states that ‘if electrical braking on winding engines is to be retained automatically following an emergency or automatic trip until the mechanical brake has been proved substantially effective, a reliable brake torque sensing transducer is required’. While systems are available which can indicate brake movement and pressure, the indications can be misleading in cases where brake linings or paths are contaminated. A system is needed which takes account of the coefficient of friction by indicating a satisfactory degree of mechanical braking torque. One way of doing this is to provide a system which can detect the reactive torque developed, by using an arrangement of transducers which can monitor strains produced in either brake shoes or pivot pins. The output from the system can be used to control removal or re-application of electrical braking. An account of the development of such a brake torque sensing apparatus is in Part 2B, Section 2.

30 Conclusion:

Trials have shown that the system adopted for measuring reactive forces in structures of caliper brakes is suitable for sensing and monitoring their reactive torque; and for enabling the objective of paragraph 33(1) of Part 1A to be pursued.

Automatic contrivances: electrical aspects

31 Recommendations for mechanical aspects of automatic contrivances are in Part 1A, paragraph 42, and Part 1B, sections 13 and 14. Reference was also made in Part 1A, paragraph 38, and Part 1B, section 14, to examination of the electrical aspects of category A type automatic contrivances and these aspects are referred to in Part 2B, section 3. The acceleration relief feature in some devices was also referred to in Part 1A, paragraph 39, and the need was stated for this to be designed to fail to safety.




32 The automatic contrivance is an important apparatus which initiates braking and removes driving power in association with the safety circuit, when either overspeed or overwind occurs. The integrity and reliability of this device should be of a very high order and wherever possible it should be designed to fail to safety. Standards for and methods of achieving the above desirable features are detailed in Part 2B, section 3.

33 Recommendations:

(1) All new automatic contrivances be designed to incorporate the features described in paragraphs 31 and 32 and in Part 2B, section 3.

(2) All existing category A type automatic contrivances be modified at the time of major overhaul to incorporate the features described in paragraphs 31 and 32 and in part 2B, section 3.

Supervisory devices for automatic contrivances

34 In Part 1A, paragraph 42(6), it is recommended that automatic contrivances and protective equipment be monitored or provided with a separate supervisory device. Examination of these alternatives has led to the conclusions that to monitor the various elements of an automatic contrivance would be complex; and that the better method is to use a separate supervisory device as described in Part 1B, section 16.

35 Successful trials of two types of prototype digital supervisory devices have established the principles of operation. The devices have the protective features of automatic contrivances and check that contrivances function satisfactorily by shadowing those elements of contrivances that monitor winding engine speed and distance.

36 In addition to its primary function the supervisory device may be used for other functions, ie:

(1) providing data for recording winding engine retardation, details of the winding cycle and results of statutory tests;

(2) slack rope protection; and

(3) monitoring the creep compensation device.

These other functions should be carried out by a separate electronic section that is electrically isolated from the supervisory section (eg by optical coupling) to avoid interference with the primary function of this device, namely to shadow the automatic contrivance. Facilities (2) and (3) are obtainable when the device is used in conjunction with magnetic marking of winding or guide ropes.

37 Conclusion:

Provision of separate supervisory devices as referred to in recommendation 42(6) of Part 1A is preferable to monitoring automatic contrivances on winding engines; and such separate supervisory devices should have the feature described in this subsection and in Part 2B, section 4.

Conveyance position monitoring

38 Paragraph 99(1) of Part 1A recommends that systems be examined with a view to providing continuous indication of the position of a conveyance in addition to that of the winding engine drum or sheave. Paragraph 82 of Part 1A




recommends that development be pursued of a fail-safe system of slack rope protection which compares movement of a conveyance with that of the drum or sheave throughout a wind. Since Part 1A was published, development work has proceeded which appeared to offer solutions for both slack rope protection and conveyance position monitoring. Investigations have also been made into creep compensation devices used by the NCB: these have confirmed that there have been very few incidents associated with this type of equipment although there have been component failures and malfunction of shaft proximity switches.

39 Supervisory devices for automatic contrivances are described in the previous subsection and in Part 2B, section 4. Development of magnetic markings of winding and/or guide ropes is continuing and is described in Part 2B, section 5: the system appears capable of efficiently indicating the position of a conveyance. A method of communication between conveyance and surface has been developed for use with magnetic marking and is also described in Part 2B, section 5. It is intended to use magnetic marking in conjunction with supervisory devices to detect slack rope and to monitor rope slip and creep. To this end, it is proposed to utilise a supervisory device which has two self-checking micro-processors: magnetic marking signals will be fed to one and the output from a winding engine drum position transducer to the other. A comparator will check the two signals and indicate any discrepancy such as that due to slack rope, rope slip or creep. The system could furthermore provide audible and visual alarms and directional signals as recommended in paragraphs 82(3) and (4) of Part 1A. For slack rope protection, an amplified error signal could be used to trip the CATEGORY 1a safety circuit of a winding engine referred to in paragraph 46 of Part 1A. For conveyance position monitoring, an accurate count of magnetic marks on either a winding or guide rope can be displayed in the winding engine house or can be utilised to operate rope slip detection equipment. Although creep compensation devices have proved reliable, they are single line components and consideration should be given to using supervisory devices, with magnetic rope marking, to monitor their operation.

40 Infra red distance measuring techniques have been investigated as an alternative to magnetic marking of ropes. Shaft environments and distances resulted however in insufficient reliability and accuracy; and infra red techniques are therefore considered unsuitable for this duty.

41 Conclusions:

(1) Tests demonstrate that data from magnetic rope marking can be used in conjunction with a supervisory device to indicate conveyance position, measure rope speed, provide slack rope protection, and detect rope slip or creep on friction winding engines.

(2) Tests show that communicating links from conveyance to surface can provide four channels for data transmission and a two way channel for audio communication. These could be used for shaftsmen’s signals and speech from the top of a conveyance and for communication from inside a conveyance to the surface.

Emergency brake solenoids

42 In Part 1B, section 19, paragraph 4, reference is made to the reliability, monitoring and cross inter-locking of brake solenoids so that they operate correctly. In the controls of a winding engine, one emergency brake solenoid would be a single line component between the trip initiating device and the mechanical brake valve, and its satisfactory operation would be essential for the application of the mechanical brake in an emergency. There should therefore be at least two




solenoids each with an associated brake valve, and fluid connections to the valves should be in parallel, as required by recommendations 23(1) and 23(2) of Part 1A. Each solenoid circuit should moreover be a duplicate of the other and the Systems Reliability Service* endorse this arrangement.

43 It is also essential that a winding engine safety circuit cannot be reset if either of the emergency brake solenoid valves fails to operate. Recommendations 23(1) and 23(2) in Part 1A refer. This requires that the function of each valve is monitored and checked to enable the necessary interlocking to be effected. Ways of achieving this monitoring are illustrated in Part 2B, section 6.

44 Recommendation:

Means, such as a push button, be provided in each emergency brake solenoid circuit for independently testing the operation and interlocking of each emergency brake valve; and these means be accessible only to authorised persons.

Control system safety

45 Normal overload, overwind and overspeed protection takes care of the majority of control scheme faults but undesirable circumstances may arise if:

(1) excessive power is applied to a winding engine motor while the mechanical brake is attempting to hold the drum stationary;

(2) a winding engine moves in the opposite direction from that selected by the power lever;

(3) excessive power is unexpectedly developed by a winding engine when at creep or shaft examination speeds;

(4) instability occurs in a closed-loop control system;

(5) a winding engine is stationary, the brake lever is not in the on position, the safety circuit is energised and pumps or compressors supplying pressure to the mechanical brake are started; or

(6) a conveyance moves when the system is changed from one control mode to another.

These are considered in detail in paragraphs 46 to 51 inclusive followed by a summary of recommendations in paragraph 52.

46 Excessive power applied to a winding engine motor while the mechanical brake is holding the drum stationary

(1) AC winding engines (open-loop) In almost all winding engines in this category, two simulataneous electrical faults, would have to occur in the control circuits for this undesirable circumstance to obtain. These could be a fault which causes the main contractor to close, together with another whereby the external rotor resistance is reduced so that the winding engine motor develops sufficient torque to drive through the mechanical brake. The circumstance could also occur if only the first fault applies and the mechanical brake is not fully effective.

* See Part 1B, section 21, paragraph 1.




(2) AC winding engines (closed-loop) With winding engines in this category, a fault which causes the forward or reverse contractors to close and power to be applied to the winding engine motor could also cause this undesirable circumstance. To prevent power from being applied by a fault, an additional circuit in the control system would be needed. This circuit should trip the main circuit breaker should such a fault occur when the drum is at rest and the winding engineman’s power lever is in the off position.

(3) DC winding engines (open-loop and closed-loop) With winding engines in these categories, a fault may cause excessive current to flow in the main DC loop when the power lever is in the off position, the mechanical brake on and the drum stationary. To prevent this undesirable circumstance, it is possible to devise a circuit which will detect current in the main DC loop that exceeds a predetermined limit and trip the safety circuit in this event.

47 Movement of a winding engine in the opposite direction from that selected This could occur if a winding engineman does not ensure that there is sufficient torque to move the out of balance load in the intended direction. Circuits can be devised to detect this occurrence but if a trip is initiated a conveyance may continue to move in the wrong direction owing to the time lag inherent in application of the mechanical brake. This is undesirable. It is not possible to devise circuits to protect against a winding engineman’s selection of the opposite direction from that intended; but circuits can be arranged to protect against movement of a winding engine in the opposite direction from that selected owing to a fault. For example, it is normal practice to cross interlock forward and reverse contactors on AC winding engines; but additional directional contacts on the master controller could be arranged so that the safety circuit would be tripped if a contactor closed in the opposite direction from that selected owing to a fault.

48 Excessive power unexpectedly developed by a winding engine when at creep or shaft examination speeds Should excessive torque be applied to a winding engine by a winding engineman, or owing to malfunction, after receipt of a signal to move a conveyance slowly, there can be danger to persons working in the shaft. It is however considered undesirable to introduce circuits that prevent a winding engineman from selecting maximum available torque when persons are working in a shaft.

49 Instability in a closed-loop system System instability in closed-loop winding engines could occur owing to loss of stabilisation or a feedback signal. Such a loss could cause oscillations of torque and speed, the frequency and amplitude of which can vary over a wide range. Circuits can be devised to detect system instability but their design would need to allow for manoeuvring, etc. It appears practicable to design a protective system to respond to current oscillations of the order of 20% of full load torque if they persist over a period of about four seconds. Greater amplitudes of oscillations should trip the winding engine in a shorter time. A typical scheme would feed a signal proportional to motor current (ie to torque) into a filter circuit which would allow a frequency bandwidth of about 1 to 15 Hz to pass. The ripple content of this signal would then be measured over an integrating period and compared with a pre-set signal which, if exceeded, would trip the winding engine. It is considered that filter circuits to respond to oscillations of torque and speed in winding engines having closed-loop control should be examined.

50 A winding engine stationary, the brake lever not in the full on position, the safety circuit energised and the pumps or compressors supplying pressure to the mechanical brake started In these circumstances starting the pumps or compressors could apply pressure to the brake engine which would release the mechanical brake, and the winding engine would then be free to move under the influence of gravity. Changes to existing circuits to prevent this would be minor.




51 A conveyance moves when the control system is changed from one mode to another such as from manual to semi-automatic To prevent this, it is essential that movement of the mode selector should cancel all previous control instructions.

52 Recommendations:

(1) New designs of winding engines should incorporate the following features: - ‘anti-freeze’ protection to the stator contractor of each AC open-loop winding engine;

- protection against an electrical fault which could close the main contactor of an AC open-loop winding engine with the winding engineman’s lever in the off position;

- arrangement of control circuits of each AC closed-loop winding engine to prevent application of excessive power while the mechanical brake is holding the drum stationary;

- protection against excessive current in the main DC loop of each DC winding engine; and

- trip of the safety circuit if a fault causes power to be applied to the motor to move a winding engine in the opposite direction from that selected.

(2) New designs of winding engine and existing winding engines should incorporate the following features:

- prevention of brake system pumps or compressors from being started when the brake lever is not in the full on position; and

- a circuit to ensure that mode selection cancels all previous control instructions where control mode selection is provided such as from manual to semi-automatic.

(3) Existing winding engines be examined and consideration given to incorporating the features listed under recommendation 52(1).

Electrical winding engine drums and drives

53 Most winding engine drums in the past were constructed with cast iron or cast steel sides, and mild steel barrel plates bolted on to ledges or sills cast integrally with the drum sides. In the transition to fabricated construction, the design of drums including those for friction winding engines remained very much the same: this resulted in constructions that were too rigid and consequently in fatigue cracking in welds and stiffening members during service. Friction winding engine drums are particularly liable to these effects as they are subject to greater fatigue loading than other types of winding engine drum. Remedial action, often taken after advice from the Welding Institute*, usually involved cutting to relieve stress in the construction and the replacement of fillet welds by full penetration welds. Modern fabricated drums usually have a greater degree of flexibility, are predominantly designed by the finite element method of analysis, are without internal bridge pieces, and weld preparation is carefully controlled for full penetration welds. Drums with a degree of flexibility, to these designs, have proved successful in service.

* The Welding Institute, Abington Hall, Cambridge, England




54 Winding engines with clutched drums usually have clutches of the axially sliding, continuous tooth type, hydraulically or pneumatically operated in both directions and interlocked with the mechanical brakes. These arrangements have proved to be reliable in service.

55 Aspects of the design and construction of brake paths which are an integral part of a winding engine drum are referred to in paragraph 19 of Part 1A and sections 6 to 8 of Part 1B.

56 Drum shafts of electric winding engines have proved satisfactory. DC directly coupled motors with overhung armatures are being increasingly used and designs tend to result in shafts of larger diameter to reduce drum deflections and stress levels.

57 Traditional white metal sleeve bearings continue to be successfully used with oil ring and/or flood lubrication. Where normal lubrication is dependent on a power supply, special arrangements are made to provide adequate lubrication during a power failure and during gravity winding in emergency. It is important to avoid loss of lubricant through bearing seals as this can result in contamination of brake paths. Precise alignment of bearings during installation and thereafter is important, and is usually achieved by dowelling and/or fitting blocks between bearings and stops on the bedplate or soleplate which are in turn secured to the tower structure or winding engine foundations. This form of location and anchorage has proved adequate.

58 Winding engine reduction gears are generally single reduction double helical wheels meshed with pinions forged solidly on their shafts. Up to the late 1960’s gear wheels in general use had rims of rolled steel plate welded to fabricated centres; but inherent inclusions contained in the rolled steel plates have led to premature fatigue cracking of teeth in a number of installations. As a consequence, some forged rims have been used but the majority of recent installations have incorporated cast steel wheels. This has improved the situation but there have still been some failures, predominantly due to high residual stresses induced during the casting process and extensive corrective welding found necessary during manufacture. Fatigue cracking has also been experienced in the teeth of wheels in gearboxes, use of which is normally confined to friction winding engines. Pitting along the flanks of teeth has occurred for a variety of reasons but has not resulted in complete failure at a British coal mine. From experience gained to date the NCB has revised its specification for winding engine gears and this specifies the steel, permits forged and cast steel rims and requires non-destructive testing to an agreed standard at various stages of manufacture. The revised specification recommends the use of hobbed gears in preference to planed gears and suggests in some cases shaving teeth as a final process where severe pitting problems have been experienced.

59 There have been some gearbox shaft failures, mainly due to severe raising of stress by sharp radii at section changes or in keyways. The design guide described in paragraphs 8 to 13 has information on most types of shaft to enable existing or proposed designs to be checked.

60 Resilient couplings are used on geared winding engines to connect AC or DC motors to pinion shafts; well proved designs of coupling are in common use. When DC motors are directly coupled to drum shafts, half couplings forged solidly with the shafts are generally used.

61 A survey was carried out within the NCB of failures of winding engine motors and their associated major electrical apparatus, ie motor-generator sets, rectifier tank, liquid controllers etc. There is no evidence that failure of a winding engine motor or associated major electrical apparatus has resulted in immediate danger to




men riding in a conveyance or resulted in excessive retardation. Flashovers and fires have occurred on motor-generator sets and winding engine motors, and these incidents emphasise the need for regular cleaning and maintenance of ventilation ducts in machines, machine windings, pits and surrounding areas to prevent extensive damage. Some maintenance aspects are in Part 2B, section 24.

62 Conclusion:

It is considered that a failure of a component, referred to in this subsection, in the drum or main drive of an electric winding engine or its associated major electrical apparatus, would not result in danger to persons riding in a conveyance.

Steam winding engines and auxiliaries

63 Many of the statements in this report in respect of electric winding engines are equally applicable to steam winding engines. The major differences relate to the power unit, the limitations in applying reverse power following an emergency trip and the method of applying torque during a statutory brake holding test. These are referred to in paragraphs 10 and 126(5) of Part 1A. The reciprocating motion of a steam engine contributes also to wear and fatigue in many components and a high standard of maintenance is required.

64 The presence of water in valve chests and cylinders of a reciprocating steam engine can be detrimental to its operation; and water in excess, whether condensate or carried over from the boilers, has caused failure of cylinder covers and fracture of engine beds. Accumulation of condensate may be limited by correct pipeline configuration, careful warming up of the main engine, adequate condensate trapping, and provision of cylinder drains and relief valves. Carry over from boilers may be avoided by use of suitable water treatment, maintenance of correct boiler water levels, and sufficient steam to meet peak demand.

65 In the past, many steam winding engines were equipped with weight applied brakes released by steam pressure; often steam was used to assist brake application and thus a proportion of braking effort depended on the availability of adequate steam pressure. Most steam winding engines operating in Great Britain are now fitted with modern brake systems independent of steam.

66 Conclusion:

It is considered that a failure of a component in the drum or main drive of a steam winding engine or its associated steam auxiliaries would not result in danger to persons riding in a conveyance.

67 Recommendations:

(1) Winding engine mechanical brakes applied wholly or partially by steam or air pressure be replaced unless they are automatically backed up by a means independent of such pressure.

(2) Provision be made to minimize the possibility of carry over of water from boilers to steam winding engine valve chests and cylinders; and also to minimize accumulation of condensate in these components.

Friction between rope and drum

68 Force for controlling conveyances of a friction winding installation is transmitted to the winding rope(s) from the winding sheave or drum by friction. To maintain




integrity of drive during the most severe conditions such as an application of the emergency brake, friction winding engines should be designed and operated so that force to be transmitted is not sufficient to cause the winding rope(s) to slip on the friction treads. Regulations in Great Britain require this, based on the assumption that the coefficient of friction between the winding rope(s) and the friction treads is 0.2 or such other value as may be agreed (see appendix 32.5 in Part 2B).

69 At the design stage, calculations are made to establish maximum permissible accelerations and retardations for all loading conditions based on this coefficient of friction assuming a non-elastic winding rope system; and the maximum emergency braking torque is determined. When an emergency brake is applied, however, reactions are produced in the winding ropes and the elasticity of the ropes induces vertical oscillations of the conveyances. In consequence, the forces transmitted to the sheave or drum from the winding rope(s) vary so that the retardation of the winding system oscillates about an average value. The actual coefficient of friction between the rope(s) and the friction treads should have a value sufficient to accommodate these varying forces without slip. The merits of various types of tread and tread materials are discussed in Part 2B, section 7.

Assessment of reliability of systems

70 In Part 1A, paragraphs 51 and 52, reference is made to the commissioning by the NCB of a pilot reliability analysis of a modern winding engine, by an organisation experienced in such work. This study has led to a much simplified procedure which is intended for application by engineers with a minimum of special training. An account of it is in Part 2B, section 8.

Emergency winding apparatus

Permanently installed equipment

71 Regulation 4(1) of the Mines (Emergency Egress) Regulations 1973 requires the owner of every mine to ensure that there is at all times in force a scheme providing for the provision and maintenance of apparatus for affording to persons employed below ground in the mine means of egress in an emergency. The purpose of the scheme is to ensure that such apparatus is constantly available for use in an emergency in the event of permanently installed winding apparatus’ failing to function. Every such scheme is required to specify:

(1) the apparatus to be provided:

(2) the nature and frequency of examinations and tests to ensure proper maintenance of the apparatus, and the manner in which results of examinations and tests are to be recorded; and

(3) the training and practices in the use of such apparatus, the manner in which these are to be carried out and the time to be allotted to them.

72 To comply with these regulations, at every mine where there is no underground connection to a walkable outlet, apparatus ancillary to the permanent winding engine should be available at one or more selected shafts for use in the event of any failure, for example a general loss of power which would prevent all the winding engines at the mine from functioning. Moreover, at every shaft in Great Britain where men are wound, mechanically or manually operated equipment is provided to enable a conveyance which is immobilised in the shaft following failure of the power supply to be moved to a convenient landing.




73 At selected shafts, the ancillary apparatus usually includes mine cars or purpose designed water containers which can readily be filled at the surface and emptied at the shaft bottom, to provide weight for winding by gravity to enable all persons to be brought out from below ground.

74 At shafts there are usually provided:

(1) an auxiliary generator for providing power to enable the winding engine brakes and safety circuit and, where applicable, the auxiliary drive to be operated;

(2) an auxiliary drive, either mechanically or manually operated to enable the winding drum or sheave to be turned so as to enable men in a conveyance which is immobilised in the shaft by a power supply failure to be wound to a convenient landing; and

(3) manipulating facilities to enable shaft side equipment to be operated or made inoperative as necessary.

Mobile equipment

75 There is no statutory requirement in Great Britain which specifically refers to the provision of emergency mobile winding engines or to their routine maintenance when not in use.

76 In addition to permanently installed ancillary apparatus, the NCB keeps immediately available vehicle mounted mobile winding engines with self contained power units, for use in the circumstances such as shaft accidents where the permanently installed winding engines cannot be used. These mobile winding engines are kept at central locations within reasonable distances from all coal mines and, when used, require special concrete pads or hardstanding, anchorages and other equipment such as special headframe pulleys. Such items are permanently installed at all shafts owned by the National Coal Board where men can be wound.

3 Headframe and shaft equipment

Design principles for arrestors in friction winding installations

77 In Part 1A, paragraphs 53 and 67, reference is made to arresting devices which are installed in friction winding installations to arrest a conveyance or counterweight in case of an overwind. The regulations for friction winding engines (see Part 2B, appendix 32.5, paragraph 6) require that apparatus be provided in the headframe and below the lowest landing to bring an overwound conveyance or counterweight to rest without danger.

78 Friction winding engines operating in Great Britain were designed with clear space above and below the conveyances at the man landing positions at the ends of the wind. The space is generally not less than 3 + 2/3 V ft (1 + 2/3 V m) where V is normal maximum man winding speed in ft/sec (m/sec) or 15 ft (4.5 m) whichever is the greater, the normal maximum man winding speed being approximately 45 ft/sec (14 m/sec). The 15 ft (4.5 m) minimum clear space also applies to the mineral/materials landing position when this is beyond the man landing position. Approximately one half of the length of the clear space is occupied by the arresting devices; and for the purpose of arrestor design it is assumed that power is removed from the winding engine motor when an overwind occurs and that there is no mechanical or electrical braking available. The design aim was to retard the




conveyance in the arrestors at an average rate of 1 g, with the sump arrestor generally positioned so that it comes into operation about 3 ft (1 m) in advance of the headframe arrestor. Fig 1 shows a graphical representation of the basis of this design. The stopping position of a conveyance relative to the bumping beams is shown for various entry speeds into the arrestors, the entry speeds being shown as a percentage of the normal maximum man winding speed. The effects of reductions to 0.8 g and 0.6 g in average retardation imposed by the arresting devices are also illustrated.

Figure 1 Positions of bumping beams and arrestors

79 the basis for positioning bumping beams in a headframe relative to those in the sump, has varied as follows:

(1) In earlier installations bumping beams in headframes and sumps were generally so installed that either they came into operation simultaneously or the sump bumping beams came into operation in advance of the headframe bumping beams. Positioning of the sump bumping beams and arrestors to come into operation in advance of those in the headframe was based on the concept that tension of the descending rope(s) would thereby be sufficiently reduced to cause the rope(s) to slip on the friction treads and largely remove the effect of the inertia of the rotating masses.

0

5

10

15

20

25

30

35

Designed max. man winding speed ‘V’ ft/sec

Cle

ar s

pace

in h

ead

fram

e 3’

+ 2 /

3 ‘V’

or 1

5’ m

inim

um

50%

Ove

rwin

d cl

eara

nce

Arrestors

50%

Arre

stor

s

Feet

abo

ve h

ighe

st p

oint

for m

anrid

ing

0 10 20 30 40 45

40%

at 1g

or 36

% at

0.8g

or 31

% at

0.6g

50%

at 1g

or 45

% at

0.8g

or 39

% at

0.6g

60%

at 1g

or 5

4% at

0.8g

or 4

6% at

0.6g

Stop

ping

poi

nt a

t ent

ry sp

eed

of 7

0% a

t 1g

or 6

3% a

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54%

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.6g

Bumpin

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ams




(2) In later installations, while retaining the advanced position of sump arrestors, sump bumping beams have been more frequently positioned lower in the sump relative to those in the headframe, to take advantage of the energy absorbing properties of winding ropes when stretching after an ascending conveyance has struck the headframe bumping beams. This does not apply to the position of bumping beams for a descending counterweight which should be in advance of those in the headframe.

There are advantages and disadvantages in the two systems but on balance it is considered that the second method in paragraph 79(2), should be adopted for future installations.

80 Following rope changing or capping operations, the relative positions of the conveyance and/or counterweight to the arrestors should be maintained within the original design parameters.

81 Recommendations:

(1) The existing design principles for arrestors should continue to be used.

(2) For all future friction winding installations with two cages or skips, sump bumping beams be so located that they be struck after those in the headframe and thus allow elasticity of the winding rope(s) to assist retardation of the descending conveyance; but sump arrestors should continue to act in advance of headframe arrestors.

(3) For all future counterweight installations, bumping beams for a descending counterweight should be in advance of those in the headframe, to relieve the ascending conveyance of the energy of the descending counterweight.

Pit bottom buffers

82 Paragraphs 53 to 60 of Part 1A describe tests on a prototype installation of pit bottom buffers and recommend further development of buffers so that they could be installed in pit bottoms of all drum winding installations. Three trial sets of fabric reinforced rubber buffers similar to those illustrated in fig 8 of Part 1A were installed: each of the three shafts is used for transport of men and materials and it is necessary for the cage rails to be registered within practical limits for loading and unloading.

83 Design was initially based on the parameters and desirable features stated in paragraphs 54 and 55 of Part 1A: these include a maximum average rate of retardation of 1 g and a peak rate of 2.5 g. The requirements have been reviewed on the basis of medical and other practical information available, and it was apparent that there could be some relaxation but the precise degree has not been established. During tests on the trial sets, designed to limit peak retardation to 2.5 g, acceptable average rates of retardation were achieved although these were sometimes greater than 1 g, and rebound characteristics were also acceptable. New equipment has been developed to measure rates of retardation of conveyances and this is referred to in Part 2B, section 9. Based on these investigations, revised design parameters have been established as follows:

(1) Buffers should be designed with the maximum man load descending and an empty conveyance ascending; and for an impact speed of not less than 5 ft/sec (1.6 m/sec) or the speed resulting from an overspeed trip with the emergency mechanical brake force reduced by 50%, whichever is the greater. The reduction of 50% is assumed to take account of effects of contamination




and consideration of an installation in detail may revise it where failure of one component would leave a mechanical brake force greater than 50%).

(2) Buffers should be designed so that the maximum rate of retardation does not exceed 2.5 g except that any part of a peak exceeding 2.5 g for less than 0.04 sec should be ignored.

84 Characteristics of various retarding devices have been examined with a view to designing practical forms to suit requirements of decking equipment. Examinations showed that retarding devices could be split into two categories:

- recoverable types, which regain their original shape after being operated; and

- non-recoverable types, which remain permanently deformed after being operated.

At a pit bottom during normal operations, conveyances may have to be accurately registered for loading but this may be unnecessary where changes in rope length due to loading can be accommodated. Where buffers are used for registration, a recoverable type will normally be required because landing speeds and loads during mineral winding may induce forces large enough to deform non-recoverable types permanently. Where buffers are not required to register conveyances but serve only to arrest an overwound conveyance, either type may be used.

85 Mechanics of arrest Effects of changes in winding rope tension and extension are considerable when a conveyance is being retarded by buffers and allowances for them may have to be made; technical considerations are discussed in Part 2B, section 10. Predictions so far are sufficiently accurate not to delay installations of reinforced rubbers buffers and performance curves which take account of the rope effect are shown in fig 2. Computerized studies of the problem are continuing and will be correlated with experimental investigations which are to be made using a specially constructed test rig as described in Part 2B, section 10.

86 Conclusions:

(1) The design parameters referred to in paragraph 83 are satisfactory for adoption.

(2) Rubber type recoverable buffers already tested at mines have proved to be operationally satisfactory and have been adopted for suitable applications. Information on selection is available and can be obtained from the manufacturers. Longer term aspects of ageing, fatigue etc. will have to continue to be monitored.

(3) A number of alternative types of recoverable and non-recoverable buffers are becoming available and can, subject to satisfactory development, be adapted to comply with the design parameters.

Conveyance suspension gear

87 The Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960 contain provisions for conveyance suspension gear relating to materials, heat treatment, factor of safety and frequency of examinations. Changes to these regulations made in recent years permit the use of approved steels in the quenched and tempered conditions without periodic heat treatment. In parallel with these changes to the regulations, a definitive life of 20 years has been introduced which is subject to review in the light of experience. The NCB has




established testing centres and adopted a procedure, including magnetic particle inspection, for examination of components of conveyance suspension gear when new and after intervals in service for six or 12 months. The procedure gives guidance for the identification, acceptance or rejection of imperfections and states limits for wear of pins and holes.

88 Materials such as wrought iron and mild steel are not prohibited by the regulations but their use is conditional on periodic heat treatment. These materials were superseded by 1.5% manganese steel in the normalised condition, and in recent years by 1.5% manganese steel in the quenched and tempered condition or by nickel chromium molybdenum steels, all to British Standard 2772 Part 2 1956, which was revised in 1977 to reflect these changes and to take into account latest metallurgical developments.

89 Strict controls are employed in the manufacture of conveyance suspension gear to ensure that only specified materials and correct heat treatment are used. Welding of components has virtually been eliminated except for chain links which are produced by modern manufacturing techniques and subjected to non-destructive testing.

90 Recent practice has generally been to base design of conveyance suspension gear on a minimum static factor of safety of 10:1 which is required by the regulations for approved steels; and there is little doubt that this has been a major contributory factor to the good safety record of conveyance suspension gear. Account is nevertheless now being taken of modern design techniques including design for infinite fatigue life. Screwed components in tension in conveyance suspension gear should be avoided in new installations and, in others, have a static

10

5

2g

1g

Inches

Retardation

Inches

ft/se

cTo

ns

Cage speed ft/sec

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

5

10

15

20

Inches

Buffer deflection

Time milli-secs

Winding depth (ft) 1015Rope dia. (ins) 15/8

E for rope (ton/in2) 5000Weight (tons)Cage 4.25Men 3.75Material 5.25

Rope stretch (ins)Cage 5Cage + men 9.4Cage + material 11.2

Buffer resistance

Reduction in rope load

0 1

80 17 26 4535 55 7066 90 104 119 136 155 177 206

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Figure 2 Predicted performance curves for a recoverable buffer




factor of safety not less than 15:1. A committee comprising representatives of the NCB, SMRE* and NPL† is considering rationalisation of conveyance suspension gear: the aim is to produce a design code which will be complementary to the NCB documents Cage suspension gear – general engineering requirement and Procedure for examining cage suspension gear at testing centres.

91 Conclusion:

In view of improvements made in recent years with regard to materials, periodic examinations including non-destructive testing, the introduction of a definitive life, and the work done by the committee referred to in paragraph 90, the position in respect of conveyance suspension gear is considered to be satisfactory.

Conveyances for manriding

92 The Mines and Quarries Act 1954 requires that all parts and working gear of all machinery and apparatus, being part of the equipment of a mine, shall be of good construction, suitable material, adequate strength and free from patent defect. The Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960 also regulate the construction of cages and ancillary apparatus.

93 Design and construction of conveyances have evolved over the years and advantage has been taken of experience and modern technology in developing equipment now in service. Although the traditional method of riveted construction is still favoured by many engineers, use of welding, proprietary high tensile fasteners and fitted bolts with suitable locknuts in construction of conveyances, has augmented options available to designers. Metallurgical developments have contributed towards the selection of materials with improved fatigue resistance and notch ductility, while retaining compatibility with the method of construction.

94 Guide shoes or rollers are purposely designed with adequate strength and wear properties to suit their shaft guides and flared shoes or fitments are added to engage receiver guides. Conveyances have to be balanced to reduce wear of guides, and cages are normally symmetrical in suspension and layout; but suspension gear attached to skips may be off centre to equalise displacement from the vertical when a skip is loaded and unloaded, or to suit site conditions.

95 Conveyances for friction winding installations are designed to withstand forces imposed by retarding devices and bumping beams. Conveyances for drum winding installations have generally been designed for landing on solid members; but the effect of the introduction of pit bottom buffers needs to be considered. Friction winding and many drum winding installations in Great Britain have catches in the headframe to limit the fall back of an overwound conveyance. It is recommended in Part 1A, paragraph 68, that catches be provided for all drum winding installations, so conveyances have to be designed to withstand fall back.

96 Conveyances are constructed to prevent limbs of riders from inadvertently projecting outside, but where persons such as the first man in or the last man out have to operate shaft side gate or signalling equipment, provision is needed in a conveyance and shaft structure for this to be safely carried out from inside the conveyance. Conveyance gates are usually removable or hinged for stowing. Lift up mesh gates are preferred on conveyances as gates hinging inwards are inconvenient except for stowing away, and gates projecting outside a conveyance are not allowed by regulation. Removable gate support structures should be

* Safety in Mines Research Establishment, Health and Safety Executive † National Physical Laboratory




adequately secured in position before persons are permitted to enter, except those whose duty it is to make a conveyance ready for winding. Persons require adequate headroom and regulations specify the provision of rigid, easily reached, hand rails. Alternative means of egress should be provided in conveyances where the usual exits would be seriously obstructed following an overwind.

97 Devices used to retain vehicles in conveyances, and other fittings, are designed for the minimum obstruction to persons travelling, or are covered by a portable floor, and should be lockable where necessary to prevent hazard. Lifting facilities for handling materials may be required in a conveyance. Intermediate decks which pivot to accommodate long materials, and man decks in skips which are raised during coal winding, should have stops at their extreme positions with locks where necessary; and means should be provided for operating decks and locks from a safe place.

98 Counterweights do not normally carry persons but they form part of a man winding installation and relevant similar considerations apply to their design. Where weights are carried in a frame, it should be constructed so that they cannot be displaces during winding.

99 Suitable provision may be necessary where persons ride on the outside of cages, skips or counterweights for shaft and guide examinations, maintenance and repairs.

100 Conclusion:

The features and principals described above are in general use in the design and construction of conveyances and have promoted a good record of safety.

Winding ropes

101 Regulations in Great Britain require that winding ropes on drum winding engines have a minimum factor of safety of 6.5 when new, and limit use of these ropes to three and one half years. Regulations for friction winding engines include a formula for determining the minimum factor of safety of ropes and limit their use to two years.

102 All friction winding engines in the NCB with the exception of three, and over 70% of drum winding engines, are fitted with locked coil winding ropes. Many stranded winding ropes have been replaced by locked coil, and new installations are generally fitted with locked coil ropes. The NCB specification for locked coil winding ropes is often used as a basis for supply to overseas users, and forms the basis of an International Standards Organisation (ISO) specification which is in course of preparation. Ropes are manufactured to approved processes and quality control procedures, with wire to British Standard specifications (for example BS 2763:1968 for round wire) except for shaped wires.

103 The construction and suitability of a winding rope selected for a particular duty is generally agreed after consultation between customer and manufacturer bearing in mind statutory safety factors, fatigue and the ratio of drum or pulley diameter to rope diameter, so that operational stresses are kept within safe limits. Specifications include provision for the use of galvanised wire to protect against corrosion. Investigations into improved forms of surface protection should continue to be pursued.

104 In recent years there has been a move towards the use of higher tensile wire in ropes where shaft loads have been increased but this practice should be approached with caution and kept under close review. A relaxation from the statutory minimum rope safety factor in deep shafts could usefully be considered as an alternative.




105 In Great Britain, multi-layer coiling of ropes is generally limited to two layers, except for emergency winding engines and some sinking winding engines. Ropes attached to a winding engine drum are usually both of the same lay. With multi-rope friction winding installations where rope guides are in use, it is usual practice to have half the winding ropes of one lay and half of the opposite lay to balance the effect of twist on conveyances. With rigid guides this not considered necessary. Multi-rope winding installations operate with winding ropes directly connected to conveyances through suspension gear and not through any form of compensating gear.

106 There are two NCB specifications for winding ropes. These are:

- No 186/1970 ‘Locked coil winding ropes’, and - No 176/1968 ‘Stranded wire ropes for winding’; this is based on BS 236:1968 ‘Stranded wire ropes for mine hoisting (winding) purposes.’

The Ropeman’s Handbook published by the NCB, written in collaboration with the SMRE which is being revised, is a standard for the construction, installation and maintenance of ropes.

107 Conclusion:

Control procedures exercised in the manufacture and use of winding ropes are of a high order and have resulted in a high standard of safety over many years.

Rope and rigid guides

108 Regulations in Great Britain require that guides be provided in shafts deeper than 150 ft (45 m). Shaft guides are formed from either tensioned ropes, or rigid vertical sections of steel or timber. Of the 570 shafts used for carrying persons in Great Britain, 393 have rope guides, and 177 are equipped with rigid guides of which 113 are steel and 64 timber.

109 The method adopted for guiding a conveyance depends on many factors including the winding capacity, type of conveyance, shaft dimensions and alignment. A rope guide system provides a smoother passage for conveyances and a reduction in dynamic loading in comparison with a rigid guide system owing to irregularities usually present in the latter. A further advantage of rope guides is a reduction in resistance to the flow of ventilating air; they are also simpler to install and usually easier to maintain as they do not require supporting structures in the shaft.

110 Advantages of rigid guides include the possibility of smaller clearances, a reduction in the loading of headframes, less complex arrangements below the lowest entrance to a shaft and prevention of twisting of conveyances. At insets, rigid side guides simplify receiving equipment, rigid end guides can be arranged to prevent cars from leaving a conveyance during its wind and retractable devices are available to permit decking.

Rope guides

111 Regulations do not impose a minimum factor of safety or a life for guide ropes but the NCB requires a new rope to have a minimum factor of safety of five. The NCB also limits rope life to 20 years but a rope may be replaced earlier depending on its condition. There is a NCB specification for guide ropes. This is No 388/1970 ‘Half-locked coil guide ropes’. Some 6/1 round rod rope guides are still in use but




these are gradually being replaced by guides of half-lock construction. Round rod rope guides are manufactured from low tensile strength steels so they are restricted to relatively shallow shafts. Half-locked coil guide ropes are manufactured from wires of higher tensile strength steel and are suitable for use in deeper shafts. It is essential that outer wires are large to avoid frequent replacement on account of wear, and preferable that all wires are rust resistant.

112 Designs developed over the years have taken account of advancing technology, modern materials and experience; this has been incorporated in the NCB reference document entitled ‘Recommended shaft guide practice’. Further information is available in the Ropeman’s Handbook.

113 Design of a guide rope system should take into consideration factors such as the inherent twisting effect of the winding rope, clearances between conveyances and between conveyances and shaft wall, the shape of conveyances and effects of ventilation particularly at shaft insets and at the conveyances passing points. The aim for all systems should be to minimise vibratory forces and oscillations of conveyances. Two basic guide rope arrangements are used, one having guides positioned at each corner of a conveyance and the other having all guides positioned along the side of the conveyance adjacent to the shaft wall although there are variations. Both arrangements are successfully used; but some authorities are of the opinion that smoother running is obtained with four guides along the side of a conveyance, particularly if it is long and narrow in plan. If twisting of a conveyance is a problem, however, a guide at each corner may be preferable.

114 It is essential that rope guides are accurately spaced in the headframe and in the shaft bottom. They are normally suspended by means of white metalled sockets or wedge clamps; if the latter are used, it is practice for the wedges to be supplemented by bolted clamps. Both types of attachment are usually mounted on spherical seatings to accommodate small errors of alignment and to provide facilities for rotating guides to distribute surface wear. In headframes, attachments should be mounted above the supporting structure in order to permit good accessibility for lifting, rotating and recapping of guide ropes.

115 Where guide rope pass between baulks, beams or platforms below the lowest entrance into a shaft or through an air casing in a headframe, provision should be made to prevent localised wear of the ropes. This can be achieved by clamping a split sleeve tightly to the rope so that wear occurs between the outside of the sleeve and the fixture in which it is free to move. The sleeve should be made from a fire resistant material and packed with a corrosion inhibiting material.

