buderus manuel ductile

Trenchless Installation

of Ductile Cast Iron Pipes

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Buderus Giesserei Wetzlar GmbHCast Iron Pipe Technology

P.O. Box 1240 D-35573 WetzlarPhone: +49 (0) 64 41 49 - 22 60

Fax: +49 (0) 64 41 49 - 16 13E-Mail: [email protected]

www.gussrohre.com

Buderus Manual

© BGW/RV • 035 • 06/08 • e 500 • DN

The future i

s ductile

„The conditions may be complicated,

but our ductile cast iron pipes, with their secure joints,

can be laid without any problems.“

Stephan Hobohm of the Applications Engineering Division of

Buderus Giesserei Wetzlar GmbH

www.gussrohre.com

Ductile cast iron pipe systems for drinking water supply and waste water disposal

Buderus Manual

Buderus Manual

on Trenchless Installation


Trenchless Installation of Ductile Cast Iron Pipes

�

Introduction

1. Introduction

When the infrastructure of our present-day towns and cities was being created and developed, the typical feature of the construction sites was large numbers of men to do the work. Trenches for laying pipes were excavated by hand, the pipes were lowered into the trenches without any mechanical lifting gear and vast amounts of sand and backfill material were shovelled in by hand. The most widely used material for the pipes was cast iron and the joints between them were sealed with hanks of hemp and poured lead.

Today, after more than 100 to 120 years, the networks of pipes that were laid at the time need to be rehabilitated and replaced. In those town and city streets where once upon a time there was plenty of space for pedestrians to stroll and elegant carriages to drive, there are now several lanes of dense motor traffic and kerbs that are blocked by parked cars, which means that delivery vehicles often double-park and cause further disruptions to the traffic. If the rehabilitation or replacement work on the existing network of pipes had to be done in conventional open-cut trenches in this case, the general interference with traffic would become almost total and it would be the community that had to suffer the additional costs of delays, exhaust and noise emissions and loss of retail income caused by the obstruction to public travel.It was therefore only logical for the first steps in the development of trenchless pipe installation techniques to be taken, as long as 30 years ago, in the densely populated areas of industrial towns, initially for the renovation or relaying of sewer pipes, which are generally situated on the lowest tier of the layers of pipes below the surface. Developers then transferred their attention more and more to the renovation and rehabilitation of drinking water and gas pipelines. A sector of industry devoted to trenchless installation grew up, with its own special machinery, installation techniques, technical rules and standards and of course, not least, its own pipes, which had to be suitable for these trenchless installation techniques.

Over the past ten years, Buderus Giesserei Wetzlar GmbH, with its ductile cast iron pipe, has made a crucial and impressive contribution to these developments and it is the story of this contribution that the present manual wishes to tell. The intention is also to describe the present state of the art, or in other words what installation techniques the ductile cast iron pipe can be used for, what are the performance features that it has and who are some of the satisfied customers who have put its ability to perform to the test.

Wetzlar, June 2008

�

Imprint

Published byBuderus Giesserei Wetzlar GmbHSophienstraße �2 - ��D-3��7� WetzlarTel.: +�9(0) �� 1- �9 22 �0Fax: +�9(0) �� 1- �9 1� 13e-mail: [email protected]

Authors: Dipl.-Ing. Steffen Ertelt, Dipl.-Ing. Stephan Hobohm, Dipl.-Ing. Lutz Rau, Wolfgang Rink of Buderus Giesserei Wetzlar GmbHDr. Jürgen Rammelsberg

Photo credits: Buderus Giesserei Wetzlar GmbHBerliner WasserbetriebeKarl Weiss GmbH & Co. KG, BerlinFachgemeinschaft Guss-RohrsystemeTracto Technik GmbH & Co. KG, LennestadtFrank Föckersperger GmbH, Aurachtal

© Buderus Giesserei Wetzlar GmbHAll rights reserved

All illustrations and details of weights and measures are subject to change. As part of ongoing technical development, we reserve the right to make product alterations and improvements without prior notice.

7

BuderusManual

TrenchlessInstallationofDuctileCastIronPipes

Listofcontents:

1. Introduction ................................................................................ �

2. Properties of ductile cast iron pipes ........................................... 8

3. Trenchless replacement of gas and water pipelines .................... 32 3.1 Push-pull technique ................................................................... 3� 3.2 Auxiliary pipe technique ............................................................ 39

�. Burst lining technique ................................................................ ��

�. Horizontal directional drilling technique ................................... ��

�. Ploughing technique .................................................................. �8

7. Pipe relining ............................................................................... 7� 7.1 Pulling-in technique ................................................................... 77 7.2 Pushing-in technique ................................................................. 79

8. Pulling-in after steered pilot drilling ........................................... 8�

9. A consideration of the economics of trenchless techniques ...... 92

10. Technical data sheets ................................................................. 98

11. Installation instructions .............................................................. 102

List of contents

8

2. Propertiesofductilecastironpipes

2.1Thematerial

In the 17th century there were isolated instances where pipes made of cast iron were used for laying water-pipes on es-tates belonging to the aristocracy, such for example as at chateaus and country houses, in parks, and so on (Fig. 2.1).In the 19th century, with the coming of the Industrial Revolution, towns and cities and industry began to develop. The growth in the population accelerated and there was thus a growing need for an infrastructure to be created based on pipes for drinking water, gas and sewage.

Cast iron in the form of pig iron is produced by using coke to reduce iron ore in a blast furnace, a process known as smelting. A particularly important type of smelter used in foundry work is the cupola furnace in which scrap iron and steel and pig iron are smelted with coke. Another typical process for producing cast iron is smelting in an electric induction furnace.

