updates on ex repair requirements & root cause failure

Ex WorkshopPower up your skills

1 Private & Confidential to EASA members only& participants at the EASA E&W Spring 21 Convention

Updates on Ex Repair Requirements & Root Cause Failure Analysis for Ex Equipment – Monday the 8th of March at 2.30pm CET

Bjorn Mjatveit, Martin Killeen, John Allen

Private & Confidential to EASA members only& participants at the EASA E&W Spring 21 Convention



Important EASA Training Program

EASA PEER TO PEER CONVENTION – STRONGER TOGETHER 2

• 23 Mar - Ex Awareness (online)

• 7-9 Apr – Ex Full Training (online) (Additional session)

• 15-16 Apr - HV winding practices training (online)

• 20 Apr - Ex Awareness (online)

• 22-23 Apr - Ex Refresher (online)

• 6-7 May - Principle of medium and large AC motors (IEC) (online)

• 19-21 May - Ex Full Training (online)

• 1-2 June – Root Cause Failure Analysis Training (Online)

Martin Killeen

Bjørn Mjåtveit

John Allen

Online & very Interactive !

https://easa9.org/training

And don’t forget All free webinars from EASA International: easa.com/training




Presentation of Bjorn Mjatveit



Repetition



5

Repetition: Why Ex equipment



Repetition: Updates and changes



Repetition: Annex C



Job report to user IEC 60079-19:2019 4.3.2.4.2



IECEx 314-5:2021 © IEC 20218.4 Records

The Ex Service Facility shall retain all repair, overhaul and reclamation records for a minimum of 10 years from the date the repaired product was released.



8.4 Records

A tick to just indicate pass is not accepted

IECEx 314-5:2021 © IEC 2021

✔



The measurement equipment used for the measurements of the Ex d flame paths shall also be mentioned in the report with respect to the

traceability of calibration

IECEx 314-5:2021 © IEC 2021



IEC 60079-19:2019 4.3.2.4.2

At the completion of the work, a job report shall be submitted to the user



IEC 60079-19:2019 4.3.2.4.2

a) details of fault(s) detected;

d) results of all checks and tests (in sufficient detail to be useful, if required, by the next repairer);

e) a comparison of the results against the criteria that have been used to determine compliance;



For repairs undertaken without the Ex Equipment Certificate and schedule drawings as referenced in 4.3.2.4.1, the following shall be included in the repair report:

1. Statement according to standard2. Statement of insufficient evidence..3. X-conditions has been identified and considered

IEC 60079-19:2019 4.3.2.4.2



IECEx OD 315-5 © IEC:2013(E) Annex A



Responsible person



Presentation of Martin Killeen



IEC 60034-23 and EASA Repair best Practice

Power up your skills

Martin Killeen [email protected]

mailto:[email protected]



EN IEC 60079-19, Edition 4 (2019)Explosive atmospheres : Equipment repair, overhauland reclamation.

This presentation is briefly summarising relationship between new Ex repair standard and its relationship with the new general electrical machine standard.

EN IEC 60079-19:2019 supersedes EN 60079-19:2011+A1:2015, which is withdrawn

This standard is part of IEC 60079 series and supplementary to other relevant IEC standards, for example the IEC 60034 series, in particular IEC 60034-23, 2019 - Rotating electrical machines : Repair, overhaul and reclamation

So the requirements in 60079-19 are now in addition to the requirements of IEC 60034-23 for Ex Equipment installed within a hazardous area.




Oil production vs consumption




Overall fossil fuel consumption increase



Induction Motors – EASA Repair Best Practice

Electric motors use about 50% of electricity generated

Estimated over 10 million motors in UK industry with total capacity 70 GW with 80% AC Induction Motors

Motor efficiencies range between 65% and 97%

The cost of electricity used by the average motor is in excess of 100 times the purchase price of the motor

A 1% decrease in efficiency of all motors in the EC would result in a £300M increase in electricity consumed



Scope Of IEC 60034-23

Covers the procedures for the satisfactory repair and overhaul of electrical machines .

Does not supersede specialist types like Ex, nuclear, aviation, hydrogen cooled, traction submersible etc..

Note IEC 60034-23 is now a requirement of IEC60079-19 , 2019

Used to prove the quality and performance of a repairer .