116 Sufficient tension should be applied to guide ropes to promote stability of conveyances during winding, and by applying different tensions to each rope in a guide system, synchronous vibrations can be substantially reduced. It is preferred that guide ropes are tensioned by weights, suspended below the lowest entrance into a shaft, because they provide constant tension independent of ambient temperature. Where sump clearances are insufficient for weights, spring tensioners are an alternative although they are not recommended for permanent installations. Spring tensioners are generally provided with indicating devices which should be regularly checked and tension adjusted when necessary. If this is not done, guides may lengthen in hot weather and become too slack, and in cold weather may contract and impose excessive loads on the headframe. Rods for carrying weights may be suspended from guide ropes by glands or clamps, below which an extra length of rope should be available for maintenance. The NCB specifies a maximum life of 20 years and a minimum factor of safety of 10.for weight rods; and where these rods have screwed threads in tension, a minimum factor of safety not less than 15 for threaded portions. When new tension weights are installed, spacer




bosses on the top surface of each weight should be considered as a means of accommodating any build up of corrosion between them. They should also be encased in suitable water repellent, rust preventive materials. Adequate access to tension weights and headframe attachments is necessary for examination and maintenance purposes.

117 The sliding connection between conveyances and guide ropes is usually made by split bushings secured to the upper and lower structural members of conveyances. Cast iron bushes are normally used but, if wear on guide ropes or over heating is a problem, brass or phosphor bronze bushes may be used.

118 Where clearances between conveyances are limited it may be necessary to install rubbing ropes to supplement the guide system. In such cases, it is necessary for conveyances to be fitted with suitably shaped contact plates that are usually attached to the upper and lower structural members. Equipment associated with shaft guides, such as conveyance receivers, is referred to in paragraph 139.

Rigid guides

119 There is a NCB specification No P.117/1955 ‘Flat bottom rails for shaft guides’ which lists preferred rail sections.

120 rigid guides may be formed from standard flat bottom rail sections, rolled steel channels or other structural steel sections; but where conditions are corrosive timber guides may have advantages. Timber guides are usually made of pitch pine, jarrah or karri. In one installation laminated guides made from iroko are used. The NCB document ‘Recommended shaft guide practice’ is being extended to include a section on rigid guides.

121 A rigid guide system is normally fixed to buntons which are securely attached to the shaft side. The vertical spacing between buntons is based on guide strength and horizontal forces due to conveyances. These forces may be increased by vibration at various conveyance speeds and this should be taken into consideration when determining spacing. It is also necessary in the design of buntons to give consideration to reducing corrosion by elimination of pockets where water can collect, and to reducing resistance to the flow of ventilating air.

122 In order to provide maximum rigidity in guide systems, Joints between rails, channels or timbers should be located at buntons by suitably designed brackets. In many installations, however, joints between guides do not occur at buntons and in such cases special connections should be designed to ensure rigidity. Clamp type connections are preferred to bolted connections where flat bottom rails are used, owing to stress concentrations produced by bolt holes. Flame cutting of steel guides, particularly flat bottom rail sections, should be avoided because it may lead to the possibility of fatigue cracking in service owing to material embrittlement. Cleats or brackets should not be welded to flat bottom rails because the high carbon content of rails may lead to embrittlement. Guides should be carefully aligned and rigidly attached to buntons. Joints between rigid guides should not induce excessive side thrust from conveyances; there are advantages in using dowels in the ends of guides for the purposes of alignment particularly where joints do not coincide with buntons. Each length of guide should be individually supported and the design take into account changes in length due to temperature variation. Excessive ramming thrusts that may occur during conveyance loading should not be transmitted to guides; and design should take account of wear and corrosion which may progressively reduce the size of guides. In one timber guide installation, socket headed cap bolts in circular counterbored holes were found to cause less cracking of timber than square headed bolts in square recesses.




123 Contact between conveyance and rigid guides is made by means of shoes or rollers. Vibratory forces which may develop between conveyance and rigid guides are diminished when rollers are mounted on spring loaded assemblies. Where conditions permit, there are advantages in using rollers with replaceable plastic treads to reduce wear on guides. It is essential to ensure that guide roller assemblies cannot interfere with arresting gear, particularly of friction winding systems, or with receivers and other structure located at the top or bottom of a shaft. Interlocking of retractable sections of rigid guides is referred to in paragraph 152.

124 Conclusion:

Standards of safety incorporated in design and installation of shaft guides are of a high order and maintenance is generally satisfactory. The NCB document ‘Recommended shaft guide practice’ has proved satisfactory over many years as a basis for design, installation and maintenance of rope guides.

Balance ropes

125 In Great Britain, regulations for friction winding engines stipulate in respect of balance ropes:

(1) a maximum life of three years;

(2) prohibition of spliced ropes;

(3) prohibition of the subsequent use of a balance rope as a winding rope; and

(4) a breaking strength not less than six times the weight of the rope.

126 there is however no specific requirement in the Mines and Quarries Act 1954, nor in regulations, in respect of balance ropes used with drum winding engines. There is also no British Standard or National Coal Board specification for balance ropes or their end fixings but details of constructions are in manufacturers’ literature.

127 The following factors contribute to balance rope problems:

(1) inherent forces in balance ropes tending to twist their loops;

(2) broken wire or strands fouling the sump structure and causing the balance rope loop to lift;

(3) transmission of abnormal oscillatory forces from the winding system to the balance rope causing it to foul the sump structure;

(4) fall of material or mineral, or its accumulation in the sump, causing the balance rope to be diverted or arrested;

(5) excessive localised wear in balance rope guide timbers resulting in grooving which restricts free travel and sideways movement of the rope;

(6) twin balance rope loops coming together and becoming entangled;

(7) seizure of a normally free swivel; and

(8) rope corrosion.




128 The majority of balance ropes are of round construction, mainly of the multi-strand non-rotating type. There are still some flat ropes in service but it is desirable that they be phased out where practicable because of their inferior resistance to corrosion compared with round ropes.

129 Conclusion:

The weight and flexibility of balance ropes are purposely designed to meet requirements of specific shafts and therefore a full standard specification is impracticable.

130 Recommendation:

The following be adopted for balance ropes on drum winding engines:

- a minimum breaking strength when first installed of six times the maximum static load which the rope will carry in service; and - a working life determined by the condition of the rope as revealed by examination but not exceeding five years from when first put into use.

Control of balance rope loops

131 Balance ropes suspended beneath two conveyances, and hanging freely in a shaft, form loops in the shaft sump which usually need to be controlled by dividing timbers, boxes, or similar means. Satisfactory balance rope operation requires selection of a rope construction sufficiently flexible to form a loop between conveyance centres with only a limited degree of twist. Minor variations in manufacturing can cause ropes of identical construction to behave differently in service and new ropes are not completely free of twist. Rope swivels are usually fitted to each end of round balance ropes to prevent formation of kinks, or figures of eight, by twisting forces in the ropes during installation and during normal running. In a number of installations, these rope swivels are either locked or removed after an initial running in period. Loop control systems are not uniform but have evolved to suit conditions and rope behaviour at particular shafts. There are some installations running with little loop control and others which are more closely controlled over a considerable distance. The types of system can be divided into four main categories as shown in Part 2B, section 11. There are some winding systems where the balance rope loop travels up the shaft, such as clutched drum installations, where the control systems are not applicable.

132 Recommendation:

The design principles for balance rope loop control detailed in paragraph 3 of section 11 in Part 2B be adopted where applicable for all new and existing installations.

Monitoring of balance rope loops

133 Balance rope incidents arise from many causes, which may culminate in lifting of the loop out of its control system and result in severe damage to the rope or shaft furnishings etc. Monitoring systems are at present designed to detect significant lifting of a loop above its normal highest running position, and to give audible and visual warning to the winding engineman and the onsetter; some trip the winding engine safety circuit. In addition to monitoring lift of a loop, and in view of the danger of build up of water or spillage beneath a loop, it may be considered advisable to monitor that a minimum clear space exists below the loop when suitable equipment is available.




134 Consideration has been given to various loop monitoring devices such as Pease probes, stretched wires, proximity switches, and photo-electric infra red or sonic beams. The protective system should preferably not require the installation of a power source in the shaft sump, and a survey has shown that switches operated by stretched wire or lever are the most simple and effective devices. In most circumstances a single monitoring device situated centrally through the loop would best detect loop lift (see Part 2B, section 12). The exact setting would depend on the normal highest loop position but the device should be set to operate at the earliest practical moment. A position between 3 ft and 5 ft (1 m and 1.5 m) above the bottom of the loop should be satisfactory and this may be determined by observation or test. The device should trip the safety circuit to stop the winding engine.

135 A monitoring device placed through a loop should be so designed as to avoid damaging the rope and should be so placed and guarded as far as possible to prevent spurious tripping from falling debris. The device should be designed to fail to safety. A loop should always be examined after its monitoring device has tripped.

136 Ready means of access to protective systems, and adequate lighting, should be provided to facilitate maintenance.

137 Recommendation:

(1) Loop monitoring devices be installed where applicable with balance ropes, and such devices be of a type which fails to safety.

(2) Operation of a balance rope loop monitoring device be arranged to trip the winding engine safety circuit and to give indication to both the winding engineman and onsetter.

Termination of wire ropes

138 Winding, guide and round balance ropes are normally terminated or capped with white metalled sockets or wedge type capels. There are BS 643: 1970 and NCB specification No 483/1970 for white capping metal; and a NCB specification No 465/1965 ‘Sockets for use with white metal cappings’. Capping procedures are detailed in the Ropeman’s Handbook. These provisions are considered to be satisfactory.

Shaft side equipment

139 In amplification of paragraphs 69 to 73, 83 and 84 of Part 1A, shaft side equipment and operational aspects which have been considered for shaft top, shaft bottom and intermediate insets, include keps, platforms, shaft gates and doors, decking equipment, skip loading and discharge equipment, conveyance catch release gear, conveyance receivers, retractable centralising gear, retractable chutes, protective canopies, fencing, landings, means of access, and methods of operation of equipment by and from a conveyance, associated proving and interlocking gear, and facilities for emergency egress.

140 Interlocking of shaft side equipment when men are automatically wound is not included; this subject is referred to in paragraphs 225 to 231.

141 After consideration of causes and effects of shaft incidents, general principles relating to man winding have been formulated with safety as the primary objective. Design of equipment should incorporate the requirements outlined in the following paragraphs.




142 Keps Subject to the revision of regulations referred to in paragraph 73(1) of Part 1A, the system should be such that where keps need to be retained for purposes other than man winding, they cannot obstruct the passage of the cages when men are wound.

143 Platforms Decking platforms used in conjunction with manriding should satisfy the following requirements:

(1) When power and manually operated platforms are in the fully raised or retracted position, there should be adequate clearances between them and the conveyance under all normal conditions of operation.

(2) Power and manually operated platforms should be interlocked with conveyance in-line gear and securely locked, so that the platforms cannot be lowered during manriding unless the deck of a conveyance is aligned within the designed range.

(3) Power and manually operated platforms should be proved in their clear and operating positions. When a platform has been proved down, movement of the conveyance off the in-line gear (eg due to excessive rope stretch during loading) should not cause the platform to lift. Downward travel of power and manually operated hinged platforms should be limited by stops.

(4) Power operated platforms should be so designed that they remain in one or other of their clear or operating positions should power be lost in those positions.

(5) Power operated platforms should have interlocking arrangements which prove the platforms are down or extended, when men are about to enter or leave a conveyance, before the shaft gates can be opened.

(6) Power operated hinged platforms should have tilting toes designed to allow a descending conveyance to pass between platforms without being arrested when the platforms are down. This feature is intended to allow for inadvertent passage of a conveyance between platforms rather than for normal use.

(7) In shafts with rope guides, where platforms are used at intermediate insets, means should be provided to align and limit horizontal movement of a conveyance when men are entering or leaving it.

(8) Side fencing to a minimum height of 3 ft 6 in (1 m) should be fitted to platforms where no other fencing is provided.

144 Shaft gates and doors The mines and Quarries Act 1954 requires shafts to be equipped with enclosures or barriers. Shaft gates should additionally be to the requirements of Clause 10 of BS 5304: 1975 ‘ Code of practice for safeguarding of machinery’ and the NCB draft Codes and Rules ‘Minimum standard of fencing and guarding’. They should also satisfy the following requirements:

(1) Where mine cars, tubs or trams are used, shaft gates and their supporting structures should be of adequate strength to prevent a vehicle from entering a shaft should it collide with the gates during decking operations.

(2) Spring applied safety bolts or catches should be fitted to keep open power operated guillotine type gates or doors while men pass through. These safety bolts or catches should operate automatically and their action be proved where appropriate.




(3) To prevent unauthorised access to shafts, gates should be close to the floor and either a minimum of 6 ft 6 in (2 m) high, or to the height of the roof where this is less than 6 ft 6 in (2 m) high.

(4) In the event of power failure or loss of fluid pressure, power operated gates should remain open or closed. This should not preclude completion of an operation which has already started when failure occurs. When men are being wound, movement of gates should be initiated manually and interlocked with conveyance in-line gear to prevent their opening when a conveyance is not in line.

(5) During manriding, shaft gates and doors at all levels should be proved to be closed before movement of a conveyance can commence.

(6) Where an assistant onsetter or assistant banksman is on duty to safeguard persons entering or leaving a conveyance who are not visible to the onsetter or banksman, he should have facilities to prevent movement of shaft gates at his position.

145 Decking and loading equipment This should satisfy the following requirements:

(1) Control apparatus on power operated decking equipment should be interlocked so that, when the automatic contrivance of a winding engine is set for manriding, all items of decking equipment not required for that operation are rendered inoperative. This applies also to control equipment for loading or unloading skips.

(2) It should not be possible to illuminate any men indicators unless all decking plant associated with a particular installation is in the manriding mode.

(3) Where there are facilities for rail mounted mine vehicles to approach a shaft side, retractable stops of adequate strength should be provided to prevent vehicles from reaching the shaft during manriding.

(4) Where two sets of stops are employed in each rail track at the ingoing side of a conveyance (as may be needed with power operated rams) all stops should be raised or otherwise made effective when the automatic contrivance of a winding engine is set for manriding.

(5) Catches should be provided in the tracks on the running off side of conveyances to ensure that vehicles do not gravitate backwards or rebound and foul shaft gates.

(6) Decking plant control systems should be so designed that movement of the setting of the automatic contrivance of a winding engine from man to coal, and vice versa, does not cause shaft gates to operate.

(7) Where facilities additional to normal decking equipment are required for handling vehicles, these facilities should be designed for the purpose and not improvised.

(8) Indication should be given to the appropriate operators when any gate or shaft interlock is overridden by the means provided.

(9) Facilities should be provided for immobilising all decking plant.

146 Power operated conveyance catch release gear The following requirements




should apply:

(1) Conveyance main catch release gear should be interlocked to prevent its operation during manriding.

(2) Where inadvertent operation of conveyance secondary retention gear could cause injury to men it should also be interlocked to prevent operation during manriding.

147 Conveyance receivers These should satisfy the following requirements:

(1) Receivers should be provided at a shaft top and where necessary at a shaft bottom where rope guides are used. Either rigid guides or receivers should extend to the maximum overwind position. All receivers should be designed with an adequate lead-in to aid smooth entry of conveyance.

(2) To stabilize the conveyances as they arrive at an inset, retractable receivers, centralisers and guides at insets should be interlocked so that they operate before platforms.

148 Fencing and protective canopies The statutory requirements and other standards referred to in paragraph 144 apply to this equipment. Fencing and protective canopies should also comply with the following:

(1) To prevent unauthorised access to shafts, side fencing at all landings should be close to the floor and either a minimum of 6 ft 6 in (2 m) high, or to the height of the roof where this is less than 6 ft 6 in (2 m) high.

(2) Fencing above shaft gates at underground landings should be full roadway height and width where practicable. Where fencing would restrict handling of materials, removable or hinged panels may be provided and should include means for preventing unauthorised opening.

(3) Where necessary, canopies should be provided at all shaft landings except the surface, to protect men entering or leaving a conveyance against falling objects. If canopies are of the retractable type, as may be required at insets, they should be interlocked so that they can only protrude into a shaft when a conveyance is in the correct position.

(4) Where canopies are provided, fencing should extend to their undersides. Walkways across shafts should be totally covered overhead and fencing should extend to this cover.

149 Landings Means should be provided where necessary at landings for orderly marshalling and controlling the passage of men to and from the conveyance.

150 Access Where men are about to enter or leave a conveyance, access should not be obstructed by vehicles which should be firmly held by a stop. Any vehicle on the running-off side should be beyond the catches referred to in paragraph 145(5).

151 Operation of shaft side equipment from a conveyance Where it is necessary for men to be wound to or from an unmanned landing, provision should be made for operating any shaft gate or platform required from a position of safety within the conveyance.

152 Safeguards against collision with intermediate inset equipment During normal




manriding in shafts with intermediate insets, the winding engine CATEGROY 1 safety circuit (referred to in paragraph 46 of Part 1A) should be tripped to immobilize the winding engine, in the event of any of the following conditions pertaining when the mechanical brake is not fully applied:

(1) Inset retractable landings and/or receivers are not proved to be at their extreme positions of operation and are not proved to be in phase with the setting of the winding engine automatic contrivance.

(2) Inset platforms are not in fully raised or retracted position.

(3) inset conveyance centralisers are not withdrawn.

(4) Inset retractable guides of the rigid type are not proved to be correctly positioned and secure.

(5) Inset retractable canopies are not proved clear or in a safe position.

(6) Any other retractable equipment at insets which can protrude into the shaft is not proved clear or in a safe position.

153 Interlocking and winding engine brake lock In addition to the recommendations in paragraphs 84(2) to 84(4) of Part 1A, all shaft side doors forming part of an airlock with a conveyance and providing regular access for men, mineral or materials, should be interlocked with the winding engine brake locking device during normal manriding so that the winding engine brake cannot be released unless the doors are closed.

154 Facilities for emergency egress At those shafts equipped to comply with the Mines (Emergency Egress) Regulations 1973, facilities should be available for manipulating shaft side equipment, including gates and platforms so that manriding can proceed in the event of power failure.

155 Conclusion:

The safety of new winding systems would be enhanced by adoption of the design principles detailed in this sub-section; and the safety of existing installations would be improved by incorporating these principles where practicable.

156 Recommendations in addition to paragraphs 73 and 84 of Part 1A:

(1) Shaft side equipment and associated vehicle handling apparatus should be designed and interlocked where necessary so that, when the automatic contrivance of a winding engine is set for manriding, all items of decking equipment not required for that operation are rendered inoperative, to prevent their inadvertent movement from causing injury to persons entering or leaving a conveyance.

(2) Where normal operation of shaft side equipment at an intermediate inset causes apparatus to protrude into the path of a conveyance, the equipment be designed and interlocked so that movement from its fully retracted or safe position when the conveyance is not in line will cause the winding engine safety circuit to be tripped and the brake to be automatically applied.




Shaft signalling systems

Existing systems

157 In part 1A, paragraphs 85 to 90, attention is drawn to disadvantages of some existing shaft signalling systems in Great Britain. Existing multi-relay type systems having an illuminated display unit in the winding engine house are further considered here, and in section 13 of Part 2B, together with other relevant matters. Features which could usefully be examined with a view to amelioration are:

(1) In most installations there is no check that the signal despatched corresponds with that received.

(2) In many installations there is no protection against earth faults or short circuits which could result in incorrect signals.

(3) Emergency stop systems are not infallible.

(4) In most cases a single key is used for initiating all signals and correct visual and audible indication of the intended signal is dependent upon the manner and speed of rapping.

(5) Correct visual indication of the signal one to distinguish between raise when stopped and stop when in motion, is dependent upon the operation of a mechanically driven cancellor which is relatively insensitive at very slow engine speeds.

(6) In most cases the relays associated with the raise and lower signals are used in other signalling combination. This could lead to spurious indication or raise and lower signals.

(7) In many cases, there is insufficient provision for co-ordinating the shaft signal system with other protective features such as the winding engine men/coal selector, winding engine brakes and keps.

(8) On many installations the winding engineman and banksman are not warned if signals are incomplete.

(9) Facilities for first man in and last man out which may be inadequate.

(10) Inadequate signalling arrangements for assistant banksmen and assistant onsetters.

(11) In some cases shaftside equipment is interlocked with shaft signals which could lead to interruption of a sequence of signals and incorrect indication to the winding engineman.

158 Recommendation:

In addition to the recommendations in paragraph 90 of Part 1A, all existing shaft signalling systems be examined with a view to incorporating the following features where these can be included without major modification:

- earth fault monitoring devices to give warning only, unless systems already possess adequate protection against earth faults that could cause false or incorrect signals;




- reliable emergency stop circuits and components;

- cancelling devices driven from the winding engine which are capable of positively distinguishing between stationary and creep speed conditions;

- automatic restoration of the incomplete signal protection by operation of the cancellor on completion of the wind, where first man in facilities involve the use of a special onsetter riding signal (say 9) to override incomplete signal protection;

- provision for interfaces between shaft signalling systems and other winding equipment, for example, brakes, men/coal selectors and kep interlocks;

- visual indicators to show emergency stop and keps clear, in addition to those showing the position of the men/coal selector, brakes on and brakes locked on, the indicators being positioned to be readily seen by persons about to enter or leave a conveyance;

- suitable standby power supplies;

- visual indication of signals at all signalling stations;

- environmental protection of apparatus and signalling push buttons or keys designed to prevent accidental operation.

Future systems

159 In addition to the recommendations in paragraph 158, new designs of systems should take account of the following:

(1) In order to check that a signal despatched is the same as that received at the engine house, the audible signal should be monitored and transmitted back to the signalling station. If the signals are the same, they should be audibly and visually displayed to the winding engineman, banksman and onsetter. Any discrepancy or false signal should cause an error signal to be so displayed (allowing corrective action to be taken).

(2) The efficiency of signalling is improved by using a different push button for each signal, plus an independent stop button, as consistently timed audible signals can be achieved. Signals transmitted from rapper type keys are subject to the dexterity of the operator and the rate of initiating pulses. The buttons should be of a shrouded type to prevent accidental operation. In addition, inclusion of a separate stop signal button with separate circuitry minimises the risk of errors arising from use of a common signal key for the stop and raise signals. Systems should furthermore be so designed that signals cannot be stored. Accidental or deliberate operation of two signal buttons together should only initiate the first signal transmitted or should alternatively indicate an error signal.

(3) The possibility of spurious operation of raise and lower signals would be considerably reduced by use of time division multiplex coding or adoption of a two out of three majority vote relay arrangement, as referred to in paragraph 21 of section 21 of Part 1B.

(4) Signalling systems which are certificated as intrinsically safe should be available for use where required particularly in upcast shafts at gassy mines.




(5) The number of visual indicators and audible warnings required at each signalling station has increased to meet various recommendations, particularly where modern decking plants are in use. Miniature indicators should be provided on the various signalling panels to display each signal and other necessary information but, in addition, certain information should be generally displayed to persons about to enter or leave a conveyance: eg men/coal selector position, brakes on, brakes locked on, emergency stop (at the winding engine house and initiating level only) and keps clear.

(6) It is likely that existing shaft signalling systems would be improved more speedily by incorporating the various features detailed if all the additional information associated with shaft signalling could be handled by existing shaft cables. It appears that this could readily be achieved by use of time division multiplexing techniques which also have the inherent advantages that their coding and addressing features improve system integrity.

(7) Although use of signal recording devices may have little effect on safety of shaft signalling systems, such devices could help to identify faulty operation and to prevent a recurrence. Modern recorders have the facility to produce on demand an accurate record of a selected period of operation without the need for continuous chart recording.

160 Recommendations:

For future systems, in addition to paragraph 90 of Part 1A and paragraph 158 of Part 2A:

(1) When a signal selected is the same as that received, visual and audible indication of the signal be displayed to the winding engineman, banksman and onsetters; otherwise, an error signal be so displayed.

(2) A visual indicator and a discrete push button or key be provided for each signal; and, where possible, the frequency of audible tones be unique to a particular landing.

(3) The signal one to stop be distinguished from the signal one to raise: a separate signal key and indicator is usually necessary to achieve this.

(4) Relays used for raise and lower signals be not utilised in other combinations of signals.

(5) Signalling systems which are certified as intrinsically safe be available for use where required particularly in upcast shafts at gassy mines.

Headframe pulleys

161 Two main types of headframe pulley are in service: cast and fabricated. Service experience has shown that most cases of deterioration have resulted from high residual stresses, excessive wear and loose spokes; and that few have been directly attributable to material deficiencies.

162 Cast iron pulleys have been made of material to Grade 14 of BS 1452 with mild steel spokes. The National Coal Board’s Specification No 358 ‘Spoke ends for cast headgear pulleys’ which recommends tinning of spoke ends, may be amended to allow their coating instead with a micaceous mineral suspended in an organic solvent. This would reduce carbon migration and hence possible embrittlement of spokes.




163 Fabricated pulleys are normally manufactured from steel to Grade 43A of BS 4360: 1972 and welded to a central boss of cast steel to Grade A1 of BS 3100: 1976 (previously Grade A of BS 592). In some pulleys, bosses may be forged. All welding is normally carried out to BS 5135: 1974 and the fabrications are stress relieved before machining.

164 Materials used appear to be adequate but evidence of high residual stresses in pulleys indicates that cast and fabricated pulleys should be stress relieved during manufacture. It may also be possible to reduce the consequences of wear by use of replaceable tread sections made from suitable materials.

165 Since the introduction by the NCB in 1959 of Specification No 185 for the design and manufacture of headframe pulley shafts, there has not been any failure of a shaft made to those standards. This would suggest that the 0.3% carbon steel specified is satisfactory. The specification is being revised but only because of changes in the steel making process.

4 Maintenance, testing and training

166 This section includes maintenance principles and practices for equipment in winding installations. More detailed considerations of practices and techniques are in Part 2B. Items not specifically referred to in this section are in sections 19 to 25 of Part 2B.

Statutory reporting

167 Relevant statutory report books are completed as a routine at mines in Great Britain to record the results of examinations and tests required by the Mines and Quarries Act 1954 and regulations made thereunder. These include reports of examinations and tests made on winding equipment which are complementary to reports required by the procedures and documentation referred to at paragraphs 105 to 107 of Part 1A. The procedures to programme and control recording, signing and custody of all such books are being reviewed.

Planned activities related to mining environment

168 Administrative procedures and documentation have been proposed for planning of and reporting on checks on a mine environment, primarily associated with safety and ventilation, by persons other than mine engineering staffs. Some of these activities, for example checking fire fighting equipment and procedures, may be relevant to the safety of persons working at or in shafts.

Maintenance procedures and documentation

169 Section 30 of Part 1B describes administrative procedures common to many managers’ schemes for the mine within the NCB and proposes modifications to raise the standard of reporting and simplify the task of scrutinising reports.

170 Examinations and tests including those specified in regulations, of electrical and mechanical apparatus, are scheduled in each manager’s scheme for the mine; and appropriate reports are required in writing on the work instruction and report documents of that scheme. A number of examinations and tests specified in regulations have to be reported in statutory books and those relating to winding installations are listed in Part 2B, section 14. Statutory books, managers’ schemes for the mine and owner’s instructions such as NCB Codes and Rules date from different times and sometimes require duplicated reporting. It is considered that the




situation should be reviewed to avoid duplication, to improve standards of reporting and to ensure adequate subsequent action.

171 To ensure that routine examinations and tests are being thoroughly carried out and that proper conclusions are being drawn from craftsmen’s observations and reports, formal inspections by supervisory staffs should also be made as routine and reported on.

172 the present day operational pattern of intensive mining, multi-shift production and concentration of winding operations, increases maintenance required at shafts and limits time available for it to be done. It is important that adequate time be scheduled for examinations, tests and maintenance to be carried out thoroughly and effectively. Detailed planning of shaft use is necessary if major routine work, repairs or replacement of equipment are to be effectively carried out.

173 When planning examinations and maintenance, it is advisable to identify any hazards that may arise and to establish safe methods of working which include essential precautions and safety rules. Some aspects to be considered in this context are in Part 2B, section 15. When preparing a plan for major work it is essential to detail main points of procedure and incorporate safety precautions and relevant reference to safety rules. Where inadvertent operation of equipment would endanger maintenance personnel, the equipment should be immobilised as far as reasonably practicable.

174 Protective clothing and safety harness are important parts of the equipment of maintenance personnel working in shafts and headframes. Clothing should provide adequate protection but at the same time allow safety harness to be worn without unreasonable restriction of movement. Safety rules should require that safety harness be worn and used in shafts and in other circumstances where there is danger from falling, and that harness be adequately maintained as outlined in Part 2B, section 15.

175 Where automatic fire extinguishing equipment is installed in winding engine houses there is a possible hazard to maintenance or other personnel if the equipment operates whilst they are within the protected area or if they enter an area in which such equipment has recently operated. This hazard is greatest in basement rooms where heavier than air fire extinguishing media are most likely to settle. Where necessary, there should be consideration of procedures to allow safe access to such areas; an example is detailed in BS 5405: 1976 ‘Code of practice for the maintenance of electrical switchgear for voltages up to and including 145 kV’.


(1) Statutory books for reporting on examinations and tests required by the Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960, and corresponding reporting requirements of managers’ schemes for the mine, be reviewed to avoid `duplication, to improve standards of reporting and to ensure adequate subsequent action.

(2) Managers’ schemes for the mine should incorporate supervisory checks of headframe and shaft equipment to ensure that routine examinations and tests are being thoroughly carried out.

(3) Use of shaft winding equipment be reviewed to ensure that adequate time is scheduled for examinations, tests and maintenance.

(4) When planning examinations and maintenance, any hazards be identified and safe working methods and procedures established.




Maintenance of foundations, buildings, structures and shaft linings

177 Legislation in Great Britain requires foundations for machinery and apparatus used as, or forming part of, the equipment of a mine to be properly maintained, and all buildings and structures on the surface of a mine to be kept in safe condition. Legislation also requires that all parts in use of a shaft shall be kept secure; and that at every mine a competent person appointed for the purpose by the manager shall, at intervals not exceeding seven days, examine thoroughly the state of every part of any shaft through any part of which persons are carried, and forthwith make and sign in a book provided for the purpose by the owner of the mine a full and accurate report of the result of the examination. The mechanical engineer at a British mine has by tradition the responsibility of ensuring that shaft linings are maintained in a safe and secure condition; this position should be specifically recognised in legislation.

178 In the Coal and Other Mines (Mechanics and Electricians) Regulations 1965, a scheme of systematic examination and testing of mechanical and electrical apparatus is required but it does not extend to foundations, buildings, structures and shaft linings; to ensure proper control of their maintenance when such items are associated with winding installations, they should be included in a similar scheme. Suitable procedures for reporting on examinations carried out by mine engineering staff are described in section 30 of Part 1B but, in the case of reports on shafts, they should be supplemented by use of a form of report similar to that illustrated in fig 16.1 of Part 2B. On this a master record is first produced, in the form of a diagrammatic development of the shaft lining, showing location of the main features. Defects or other matters to be reported can then be marked on photocopies to provide a pictorial record which can be easily understood. A completed form could also be used as part of an engineer’s shaft examination report.

179 Check lists supplemented by notes of guidance (see section 16 of Part 2B) constitute an appropriate means of instructing persons in the nature of examinations to be carried out. Shafts should be examined weekly by trained shaftsmen. Foundations, buildings and structures should be examined at appropriate intervals by person who have been given any special training and instruction required. Additional examinations should also be periodically made by mine mechanical engineers with the help of civil engineers.


(1) The mine manager have a scheme for the examination of foundations, buildings and structures associated with winding installations and for the examination of shaft linings; and this scheme be similar to that required for mechanical and electrical apparatus.

(2) Reports of shaft examinations be made on a form similar to that illustrated in fig 16.1 of Part 2B.

(3) Consideration be given to clarifying legislation in Great Britain in respect of the mine mechanical engineer’s traditional responsibility for the maintenance of shaft linings.

Maintenance of equipment in towers, headframes and sumps

181 Maintenance of winding apparatus and ancillary equipment mounted in winding engine towers, headframes and shaft sumps presents particular problems. Although most installations have some basic similarities, they vary in detail and are




exposed to different environments; maintenance should therefore be planned, organised and varied to suit each installation. Standards, methods and frequencies of maintenance operations in Great Britain are such as not to give rise to major maintenance problems; but utilization of resources could be improved if the principles of maintenance planning outlined in paragraphs 169 to 176 of this Part were more widely applied. Section 17 of Part 2B also refers.

182 Open towers and headframes are often exposed to the effects of severe weather, particularly ice and driven snow. Some also pose problems of accessibility to equipment. At many upcast shafts, the tower or headframe forms part of the airlock enclosure of the mine ventilation system within which condensation and hostile atmospheric conditions may accelerate corrosion of steelwork and deterioration of concrete and brickwork. Provision of adequate lighting and access to parts requiring maintenance may also be difficult. Where ice and driven snow could adversely affect clearances between conveyances and receiver guides or the operation of tower and headframe equipment, consideration should be given to providing suitable protection.

183 Detaching plates or bells Regulation 19(8) of The Coal and Other Mines (Shafts, Outlets and Road) Regulations 1960 states ‘Where the efficient operation of any such detaching hook would be affected by wear of any ancillary plate or bell provision shall be so made for the measurement of the relevant dimensions by means of calipers or gauges at intervals not exceeding thirty days.’ Such frequent measurement is now thought to be unnecessary and consideration should be given to replacing Regulation 19(8) by a requirement that, whenever a detaching hook is taken off and replaced by another, the dimensions of the replacement hook and the detaching plate or bell be measured to check their compatibility.

184 Pit bottom buffers for drum winding installations At present the development testing of pit bottom buffers of the type described in paragraph 56 of Part 1A suggests that they will need little maintenance. On some pilot installations this aspect is being evaluated but those in service should be regularly checked to ensure that they can operate as intended.

Maintenance of ropes in winding installations

185 All ropes in winding installations used for carrying persons through a shaft, staple pit or unwalkable outlet are required by regulation in Great Britain to be thoroughly examined at intervals not exceeding 24 hours. A considerable amount of information is generally available for guidance in the care and maintenance of wire ropes. Detailed descriptions of techniques and procedures emphasise the importance of careful storage and handling, regular cleaning and lubrication, systematic examinations and the need for maintaining correctly profiled rope grooves in pulleys, sheaves and drums. Mine engineering staffs and rope maintenance personnel are therefore usually well informed about factors which can adversely affect the condition of ropes and about methods whereby they can be effectively examined and maintained. The Ropeman’s Handbook referred to in paragraph 106 deals with selection, installation, examination, care and lubrication of various types of rope used for mining work, common forms of deterioration and damage likely to be experienced, and the various types of capping and end fixing. It is a basic training and reference manual for personnel concerned with care and maintenance of ropes.

186 Ropes in mine shafts in Great Britain are often subject to corrosion, which may lead to the onset of corrosion fatigue. However, extensive use of galvanised wires, the properties of present day lubricants, improved designs of winding systems in new and reconstructed mines, and provisions made for examination and testing of




ropes in service largely contain this problem. Standards of examination, testing and lubrication during manufacture and service should nevertheless be maintained if dangerous deterioration of winding, balance, guide and rubbing ropes is to be prevented. The only statutory examination for shaft ropes, other than the 24 hourly examination, is that prescribed for winding ropes at intervals not exceeding 30 days and which is referred to in Part 2B, section 18. To ensure that the surface condition of balance, guide and rubbing ropes is satisfactory, and that wear has not become excessive, periodic examinations of these ropes should also be carried out.

187 The quality of lubricants has been greatly improved over the years by manufactures in co-operation with rope makers and users. This improvement may be expected to continue in future leading to better performance and methods of application. Mechanical application of lubricant to winding ropes is extending and could also be more widely employed for lubricating guide ropes. Some details of maintenance of ropes in winding installations are in Part 2B, section 18.

188 Recommendation:

Each manager’s scheme for the mine should require that at suitable intervals every balance, guide and rubbing rope be thoroughly cleaned and examined at all places liable to deterioration, and at other selected places throughout its length.

Lasers and other devices for aligning shaft equipment

189 The traditional method of aligning shaft equipment such as buntons and rigid guides is to fix tensioned wires parallel to the desired lines and measure offsets. Lasers are being increasingly used in place of tensioned wires to facilitate more rapid alignment of equipment and also to measure movement of shaft linings. This is described in Part 2B, section 26. Where accurate vertical measurements are required, steel measuring tapes are generally used but electronic distance measuring instruments have been successfully employed for this purpose.

190 Lasers are extensively used for underground surveying and the NCB has issued Codes & Rules for their specification, design, approval and use, to reduce hazards to personnel. Lasers which comply with the Codes & Rules have proved satisfactory in shafts of up to 500 m depth, but higher powered apparatus has been found necessary for greater depths to minimize divergence of their beams. There are procedures for exempting apparatus which does not meet the specification.

Protection of steelwork from corrosion

191 In normal atmospheres steelwork will always suffer some deterioration. The rate of corrosion may be reduced by suitable treatment, but its progress should be monitored to ensure that every structural member retains an adequate reserve of strength. British Standard 5493: 1977 ‘Code of practice for protective coating of iron and steel structures against corrosion’ provides detailed guidance on methods of protective treatment and could well be consulted before any such work is specified or undertaken. Treatment may range from single coat painting to galvanising; and it may even be necessary to replace mild steel by special corrosion resistant steels. Further reference to this subject is in Part 2B, section 27.

Shaft air heating

192 The presence of water freely running down shaft walls in periods of cold weather may lead to formation of ice which can be dangerous to persons riding in shafts. Ice may build up to obstruct passage of conveyances or may come loose and fall down a shaft particularly during a quick thaw. Precautions should therefore




be taken to prevent significant formation of ice preferably by minimising any flow of water into a shaft and, if this proves insufficient, by heating shaft air. Further reference to this subject is in Part 2B, section 28.

Non-destructive testing of components of winding apparatus

193 In Part 1A there is reference to non-destructive testing (NDT) of winding engines, and detailed proposals are included in section 5 of Part 1B for routine examination of mechanical brake parts. ‘Guidelines to suggested action following NDT’ are in appendix 5.4 of Part 1B. Extensive NDT of existing brake components has since been carried out on winding engines in Great Britain and some of the suggested actions and component classifications have consequently been reassessed.

194 Paragraph 112 of Part 1A refers to the need for using NDT to ensure satisfactory quality of certain winding engine components prior to service. Existing practices for NDT of drum shafts, intermediate shafts, main reduction gears, crank pins and crosshead pins are not deemed to require urgent modification, but it was nevertheless considered that they should be reviewed in relation to recent developments. Some details of NDT procedures are in Part 2B, section 29.

195 A survey has been made of shaft and winding apparatus not covered in Part 1 and consideration has been given to the need for routine NDT of these items and to methods to be employed when necessary. A review of existing practices for testing drum shafts, intermediate and main reduction gears has also been carried out.

Reassessment of non-destructive testing

196 Paragraphs 113 to 118 of Part 1A refer to NDT of winding engine mechanical brake components and classify components from consideration of the significance of failure. On the basis of this classification and the duty of an installation, recommended intervals between non-destructive tests of winding engine brake components are proposed. The extensive experience gained in the NDT of mechanical brakes of more than 500 winding engines has led to the following reassessment.

197 No change is required to component classification (A) in paragraph 114 of Part 1A, namely single line components, but it is considered that component classification (B) and (C) should be changed to relate more closely to the philosophy of 50% braking referred to in paragraph 3 of Part 1A. Thus the new classifications (B) and (C) would be:

(B) those mechanical brake components the failure of which would result in either insufficient braking torque to bring the winding system safely to rest or the loss of more than 50% of braking,

(C) those mechanical brake components the failure of which would not prevent the brake from bringing the winding system safely to rest and would not result in loss of more than 50% of braking.

It should be noted that this revision modifies the example of classification of components on a typical winding engine brake shown in appendix 5.1 of Part 1B.

198 The frequency of NDT of winding engine brake gear is related in Part 1A to the duty of the installation, whether heavy, medium or light, which in turn is determined from the number of winds per year. Whilst this is reasonable it is considered that a better criterion is the number of brake applications. The three duties of heavy, medium and light should be retained but account should also be taken of other




factors, as well as number of winds, in determining a category for a particular installation as in paragraphs 202 and 203. Revised recommendations for the frequency of examination of mechanical brake gear which take account of experience gained and the above classifications are in table 2.

199 In paragraph 5(4), section 5, of Part 1B, it is stated that areas to be non-destructively tested should be given a thin coat of quick drying white background paint. While this is generally the case, it is not always necessary on finely machined surfaces.

200 Figs 5.3 and 5.4 in appendix 5.4 of Part 1B are regarded as obsolete. Consequently, entries under ‘nuts’ ‘pins’ and ‘clevises’ in that appendix should be replaced by the guidelines in Table 1.

While there is no reject criterion for bolts in Part 1, it has been found that British Standard commercial quality nuts and bolts are satisfactory provided they are properly checked and found free from imperfection which could impair service performance or safe working of a component. No attempt is made to define which imperfections would affect service performance or safe working as this is left to the judgement of the responsible engineer who should assess any imperfection taking into consideration its size, location and stressing.