In these smelting processes, some of the carbon goes into solution in the liquid iron, as a result of which the melting point of the pure iron goes down from about 1��0°C to a figure of 11�0°C. This is the most important prerequisite for the industrial and economical processing of cast iron, because it allows the consumption of energy, re-fractory materials and mould materials to be reduced. The second advantage of the carbon dissolved in the iron comes into play when the molten cast iron solidifies: the contraction in the volume of the iron as it changes from the liquid to the solid state counteracts any increase in the volume of the dissolved carbon which crystallises out. Consequently, articles made of cast iron generally have a dense microstructure free of cavities. The disadvantage of the elemental graphite in the cast iron is that it reduces the strength and ductility of the pure iron. In the course of solidification, the dissolved carbon normally crystallises in the form of graphite lamellae.

Properties of ductile cast iron pipes

Fig 2.1, Fountains in the park at the Chateau de Versailles

9

At x 100 magnification, these graphite lamellae can clearly be seen in metallographic micro-sections (Fig. 2.2). Under the scanning electron microscope, the space-filling structure of the graphite lamellae is very clear (Fig. 2.3).

Fig. 2.2 Fig. 2.3

The lamellar graphite, which has no strength of its own, interrupts the matrix of metal in which it is em-bedded and thus causes the relatively low strength which cast iron has. At the same time, this internal structure also gives the material poor ductility: its fracture behaviour is brittle. The modelled repre-sentation shown in Fig. 2.� simulates the internal notch effect which is caused by the concentration of stress lines at the tips of the lamellae. This is the reason for the poor ductility of grey cast iron.

Some �0 years or so ago, the form in which the graphite crystallises was successfully altered by a metallurgical treatment of the melt with metals with a high affinity for oxygen (cerium, magnesium). In a melt of cast iron in which the graphite would origi-nally have solidified in lamellar form, it solidifies in a spheroidal form if a small amount (about 0.0�%) of the above metals is added.

Fig. 2.4

Fig. 2.5

The material

10

Compared with lamellar graphite, graphite in a spheroidal form reduces the internal stress concentrations in the base metal. The strength of cast iron containing spheroidal graphite is considerably higher than that of cast iron containing lamellar graphite and it also has the ability to deform plastically under external mechanical loads. The associated modelled representation is shown in Fig. 2.�. The stress lines are less tightly packed be-tween the spheroids of graphite than they were at the tips of the lamellae. This gives the material the ability to undergo elastic and plastic deformation before it actu-ally fails. Behaviour of this kind by a material is called ductile. This significant change in the properties of the mate-rial has meant that spheroidal graphite (i.e. ductile) cast iron has been able to replace steel in many areas of mechanical engineering.

Experts on the pipe networks used for supplying gas and water were very quick to appreciate the advantages that the ductile behaviour of the new material gave: if over-stressed mechanically, brittle pipes fail by what are called egg-shell fractures, where large openings, which allow vast amounts of water to escape and cause considerable consequential damage, appear all at once. When the failure of the material is ductile, a high proportion of the fracturing energy is converted into deforming energy. Highly deformed parts of the workpiece are always found close to the fracture. Crack propa-gation proceeds more slowly and only a small amount of water escapes through the comparatively small opening that it produces. Underscouring as a consequence of egg-shell fractures is now a thing of the past. In the mid-nineteen-sixties, ductile cast iron superseded grey cast iron as a material for pipes in the gas and water supply industry.

In 1973, Albrecht Kottman published details of the trials he had conducted to demon-strate the outstanding energy of deformation of ductile cast iron pipes. Fig. 2.7 shows the test rig he used: two-meter-long pipes of a nominal size of DN 100 and of differ-ent materials were set up on two supports as beams stressed in bending and were stressed by a force applied at mid-span. The stress-strain curves plotted in these trials are shown in Fig. 2.8. Whereas a DN 100 pipe of lamellar graphite cast iron fractured at a load of approxi-mately six tonnes with almost no deformation (= brittly), the pipe of ductile cast iron bowed by 17 centimetres under approximately the same force before it failed.

Fig. 2.6


11

103

kp c

m

Fig. 2.7

Fig. 2.8

The material

Kottmann defined the integral of the area below these curves as energy of deformation and compared this property of pipes made of different materials in the bar chart shown in Fig. 2.7. He was able to show in this way that the energy of deformation of pipes made of ductile cast iron was higher by more than a power of ten than that of, for example, pipes made of grey cast iron.

Seamless steelWelded steelAsbestos cement

PVC

Ductile cast iron

Grey cast iron

Test rig

Steel Ductile Grey Asbestos PVC cast cast cement iron iron

12

2.2Howthepipesareproduced

Casting techniques of the kind which had been developed in the Middle Ages, above all for casting works of art and bells and also for casting guns, were a prerequisite for the development of a technology for producing high-quality pipes. Initially pipes were cast in horizontal moulds where the moulds were also split horizontally. This meant that there was a limit to how long the pipes could be, given that at the casting temperature of some 1300°C and under their own weight, the cores used to form the hollow cen-tres of the pipes would bend, which also limited the uniformity of the wall thickness of the pipes. Pipes dating from this early period of manufacture can be recognised by the two lines of flash on opposite sides of their outer surface, which formed in sand moulds on the plane marking the division between the top and bottom halves of the moulds

(Fig. 2.9).With the increasing demand for cast iron pipes for supplying water and gas in the rapidly expanding towns and cities in the second half of the 19th century, the car-ousel casting process was introduced, in which the sand moulds were arranged upright in casting carousels in such a way that a semi-continuous procedure became possible. In this process, the moulds, in the form of undivided metal mould boxes matched to the shape of the pipe, were initially placed in position individually and later on in rotary racks, to allow work to go on in a continuous flow. The cores to produce the hollow centres in the pipes were rammed onto metal core spindles with the help of metal core bushes. There was an increase in the overall length of the pipes and the flash at the mould division

disappeared. This process was used by Buderus from the time when pipe production began in 1901 until 192�. Hundreds of thousands of kilometres of pipes dating from this period of production are still giving faithful service below the ground.A particularly important milestone in the course of further development was the inven-tion of the centrifugal casting process (Fig. 2.11). In 192�, this process was successfully introduced throughout Europe, including at Buderus. One of its principal features is