Aim is to maintain or improve efficiency and upgrade if required and allowed.

24



The repair of electrical machines complies with the circular economy.

Repair of energy efficient machines ensures use of the worlds dwindling resources.

The focus is to standardise on high efficiency so any repair needs to consider replace or repair as part of the efficient analysis .

25IEC 60034-23



Repairers Recognition

Repairer to have adequate facilities and equipment.

Suitably trained staff that are competent.

Suitable quality control system.

Use a repair label .

26IEC 60034-23



Efficiency

Ensure there is no degradation of performance.

Maintain efficiency values.

Standard states that a well equipped repair workshop with good quality control and competent staff can achieve this criteria.

Repairing an energy efficient machine is an environmentally friendly option .

The majority of wasted energy is not from electrical machines in the system but other items e.g. gearboxes, pipes, pumps, ducting, fans.

27

IEC 600034-23



• Friction & Windage Losses

• Iron Losses

• Stator I2R Heating Losses

• Rotor I2R Heating Losses

• Hard to Define Stray Losses

Induction Motors Losses What Are They





Extracts from the EASA Good Practice GuideLosses 2 pole

average4 pole

averageDesign factors

Affecting losses

Core losses(Wc)

19% 21% Electrical steel, air gap, saturation, supply frequency, condition of inter laminar insulation

Friction and windage losses (Wfw)

25% 10% Fan efficiency, lubrication, bearings, seals.

Stator I2R losses (Ws)

26% 34% Conductor area, mean length of turn, heat dissipation

Rotor I2R losses (Wr)

19% 21% Bar and end ring area and material

Stray load losses (Wl)

11% 14% Manufacturing processes, slot design, air gap, condition of air gap surfaces and end laminations



Factors Increasing Stator Copper Losses

Reduced conductor section

Increased mean turn length

Reduced airgap flux (incorrect stator winding)

Increased stray losses

Changing winding type

Note; Reducing copper size or type not permitted on Ex machines




Factors Increasing Iron Losses

Mechanical damage ( pulled tooth, rub, grinding & polishing)

Increased flux density (incorrect stator winding)

Factors that affect the quality of the laminations;Core and tooth rigidity and ability to hold shapeCore damage caused by the failureQuality of the interlaminar insulation (coreplate)

Damage caused by burnoutDamage caused by coil removalExcessive grinding and filing




IEC 60034-23 Core Issues

Core loss test or loop test to be performed if evidence of rubbing or damage. Flux test to 1.32 Tesla (50Hz) with a value exceeding 12 W/Kg . Note this is increase to 1.5 for Ex .

Hot spots greater than 10 degrees need to be repaired i.e. reinsulated, new laminations , new core pack

Air gaps to be within 10% of average value or 5% for 2 pole or large synchronous machines. Note for Exe machines there is also a need to check the min gap allowed .

Maximum core loss comparison before and after any burnout in the standard states 20% but EASA recommendations is 10%and 10 % specified for Exe .

33



Factors Increasing F & W Losses

Incorrect bearing mounting fit or clearance

Inappropriate bearing lubrication (Over & Under)

Incorrect seal fitting (type, seating & lubrication)

Incorrect fan (diameter, blades No. & area)




Factors Increasing Rotor Losses

Reduced airgap flux (incorrect stator winding)

Changed bar & endring materials & dimensions

Increased airgap

Incorrect replacement rotor





Stray loss

Damage to air gap surfaces

Uneven air gap (i.e., rotor eccentric with respect to stator bore)

Change in air gap

Damage to end laminations

Note changing air gap due to say skimming could be a problem for Exd machines dues to pressure piling and generally as it will increase surface temperatures



IEC 60034-23

Winding Removal

Removal of windings are to be by using a burn out oven to a maximum of 370 degrees C. If ec5 or ec6 steel (laminations with high quality interlaminar inorganic coatings )can go to 400 but the recommendation is to stop at 370.

Temperature profile and maximum temperature of the oven to be recorded and the machine to be mounted horizontally during the process .