201 In Part 1A, on the basis of the limited information then available, it is suggested that routine NDT of winding engine drums should be carried out in service at intervals of not more than ten years. Subsequent consideration and a review of past experience have cast doubt on the need for routine NDT to supplement visual inspection. Accordingly, it is proposed that NDT of winding engine drums should not be carried out on a routine basis but only when inspection has revealed a need for more detailed examination.

Table 1 Nuts, brake pins and clevisesComponent Observation Action

Nuts Any imperfection in threads Any longitudinal imperfection

Brake pins Transverse imperfections Any imperfection in thread and bearing area Imperfection at a section change

Reject if considered that the imperfections would affect service performance or safe working of component

Clevises Imperfection in threads Imperfection at a section change Imperfection within the hole area and within 50 mm from the hole

Frequency of non-destructive testing

202 In paragraph 116 of Part 1A, the frequency of NDT of winding engine mechanical brakes is related to the duty of an installation, whether heavy, medium or light, which in turn is determined from the number of winds per year. While this criterion is acceptable, it is considered that the frequency of examination of a mechanical brake would be better if based on the number of times it is applied, which is related to the number of decking operations at the end of each wind. Moreover, the fatigue lives of winding engine reduction gears and other




components may be influenced by factors such as depth of shaft, their diameters, number of teeth etc, and so number of winds is unacceptable as the sole criterion. Determination of frequency of examination should ideally be based on the number and magnitude of stress cycles to which a component is subjected. This information is not always readily available but it is possible to categorise components into heavy, medium and light duty on the basis of experience and existing knowledge of installations.

203 Thus it is recommended that the heavy, medium and light categories be retained, but that the number of winds should not be the sole criterion for determining a category. A competent person should assess operating experience and conditions for components in each particular installation and allocate a category. In the case of mechanical brakes, the following should be included in the assessment: age of components, number of winds, number of decking operations, brake forces and operating methods. In the case of pulleys, shafts and gears, the following should be considered: age of component, number of winds, diameter of pulley, depth of mine shaft, number of gear wheel revolutions per wind and component loading.

Table 2 Frequency of non-destructive testing of winding components

Maximum intervals between successive examination (years)

Duty of installation

Winding engine gears

Gear shafts

Headframe pulleys

Headframe pulley shafts

Drum Shafts Hangers and connecting ears for chain type suspension gear

Mechanical brake parts classification

Electric Steam A B C

Heavy 3 3 3 3 7 3 5 1 3 6

Medium 5 5 5 5 10 5 7 2 5 10

Light 7 7 7 7 14 7 10 5 10 10

204 All these components should be examined when new and at the frequencies in table 2. The maximum intervals between examinations that have been adopted are based on wide experience and some fracture mechanics work. Experience will continue to be gathered, and work on fracture mechanics expanded, to enable frequency to be reviewed to relate more closely to the design and actual working conditions of a specific component. In addition to examinations at the frequencies in the table, others should be made as appropriate:

- when inspection has revealed a need for more detailed examination,

- after any incident which could have caused abnormal loading,

- when experience indicates that due to usage the item may be approaching the end of its life.

205 Routine NDT of conveyance suspension gear is referred to in paragraph 87. Other items such as shaft side equipment, weight rods and rigid guides are not considered to require routine NDT but should be so examined when inspection has shown this to be necessary.

Fracture mechanics

206 Failure assessment by fracture mechanics is concerned with size and growth of flaws in materials subjected to stress. All materials contain flaws whether they be




microscopic inclusions and imperfections, or large notches and grooves introduced during manufacture. It is from such flaws that failure occurs, either suddenly by application of a single load or progressively by gradual growth owing to application of a large number of fatigue cycles. Safe life assessment can be made from a knowledge of four parameters: flaw size, localised stress at flaw, value of fracture toughness of the material and rate of fatigue crack propagation. The rate of growth of fatigue cracks can be directly related to the applied cyclic load and hence a frequency of inspection can be calculated to ensure that growing cracks are detected before final failure. It should be noted, however, that even though the fracture toughness of a material may be known, the complex nature of many components precludes an assessment of service stresses; and that this, combined with the difficulties in accurate location and sizing of flaws, already referred to, precludes general application of such techniques. An illustration of the application of this technique to a headframe pulley shaft is in Part 2B, section 30.

207 Recommendation:

(1) The revised classifications for components of winding engine mechanical brakes outlined in paragraph 197 be adopted; paragraph 114 of Part 1A be superseded and appendix 5.1 of Part 1B modified.

(2) Intervals between non-destructive tests of winding components be those specified in table 2; and recommendation 118(3) of Part 1A be superseded.

(3) The guidelines to suggested action following non-destructive testing, in appendix 5.4 of Part 1B, be modified by deleting figs 5.3 and 5.4 and replacing entries under ‘nuts’ ‘pins’ and ‘clevises’ by those in table 1.

(4) Non-destructive testing during manufacturer be specified for important components of winding apparatus.

Monitoring of mechanical equipment

208 The aim of monitoring is to detect abnormalities in mechanical equipment before failure or hazard arises, to prevent accidents and to permit remedial action to be taken before breakdown or emergency. Monitoring, in the broadest sense, includes visual inspection, non-destructive testing, overhaul, scheduled replacements, etc. Such practices are already well established in the mining industry. Paragraph 50 of Part 1A reads: ‘Safe operation of winding engines depends upon implementation of effective planned maintenance schemes, testing programmes, and training of personnel. These should include lubrication standards and non-destructive testing procedures for components when new and when in service.’ In paragraphs 112 to 117 of Part 1A, there are details of non-destructive testing; and recommendations for the frequency and scope of such testing are in paragraph 118 of the same Part. Based on experience, these details and recommendations have been modified and the changes are in paragraphs 196 to 201.

209 In recent years a wide range of compact and reliable transducers and circuitry has become available; these can be used to monitor continuously critical functions or components, to give early warning of faults or deterioration of performance, or to stop an operation automatically. Continuous monitoring while equipment is working reduces the need to interrupt production for non-destructive testing, dismantling, or overhaul. Cases are known in industry where dismantling has itself contributed to subsequent failure. The advantages must be weighed against factors associated with monitoring equipment: eg initial installation costs, reliability, maintenance, training etc, all of which require allocation of resources. Even though such equipment may fail safe, spurious signals can cause delay; and additional displays




or checking may add to the work of operators or test engineers. Use of these methods in industry is nevertheless increasing. A summary of methods generally available is in Part 2B, section 31, which highlights possible application to safety of manriding in shafts, and suggests criteria against which proposed devices can be assessed.

210 The reliability of a monitoring device in relation to the reliability of its primary system is important. No monitor operates perfectly all the time; most monitoring instruments have failure rates of between 0.1 and 10 faults per year. Even if the reliability of a monitor is less than that of the equipment it is designed to protect, the reliability of the total system can still benefit. The example in Part 2B, section 31, shows that, should a monitor be ten times less reliable than the equipment monitored, system reliability can improve five times.

Testing of friction winding engines

211 To comply with regulations in Great Britain, it is necessary to carry out a series of tests when a winding engine, which is ordinarily to be used for winding persons, is first installed, and thereafter at periods not exceeding three months for drum winding engines and six months for friction winding engines.

212 A model testing code for drum winding engines is in Part 1B. Reference is made to a model testing code for friction winding engines in paragraphs 122, 126(3) and 168 of Part 1A and this code is in Part 2B, section 32.

213 Recommendation:

The model testing code in section 32 of Part 2B for friction winding engines be adopted.

Brake performance test

214 In Part 1A, it is recommended in paragraphs 126(6) and 126(7) that a brake holding test for drum winding engines be carried out each shift to determine that contamination has not reduced braking performance below the level defined in paragraphs 126(4) and 126(5) for electric and steam winding engines respectively. For most electric drum winding engines, the test current would be either the maximum permitted by any current limit device in use or that corresponding to 1.1 times the maximum torque required for normal duties. The recommendation in paragraph 126(7) of Part 1A is that trials should continue, to establish if it is practicable to replace the existing brake holding tests for electric winding engines by one using a specified combination of mechanical brake torque and power torque, such that the drum just moves through the brake. The reason for this is that, where brakes can produce torque greatly in excess of the test torque, brake performance could diminish before being shown up by the existing type of test.

215 The braking philosophy outlined in Part 1A paragraph 3 requires that the design of new brakes should be such that, in the event of failure of a component, the brake still exerts a braking torque sufficient to bring the winding system safely to rest and produces not less than 50% of the normal braking force. A serious reduction in mechanical braking torque may also occur as a result of contamination of brake paths or linings by oil or moisture or other matter, but it has been assumed that this will not exceed the 50% allowance for loss of braking force due to failure of a component. Paragraphs 6 of Part 1A states that improved design standards, together with adequate standards of inspection, testing and maintenance, should reduce the possibility of component failure and the possibility of contamination of brake paths or linings; and that work is proceeding on the selection and




development of lining materials less susceptible to contamination. In addition, it is required in paragraph 10 section 29 of Part 1B that steps should be taken if necessary to prevent contamination of brake linings and paths or any other vital parts of the safety equipment by oil, grease, condensation or water. Drum pits should not be allowed to become so contaminated with grease as to prevent effective examination of brake anchor brackets and beams. If necessary, special provisions should be made to ensure adequate and safe access to equipment requiring examination and maintenance. Adequate lighting should be provided to enable examinations to be effectively carried out. Examinations of brake paths should be in the maintenance check lists which form part of the manager’s scheme for the mine as in paragraph 3, section 30 of Part 1B.

216 Trials took place to establish if it is practicable to replace the existing brake holding test (which indicates only that braking is greater than a minimum value) by a brake performance test to determine that braking has not deteriorated since the previous shift which can be carried out by a winding engineman alone. This would be achieved by establishing that the drum just moves through the brake when a pre-determined proportion of braking torque is compared with the corresponding proportion of power torque. The trials were carried out on five winding engines at regular intervals using the following two test methods. Method 1 was used on two winding engines, method 2 on another two and both methods on the fifth winding engine.

Method 1 With the drum at a known position and with empty cages, a pre-determined brake force indicated by the brake system pressure was applied. Power torque was then increased from zero until the drum just moved through the brake. At this point the motor current was noted.

Method 2 With the drum at a known position and with empty cages, the brake was fully applied. The motor current was adjusted to a pre-determined value and the brake then gradually released until the drum just moved. At this point the brake system pressure was noted.

The test results from both methods produced too wide a scatter and so the tests were discontinued.

217 Consideration was next given to a retardation test to replace the existing brake holding test, although it was appreciated that this would require permanent instrumentation on each winding engine. Necessary instrumentation could be provided as an additional feature on the prototype electronic supervisory devices, referred to in paragraph 34 to 37, which are now being installed. Records of statutory and other retardation tests indicated that this retardation test would have to be carried out at a minimum speed of approximately 20 ft/sec (6m/sec) to obtain consistent results for comparative purposes and with less scatter than the brake performance tests. The retardation type of test may be a good measure of brake performance, and may be pursued in the long term. However, as an alternative, the torque reaction device referred to in Part 1A paragraph 34 which is already in an advanced state of development, is being further developed with a view to obtaining a measurement of braking torque that could be used to give early warning to the winding engineman of onset of contamination of the brake paths.

218 Following examinations of alternative methods of performing a suitable brake test each shift, and after further detailed consideration of protection against contamination afforded by the existing brake holding test, it is considered that the existing brake holding test is the most suitable to be applied at the present time. This type of test should also be carried out each shift on friction winding engines but at a power torque based on the Model Code for the Testing of Friction Winding




Engines in Part 2B, section 32, and as defined in the following recommendation. The position should be reviewed in the light of continuing developments. Where winding engines have no manual brake lever they should be similarly tested but it may be necessary to provide means such as a push button to retain mechanical braking when power is applied.

219 Conclusion:

Use of the torque reaction device in future may form the basis of an alternative means of carrying out brake holding tests.


(1) The existing brake holding test continue to be applied each shift to drum winding engines, preferably before man winding.

(2) A brake holding test be also applied to friction winding engines but at torques as defined below, using empty conveyance(s):

- a power torque of twice maximum static torque in case of two conveyances, taking into account unequal weights of balance and winding ropes; or, where a motor will not develop twice maximum static torque, the maximum torque available to the winding engineman; or

- a power torque of 1.5 times maximum static torque in favour of the counterweight in a conveyance and counterweigh system.

Training for work in shafts

221 Regulations in Great Britain require the appointment of a competent person at every mine to examine thoroughly, at specified intervals, ‘the state of every part of any shaft, staple pit and unwalkable outlet through any part of which persons are carried’. Persons appointed for this purpose are skilled shaftsmen who have been trained in shaft examinations, under close supervision, and instructed in various aspects of shaft work.

222 Other craftsmen having particular skills are also involved in work in shafts but shaftsmen carry the main burden of installation, examination and maintenance therein. Shaftsmen are often recruited from craftsmen (eg blacksmiths and carpenters) and in such instances are able to carry out or supervise work involving their particular skill. The scope of their duties varies depending upon types of shaft furnishings and also to some degree on custom and practice at particular mines.

223 The extent and nature of training for shaftsmen in Great Britain has in the past been decided on a local basis but the National Coal Board has recently established basic training requirements which are to be generally applied. In addition to training in practical aspects of shaft work these requirements include supplementary instruction in the following subjects:

(1) safe working, including essential features of personal security such as use of safety harness and general safety procedures;

(2) operation and maintenance, including the purpose and function of shaft fittings, their examination and maintenance requirements;

(3) installation, including methods and arrangements for installation of ropes and cables in shafts; and




(4) mechanical handling, including procedures, communications equipment and principles of handling and moving heavy loads in shafts.

224 All persons required to work in shafts, whether shaftsmen or not, need to have an aptitude for this type of work and should be instructed in the essential features of personal safety. In general, shaftsmen should be competent to supervise other workers to ensure compliance with safety procedures in shafts.

5 Other winding practices

Control systems: push button winding

225 Paragraph 141 of Part 1A refers to investigation work being carried out to establish principles of operation and a code of practice for push button winding at existing and future installations.

226 A survey of winding installations operated by the NCB and at two German mines established the various forms of push button control necessary to suit the different types. A typical multi-level winding installation was analysed to determine the feasibility of the operational principles.

227 Conveyance and counterweight installations are most suitable for pushbutton operation and for winding in multi-level shafts controlled either from the conveyance or shaft side.

228 Installations with two conveyances are those most commonly operated by the NCB and 30% of this type work in multi-level shafts. The more straightforward form of push button control for this type of installation is from the shaft side, using a banksman and onsetter to initiate a wind and to supervise men entering or leaving conveyances. At normal manriding times where winding is taking place from two levels, or where clutched drum facilities exist, this method of push button control would be advantageous. Where more than two levels are involved this form of control would be wasteful of manpower. This could be overcome by using a travelling onsetter operating controls in one conveyance only; or by using a travelling onsetter in each conveyance with one having master control. This latter arrangement would allow maximum utilisation of the two conveyances at peak manriding times.

229 On clutched drum winding engines, the clutch facilities have to be suitably interlocked for working in the automatic mode. Before automatic winding can be selected, the conveyances would have to be moved by manual control to the required levels and then detected at those positions by suitable proximity devices. The proximity switches at a chosen level would then be interlocked with a selector switch in the winding engine house, so that retardation cams appropriate to the levels in use are selected.

230 The NCB is preparing a code of requirements for winding between two levels, with initiation of winds from shaft sides by push buttons operated by banksmen and onsetters.

231 The best method of establishing the most suitable form of push button control and necessary protective devices would result from trial installations. To achieve this it would be necessary to consider the following:

(1) Provision of suitable shaft side gates for use during man winding which would be automatically locked in the closed positioning when a conveyance moves away from the landing.




(2) Provision of retractable platforms which could be operated from a stationary conveyance at an inset.

(3) Availability of a person, normally otherwise employed, who is authorised to operate the winding engine manually in case of failure of the push button system and for other operations such as rope and shaft work.

6 Abstract of recommendations

Subsection Paragraph Recommendation

Automatic contrivances: electrical aspects

33(1)

(2)

All new automatic contrivances be designed to incorporate the features described in paragraphs 31 and 32 and in Part 2B section 3.

All existing category A type automatic contrivances be modified at the time of major overhaul to incorporate the features described in paragraph 31 and 32 and in Part 2B section 3.

Emergency brake solenoids

44 Means, such as a push button, be provided in each emergency brake solenoid circuit for independently testing the operation and interlocking of each emergency brake valve; and these means be accessible only to authorised persons.

Control system safety

52(1)

(2)

(3)

New design of winding engines should incorporate the following features: -contactor ‘anti-freeze’ protection to the stator contactor of each AC open-loop winding engine; -protection against an electrical fault which could close the main contactor of an AC open-loop winding engine with the winding engineman’s lever in the off position; -arrangement of control circuits of each AC closed-loop winding engine to prevent application of excessive power while the mechanical brake is holding the drum stationary; -protection against excessive current in the main DC loop of each DC winding engine; and -trip of the safety circuit if a fault causes power to be applied to the motor to move a winding engine in the opposite direction from that selected.

New designs of winding engine and existing winding engines should incorporate the following features: -prevention of brake system pumps or compressors from being started when the brake level is not in the full on position; and -a circuit to ensure that mode selection cancels all previous control instructions where control mode selection is provided such as from manual to semi-automatic.

Existing winding engines be examined and consideration given to incorporating the features listed under recommendation 52(1)





Steam winding engines and auxiliaries

67(1)

(2)

Winding engine mechanical brakes applied wholly or partially by steam or air pressure be replaced unless they are automatically backed up by a means independent of such pressure.

Provisions be made to minimize the possibility of carry over of water from boilers to steam winding engine valve chests and cylinders; and also to minimize accumulation of condensate in these components.

Design principles for arrestors in friction winding installations

81(1)

(2)

(3)

The existing design principles for arrestors should continue to be used.

For all future friction winding installations with two cages or skips, sump bumping beams be so located that they be struck after those in the headframe and thus allow elasticity of the winding rope(s) to assist retardation of the descending conveyance; but sump arrestors should continue to act in advance of headframe arrestors.

For all future counterweights installations, bumping beams for a descending counterweight should be in advance of those in the headframe, to relieve the ascending conveyance of the energy of the descending counterweight.

Balance ropes 130 The following be adopted for balance ropes on drum winding engines: -a minimum breaking strength when installed of six times the maximum static load which the rope will carry in service; and -a working life determined by the condition of the rope as revealed by examination but not exceeding five years from when first put into use.

Control of balance rope loops

132 The design principles for balance rope loop control detailed in paragraph 3 of section 11 in Part 2B be adopted where applicable for all new and existing installations.

Monitoring of balance rope loops

137(1)

(2)

Loop monitoring devices be installed where applicable with balance ropes, and such devices be of a type which fails to safety.

Operation of a balance rope loop monitoring device be arranged to trip the winding engine safety circuit and to give indication to both the winding engineman and onsetter.

Shaft side equipment

156(1)

(2)

Shaft side equipment and associated vehicle handling apparatus should be designed and interlocked where necessary so that, when the automatic contrivance of a winding engine is set for manriding, all items of decking equipment not required for that operation are rendered inoperative, to prevent their inadvertent movement from causing injury to persons entering or leaving a conveyance.

Where normal operation of shaft side equipment at an intermediate inset causes apparatus to protrude into the path of a conveyance, the equipment be designed and interlocked so that movement from its fully retracted or safe position when the conveyance is not in line will cause the winding engine safety circuit to be tripped and the brake to be automatically applied.





Shaft signalling systems

158

160

(1)

(2)

(3)

(4)

(5)

In addition to the recommendations in paragraph 90 of Part 1A, all existing shaft signalling systems be examined with the view to incorporating the following features where these can be included without major modification: -earth fault monitoring devices to give warning only, unless systems already possess adequate protection against earth faults that could cause false or incorrect signals; -reliable emergency stop circuits and components; -cancelling devices driven from the winding engine which are capable of positively distinguishing between stationary and creep speed conditions; -automatic restoration of the incomplete signal protection by operation of the cancellor or completion of the wind, where first man in facilities involve the use of special onsetter riding signal (say 9) to override incomplete signal protection; -provision for interfaces between shaft signalling systems and other winding equipment, for example, brakes, men/coal selectors and kep interlocks; -visual indicators, to show emergency stop and keps clear, in addition to those showing the position of the men/coal selector, brakes on and brakes locked on, positioned to be readily seen by persons about to enter or leave a conveyance; -suitable standby power supplies; -visual indication of signals at all signalling stations; -environmental protection of apparatus and signalling push buttons or Keps designed to prevent accidental operations. For future systems, in addition to paragraph 90 Part 1A and 158 of Part 2A:

When a signal selected is the same as that received, visual and audible indication of the signal be displayed to the winding engineman, banksman and onsetters; otherwise, an error signal be so displayed.

A visual indicator and a discrete push button or key be provided for each signal; and, where possible, the frequency of audible tones be unique to a particular landing.

The signal one to stop be distinguished from the signal one to raise: a separate signal key and indicator is usually necessary to achieve this.

Relays used for raise and lower signals be not utilised in other combinations of signals.

Signalling systems which are certified as intrinsically safe be available for use where required particularly in upcast shafts at gassy mines.





Maintenance procedures and documentation

176(1)

(2)

(3)

(4)

Statutory books for reporting on examinations and test required by the Coal and Other Mines (Shafts, Outlets and Roads) Regulation 1960, and corresponding reporting requirements of managers’ schemes for the mine, be reviewed to avoid duplication, to improve standards of reporting and to ensure adequate subsequent action.

Managers’ schemes for the mine should incorporate supervisory checks of headframe and shaft equipment to ensure that routine examinations and tests are being thoroughly carried out.

Use of shaft winding equipment be reviewed to ensure that adequate time is scheduled for examinations, tests and maintenance.

When planning examinations and maintenance, any hazards be identified and safe working methods and procedures established.

Maintenance of foundations buildings, structures and shaft linings

180(1)

(2)

(3)

The mine manager should have a scheme for the examinations of foundations, buildings and structures associated with winding installations and for the examination of shaft linings; and this scheme be similar to that required for mechanical and electrical apparatus.

Reports of shaft examinations be made on a form similar to that illustrated in Fig 16.1 of Part 2B.

Consideration be given to clarifying legislation in Great Britain in respect of the mine mechanical engineer’s traditional responsibility for the maintenance of shaft linings.

Maintenance of ropes in winding installations

188 Each manager’s scheme for the mine should require that at suitable intervals every balance, guide and rubbing rope be thoroughly cleaned and examined at all places liable to deterioration, and at other selected places throughout its length.

Non-destructive testing of components of winding apparatus

207(1)

(2) (3) (4)

The revised classifications for components of winding engine mechanical brakes outlined in paragraph 197 be adopted; and paragraph 114 of Part 1A be superseded and appendix 5.1 of Part 1B modified.

Intervals between non-destructive tests of winding components be those specified in table 2; and recommendation 118(3) of Part 1A be superseded.

The guidelines to suggested action following non-destructive testing, in appendix 5.4 of Part 1B, be modified by deleting figs 5.3 and 5.4 and replacing entries under ‘nuts’ ‘pins’ and ‘clevises’ by those in table 1.

Non-destructive testing during manufacture be specified for important components of winding apparatus.

Testing of friction winding engines

213 The model testing code in section 32 of Part 2B for friction winding engines be adopted.





Brake performance tests

220(1)

(2)

The existing brake holding test continue to be applied each shift to drum winding engines, preferably before man winding.

A brake holding test be also applied to friction winding engines but at torques as defined below, using empty conveyance(s): -a power torque of twice maximum static torque in the case of two conveyances taking into account unequal weights of balance and winding ropes; or, where a motor will not develop twice maximum static torque, the maximum torque available to the winding engineman; or -a power torque of 1.5 times maximum static torque in favour of the counterweight in a conveyance and counterweight system.

7 Further work

232 The following development work will be undertaken by the NCB and the HSE:

(1) The design guide Continuation of work on stress analysis and fatigue, promulgation of good design practice an assessment of materials with updating as appropriate.

(2) Pit bottom buffers Assessment and testing of new and existing designs of pit bottom buffers and monitoring longer term aspects of ageing and fatigue.

(3) Non-destructive testing Review of frequencies of testing and updating of techniques.

(4) Torque reaction devices Investigating means of integrating these devices into winding engine control systems; and any necessary further development.

(5) Automatic application of dynamic braking Continuing investigation and development of suitable systems.

(6) New concepts of winding system protection and communications Continuing investigation and development of means of providing slack rope protection, conveyance position monitoring, monitoring of rope creep and rope slip, and automatic contrivance monitoring.

(7) Push button control of man winding Development of systems for AC and DC winding engines.




PART 2B Application of Principles for shafts and supporting information




Contents of report - Part 2B Winding engines 61 1 Recommended materials for winding engine brakes 61 2 Mechanical brake torque sensing apparatus 63 3 Automatic contrivances: desirable electrical design and installation features 69 4 Supervisory devices for automatic Contrivances 70 5 Magnetic marking of winding and guide ropes 71 6 Emergency brake solenoids 72 7 Friction between rope and drum 73 8 Assessment of reliability of systems 74 Headframe and shaft equipment 79

9 Measurement of conveyance deceleration 79 10 Pit bottom buffers 81 11 Control of balance rope loops 89 12 Monitoring of balance rope loops 92 13 Shaft signalling systems 92 Maintenance, testing and training 95

14 Maintenance procedures: statutory report books 95 15 Maintenance: Safe working procedures and control 95 16 Maintenance of foundations, buildings, structures and shaft linings 98 17 Maintenance of equipment in towers, headframes and sumps 105 18 Maintenance of ropes in winding installations 107 19 Maintenance of suspension gear 120 20 Maintenance of conveyances 120 21 Maintenance of rigid shaft guides 121 22 Maintenance of shaft side equipment 122 23 Maintenance of shaft pipes and cables 122 24 Maintenance of electrical equipment 123 25 Maintenance of emergency winding apparatus 124 26 Lasers and other devices for aligning shaft equipment 125 27 Protection of steelwork from corrosion 126 28 Shaft air heating 126 29 Non-destructive testing of components of winding apparatus 127 30 An illustration of the application of techniques of fracture mechanics to a headframe pulley shaft 129 31 Monitoring of mechanical equipment 136 32 Model code for the testing of friction winding engines 140 Glossary 165 Appendix Sub-committees/Working groups/Drafting panel 170 Acknowledgements 177




Winding engines1 Recommended materials for winding engine brakes

In Part 1B, Section 4, there is a list of recommended materials for winding engine brakes. Experience of use of these materials for both new and replacement parts has been successful but the list has been enlarged by the addition of two materials. The full list is in the table below and the additional materials are marked by an asterisk. A column of rationalised choices is included to limit the types of steel which need to be used. The En classification of steels in BS 970: 1955 has been abandoned by the British Standards Institution but, for convenience, the old En references are in brackets where appropriate.

Material

Component General Rationalised

Brake paths Brake paths can be made either by casting or by forming steel plate. It is recommended that all new brake paths should be made from castings but replacement brake paths may be either cast or formed. Castings: Fine-grained pearlitic grey cast iron to either Grade 14 or 17 of BS 1452: 1961. Control of the graphite flake size by an inoculation process is recommended. Formed plate: 080M40 (En 8) of BS 970: Part1: 1972. The plate should have a minimum hardness of 152 Brinell.

Brake linings The linings, which should be asbestos-based, should be compatible with the brake path material and the specification should be supplied by the manufacturer for approval.

Brake shoes Grade 43A of BS 4360: 1972.

Brake posts Grade 43A of BS 4360: 1972, in sectional fabrication.

Anchor brackets These may be either cast or fabricated. Cast: Grade A of BS 1456: 1957 or Grade A of BS 592: 1957 (Specified Izod). (Both of these specifications are incorporated in BS 3100: 1976). Fabricated: Grades 43A, 43C, 43D, 50C, 50D of BS 4360: 1972, or 1.5% manganese steel 150M12* to BS 2772: Part 2: 1977.

50D 150M12*




Material


Brake shaft pedestals These may be either cast or fabricated. Cast: Grade A of BS 1456: 1957 or Grade A of BS 592: 1957 (Specified Izod). (Both these specifications are incorporated in BS 3100: 1976). Fabricated: Grades 43A, 43C, 43D, 50C, 50D of BS 4360: 1972, or 1.5% manganese steel 150M12* to BS 2772: Part 2: 1977

50D 150M12*

Brake shafts Grade 150M19 (En 14A) or grade 080M40 (En 8) of BS 970: Part 1: 1972, in the normalised or P condition (fine grain controlled).

150M19

Brake levers These may be either fabricated or forged. Fabricated: Grades 43C, 43D, 50C, 50D of BS 4360: 1972 in the normalised condition or 1.5% manganese steel 150M12* to BS 2772: Part 2: 1977 Forged: Grade 150M19 (En 14A) of BS 970: Part 1: 1972 in the normalised or P condition (fine grain controlled).

50D 150M19

Spring rods and tie rods incl turn buckles, rod ends etc.

Grades 43C, 43D, 50C, 50D of BS 4360: 1972 in the normalised condition or Grade 150M19 (En 14A) of BS 970: Part 1: 1972 in the normalised condition (fine grain controlled) or 1.5% manganese steel 150M12* to BS 2772: Part 2: 1977

50D 150M19

Pins Materials to be as for Spring Rods etc. For applications where size considerations preclude the use of these materials (i.e. where geometric factors are limiting) 817M40* (En 24), condition T BS 970: Part 2: 1970.

50D 150M19 150M12 817M40*

Bell cranks or triangular levers Grade 43A of BS 4360: 1972.

Springs Grade 250A58 (En 45A) or 735A50 (En 47) of BS 970: Part 5: 1972.

Thruster brake spring case, side plates and bridge reaction plates

Grade 43A of BS 4360: 1972.

Spring nest platforms Grade 070M20 (En 3A) of BS 970: Part 1: 1972 or Grade 43A of BS 4360: 1972.




Material


Low pressure brake engines (less than 200 lbf/in2 i.e. 1.4 MN/m2

Cylinders, covers, valve bodies, brackets, pedestals and other castings associated with the brake engines Pistons, valve spools etc.

Grades 14 or 17 of BS 1452: 1961. Control of the graphite size by an inoculation process is recommended. These may be machined from either cast or wrought material. Cast: Grade 14 or 17 of BS 1452: 1961. Control of the graphite flake size by an inoculation process is recommended. Wrought: Grade 070M20 (En 3A) of BS 970: Part 1: 1972 or Grade 43A of BS 4360: 1972.

High pressure brake engines Bodies Rams Non-metallic bushes

These may be from either cast or wrought material. Cast: Grade SNG 420/12 of BS 2789: 1973. Wrought: Grades 070M20 (En 3A) or 080M40 (En 8) of BS 970: Part 1: 1972. Either grade may be used with or without a spun cast liner. Grade 070M20 (En 3A) of BS 970: Part 1: 1972 with the surface plated with a 0.001 - 0.0016 in (25-40 µm) thick layer of hard chrome to BS 4641: 1970, or Grade 080M15 (En 32C) of BS 970: Part 3: 1971 Supplement No 1, case-hardened to a finished depth of 0.025 – 0.040 in (0.6 – 1.00 mm). Woven cloth impregnated with thermal setting resin; the specification should be supplied by the manufacturer for approval.

Non-ferrous bushes Grade PB1 or LG2C or BS 1400: 1973.

2 Mechanical brake torque sensing apparatus

Development of transducers (see paragraph 29 of Part 2A)

1 Initially, the feasibility of monitoring strains produced in brake shoes was investigated. A number of commercially available transducers were examined under static and dynamic conditions in the laboratory but were found to be unsatisfactory with regard to application and sensitivity. Subsequently, a contract was placed with a manufacturer to develop an existing type of transducer for attachment to brake shoes, and a prototype (fig 2.1) was submitted for laboratory tests. The transducer comprised a steel bar which had holes for bolting it to adaptor blocks welded to brake shoes. Longitudinal strains transmitted through the bar were mechanically amplified by a circular hole in the bar. Strains induced around the periphery of the




hole were measured by strain gauges interconnected to form a bridge circuit. Repeated applications of force were made on the transducer and after approximately two and one half million cycles there was no detectable change in output signal.

Mechanical brake torque monitoring system

2 An experimental method for monitoring outputs from brake torque sensing transducers is illustrated in fig 2.2. On a caliper brake, two transducers are bolted to the web of each brake shoe of one brake path: A and B in fig 2.3 are on each side of one web and C and D on each side of the other.

3 The transducers are connected to stable high gain amplifiers having zero balance and variable gain facility. They are balanced so that the amplifiers give zero output when the brake shoes are in the off position: and the summated output is zero when stationary conveyances are in balance with brakes applied. During braking, output signals derived from the individual transducers are proportional to the reactive forces, and signal polarity is dependent on direction of drum rotation. These signals are fed into an electronic summating system connected to provide a single output voltage proportional to brake reaction. This voltage is then fed to a unity gain amplifier fitted with an automatic zeroing feature to compensate for long term drift and hysteresis in the mechanical brake. Auto-zeroing is in continuous operation when brake shoes are in the off position and a microswitch, which detects movement of the brake shoes, locks the automatic zeroing feature ready for the output voltage to be measured when the brake is applied. The measured voltage is fed to a display unit scaled to give an indication of brake effectiveness. This voltage is also fed to an adjustable voltage comparator: provided the voltage exceeds the level at which the comparator is set, a trip unit controlled by the safety contactor is actuated to control removal of electrical braking. A time delay unit is incorporated to inhibit action in order to allow for settlement times and other time lags in the mechanical brake.

Test results of mechanical brake torque monitoring system

4 A typical trace of summated signal output from four transducers on a 700 hp (520 kW) AC cage winding installation with a 10 ft (3m) diameter drum driven through gears, is shown in fig 2.4.

5 The results in table 2.1 were obtained from a 3560 hp (2650 kW) DC installation with a dual path caliper type mechanical brake operating on a directly driven 20 ft (6.1 m) diameter drum. Four transducers were fitted to monitor reactive forces at one brake path (fig 2.5). Summated outputs from the transducers were monitored during simulated emergency brake applications over a wide range of operation such as with empty and loaded skips, different winding speeds and both directions of drum rotation. Sensitivity of the electronic monitoring system was calibrated to produce a resultant output of 1000 millivolts for the condition of the brake holding

Figure 2.1 Brake torque sensing transducer




test, referred to in paragraph 18 of section 32 of Part 1B. Summated values were obtained from a data printer set to print out every 0.3 sec for a duration of 5 sec. Examination of results showed that the summated output from the transducers varied as expected with the level of brake application. The outputs were repeatable and independent of operating conditions during emergency braking.

Figure 2.2 Experimental monitoring system

Figure 2.3 Transducers on caliper brake shoes

Operational systems

6 A specification was based on the experimental system and a contract placed for the production of an operational system. Outputs from transducers, fitted at both brake paths of a drum, monitor effectiveness of the brake and can be used for controlling retention, removal or re-application of electrical braking. Proving of a preproduction version by trials at a colliery has been completed.

TransducerA

Amplifier Brake shoeswitch

Automaticzero

Displayunit

DelayFrom safetycontractor

Comparator Relay tripunit

Output

TransducerB

Amplifier

TransducerC

Amplifier

TransducerD

Amplifier

Summator




Figure 2.4 Typical trace of output from four transducers

Figure 2.5 Brake torque sensing transducers fitted to brake shoes of a caliper type brake

7 Investigations are being made of transducers suitable for embodiment in structures or hinge pins of brake shoes or posts. Various designs are being assessed and prototype versions will be subjected to laboratory and colliery trials.

This trace is the summated output from transducerson a cage winding installation

Brake off

Drum rotating30 ft/sec

Brake on

Zero

Ocillationdue to cage

Time 1 cm = 0.5 seconds

First peak

Range of readings

Brake holdingtest level1000 mV

Sign

al 1

cm

= 1

00 m

V

Prop

ortio

nal t

o m

echa

nica

lbr

akin

g to

rque

Drum retarding7.2 ft/sec2 (average)

Brake on

Drum static

()




8 Disc brake systems are being introduced and it is intended to incorporate equipment for monitoring braking torque in their design. One method being investigated is the use of pins fitted with strain gauges in the mountings of disc caliper units.

Brake torque sensing devices and winding engine circuits

9 The function of a torque sensing device is to indicate whether the mechanical brake on a winding engine is effective prior to removing electrical braking after an emergency or automatic trip. Following successful trials of the torque sensing device referred to above consideration was given to its connection into winding engine circuits.

10 Where they are used, torque sensing devices should be connected into appropriate circuits of a winding engine by means of an interposing relay. Visual and audible indication should be given to the winding engineman if the mechanical brake is ineffective after initiation of an emergency trip: this can be effected by provision of a latched relay operated by contacts on the interposing relay and safety contactors, so that cause of the trip must be investigated before winding can be resumed.

11 Where a torque sensing device is installed with a DC winding engine, circuitry has to suit the plant involved. For an open-loop DC winding engine, the interposing relay could be arranged to operate in conjunction with field discharge circuits. With a closed-loop Ward Leonard system, the interposing relay could be arranged to operate in conjunction with the speed reference and field discharge circuits. With a closed-loop converter supplied winding engine, the interposing relay could be arranged to operate in conjunction with the speed reference circuit and the regulating and/or phase shift circuit.

12 Operating settings for torque sensing devices need to be determined for each winding installation.

Table 2.1 Typical results from tests carried out on a skip winding installation with caliper type brakes

Summated value (mV)

Test conditions FIRST PEAK

RANGE OF READINGS

Nominal rope (ft/sec)

Retardation (ft/sec2)

Drum direction

Test No.

Normal wind Cages out of balance

660 - - - Static 1

Forward brake holding test 1000- - -

Static 2

Reverse brake holding test 1000- - -

Static 3




Summated value (mV)


RANGE OF READINGS


Retardation speed (ft/sec2)

Drum direction

Test No.

Both Skips Empty – Overlap Skip into and out of shaft bottom

150612451175126412001333129812821246

1011 - 15061245 - 13791175 - 14631264 - 13931200 - 13111285 - 13331180 - 13391282 - 13501175 - 1312

102030454510203045

14.012.412.012.111.814.013.913.914.2

R R R R RF F F F

456789101112

Man Weight in Underlap Skip-Underlap Skip into and out of shaft bottom

1405134012541269132113171296129612961309

1405 - 14231340 - 14011254 - 13941235 - 12991289 - 13211187 - 13171231 - 12961203 - 12961296 - 12971303 - 1309

1020304510203045-6

12.012.111.711.413.313.913.713.9Peak power test Peak power test

R R R R F F F F R R

13141516171819202122

Man Weight in Underlap Skip – Underlap Skip into and out of shaft top

134312961215123713171373127412731248

1330 - 13431223 - 12961210 - 12941181 - 12481303 - 13171324 - 13731243 - 12681228 - 12731163 - 1248

102030451020304545

11.512.112.512.412.912.612.6-11.2

F F F F R R R R R

232425262728293031

Man Weight in Overlap Skip – Overlap Skip into and out of shaft bottom

129212631240122512021262125712391153

1283 - 12921201 - 12631225 - 13091198 - 12371155 - 12261235 - 12621015 - 12571212 - 12451117 - 1153

102030454510203045

12.111.511.611.811.911.912.612.510.8

F F F F F R R R R

323334353637383940

Man Weight in Overlap Skip-86% Braking-Overlap Skip into and out of shaft bottom

1136109211581078108510711050942999

1121 - 11361047 - 10921137 - 12101032 - 10921071 - 10851040 - 10711014 - 1058902 - 942962 - 999

102030451020304545

10.010.010.510.411.111.711.511.311.0

F F F F R R R R R

414243444546474849




Summated value (mV)


RANGE OF READINGS


Retardation speed (ft/sec2)

Drum direction

Test No.

Coal Weight in Overlap Skip-Overlap Skip into and out of shaft bottom

13201261122612011275131212711213

1320 - 13401233 - 12611197 - 12591157 - 12401260 - 12751267 - 13121261 - 12961154 - 1213

1020304510203045

11.3-10.110.212.912.313.213.5

F F F F R R R R

5051525354555657

Coal Weight in Overlap Skip-Overlap Skip into and out of shaft top

12691287124912451254122912251199

1257 - 12691220 - 12871219 - 12651167 - 12471235 - 12541226 - 12361195 - 12271114 - 1199

1020304510203045

11.111.611.511.310.311.611.812.1

F F F F R R R R

5859606162636465

F=Forward R=Reverse Man Weight=21cwt Coal Weight=11 ton (approx)

3 Automatic contrivances: desirable electrical design and installation features

1 Standards for, and methods of, achieving the desirable features recommended in Part 2A, paragraph 33, are set out below:

(1) Cables should be terminated by using compression type glands on a suitable gland plate and insulated crimped connections to a suitably located terminal block, or a similar method which does not impair reliability of terminations. Methods of terminating incoming cables and internal wiring should be of high integrity so that the risk of short circuit or earth fault is negligible.