Fig. 2.9

Fig. 2.10

13

How the pipes are produced

Fig. 2.11

Fig. 2.12

a permanent metal mould (a chill mould) which is cooled from the outside by water and which does not need a thermally in-sulating covering. One chill mould can be used to cast as many as several thousand pipes, depending on their nominal size. The sudden quenching of the liquid cast iron against the water-cooled chill mould produces just a single solidification front, facing towards the wall of the chill mould, which makes the microstructure particu-larly fine-grained and dense. After heat treatment to transform the microstruc-ture (Fig. 2.12), it is possible to obtain ap-preciably higher strength in the grey cast iron pipes than can be obtained in pipes cast in sand moulds. The length of the pipes went up to five or six metres, and the wall thickness went down and became more uniform. Shortly after the centrifugal casting process made its breakthrough, the new joint-making technique was invented (see section 2.3), and after that the lead-sealed socket could only be a thing of the past.

1�

In today‘s typical pipe foundry, the cast iron for producing the pipes is smelted in a cu-pola furnace, is adjusted to a preset composition by tailored metallurgical procedures and is raised to the requisite casting temperature. This is followed by the treatment with magnesium to produce ductile cast iron and the melt, having been treated in this way, is then at once cast into pipes.

The outcome of the developments that took place over the �0 years between 1920 and 1970 was that the tensile strength of pipes could be raised and their weight and wall thickness halved. As development of the production technology has continued, and above all with modern-day systems for controlling the casting machines, it has been possible for a considerable further reduction to be made in the wall thickness of the pipes. Account has been taken of this in the product standards EN �� [2.1] and EN �98 [2.2], where a shift can be seen from classification by wall thickness to clas-sification by pressure class.


1�

In the period which saw the growth of centralised systems of water supply (18�0-1930), the cast iron pipes were fit-ted with a socket that had to be packed; it was sealed with tarred hanks of hemp and poured lead (Fig. 2.13). When they are being made, joints made with packed sockets call for great skill and reliability on the part of the fitters doing the job. Be-cause the sealing material is very inelastic, the joint must not be subject to any move-ments. Bedding which will not be disturbed and support for the pipe which does not allow any movement are essential for long-term freedom from leaks.Rolling ring seals made of rubber were initially introduced for gas pipes in 18�0 and from 18�3 on they came into use for water pipes. As from 1910 there were some initial trial pipes in Stuttgart which used a precursor of the screw-gland socket joint but the advantages of this joint were not appreciated for the time being. It only made its real breakthrough in the early 1930‘s (Fig. 2.1�) and in doing so it represented a milestone in pipe-laying in that since then the elasticity of seals of vulcanised rubber has allowed joints to move to a certain degree.

2.3Developmentinthejoint-makingtechniques

When cast iron pipes first began to be used, one of the primary concerns was seal-ing the individual butt joints between the pipes. In 172�, Jacob Leupold had already described in his book [2.3] a mixture of various powders and substances containing organic constituents to produce a sort of putty that was halfway elastic.

Development in the joint-making techniques

Fig. 2.13

Fig. 2.14

1�

The characteristic feature of the screw-gland socket joint for the range of nominal sizes from DN �0 to DN �00, and of the bolted-gland socket joint (Fig. 2.1�) which is more suitable for larger nominal sizes, is that a gasket of elastic rubber is com-pressed by mechanical means. This seals the joint against gaseous and liquid media. In the early 19�0‘s, Buderus introduced the TYTON® socket joint. With this de-sign of joint, all that is needed apart from the two pipes to be joined is a profiled gasket. When the inserting end is slid into the socket containing the gasket, the gas-ket is compressed and thus automatically makes the seal. Fig. 2.1� shows this joint, for which there is a standard in the form of DIN 28�03 [2.�]. Extensive checks have shown that this joint will remain sealed for decades even when subject to dynamic angular deflection movements.

Their design means that the socket joints which have been described are not locked against longitudinal forces. At changes of direction, stop-ends, changes of cross-sec-tion and branch pipes, the internal pressure of the water generates longitudinal forces which have to be dissipated into the ground in some suitable way. Traditionally, this has been done by using concrete counter-bearings. These are sized in such a way that the size of the rear face prevents the permitted pressure per unit area on the in-situ soil

Fig. 2.15

Fig. 2.16

from being exceeded. The rules for the sizing of counter-bearings made of concrete are given in DVGW Arbeitsblatt GW 310 [2.�]. The smaller and smaller amounts of space that are available in the ground below our towns and cities has made it necessary for this technique to be gradually abandoned and to be replaced by joints which are trac-tion-resistant.

Traction-resistant joints are locked against longitudinal forces yet are able to hinge at the same time. The principle on which they operate is that the resistance of the earth is brought into play by slight movements of the fittings and the pipes connected to them. The document giving the technical rules for the use of such longitudinal force-fit


17

joints is DVGW Arbeitsblatt GW 3�8 of June 2002 [2.�]. The current designs are shown in section in this document togeth-er with the associated performance data.A distinction is made between joints which are locked by friction and joints which are positively locked. With its BRS® friction-locking joint and its BLS® positive-locking joint, Buderus offers two innovative so-lutions in this case. In the BRS® friction-locking joint (Fig. 2.17), sharp, hardened stainless steel teeth bite into the surface of the inserting end and this produces the frictional connection. There are also friction-locking designs for bolted-gland socket joints.