Cut off coil extension using a cut-off machine

Remove the winding without damage to the core

37



Core loss testing

Conduct all tests using the same tester/method

Tests are well within the operating range of the core tester

Carry out tests before burnout and prior to winding (after cleaning)

Remember the figures are comparative not actual losses

If the losses increase by more than 10% ● check dimensions/calculations/settings/readings and repeat ● If the readings are confirmed consider repair/replace core laminations.




IEC 60034-23 General Winding Guidance

39

End winding projection and MLT to match original winding .

Match original insulation grade or better unless its Exe and then you need to use the same generic varnish type and impregnation process .

Upgrade of insulation grade might be needed if converter fed but for Ex types this is not allowed .

Varnish/resin impregnation to meet manufacturer's recommended curing temperature but take care for Exe .



Rewinding the motor (copy winding)

Check the old winding is manufacturers original

Use same winding type

Keep coil extensions as short as practical

Same overhang (same or shorter MLT)

Use same coil pitch (or pitches)

Use same turns/coil

Use same copper cross-sectional area or up to 3% more

Same or lower winding resistance (temperature corrected)




Motor rewind processes Include –Recording the winding detailsWinding configuration/typeImpregnation systemNumber of slots/poles/phasesNumber size and marking of leadsTurns/coilCoil pitchGroup connectionsPhase connectionsCoil overhang (connection and non-connection end)Number and size of wires in each coil (Note: increase CSA by -0% to +3%)




IEC 60034-23 Suitable varnish / resin application systems

42

Low voltage :• Dip and bake• Trickle• VPIHigh voltage:• VPI or VP• Resin rich tapes or foils Note for some specialist designs the impregnation method has to be the same as the original manufacturer's design.



IEC 60034-23 Housings End-shields , Fans

43

Maintain orientation of end shields.Rebuilt sleeve bearing housings to match original manufacturers dimensions.Rebuilt roller bearing housings to match the original design and meet concentricity. This will affect not only running temperatures but also ‘k’ value, air gap or flamepath dimensions

Any reclamation can use welding , sleeving or metal spraying. Refer to the restrictions stated in 60079-19 .

Replacement fans and fan cowls should be dimensionally and structurally equivalent to original. Remember fans have a cubic property so any change of design will affect windage losses and air flow and hence running surface temperatures. Also for Ex be carefull on material as this could be an ignition source if changed. There are also stated clearances to cowlings to consider .

Fans to be fitted the same way as the original method.



IEC 60034-23 Shafts

44

Before any remedial work is performed on a shaft the damaged area should be NDT’d e.g. dye penetrant , magnetic particle .

Cracks need to be removed if present.

Shafts can be repaired by sleeving, spiral welding, machining. If metal spraying a bond test of 40 MPa is recommended.

Note for Ex motors bond testing is a requirement.

Metal spraying not recommended for peripheral speeds above 90m/s .



IEC 60034-23 Shafts cont’d

45

Bearing seats can be reclaimed by metal spraying or welding .

The rebuilt size to meet manufacturer's or bearing manufacturers tolerances .

Peening shafts to improve fit not recommended .

Replaced shafts should have the same magnetic and mechanical properties as the original .

Recommended rotary/spiral welding techniques are MIG, TIG, sub arc or hot wire.



IEC 60034-23 Bearings

46

Rolling element bearings to be replaced with equivalents.

Greased bearings to be filled in accordance with recommendations.

Over greased bearings result in loss of efficiency .

Bearing fit onto shafts and in housings to be to IEC 60072-1 tolerances or manufacturer's recommendations.

Sleeve bearings should be bedded in following manufacturers recommendations .

Insulated bearings should be tested and results recorded.



IEC 60034-23Final Test Guidance

47

Insulation resistance measurement to be carried out using a megohmmeter normalised according to IEC 60034-27-4

Winding resistance of each winding to be normalised to a reference temperature . Guidance is phases within 1% formed coils , 3% wound coils.

No load and locked rotor tests in accordance with IEC 60034-1



IEC 60034-23Final Test Guidance

48

Cooling systems to be checked in accordance with IEC 60034-6( cooling methods )Sound level checks to be within IEC 60034-9 .

Vibration levels taken during no load test to be in accordance with IEC 60034-14 .