(2) Terminal block design should be such that there is adequate separation between adjacent terminals to reduce to a minimum risk of inadvertent displacement of a connection which may cause inter wiring or earth faults.

(3) Account must be taken of the fact that wiring on site may be carried out by electrical staff who do not have specialist wiring skills.

(4) Internally, screened cables should be used where there could be risk of the development of a wiring fault in high integrity circuits. Where there is little risk of such a wiring fault, unscreened cables may be used, but they should have good quality insulation and should be properly supported and segregated as necessary.

(5) Screens of screened core cables should be terminated at suitably located points close to where they are separated from a cable, while maintaining adequate segregation between the screens and terminal block.

(6) BS 5501:Part 7:1977 (Electrical apparatus for potentially explosive atmospheres: intrinsic safety ‘i’) Sections 5.4, 5.5 and Table 2 should be used as a guide with respect to wiring, terminals, creepage and clearance distances, and insulation.




(7) Ends of wires should be clearly identified by the use of numbers.

(8) Methods of operation of contacts and contact action should be reliable and of high integrity. Generously rated, air break, normally closed, overspeed and overwind contacts, should be used; they should be positively driven to the open position as distinct from spring operated. Where auxiliary contacts for control purposes are employed, these should not reduce the integrity of relevant tripping circuits.

(9) Each switch and contact should be clearly identified as to its purpose.

(10) A warning label should be fixed in a prominent position on an automatic contrivance drawing attention to live electric parts within.

(11) Acceleration relief features should be designed out; where this is not possible, consideration should be given to:

- eliminating acceleration relief on man winding duty;

- designing the acceleration relief feature used on mineral and coal winding to fail to safety; and

- making any fault on the associated directional changeover switch self revealing.

4 Supervisory devices for automatic Contrivances

1 Reference is made in paragraph 34 of Part 2A to the use of supervisory devices for monitoring operation of automatic contrivances. The overspeed protection provided by the supervisory device should be effective for the full speed and retardation periods, in each direction of wind. Its setting should not be more than 5% above the setting of the automatic contrivance, or 20% above normal man winding speed, whichever is the lower. Overspeed protection should be provided during the acceleration period but need not be so closely set. Where the winding engine speed for mineral or material winding is greater than that for manriding, a setting should be provided on the device for this duty. The changeover should be affected by operation of the man/coal selector which forms part of the normal winding engine controls. The device should provide overwind protection against movement of a conveyance beyond the overwind setting of the automatic contrivance at the highest and lowest normal winding positions. Where a clutched drum winding engine is in use, the supervisory function should individually apply to each drum.

2 Output signals from a supervisory device should be terminated in relays with suitably rated contacts for connecting into the safety circuit.

3 An automatic contrivance or a supervisory device is each in itself a single line component but when used together they form a dual system ie provide redundancy. Means should be provided whereby they can be operationally checked and where possible their faults should be self revealing. Because the additional complexity would be undesirable and may make the devices less reliable, cross interlocking should only be adopted after careful consideration.

4 The supervisory device should be so designed that electrical interference whether carried by the power supply, propagated by radio, or induced by other means has no adverse effect on its operation. Loss of power supply to the device




should trip the safety circuit and stop the winding engine. This could result in loss of co-ordination with the automatic contrivance necessitating resetting the supervisory device.

5 Means should be available to enable the supervisory device to be operationally tested. This can be provided by shortening the full speed proportion of the protection curve of the device by an appropriate distance to create an artificial landing. Indication provided by the device should include distance travelled by one conveyance in linear units or drum revolutions, and the difference between actual speed and the tripping speed.

5 Magnetic marking of winding and guide ropes

1 In Part 2A, paragraph 39, there is reference to the use of magnetic marking of ropes in shafts in connection with conveyance position monitoring. Magnetic marking of one winding rope of a 4-rope tower mounted friction winding engine was carried out in 1976. The magnetic intensity at the marks diminished by 50% in the first three months but thereafter remained substantially constant. Two flux gate magnetometer detector heads for detecting the magnetic marks are positioned in close proximity to the rope near where it passes over the friction drum, with a digital and analogue display of conveyance position sited at the winding engineman’s position.

2 The first rope was marked using hand held permanent magnets but a powered pulsed electromagnet equipment weighing 50 1b (23 kg) has since been developed to slide on the rope. The electromagnet has poles 8 in (20 cm) apart with faces of radio metal to avoid blurring, and detachable so that they can be changed to suit different sizes of rope. It is powered from a 12 volt battery and has a capacitor which is charged to 300 volt and discharged through the magnetising coils, to give a steep fronted wave and a clean magnetic mark on the rope. The electromagnet is triggered by a follower wheel driven by the rope to provide magnetic marks at 8 in (20 cm) intervals. Normal speed of marking is about 2 ft/sec (0.6 m/sec) but may be increased up to 6 ft/sec (1.8 m/sec). A shaft rope can normally be marked in about one hour.

3 The use of two detector heads doubles the number of generated pulses so reducing the increment for detection to 4 in (10 cm) and enabling direction of motion of rope or conveyance to be established.

4 The indications so far are that magnetic marking should last the life of a winding rope if taken initially to saturation, provided that the marking is not removed or distorted for example by magnetic non-destructive testing. Care will also have to be taken when other components are subject to non-destructive testing. To ensure that a rope is magnetically clean before marking or non-destructive testing, a rope ‘wiping’ device has been developed which may be powered from the mains or from a 12 volt battery and a DC to AC converter.

5 Magnetic marking can be applied to either winding or guide ropes but has so far only been used with locked coil winding ropes and half lock guide ropes. Detector heads for either type of rope would be basically the same but to make use of information provided from guide ropes it is necessary to develop suitable communication between conveyances and the surface. A satisfactory system of communication between a conveyance and the surface has been established using the inductive loop principle with a guide rope forming part of the loop. Signals from the conveyance are transmitted up the guide rope from a toroidal coil to a similar coil at the surface. Power required at the transmitter on a conveyance to provide a good clear signal at the receiver is approximately 0.05 watt and this means that a suitable intrinsically safe battery will provide power for more than a week.




6 Emergency brake solenoids

1 Ways in which emergency brake solenoid valves can be monitored and provision made for manual testing, as referred to in Part 2A, paragraphs 42 and 43 are:

(1) a directly operated switch, providing the action of the switch does not impede the opening of the valve; or

(2) a suitable optical device, if the final movement of the valve is very small or where a directly operated switch is likely to impede the opening of the valve; or

(3) comparison of fluid pressure in the two valve circuits, particularly if the valves are of the free spool type and external access to the spools is not possible.

2 The monitoring system and its associated circuitry should fail to safety. Fig 6.1 illustrates a typical circuit for the emergency brake solenoids (EBS1 and EBS2) of a winding engine. Contacts of the relevant safety circuit contactors are connected in series in each emergency brake solenoid circuit, together with push buttons for manual testing of the circuit. When fully open each valve operates a contact which is used for monitoring purposes. Fig 6.2 illustrates one method of monitoring the operation of the emergency brake solenoid valves. Follower relays R1 and R2 are energised when the valves open, closing contacts R1.3 and R2.3 in the reset circuit. If a valve does not open, or a relay is not energised, then the safety circuits cannot be reset. A parallel connected circuit using contacts R1.1, R2.1, R1.2 and R2.2 will give an indication ‘EBS valve malfunction’ if either the valves or the relays are not in the same mode.

Figure 6.1 Emergency brake solenoid (EBS) circuit

Figure 6.2 Energy brake solenoid valves (EBS) monitoring and indication

1a1 1a2 1b1 1b2 21 22Test

Monitoringcircuit

E.B.S.1

E.B.S.1.1

Monitoringcircuit

1a1 1a2 1b1 1b2 21 22Test E.B.S.2

E.B.S.2.1

Safety contactor contacts

Reset circuit

EBS valvemalfunction

R1.1 R2.1

R1.2 R2.2

E.B.S.1

1a1 1a2

R1

E.B.S.2

R2




7 Friction between rope and drum

1 In the late 1940’s, friction winding installations were adopted at a number of new and reconstructed mines after making investigations in Germany where this system was predominant. At that time there were only three friction winding installations operating in Great Britain: the largest was a single rope system at Murton Colliery which used a locked coil winding rope and elm wood friction treads. Tests were made at this installation using a decelerometer in one cage and a tensometer on the winding rope. Records from these instruments indicated the effects of rope oscillation induced during emergency braking and the corresponding changes in the ratio of tensions in the rope at each side of the sheave. At about the same time, laboratory experiments were also made by winding rope and winding engine manufacturers to determine the static coefficient of friction between various tread materials and types of winding rope. Based on this work, the combination of locked coil winding rope(s) and elm wood friction treads was selected for most of the early single rope friction winding installations. For later multi-rope friction winding installations the same combination was generally used, although in some installations alternative materials were introduced for friction treads such as iroko wood or inserts made from stampings of PVC conveyor belting bonded together to form tapered blocks. Wooden treads used on multi-rope friction winding engines are usually in the form of solid or laminated laggings laid across the drum and it has sometimes been difficult to obtain replacements of properly seasoned timber. Because of this and the successful application of synthetic friction treads in Europe, further investigations and tests have been made in Great Britain to find suitable alternative insert tread materials for use with locked coil ropes.

2 In order that the frictional properties of alternative materials could be compared with those of elm wood, a series of laboratory experiments was made to establish a standard method of test. Paragraph 69 of Part 2A refers. The main test rig employed is shown in Fig 7.1: this uses a 0.75 in (19 mm) diameter locked coil rope and has a 5 ft (1.52 m) diameter pulley designed to accommodate friction tread inserts. The rope is tensioned by screw arrangements to produce tread pressures of up to 500 lbf/in2 (3.45 MPa) and the pulley is rotated at a peripheral speed of 0.0006 in/sec (0.015 mm/sec) by a lever driven from a motor and worm gear, to increase the ratio of rope tensions until slip occurs. Experiments started in 1958 and over the years a considerable amount of testing has been done to evaluate properties of available and developed materials under dry, wet, icy and lubricated conditions. The scale effect resulted in a tendency to underestimate coefficients of friction of the materials, but the rig was nevertheless a satisfactory means for comparing their frictional properties with those of elm wood. Results show that plastic materials when tested dry tend to have coefficients of friction higher than wood, that water has little effect on the frictional properties of plastic materials but causes the coefficient of friction of wood and other absorbent materials to increase, and that lubricants and ice have a deleterious effect on the frictional properties of all the materials tested.

3 The dynamic coefficients of friction and wear properties of some materials were also determined at a friction winding installation. A shoe containing a sample of the material, and instrumented to measure resultant forces generated at the shoe, was situated between the winding drum and deflector pulley and forced against a moving winding rope. The apparent coefficients of friction were then evaluated from the forces measured at winding speeds, up to 15 ft/sec (4.5 m/sec). In general, the coefficients of friction of the plastic materials increased as rope speed increased but those of wood seemed to be unaffected. The amount of wear measured during the tests was negligible and this can be attributed to the locked coil winding ropes which have relatively smooth surfaces.




Figure 7.1 Diagram of the friction test rig

4 On some friction winding engines, troubles experienced with locked coil winding ropes appear to have been aggravated by synthetic inserts in the deflector pulleys. The coefficient of friction of these synthetic inserts is sufficient to restrict the natural tendency or the winding ropes to turn in their grooves. To minimise this possibility, standard Betathane (urethane elastomer) inserts for deflector pulleys can be obtained with polytetrafluoroethylene (PTFE) added to reduce the coefficient of friction. Standard Betathane inserts without PTFE would nevertheless normally be used in any deflector pulley that drives ancillary equipment in order to reduce the possibility of slip between defector pulley and winding rope. It is considered that deflector pulley inserts containing PTFE should be of a different colour from standard Betathane inserts and that inserts for a main driving drum should be of a different shape from those fitted to deflector pulleys. The manufacturer should draw the attention of users to these aspects.

5 The considerable amount of testing which has been done on frictional properties of different materials has shown that some plastic materials are comparable with wood, and have better recovery features. It is considered that these plastic materials should be tried to augment those already available for rope treads on drums of friction winding engines. Drums of more friction winding engines could be modified to accept renewable rope tread inserts; and selected materials could continue to be tested and proved to augment those already available for rope treads on drums of friction winding engines.

8 Assessment of reliability of systems

1 Principles of formalised techniques of reliability assessment have been developed over a number of years, notably by the aircraft, nuclear and chemical industries. In Part 1B section 21, the principal methods are outlined with particular relevance to the safety of mine winding installations. As referred to in paragraphs 51 and 52 of Part 1A, after consideration of alternatives, the NCB commissioned the Atomic Energy Authority Systems Reliability Service (SRS) at Culcheth, Nr Warrington, to undertake a pilot assessment at No 1 Shaft, Markham Colliery, Derbyshire. The principal results and steps of the SRS study are outlined in

P = O

Hydraulic tension capsule10 ton capacity

Hydraulic tension capsule10 ton capacity

Chaindrive

Electricmotor drive

Wormshaft

Wormshaft

Pulleyarm

0.75” (19 mm)lockedcoil rope

Handwheel

Tank

5’ (1.52 m) dis pulley

Recorder

Recorder

Recorder

P

P

T0 T0

T2

T2

T1

T1Startingcondition

Testcondition




paragraph 4 and their application to other installations reviewed. The report of this assessment is of considerable length with a full and detailed exposition of the procedures used, including assembly and treatment of failure rates for components where the lack of appropriate data, especially rare event data, has presented difficulties. A much simplified step by step procedure, capable of application by engineers with a minimum of special training, was considered necessary for general application of the techniques. Paragraph 70 of Part 2A refers.

2 The simplified procedure aims to achieve its object by the following and will be tested by practical application within the industry:

(1) use of failure rate data already assembled by SRS, with adjustment where specific circumstances demand;

(2) omission of mathematical and empirical justification for basic procedures that was included in the SRS report; and

(3) reduction of probability calculations to their simplest form by ignoring terms which the SRS study has shown to be negligible.

3 Outline of simplified procedure Basic steps are:

(1) Definition of the objectives, functions, systems, assumptions, etc.

(a) Definition of assessment objectives: eg to determine in quantified form the probability of occurrence of a given hazard in a given period.

(b) Determination of functional and physical boundaries of the system eg whether the consideration is that of danger to men when being transported or of system availability; and whether it is a major sub-system such as the mechanical brake, or a complete winding engine, or a winding system including the shaft, headgear and auxiliaries.

(c) Definition of system requirements: eg to transport men safely; or to operate reliably with maximum availability.

(d) Definition of system failure; this may be failure to meet the requirements of (c) above, or inability to meet some minimum braking criterion such as 50% of designed braking effort.

(e) Compilation of assumptions upon which validity of the analysis will depend.

(2) Qualitative analysis of the system.

A logic block diagram representing the functioning of the complete system is constructed. The diagram should be complete down to the simplest identifiable function and show the relationship between identifiable functions for successful system operation. Several diagrams may be required to show different conditions such as normal, overwind, overspeed etc.

(3) Quantitative analysis of safety and reliability.

(a) Establishment of the relationship between the system and its constituent parts. The system is broken down into series and/or parallel blocks; and the overall failure probability considered in terms of failure probability for individual blocks. At this stage the block probability values are not likely to be in numerical terms.




(b) Derivation of failure probability for each block in the main logic diagram. The failure probability for each block is derived from failure rates of its individual components. Arrangements of components within each block generally fall into one of the following categories:

- components in series,

- components in parallel,

- components combined in series and parallel,

- systems containing one or more cross links forming a lattice network, and

- systems containing force splitting arrangements, such as a brake engine in four sections in which breakage of one section could be assumed to reduce effective braking force from 100% to 75%.

Given the appropriate technique of analysis for each of the above categories, probabilities of block failure can be derived from failure rates of individual components. It should be assumed that all failures are random and that the cumulative probability of failure corresponds to an exponential distribution, that is the probability of failing over a given period is assumed constant throughout the working life of the component.

(c) Determination of overall system failure rate by substitution of block failure rates in the main logic diagram. The resultant diagram provides two primary items of information:

- an overall assessment of the hazard involved in operation of the complete system; and

- the relative contribution of each block of components to the overall hazard, thus identifying sensitive areas.

The document presenting the simplified procedure contains a method of analysis for all likely configurations of components and sub-systems or blocks, based on standard probability theory which has been simplified by ignoring those terms which can in practical circumstances be neglected. Criteria for ensuring that such terms are negligible are explicitly stated. The resultant method has been resolved into five basic rules, with examples of their separate and combined applications. An example of use of logic block diagrams and the assessment method is in Appendix 8.1.

4 Brief outline of the SRS report on the No 1 winding installation at Markham Colliery, Derbyshire

(1) The prime objectives of the SRS study were:

(a) to determine in quantified form, the probability that a hazard will arise during manriding in any period of one year as a result of the occurrence of random faults in the winding system;

(b) to identify sensitive areas in the system;

(c) to carry out a detailed assessment of the electrical safety circuit; and

(d) to make such recommendations as might seem appropriate to enhance reliability of the winding system.




(2) Major steps in the SRS study were:

(a) to obtain a thorough understanding of the system;

(b) to prepare logic diagrams expressing ways in which hazards might occur;

(c) to collect failure rate data from a variety of sources such as the SYREL data bank*, NCB and HSE records, other industries, or, where necessary, to make estimates based on engineering judgement; and

(d) to substitute failure rate data in the appropriate logic diagrams and calculations of overall probability of system failure.

(3) The requirements of the study were confined to failures involving a hazard to men; mechanical breakdown of damage was not considered except where there was possible danger to men.

5 Reliability assessment techniques by other organisations A number of visits were made to other firms and establishments who had direct experience of reliability systems techniques and their application to improvement of safety and plant availability. The information gained has been helpful in assessing:

- probable size and staffing requirements of a reliability team,

- varying methods of data collection, analysis and retrieval,

- methods of deriving rare event data, and

- quality of data from different sources.

6 Conclusions:

(1) The SRS report shows the way towards a rigorous method of reliability and safety analysis and indicates how component and sub-system reliability can be assessed in order of importance.

(2) Because various assumptions had to be made, the quantitative results of the SRS report are subject to qualification and should therefore be treated with caution; but significant conclusions are that travelling in a conveyance in a shaft is estimated to be safer than riding on an omnibus, and about thirty times safer than travelling in a motor-car.

(3) These techniques could be moulded into a sufficiently simplified form to allow widespread application to winding installations.

Logic block diagram for system success

* SYREL data bank: a systems reliability data bank which forms an integral part of the UK Atomic Energy Authority Systems Reliability Service. See paragraph 50 of section 21 of Part 1B.

Contact 1opens

Contact 1opens

Emergencybrake

solenoid 1de-energies

Emergencybrake

solenoid 2de-energies

Safety contactor 1

operates

Safety contactor 1

operates

OROR




APPENDIX 8.1 Example of use of logic block diagram and assessment method

1 A schematic diagram for a typical emergency braking system would in part be as follows:

where SC1 and SC2 are the contacts of two independent safety contactors; and EBS1 and EBS2 are independent emergency brake solenoids which initiate emergency application of the mechanical brake when they are de-energised.

2 The safety contactors and emergency brake solenoids are duplicated and a logic block diagram for system success can be constructed as below.

3 If it is assumed that in the event of a demand being made on the system during a specified proof check period:

P1 = probability that one of the safety contactor fails to move to the open position when de-energised,

P2 = probability that contacts of a safety contactor fail to open when the safety contactor moves to open position and

P3 = probability that an emergency brake solenoid fails to release its armature when de-energised, then probability of overall system failure, or unreliability is given by

Q = (P1 + P2)2 + P2 3.

4 Assuming a one week proof-check period, typical probabilities may be as follows:

P1 = 1.9 x 10-5

P2 = 2.85 x 10-5

P3 = 1.9 x 10-5.

Hence, assuming weekly proof-checking,

Q = (1.9 x 10-5 + 2.85 x 10-5)2 + (1.9 x 10-5)2

= 2.6 x 10-9.

This is a theoretical figure which makes no allowance for common mode failures.

SC1 SC2

EBS1

EBS2




Headframe and shaft equipment9 Measurement of conveyance deceleration

1 Paragraph 5 of Part 1A reads ‘The retardation of a conveyance should not exceed 1 g in order to minimise risk of injury to persons following application of the brake after an emergency trip. To achieve this in practical terms, the retardation of the rope at the drum should not exceed 16 ft/sec2 (4.9 m/s2) and should preferably be less than 12 ft/sec2 (3.7 m/sec2).’ These limits are based on previous work which has indicated that maximum retardation at a conveyance can be about twice the average retardation at the drum where measurements can conveniently be made. Conveyance retardations have been studied at a number of collieries during both normal winding operations and tests of emergency braking, using an electronic system developed from commercially available units. Paragraph 83 of Part 2A refers. This system has a better overall performance than mechanical systems previously used as it has better frequency response. Results were compared with average drum retardations obtained at the same time using a Kelvin and Hughes cage speed landing recorder.

2 The better frequency response of this electronic equipment permits direct and more accurate recording of frequencies and amplitudes of oscillations. Such records reflect more accurately variations in dynamic load in components such as ropes and suspension gear, and at conveyance attachment points, improving knowledge of service loading and conditions during manriding. Assessment of effects of retardation, or of changes in retardation, on persons standing in various attitudes in a moving conveyance is complex. At present there is insufficient medical evidence available to enable more specific limits than 1 g, including the effects of rate of change of retardation, to be recommended.

3 The equipment used for measuring acceleration or retardation consists of:

(1) a piezo-resistive accelerometer, ± 25 g range, frequency response zero to 750 Hz, output 20 mV/g at 10 volt DC excitation;

(2) a signal conditioner, an in-line signal amplifier and stabilized voltage regulator powered from the internal battery in the recorder; and

(3) a two channel, battery powered, medium speed, pen recorder with a frequency response of zero to 30 Hz for full scale deflection and zero to 120 Hz for small scale deflections.

The accelerometer is bolted to a steel plate using a special mounting stud; and this assembly together with the amplifier can then be bolted or clamped to a suitable rigid part of a conveyance and connected to the recorder in the conveyance. An intrinsically safe version of this equipment using a small tape recorder is being developed.

4 Measurements of retardation have been made in one conveyance at each of 13 shafts during quarterly tests. These were recorded during emergency braking with each conveyance ascending and descending at different positions in the shaft. At some shafts measurements were also made during normal winding with both men and materials. More than 150 measurements were made during emergency brake application and a typical trace which illustrates the duration of peak values is shown in fig 9.1.




Figure 9.1 Record of a conveyance accelerometer trace

5 Results of this study may be summarised as follows:

(1) During emergency braking:

(a) Approximately 95% of records indicated peak retardations of 1 g or less.

(b) Although many results support the premise that drum retardation is usually 50% of conveyance retardation, spread of values showed that there is no simple relationship between the two. It appears that direct measurement of conveyance deceleration is preferable to indirect methods such as measurement at the drum and multiplication by an assumed factor.

(c) In seven of the 150 emergency brake measurements individual peak retardations exceeding 1 g were recorded in conveyances. These peak values ranged from 1.13 g to 1.61 g and their durations above 1 g from 0.1 sec to 0.5 sec. No more conclusions have been drawn at this stage from these isolated values.

(2) During normal winding:

(a) During normal manriding the maximum retardations recorded in 38 measurements were in the range of 0.1 g to 0.4 g.

(b) Measurements made during coal winding at one shaft indicated some misalignment of the rigid guides; and at another shaft, values of over 1 g were recorded as a skip entered receivers at the shaft top owing to uneven receiver profile.

6 It has been demonstrated that direct measurement of conveyance acceleration or retardation using an electronic system is a valuable aid in investigating:

- retardations to which men are subjected during emergency brake application;

- the extent of oscillatory motion following emergency brake applications;

- acceleration and retardation of a conveyance during normal winding;

- the ranges of dynamic load to which suspension gear, ropes and conveyances are subject in service; and

- abnormalities in the condition of shaft, guides and receivers.

+ 1.0 g

- 1.0 g 1 sec

A

B

C

Acceleration zone

Zero acceleration

Braking zone

Conveyance speed at trip 36 ft/sec

Conveyance oscillation




10 Pit bottom buffers

Recoverable buffers (see paragraph 85 of Part 2A)

1 The types examined utilised different principles of energy absorption: flexure of reinforced rubber; hydraulic cushioning; and compression of an elastomer in an enclosure:

(1) Flexure of reinforced rubber. Tests on original versions of these buffers are described in section 22 of Part 1B and later designs using fire resistant compounds have been prepared by a manufacturer and a diagrammatic arrangement is shown in fig 10.1. Results of static and dynamic tests under laboratory conditions (described in this section) have provided fundamental characteristics which were used to predict performances at collieries. Three trial sets installed in men and materials shafts are being monitored and further installations have been made. Commissioning tests made on completion of the trial installations showed that conveyances can be retarded at the anticipated rates. The monitoring is for assessing performance in respect of resistance to fatigue, degree of maintenance and effects of the environment. As the buffers so far developed are apparently satisfactory, the NCB has a programme for installing similar buffers, individually designed, where the accuracy of conveyance registration is adequate. Development continues.

(2) Hydraulic cushioning. Two typical hydraulic buffers were examined, which depend on controlled transfer of fluid; one is shown in fig 10.2. Tests of this buffer (described in this subsection) indicate that conveyances can be retarded satisfactorily but the buffers have not been designed to register conveyances accurately and further investigations will be made into this aspect.

Figure 10.1 Construction of a recoverable buffer (Cable belt type)




(3) Compression of an elastomer. A sketch of a two stage elastomer type of buffer is shown in fig 10.3. The behaviour under compression of a hydrostatically loaded elastomer is used to provide spring and damping effects. The device appears to be suitable for use as a recoverable buffer and a single stage appears to be adequate. Further testing is required to determine whether its performance is affected by repeated loading, deflection and ageing.

When the buffer is subjected to a force the pistons are forced successively through the elastomer causing a decrease in its volume and an increase of pressure. The pistons have specially shaped heads and their relative proportions are such that the bottom piston operates before the top one. The elastomer is pre-stressed in the cylinder so that compression does not occur until predetermined static forces are applied. A characteristic of the design is that the pistons return to their normal extended position after the forces have been removed.

Non-recoverable buffers

2 A wide range of materials and components suitable for use in non-recoverable buffers has been considered including: wooden blocks, wooden packs, thin wall steel cylinders, plastic cylinders, aerated concrete, steel bellows, honeycomb materials, rubber and cork compounds, and steel mesh lattices. Static and dynamic tests have been made on a number of these items to determine their characteristics and results

Air chamber(precharged)

Seconarycylinder

Primarycylinder

Siliconehigh viscosityelastometer

Metering pinto allow transferof oil duringcompression

indicatesdirection of oil flowduring compression

Weight: 160 lb Weight: 114 lb

4” dia4 1/8” dia

4 1/2” dia

4 1/2” dia

5 1/2” dia

47 1 /

2”

14 3 /

4” s

troke

20 5 /

8”

22 1 /

2” s

troke

13 3 /

4”

64 3 /

4”

28 1 /

2”

Figure 10.2 OLEO type 9 buffer. See Fig 10.8 for results of dynamic tests

Figure 10.3 Jarrett Elastometer buffer. See Fig 10.9 for results of dynamic tests




are in this section. The majority of the items had reasonable energy absorbing properties but assessment of results including modes of deformation showed that steel cylinders, as shown in fig 10.4, were the most promising since they fold progressively into a regular shape and use available space more effectively. On this basis, a number of trial installations are being made and a design and selection guide is being produced.

Figure 10.4 Thin wall steel cylinder buffer

Mechanic of arrest

3 A method predicting performance of buffers which takes into account changes in tension in a rope is as follows.

4 Three ways of dynamically loading a buffer are shown in fig 10.5(a). In fig 10.5(a) a mass of weight W moving in a horizontal plane at a velocity V strikes a buffer of varying resistance R as illustrated by its characteristic resistance/compression curve. As the buffer resistance is virtually the only force acting in the plane of motion, the kinetic energy of the weight is converted into strain energy equal to the area under the curve.

5 In fig 10.5 (b) a mass of weight W falls under gravity and strikes a buffer with a velocity V. The net force acting in the direction of motion is the resultant of the weight W downwards and the buffer resistance R upwards. The kinetic energy converted into strain energy is equal to the area between the curve and the horizontal line equivalent to the weight. The area under the weight line represents the change in potential energy as the weight compresses the buffer.

6 In fig 10.5 (c) the weight W is supported by a spring and the weight/spring system is descending at a constant velocity V. On impact the tension T in the spring equals weight W and the resultant force resistance, ie the circumstances are equivalennt to a horizontal impact. After impact the upper end of the spring continues downwards at the same constant velocity and the spring tnsion decreases during arrest and may at some stage reduce to zero. The net force is

Before use

After fullcompression

Crushed cylinder cut away to show construction




then the resultant of the weight and the buffer resistance, ie the circumstances are equivalent to a free fall impact. The kinetic energy converted into a strain energy is equal to the shhaded area under the curve. The spring simulates the elasticity of a winding rope and the rate of transfer of conveyance weight from rope to buffer, ie the rope effect depends on buffer resistance, speed of descent, conveyance weight, and rope length and elasticity.

Figure 10.5 Different methods of loading buffers

7 True circumstances are somewhere between the horizontal and free fall conditions; and it is essential to take rope characteristics into account to determine deceleration and buffer compressions with reasonable accuracy. Theoretical work is proceeding to establish if the weight of a winding rope affects its apparent elasticity in these circumstances.

Test rig for investigating rope effects

8 The theoretical work referred to in paragraphs 3 to 7 has established the

Velocity V

Weight(W)

Weight(W)

Velocity(V)

Velocity V

R

W

W

R

T

Weight(W)

(a) Horizontal condition

Compression

Res

ista

nce

Bufferresistance

(R)

(b) Free fall condition

Compression

Res

ista

nce

(c) Weight/spring system

Compression

Res

ista

nce




necessity of allowing for changes in tension in a winding rope as a conveyance is retarded by buffers. To provide experimental correlation a test rig has been constructed which simulates the elasticity of a winding rope and enables tests to be made at a controlled speed of descent.

9 A schematic diagram of the test rig is shown in fig 10.6. A test weight is suspended from a spring attached to the end of a piston rod of a hydraulic cylinder so that the spring simulates the elasticity of a winding rope. The piston/spring/weight system descends when oil is allowed to flow from the cylinder under control of a proportional flow control valve. A signal equivalent to the required descent velocity is compared with a signal representing the measured velocity of the weight to produce an error signal which forms the input to a compensator in the controller. A conditioned signal is produced by the compensator for activating the flow control valve and determining the rate of descent of the weight. Measurement of velocity is obtained by integrating the output of an accelerometer attached to the weight. Just before impact of the weight on the buffer, when constant descent velocity has been attained, output is switched from the weight accelerometer to one mounted on the piston rod so that the piston rod maintains a constant descent velocity after impact.

10 A mathematical simulation of the test rig has been made by the Control Systems Centre, University of Manchester Institute of Science and Technology (UMIST).* Computerized studies of dynamics and control of the test rig have been carried out and recommendations made with respect to operation of the system.

Tests on fabric reinforced rubber buffers

11 To establish performance characteristics of buffers before installation at colliery trial sites, test units were manufactured having walls of different constructions. Static tests were made to determine their fundamental characteristics and a typical resistance/compression curve is shown in fig 10.7.

Isolatingvalve

Ropesimulator

Testbuffer

Testweight

Flow controlvalve

ControllerAccelerometer

Accelerometer

To sump

Figure 10.6 Schematic diagram of testing for investigating rope effects on buffer

* Full details of these studies are given in UMIST Control Systems Centre Reports, numbers 341 and 362 by B S Bennett.




12 Dynamic performances were investigated using a drop test rig. A weight was dropped from predetermined heights to strike the buffers at known velocities and measurements were made of buffer compressions and retardations of the weight. Maximum forces and compressions recorded for the buffers tested were in close agreement with the static characteristics of some types of buffer but not with others.

Figure 10.7 Resistance/compression curve for buffer (type 3-6-4)

13 Buffers were installed at three trial sites during 1976 and commissioning tests were made to determine impact velocities, conveyance retardations and maximum buffer compressions, with empty cages and with a simulated full man load in one cage. In each case retardations were measured by an accelerometer: signals were fed to a battery powered tape recorder mounted in a cushioned box within the cage. Table 10.1 shows a summary of results for one of the collieries; and predicted values of retardation and compression have been included. Measured decelerations were below 2.5 g and good correlation exists in general with calculated values. With one or two exceptions there is also good accord between measured and calculated deflections; differences between them are being investigated by further theoretical studies and experimental work using the test rig referred to in paragraph 8 and 9.

Tests on buffers other than fabric reinforced rubber buffers

14 Dynamic tests have been made on alternative recoverable and non-recoverable buffer systems using a drop test rig. A weight of 2 tons was dropped from varying heights on the test units and measurements were made of reactive forces, decelerations of the weight and compressions of the units. The effects of different ambient temperatures and non-axial loadings have been investigated. Static tests have also been made to establish fundamental characteristics.

15 Typical test records are shown in figs 10.8 and 10.10 and a summary of results for non-recoverable buffers is given in table 10.2. Only preliminary tests have so far been made on a prototype hydraulic buffer with spring return, similar to the type commonly fitted in lift installations.

8

7

6

5

4

3

2

1

00 2 4 6 8 10

Compression (inches)

Res

ista

nce

(tonf

)

1412 16 18




Deflection

Cage Condition Impact velocity(ft/sec)

Maximum deceleration(g)

Maximum dynamic(in)

Static after test(in)

East Empty 1.8(3.0)4.6(5.0)5.45.86.6(6.5)

1.1(1.5)1.9(1.8)2.21.91.7*(2.1)

1(1.0)2.5(2.8)

-3.0-

(4.8)

0.2

0.6

0.70.70.8

East Man load (3.0)3.8(5.0)5.05.76.4(6.5)

(0.9)1.6(1.2)1.51.61.6(1.2)

(2.5)-

(4.8)---

(8.2)

2.3

2.6-

3.8

West Man load 4.64.8(5.0)(6.5)6.6(7.5)7.5

1.51.7(1.2)(1.2)1.8(1.3)1.6

4.54.0(4.8)(8.2)5.6

(10.8)5.8

2.61.0

3.8

3.3

West Empty (3.0)(5.0)5.06.0(6.5)6.5

(1.5)(1.8)1.71.6(2.1)1.7

(1.0)(2.8)3.73.9(4.8)3.9

0.91.0

1.0

* Braking evident before impact NB: Figures in brackets are calculated values The cage not being tested was always empty




Figure 10.8 Dynamic resistance/compression curves OLEO type 9 buffer

Table 10.2 Summary of typical results for non-recoverable buffers

Description Energy absorptionCapacity (ft tonf)

Compression (as percentage of original height)

Plateau force*(tonf)

Comments on plateau force

Plain thin wall steel cylinder11.45 in diameter24 in high18 gauge

8.9 83 6.3 Can be varied with sheet thickness, keeping height and diameter constant

Perforated thin wall steel cylinder11.45 in diameter24 in high18 gauge

2.9 86 1.9

Plastic cylinderExtruded 9.1 84 6.1

Can be varied as required by prior specification

Wood Pack(Deal)

9.2 67 7.1 Not easily pre-determined by changing structure

*See fig 10.10

00

1

2

3

4

5

6

2 4 6 8

Compression (inches)

Impact velocity: 10 ft/secWeight: 2 tons

CurvesDotted: PredictedFull: Experimental

Res

ista

nce

(tonf

)

10 12 1614




Figure 10.9 Static and dynamic resistance/compression curves - Elastomer buffer

Figure 10.10 Dynamic force/compression characteristics of experimental buffer

11 Control of balances rope loops

1 The four main systems of balance rope loop control are described below and the design principles referred to in paragraph 132 of Part 2A are in paragraph 3 below.

(1) The Baulk System (fig 11.1): a timber baulk is threaded through the loop, and can be designed to break or lift in the event of the loop’s rising.

00

1

2

3

4

5

6

7

8

3 4 6 8

10 ft/sec

Weight: 2 tons

10 ft/sec

10 ft/sec

10 ft/sec

Static

Static

Static

Static

13.6 ft/sec

13.6 ft/sec

13.6

ft/se

c

10 12Compression (inches)

Res

ista

nce

(tonf

)

14 16 18 2220 24

00

2468

1012141618

1 2 3 4 5 6 7Compression in.

Steel cylinderplain wall18 gauge

Forc

e To

nf

8 9 10 11 12 13 140

0

2468

1012141618


Steel cylinderperforated wall

18 gauge

Forc

e To

nf

8 9 10 11 12 13 14

00

2468

1012141618


Plastic cylinder(extruded)

Forc

e To

nf

8 9 10 11 12 13 140

0

2468

1012141618


Wood pack(Deal)

Forc

e To

nf

8 9 10 11 12 13 14

(plateau)

Not

e: A

ll cy

linde

rs a

re v

ente

d

(plateau)

(plateau)(plateau)




(2) The Open Box System (figs 11.2 and 11.3): usually a four sided timber box open at the top and bottom contains the loop and prevents contact between rope and sump structure. The loop is allowed to move horizontally and vertically within the confines of the box and may lift out under overwind conditions. The box may encase the loop or be positioned so that the loop protrudes below it. The sides of the box can be solid or made of slats and, where twin balance ropes are used, a substantial partition is normally fitted between the ropes.

(3) The Restricting Frame system (fig 11.4): a number of substantial timber frames, adequately braced together, encase the rope above the loop and a substantial partition is normally used to separate twin balance ropes.

(4) The Guide Slot or Hole System (fig 11.5): a long narrow timber lined slot is formed to guide both parts of the rope above the loop to prevent twisting; alternatively round or square holes are cut in sump platforms to control individually both parts of the rope in horizontal planes. The slot or holes are usually lined with substantial chamfered timbers and the holes should be large enough to prevent localised wear. This arrangement is often used in conjunction with one of the other systems.

2 Loop pulley system in which a balance rope passes around a weighted pulley, usually mounted in a frame and free to slide in vertical guides, are not recommended because of operational difficulties and potential hazards.

3 A balance rope is selected to be compatible with conditions of use, but in view of the possibility of twisting of the loop and the different behaviour of ropes of the same construction, some kind of loop control system is necessary on all installations, whether equipped with round or flat balance ropes. The following principles are considered good practice:

(1) Movement of a balance rope loop should preferably be restricted by one of the four preceding schemes.

Balance rope

Monitor

Monitor

Coveyance crs

Open boardedbox

A A

B B

Baulk retaining guides

Timber positioning slat(nailed to guides)

Monitor

Balance rope is shown stationary

Balance ropeis shownstationary

Max twistangle shouldnot exceed 26o

Section B - B

Section A - A

Figure 11.1 Balance rope control (Baulk system)

Figure 11.2 Balance rope control (Open box system)




(2) The distance between the bottom of a box, lowest frame, guide slot or hole, and the bottom of the balance rope loop should be such that a kink or twist cannot develop in the rope.

(3) Where a frame, guide slot or hole cannot be arranged to prevent a loop from running in contact with shaft furnishings, a box should be installed.

(4) Any control box should have sides of continuous timber or of wooden planks between which gaps are not greater than 12 in (0.3 m).

(5) Where twin balance ropes are fitted, each rope should be accommodated in its own box or frames, or both ropes in a common box or common frames divided by a substantial partition extending at least to the bottom of the loops (fig 11.3 and 11.4).

(6) Insides of boxes should be smooth with no protruding edge or bolthead etc.

MonitorMonitor

Monitor

Coveyance crs

Open boardedbox Timber

frames

Tripswitch Tripswitch

Substantialtimber

partition

Twinbalanceropes

A A

A

A

B B

Balance ropeshownstationary

Balance ropeshown

stationary Max twistangle shouldnot exceed 26o

Section B - B Section A - A

Section A - A

Figure 11.3 Balance rope control (Open box system)

Monitor

Guideholes

Figure 11.4 Balance rope control (Restricting frame system)

Figure 11.5 Balance rope control (Guide hole system)




(7) The longer horizontal dimension of a box or frames should allow a balance rope to form its natural elongated loop without making contact with the ends of the box or frames when winding at full speed. The shorter dimension should prevent the angle of movement, based on normal conveyance centres, from exceeding 1 in 2, i.e. 26º (0.46 rad): see figs 11.2 and 11.3.

(8) Where timber baulks are fitted through a loop to prevent it from twisting, the baulks should be arranged to lift should the loop rise; and any vertical restraining forces on baulks should be reasonably small.

(9) There should be a clear space of at least 4 ft (1.2 m) kept free from any debris, water or obstruction, below the bottom of the loop of a stationary balance rope.

(10) The bending ratio of a balance rope loop, based on distance between conveyance centres to rope diameter, should not normally be less than 25 to 1 or that agreed with the rope manufacturer.

(11) There should be sufficient vertical distance between a balance rope loop and any fixed obstruction passing through it, to ensure that lifting of the loop is not restricted in the event of overwind of a conveyance to the ultimate position or during capping or other operation.

(12) Rope swivels of the rolling bearing type should be fitted to round balance ropes except where experience has shown that ropes operate successfully without swivels.