In the BLS® positive-locking joint, a bead of weld metal is applied to the surface of the inserting end either in the factory or on site and appropriate force-transmit-ting members are supported against this bead and thus transmit the longitudinal force from one pipe to the next (Fig.2.18).

The development of these socket joints, which are locked against longitudinal forces but at the same time able to hinge, to their present-day standard of maturity was es-sential to the development of modern-day trenchless techniques for installing pressure pipelines. In almost all of the trenchless installation and renovation techniques which are described in the present manual, it is a hinged string of pipes locked against longi-tudinal forces which is pulled into the final route of the pipeline. Whereas in the series of standards which applied previously, namely DIN 28�00 et seq., it was just the pipes and fittings which were exactly described, in the European standards which now apply, namely DIN EN �� for water pipes and DIN EN �9� for sewage conduits and pipes, there is a new aspect which is considered, namely the functional requirements they have to meet. With their exact descriptive specifications, the earlier national stand-ards provided what was needed for technical delivery conditions. The additional aspect dealt with by the European standards, namely the functional requirements which the

Entwicklung der Verbindungstechnik

Fig. 2.17

Fig. 2.18

18

pipe system and its joints have to meet, specifies what the performance of the pipe system and its joints has to be. In the type tests which are laid down for this purpose, the components and their joints are tested for the following:

• Sealing of the components against internal water pressure• Sealing of joints against positive internal pressure when subject to loads at the crown

resp. angular deflection• Sealing of joints against negative internal pressure when subject to loads at the crown

resp. angular deflection• Sealing of joints against positive external pressure when subject to loads at the

crown.

The longitudinal force-fit joints also have to pass a dynamic test in which the internal pressure alternates between PMA and PMA-� for 2�,000 load cycles. The functional requirements described and the related type tests have been included in the techni-cal rules of the DVGW (the German Technical and Scientific Association on Gas and Water) which are given in Arbeitsblatt GW 3�8. In view of the importance that high-quality longitudinal force-fit restrained joints will have in the future for trenchless pipe installation, the supplementary requirement of an externally monitored type test was introduced when the above document was revised in 2002. As well as this, all designs have to be listed by the following characteristic performance parameters: • allowable component operating pressure (PFA)• allowable angular deflection.

With these particulars plus an indication of the externally monitored type test, there being sets of particulars which are representative of respective ones of four groups of nominal sizes, the planning engineer has the right tool for selecting the design giving safety against tractive forces that is best suited to a specific task.


19

2.3.1Longitudinalforce-fitjointsandtechnicalrulesfortrenchlessinstallation

In the period between 2002 and 200� the drawing up by the DVGW of a set of tech-nical rules for quality assurance for trenchless installation and renovation techniques also took place. The quality of pipelines which are installed by these techniques is affected not only by the effects due to the soil but also by the following parameters, which have to do with the pipes themselves:• permitted tractive forces• minimum radius of curves.These parameters have to be measured and documented, to ensure that the planned operating life will not be reduced by components that were damaged at the outset due to over-stressing. For the most important materials, they are listed in the sets of tables which can be found in the appendices to the documents mentioned, these materials being. • ductile cast iron• cross linked polyethylene (PE-X)• PE 100• St 37 steel.Allowance is made for the dependence of the permitted tractive stress on temperature and for the time for which it lasts in the case of the thermoplastic materials. In this way, the permitted pulling-in forces have to be decreased by a quarter for pulling-in times of more than 20 hours, and when pipes are at a wall temperature of �0°C the permitted force has to go down by 30% compared to a wall temperature of 20°C. Further reductions have to be envisaged when pipes follow curved paths. In contrast to these reductions due to routeing and temperature, for ductile cast iron pipes there are increases that can be made in the permitted forces when the pipes run in a straight line with no appreciable angular deflections. The temperature of the pipe wall is immaterial with ductile cast iron pipes. For the longitudinal force-fit BLS® joint, Table 2.1 gives the following parameters • permitted tractive force• angular deflection which is possible• minimum radius of curves.The figures for the permitted tractive force were taken from the results of externally monitored internal-pressure tests conducted as part of the standard type tests, as indicated in the headings of the columns in the table.

Longitudinal force-fit joints and technical rules for trenchless installation

20

To the experts at the Berlin water supply company Berliner Wasserbetriebe (BWB), who were pushing ahead with the trenchless replacement of the old systems of grey cast iron pipes, the above figures of GW 321 appeared to be too low. Hence, as a joint endeavour of the cast iron pipe industry, the Karl Weiss company and BWB, axial trac-tive tests were carried out on pipes of nominal sizes ranging from DN 100 to DN 200, with no internal pressure, until they began to fail [2.8].


Nominal size DN [mm]

Component operating pres-

sure [bar] 1)

Permitted trac-tive force Fperm

[kN] 2)

DVGW BGW

Possible angular

deflection of sockets3) [°]

Minimum radius of curves [m]

80* 110 70 11� � �9

100* 100 100 1�0 � �9

12� 100 1�0 22� � �9

1�0 7� 1�� 200 � �9

200 �3 230 3�0 � 8�

2�0 �� 308 37� � 8�

300 �0 380 380 � 8�

�00 30 ��8 ��0 3 11�

�00 30 8�0 8�0 3 11�

�00 32 1200 1�2� 2 172

700 2� 1�00 1��0 1.� 230

800 1� - 1��0 1.� 230

900 1� - 18�� 1.� 230

1000 10 - 1��0 1.� 230

1) Basis for calculation was wall thickness class K9. Higher pressures and tractive forces are possible in some cases but must be agreed with the pipe manufacturer.