Rotor to be dynamically balanced in accordance with IEC 60034-14 (note there are two options for balancing a or b . a is for machines with special vibration requirements so consult with the user)



Reference Appendices within the rewind study good practice guide

Appendix 1. Chord factor and distribution factor

Appendix 2. Analysis of winding configurations

Appendix 3. Changing to lap winding examples

Appendix 4. Electrical Steels

Appendix 5. Repair-Replace considerations




Extracts from the EASA Technical ManualIn Section 24 Reference Material

Annex B Guidelines for maintaining motor efficiency during rebuilding (2-98 to 2-118)

Annex C The cause and analysis of stator and rotor failures in AC machines (2-119 to 2-137)

Annex D Stator core testing (7-17 to 7-23)

Annex E Electric motor diagnostic chart (10-30 to 10-31)




Presentation of John Allen

Ex WorkshopRCA for Ex Equipment 8th March 2021



RCA for Ex Equipment • EASA’s Root Cause Analysis methodology as

detailed in EASA’s RCA training materials, can be used for Ex Machines when considering the industrial aspects of rotating Ex electric machines in relation to IEC 60034 series of standards

• This methodology can also be used to conduct a root cause analysis relating to the special features which have been built into the design and construction of the machine to comply with the relevant Type of Protection standards



RCA for Ex Equipment EASA’s five cause analysis categories which are used during a root cause analysis are: -

• Failure mode• Failure pattern• Appearance• Application• Maintenance history



RCA for Ex Equipment As an example, when conducting a RCA of a flameproof Ex ”d” rotating electric machine each of the five categories should be reviewed, even though they may have been considered in the RCA as industrial equipment

Failure Modes: -• Flame path failure• Enclosure failure• Cable entry failure• Accessory failure



RCA for Ex Equipment For each of the failure modes should be evaluated to determine the failure patterns

Flame Path Failure Pattern: -• Corrosion• Bearing failure wear• Fitting damage



RCA for Ex Equipment For each of the failure patterns should be evaluated to determine the failure appearance

Flame path failure appearance: -

Corrosion Bearing Wear Fitting Damage




Enclosure Failure Pattern: -• Enclosure component defect or fracture• Enclosure threaded hole defect• Threaded fastener missing or not as specified• Threaded fastener clearance hole damage




Cable Entry Failure Pattern: -• Thread damage, corrosion or fitting damage• Insufficient threads to enable 5 full thread fit• Wall thickness insufficient for 5 full thread fit• Flame path gap excessive for plug entry




Accessory Failure Pattern: -• Temperature sensor failure• Vibration sensor failure



RCA for Ex Equipment EASA’s remaining categories for cause analysis which are used during a root cause analysis are: -

• Application• Maintenance history

These cause analysis will have been covered in the industrial RCA, however they need to be considered again on what impact they can have on the Type of Protection features particularly for effects on ingress protection



RCA for Ex Equipment The logic process detailed in EASA’s RCA can be applied to the specific safety features which have been used in the design and construction of Ex Equipment to ensure it is safe to use in a hazardous area

Different analysis’s will be required for each Type of Protection in addition to EASA’s RCA for rotating electric machines or other type of equipment



RCA for Ex Equipment I hope that this brief introduction provided sufficient information to assist you in conducting root cause analysis of Ex Equipment

If you require further support please do contact the EASA technical support team



Thank you!

John [email protected]

+44 7963 558069



Thank you!

Martin KilleenEmail

mobile

John AllenEmail

mobile

Bjørn MjåtveitEmail

mobile

www.easa9.orgLinkedIn EASA9 [email protected]

http://www.easa9.org/

mailto:[email protected]



Upcoming EASA Training sessions• 23 Feb - Ex Awareness (online)

• 24-26 Feb - Ex Full Training (online)

• 18-19 Mar - Fundamentals of DC Operation and Repair Tips (online)

• 23 Mar - Ex Awareness (online)

• 8-9 Apr - HV winding practices training (online)

• 20 Apr - Ex Awareness (online)

• 22-23 Apr - Ex Refresher (online)

• 29-30 Apr - Principle of medium and large AC motors (IEC) (online)

• 18 May - Ex Awareness (online)

• 19-21 May - Ex Full Training (online)

Full Training calendar at https://easa9.org/training


updates on ex repair requirements & root cause failure

Documents