12 Monitoring of balance rope loops

1 Monitoring of a balance rope loop, as referred to in paragraph 134 of Part 2A, may be achieved by a wire or hinged lever through the loop. A wire system may be designed to fail to safety, either by use of a normally energised relay circuit with current passing through the stretched wire and a remote diode, or by switches held in the closed position by taut wire. A hinged lever type of device, also designed to fail to safety, may not be so prone to spurious tripping or damage: and, provided a latch type tripping relay is used, the lever can be self resetting but this may not be an advantage in practice.

2 Arrangements suitable for conditions in pit bottom sumps include:

(1) a hinged tubular lever of 3 in to 4 in (75 mm to 100 mm) diameter; and

(2) a trip wire protected against falling debris by a light weight beam or tube that is free to lift or hinge out of the path of a lifting balance rope loop.

Electrical apparatus used in conjunction with this equipment should also be protected against falling debris.

13 Shaft signalling systems

1 This section amplifies requirements and means of achieving the ameliorations referred to in Part 2A, paragraphs 157 to 160.

2 For many years Regulation 20(3) of the Coal and Other Mines (Electricity) Regulations 1956 prohibited the earthing of underground signalling systems, and shaft signalling systems followed this practice. This has the disadvantage that a




single earth fault is not self revealing and an additional earth fault might cause serious malfunction. It is therefore probable that the integrity of shaft signalling systems would be improved by connecting them to earth via a suitable monitoring device. Such a monitoring device should give warning of the first earth fault but not cut off the power supply. Earth fault monitoring can be even more important in the case of modern complex signalling systems. Modern underground power system practice precludes use of concentric cables and incorporates instantaneous earth fault protection; this precedent favours adoption of earth fault monitoring on signalling systems.

3 Emergency stop systems should fail to safety; a normally energised circuit, designed to British Standard 3101: 1959, with duplicated independent relay channels, is an example of a system of this type. The use of screened cables with an earthed suitably monitored system could further improve the integrity of the circuit; but there may be practical difficulties in executing this. The button for signalling emergency stop should be of the unshrouded stop-lock type, and mushroom headed to assist operation. It is preferable that indication of emergency stop should only be displayed in the winding engine house and at the initiating level. Although this has the disadvantage that a person at another level may be unaware of the reason for a stoppage, this situation should not cause danger and he can seek information by telephone. Indication of emergency stop at other levels might led a person there to assume that it is safe to work in a position where movement of a conveyance could cause danger.

4 Existing mechanically driven cancelling devices do not respond efficiently at slow speed. This can lead to use of the emergency stop button rather than the normal signal, as the cancellor may not have moved far enough to cause stop to be indicated. A new type of cancelling device capable of responding efficiently at slow speed or after short travel of a winding engine (for example an electronic pulsing device) could probably be designed to provide much more efficient cancellation of signals.

5 All signalling system should include a signal incomplete warning feature to ensure that the winding engineman is informed if the full and correct combination of signals has not been received at the engine house; eg raise with lower, raise steadily with lower steadily, or first man in with lower or lower steadily. As a further precaution this signal incomplete protection could be included in the brake lock circuit.

6 When the signal three indicating men is transmitted from any level, this signal should remain displayed on the indicator at that level and on the appropriate level indicator in the winding engine house, until a subsequent action signal has been sent from the same level and the next normal movement of the conveyance is completed. If an emergency stop signal is given during a wind, the men indication should remain displayed until that wind is completed.

7 There should be provision of interlocking at all levels where assistant onsetters or assistant banksmen are employed. This method provides assurance for the onsetter, banksman and assistant and a ready signal should only be cancelled by the signal cancellor or an emergency stop signal. The assistants’ signalling positions should be provided with full emergency stop features (cleared only by resetting and subsequent ready signal from that position) and indication of action or emergency stop signals from the onsetter or banksman.

8 Although the assistants’ signal is usually inter-locked into the onsetter’s and banksman’s signalling circuit, it is doubtful whether this feature should be extended to any of the shaftside protective devices. If an alarm is insufficient protection it is




preferable that these devices should be interlocked with other apparatus such as the winding engine safety circuit or brake lock; but the method of achieving the interlock should comply with the recommendation in paragraph 90(9) of Part 1A. For example, vibration of a shaftside door should not be able to split an onsetter’s signal of three so that the winding engineman receives a raise signal of one.

9 Shaft signalling systems emergency power supply comprises two batteries, one in service and the other on standby or charge. This system has the weakness that failure of the service battery at, or shortly after change-over, could result in complete loss of the power supply. Whether it is considered that a more secure power supply could be achieved by use of a single battery on a floating charge, it is essential that the state of the battery should be continuously monitored. The type of battery would moreover need careful selection: for example, lead acid Planté type or alkaline cells would be suitable.

10 Signal buttons should be shrouded to prevent accidental operation and signalling stations sited to minimise risk of accidental damage or interference, particularly where persons congregate. In some cases dirt or moisture can interfere with apparatus and a manufacturer may need relevant instructions from the user. Small heaters, even filament lamps, can help to prevent condensation in signalling units. Illuminated signal units, particularly those which are intended to provide information to persons entering a conveyance, should be carefully sited so as to be easily seen.




Maintenance, testing and training14 Maintenance procedures: statutory report books

Prescribed books specifically for reporting statutory examinations and tests of winding installations in Great Britain, referred to in paragraphs 170 of Part 2A, are as follows:

M & Q Form No 275 Reports of examinations of shafts, staple-pits and unwalkable outlets through which persons are carried.

M & Q Form No 277 Reports of examinations of winding ropes.

M& Q Form No 278 Reports of tests of automatic contrivance to prevent over-winding

M & Q Form No 279 Reports of thorough examinations of apparatus provided for attaching to the rope a cage etc. in a shaft, staple-pit or unwalkable outlet.

M & Q Form No 281 Reports of examinations of lengths of rope cut off when recapping.

15 Maintenance: Safe working procedures and control

General factors

1 Some of the general factors, as referred to in paragraph 173 of Part 2A, which should be considered when preparing plans for examination and maintenance work on headframe and shaft equipment are:

(1) There should be safe and, as far as practicable, unobstructed access to equipment and structures.

(2) For some shaft work, bridging platforms on conveyances are necessary; these platforms should be of adequate strength, each firmly attached to the conveyance and capable of being secured in the withdrawn position so that conveyances may move freely through the shaft. Anchorage points for safety harness should be available and handrails may be necessary.

(3) Although it may be necessary to use a conveyance as a working platform in certain cases, permanent substantial ladders or stairways, platforms or gantries set at convenient levels, with handrails, ladder hoops or anchorage points for safety harness should, where practicable, be provided in headframes and winding engine towers at all positions where routine maintenance has to be carried out. Access to external parts of headframes and ancillary equipment is aided by use of purposely built mobile inspection platforms. Where regular access to external parts of winding engine towers is required, the installation of power operated suspended scaffolds should be considered.

(4) When temporary access arrangements have to be provided for major work, properly constructed and secured temporary platforms should be used.

(5) Access to a shaft sump is required for examination and maintenance of guides, tension weights, balance rope loop control systems, arrestors, bumping beams,




spillage hoppers, clearance conveyors etc. This equipment should be capable of being readily examined from permanent substantial ladders or stairways, platforms or gantries set at convenient levels, with handrails, ladder hoops or anchorage points for safety harness. Mineral spillage should not be allowed to accumulate in sumps to such an extent that operation and condition of equipment is adversely affected. Where a sump is used as part of a catchment for mine water, the permissible high water level should be established well below any apparatus. In establishing this level, the effect of any water likely to be discharged into a sump during gravity winding should be taken into account; and allowance for this water should be catered for in the emergency egress scheme for the mine as pumping facilities may not be available.

(6) General lighting should normally be installed to illuminate all permanent access stairways, platforms and gantries in the headframe and sump, and the switch locations identified. It may be necessary to provide emergency lighting in and around a headframe and shaft mouth, preferably from a standby generator.

(7) Work within a shaft can be more satisfactorily carried out where adequate lighting allows the job to be clearly viewed.

(8) It should be the responsibility of the person carrying out maintenance or, where there is more than one person, the responsibility of the supervisor to inform the winding engineman, the banksman and, where necessary, the onsetter when work is to commence, and to take steps, when necessary, to prevent movement of the winding engine and to immobilise any other associated equipment.

(9) Where separate individuals or groups have to apply interdependent safety precautions or procedures, consideration should be given to applying the principles of a permit to work system.

(10) Speech communication facilities are desirable for maintenance personnel when they are carrying out such tasks as rope changing, headframe pulley changing etc., because of distances involved. It is considered that a loud speaking telephone system of a type recommended in paragraph 94(1) of Part 1A could be used to aid special tasks on headframes and in other working places which are directly affected by winding engine operations.

(11) Work in shafts should only be undertaken by persons having had or receiving the necessary training and should be supervised by competent shaftsmen.

(12) When men are working in a shaft, precautions should be taken to prevent injury from falling objects. Work should not be carried out simultaneously at different levels in a headframe, shaft or sump where there is a danger of work at one level creating a hazard for men working at a different level.

(13) Adequate precautions should be taken against dangers which can arise when using welding and flame cutting apparatus: the NBC has issued mandatory instructions covering the use of such equipment at its mines. Where the apparatus is to be used in a shaft, it is particularly important that correct procedures be followed, and the mine manager should issue to the person in charge of operations a statement of the conditions which he imposes as well as a certificate of authorisation. In the case of a safety lamp mine in Great Britain. Section 67(1)(c) of the Mines and Quarries Act 1954 permits such apparatus to be used below ground where the authority in writing of a mines inspector has been obtained, and the inspector may impose conditions of use.




(14) Power packs which convert liquid nitrogen to gas under pressure are presently being tested in several coal mines to provide power for operating conventional pneumatic hand held tools. Such power sources mounted on conveyances may facilitate maintenance and installation work in shafts. They may also be used to power pneumatically driven generators for portable electric lighting in shafts.

(15) Materials should not be stored or allowed to accumulate so that they impede access to places requiring to be examined.

(16) Combustible material should not be stored in winding engine house basements. Basements are often used for storage of shaftsmen’s tools; these stores should be kept tidy and fires should not be used for heating them.

Safety harness

2 The NCB has issued a specification for design and performance of safety harness for use at collieries. Safety harness should be worn by any person when at work where there is a danger of falling from a height; in particular, it should be worn unless the person is otherwise adequately protected against falling during:

(1) all work in shafts including inspections;

(2) maintenance work at a shaft side requiring removal of safety fencing; and

(3) work on headframes and in sumps or measuring pockets at positions where fenced platforms are not provided and a person could fall for a distance of more than 6 ft 6 in (2 m).

3 Issue and storage Sufficient safety harnesses should be available at a mine for use by persons who may need them. A person should be appointed to look after harnesses which should be properly stored in a ventilated place away from steam pipes or other direct sources of heat. During storage no part of the equipment should be subjected to unnecessary strain or pressure and it should be kept free from contact with sharp objects, corrosive substances and other possible causes of damage. Immediately after use harness should be returned to its place of storage; but if it is wet it should be dried out without means of direct heart, at or near normal room temperature and where necessary cleaned ready for further use. A person required to wear safety harness in the course of his regular duties should be provided with a personal issue which fits properly and which should not have unauthorised modifications. Where persons not on the staff of a mine have a personal harness, they should be responsible for ensuring that it is properly maintained and stored.

4 Use The wearer should ensure that harness is properly anchored and that all snap hooks or similar fastenings are locked. The anchorage should be at least as strong as the harness itself taking into account the least favourable direction of pull which can be applied by the harness. Anchorage points should be carefully selected: for example, they should not be on conveyance suspension gear above a detaching hook or such that there may be relative movement between the place on which the person is standing and the anchorage.

5 Examination Each time before wearing safety harness, the user should make a visual examination to ensure that it is serviceable. Every set of harness issued for use, whether it has been used or not, should be thoroughly examined at regular intervals, probably monthly, by a suitably trained and authorised person who is not the normal user. During this examination, particular attention should be paid to detection of the following types of defect in:




webbing: cuts, tears, or abrasions; undue stretching; deterioration; damage due to heat, acids or other corrosive substances;

sewing: broken, cut or worn threads;

hooks: damage, wear, corrosion, distortion or faulty springs; and in

chains: damage, wear or corrosion

When any defect is found during examination, harness should be immediately withdrawn from service and the matter reported to the mine mechanical engineer or other nominated person. Withdrawn harness should not be put back into service until the necessary repairs have been effected and the harness cleared by the mine mechanical engineer or other nominated person. When a harness is discarded because of arrestment, irreparable damage, or other cause, it should be destroyed.

6 Reports and records A certificate should be issued by a manufacturer for each harness when new and after he carries out any examination, service or repair. These certificates should be retained at the mine. Each harness should be marked with a serial number for identification; and a history card or sheet, bearing the serial number and containing the following information, should be kept for each harness:

- summary of examinations and reports;

- details of manufacturers’ certificates issued when new and after each examination and service; and

- records of withdrawal for repair with details of the reasons and repairs.

16 Maintenance of foundations, buildings, structures and shaft linings

Examinations of foundations, buildings and structures

1 Referring to paragraphs 177 to 180 of Part 2A, points to be observed during routine examinations are:

(1) Cleanliness should be maintained to a standard which minimizes hazards such as stumbling and slipping and allows structural imperfections to be readily observed.

(2) Some deterioration will be found in structures: this may not affect safety but, at successive examinations, evidence of progressive deterioration should be looked for such as spalling of brickwork, deposits of mortar, extension of cracks in concrete and masonry, and corrosion of steelwork. Reporting systems should be such that the rate of progress of deterioration at critical points can be assessed by reference to previous reports, and remedial work put in hand well before any dangerous situation can develop.

(3) Any cause of damp in structures and foundations should be traced and reported. Drain holes in steel structures should be cleaned out.

(4) Relative movement between winding engine foundations and bed plates should be reported. With steam engines, movement cannot always be eliminated, but checks should be made to ensure that it does not become excessive.




(5) Movement between headframe members, including foundations and base plates, can sometimes be detected by putting a finger on the joint during winding even if there is no visible indication of movement. Excessive deflection can sometimes be detected by sight; any such deflections should be recorded and their causes investigated.

(6) Details of the examination, including identification of the selected parts, and any significant deterioration should be recorded; other selected parts should subsequently be examined to ensure that the whole structure is inspected within a reasonable period of time.

2 Additional checks to be made during periodic examinations by mine mechanical engineers and civil engineers include:

(1) The history of cracks and other imperfections in structures being examined should be considered. The reason for deterioration should be sought and if necessary specialists should be consulted. Effects of testing such as quarterly brake tests should be taken into account where it is suspected that such tests may contribute to deterioration.

(2) Brickwork should be probed to determine the depth of any imperfections that appear to be increasing.

(3) Recurrent damage to items such as access staircases, doors, handrails etc. may indicate the need for redesign to cater for more severe usage.

(4) Selected parts of steelwork should be cleared of corrosion and the thickness of sound steel then compared with the original thickness, so that its adequacy can be assessed.

(5) A torque wrench or other measuring device should be used to check the security of selected bolts and of all bolts at joints where relative movement is suspected. Selected rivets should be hammer tested.

(6) Welds should be visually checked, and causes of cracks and fractures further investigated.

(7) Reports should be made at the time of the examination and action initiated for the replacement of loose or missing parts or fastenings together with any other repairs needed.

Examination of shaft linings

3 Referring again to paragraphs 177 to 180 of Part 2A, the following notes are for guidance of persons examining shaft linings and fig 16.1 illustrates a suitable form of shaft examination report:

(1) Before a detailed examination of a shaft lining is carried out, accumulations of dirt should be removed.

(2) Accumulations of salt should normally be removed. Although water present in a shaft my not have ill effect, its evaporation may leave salt deposits with high local concentrations sufficient to attack the shaft lining and its furnishings. Salt deposits have been known to retain shaft linings in a wet state but in good condition: their removal accelerated evaporation by the ventilation and caused the concrete linings to become seriously affected at these points. If salt is removed, therefore, parts of the shaft lining previously covered should be regularly and carefully examined.



Figure 16.1 (Sheet 1) Maintenance: Example of shaft examination report




(3) Cracks in metal tubbing should be marked at their ends to enable the rate of propagation to be determined, while ceramic or other tell-tale indicators can be similarly used for cracks in brickwork or concrete.

(4) Deterioration of shaft linings may result from lack of adequate back filling, either because the original filling, frequently ashes, has been washed out, or the strata have disintegrated and been washed out in the vicinity of coal seams or soft ground. In older shafts, voids created may lead to migration of water and build up of pressure in sections below the original water bearing zones. If defects appear in a shaft lining, reference to sinking records may be useful when information relating to the strata is required to aid remedial measures.

(5) If a shaft lining other than timber is damaged, it may be necessary to make a hole in it large enough to allow the ground behind to be examined to determine the cause; but great care should be exercised in making such an access as water under very high pressure may be present. In a concrete shaft, a suitable method is to bore part of the way through the lining and in this hole to fix securely a pipe fitted with a cock. Boring can then be completed through the cock: if water is not encountered, the hole may be enlarged; if it is found, the cock can be closed and the water subsequently run off under control. When such water has run until pressure appears to have dissipated, the hole should not be enlarged until another similar boring has been made a short distance away. If flow at the original hole had only diminished owing to partial blockage, the water can then be safely tapped again before the holes are enlarged.

(6) Timber linings through competent strata have been known to give long service, but those subject to loading from wet backfill should be continually inspected to prevent failure from rot. Symptoms of decay such as fungus growth and softening should always be investigated as the condition can sometimes be remedied at an early stage simply by injection of the timber with fungicide and provision of additional support. Complete failure of any member in a timber lining is most serious as it can lead to a chain reaction causing a sudden obstruction in a shaft.

(7) As a means of identifying locations in a shaft, marks should be made either on the wall or on buntons and related references should be printed on the shaft inspection report form (fig 16.1). Where magnetic marking of guide ropes as referred to in section 5 is adopted in connection with conveyance position monitoring, this may prove to be useful for accurate identification of places in a shaft. Photography can be a useful means of recording shaft defects which cannot otherwise be as well described.

(8) Any brackets or supports attached to shaft linings should be regularly examined.

Notes of guidance on examinations of reinforced concrete

4 The following additional notes are for the guidance of persons examining reinforced concrete used in structures and, where applicable, in shaft linings:

(1) The object of examination is to obtain appraisal of the condition of a member and to begin repairs before its strength is significantly reduced. Sound concrete usually indicates a sound member: it is uniform and often shows the marks of the original form work. Porosity is indicated by spalling or fretting of surfaces and permeability will be increased by cracking. Corroded steel reinforcement can burst concrete as it expands and an iron stain may appear on the surface if free water is present. When concrete fails to protect concealed steel from progressive corrosion, members may be seriously weakened even though their original strength was adequate. Design drawings are necessary to establish the




original particulars of embedded steel although its location can often be inferred. The information obtainable from examination methods such as the rebound hammer or induction tracing and radiography, is not easily interpreted and these methods should not be relied upon in routine examinations.

(2) Examination of structures subject to hydraulic or other pressure, for example water lodges, shaft collars, retaining walls, shaft linings and shaft bunkers, must be particularly thorough as failure of any part could lead to rapid failure of the whole. The procedure should be to note soundness of surface, presence of cracks and any leakage; to mark the full length of any cracks; to determine if possible the location of steel reinforcement and appraise any cracking in relation to this; to estimate strength of the structure in relation to the load carried; and to examine the structure more closely by the following methods:

- Cleaning down and, where applicable, emptying to facilitate proper examination. The structure should be kept under observation during emptying and cleaning, so that indication of its true condition such as water draining from cracks or cavities can be observed. The size of any such cavities and cracks should be estimated by probing and if necessary blowing out loose material with compressed air.

- Removing concrete cover from concealed reinforcing bars with hand tools in selected areas subject to corrosion. Where it appears that corrosion is likely to be uniform over an area, removal of concrete in the vicinity of highly stressed parts of critical members should be avoided.

- Recording the more obvious signs of deterioration, staining and spalling, noting particularly where they are concentrated in critical areas

- Monitoring movement and checking against acceptable limits.

(3) Examination of other reinforced concrete structures should be similarly carried out as far as is relevant. Because excessive deflection is an early sign of distress, monitoring of movement is a useful first procedure for examination of such structures.

17 Maintenance of equipment in towers, headframes and sumps

1 Some aspects of maintenance of equipment in towers, headframes and sumps, are discussed in paragraphs 181 to 184 of Part 2A. Other matters are elaborated below.

Headframes pulleys, and their shafts and bearings

2 Pulleys and their shafts should be subjected to routine non-destructive testing as outlined in section 29. Pulley groove profiles should be regularly and systematically checked; this subject is discussed in more detail in section 18. Evidence suggests that the wear rate in some fabricated pulley grooves may be greater than was previously experienced with cast iron pulleys. If this is so, the adoption of alternative materials for pulley rims or the use of inserts may need to be considered. Performance and reliability of both shell type bearings and of grease lubricated, self-aligning roller bearings have proved to be generally satisfactory in service. Effective maintenance of headframe pulleys, shafts and bearings depends to a large extent on a realistic assessment of the requirements of each installation, taking into account details of design and operating conditions. In Great Britain, the statutory examination of headframe pulleys, their shafts and bearings at intervals




not exceeding 24 hours has proved sufficient for a routine check on their condition and security. More detailed examinations should be made at appropriate intervals based on experience, to include: comparison of internal and external rim profiles of pulleys with the profiles when new; wear and condition of bearings and shaft journals; hammer test of spokes in cast pulleys; examination of welds in fabricated pulleys; and a check on security of joint bolts and hoop rings. Examination and maintenance of headframe pulley shafts and bearing is facilitated where proper provision is made for lifting. If jacks are to be used for lifting, purposely designed jacking points should be incorporated in the headframe structure. Adequate platform area should be provided around bearings to facilitate dismantling and reassembly in a safe manner.

Overwind safety catch gear

3 Traditional types of safety catch assembly contain a number of individual catch pawls, hitherto usually of the gravity returned type, of which only two directly opposed are needed to support a conveyance after an overwind. At downcast shafts this gear is often exposed to the elements and at upcast shafts is likely to be affected by condensation. Such conditions may produce rust and, particularly where skip winding takes place, accumulations of dust may cause catches to seize. For the purpose of inspection, headframe and tower mounted overwind safety catches should be capable of being operated manually, or by simple hand operated jacks, from suitable platforms so that persons operating them can see that each pawl works correctly. Where safety catches are mounted on conveyances, their arrangement should be such that correct operation of each pawl can also be readily checked. Ease of access, cleanliness and adequate lubrication where required, are the main essentials for maintaining overwind safety catch gear in effective working order. Examinations are required by regulations to be carried out at intervals not exceeding 24 hours. At periodic intervals the following additional procedures should be implemented:

(1) Racks and catch pawls fitted to conveyances or in headframes or towers should be subjected to detailed examination for security of fixing, sign of damage or general deterioration. Any debris which might inhibit engagement of pawls with racks should be removed.

(2) Each set of safety catches should be physically tested to check that the return of each pawl is unimpaired. Any dirt or other debris should be removed. In freezing weather it may be necessary to take additional precautions at downcast shafts.

(3) At specified intervals each set of catch gear should be thoroughly cleaned, overhauled and lubricated where appropriate.

Conveyance arrestor gear for friction winding installations

4 Conveyance arrestors and bumping beams of friction winding installations only come into use in exceptional cases of overwind. Examinations at intervals not exceeding 24 hours are required in Great Britain. In addition, arrestor gear should be periodically cleaned and examined in detail, measurements taken of critical dimensions and, where appropriate, other necessary tests and examinations should be made to indicate that original design standards are maintained. The effectiveness of timber arrestor gear depends on the quality of the timber and the maintenance of correct dimensions. All timbers should be securely bolted to their supporting steelwork and any which are excessively warped or split should be replaced. For all counterweight systems, there should be routine procedures to ensure that the relative positions of conveyances and counterweights to arrestors are maintained,




taking account of rope stretch and following rope changing or capping operations. In cases of arrestors which incorporate loose frames moved by conveyances, these frames should also be regularly checked to ensure that they are correctly located on their arrestors. Guidance on these relative positions is included in paragraphs 79 and 81 of Part 2A.

Receiver guides

5 Maintenance of correct running clearances between conveyances and receiver guides, and regular lubrication is essential. Damage to receiver guides is usually caused by excessive impact when conveyances enter them. Care should be taken in design to ensure that receiver guides are sufficiently robust; and that lead in angles and clearances between conveyances and rigid guides are such that impact forces are reduced to a minimum. In a rope guided system it is necessary to establish and maintain correct alignment of rope guides and receiver guides. Maximum and minimum clearances and frequency of measurement should be specified for each installation, and included in the manager’s scheme for the mine. Routine maintenance should be scheduled to ensure that fixings of receiver guides are secure. Periodically, alignment of each complete guide system should be thoroughly checked.

18 Maintenance of ropes in winding installations

Winding ropes

1 In addition to the statutory requirement referred to in paragraph 185 of Part 2A, regulations in Great Britain require that provision be made for the examination at intervals not exceeding 30 days of every rope used for carrying persons or loads through a shaft, staple pit or unwalkable outlet. Each rope has to be thoroughly cleaned at all places particularly liable to deterioration and at other places not more than 300 ft (90 m) apart throughout its length; and, at each of these places, after cleaning, examination has to be made of the circumference and surface condition of the rope and for any fractures of the wires. To comply with regulations, winding ropes in Great Britain are moreover recapped within periods of six months, and the length of rope cut off with each capping is forthwith opened up and its internal condition examined by a competent person appointed for the purpose. The combination of regular and careful examination over the whole length of each winding rope and detailed examination of capping samples has proved over many years to be a sound basis for assessing the continuing fitness for service of drum winding ropes. When friction winding ropes are recapped, the amount of rope cut off is normally kept to the minimum allowed and the whole of the length cut off is consequently within the capping. It is therefore not practicable to strip and examine a sample or to carry out tests on individual wires, so that the rope condition has to be assessed from routine external examination. This has proved to be effective as friction winding ropes complete their statutory life of two years or are removed before deterioration becomes severe.

2 Correct capping of winding ropes is essential for safe operation and is achieved by employment of thoroughly trained personnel, effective supervision of work and examination of the condition of white metal cones, if these are used, after service. When examining a cone after it has been pressed out of a socket, it should be visually checked to ascertain that white metal had penetrated fully through to the neck of the socket, and to check that the surface of the cone is free from serious blemishes caused by incorrect temperature of the socket or white metal during capping; sufficient white metal should be removed to check that the rope had been located centrally in the socket and so that the serving can be examined. Any deviation from the highest standard should be noted and necessary action taken.




3 Winding ropes are occasionally damaged when wear in headframe pulleys results in their being pinched in pulley grooves: this has been known to lead to distortion or waviness in locked coil ropes or broken wires in stranded ropes. For new installations the groove radius should normally be at least 7.5% greater than the nominal rope radius. Before any rope is installed, and regularly thereafter, it is important that pulley grooves be gauged and, when necessary trimmed to provide effective seating and adequate side clearance for the rope; account should be taken of rope manufacturing tolerances, fleet angles, changes in shape of rope cross section under load, and wear. For similar reasons it is prudent to check grooves of drums of winding engines against rope size before a new rope is installed. This applies particularly to scrolls on bi-cylindro conical drums but it is unusual for any drum barrel to wear sufficiently to require machining.

4 Multi-rope friction winding installations in Great Britain operate with winding ropes directly connected through suspension gear to conveyances and not through any form of compensating gear. Experience has shown that it is necessary to keep circumferences of grooves in rope treads in a driving drum as near as possible the same, otherwise excessive differences in rope tension may be produced which can cause distortion or broken wires in one or more of the winding ropes. Most friction winding engine have groove machining equipment installed and grooves can be kept in good order by regularly checking and trimming as required. There are several methods for checking tread circumference and two are outlined in paragraphs 24 to 34. Provided care is taken to establish sensibly equal rope lengths and tread diameters when ropes are installed, the difference between wear of treads is minimized and it is often possible to avoid need for trimming grooves during the life of a set of ropes. It is however necessary to keep grooves clear of deposit from ropes. Some twin rope ground mounted friction winding engines have spare grooves cut in the treads so that, when grooves in use become worn, the ropes are moved to the spare grooves and the originals trimmed when convenient. With such an arrangement, if lubricant exudes from the ropes, they can be moved into clean grooves and the contaminated grooves then cleaned.

Balance ropes

5 Regulations in Great Britain do not require specific examinations of balance ropes other than at intervals not exceeding 24 hours. It is however considered that they should be periodically cleaned and examined at selected places throughout their length and that these examinations should be included in the manager’s scheme for the mine.

6 There have been instances of corrosion and physical damage which have led to failure of balance ropes and these incidents have highlighted the importance of regular and thorough examination and lubrication, particularly when ropes are operating in wet and corrosive conditions. Water in a shaft sump should be kept clear of a balance rope loop and debris should not be allowed to accumulate so as to impede running of a rope. Proper access and adequate lighting should be provided if examination and lubrication of balance ropes and their attachments are to be effectively carried out. It is also advisable that onsetters should, where practicable, keep balance ropes under observation during normal winding so that any unusual movement may be noted and the cause investigated. Control and monitoring of balance rope loops is discussed in paragraphs 131 to 137 of Part 2A.

Guide and rubbing ropes

7 In Great Britain regulations require examination of ropes forming part of winding installations at intervals not exceeding 24 hours. Guide ropes should in addition be periodically examined to ascertain extent of wear and general condition. They




should be cleaned, examined and measured at all positions most liable to deterioration and at other selected positions along their length including those sections above the top landing and below the bottom landing. Starting points for successive series of examinations may be varied in order to obtain a general assessment of the whole length of each rope. The interval between these examinations will depend on operating and shaft conditions but should not exceed 12 months. When measuring a rope particular note should be taken of uneven wear, and its effect taken into account when assessing strength of a rope. A typical NCB inspection report form for guide or rubbing ropes is shown in fig 18.1 and a related form for assessment of strength in fig 18.2. For a deep shaft, more than one sheet such as fig 18.1 would be required.

8 Guide and rubbing ropes tend to wear unevenly owing to rubbing action of conveyance shoes at positions where lateral movement is greatest such as at a fan drift, entrances to receiver guides, conveyance meetings and bottom landings. Where uneven wear occurs it is usual practice to rotate guide ropes at intervals in order to equalise it; and spherically seated suspension sockets, suitably lubricated, facilitate this. To minimize the effect of fatigue of a guide rope at a point where vibration is arrested under a capping or gland, the ropes should be lifted at appropriate intervals through a distance of not less than one and one half times the length within the capping or gland and the termination remade. Where guide ropes pass between baulks, beams or platforms below the lowest entrance into a shaft, as referred to in paragraph 115 of Part 2A, they should be kept liberally coated with anti-corrosive grease.

9 Means of tensioning guide ropes are described in paragraph 116 of Part 2A. The most satisfactory way of tensioning guide and rubbing ropes is by means of weights in shaft sumps but cases have occurred where weights and their supporting rods have become bonded together owing to corrosion. Rust forming between individual weights in close contact can force them apart, bending rods; in two cases, cracks propagated slowly across the rods until they broke. The development of such a condition may not be readily apparent before failure occurs and persons examining the equipment should be made aware of the possibility of this type of failure, which may be indicated by bending of the rod. In shafts subjected to corrosive conditions, a liberal amount of anti-corrosive grease should be applied during installation between weights and to weight rods. Although not preferred for permanent installations, where spring tensioners have to be employed, tension indicating devices should be regularly inspected and adjustments made as necessary.




Figure 18.1 (Sh




Figure 18.2 NCB guide and rubbing rope inspection form

Testing of ropes

10 Tests made using accelerometers mounted in conveyances can help to identify magnitudes and sources of kinetic loadings in winding ropes. From an analysis of accelerometer records it may be possible to suggest a means of reducing the stresses imposed on winding ropes and their attachments. The subject is further discussed in section 9.

11 When drum winding ropes are recapped by the NCB, part of a rope cut off is immediately opened up for examination at the mine and about 3 ft (1 m) forwarded to a rope test centre. A number of centres have specifically been set up to inspect




and test new ropes, capping samples and discarded ropes. It is not general practice to test guide ropes. Testing of balance ropes is limited to occasional tests on new or discarded ropes as their recapping is not a routine. Tests of winding rope samples are made on random selections of wires from each layer or strand, and comprise reverse bending, torsion and tensile tests. When capping samples from friction winding ropes are available for test, they are usually not much longer than 6 in (150 mm) and so only reverse bending and tensile tests can be made because longer specimens are necessary for torsion tests. A typical rope test certificate is shown in fig 18.3.

Figure 18.3 Rope test certificate




Figure 18.3 Rope test certificate (continued)

12 Non-destructive testing (NDT) of wire ropes in service by means of instruments using magnetic induction techniques has been under investigation in many countries during the last thirty years. In several countries these instruments are now in use for testing selected stranded winding ropes in service and in at least two countries their use on some stranded winding ropes is now prescribed by regulations. Taking account of experience with non-destructive testing of winding ropes in other countries, although operating conditions and the extent of use of locked coil ropes are not necessarily similar, it is considered that non-destructive testing might augment present methods of assessing continuing fitness for service of ropes in Great Britain. Information gained from this form of testing may moreover lead to a review of criteria on which the period of use of winding ropes is based.




13 There are basically two types of NDT instrument using magnetic induction techniques for wire ropes available today, the alternating current type and the direct current or permanent magnet type.

(1) Alternating current type These instruments work on the transformer principle, with the rope acting as the transformer core. An alternating current is applied through the primary winding and the resulting output from the secondary winding is monitored. Thus these instruments examine the average condition of a piece of rope passing through the magnetising coil at any given instant. They are therefore better suited for detecting general wear, corrosion and any other defects which occur over relatively long lengths of rope rather than for locating local defects such as individual broken wires. When used on stranded ropes, these instruments have one main advantage over the direct current and permanent magnet instruments in that their records can be analysed to give an estimate of the steel cross-section of the rope. They are however of little use on locked coil ropes because of the generation of eddy currents in outer layers of wires which tend to oppose penetration of magnetic flux into inner layers with the result that defects in inner layers are not usually detected.

(2) Direct current and permanent magnet types With these types, as the rope is passed through a magnetic field, defects in the rope cause local variations in this field which are usually detected by special search coil and recorded. The instruments give generally useful results when used on stranded ropes, being suitable for location of defects such as broken wires, local distortion and short patches of wear or corrosion. They are not however suitable for quantitative assessment of generally distributed wear or corrosion. In the case of locked coil ropes, investigations and trials in Great Britain have shown that although some inner layer defects, eg corrosion, can be easily detected, other smaller defects do not show up as clearly as similar faults on stranded ropes owing to the partial masking effects of the outer layers of wires. In some tests on locked coil ropes spurious indications of faults were obtained, but, when the ropes were opened up, no defects were observed. As the instruments are very sensitive to changes in the shape and diameter of a rope it is possible that these indications could have been caused by small manufacturing variations. For broken wires to be detected it is, in general, necessary for the broken ends to open up to give a gap of one millimetre or more. With locked coil ropes this movement may not occur in the early stages of deterioration, and breakages may thus remain undetected. However, even with this restriction, these instruments can give valuable information about the internal condition of the whole working length of a locked coil rope whilst it is in service which cannot be obtained by other methods; thus they can be used to supplement normal visual examinations.

14 In conjunction with the NCB, SMRE is directing the development of a new permanent magnet type instrument. This instrument uses Hall-effect sensors instead of search coils and these enable it not only to detect localised deterioration in ropes but also to measure generally distributed wear or corrosion thus offering the combined advantages of the present AC, DC and permanent magnet types. The prototype is being developed in a form suitable for certification, as intrinsically safe, specifically for monitoring stranded ropes used on underground manriding haulages. This instrument could also be used on some stranded shaft ropes. Other models may be built which would be suitable for larger shaft ropes including those of locked coil construction.

Lubrication of ropes

15 The purpose of lubrication of wire ropes is twofold. Firstly, it facilitates movement between wires within a rope, thereby reducing friction and internal wear and improving




distribution of the load. Secondly, it protects surfaces of both internal and external wires from corrosion. Lubricants have been developed to meet a wide variety of environmental and operating conditions but, even so, particular needs may still require special lubricants to be made up. Essential properties of a wire rope lubricant are:

(1) It should firmly adhere to the wires and be viscous enough to resist gravitational forces in vertical ropes, centrifugal forces generated by high speed coiling and the effects of air velocity.

(2) It should be non-corrosive, stable over the range of temperatures and environmental conditions likely to encountered, and under no circumstances create by-products which would attack the wires.

(3) It should be water repellent to protect internal and external surfaces from water or corrosion, and to displace moisture when it is applied to the surface of a rope.

(4) Its rate of deterioration should be such that hardening and cracking, brought about by age, exposure or temperature changes, are minimal.

(5) It should, when applied externally during service, penetrate to compensate as far as possible for loss of the manufacturer’s internal lubricant.

(6) It should be compatible with lubricant used in manufacture.

(7) No ingredient should be injurious to health during application or because of evaporation into mine air.

16 Because it is difficult to lubricate fully the internal part of a rope once it is made up it is important that ropes be thoroughly lubricated during manufacture. Both petroleum based compound and mixtures of bitumen in mineral oil are used in the manufacture of ropes for winding installations. Stranded ropes for relatively light duty are often lubricated with petroleum jelly containing standard additives according to the working environment. For ropes for general and heavier duties, lubricants consist usually of bitumen in mineral oil with extreme pressure, anti-corrosion, anti-oxidation, and/or water repellent additives. These lubricants are generally semi-solid at working temperatures and applied hot during manufacture of a rope. Petroleum based lubricants may be used for smaller locked coil ropes. With friction winding ropes the quantity of lubricant used must however be carefully controlled to avoid exudation of excess lubricant onto friction treads. For locked coil friction winding ropes, specially developed bitumen based lubricants are used, and general practice is to lubricate the inner layers heavily with a bitumen in oil compound and to lay up the outer one or two layers in a virtually dry condition. In service the lubricant spreads eventually to the outer layers. Some manufacturers contain the internal lubricant within a rope by adding fibrous material to act as a binder for the bitumen.

17 Dressings applied in service protect surfaces of external wires from corrosion and help also to reduce internal corrosion by restricting ingress of moisture and dirt. The frequency of application and the type of lubricant used should be related to the duties and service conditions of each rope.

Winding ropes in service

18 Some lubricants available for service application are basically those used during manufacture of ropes, with volatile thinners added. For wet and arduous conditions, compounds are available containing anti-corrosion, tackiness, water repellent and in some cases de-watering additives. The de-watering additives emulsify with water present on a rope and ensure that oil is kept in close contact with its surface; it is




however necessary for lubricants with de-watering additives to be cleaned from ropes before the lubricant becomes saturated with water. The colour of the oil, which changes as its water content increases, can be a guide as to when cleaning and re-lubrication are necessary. With petroleum based compound containing de-watering additives water is removed from a rope but not absorbed by the compound to the same extent as bitumen based mixtures.

19 Several devices for the automatic lubrication of drum winding ropes are in use but the great majority of these ropes in Great Britain are still manually cleaned and lubricated. It is only necessary for automatic lubricators to be operated intermittently and where they have been used there is some evidence that lubricant is more effectively introduced into ropes. This method of applying lubrication may be suitable for ropes at mines where shaft conditions are particularly severe.

20 In the case of friction winding installations, externally applied lubricants or dressings must not seriously reduce friction between rope and tread. When friction winding was first introduced into Great Britain some of the locked coil ropes were, and some still are, never lubricated during service. Initial problems with internal corrosion of some of these locked coil ropes led however to use of light oils, initially transformer oil, applied sparingly, with care being taken to wipe off surplus oil with dry cloths before winding was resumed. Specifically developed lubricants for locked coil friction winding ropes have now been available for several years and are used with a good measure of success. Despite precautions taken to avoid exudation of internal lubricant from friction winding rope, this still occurs occasionally when new ropes are installed so they have consequently to be carefully examined for excess lubricant and cleaned where necessary during initial operation.

21 Mechanical cleaning and lubricating devices are not used on friction winding ropes in Great Britain but a system of localised injection of lubricant under pressure into locked coil ropes has been used. The system was originally developed to counter the early problems of internal corrosion in large ropes already referred to: a gland is clamped to a stationary rope and pressure of 3000 lbf/in2 (20 MPa) injects lubricant along the inside of the rope for a distance of up to 65 ft (20m) on each side of the gland. The system is now used on a few drum and friction winding ropes but only where it is necessary to augment normal methods of lubrication.

Balance ropes in service

22 Flat balance ropes are difficult to examine properly if covered with high viscosity adhesive type lubricants, so it is preferable to use thinner oils which keep ropes cleaner as well as lubricating wires and protecting against corrosion. In the case of round balance ropes, lubricants of the types used for guide ropes in moderately wet shafts are generally employed. When round balance ropes with fibre cores are capped with white metal sockets, some internal lubricant may be melted out from those parts of rope adjacent to capels. A patented system is available for white metal cappings whereby a tube, fitted with a grease nipple, is cast into the white metal so at to leave an opening into the fibre core of the rope. Lubricant is pumped in to replace any which may have melted out and the process can be repeated if necessary during the life of the rope.