2) When pipelines follow straight paths (max. deflection of 0.5° per pipe joint), the tractive forces can be raised by 50 kN. High-pressure locks are required for DN 80 - DN 250.

3) When of the nominal dimensions* Wall thickness class K10

Table 2.1: Permitted tractive forces, angular deflections which are possible, and radiuses of curves for ductile cast iron pipes with BLS® joints (source: DVGW Arbeitsblatt GW 321 [2.7] and Buderus Giesserei Wetzlar GmbH (BGW)

21


Nominal size DN [mm]

Component operating

pressure PFA [bar] 1)

Permitted trac-tive force Fperm

[kN] 2)

Capacity for an-gular deflection of sockets [°]

Minimum per-mitted elastic bending radius

Rmin [m]

80 �� 1002) 3 11�

100 �� 2�01),2) 3 11�

1�0 �0 3201),2) 3 11�

200 �0 �001),2) 3 11�

2�0 3� �002) 3 11�

300 30 �002) 3 11�

�00 2� ��8 3 11�

1) Determined by tractive tests (see report)2) The tractive forces given apply only to Berliner Wasserbetriebe and to DN 80 - DN 250 BLS®

joints with high-pressure locks.

The results obtained in these tests showed there to be a threefold safety margin in comparison with the figures given in Table 2.1. FEM calculations carried out by Prof. Bernhard Falter [2.9] showed very good agreement with the experimentally deter-mined figures for permitted tractive force. The very safe nature of the figures which were given for the permitted tractive forces on positive-locking joints in ductile cast iron pipes in the DVGW rules had two consequences:1. In its internal technical rules, BWB made a very large increase in the permitted trac-tive force from the figures given in the DVGW rules. This was because practical expe-rience of a wide variety of kinds had convinced it of the high performance of the joints (see Table 2.2).2. A footnote was added to the tables in the DVGW rules saying that, with pipelines following straight paths and with an angular deflection of less than 0.�° ( = a radius of curvature of �87 metres), the permitted tractive force could be increased by �0 kN (see Table 2.1)

Table 2.2: Permitted tractive force for positive-locking joints in cast iron pipes(source: internal standard WN 322 of Berliner Wasserbetriebe)

22

100150

200300

400

0

100

200

300

400

500

600

700

In the bar chart (Fig. 2.19), the figures from Table 2.1 for the maximum permitted trac-tive force on ductile cast iron pipes with BLS® joints are compared with those for other materials for water pipelines. Of all the current materials for water pipelines, Buderus Giesserei Wetzlar GmbH‘s ductile cast iron pipes with positive-locking BLS® joints


Fig. 2.19: Maximum permitted tractive forces of different materials. Source: DVGW

have the highest permitted tractive forces. This allows installation pits to be spaced further apart when ductile cast iron pipes are being used and thus makes the pipes more economical without the need for safety to be sacrificed in any way. Additional increases, both in the operating pressure and in the permitted tractive force, are pos-sible by increasing the class of wall thickness, but special agreements have to be made with our Applications Engineering Division for this purpose.

Material

Nominal Size

Tractive force [kN]

PE-Xa SDR 11 pipes

PE 100 SDR 11 pipes

St 37 steel

Ductile cast iron,

BLS® joints

23

2.3.2MakingtheBLS®joint

For the trenchless installation of ductile cast iron pipes, the technical rules of the DVGW agree with what is specified in Buderus Giesserei Wetzlar GmbH‘s installation instructions in laying down the use of positive-locking joints.

The circumstances under which friction-locking joints may fail are, above all, when there have been a number of angular deflection movements of the kind which may oc-cur on steered directionally drilled runs when there are a number of curves in opposite directions along the run. This is because there are tractive forces which alternately relieve the load on the teeth of the retaining segments when these movements occur. There is no fear of this happening on runs which follow a straight path. Nevertheless, to prevent any risk, the use of positive-locking joints has been laid down for trenchless installation techniques. There is an additional advantage in that the maximum permit-ted tractive forces can be transmitted in this way.

The Buderus positive-locking BLS® system makes it possible for the two connecting processes which may be referred to as • „making a seal“ and• „locking“to be separated and made into two separate steps which have to be performed one after the other and which can be checked.In the first step it is thus the TYTON® joint which is made, following the installation instructions (see section 10): the socket and the inserting end having been cleaned, the gasket is inserted in the retaining groove in the socket by its hard-rubber claw. The cir-cumference of the gasket is deliberately made larger than the circumference of the seal-ing surface with which it mates in the groove, and this means that the seal is subject to a pre-loading. Because of this, particularly with large nominal sizes, it may be helpful for a second fold to be made in the gasket on the opposite side. The two small folds can then the pressed flat without any trouble. The checking step which then follows ensures that the retaining claw on the gasket is pressed fully into the retaining groove around the en-tire circumference and is nowhere spaced away from the locating bead (Fig. 2.20). The faces of the gasket and inserting end which slide against one another are then given a thin coat of the lubricant which is supplied by Buderus with the joint and the inserting end is inserted in the socket square with it (i.e. with no angular deflection). Depending on the nominal size of the pipe, the axial force required to compress the bead on the gasket can be applied with a crowbar, a laying tool or the hydraulic digger.

Making the BLS® joint

2�

When joints are being made with a hydraulic digger, a suitable interlayer, e.g. a length of squared-off timber, must be placed between the pipe and the bucket of the digger. The pipe must be pressed in gently and sufficiently slowly for the gasket to have time to deform. Regardless of what equipment is selected to make the joint, pipes and fittings must be lined up so that they are concentric and square to one another.