Guide and rubbing ropes in service

23 Viscous bitumen based compounds containing anti-rust, tackiness, water repellent and de-watering additives are commonly used for guide ropes and give good results in dry or moist conditions. They are not however easy to apply because they tend to stream and string in air currents encountered in shafts. Lubrication compounds with adhesive and emulsifying properties are generally used




in wet shafts; but under the most severe conditions, where large amounts of corrosive water are present, lubricants with anti-rust and de-watering characteristics without emulsifying agents have been used. Such lubricants are difficult to apply since it is first necessary to dry the surfaces of ropes; they last however for a reasonable time before fresh application is needed.

Methods of checking differences in rope tread diameters on multi-rope friction winding engines

24 Two methods of checking are described in the following paragraphs. Method 1 alone can be used if desired; but experience indicates that the more accurate procedure is to use method 1 for checking initial grooving when new laggings or inserts have been installed, followed by method 2 for finer adjustment and for subsequent routine checks during service.

Method 1 (see fig 18.4)

25 With both conveyances empty, or a counterweight system balanced, wind conveyance A from the surface (stage1) to approximately mid-shaft at a steady speed of about 10 to 15 ft/sec (3 to 4.5 m/sec). Bring the conveyance to rest very gradually without sudden brake application (stage 2).

Figure 18.4 Method for checking differences in rope tread diameters

26 With conveyance A at mid-shaft, mark the ropes on the same side as conveyance A at some convenient place, such as ground level or a suitable floor level in the case of tower mounted winding engines. The marks can be made by pencil on chalk background or by white adhesive tape and should be in a horizontal line; this is normally achieved by using a straight edge and spirit level but if site conditions permit it would be advantageous to have permanent straight-edge supports available.

SURFACE Mark ropes

Check ropemarks and

measure

X

STAGE 1

A

STAGE 2

A B

STAGE 3

A

MID SHAFT

PIT BOTTOM

B

B

Distance X should be equivalent to at least 2 - 3 drum revolutions




27 After marking the ropes, wind conveyance A steadily up the shaft for two to three drum revolutions until the rope marks are at another convenient level for checking. Again bring the conveyance to rest very gradually without sudden brake application, and mount the straight edge accurately in a horizontal position so that measurements for each mark relative to the straight edge can be taken (stage 3).

28 It is necessary to correct differences in rope travel by trimming grooves which give the largest rope travel. When method 1 alone is used, the point at which trimming becomes necessary is largely determined by experience but it is suggested that treads should be trimmed when discrepancies have reached the limits in table 18.1. By this method equalisation of treads can usually be achieved to limit discrepancy in rope travel to within 1/32 in (1mm) over two to three drum revolutions. If grooves are dirty, trim them clean first. After each trimming, wind the conveyance through the shaft to bed in the grooves and re-check measurements following the procedure outlined.

Table 18.1 Rope discrepancy limits

Ropes where trouble has been experienced during Limit of discrepancy

First 12 months 1/4 inch (6 mm)

Second 12 months 1/8 inch (3 mm)

Ropes where trouble has not been experienced during

First 12 months 3/8 inch (10 mm)

Second 12 months 1/4 inch (6 mm)

Note: A new rope will generally tolerate a greater discrepancy than one that has been in service for some time

29 To assist in making a detailed assessment of this method of checking rope tensions and tread diameters, a record should be kept of:

(1) the actual measurements and date of checking; and

(2) the date of trimming of each groove.

Method 2 (see fig 18.5)

30 Method 2 takes into account variations in the system, including rope diameter, rope modulus, drum bending, tread material variation and rope tread circumference. The measurements obtained are a reflection of differences in elastic rope stretch caused by such variations.

31 Conveyances should be empty. Operate the winding engine through a full cycle of two complete winds to eliminate any effects on rope lengths caused by previous winds with loaded conveyances (stage 1). Lower conveyance A to approximately mid-shaft and mark the ropes as described in paragraph 26 at some convenient position at the top of the shaft (stage 2). Lower conveyance A slowly to the bottom of the shaft so that the rope marks descend (stage 3) then slowly raise it back to mid-shaft, taking care to ensure that winding is carried out as smoothly as possible (stage 4). If rope tensions are unequal, the marks which were originally level will have separated. Measure and record this separation.

32 Continue the wind by raising conveyance A to the surface (stage 5); then lower it to mid-shaft to bring the rope marks back to their original position (stage 6). At




this stage all rope marks should be level. Any discrepancy will have been caused by rope creep or slip, in which case the procedure should be repeated more gently to avoid these effects.

Figure 18.5 Method 2 for checking differences in rope tread diameters

SURFACE Mark ropes

STAGE 1

A

STAGE 2

A B

STAGE 3

A

MID SHAFT

PIT BOTTOM

B

B

SURFACE

Check ropemarks and

measure

STAGE 1

A

STAGE 2 STAGE 3

MID SHAFT

PIT BOTTOM

Check that ropemarks are level

if they are notrepeat whole

procedure

B

A

B

A B




33 When a satisfactory test without discrepancy at stage 6 has been achieved, check that the greatest vertical separation of marks at stage 4 does not exceed 15% of the extension caused at shaft bottom by the designed load of a rope. The designed load of a rope is its share of the total suspended load when a conveyance is at shaft bottom. Should the vertical separation measured exceed 15% of this extension, the drum grooves require machining. The groove to be machined first is that of the rope having the highest mark. After trimming the grooves, the entire procedure should be repeated until the vertical separation is less than 15% of this extension. 15% was chosen after many practical tests to allow a reasonable variation in rope tension that is sufficiently large to keep the frequency of machining grooves to a minimum and so conserve treads.

34 It should be noted that if, after marking the ropes at stage 2, the procedure had been reversed and conveyance A raised to the shaft top so that the marks moved upwards, and then lowered again to mid-shaft, the mark corresponding to the groove to be machined first would be lower than the others. It is therefore important to follow the procedure exactly as described.

19 Maintenance of suspension gear

Conveyance suspension gear

1 The standards of design, manufacture and maintenance of conveyance suspension gear have ensured reliable and safe operation of this equipment in Great Britain over many years. Regulations require that suspension components be examined daily; that detaching hooks be dismantled, cleaned and refitted at three monthly intervals; and that all suspension gear connecting ropes to conveyances be thoroughly examined at six monthly intervals. Maintenance of conveyance suspension gear including non-destructive testing is carried out at testing centres and is referred to in paragraphs 87 and 90 of Part 2A. Standards adopted comply with the NCB document Procedure for examining cage suspension gear at testing centres as agreed with HM Chief Inspector of Mines and Quarries. The definitive life of conveyance suspension gear in British mines is presently twenty years.

Balance rope suspension gear

2 Balance rope suspension gear is not subject in Great Britain to the same statutory requirements as conveyance suspension gear in regard to periodic examination. It is however considered that balance rope attachments should be removed for examination including magnetic particle inspection at intervals not exceeding five years. This corresponds to the maximum working life of balance ropes on drum winding engines recommended in paragraph 130 of Part 2A. In the case of friction winding installations it may be convenient to carry out such examinations at three yearly intervals when balance ropes are changed. Where swivels are used in balance rope suspension gear, it is necessary during service for them to be kept properly lubricated and any seals to be regularly examined. Where operating conditions are particularly severe it may be advisable to remove swivels periodically so that they can be dismantled, cleaned and thoroughly examined.

20 Maintenance of conveyances

1 In Great Britain, routine maintenance and simple repair work to conveyances is usually done whilst they are in position, but deterioration in service is closely watched. For major repairs or overhaul, conveyances are replaced to minimize time that shafts are unavailable. Maintenance requirements should be considered during




design, and provision made for effective access for examination of parts which are most likely to deteriorate and where effects of deterioration would be most serious. During winding and decking, stress fluctuations and shock loads imposed on conveyances are transmitted through their suspension members to the remainder of the structure. Fastenings and suspension members should be accessible so that they can be cleaned and properly examined for security and possible onset of fatigue cracking. Although balance rope support beams are not normally subject to fatigue, they should be readily accessible for examinations. Shock loads experienced in decking operations could cause local cracking especially if kep gear is in use. Decking pads materially reduce the incidence of such cracking.

2 A number of conveyances are manufactured either completely or in part from aluminium alloy. Electrolytic action could take place between aluminium alloy and steel sections if precautions are not taken to insulate them to prevent deterioration. Care has to be taken to provide an effective barrier along the body of any fastening between the two metals.

3 Regulations in Great Britain require conveyances which are part of a winding installation to be examined at intervals not exceeding 24 hours, but they do not specify any other examination nor is any limit imposed upon the life of a conveyance. Each manager’s scheme for the mine should specify a detailed examination at suitable intervals. Procedures for non-destructive testing of conveyances when new and periodically during service are in section 29. When carrying out detailed examinations, care must be taken to check the fastenings at points where shock loads are imposed in case rivets, bolts, etc. have been subjected to excessive loads. Effects would normally be fretting and looseness, but in some cases shock load is transferred through fastenings into the main body of a conveyance, causing cracks in its structure or platework. This form of deterioration may also be found around guide shoe fastenings, especially where the guides are rigid.

21 Maintenance of rigid shaft guides

1 Rigid guides are not as widely used in Great Britain as rope guides. The principal types of rigid guide are flat bottom steel rails, and to a lesser extent wooden rails, fixed to buntons generally made from rolled steel joists or channels. In addition to the 24 hourly statutory examination each complete guide system should be thoroughly examined at suitable intervals, depending upon the nature and duty of the installation, and these intervals should be specified in the manager’s scheme for the mine. Periodic examinations should include use of profile gauges to determine the pattern and extent of wear at all points in a shaft where severe wear is known to occur, and also at other appropriately spaced points throughout a shaft. Profile gauges should be made using new rail as a template and not from nominal rail dimensions, thus taking care of any variation in rail size from the standard. During examinations, all connections, bolts and supporting structure should be checked to ensure that they are secure and that there is neither significant misalignment between adjacent lengths of guide nor excessive corrosion. Although general rules have not been made for permissible limits of wear they should be prescribed for each installation. A master plan prepared in association with that in section 15 should be produced for examination and recording purposes, identifying every bunton and rail.

2 In addition to determining wear, measurements should be taken at selected locations in a shaft to ascertain that:

(1) adequate clearances are maintained between conveyances;




(2) adequate clearances are maintained between conveyances and shaft walls or any fixed obstructions; and

(3) slippers or rollers can neither be nipped nor come out of engagement with guides.

3 Accelerometers mounted in a conveyance may be used to indicate the effect of misalignment of the guides on the conveyance and the position in the shaft where it occurs. Where re-alignment of guides is necessary, laser beams, referred to in paragraph 189 of Part 2A, may be used with advantage.

4 In addition to regular checks of the heads of steel rail guides for wear, flat bottoms of rails should be examined for corrosion particularly at connections with buntons or bunton pads where they may in addition be subject to wear. If joints are dowelled, replacement of single rails can be difficult; arrangements should be made for dowels in new rail to be retracted and then, after installation, moved out to locate the rail ends. Experiments have been carried out in which a dowel retracted into a rail head was forced into its final position by grease pumped in behind it from a grease gun.

5 Present practice is to make buntons from standard rolled steel sections which should be regularly examined to check that corrosion of webs is not excessive. When replacement buntons are set into a shaft wall they should preferably be concreted in, rather than bricked, to be more secure. In some shafts, buntons are located in cast iron pockets set into shaft walls and this facilitates replacement of buntons. Where a shaft lining consists of metal tubbing, an effective way of securing buntons is to bolt them either to tubbing joints or to fabricated brackets secured to bosses on the tubbing.

22 Maintenance of shaft side equipment

1 Shaft side equipment as referred to in paragraph 139 of Part 2A has in Great Britain proved over many years to be robust and reliable. At most installations there are limited running clearances between conveyances and retractable gear when the latter is in the retracted position. Malfunction, excessive wear or deformation may lead to situations which could affect the safe operation of a winding system, and it is important that retractable gear be regularly examined and effectively maintained. Limits should be set for clearances and wear which are allowable under normal winding conditions; and each item should be regularly examined for signs of deterioration, to check that clearances are adequate and that it is secure. Provision should be made to prevent freezing of water in compressed air operated equipment.

2 Control and interlocking of shaft side gates and decking equipment may be relatively complex and personnel need to be aware of safety procedures to be followed when carrying out maintenance and testing. For certain tasks requiring multi-discipline involvement, it may be necessary for both the mine mechanical and electrical engineers to issue joint safety instructions.

23 Maintenance of shaft pipes and cables

1 Pipes and cables are used in shafts for water, compressed air, methane, hydraulic and pneumatic hoisting, mine air sampling, power, communications, remote control and monitoring. Complete or partial collapse of such equipment could have serious consequences particularly if persons were being wound at the time. Regulations in Great Britain do not make specific provision for examination at regular intervals of shaft cables, pipe ranges, and their supports, not forming part of winding




apparatus; but each manager’s scheme for the mine should require such equipment to be examined to ensure that it has not been damaged or displaced, and should detail the nature of periodic examinations for each particular item. Examinations should be carried out by persons who have a thorough knowledge of the particular shaft, in order that they can identify any changes in the condition of equipment. This is particularly important in the case of daily examinations, made at the time of the shaft examinations, which usually involve observation from the top of a slowly moving conveyance to check that equipment has not been damaged or displaced. Shaftsmen are normally responsible for daily examinations; but supervisory members of the electrical and mechanical engineering staffs should periodically accompany them to ascertain that equipment is not deteriorating to any significant extent.

2 When carrying out installations and periodic examinations, special attention should be paid to the following features:

(1) Care should be taken to identify and keep clean all places in a shaft where spillage or salts can accumulate around pipes, power cables etc, and their supports. Accumulations may inhibit proper visual examination and can create moisture traps which may lead to rapid corrosion.

(2) Inspections should be made of these parts of pipes adjacent to flanges where deterioration tends to be more rapid. There should also be close inspection of pipework adjacent to or touching a shaft wall or tubbing since the general condition of pipes at these places is difficult to assess.

(3) In order that loss in pipe wall thickness due to external or internal wear or corrosion can be monitored, the original pipe wall thickness should be recorded for purposes of comparison. Ultrasonic instruments are now available which are capable of gauging thickness of not only ferrous metal but also non-ferrous materials. To minimize corrosion, where appropriate, suitable external and internal treatment should be applied to iron and steel pipes prior to installation.

(4) In wet shafts, or where it is known that strata behind shaft walls or tubbing contain water, it is advisable that joists or other means used for supporting pipes, power cables etc. should be given suitable anti-corrosion treatment before installation. Where shaft conditions are hostile, such as where condensation occurs, it may occasionally be advisable to investigate the condition of hidden steelwork contained within a shaft wall or tubbing to ascertain the extent of any corrosion.

(5) From a safety point of view all redundant items of equipment should be removed as soon as possible.

24 Maintenance of electrical equipment

1 Detailed maintenance information of electrical equipment is available from various sources such as manufacturers handbooks, owners’ instructions, etc. The following paragraphs describe installation features and some maintenance procedures designed to promote improved safety and reliability of such equipment when it is used in and around shafts.

Control and interlocking devices

2 Electrical equipment in use in shafts, headframes and at shaft entrances includes various control and interlocking devices for winding and ancillary apparatus. Failure or malfunction of this equipment may lead to hazard, so it is important that regular




examinations and tests be made to prove that operation is satisfactory and equipment properly maintained. Various types of switch are used for the purposes of interlocking; and for proving the operation of keps, shaft gates, conveyance in-line gear, retractable platform gear and decking plant. Some switches are purposely designed, and others adapted, for the duty and environment. Magnetically operated and inductive type switches are reliable and require minimal maintenance; mechanically operated contact switches have proved to be generally reliable but to require more maintenance. It is sometimes necessary to include an intervening mechanism between the initiating equipment and a contact type switch to avoid damage due to overtravel or shock loading. Clearances between conveyances and some retracted shaft side equipment are relatively small, and particular attention should be paid to the location of any proving switches. Each operating position of initiating equipment should be separately proved, taking into account the operating range of switches and allowable wear of equipment.

Shaft cables

3 In addition to routine tests of insulation and conductivity, it is necessary at specified intervals to examine the physical condition of shaft cables, cleats and suspensions, and the security of cables within the cleats. To prevent damage to cables from falling objects, cleats should have tapered ends or be fitted with suitable deflectors; and deflector plates should be fitted above cables where they are vulnerable such as where they pass horizontally around a shaft at entrance or exit points.

Visual indicators

4 In Great Britain, indication of the operational state of proving and interlocking devices is mainly limited to that required by banksmen and onsetters for winding purposes. This type of indication, if suitably extended, could assist maintenance personnel to locate faults and to check operation of proving and interlocking devices.

Cleaning

5 To avoid the risk of fire or flashover, it is necessary that adequate and regular cleaning of winding engine equipment and its environment be undertaken.

25 Maintenance of emergency winding apparatus

1 In paragraphs 71 to 76 of Part 2A reference is made to the provision of apparatus for affording means of emergency egress to persons employed below ground in a mine; and to mobile winding engines.

2 Routine examination, testing and maintenance of permanently installed emergency winding apparatus is necessary to ensure that it is fit for immediate use. As the requirements of the Mines (Emergency Egress) Regulations 1973 for examination, testing and keeping records are similar to those for the manager’s scheme for the mine, it is convenient to include the apparatus in that scheme. The regulations require competent persons to be appointed to supervise training of personnel to operate the equipment and carry out the necessary safety checks associated with its use. Such training should be implemented and periodically reviewed to ensure that sufficient competent personnel are available.

3 There is no statutory requirement in Great Britain which specifically refers to the maintenance of emergency mobile winding engines when not in use. When a mobile winding engine is installed for use at a mine, it is appropriate to maintain it to conform




with relevant statutory provisions for permanent winding apparatus. To ensure that they can be put to work without delay in an emergency, mobile winding engines when not in use are subjected to appropriate examinations and maintenance procedures. Necessary ancillary equipment including special concrete pads or hardstanding, anchorages and other apparatus such as special headframe pulleys, is permanently installed at all shafts owned by the NCB; and examination and maintenance of this equipment is included in each manager’s scheme for the mine.

26 Lasers and other devices for aligning shaft equipment

Setting up lasers

1 Where laser beams are used for aligning shaft equipment, two parallel beams are needed. They are generally set up so that they are vertical and/or at fixed distances from appropriate shaft reference points. The apparatus is rigidly mounted in such a position that it will be protected against buffeting by air currents and damage from falling objects, and the beams will not be obstructed by a conveyance or other equipment. Mounting in head frames is usually satisfactory unless there is excessive vibration. It is necessary that the beams should be directed at targets fixed at the lower locations; this can be time consuming, since adjustment through an arc of 0.5 degree (0.009 rad) will displace a beam by about 13 ft (4 m) at a distance of 500 yd (450 m). This operation would be easier if lasers were provided with finer means of mechanical adjustment than currently available.

Measurements from a beam

2 One experiment in a shaft with different coloured targets showed that at a range of 900 yd (820 m) the brightest image was obtained with a red target, but the 2 in (50 mm) beam spot was surrounded by stray light up to 4 in (100 mm) in diameter. With a blue target the image was less bright but stray light was not visible. Blue targets were therefore used in the pit bottom for making measurements and, to provide the best possible conditions, a baffle plate with a 1 in (25 mm) diameter hole was centrally positioned in each beam at midshaft. Each baffle plate was set so that the outer edge of the beam appeared as a ring of uniform width around the hole thereby cutting out stray light and providing a clean edge to the beam. Portable red targets were then used at positions where measurements needed to be taken. When checking rigid guides, a satisfactory method of measuring off-sets from a beam is to have a target marked with gridlines and designed to be clamped to the face of a guide at each bunton position. Co-ordinates of the beam on the gridded target are recorded and the extent of re-alignment of each guide or bunton determined.

Establishing vertical lines

3 Truly vertical laser beams can be set up by first using an optical plummet to establish points in the same vertical lines at the surface and at the shaft bottom, and then setting laser beams parallel to these lines by measuring offsets. A recently developed flameproof laser unit which incorporates a true vertical setting device is being investigated and may prove useful in shafts. It has a nominal working range of 550 yd (500 m) at which the beam diameter is 2 in (50 mm) and has provision for fine adjustment.

Distance measurement

4 Electronic distance measuring instruments have been this developed which are accurate to within ± 0.4 in (10 mm) over 1100 yd (1000 m) this meeting any requirement likely to be encountered in a shaft. Instruments of this type arranged




for sighting vertically downwards are now available and have been successfully used for setting out bunton positions.

27 Protection of steelwork from corrosion

1 Good preparation of new steelwork before treatment is essential and will be reflected in the quality and life of the finished work. Treatment should be carried out in the factory after manufacture and any damage caused in transit rectified on site. Drilling on site and other work liable to destroy protective coatings can be reduced to an absolute minimum with good planning. Where steelwork is to be used in shafts, very durable methods of protection should initially be employed since subsequent re-treatment in position may be impracticable.

2 With many existing structures such as headframes and winding engine towers, access for routine inspection can be difficult. The costs of scaffolding, cleaning, surface preparation and labour constitute a large part of total re-treatment cost. It is therefore usually preferable to accept the expense of durable treatment and to employ only reliable contractors who are prepared to back their work with enforceable guarantees.

3 BS 5493:1977 refers to the vulnerability of zinc and aluminium coatings to attack by liquids having pH values outside the ranges 5 to 12 for zinc and 4 to 9 for aluminium. If zinc or aluminium coatings are used in these circumstances, additional protection should be provided preferably by application of a sealer. In coal mines where there is a risk of presence of inflammable gas, use of aluminium coatings may be restricted because of danger from incendive sparking.

4 Steel sections heavier than the required minima may be employed as a means of resisting the effects of corrosion, but the effect of self weight should be considered at the design stage. Corrosion monitoring should always be carried out at critical stress points rather than at points which are chosen because they are readily accessible.

28 Shaft air heating

1 Reference is made in paragraph 192 in Part 2A to shaft air heating and the presence of water and ice in shafts. When tubbing is at its coldest, flow of water is likely to be greatest; and this can be reduced by caulking leaking joints with wooden wedges possibly aided by sealants. Maintenance work of this nature is not pleasant but can be effective. Grouting behind shaft walls is probably the only satisfactory method to reduce flow of water to an acceptable rate through concrete or brick walls, and grouting can also be used behind tubbing. When boring shaft walls for this purpose precautions such as those referred to in paragraph 3(5) of section 16 should be taken.

2 If entry of water into a shaft cannot be restricted, the most effective way of minimizing formation of ice is by the installation of purposely designed equipment to heat air passing down the shaft to a temperature above freezing point. This can be achieved by heating a proportion of the air to a temperature of about 60 to 70ºC and using fans to force it into the shaft, through ducting if required, to mix with the main body of air. To avoid contaminating the main air stream with products of combustion, air should be indirectly heated by passing it over external surfaces of coal or oil fired combustion chambers and/or through flue gas or steam heat exchangers. Although some of these heating systems can be arranged to operate automatically whenever air temperature falls below a predetermined level, the usual practice, for reasons of economy, is to bring them manually into operation when




formation of ice is judged to be imminent. Where heated air enters a shaft, care should be taken to ensure that it is not directed towards anything which might be adversely affected by high temperature such as cables, or lubricants on guide ropes.

29 Non-destructive testing of components of winding apparatus

Drums

1 All new drums should be non-destructively tested by the manufacturer using magnetic particle inspection. This involves examination of drum side and drum shell welds in fabricated sub-assemblies and examination of critical surfaces of cast drum sides. For NDT of winding engine drums in service, suitable procedures involving magnetic particle inspection supplemented by ultrasonic testing should be used.

2 There is a wide variation in design of existing winding engine drums and so it has not been possible to list all areas to be examined to each design. Visual inspection should however be concentrated on the following areas, followed by NDT as necessary:

(1) External surfaces:

- drum bosses especially at keyways;

- junctions between any structural member and

- bosses and/or rims including shrink hoops; on cast drums, areas within 50 mm of spoke edges;

- welding or bolts joining brake paths to drums, or areas around any other fixing bolts; and brake paths.

(2) Internal surfaces:

- junctions between any structural member and bosses and/or rims including shrink hoops;

- welding on any major stiffener or support; and on split drums, drum barrels in the regions of the joints.

(3) Generally:

- welding on any block or fixture used for fixing bolts;

- main fixing or joint bolts;

- any other area which has been repaired in the past or is known to contain imperfections or is suspected of being highly stressed; and areas where lamellar tearing is possible.

Winding engine main drive reduction gears

3 All new reduction gears should be non-destructively tested during manufacture to requirements similar to those of the revised NCB Specification No 383. This procedure is considered adequate to ensure that all reduction gears delivered are free from imperfections which could impair service performance or safe working.




4 In order to monitor performance of gears in service, suitable procedures for their routine examination should be adopted. These involve magnetic particle inspection using current flow techniques and are generally described in paragraphs 10 to 12 of section 31 in Part 1B. Experience of behaviour of gears has permitted consideration to be given to extending periods between examinations on the basis of duty, in accordance with frequencies in table 2 of Part 2A. Frequency of examination should be determined using the category classification but varied where necessary on the basis of consideration such as age. Although from consideration of fatigue it might seem logical to increase the times between examinations, there is as yet insufficient information about other factors such as residual stresses to permit this.

Fabricated or cast headframe pulleys

5 Quality and NDT requirements should be specified for new headframe pulleys in any purchase enquiry. Some manufacturers carry out NDT as part of their own quality assurance procedures: but ultrasonic tests on pulley bosses to ensure avoidance of defects in their bores and to confirm soundness of flange peripheries and shrink hoop areas, and magnetic particle inspection of welds, should be included.

6 Fabricated pulleys in service should be non-destructively tested using magnetic particle inspection of welds and other areas as necessary. Because of experience of high residual stresses in some of these, it may be prudent to carry out limited examination of welds of fabricated pulleys after six months in service. Cast pulleys in service should be visually inspected, and hammer tested for any looseness of spokes. These tests should be supplemented by magnetic particle inspection of areas around the ends of spokes and at rim joints on split pulleys. Although there is no evidence that pulley wheels constitute a major hazard, an audit of their conditions is required at the frequencies in table 2 (see paragraph 204 of Part 2A).

Shafts for winding engine drums, gears and headframe pulleys

7 Requirements for NDT are similar. All new shafts should be examined by ultrasonic means at the raw material stage and by magnetic particle inspection of their whole surface areas when in the finished machined condition.

8 Routine NDT of these shafts should be carried out in service; these examinations should consist of ultrasonic flaw detection of the full length of each shaft, with particular attention to keyways and section changes, and magnetic particle inspection of journals where necessary. Visual inspection should also be made for signs of scuffing. One aspect of in situ ultrasonic testing of shafts is that both ends of a shaft are not always accessible for placing probes; because of design and experience of shafts so far, this does not however cause concern. Interpretation of the full significance of ultrasonic signals is nevertheless difficult and means of obtaining valid results by applying probes to one end of a shaft are being investigated. The state at which a growing crack can be detected is influenced by the method of test, and work is continuing on interpretation of ultrasonic signals. Maximum intervals between successive examinations of drums shafts are in table 2: the longer intervals for drum shafts of electrically powered winding engines are justified on the basis of experience. Calculations based on fracture mechanics (see section 30) for headgear pulley shafts designed and manufactured to National Coal Board Specification No 185 demonstrate that the intervals for these in table 2 are reasonable.

Conveyances

9 The parts of steel conveyances that may require NDT have been reviewed and it is considered that examinations should be concentrated on hangers and connecting




ears where winding and balance rope suspension gears are connected. The following examinations should be made of steel conveyances but special arrangements are required for the relatively few conveyances made from aluminium alloy.

10 New hangers and connecting ears of multi-leg chain type suspension gear should be examined by magnetic particle inspection, using current flow techniques over their whole surface prior to assembly.

11 For in situ examination in service, magnetic particle inspection should be used but the type of magnetisation may depend upon whether the conveyance involved is in a mine shaft where flammable gas may be present. The areas to be inspected are:

- where connecting ears are integral parts of hangers, from the tops of the connecting ears down to the points just below their connection to top hoops of conveyances; and

- where connecting ears are made separately and attached to main hangers, the full lengths of the connecting ears, and hangers from their tops to just below the last points of attachment of the connecting ears.

The recommended intervals between in situ examinations are in table 2: they should be revised as experience is gained and further investigations completed. It is also recommended that NDT should be carried out at each major overhaul and after any incident which could have caused abnormal loading. In respect of block type suspension gear, the attachment members on a conveyance for single-point, multi-point and balance rope suspension gear are considered to have been designed with a high reserve factor and, subject to future experience, are therefore thought not to need examination at prescribed intervals.

Ropes

12 Non-destructive testing of wire ropes in service is described in paragraphs 12 to 14 of section 18.

30 An illustration of the application of techniques of fracture mechanics to a headframe pulley shaft

1 This section illustrates the reference made to techniques of fracture mechanics in paragraph 206 of Part 2A. It should however be noted that the complex nature of many components precludes an assessment of service stress even though the fracture toughness of a material may be known; and that this combined with difficulties in accurately locating and sizing flaws precludes general application of these techniques.

2 Headframe pulley shafts are known to be subject to fatigue during service and experience has shown that there are four positions on a shaft where fatigue cracks may develop (see fig 30.2). These are at each bearing fillet radius and at each side of the pulley hub, 2 in (50 mm) inside the bore. In order to minimize the risk of fatigue in these positions the National Coal Board’s Specification No 185 for headframe pulley shafts requires that stresses are kept below 8000 and 4500 lbf/in2 (55 and 31 MN/m2) respectively when using 0.3% carbon steel in the condition specified ie 30 tonf/in2 (463 MN/m2) minimum tensile strength.

3 Any inspection technique is limited by the minimum size of imperfection which can be detected in practice. To make a conservative assessment of imperfections, It must be assumed that some exist which are slightly smaller than the minimum




detectable size. Possible growth of imperfections under the influence of working stresses may be assessed by techniques of fracture mechanics. Theories of fracture mechanics are based on analysis of cracked or flawed bodies which can be utilised under static or dynamic loading. Briefly, in a body in which the general stress level is below the elastic limit of the material, plasticity is restricted to a small zone at a crack tip and microscopic behaviour is essentially elastic. The concept of crack tip stress intensity KI is introduced (I-denotes the tensile crack opening mode, the case generally considered) and when this reaches a critical value KIC unstable fracture will occur. The parameter KIC is known as the fracture toughness and is recognised to be a material property. Stress intensity can be simply related to applied stress σa and crack length a by the equation:

KI=σaa0.5Y. (1)

Y is a factor incorporating loading and component geometry. At failure KI is equal to KIC and the critical crack length ac at any particular applied stress can be evaluated. Equation (1) can thus be used in design to ensure that unstable fracture does not occur.

4 The concept of stress intensity can also be applied to fatigue where the fatigue stress intensity ∆ K is equal to the difference between the values of KI at maximum and minimum stresses during the fatigue cycle. Fatigue crack growth can be adequately represented by the following equation:

(2)

where N is the number of fatigue cycles, da/dN is the cyclic growth rate and C and n are constants determined by experiment for any particular material. In order to estimate fatigue life, that is the number of cycles required for a crack of initial length ai to attain the critical length ac,equation (2) may be integrated as follows:

(3)

In rigorous analysis, computer techniques are necessary to estimate the value of N and hence the fatigue life. If no imperfections are detected it should be assumed that the initial crack length ai is equal to the minimum size detectable by the non-destructive technique employed in inspection. Furthermore, by application of the above technique the maximum periods between inspections may be able to be determined, which should be such that an imperfection cannot attain a critical size during those periods.

5 An illustration of the application of this technique to a specific headframe pulley shaft is given below. The shaft used as an example was from a drum winding installation at a shaft 290 ft (88.4 m) deep.

Working loads:

Weight of payload Weight of conveyance Weight of suspension gear Weight of mine cars Weight of suspended winding rope: 742.4 lb (337 kg)

dadN

= C (∆ K)n

daai

acN =C (∆ K)n

8960 lb (4063 kg)




Dynamic load due to normal acceleration (1.5 x static load)

= 1.5 (8960 + 742.4) = 14,554 lbf (64.7 kN)

Friction force (5% of suspended load)

= 0.05 (8960 + 742.4) = 485 lbf (2.2 kN)

Total rope pull

= 14,554 + 485 = 15,039 lbf (66.9 kN).

The total resultant load was obtained from the parallelogram of forces shown in fig 30.1, the weight of the pulley shaft and wheel being neglected. It was assumed that the angle of the winding rope was 30º to the horizontal. The total resultant load W was thus calculated to be 26,048 lbf (116 kN). The shaft dimensions are in fig 30.2 and the bearings are asymmetrically placed about the rope and pulley centre lines. For simplicity, the reactions were assumed to act at the centre of the bearing surfaces; and their values were estimated to be 0.586 W and 0.414 W as indicated.

6 The working stresses at the Critical positions were calculated making appropriate adjustments to the formula to account for asymmetry of the pulley wheel with respect to the bearings. With reference to fig 30.2,

At a, (4)

The value of K/

t (stress concentration factor) was obtained from standard graphs [Peterson, Ref (4)] and is applied to account for the stress concentration arising from the change in section at the bearing fillet radius. This calculation gives a working stress of 7043 lbf/in2 (48.6 MN/m2).

At b, (5)

At c, (6)

At d, (7)

These stresses are all less than the specified stresses of 8000 lbf/in2 (55 MN/m2) at the bearing fillet radii and 4500 lbf/in2 (31 MN/m2) 2 in (50 mm) inside the pulley hub bore, above which damage by fatigue may occur.

7 An example of the practical limits of ultrasonic inspection is represented approximately by fig 30.3 for reflections of 20 and 30 decibels less than the back wall echo. The effect of attenuation is shown by the broken lines and this can seriously reduce sensitivity, increasing the minimum detectable defect size. During inspection,

σa = R1X1 Kt/

32

πd3

σb = R1Y1

= 3981 lbf/in2 (27.5 MN/m2)

32

πD3

σc = R2Y2

= 4420 lbf/in2 (30.5 MN/m2)

32

πD3

σc = R2X2 Kt’

= 4975 lbf/in2 (34.3 MN/m2)

32

πD3




access to pulley shafts is frequently restricted to one end owing to close proximity of adjacent pulley wheels. The minimum size of defect that can be detected will then be greatest at the end of the shaft more remote from the test probe. Reflections at changes in section are a frequent source of confusion and may mask defects. This effect can be alleviated to some extent when access to both ends of a pulley shaft is available. For this particular headframe pulley shaft, the minimum defect which could be measured was equivalent to a flat bottomed hole 0.12 in (3 mm) diameter. With access restricted to one end, a conservative estimate of minimum detectable defect would be the equivalent of a 1 in (25 mm) diameter flat bottomed hole. This latter figure represents the worst possible condition likely to arise in practice. It is necessary to convert these flat bottomed hole diameters to equivalent surface cracks of depth a as shown in fig 30.4. This is achieved by means of integration on an area basis as shown diagram-matically. If the minimum detectable flat bottom hole defect has a diameter of d and an area of, then, the area of an equivalent surface flaw of depth a will be

Totalrope pull

W = 2 (Total rope pull) cos 30o

= √ (Total rope pull)

Totalrope pull

Resultant load W

30o

30o

30o

32.75”

11.125” 15.625”

2.0” 2.0”6.5”

7.0”

6.5”

7.0”

D

r

d

d

a

cbW

X2X1

Y2Y1

R2 (0.41W)R1 (0.586W)

d = 5”

D = 6.75”

r = 0.5”

X1 = 3.75”

Y1 = 7.875”

X2 = 3.75”

Y2= 12.375”

K/t = 1.51 = 1.35D

d

= 0.1rd

Figure 30.1 Parallelogram of forces

Figure 30.2 Pulley shaft for illustration of fracture mechanics

πd2

4




The equivalent surface defect depths for 0.12 in (3 mm) and1 in (25 mm) diameter flat bottomed holes are estimated to be 0.026 in (0.66 mm) and 0.418 in (10.6 mm). A further limitation to the theoretical limits of detection should be considered. It is not in practice possible to detect defects of a size less than half the wavelength of the ultrasonic beam. Wavelength is given by the following formula:

(8)

where C is the velocity of longitudinal sound waves in mild steel 19,550 ft/sec (5960 m/sec), f is the frequency (2x106 Hz assuming a 2 MHz probe is used) and l the wavelength. This gives a wavelength of 0.12 in (3 mm) and hence a practical limit on defect size of 0.06 in (1.5 mm). A defect of this size is equivalent to a flat bottomed hole of 0.235 in (6 mm) in diameter which is above the limit for defect measurement and represents the practical limit for detection under ideal conditions. In view of the above practical limitations, a crack depth of 0.418 in (10.6 mm) equivalent to a flat bottomed hole of 1 in (25 mm) diameter is used as a conservative, but not unrealistic, minimum detectable defect size for the following fracture mechanics calculation.

8 There are two possible calibrations of the stress intensity factor KI (from which estimates of values of the geometrical factor Y may be obtained) applicable to a surface defect in bonding, [Bush, Ref (1), and International Institute of Welding, Ref (3)]:

r-arA - A1 = 2 (r2 - x2)1/2 dx. which can be expressed as

= 2 1/2 x r2 - x2 + r2 sin4

πd2

r-1X

r-ar

30 dB < Back wall echo

20 dB < Back wall echo

1Distance from probe: m

Attenuated signals

Equivalent flatbottomed holediameter: mm

25

20

15

10

5

02

Flat bottom hole

Surface flaw

X A A’

Y

r

d

a

Figure 30.4 Diagramatic reppresentation of equivalent flaws

C = f λ

Figure 30.4 Diagramatic representation of equivalent flaws




(9)

where Y/ is given for values of the ratio of crack length to bar diameter in tabulated form; and

(10)

where Qo is a factor dependent on the ratio of crack depth to surface length and Mb is a correction factor dependent on the ratio of crack depth to bar diameter.

9 A crack depth 0.418 in (10.6 mm) results in stress intensities of 5900 and 8340 lbf/in1.5 (6.49 and 9.17 MN/m1.5) respectively for the two methods outlined above. The latter is considered more appropriate because it is more conservative; and more generally applicable since the former gives values of Y’ for a specific ratio of span to bar diameter in three-point bending. The fracture toughness of typical pulley shaft material is not known but a conservative estimate is 30,000 lbf/in1.5 (33 MN/m1.5). The critical crack length for final failure is estimated to be approximately 3 in (76 mm) from equation (10). This large value of critical crack length indicates that the possibility of brittle failure in this case is remote and it is more likely that plastic collapse will occur before the fatigue crack attains its critical length.

10 During operation, the pulley shaft is subjected to alternate tensile and compressive loading; and it is assumed that fatigue crack growth would only occur in the tensile half cycle. The fatigue stress intensity corresponds therefore to the difference in stress intensities and thus calculated as follows:

∆ K = 8340 – 0 lbf/in1.5 (9.17 – 0 MN/m1.5)

and the fatigue crack growth equation is assumed to be:

(11)

This equation applies for a 0.07% carbon, high nitrogen mild steel [Ritchie et al; Ref (5)], but can be applied in this case since growth for the material in question is not likely to be significantly different. It is estimated that this headframe pulley shaft undergoes 38,660 winds per annum at 11.5 revolutions per wind. This corresponds approximately to 22.5 x 105 cycles in the 5 year period between inspections specified for medium duty in table 2 of Part 2A. Based on growth given by equation (11) for an initial fatigue stress intensity (∆ K) of 8340 lbf/in1.5 (9.17 MN/m1.5) the cyclic growth rate da/dN is estimated to be 3.712 x 10-8 in/cycle (9.428 x 10-7 mm/cycle). As the crack grows, this rate increases and simple linear extrapolation to determine total growth may lead to error. An integration is therefore carried out to determine total growth using the initial ∆ K value and the final ∆ K value of 9180 lbf/in1.5 (10.1 MN/m1.5) with a corresponding growth rate of 5.46 x 10-8 in/cycle (1.39 x 10-6 mm/cycle). The total growth in 22.5 x 105 cycles (5 years) is then 0.09 in (2.3 mm).

11 Summarising results of the above assessment, the maximum flaw which could be missed during non-destructive testing is conservatively estimated to be equivalent to a surface flaw 0.418 in (10.6 mm) in depth. Analysis of fatigue crack propagation indicates that a flaw of this size at the bearing fillet radius would increase in length by 0.09 in (2.3 mm) in the 5 year period between inspections. The critical crack length for final failure is however estimated to be approximately 3 in (76 mm). Failure of the pulley shaft due to fatigue crack growth between

K1 = σa

Mba0.5

Q0

= 7.681 x 10-12 (∆ K)4.

dadN

K1 = σaa0.5Y’




inspections is therefore considered extremely unlikely under the specified working conditions. In this respect the non-destructive testing technique and the inspection frequency appear to be quite adequate to ensure safe working.

12 It is clear from this fracture mechanics assessment of the extent of fatigue crack growth during five years’ operation that there is no danger of growth of a defect from just below the detection limit to a critical size. The assessment was necessarily conservative since very little detailed information was available concerning either fracture toughness values or fatigue crack growth. Nevertheless, since this assessment predicts safe working of the pulley shaft under the conditions specified, a more rigorous analysis would predict an even greater margin of safety. At this particular winding installation, moreover, only about 10% of winds involve the maximum loading as used in this analysis, making the estimate still more conservative. It appears that any significant cracks in these components would be readily detected by the ultrasonic non-destructive testing and a decision to withdraw a component from service could be made prior to ultimate failure. It is assumed in this analysis that the components and working conditions are as specified but this is not always the case; higher stresses can be induced by poor engineering practice. It is important to consider conditions such as fretting and corrosion which may accelerate fatigue crack growth; fretting alone can reduce the conventional fatigue limit in severe cases by a factor of 5 or even more (Engineering Sciences Data Unit Sheet No 67012). This is particularly important at the positions 2 in (50 mm) inside the pulley hub bore where design should ensure that relative elastic movements between the pulley shaft and hub are minimized. This can generally be achieved by suitably balancing the stiffness of the pulley shaft with that of the hub assembly. Increased loading may arise from dynamic effects inherent in the system or from bearing mis-alignment. Increased loading would cause increased fatigue stress intensities; and since crack growth rate has a fourth power dependence on these intensities (equation (11)) would cause accelerated fatigue. It is important to design against abnormal conditions which may arise in service such as indicated above. It is possible by means of more advanced techniques of fracture mechanics to incorporate such factors into the design. This necessarily involves a more rigorous analysis capable of allowing for variable loading, fretting and corrosion. It may however still be possible conservatively to predict fatigue life and necessary frequency of inspection.

13 Conclusions:

(1) Ultrasonic non-destructive testing is sufficiently sensitive to detect imperfections before they attain a critical size.

(2) Growth of imperfections from below the minimum detectable size to a critical size by fatigue between specified inspections is unlikely in the case of headframe pulley shafts which comply with the NBC Specification No 185.

(3) Other factors such as fretting, corrosion and increased loading arising from dynamic effects and from bearing misalignment are likely to accelerate fatigue crack growth and should be considered.

14 References:

(1) Bush, AJ Experimentally determined stress-intensity factors for single edge cracked round bars loaded in bending, Experimental Mechanics, July 1976, 249-257.

(2) Engineering Science Data Unit Sheet No 67012.




(3) International Institute of Welding: Draft rules for the derivation of acceptance levels for defects in fusion welded joints, WEE/37, Jan 1976.

(4) Peterson, R E Stress Concentration Design Factors, 1953; New York (Wiley and Sons).

(5) Ritchie, R O, Smith R F and Knott, J F Metal Science, 9(11) Nov 1975, 485.

31 Monitoring of mechanical equipment

1 The range of characteristics which can be monitored is summarised in table 31.1 together with some of the techniques. The large range of transducers available includes pressure transducers, movement transducers, strain gauges, thermocouples, infra red scanners and wear detectors such as contact devices. Many basic units for such devices are manufactured in quantity offering high reliability, minimum cost, and availability of spares; and a number of devices have been developed and improved as a result of practical industrial experience. For example, incipient failures of bearings and out of balance effects of rotating machinery can be detected by monitoring vibration before such deterioration is audible or visible. Signals from monitoring devices can be displayed in digital or analogue form, used to alert operators if preset limits are exceeded, called for on demand, eg during routine testing, or used to shut down plant if abnormal conditions arise.

2 Some devices and techniques have been or are being developed, namely:

(1) Measurement of brake pressure and brake shoe movement. While these give an indication that a brake is functioning they do not take account of brake path contamination and for this reason the torque reaction device referred to in (2) is being developed.

(2) A device to measure directly torque reaction from mechanical brakes of winding engines (paragraphs 34 and 35 of Part 1A and 29 of Part 2A). The purpose of this development is to signal the effect of mechanical braking effort so that electrical braking can be retained or discarded according to the amount of mechanical braking torque. This system summates outputs of strain gauge transducers mounted on brake shoes and has the facility to display the output of individual transducers. Comparison of output with previous recordings can be used to indicate whether there is out of balance or malfunction on individual brake paths. Outputs can be displayed continuously or on demand. The use of transducers fitted to brake rods of twin brake path systems is being investigated in Germany with similar objectives in view.

(3) Simple mechanical devices to give visual indication of displacement, or to give an electric signal. Such a device could be applied to brake rod pivots where seizure could result in high bending stresses for which the rods may not be designed. The degree of rotation in such assemblies is small and not easily seen. Indicators are proposed which magnify the movement and show if a pivot is moving freely.

(4) Improved methods of detecting slack rope in winding installations and monitoring conveyance position (paragraphs 95 to 99 of Part 1A and 38 to 41 of Part 2A).

(5) Improved methods of balance rope loop monitoring (paragraphs 133 to 135 of Part 2A).




(6) An electro-magnetic instrument for rapid non-destructive testing of stranded ropes. An instrument with facilities for audible and visible warning of major defects and for tape recording of rope condition is well advanced. Further research and development may extend this technique to locked coil winding ropes (paragraph 14 of section 18).

(7) Improved equipment to measure deceleration of conveyances (paragraph 83 of Part 2A). An intrinsically safe version of such equipment could be used to detect variations in winding engine performance, and if permanently installed, could continuously monitor changes in system behaviour.

3 Early detection of developing cracks in components often depends upon removing components from an assembly and then subjecting them to non-destructive testing (as described in Part 1B, section 5 and 31, and Part 2A, paragraphs 193 to 195). Two techniques are being studied which may enable defects in installed components to be reliably monitored:

(1) Vibration analysis. The technique used in work on rotating machinery such as underground fans may be used to detect onset of fatigue cracks in operating rods of a winding engine brake. The method relies on inducing vibrations in a bar of material when struck. If the bar is cracked changes in the characteristics of vibration occur. The work is described in paragraphs 5 to 7.

(2) Measurement of changes in compliance. In theory it is possible to monitor crack growth in any component of a brake system by measuring small changes in stiffness or compliance of the system. This technique is described in paragraphs 8 and 9.

4 It is necessary to demonstrate prospects of a gain in safety and reliability and a saving in conventional maintenance work to justify allocation of resources to the installation, maintenance, and operation of a monitoring device. Desirable characteristics of a monitoring device are:

(1) The device should preferably fail to safety. If it does not, it should be checked sufficiently frequently to ensure a high probability of operation. The example referred to in paragraphs 10 to 13 shows the relationship between equipment reliability, monitor reliability and time that a monitor could be in a fail to danger state.

(2) Output must be unambiguous and such that an operator or test engineer can readily interpret it and take necessary action. Operators should not be overloaded with displayed information.

(3) Installations of a device should not introduce new hazards, such as interaction with existing circuitry or weakening of existing components: It should in most cases be suitable for application to existing plant without major dismantling and permit ready access for servicing.

(4) Sensitivity of a device must be compatible with operating conditions. Ideally, faults within the range of stress, displacements etc for which plant has been designed and commissioned should not be signalled, but should be when this range is exceeded.

(5) A device should preferably be of a type with a proven long life and minimum requirements for servicing or checking.

(6) Outputs should produce effective warning so that action can be taken.




Table 31.1 Monitoring techniques available

Characteristic to be monitored

Typical techniques Typical application

Surface condition

Unaided eye Boroscopes Stroboscopes Non-destructive testing techniques Photographs (to record trends) Thermographs (temperature) Witness indents (surface wear) Surface prints

Any component – but limited use on installed components. Machinery usually has to be stopped.

Internal condition

Radiographs Temperature sensors (thermocouples)

Any component.

Surface strain (local)

Electrical resistance strain gauges Brittle coatings Acoustical strain gauges

Load bearing components in tension, compression, torsion or shear.

Linear or angular displacements and clearances

Preset gauges or jigs Potentiometer transducers Electrical contact devices Inductive loops Mechanical Indicators Proximity transducers (eddy current or capacitance)

Bearings and mountings. Mechanisms. Loose connections. Excessive wear. Lost motion.

Vibration or noise-deviations from normal

Unaided ear Displacement, velocity or acceleration transducers Oscilloscope - observation of wave forms Resonance changes Frequency analysis - comparison with normal Noise level meters Shock pulse meters Accelerometer signal averaging Acoustic emission (research stage)

Bearings. Rotating machinery (out of balance or wear monitoring). Fluid power circuits. Pumps, motors. Gearboxes. Load bearing parts.

Pressure or flow Diaphragm or capacitance transducers Piezo electric or resistive transducers Pitot tubes, venturi devices Flow meters

Fluid circuits, pipes, valves

Leakage Nose or unaided eye Gas detecting instruments Accurate pressure gauges with threshold alarms Electrical (surface conductivity)

Pressurised systems. Seals or glands. Pressure vessels.

Temperature Bimetallic strip (electrical contacts) Direct expansion (liquid, gas, metal) Thermocouples Chemical indicators Photographic (infra red)

Internal conditions. Bearings. Gearboxes. Furnaces or ovens.

Wear or wear debris

Magnetic plugs Oil analysis Filter checks Electrically conducting filters Spectrometric analysis Automatic particle counting

Bearings-rotating journal, ball and roller; especially when internal, or access or servicing is difficult.

Vibration analysis

5 Vibrations with a range of frequencies are induced in a bar of material when it is struck. If the bar becomes cracked, changes in three characteristics of vibrations

* Non-destructive Testing Centre, Atomic Energy Research Establishment, Harwell




could occur, namely: natural frequency, frequency spectrum and decay rate. Tests have been made to determine whether any of these changes can be measured sufficiently accurately to use them as a means of detecting fatigue cracks in a component. The tests were made on a 37 in (0.94 m) length of 1 in (25.4 mm) square section bar of En 8 steel. To keep the initial tests simple, the bar was supported on two rubber mounts positioned 8.5 in (0.22 m) from its ends, these positions being approximately at the nodal points for its natural frequency and its even harmonics. The transducer used for detecting the changes was positioned approximately 1 in (25.4 mm) from one end of the bar.

6 Of the three characteristics, decay rate has shown the most promise as a means of detecting fatigue cracks in a component. The smallest fatigue crack detected using this technique was 0.05 in (1.3 mm) deep at the edge of the bar; and this showed a detectable change in decay rate from the original uncracked condition of the bar. As would be expected, the larger the crack the more marked is the change. At Harwell Non-destructive Testing Centre*, a similar technique has been successfully developed for detecting cracks in mass produced aluminium alloy components, but a skilled operator is necessary to judge the characteristics of the induced vibrations.

7 An aim of the test programme is to be able to detect a cracked component without having to remove it from its working position. Two major difficulties present themselves at this stage in the test programme and these are:

(1) variation in vibrational characteristics caused by the method of mounting or fixing; and

(2) variation in vibrational characteristics caused by inconsistencies in material properties resulting from manufacture.

Measurement of changes in compliance

8 When a crack in a component of a brake system grows, compliance (i.e. the reciprocal of stiffness or displacement per unit load) of the component and of the complete system increase. It is therefore possible, in theory, to monitor crack growth in any component of a system. The theory and practice of linear elastic fracture mechanics in recent years has shown that the onset of rapid propagation from a slowly growing crack depends on the rate of change of compliance with increasing crack size. Thus change in compliance represents not just an arbitrary property that conveniently varies with crack growth but a property that is fundamentally related to the hazard that the crack represents.

9 An investigation is in progress to establish whether the compliance of a brake system can be measured sufficiently precisely to allow small changes to be detected. Initial measurements on the brake system of a small haulage unit have shown that the repeatability of the load-displacement characteristic is not sufficiently good to allow a small change in compliance to be detected from an application of a single load. Work is now aimed at utilising mean compliance determined from a large number of load applications. It seems therefore that a method suitable for application to winding engine brakes would have to employ continuous monitoring of load and displacement, so that any significant increasing trend in compliance could be isolated from random variations. Potential advantages of such a method of monitoring crack growth are that an entire brake system could be examined as a single unit and that this could be done without interfering with its use. In addition, the size of the effect being monitored is related to the probability of catastrophic failure from the crack.




Reliability of a monitoring device in relation to reliability of its primary system

10 If a monitor is not used and corrective action is not taken and an equipment ceases to operate as desired, there would be an annual loss of qeQ units where

qe is the fault rate of the equipment in failures per year, and

Q is the loss associated with each failure.

11 If a monitor is installed, which could be an instrument or a man etc, there is a probability Pm that the monitor would not detect abnormality in operation of the equipment and a further probability Ps that corrective action would not be successful after it has been initiated. It can then be shown that the annual loss with a monitor installed is approximately qeQ (Pm+Ps) provided Pm and Ps are both small, eg less than about 0.1. Hence the ratio of annual loss for monitored equipment to that of unmonitored equipment is (Pm+Ps).

12 If a monitor with a fault rate qm is checked at intervals of time tc and shown to be working, Pm can be calculated from

13 Example

If qe = 0.1, ie the equipment operates abnormally once in ten years;

and qm = 1, ie the monitor fails once per year;

and tc = 0.2 ie the monitor is proof checked five times per year;

and Ps = 0.1, ie corrective action once initiated fails one time in ten;

then the total loss per year is

compared with 0.1Q for the unmonitored system. It can thus be seen that, even though the monitor is ten times less reliable than the equipment, the system reliability has for this case been improved by a factor of five.

32 Model code for the testing of friction winding engines

1 In Part 1A, paragraphs 126(3) and 168, reference is made to a model testing code for friction winding engines. A provisional code has been implemented by the NCB since 1976 and amendments have been made, as a result of experience, relating to recording of time delays and the sequence of testing near to artificial landings. These amendments have been incorporated in this model code. There are as a result minor differences in those tests which are basically common to this model code and the model testing code for drum winding engines referred to in paragraph 122 of Part 1A; and it is suggested that the latter code be amended accordingly.

* Paragraph 42(1) of Part 1A recommends 5 ft/sec (1.6 m/sec).

Pm = θm1c

2

0.1 ÷ 0.1 Q = 0.02Q 1 x 0.2

2( (




2 In order to comply in Great Britain with the Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960, and the Special Regulations for Friction Winding Engines, it is necessary to carry out a series of tests when a winding engine which is ordinarily to be used for winding persons is first installed, and thereafter at regular intervals, to check that the safety system is properly adjusted. This code details the testing procedures to be followed every six months on friction winding engines serving vertical shafts. Explanatory notes given in appendices to this section should be taken into consideration as appropriate when making tests. Where there are individual equipments or circumstances for which this testing code is not applicable, then an appropriate individual test procedure should be established by the senior engineer or official concerned.

3 In Great Britain, the Special Regulations for Friction Winding Engines (see appendix 32.5 to this section) are in addition to, and not in substitution for, the Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960. When it is necessary to vary, or it is unnecessary to apply, the requirements of the latter regulations to friction winding engines, this is stated in the Special Regulations. The text below contains the appropriate variations in capitals, and indicates deleted material by dots, where the Shafts, Outlets and Roads Regulations are varied by the Special Regulations for Friction Winding Engines:

(1) Regulation 11(1) of the Shafts, Outlets and Roads Regulations requires that:

‘Where mechanically operated winding apparatus or mechanically operated rope haulage apparatus is ordinarily used for carrying persons through a shaft or unwalkable outlet and the speed of winding or haulage can exceed twelve feet per second* (3.7 m/sec) there shall be provided an effective automatic contrivance to prevent overwinding so constructed as:

(a) to prevent the descending cage or carriage from being landed at the lowest entrance to.....the shaft or unwalkable outlet at a speed exceeding TWELVE FEET PER SECOND (3.7 m/sec).

(b) to control the movement of the ascending cage or carriage to prevent danger to any persons therein.’

(2) Regulation 19(4)(b) of the Shafts, Outlets and Roads Regulations requires that the operation of the automatic contrivance be tested ‘at intervals not exceeding SIX MONTHS by attempting to land each cage when descending at an excessive speed’.

4 In order to comply with Regulation 11(1) above, the overwind safety system of a winding engine is designed to operate automatically in circumstances of maloperation of the controls by the winding engine-man or in the event of the failure of the winding engine controls to function due to any cause. The testing procedure in this code includes the necessary tests to ensure that the safety system is properly adjusted to deal with these eventualities and to comply with Regulation 19(4)(b) above. The sequence of tests is designed to check that the various components of safety apparatus operate satisfactorily before any attempt is made to land each conveyance at an excessive speed in subsequent tests.

5 Regulation 8 of the Special Regulations sets out the braking requirements some of which are summarised as follows:

(1) Manually variable service brakes shall be capable of holding a torque equivalent of 2.5 times the maximum static torque.




(2) Minimum retardations under emergency trip conditions shall be 3 ft/sec2 (1m/sec2) for men and 1.5 ft/sec2 (0.5 m/sec2) for mineral.

(3) The maximum permissible retardation under emergency trip conditions shall not exceed that produced by the greatest torque which will not cause slip between winding ropes and drum calculated on the basis of a coefficient of friction between them of 0.2. Maximum retardations for each normal loading that would not cause slip on this basis are referred to as the theoretical slip values.

6 When a winding engine or safety equipment is installed, the results of the comprehensive tests carried out to ensure that it is functioning correctly should be kept in the form of a Master Record for comparison purposes when checking compliance with the statutory landing speed and operation of the safety equipment. If some feature is subsequently altered such as a trip curve, retardation of winding cycle, or if doubt exists as to the authenticity of the Master Record, then comprehensive tests should be carried out to establish a new Master Record. Statutory test results should be compared with the Master Record and with the previous statutory test results. A copy of the Master Record for each winding engine should be kept in the winding engine house and the winder testing engineer should ensure that an up-to-date copy is available when he is carrying out statutory landing speed tests.

7 The tests specified in this code should be carried out by a competent winder testing engineer appointed in accordance with paragraph 135 of Part 1A. The winder testing engineer should be fully conversant with the operation, principles of control and safety apparatus of those winding engines with which he is concerned. The explanatory notes in the appendices to this section should be carefully considered in relation to each individual equipment to ensure that the testing procedure is properly applied and that excessive testing procedure is properly applied and that excessive testing is avoided.

8 It is important to appreciate that while winding equipment is designed to withstand stresses imposed during emergency trip conditions it is both unnecessary and undesirable during testing to initiate more emergency trips than are required to prove safe operation of the winding engine; during dynamic tests, trips where conveyances pass each other should be avoided.

Testing procedure

9 Where reference is made in the code to dynamic testing of a winding engine with an equivalent man load in one conveyance, it is implicit that the tests be repeated with the load changed over to the other conveyance. The standard test load should be declared and equivalent to the maximum number of men specified as the manriding load per conveyance, at 1.5 cwt (75 kg) per man.

10 For a conveyance and counterweight system, the standard test load should be used when testing with reference to the conveyance but the conveyance should be empty when testing with reference to the counterweight.

11 The banksman will normally be at his station during testing to supervise loading and unloading of the conveyances. It is important that during any movement of the winding engine involving a conveyance coming to the shaft top landing, he should be made aware of the intention and be ready to signal appropriately. This is particularly important when an artificial landing is being set up and removed.

12 During testing, a person should be stationed at an appropriate safe place in the pit bottom to detect any unusual circumstances which may arise, eg fouling of the balance ropes or displacement of the test load.




13 The requirements in paragraphs 11 and 12 above should be established for individual shafts in the light of experience and knowledge of the installations.

14 It is important during a winding engine test that the following points be borne in mind:

(1) The winder testing engineer should direct and control testing operations and only persons essential to the performance of these operations should be present in the winding engine house.

(2) The colliery mechanical and electrical engineers or their nominees should be present and be responsible for control of the winding engine during loading and unloading of the conveyance(s), and when any adjustments are being made. A nominee should be a person having supervisory duties; and adequate mine staff should be available to make any necessary adjustments.

(3) The winder testing engineer should be positioned, or provided with means, to give clear instructions to the winding engineman, and have a clear view of the graph on the recording instrument at the same time.

(4) Notwithstanding that a winding engineman will be operating under the instructions of the winder testing engineer during testing, he should be advised before testing commences to stop the winding engine if he becomes aware of anything that will affect the safety of personnel or equipment.

(5) When adjustments are made, a check should follow to ensure that they are correct, by a safe method, before attempting to resume the testing sequence. For some adjustments this may involve a brake holding test or a trip at low speed with an ascending load.

(6) The winder testing engineer should ascertain whether rope slip has occurred; and if it has he should take the necessary remedial action. (See appendix 32.1 to this section, paragraph 33).

General inspection

15 Before commencing a test, the winder testing engineer should ensure that the general condition of the winding equipment is satisfactory for the tests to be carried out, and that:

(1) Pivots, levers, etc on the automatic contrivance appear to be free and functioning properly.

(2) Brake linings are not unduly worn and brake paths are free from grease and oil and are not in danger of becoming contaminated.

(3) Brake posts and shoes are properly adjusted to give correct clearance and motion, linings are correctly bedded, and the brake engine or cylinders are within the limits of their travel. Where over-travel and wear switches are fitted these should be checked and operated manually.

(4) Winding ropes and winding sheave rope treads are free from excessive contamination, such as dirt, grease or water.

(5) When the automatic contrivance is set for man winding, the winding engineman’s and banksman’s automatic indicators are functioning correctly.




(6) In the case of AC winding engines, the supply voltage is noted.

(7) Any rope creep compensating device, depth indicator, automatic contrivance and cam gear in the winding engine house is correctly set relative to the conveyances.

16 This general inspection should not replace normal maintenance inspection.

Operation of the mechanical brake and safety circuit (see also paragraphs 2 to 15 of appendix 32.1 to this section).

17 This series of tests is to ensure that the level of braking torque is adequate and the safety circuit is functioning properly before tests at speed are made.

18 Brake holding tests-service braking

See also paragraphs 5 to 9 of appendix 32.1 to this section.

TEST 1A: winding engines with balanced conveyances and manually variable braking. Position the empty conveyances near mid-shaft and with the service brake fully on apply power torque up to a maximum value of 2.5 times maximum static torque (see appendix 32.1 to this section, paragraphs 5, 8 and 9) or until the drum moves through the brake. Note the maximum current applied and compare it with the Master Record. Repeat this test in the other direction of wind.

TEST 1B: winding engines with conveyance and counterweight and manually variable braking. Position the conveyance and counterweight in the shaft with the conveyance either empty or fully loaded whichever gives the maximum out of balance load (see appendix 32.1 to this section, paragraphs 5 to 9). With the service brake fully on apply power torque in the downward direction of the maximum out of balance load, up to a maximum value of 1.5 times the maximum static torque or until the drum moves through the brake. Note the maximum current applied and compare it with the Master Record.

19 The Special Regulations do not require a brake holding test to be carried out on winding engines which do not have manually variable braking. The adequacy of the brakes can be determined by retardations obtained during speed tests.

20 Application tests-emergency braking Position the conveyances or conveyance and counterweight near mid-shaft.

TEST 2: Take the brake fully off and, without applying power, trip the safety system by operating the winding engineman’s emergency stop device. The brakes should be applied automatically. Determine the brake force at the brake engine and compare it with the Master Record (see appendix 32.1 to this section, paragraph 13).

TEST 3: Where back up operating gear is provided which applies the brake when there is a failure of the main brake air or oil pressure, a test should be made to check that the back up protection is functioning correctly under failure conditions (See appendix 32.1 to this section, paragraphs 10 to 12).

TEST 4: Set the brake fully on and apply power to the winding engine. Trip the safety system by operating the winding engineman’s emergency stop




device. Power to the motor should be immediately interrupted or reduced. Where two safety circuits are used: ensure that both are in working order. Where two safety contactors are used in the same circuit: ensure that they both operate satisfactorily.

TEST 5: Trip the safety circuit by hand from each safety device in turn (See appendix 32.1 to this section, paragraphs 14 and 15). Test the back out circuit to ensure that when the brake lever is moved from the on position, power cannot be applied to aggravate an overwind. Check each direction of overwind.

Acceleration, brake time delay, trip characteristics and retardation tests

21 This series of tests is to determine the brake time delay, characteristic trip curve of the automatic contrivance, retardations produced by the brake and maximum speeds past the landing. (See appendix 32.1 to this section, paragraphs 17 to 32). Before commencing these tests, the winder testing engineer should ensure that any rope creep is compensated for, and that any rope creep compensating device in the winding engine house is correctly set relatively to the conveyance. If an electrical device is placed across the overspeed contacts of the automatic contrivance in order to indicate the instant of trip, precautions should be taken to ensure that there is no risk of interference with the operation of the safety contactors. When any testing is undertaken on the winding engine, precautions should be taken to ensure that effective operation of the protective equipment for the winding engine is not impaired. Such precautions can be taken by operating the overspeed contacts manually to break the safety circuit with the winding engine stationary and the service brake applied. An approved method of obtaining overspeed trip indication is described in appendix 32.4 to this section.

TEST 6: Wind the empty conveyance to mid-shaft and make temporary reference marks on the winding rope(s), drum and depth indicator. Accelerate the conveyances away from mid-shaft and when a speed of approximately one third to one half maximum manwinding speed has been reached, an emergency application of the brake should be made by opening the overspeed contacts and the retardation and brake time delay measured. (See appendix 32.3 to this section, fig 32.2). Wind the conveyances to mid-shaft and check the reference marks to establish whether slip has occurred. If the test is satisfactory, a similar test should be made in the opposite direction of wind at a speed of approximately one half to two thirds of maximum manwinding speed. The trip times measured should be compared with the results of the Master Record and the average of the trip times entered on the test certificate (See appendix 32.1 to this section, paragraphs 17 and 18). For systems having a conveyance and counterweight, the direction of the first test should be with the counterweight ascending. On completion of these tests the temporary reference marks should be removed.

22 Place the standard test load in one conveyance (see paragraph 10) the load being equal to the weight of the maximum number of men permitted to ride and set up an artificial landing for this conveyance as described in appendix 32.2 to this section. An artificial landing will be maintained for one or other of the conveyances for the whole of this series of tests. Any cam gear designed to reduce automatically the winding engine speed should be left set to the normal landing when the automatic contrivance is set to the artificial landing. Ensure that the automatic contrivance is set for man winding. With the loaded conveyance at the artificial landing, mark the winding ropes, drum and depth indicator to establish an accurate reference point.




TEST 7: Raise the loaded conveyance a sufficient distance above the artificial landing to enable half maximum speed to be reached in a descending direction. Lower the loaded conveyance; and at half maximum speed make an emergency application of the brake. Measure the retardation and compare the value and trace shape with the Master Record and/or the requirements in the Special Regulations. This test should be carried out using a velocity/time trace. This test need not be carried out if, when the characteristic trip curve in Test 10 is checked, a velocity/time retardation trace is obtained at half maximum speed and used for comparison with the requirements of the Special Regulations (See appendix 32.1 to this section, paragraphs 19 and 20).

TEST 8: The first landing speed test should be at a slow speed with little or no power applied and can be achieved as follows (see appendix 32.1 to this section, paragraph 22). Raise the loaded conveyance a sufficient distance from the artificial landing and then lower it at a steady speed, or allow it to gravitate, until an overspeed trip occurs just before the artificial landing.

TEST 9: Raise the loaded conveyance a distance above the artificial landing selected as below. With the brake fully on, apply maximum power torque (see appendix 32.1 to this section, paragraphs 29 to 32) to the winding drum in the direction of the artificial landing. Release the brake quickly. The starting position for this test should be such that the test will give a maximum speed at, or just before, the artificial landing; and this speed should be recorded as the maximum landing speed. Repeat this test at approximately one drum revolution from the artificial landing; and then at appropriate distances until the conveyance stops close to the artificial landing. (See appendix 32.1 to this section, paragraphs 22 to 24). A test from the artificial landing in the wrong direction may be carried out, but care should be taken that the automatic contrivance is not damaged by over-travel. The extent of over-travel can be estimated by examining the distance moved after the trip which produced a maximum speed at the artificial landing. The response of different winding engines varies and it will have to be determined by experience whether acceleration is greater when the brake is taken off before power is applied, or when power is allowed to build up before the brake is released.

TEST 10: Raise the loaded conveyance a sufficient distance above the artificial landing, say 1.5 to 2 drum revolutions, then lower it until an overspeed trip occurs at a speed greater than that recorded from one drum revolution in Test 9. Repeat this test for about three increasing trip speeds up to and including maximum man winding speed to obtain additional points on the trip curve. Finally accelerate the winding engine from the normal maximum man winding speed to obtain a trip at the maximum speed permitted by the automatic contrivance just prior to the retardation portion of the trip curve. By considering the distance of this trip point from the start of the retardation portion of the trip curve, an assessment can be made of the minimum stopping clearance from the landing with this trip speed (see appendix 32.1 to this section, paragraphs 27 and 28). The temperature of the brake path should be checked during this series of tests and cooling time allowed as appropriate.




23 During Tests 7, 8, 9, 10 and 11 the following records should where appropriate be taken

Trip speed.

Distance of trip point from artificial landing.

Retardation (see appendix 32.1 to this section, paragraphs 18 to 21).

Distance of loaded conveyance from landing when stopped.

Maximum landing speed.

Rope slip or creep.

When the above tests have been satisfactorily completed the artificial landing should be removed. (See appendix 32.2 to this section, paragraph 6, 10, 14 and 15). If test 7 has not been undertaken then the alternative retardation test obtained at about one half maximum speed during the characteristic trip curve tests should be compared with the Master Record and the requirements of the Special Regulations relating to retardation values.

24 Overwind setting In order to check that the setting of the automatic contrivance has been correctly restored, and to record the position of the overwind trip settings above the normal landing, the following test should be made:

TEST 11: Ensure first that the setting of any rope creep compensating device is correct. Then raise slowly each empty conveyance in turn until an overwind trip occurs. Record the position of the conveyance above the normal landing. Any back up overwind trip gear, such as headframe limit switches, should also be tested in a manner prescribed (see appendix 32.1 to this section, paragraph 34).

General check on equipment

25 After completing the tests, winding equipment including ropes, suspension gear and rope creep gear, should be examined by a responsible engineer before normal winding is resumed.

Statutory report

26 The winder testing engineer should make available to the appropriate mine staff, test results and other relevant information necessary to enable a report to be made of the six-monthly test on the statutory form.

Test certificate

27 The winder testing engineer should record the half yearly test results on a test certificate (see example in appendix 32.3 to this section) which should be attached to a copy of the velocity/distance traces (fig 32.1) produced when checking the automatic contrivance trip curve. Where the cage landing speed recorder used is of a type which produces traces on a velocity/time base (fig 32.2) then these traces should be re-plotted on a velocity/distance base to arrive at the automatic contrivance trip curve. The test certificate should be signed by the winder testing engineer, formally countersigned by an authorised person and distributed appropriately.




APPENDIX 32.1 Explanatory Notes

1 The following explanatory notes should be read in conjunction with the relative paragraphs of the Testing Procedure:

Operation of mechanical brake and safety circuit (See paragraphs 17 to 20 of code)

2 The series of tests listed under this heading is designed to check the brake holding capacity and satisfactory operation of the means of applying the brake under emergency conditions. There are a variety of braking arrangements is use but the following terms used in the text are applicable to all types:

SERVICE BRAKING is that controlled directly by the winding engineman, usually from a hand lever; both the rate of build up of torque and the level of torque are normally determined by the winding engineman. EMERGENY BRAKING is that applied automatically by safety devices. Both the rate of build up of torque and the level of torque are pre-set and independent of the winding engineman’s actions.

3 The majority of modern pressure controlled brake engines have separate adjustment of service and emergency braking force and service braking force is normally the greater. To establish the true retardations produced by the emergency brake, care should therefore be taken to ensure that the service brake is not inadvertently applied during the test.

4 All brake engines should be fitted with a pressure gauge so that there is a means of indicating or checking braking force.

Brake holding test (see paragraphs 18 and 19 of code)

5 The Special Regulations for Friction Winding Engines specify statutory requirements in respect of the holding power of the mechanical brake. Tests 1A and 1B are designed to check that the brake complies with these requirements.

6 Reference Test 1A which relates to balanced conveyances: where motor current does not reach a value corresponding to 2.5 times maximum static torque, it will be necessary to repeat this test with a loaded conveyance assisting the motor torque. The current required to be applied in the test with a loaded conveyance will be less than that equivalent to 2.5 times maximum static torque by an amount equivalent to the torque produced by the out of balance load. However the test with empty conveyances should always be carried out first as it will indicate if the brake is functioning.

7 Reference Test 1B which relates to a conveyance and counterweight: it is necessary to establish whether the total out of balance load when the conveyance is empty is different from that when it is fully loaded. If the out of balance load is greater when the conveyance is fully loaded but it is more convenient to carry out the test with the conveyance empty, the torque applied in favour of the counterweight should be 1.5 times the maximum static torque for the fully loaded conveyance plus the difference in out of balance torque between an empty and loaded conveyance.

8 Service braking force may have two levels: a low level immediately available; and a higher level which is available only when the winding engine is stationary or after a set time following full application of the service brake. Both levels of braking force should be checked; and the time between application of low and high levels measured and compared with the original settings in the Master Record.




Maximum static torque (see paragraph 18 of code)

9 The maximum static torque referred to in the brake holding tests is that value of torque developed by a winding engine motor which will just hold the maximum out of balance load stationary without using the winding engine brake. For this purpose the maximum load in a conveyance should be the man load or the most frequently wound mineral or materials load, whichever is the greater. Where balance rope and winding rope weights are unequal this should be taken into account as far as is practicable when maximum static torque is being determined. A measure of this torque should be obtained from the motor ammeter and recorder in the Master Record.

Protection against failure of brake pressure (see paragraph 20, Test 4, of code)

10 Where a brake engine is designed so that braking force is applied by air or oil pressure, additional provision is made for application of the brake should pressure fail. Arrangements vary with different designs of brake engine but all follow the principle of applying the brake by deadweights or springs after pressure failure.

11 The method of testing depends on the particular system but, basically, the test should prove that the back up gear operates and applies the mechanical brake in accordance with the design characteristics should the pressure of the operating fluid reduce to such a value that the main brake engine is not effective.

12 This part of the emergency braking facility may not regularly be used and/or may not normally be seen to function in isolation. Hence, when initially devising a testing procedure which requires the primary braking system to be held off, additional precautions should be taken to prevent uncontrolled drum movement in case of malfunction of the back up brake.

Application tests-emergency braking (see paragraph 20 of code)

13 Wherever possible a measure of emergency braking force at the brake engine should be made and the method for each winding engine approved by the senior engineer or official. For example, where brakes are applied by fluid pressure, it would suffice for a check to be made of pressures at each fixed level of braking. Where brakes are spring applied and pressure released, it may be necessary to take physical measurements in order to check any change in spring-rest setting with the brakes in the on positions. Residual pressure if any should also be noted when the emergency brake is applied.

14 Reference Test 5 (see paragraph 20 of code)-The safety devices to be tripped as required by Test 5 should be declared for each winding engine by the senior engineer or official. It is essential that the automatic contrivance overwind and overspeed switches be included and any other safety devices incorporated for overwind protection, such as brake overtravel switches. Test 5 can be carried out in a similar manner to Test 4; but it is satisfactory to check that the safety circuit is tripped without applying power to the winding engine motor.

15 It may be convenient, and in some instances advisable, for other electrical safety devices operating the safety circuit(s) to be tested at this time. This should be decided by the electrical engineer concerned. Such tests should be recorded in the manager’s scheme for the mine and can, if desired, form part of the six-monthly test record.




Operation of the automatic contrivance and determination of retardation rates

16 Paragraphs 16 to 32 of this appendix relate to testing of safety devices under running conditions.

Time delays

17 When carrying out periodic check tests it is necessary to obtain the time delay from initiation of an overspeed trip to full application of the mechanical brake. Should a test indicate that this time lag has increased so as to affect safety, it will be of some assistance in locating the cause if the various component times, making up the total time, are known. It is therefore recommended that, when a winding engine is commissioned, measurements should be taken of those component operating times that can reasonably be measured. (See paragraph 21 of code).

Brake retardations (see paragraphs 21 and 22 of code)

18 Reference Test 6-After carrying out the brake holding test and other preliminary check tests, retardation tests with empty conveyance(s) are required before other dynamic tests to establish that the safety equipment is functioning correctly, that brake time delays and retardations are of the right order and that slip is not likely to occur. Also, if is necessary to correct the retardations, adjustments made at this stage may avoid the necessity to repeat tests.

19 Reference Test 7-This test is to check if the retardation with a man load complies with the requirements of the Special Regulations; it should normally be carried out at one half maximum winding speed. This test is optional because it is desirable to keep the number to a minimum as excessive testing can lead to high brake path temperatures. These temperatures can cause loss of retardation during testing, particularly on those friction winding engines with brakes designed to dissipate energy at about twice the rate normal for drum winding engines. It may therefore be preferable to check the retardation during the characteristic trip curve tests to limit the number of tests. A trip curve is normally recorded on a velocity/distance basis but retardation should be recorded on a velocity/time basis so that changes in retardation can more easily be recognised. A velocity/time retardation trace is ideally a straight line, but as it is usually of a wave form it is necessary to determine the average retardation by drawing a straight line through the trace. (See appendix 32.3, fig 32.2). This value of retardation should be recorded on the test certificate.

20 It is possible that the rates of retardation obtained in Test 7 will slightly differ from one six-monthly test to another. Where these differences are due to normal variation in the coefficient of friction between brake lining and brake path, it is unnecessary to make compensating adjustments to the braking torque provided that the retardations comply with regulations. The retardations should ideally be set in the middle of the permissible range of retardation so that any such variations can easily be accommodated.

21 Commissioning or subsequent comprehensive tests are carried out on winding engine safety equipment under all anticipated loading conditions including man loads and the results form part of the Master Record. During comprehensive tests, rates of retardation obtained with other loads such as a coal load have a direct relationship with rates obtained with a man load; and provided the corresponding brake pressures remain the same this relationship should stay unchanged. It should therefore not be necessary to carry out routine tests with a coal or similar load in addition to man load tests.




Acceleration and trip characteristic tests (see paragraphs 21 to 23 of code)

22 The first dynamic test is a trip at about 8 ft/sec (2.5 m/sec) and is to check operation of the safety equipment at a safe speed before commencing acceleration tests.

23 The acceleration tests are designed to ensure that the equipment complies with the requirements of Regulation 19(4)(b) of the Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960 as varied by Special Regulations for Friction Winding Engines. These tests of the safety equipment are the most onerous in determining the maximum landing speed. As indicated in the text, to produce maximum acceleration, power has to be built up before or after the brake is released; if the latter, then maximum power should be applied when the winding engine is moving. It is only necessary to carry out the test found to be the more onerous.

24 Reference is made in the text to carrying out tests at appropriate distances within one drum revolution of the artificial landing. For guidance, it is suggested that these be at approximately 1.0, 0.75, 0.5 and 0.25 drum revolutions from the artificial landing and thereafter at decrements of 3 to 6 ft (1 to 2m) towards the artificial landing. It should be appreciated that the positions indicated above are not rigid requirements and, in general, acceleration tests from positions within the last revolution of the drum are all that is required and the number of tests should be kept to a minimum. If a winding engine is fitted with acceleration relief on the overspeed mechanism of the automatic contrivance, it is necessary to check that this feature does not allow an excessive speed towards the landing owing to lag in the mechanism after changing direction.

25 The trip characteristic of the automatic contrivance is the curve indicating winding speed at which the safety circuit trips at various positions of the conveyance relative to both ends of the wind.

26 During commissioning or subsequent comprehensive tests the full trip curve is established, but at a six-monthly test it is sufficient to prove the curve in relation to speed and distance from the landing by using a minimum number of trips. Trip speeds and distances at the six-monthly tests should be varied so that the full characteristic is adequately verified.

27 After the acceleration tests in Test 9 have been completed, the first test in Test 10 should be at a speed in excess of the speed recorded from one drum revolution and is the first of the tests for proving the trip curve. About three tests are then carried out, the last being at the maximum possible winding speed when the automatic contrivance is in the man winding position.

28 The method of achieving this maximum possible winding speed will need to be determined for each winding engine and approved by a senior engineer or official. On some electric winding engines it can be achieved by accelerating the loaded conveyance down the shaft until normal maximum speed is reached, and then by removing power from the motor allowing the out of balance load to accelerate the winding engine until an overspeed trip occurs at the maximum speed permitted by the automatic contrivance. Preferably the trip should occur just before the retardation part of the trip curve is reached. Experience and knowledge of a particular installation will indicate the point in the wind at which this test should start and the position in the wind at which power should be removed from the motor in order to achieve such an overspeed trip. Consecutive tests of this type should not be carried out to try to make the overspeed trip coincide with commencement of the retardation part of the wind, as this may cause over heating of the brake paths.