Locking

The pipe remains square to the socket and is pressed into the latter until the welding bead is resting against the internal locating bead. This ensures that there is room for the locking members. Depending on how many there are, these are inserted though the openings in the end-face of the socket and are distributed around the circumference to the right and left. In the size range from DN 80 to DN �00 the locking members are locks (Fig. 2.21) whereas in the range from DN �00 to DN 1000 they are segments of a flat, planar form (Fig. 2.22). In the case of the locks, a distinction has to be made between the „left“ and right“ types, and these have to be inserted as directed in the installation instructions. With trenchless installation techniques and in high-pressure applications, an additional high-pressure lock is required. When the fitting of the lock-ing members has been completed, a rubber catch fitted in the opening that is still clear in the end-face of the socket stops the locking members from shifting.


Fig. 2.20

Wrong

Right

2�

With nominal sizes from DN �00 to DN 1000, the planar locking segments are inserted in the axial direction through the twin openings in the end-face of the socket and are then moved to be evenly spaced around the circumference. To simplify the locking process, the open-ings are preferably positioned to be at the crown of the pipe (Fig. 2.23). Once all the locking segments have been inserted in the gap in the socket, they are shifted as a whole around the circumference suffi-ciently far for none of the humps to be vis-ible through the openings in the socket.The segments are fixed by a clamping strap and locked by gently pulling the pipe out of the joint until the welding bead comes to rest against the segments. An extra-strong metal clamping strap has proved useful in directional drilling projects involving a number of changes of direction (Fig. 2.2�)A detailed description of how the vari-ous components are dealt with and used can be found in the operating instructions (section 11).

Catch

Fig. 2.21

Fig. 2.22

Left lockRight lock

High-pressure lock

Fig. 2.23

Fig 2.24

Making the BLS® joint

2�


Table 2.� shows the average assembly times required by a practised team of one or two pipe layers to make a BLS® joint. The differences are the result of the different possible ways in which the joint can be protected. In the majority of pipe replacement operations, the joints are made for one length of pipe at a time in a pipe-assembling pit dug for the purpose. After the step of making the joint, the pipe string is pulled forward by the length of one pipe. If the on-site logistics are organised in the optimum way, it is possible to achieve speeds of installation of �0 to �0 metres an hour for the lower range of nominal sizes. It is impossible to achieve speeds of this kind with welded joints between pipes, especially if one bears in mind that with pipes of ductile cast iron using BLS® joints the maximum permitted tractive force can be applied, in full, immediately the joint has been made and there is no need to wait for any cooling times.

Table 2.�: Average assembly times for the BLS® joint

Nominal size Number of fitters

Assembly time with no joint protection

[min]

Assembly time when a protec-

tive sleeve is used [min]

Assembly time when shrink-on sleeves are used

[min]

DN 80 1 � � 1�

DN 100 1 � � 1�

DN 12� 1 � � 1�

DN 1�0 1 � � 1�

DN 200 1 � 7 17

DN 2�0 1 7 8 19

DN 300 2 8 9 21

DN 3�0 2 9 10 23

DN �00 2 10 12 2�

DN �00 2 12 1� 28

DN �00 2 20 22 3�

DN 700 2 22 - 37

DN 800 2 2� - �0

DN 900 2 28 - �3

DN 1000 2 30 - ��

27

Inside and outside protection

2.4Insideandoutsideprotection

Hand in hand with the introduction of ductile cast iron, there was also a rapid devel-opment in systems for inside and outside protection. Nowadays, pipes, fittings and accessories of ductile cast iron are all supplied complete with linings and coatings of a wide variety of types as an integral part of the product. The nature of the protection is governed by the conditions of installation and operation.

2.4.1Outsideprotection

The grey cast iron pipes of the period from the end of the 19th century to the mid-20th century were endowed with their legendary long life by dipping them in liquid tar or asphalt, but the use of tar was discontinued at the end of the 1970‘s, roughly at the same time as ductile cast iron was introduced. As from the 1970‘s, dip-coating with tar was superseded by coating with bituminous paints. This was supplemented, or its field of application extended, by zinc coating (introduced later, as from the early 1970‘s) and by coatings of plastic-modified cement mortar (from 1978 on). More recently, the place of bituminous paints has also been taken by epoxy resin coatings.

Because of the enormous importance it has for the use of ductile cast iron pipes in trench-less installation techniques, the cement mortar coating will be looked at in detail at this point. The cement mortar coating was initially developed chiefly as an outside protection for ductile cast iron pipes when they were going to be installed in stony ground, where it would have been expensive to get hold of sand or non-stony soil to bed the pipes in. The characteristic features of a coating of this kind are its high mechanical strength and resistance to chemicals, high impact resistance and high strength of adhesion. These requirements were decided on in consultation with the users and have been combined with the requisite methods of testing in DIN 30�7�-2 [2.10]. To implement the European construction product directive, a European standard, DIN EN 1��2 [2.11] has been laid down for cement mortar coatings for ductile cast iron pipes.

In this connection, it will be recalled that the technical rules for conventional pipe-laying give detailed requirements that the nature of the pipeline zone has to meet in order to safeguard the pipeline components against damage and deformation. In the first place, the bedding layers have to be produced from non-stony soil in such a way that the pipes rest down evenly over their entire length. The wedge-shaped space between the pipes and the bedding layers has to be evenly packed with non-stony soil, and any changes in the position of the pipe have to be avoided when this is done.

28


The trench then has to be infilled layer by layer with non-stony soil at the sides, next to the pipe, and this has to be compacted as directed by the stress analyst, before fi-nally, after 30 centimetres of non-stony soil has been dumped in and compacted over the crown of the pipe, the requirements become rather less stringent (Fig. 2.2�).

DVGW Arbeitsblatt W �00-2 [2.12] provides an overview of the grain-sizes of filling and bedding materials for be used for various pipe materials. Under it, ductile cast iron pipes can be bedded in materials with a maximum grain size of 100 millimetres. The aim and intention of all the requirements is to ensure that the pipes will produce a pipeline of exactly circular cross-section in which there are no unacceptably high stresses in the walls of the pipes. This is the only way in which the long operating life that is desired can be achieved.