It is preferable to establish the ideal starting point during a series of six-monthly statutory tests. If an overspeed trip is not obtained before the retardation part of the wind is reached because out of balance load does not produce sufficient accelerating torque, or if there is not adequate accelerating distance due to shallow depth of shaft, then the overspeed trip which occurs at the commencement of the retardation period should be recorded as the maximum possible winding speed. On AC and DC winding engines with closed-loop electrical control it will be necessary to provide an overspeed test switch to enable this test to be carried out. Completion of this series of tests in the manner described should enable the trip curve to be adequately verified.

Maximum power torque (see paragraph 22, Test 9, of code)

29 A number of tests require that maximum power torque to be applied to the winding engine drum or sheave. This is not necessarily the maximum torque of which the winding engine is capable and note should be taken of the following paragraphs.

30 Where electric winding engines incorporate closed-loop control, a limiting device which determines the maximum torque is invariably incorporated. If a torque limiting device is not used, the test should be carried out at a current corresponding to 1.1 times the maximum torque required in service for normal duties, taking into account any permissible variation in loading conditions. Where the motor(s) will not develop 1.1 times this maximum torque or where a torque limiting device is fitted, the maximum torque that is available to the winding engineman should be used for the test. In any case maximum torque at standstill should only be applied for a very short time to avoid damage to the winding engine motor(s).

31 For purposes of test, the winding engineman’s ammeter reading corresponding to maximum torque for normal duties should be established; maximum torque does not usually occur at maximum stator current with AC induction motors although armature current can be considered as a direct measure of torque with DC winding engine motors. Open-loop Ward Leonard winding engines should be examined and, where necessary, current limit devices fitted or the setting of existing devices checked.

Combined electrical and mechanical braking on Ward Leonard winding engines

32 There are various arrangements for initiating retardation under trip conditions on Ward Leonard winding engines but, whatever the arrangements, some electrical effect will be present which may assist or oppose the mechanical brake. Wherever possible, the control should be set such that following an emergency trip, minimum electrical braking occurs when the mechanical brake is fully applied and effective with the maximum load descending and the conveyance near the bottom landing. At commissioning, tests should be carried out to ensure that the mechanical brake will protect the winding engine with zero electrical torque. At this time the separate and combined effects of mechanical and residual electrical braking should be clearly identified and recorded as standards. At a six-monthly test the combined effect can then be compared with the commissioning standard. The procedure for this test should be agreed by a senior engineer or official before any such tests are carried out, and should form part of the Master Record.

Detection of rope slip (see paragraph 14(6) of code)

33 It is necessary to detect any rope slip that occurs during testing. One method of doing this is to mark the rope(s) before testing with tape at a position which coincides with a mark on the drum or sheave and corresponds to a mark on the




depth indicator. At any time during testing when it is suspected that rope slip has occurred, and always at the completion of testing, the relationship of the three marks should be checked . A convenient time for marking and checking for rope slip is when setting and removing the artificial landing. An accumulation of rope creep can be detected by the same method.

Overwind setting (see paragraph 24 of code)

34 The position of the overwind switch of trip above bank will depend upon the distance that it is necessary to raise the conveyance above the landing during normal winding operations. The switch or trip device should be set to operate at the minimum overwind distance commensurate with normal manoeuvring requirements.

Appendix 32.2 Setting an artificial landing

1 Three methods of setting up an artificial landing are indicated below.

2 Where the automatic contrivance is fitted with moveable cam dials for each conveyance, Method 1, which avoids uncoupling the drive, should be used.

3 For other automatic contrivances, Method 2 or 3 should be used but additional protection should be afforded for the loaded conveyance when ascending. For this purpose it is suggested that, during testing, a limit switch be introduced into the trip circuit and so arranged to operate when the loaded conveyance required is at a distance from the highest landing equal to the distance required for normal retardation from maximum speed. Wherever possible Method 3 should be avoided because of the danger of moving the winding engine without protection.

Method 1

4 Place the declared test load in one conveyance (see paragraphs 9 and 10 of code).

5 Wind the loaded conveyance to the lowest level and stop it at the normal landing position. Suitably mark the sliding part of the automatic contrivance cam dial in relation to the non-sliding part. Note the clearance between the overwind cam and its roller at the shaft bottom position. Wind the conveyance about ten completed drum turns up the shaft; loosen the sliding part of the dial and move it bodily, complete with the cams, to its shaft bottom position. The dial should then be made secure and temporary marks put on the ropes, depth indicator and drum showing the position of the artificial landing. It is normal practice to mark the drum relative to a fixed point as a check and to facilitate resetting. The setting of the overwind switch should then be checked by slowly lowering the loaded conveyance until an overwind trip occurs.

6 The procedure of resetting to the normal landing is as follows. Wind the conveyance to the artificial landing. Loosen the sliding part of the dial and turn it until the marks on both the sliding and the non-sliding parts of the dial coincide. Secure the two parts together and remove the temporary marks on the ropes, depth indicator and drum. Instruct the winding engineman to wind SLOWLY to the rope creep compensating position and compensate if necessary. Check the setting of the dial on the automatic contrivance which refers to the conveyance just tested and, if necessary, wind this conveyance to the other end of wind to enable this to be done. Test the overwind trips as described in Test 11 (see paragraph 24 of code).




Method 2

7 Place the declared test load in one conveyance (see paragraphs 9 and 10 of code)

8 Wind the loaded conveyance to the lowest level and stop it at the normal landing position. Suitably mark the two halves of the drive coupling nearest to the automatic contrivance relative one to the other and with reference to a fixed point. Wind the conveyance about ten completed drum turns up the shaft noting the number of revolutions of the automatic contrivance coupling. Uncouple the drive and reset the automatic contrivance by hand, turning back the same number of revolutions to the fixed mark previously made, and reconnect the coupling. This position may now be regarded as the artificial landing and temporary marks should be made on the ropes, depth indicator and drum. It is normal practice to mark the drum relative to a fixed point as a check and to facilitate resetting. The setting of the overwind switch should be checked by slowly lowering the loaded conveyance until an overwind trip occurs.

9 The procedure for resetting to the normal landing is as follows. Wind the conveyance to the artificial landing, uncouple the drive and reset the automatic contrivance by hand until the marks on the two half couplings coincide, making sure that the number of revolutions of the automatic contrivance half-coupling is the same as that previously noted when setting the artificial landing. Reconnect the coupling and remove the temporary marks on the ropes, depth indicator, drum and coupling. Instruct the winding engineman to lower the conveyance SLOWLY to the rope creep compensating position and compensate if necessary. Check the setting of the dial on the automatic contrivance which refers to the conveyance just tested and, if necessary, wind this conveyance to the other end of the wind to enable this to be done. Test the overwind trips as described in Test 11 (see paragraph 24 of code).

Method 3

10 Place the declared test load in one conveyance (see paragraphs 9 and 10 of code).

11 Wind the loaded conveyance to the lowest level and stop it at the normal landing position. Disconnect the drive to the automatic contrivance, suitably marking the halves of the coupling where the drive is split and marking the drum relative to a fixed point. Wind the conveyance about ten completed turns up the shaft using the drum mark. Re-couple the automatic contrivance drive using the marks.

12 This position may be regarded as the artificial landing and temporary marks should be made on the depth indicator and ropes. During movement of the winding engine with the drive uncoupled the winder testing engineer should be in a position to operate the emergency trip in case the winding engineman attempts to wind in the wrong direction. The setting of the overwind switch should be checked by slowly lowering the loaded conveyance until an overwind trip occurs.

13 The procedure for resetting to the normal landing is as follows. Wind the conveyance to the artificial landing and disconnect the drive to the automatic contrivance. Wind the conveyance SLOWLY down to the normal landing. The automatic contrivance drive is then reconnected at the correct marks. During this movement of the winding engine, the winder testing engineer should be in a position to operate the emergency trip in case the drum moves in the wrong direction, moves too fast, or travels beyond the normal landing. Remove the temporary marks on the depth indicator, drum, coupling and ropes. Wind the conveyance SLOWLY to the normal rope creep compensating position and compensate if necessary. Check the setting of the dial on the automatic




contrivance which refers to the conveyance just tested. If necessary, wind this conveyance to the other end of wind to enable this to be done. Test the overwind trips as described in Test 11 (see paragraph 24 of code).

General

14 The speed control cam gear used on older type open-loop Ward Leonard winding engines is usually an essential part of the overspeed protection system. Thus, although this cam gear is not in operation when carrying out the automatic contrivance characteristic tests, it is necessary for it to be set to the artificial landing for the acceleration tests.

APPENDIX 32.3 Record of tests




60 ft/sec 60 ft/sec

12 ft/sec

0 ft/sec 0 ft/sec6 rev 4 rev

Overspeed tripindications

Distance scale 1 cm = 10 ftAcceleration

tests2 rev 1 rev

Mid shaftoverspeed

Star

t of r

etar

datio

n ca

m o

n au

tom

atic

con

triva

nce

Velo

city

sca

le 0

-60

ft/se

c

Velo

city

sca

le 0

-60

ft/se

c

Full motor overspeedLoad descending

Automatic contrivance trip curve tests:velocity/distance

Firs

t lan

ding

spe

ed te

st -

little

or n

o po

wer

Test

in w

rong

dire

ctio

n

Artifi

cial

land

ing

10 d

rum

revs

. fro

m p

it bo

ttom

Collierywinding enginedate of testdirection of test

30 ft/sec 30 ft/sec0.15 sectime lag

0.15 sectime lag

0.15 sectime lag

0 ft/sec 0 ft/secLower limit

Tripindication

Tripindication

Tripindication

Upper limit

Upper limit

Retardation tests velocity/time

Empt

y cag

es m

id-sh

aft f

orwa

rd g

ear

8.8 ft

/sec

2

Upper limit

Velo

city

sca

le 0

-30

ft/se

c

Velo

city

sca

le 0

-30

ft/se

c

Lower limitTime scale 1 cm = 0.25 secs

Note:The average retardation should be obtained by taking the average ofretardation trace between selected upper and lower limits.The UPPER LIMIT will normally be the point of first aplication of thebrake but may be modified to exclude initial transient peaks.The LOWER LIMIT will normally be the lowest point of the trace,neglecting any effect of brake fade.The trace should be compared with the master record, particularlythe trace peaks and their duration.

Lower limit

Empt

y cag

es m

id-sh

aft b

ackw

ard

gear

Load

ed ca

ge de

scen

ding

8.1 ft

/sec2

5.8 ft/

sec2

Figure 32.1 Typical graph of six monthly dynamic tests on friction winding engine

Figure 32.2 Typical graph of six monthly dynamic tests on friction winding engine




APPENDIX 32.4 Overspeed contacts: conditions to satisfy paragraph 21 of code

1 In order to carry out tests required by the model code the precise instant of opening of the overspeed switch is required to be known, and also that it is this switch that has tripped the safety circuit and caused the mechanical brake to be applied.

2 The conditions relating to the use of this switch for this purpose are laid down in paragraph 21 of the model code. These conditions are necessary to maintain the integrity of the switch and associated circuitry. This circuit responds to malfunction of the winding engine speed control system whether manual or automatic. A method of complying with the requirements of paragraph 21 of the code is suggested below.

3 A high resistance interposing relay may be connected across the overspeed switch in the following manner. Two resistors of high integrity, each mounted on its own insulating board, attached to a metal plate and adequately protected by a metal cover, should be used for connecting into the leads from the overspeed switch to the relay, one resistor in each lead. The resistors should be of such value that, when connected in series across the overspeed contacts, the current in the safety circuit is reduced to about 10% of the current required to hold in (not close) the safety circuit contactors.

4 For reasons of robustness and reliability, the resistors should be of a vitreous coated wire wound type, and at least 3 watts rating or 3 times the wattage required by the rating of the circuit whichever is the greater.

5 Reliance should not be placed on the wire connections of a resistor as the sole means of its support. The body of a resistor itself should be held by a suitable clamp.

6 The purpose of mounting the resistors on separate insulating boards on a metal plate, which should be earthed, is to ensure that a fault will be an earth fault rather than a short circuit.

7 The leads from the overspeed contacts to the resistors should be as short as is practicable and should be screened, as are the cables in this section of the safety circuit, unless the leads are so short that high integrity is maintained by disposition and clamping. The leads to the interposing relay need not be screened as a short circuit at this point would not interfere with the operation of the safety circuit.

8 The interposing relay should be incorporated into the automatic contrivance so that there is not live contact on the socket outlet to be used for the connections required to the test equipment.

9 The above arrangement is one method of achieving the required integrity, others could be equally acceptable but should be at least to the same level of integrity.




APPENDIX 32.5 Draft Local Regulations which the Secretary of State Proposes to make, published under the Mines and Quarries Act 1954

DRAFT STAUTORY INSTRUMENTS

19 No.

MINES AND QUARRIES

The Mine (Friction Winding) Local Regulations 19 __

Made 19 __

Coming into operation 19 __

The Secretary of State in exercise of his powers under sections [47]* 141 and 143 of the Mines and Quarries Act 1954(a), and of other powers in that behalf enabling him hereby makes the following regulations:

Citation and commencement

1 These regulations may be cited as the _______ Mine (Friction Winding) Local Regulations 19 __ and shall come into operation on _______

Interpretation

2 (1) In these regulations the following expressions have the meanings hereby respectively assigned to them, that is to say-[‘the Act’ means the Mines and Quarries Act 1954]* ‘cage’ includes the skip; ‘the general regulations’ means the Coal and Other Mines (Shafts, Outlets and Roads) Regulations 1960(b); ‘the mine’ has the meaning assigned thereto in regulation 3; ‘friction winding apparatus’ and ‘shaft’ have the meanings assigned thereto in regulation 4(1) and (2) respectively.

(2) The Interpretation Act 1889(a) shall apply to the interpretation of these regulations as it applies to the interpretation of an Act of Parliament.

Application 3 These regulations shall apply to the _______ Mine at _______ in the county of (in these regulations referred to as ‘the mine’).

Friction winding apparatus

4 (1) The manager of the mine shall ensure that no winding apparatus thereat operated by means of the friction of a rope on a winding sheave (in these regulations referred to as ‘friction winding apparatus’) is used in any shaft in the mine except in compliance with the provision of these regulations.

* To be included only whenautomatic operation is contemplated




(2) Any reference in these regulations to a ‘shaft’ shall be construed as a reference to a shaft which is provided with friction winding apparatus.

Keps

5 Notwithstanding anything in regulation 15 of the general regulations (which relates to keps) keps shall not, except with the consent of an inspector served by notice on the manager of the mine, be provided in a shaft for use with any friction winding apparatus.

Overwinding

6 (1) There shall be provided at every shaft, in the headframe and in the part of the shaft below the lowest entrance for the time being in use, apparatus so designed and constructed as to secure that, so far as is practicable, any cage or counterweight of the friction winding apparatus which has been overwound is brought to rest without danger.

(2) There shall be provided in the headframe of every shaft safety devices so designed and constructed as to prevent, while persons are being carried, a cage or counterweight of the friction winding apparatus which [has been brought to rest by]1 [has reached the upper limit of] 2 the apparatus provided in pursuance of paragraph (1) of this regulation falling down the shaft,

(3) Regulation 16 of the general regulations (which relates to detaching gear) shall not apply to any friction winding apparatus.

Speed of landing

7 Regulation 11(1)(a) of the general regulations (which relates to the speed of landing of a descending cage) shall be varied in its application to every friction winding apparatus by the deletion therefrom of the words ‘or the bottom of’ and by the substitution therein of the words ‘twelve feet per second’ for the words ‘five feet per second’.

Brakes

8 (1) Every friction winding apparatus shall be provided with one or more brakes which:

(a) howsoever applied will act directly on the winding sheave or sheave shaft;

(b) where applied by a means provided for use by the person operating the friction winding apparatus being a means which enables that person to vary the braking torque applied thereby, will be capable of holding the winding sheave or sheave shaft (as the case may be) stationary when a torque is applied to the sheave shaft of two and a half times the maximum static torque which will be applied thereto:

(i) While persons are being carried by the apparatus; or

(a) 1954c.70 (b) S.I.1960/69 (1) Applicable to all new installations and to all existing installations which are equipped with sets of cage catches operating at more than one level. (2) Applicable only to existing installations which are equipped with a set of cage catches operating at a single level.




(ii) in the course of normal operation while the mineral or material most frequently carried by the apparatus is being carried thereby whichever is the greater;

(c) where applied by a means to which the last preceding sub-paragraph does not apply will-

(i) while persons are being carried by the apparatus and before the winding sheave has been brought to rest, produce a braking torque which will reduce the speed of the ropes on the winding sheave at a rate of not less than three feet per second but not exceed the greatest torque which would not cause any winding rope to slip while the apparatus is being used;

(ii) in the course of normal operation while the mineral most frequently carried by the apparatus is being carried thereby and before the winding sheave has been brought to rest, produce a braking torque which will reduce the speed of the ropes on the winding sheave at a rate of not less than one and a half feet per second per second but not exceed the greatest torque which would not cause any winding rope to slip while the apparatus is being used in the course of such operations as aforesaid.

(iii) when the winding sheave has been brought to rest, produce a braking torque not less than that specified in provisions (i) and (ii) of this sub-paragraph for application when the apparatus is carrying persons, or mineral or materials, as the case may be.

(2) For the purpose of the preceding paragraphs a means of braking shall not be deemed to enable a person operating the friction winding apparatus to vary the braking torque applied thereby by reason only that that person can select one of two braking torques one of which is to be used when the apparatus is carrying persons and the other of which is to be used when the apparatus is carrying minerals or materials.

(3) For the purposes of paragraph (1) of this regulation the greatest torque which would not cause any winding rope to slip shall be calculated upon the assumption that the coefficient of friction between the winding ropes and the winding sheaves is 0.2 or such other value as an inspector may specify in a notice served on the manager.

(4) Each person operating any friction winding apparatus shall ensure that, while persons are being carried or are about to be carried, every brake provided in pursuance of paragraph (1) of this regulation is fully applied immediately after any cage of the apparatus stops at any landing of or entrance to the shaft and is kept so applied until the appropriate signal to raise or lower the cage, as the case may be, has been transmitted to him.

(5) Regulation 9(1) of the general regulations (which relates to brakes) shall not apply to any friction winding apparatus.

Stop switch

9 Every electrically driven friction winding apparatus shall be provided with a stop switch for the purpose of stopping the winding engine, being a switch-

(a) Placed within easy reach of the person operating that engine; and




(b) so designed and constructed as to ensure that when it is operated for the purpose aforesaid-

(i) the supply of electricity to that engine, other than any for the purposes of braking it, will be immediately cut off; and

(ii) the brakes provided in pursuance of regulation 8(1) will be applied.

Winding and balance ropes

10 (1) Each set of winding ropes used to suspend a cage in any friction winding apparatus shall have a combined braking strength when first installed of not less than F1 times the maximum static load that the ropes may be required to carry while persons are being carried, or F2 times the maximum static load that the ropes may be required to carry while carrying the mineral or material they will most frequently carry, whichever is the greater, where the factors F1 and F2 are calculated in accordance with the appropriate formula contained in the schedule to these regulations.

(2) Regulation 17(2) of the general regulations (which relates to winding ropes) shall be varied in its application to each winding rope installed in any friction winding apparatus by the substitution therein of the words ‘two years’ for the words ‘three and a half years’.

(3) No rope shall be used as a winding rope in any friction winding apparatus which has previously been used as a balance rope.

(4) Regulation 17(3) of the general regulations shall not apply to any winding rope used in any friction winding apparatus.

11 (1) No spliced rope shall be used as a balance rope in any friction winding apparatus.

(2) No rope shall be so used if it has been used either as a winding rope or balance rope, or as the former and then the latter, for a period of three years or more. Provided that if an inspector having regard to the condition of the rope and to the extent to which and the circumstances in which it has been used is satisfied that it can be used as a balance rope without danger, he may by notice served on the manager of the mine authorise such use of that rope for such further period as may be specified in the notice.

(3) Each balance rope when first installed in any friction winding apparatus shall have a breaking strength of not less than six times the weight of the rope.

Cappings of winding ropes

12 (1) A winding rope which has been re-capped shall not be used in any friction winding apparatus as such unless on the last occasion on which it was re-capped the capping was moved a distance of not less than six inches along the rope towards its other end; Provided that an inspector may by notice served on the manager of the mine exempt any such rope thereat from the provision of this paragraph.

(2) Regulation 67(1) of the general regulations (which relates to re-cappings) shall not apply to any such rope.




(3) Regulations 67(2) of the general regulations shall be deemed to apply to any length of such rope which is cut off when a capping is moved as aforesaid, other than a length which was enclosed by a white metal capping before it was so moved.

Construction of cages and counterweights

13 (1) Every main suspension member of every cage of any friction winding apparatus shall have a breaking strength of not less than seven times the maximum static load that may be imposed thereon when the apparatus is carrying either the maximum load of persons which it may be required to carry or the maximum load of the mineral or materials which it most frequently carries whichever is the greater.

(2) Every main suspension member of every counterweight of any friction winding apparatus shall have a breaking strength of not less than seven times the load that will be imposed thereon when the counterweight is at the highest position that it normally reaches in the shaft.

Safety devices while persons are being carried

14 Every friction winding apparatus shall be provided with an effective automatic device which shall operate while the apparatus is being used for the carriage of persons and shall be so designed and constructed as to ensure that the winding engine cannot be set in motion when-

(a) any cage of the apparatus is stationary at a landing or entrance which is used by any person at the beginning or end of a shift;

(b) the appropriate gate or enclosure provided at the landing or entrance is wholly or partly removed or open; and

(c) the brakes provided in pursuance of Regulation 8(1) are fully applied.

Operation of friction winding apparatus

15 All gear provided for the control of friction winding apparatus shall be so designed and installed that while the friction winding apparatus is being used for the carriage of persons the winding engine will not respond to control gear installed at more than one place.

Provided that nothing in this paragraph shall be construed as applying to any emergency stop switch whether or not provided in pursuance of Regulation 9.

Fire precautions

16 (1) In every case where the winding engine of any friction winding apparatus is situated in the headframe of a shaft so far as is practicable effective measures shall be taken to prevent any inflammable liquid used in connection with the winding engine or any apparatus installed in the headframe escaping into the shaft.

(2) In every such case where the winding engine is not attended by the person operating it there shall be provided-

(a) apparatus which will in the event of an outbreak in the headframe of fire which might develop so as to endanger or affect the operation of the




friction winding apparatus, automatically give warning to that person and to the banksman; and

(b) in the headframe sufficient and suitable means of extinguishing any such fire.

Maintenance

17 Regulation 19(4)(b) and Regulation 19(5)(b) of the general regulations (which relate to maintenance of winding apparatus) shall be varied in their application to every friction winding apparatus by the substitution of the words ‘six months’ for the words ‘three months’ in regulation 19(4)(b) and of the words ‘twelve months’ for the words ‘six months’ in regulation 19(5)(b).

Change of friction winding apparatus

18 Section 43(1) of the Act (which relates to the charge of winding apparatus when persons are not carried) shall not apply to any friction winding apparatus while it is being used for carrying loads other than person and its operation is wholly automatic.

Dated ___________________________ 19 __

Health and Safety Executive Reg. 10(1)

Schedule

Formulate for calculation of safety factors of winding ropes

Where-

F1 = the factor of safety while persons are being carried;

F2 = the factor of safety while the mineral or material which the apparatus most frequently carries is being carried;

R = the ratio of the diameter of the winding sheave to the diameter of the winding ropes;

C = 35 where there is not a nearby deflecting sheave, or 43 where there is a nearby deflecting sheave; and

L = the vertical distance in feet between the level of the top of the highest winding sheave and the level at which the winding ropes meet the suspension gear of the cage when at its lowest position in the shaft.

F1 = 1.0+

F2 =R(1 + 0.0028 L) - 13.5

4.5 (R + C)

R(1 + 0.0028 L) - 13.5

4.5 (R + C)




DRAFT STAUTORY INSTRUMENTS

19 No.

MINES AND QUARRIES

The Mine (Friction Winding) Local Regulations 19 __

Made 19 __

Coming into operation 19 __

The secretary of State in exercise of his powers under sections 141 and 143 of the Mines and Quarries Act 1954(a), and all other powers in that behalf enabling him hereby makes the following regulations:

1 These regulations shall come into operation on _________ 19 __ and may be cited as the __________ Mine (Friction Winding) (Amendment) Local Regulations 19 __

2 The Interpretation Act 1889(b) shall apply to the interpretation of those regulations as it applies to the interpretation of an Act of Parliament.

3 These regulations shall apply to the _________ Mine at __________ in the county of _______________

4 (1) The __________ Mine (Friction Winding) Local Regulation 19(c), (in these regulations referred to as ‘the principal Regulations’), shall have effect subject to the variation specified in this regulation.

(2) After regulation 12(3) of the principal regulations there shall be added the following paragraphs:

‘12(4) No rope which has been properly cut to length, capped and placed in store in a suitable place shall be used in any friction winding apparatus for more than six months without first being re-capped and subsequently being re-capped at intervals not exceeding six months.

12(5) Regulations 65(1) of the general regulations shall not apply to any such rope.’

Dated _________ 19 __


(a) 1954 c.70 (b) 1889 c.63 (c) S.I. 1963/1566




Glossary Definition of terms as used in this report in addition to those in the glossary in Part 1A.

Accelerometer An instrument for measuring rate of change of velocity. Traces obtained from accelerometers in conveyances are used to investigate shocks and vibrations rather than steady accelerations and decelerations.

Airlock A system of doors arranged to allow passage of men or vehicles through it without permitting significant air flow.

Analogue Analogous representation of quantities by other continuously varying quantities such as electric currents or voltages.

Bank The decking level at a shaft top.

Bind Shale or mudstone occurring in coal measures.

Bunton One of a series of horizontal beams set at intervals across a shaft to support rigid guides, cables and pipes.

Bush The inserted lining of a bearing in which a shaft or pin rotates.

Byatt An alternative word for bunton.

Capacitor A device which gives a circuit a capability of storing electrical energy: capacitance of such a device is defined as the quotient of its positive charge divided by the potential difference between its conductors.

Clunch A clay like rock occurring in coal measures.

Compliance The extension, compression or distortion of a component per unit of force applied to it.

Corrosion fatigue Acceleration of weakening of metal components exposed to pulsed stress, by corrosive attack.

Creep 1 The small relative movement which occurs between the winding rope(s) and friction treads of a friction winding engine during normal winding operations.

2 A low winding speed normally employed just prior to stopping.

Crib A ring of iron, timber or concrete set so as to form the foundation of a section of walling in a shaft.

Cryogenic power pack A source of pneumatic power using liquid nitrogen.




DC to AC converter Static apparatus for converting direct current to alternating current, particularly in cases where alternating operating current is required from a storage battery.

Decelerometer As accelerometer.

Deflector pulley A pulley in a tower of a winding installation to align a winding rope vertically with a conveyance.

Detaching plate or bell Apparatus in a headframe which operates a detaching hook in the event of an overwind, and from which the detached conveyance is suspended when not supported by safety catches.

Digital Codified representation of quantities by discrete pulses in electric circuits.

Drift An underground roadway driven from the surface, or across strata below ground.

Emergency brake solenoid An electrical device which, when de-energised, initiates emergency application of the mechanical brake of a winding engine.

Fillet weld A weld at the junction of two parts at right angles to each other, in which a fillet of welding metal is laid down in the angle created by the intersection of the surfaces of the parts.

Finite element method A method of stress analysis in which a structure isof analysis considered as separate elements.

First man in The first person to be wound to an unmanned landing, for the safety of whom special provision is made.

Flashover An arc or spark between electrical conductors or between an electric conductor and earth.

Flood lubrication Lubrication for a bearing supplied in excess by a pump or other means.

Flux gate magnetometer A device for measuring intensity of a magnetic field by means of a magnetic reproducing head.

Fracture mechanics The study of fracture of bodies, in relation to flaws in them and forces acting on them.

Fracture toughness A measure of the resistance of a material to fracture in the presence of a flaw or discontinuity.

Frequency spectrum An arrangement of components of a complex sound in order of frequency.

Full penetration weld A weld resulting from a technique which ensures that welding metal fully penetrates the joint with complete roof fusion.




Garland A channel fixed around the lining of a shaft to catch water draining down and conduct it to pipes or water boxes.

Hysteresis The lagging of an effect behind a change in the mechanism or force causing the effect.

In-line gear Apparatus which prevents operation of decking and associated equipment at a landing in a shaft until a conveyance is substantially in line with the landing.

Inset An opening or entry from a shaft to an underground roadway or chamber.

Last man out The last man to be wound from a landing, for the safety of whom special provision is made.

Lay The direction in which the strands of a steel wire rope are spun.

Liquid controller A variable resistance in the rotor circuit of an induction motor, using a liquid as the resistive medium, for control purposes.

Locked coil rope A rope comprising one strand containing as many steel wires as are necessary to give the required diameter and rope strength. Intermediate layers are composed of either round wires or a combination of round and shaped wires. The outermost layer, always composed of full lock wires, is normally laid in the opposite direction to the one beneath.

Microprocessor Part of a miniaturized computer containing a few discrete elements, where the central processing unit is a single small chip of semiconductor material.

Motor-generator set A set comprising one or more motors mechanically coupled to one or more generators: as used for converting AC to DC in a Ward Leonard winding engine.

National Coal Board A standard purchase specification issued by theSpecification National Coal Board.

Notch ductility Susceptibility to fracture due to weakening effect of a surface discontinuity, as disclosed by Izod or Charpy test.

Oil ring lubrication Lubrication of a bearing by means of metal rings supported on the journal and running in a sump containing oil.

Optical coupling Transfer of a signal from one electrical system to another by optical means without direct electrical connection between the two systems.

Optical plummet An optical device designed to enable a theodolite to be accurately positioned over or under a survey station.




Overwind safety catches Catches or equivalent devices provided in headframes to prevent conveyances from falling back an excessive distance after an overwind, independent of the suspension gear.

Piezo-resistive An effect brought on in certain crystals of change of intensity of static-electrification field with mechanical pressure.

Radio metal An alloy of permalloy type used because of high magnetic permeability and low hysteriesis loss.

Rapper A signal key, each operation of which initiates a single pulse.

Receiver guides Wooden or steel guides with ends shaped to lead in and locate a conveyance at decking levels.

Rectifier tanks Gas filled rectifiers for converting AC to DC in which current flows through ionized mercury vapour.

Rubbing ropes Ropes hung in a shaft between the paths of conveyances to prevent their collision.

Semi-automatic In the case of winding installations: winding between predetermined levels in a shaft without intervention by the winding engineman, with initiation of a wind by pushbutton from appropriate landings.

Slip Abnormal relative movement between the winding rope(s) and friction treads of a friction winding engine.

Shaft guides An arrangements of girders, rails, wooden rods, or ropes, disposed in a shaft to restrict lateral movements of conveyances.

Shaftsman A person employed in the equipping, inspection, maintenance and repair of shafts and shaft furnishings.

Tackiness The property of being slightly sticky and adhesive.

Tensometer A device for measuring tension in a moving steel wire rope by passing the rope through a system of rollers.

Tilting toe A pivoted end on a retractable platform to allow a descending conveyance to pass between platforms if they are inadvertently in the down position.

Time division multiplex A device or process for the transmission of two orcoding more signals over a common path by using successive

time intervals for different signals.

Torque wrench A device for applying a known torque to a nut.

Tower In the case of winding installations: a structure, immediately over a shaft, in which a winding engine is installed.




Unity gain amplifier A device for transposing electric signals from one circuit to another separately powered circuit without direct electrical connection and without magnification of the signals.




Appendix Sub-committees/Working groups/Drafting panel The constitution of the above bodies for the second report was as follows:

Member Official designation Organisation*

Sub-committee 1-(Mechanical engineering)

J B Hall (Chairman) Chief Mechanical Engineer NCB

T K Clanzy HM Principal Inspector of Mechanical HMI M & Q (Deputy Chairman) Engineering in Mines and Quarries

J W Barnes Head of Engineering Services, (Major Projects) NCB

JA Feirn Area Chief Engineer, South Notts NCB

E H Hands Joint Managing Director Blacks

A G Harley Deputy Chief Mechanical Engineer NCB

H M Harrison Mechanical/Electrical Inspector NUM

L C James Head of Technical Services Division MRDE

R W Latham Section Engineer GEC

E Loynes Representative AMEME

H D Munson Head, Engineering Group SMRE

P Wood Head of HQ Shafts and Winding Section NCB

G Scott (Secretary) HM District Inspector HMI M & Q

Working Group 1B

J W Barnes Head of Engineering Services (Major Projects) NCB(Chairman)

R Chadwick Services Engineer, Western Area NCB

A M Hepburn HM Inspector of Mechanical Engineering HMI M & Q

C H H Corden Senior Scientific Officer SMRE


R Newsham Senior Test Engineer, Mechanical MRDE

* See List of Abbreviations at the end of this Appendix





R A Smith Deputy Chief Maintenance Engineer NCB

P Wood Head of HQ Shafts and Winding Section NCB

T B Hinds (Secretary) Engineering Secretariat NCB

Working Group 1D

A G Harley (Chairman) Deputy Chief Mechanical Engineer NCB

H Andrews Manager Westinghouse

E A Barnes Mechanical Engineer, NCB HQ Shafts and Winding Section

R Hathaway Director and Chief Engineer Qualter, Hall

D W Neville Operations Engineer, HQ (Mechanical) NCB

W G Williams HM Inspector of Mechanical Engineering HMI M & Q

T B Hinds (Secretary) Engineering Secretariat NCB

Sub-committee 2-(Electrical engineering)

R Hartill (Chairman) Chief Electrical Engineer NCB

S Luxmore HM Principal Electrical Inspector HMI M & Q(Deputy Chairman)

M Blythe Area Electrical Engineering, North Derbys NCB

G Cooper Area Electrical Engineering, South Notts NCB

H M Harrison Mechanical/Electrical Inspector NUM

T A Hughes Deputy Chief Electrical Engineer NCB


N Hindley H Q Winding Engineer (Electrical) NCB

H Routledge HM Deputy Principal Electrical Inspector HMI M & Q

A Rushton Representative BACM

W Walker Section Engineer GEC


* See List of Abbreviations at the end of this Appendix † Now Director of British Approvals Service for electrical equipment in flammable atmospheres.





Working Group 2A

T A Hughes Deputy Chief Electrical Engineer NCB(Chairman)

B Hill HM Deputy Principal Electrical Inspector† HMI M & Q

A G Gent Principal Engineer GEC

G Gray Area Electrical Engineer, South Yorks NCB

N Hindley Winding Engineer (Electrical) NCB

K Overton General Manager Blacks

A Thurtle Electronics Engineer Blacks

C B Flint (Secretary) Engineering Secretariat NCB

Working Group 2B

M Blythe (Chairman) Area Electrical Engineer North Derbys NCB

N Hindley HQ Winding Engineer (Electrical) NCB



W Walker Section Engineer GEC


Working Group 2C

G Cooper (Chairman) Area Electrical Engineer, South Notts NCB

T A Hughes Deputy Chief Electrical Engineer NCB

M Blythe Area Electrical Engineer, North Derbys NCB

R Dobson HM Senior Electrical Inspector HMI M & Q

A G Gent Principal Engineer GEC



* See List of Abbreviations at the end of this Appendix † Now Director of British Approvals Service for electrical equipment in flammable atmospheres





Working Group 2D

H Routledge HM Deputy Principal Electrical Inspector HMI M & Q(Chairman)

M Blythe Area Electrical Engineer, North Derbys NCB

G A Gregory Mining Manager Westinghouse

W Grew Operations Engineer, North Derbys NCB

J Hawksworth Sales Manager-Mining Plessey

P Holmes Managing Director STS

V Hosking Senior Engineer GEC

S J Robson Area Electrical Engineer, North Yorks NCB

G Sewell (Secretary) Engineering Secretariat NCB

W J Smith (Secretary) Electrical Project Engineer NCB

Sub-committee 3-(Maintenance)

A J Williams (Chairman) Chief Maintenance & Energy Engineer NCB

B Hill HM Deputy Principal Electrical Inspector† HMI M & Q(Deputy Chairman)

G E Hancock Head of Mechanical Maintenance Section NCB


J Hopkinson HM Senior Inspector of Mechanical HMI M & Q Engineering

T McGee Mining Engineer NUM

K Mitchell Area Mechanical Engineer, North Yorks. NCB

A Rushton Representative BACM

W J Searle HM Deputy Principal Inspector of Civil HMI M & Q Engineering


A Tait Deputy Chief Civil Engineer NCB


* See List of Abbreviations at the end of this Appendix † Now Director of British Approvals Service for electrical equipment in flammable atmospheres





Working Group 3C

D H Jackson Maintenance Engineer/Plant Pool Manager NCB(Chairman)

J Hodgkinson Maintenance Clerical Supervisor N. Derbys NCB

I H Morris HQ Ventilation Engineer NCB

J M Shaw HM Inspector of Mechanical Engineering HMI M & Q


R S Webb Area Safety Engineering, North Derbys NCB

H Whitehead Organisation & Methods Branch, Headquarters NCB

Working Group 3E

G E Hancock Head of Mechanical Maintenance Section NCB(Chairman)

J Evison Area Civil Engineer, South Yorks NCB

E R Giles HM Civil Engineering Inspector HMI M & Q

K Mitchell Area Mechanical Engineer, North Yorks NCB

H Sykes Deputy Area Mechanical Engineer, NCB North Yorks

A Tait Deputy Chief Civil Engineer NCB

H Wildsmith Maintenance Engineer (Mechanical) NCB

G Lunn (Secretary) Mining Secretariat NCB

Working Group 3F

R A Smith (Chairman) Deputy Chief Maintenance Engineer NCB


W Laing HM Electrical Inspector, South Mids, District HMI M & Q

L Parsons Testing Engineer, North Notts. Area NCB

K Salt Area Maintenance Engineer, Western Area NCB

J M Shaw HM Inspector of Mechanical Engineering HMI M & Q






W Smith Maintenance Engineer (Electrical), NCB South Yorks

G Thompson Maintenance Engineer (Electrical) NCB

H Wildsmith Maintenance Engineer (Mechanical) NCB

L Woods Deputy Area Mechanical Engineer, NCB Doncaster

A W Eadie (Secretary) Engineering Secretariat NCB

Sub-Committee 4-(Metallurgy and materials)

L C James Head of Technical Services MRDE(Chairman)

H D Munson Senior Principal Scientific Officer SMRE(Deputy Chairman)

A Bulmer Mining Engineer NUM


C E Nicholson Principal Scientific Officer SMRE

W G Stephenson HM Senior Inspector of Mechanical HMI M & Q Engineering

D A Sutcliffe Head of Metallurgy and Materials Branch MRDE

V M Thomas Deputy Director (Electrical Engineering) MRDE

T L Wall Principal Scientific Officer SMRE



Working Group 4A

D A Sutcliffe Head of Metallurgy and Materials Branch MRDE(Chairman)

C E Nicholson Principal Scientific Officer SMRE

J A Cottier Head of Regional Metallurgical Services MRDE

E D Yardley Materials and Metallurgy Branch MRDE

C H H Corden Senior Scientific Officer SMRE





Member Official designation Organisation* Working Group 4B

L C James Head of Technical Services MRDE(Chairman)

G A C Games Senior Scientific Officer SMRE

J W Hunter Testing Engineer MRDE

G W Sadler Head of Mechanical Testing Group MRDE

F E Taylor Head of Design Group B MRDE

T L Wall Principal Scientific Officer SMRE

D A Shorthose Senior Design Engineer MRDE

Working Group 4C(E)

V M Thomas Deputy Director (Electrical Engineering) MRDE(Chairman)

J E Burton Head of Monitoring and Communications MRDE Branch


GA C Games Senior Scientific Officer SMRE

A G Harley Deputy Chief Mechanical Engineer NCB

S J Robson Area Electrical Engineer, North Yorks NCB

A Birch Shafts and Winding Section NCB

Drafting panel


N Hindley Electrical Engineer, Headquarters NCB

HM Hughes Head of Production Design and Hydraulic MRDE Services Branch

W G Stephenson HM Senior Inspector of Mechanical HMI M & Q Engineering

P Wood Head of Shafts and Winding Section NCB




Published by the Health and Safety Executive 08/15 of 177

List of abbreviations

Abbreviations Organisation

AMEME Association of Mining Electrical and Mechanical Engineers

BACM British Association of Colliery Management

Blacks Blacks Equipment Ltd

GEC GEC Electrical Projects Ltd

HMI M & Q HM Inspectorate of Mines and Quarries, Health and Safety Executive

NCB National Coal Board

MRDE Mining Research and Development Establishment, National Coal Board

NUM National Union of Mineworkers

Plessey Plessey Communications Systems Ltd

Qualter, Hall Qualter, Hall & Co Ltd

SMRE Safety in Mines Research Establishment, Health and Safety Executive

STS Shaw, Trew & Smith Ltd

Westinghouse Westinghouse Brake and Signal Company Ltd

Acknowledgements The National Committee thank all persons and organisations who have contributed to this report. Many, at home and abroad, have given freely of their time, and organisations have generously afforded facilities, without which this report could not have been produced. Organisations include the National Coal Board, manufacturers, unions and associations.

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