Let us now consider the bedding conditions for a pipe which is installed by a trenchless technique: it is true that the customer will have a general knowledge of the ground he has, but he will certainly not be able to rule out the possibility of stones or other sharp objects being present along the run, against which the pipe will rub while it is being pulled in. With the burst lining technique for example, the new pipe is pulled through

Fig. 2.25

Surface

Walls of trenchMain infill

Direct cover zone

Lateral infill

Upper bedding layer

Lower bedding layer

Height of cover

OD

Bedding

Pipeline zone

Depth of trench

29

Inside and outside protection

the collection of sharp-edged fragments that once formed the old grey cast iron pipe. With the directional drilling technique, some of the supporting fluid may soak away through gaps in the soil, thus producing interruptions in a bed that was formerly even. This may result in settlement of the cover, or in short: trenchless techniques are car-ried out „out of the public eye“ as it were, and there is thus no controlling eye which can check that the stringent requirements which apply to the conventional open-cut techniques are in fact satisfied.

It is clear that what has to be used in the „black box“ that the trenchless techniques represent is the most rugged pipe which has the coating able to withstand the high-est mechanical loads. The Buderus ductile cast iron pipe, which has, comparatively speaking, the highest energy of deformation of all the types of pipe for water pipelines (see section 2.1), has the best prerequi-sites for undamaged installation under the uncheckable conditions that exist with the trenchless techniques. At the same time the positive-locking BLS® joint, with its high permitted tractive forces, allows installation pits to be spaced at long inter-vals without any risk of the pipes failing when they are being pulled in.

2.4.2InsideprotectionAs mentioned in the preceding section, the use of tar and asphalt as both an outside and an inside protection for cast iron pipes was discontinued in the 19�0‘s. Whereas bituminous paints were then used for outside protection, an entirely new path was taken in the case of inside protection in the form of a lining of cement mortar. Depending on the application, what are available nowadays for the inside protection of ductile cast iron pipes are cement mortar linings based on blast furnace cement for drinking water applications or ones based on alumina cement for sewage applications. At Buderus Giesserei Wetzlar GmbH, coatings of these two variant types are ap-plied to the inside of the pipe by the ro-tary centrifugal process to DIN 2880. This process gives the cement mortar lin-ing a very high abrasion resistance. Even rates of flow of up to 20 m/s for the me-dium carried are no problem.

Ductile cast iron pipes with BLS® restrained joints and cement mortar coatings

Wat

er is life

30


2.5 Reference documents

[2.1] DIN EN �� Rohre, Formstücke, Zubehörteile aus duktilem Gusseisen und ihre Verbindungen für Wasserleitungen – Anforderungen und Prüfverfahren [Ductile iron pipes, fittings, accessories and their joints for water pipelines – Requirements and test methods]

[2.2] DIN EN �98 Rohre, Formstücke, Zubehörteile aus duktilem Gusseisen und ihre Verbindungen für die Abwasser-Entsorgung Anforderungen und Prüfverfahren [Ductile iron pipes, fittings, accessories and their joints for sewerage applications – Requirements and test methods]

[2.3] Leupold, J.: Theatrum machinarum hydrotechnarum der Wasserbaukunst; Leipzig 172�

[2.�] DIN 28�03: Rohre und Formstücke aus duktilem Gusseisen – Steckmuffen-Verbindungen – Zusammenstellung, Muffen und Dichtungen [Ductile iron pipes and fittings - Push-in joints; survey, sockets and gaskets]

[2.�] DVGW-Arbeitsblatt GW 310: Widerlager aus Beton; Bemessungsgrundlagen (Entwurf 2007) [Concrete abutments: principles of sizing (draft of 2007)]

[2.�] DVGW-Arbeitsblatt GW 3�8: Längskraftschlüssige Muffenverbindungen für Rohre, Formstücke und Armaturen aus duktilem Gusseisen oder Stahl [Longitudinal force-fit restrained joints for ductile cast iron and steel pipes and fittings]

[2.7] DVGW-Arbeitsblatt GW 321: Steuerbare horizontale Spülbohrverfahren für Gas- und Wasserrohrleitungen – Anforderungen, Gütesicherung und Prüfung [Steerable horizontal directional drilling methods for gas and water pipelines – Requirements, quality assurance and testing]

31

Reference documents

[2.8] Gaebelein, W. u. Schneider, M.: Grabenlose Auswechslung von Druckrohren mit dem Hilfsrohrverfahren der Berliner Wasserbetriebe [Trenchless replacement of pressure pipes by Berliner Wasserbetriebe‘s auxiliary pipe technique] GUSSROHRTECHNIK 38 ( 200�), p. 8

[2.9] Falter, B. und Strothmann, A.: Beanspruchungen und Verformungen in der TIS-K-Verbindung beim grabenlosen Auswechseln von duktilen Gussrohrleitungen [Stress and deformations in the TIS-K joint in the trenchless replacement of ductile cast iron pipelines] GUSSROHRTECHNIK �0 ( 200�), p. �1

[2.10] DIN 30�7�-2: Umhüllung von Rohren aus duktilem Gusseisen; Zementmörtel-Umhüllung [Cement mortar coating for ductile iron pipes; requirements and testing]

[2.11] DIN EN 1��2: Rohre, Formstücke und Zubehör aus duktilem Gusseisen – Zementmörtelumhüllung von Rohren – Anforderungen und Prüfverfahren [Ductile iron pipes, fittings and accessories – External cement mortar coating for pipes – Requirements and test methods]

[2.12] DVGW-Arbeitsblatt W �00-2: Technische Regeln Wasserverteilungsanlagen (TRWV); Teil 2: Bau und Prüfung, 09/200� [Technical Rules – Water distribution systems; Part 2: Construction and testing, 09/200�]

[2.13] DIN 2880 Anwendung von Zementmörtel-Auskleidung für Gussrohre, Stahlrohre und Formstücke [Application of cement mortar lining for cast iron pipes, steel pipes and fittings]

32

There has been tremendous progress in the development of no-dig or trenchless techniques for installing new pressure pipelines and replacing old ones, particularly when this has to be done in inner city areas. There is an increasing trend towards the use of these techniques. Whereas large areas are covered with excavated soil when open-trench techniques are used, with trenchless techniques any nuisance of this kind is kept within acceptable limits.

The following are some of the major advantages of trenchless techniques:• The digging-up of roads and earth-moving work are reduced by up to 80% or more

(Fig. 3.1)• There is less excavated soil and bedding material to be transported (Fig. 3.2)• Less space is needed for the site equipment and facilities (this is particularly important

in inner city areas, Fig. 3.3)• Sites can be confined to several small „points“ and it is therefore possible to cover the

pit and put it out of reach of the weather, which benefits the quality of the product, i.e. the pipeline that is installed.

Fig. 3.1 Space required for open-trench installation Fig. 3.2 Open-trench and trenchless installation: comparison of volumes of material transported

Fig. 3.3 Trenchless installation does not disrupt traffic

Trenchless replacement of gas and water pipelines

3. Trenchlessreplacementofgasandwaterpipelines

3General

Open-trench installation Equipment

Trenchless installation

Volume of material transported

33

General

What is said above is true of more or less all trenchless installation techniques. When these techniques are used for renovation, there are the following advantages as well:• the way of working does not create any vibrations and is quiet and this keeps the

nuisance to traffic and to the public to a minimum• there is no damage to trees planted along the streets above the run of pipe.

The major block of costs that are incurred when installing pipelines are the costs for below-ground work. Efforts to reduce these by developing new methods of installation have produced a wide variety of techniques which belong to the family of trenchless or no-dig installation and renovation techniques.The first of these was microtunneling, a steered pipe-jacking technique for the instal-lation of new sewer pipes, this being the field of application where economic success could be achieved most quickly because of the considerable depths involved. What were generally of advantage in this case were sections normally measuring less than �0 metres in length extending in a straight line between two manholes. Since 198� the Berlin tech-nique has been brought to a high level of sophistication. Today, the proportion of new sewer pipes that are installed by this method in Berlin is already �0%.The pipes mainly used for the construction of pressure pipelines are pipes that are con-nected into pipelines locked against longitudinal forces. What are used in this case are Buderus Giesserei Wetzlar GmbH‘s ductile cast iron pipes with their longitudinal force-fit BLS® restrained joints. It was in the 1970‘s that longitudinal force-fit restrained joints began to be used to take the place of concrete counter-bearings. Their advantages for pulling in culvert pipes were recognised and began to be exploited at that time. This marked the beginning of trenchless installation techniques using ductile cast iron pipes.

3�

The greatest impetus to innovate in the field of trenchless replacement came from Ber-lin, where Germany‘s oldest systems of grey cast iron water pipes had by then been in use for more than 120 years and urgently needed to be renovated. There were external conditions in Berlin that made replacement more difficult and these took the form of the following requirements:

1. The pipes are situated in the area where the roots of the trees at the edges of the pavements lie. The trees are strictly protected and under no circumstances may the roots be harmed. It is not possible for trenches to be dug for conventional laying.

2. Replacement techniques where the old pipes remain in place along the run, either unbroken or in fragments, cannot be used. Any pipes or fittings which are not in use have to be removed in their entirety.

This meant that the development of two special pipe replacement techniques, namely the press-pull technique and the auxiliary pipe technique, was almost pre-ordained; specifications serving as a foundation for both these techniques now exist as technical rules laid down by the DVGW in the form of Arbeitsblatt GW 322-1 [3.1] and Arbeits-blatt GW 322-2 [3.2]. Both techniques can be used for the trenchless replacement of pipelines, following the same route, with new pipelines of the same or larger nominal sizes (e.g. new DN 12�/1�0 pipes to replace old DN 100 ones, see Table 3.1), with the pipes making up the old pipeline being recovered either as fragments or as complete lengths. This gives the following advantages:

1. Valuable raw materials are recycled.2. There is only minimal disruption of ground surfaces and nature.3. No new runs of pipe are installed in the space available below ground level.

Table 3.1: Maximum increases in nominal sizes with trenchless replacement to GW 322-1 or GW 322-2

Nominal size of old pipes Maximum nominal size of new pipes

DN 80 DN 1�0

DN 100 DN 200

DN 1�0 DN 200

DN 200 DN 300

DN 300 DN �00

DN �00 DN �00


3�

General

Other pluses that the two techniques have are these:

• There is no need for public-transport bus stops to be moved (see Fig. 3.3).• There is almost no interference with delivery traffic in streets where there are business

premises.• Other utilities carried in pipes are not put at risk by excavation work.• Depending on the machinery used, whose maximum sound emission is less than ��.�

dB(A), the installation work is particularly „quiet“ and free of dust. It is even possible for work in residential areas to continue without any overnight breaks.

Above all when installation work is being done in inner city areas, where there are very closely packed runs of pipe, intersecting pipelines and pipelines running in parallel are very much at risk when heavy-duty digging equipment is used in open trenches. This risk is cut to a minimum when trenchless replacement techniques are employed.

The two techniques can both be used for supply pipelines of nominal sizes ranging from DN 80 to DN �00. What are required are:• a machine pit to hold the machinery,• an installation pit (about 7 metres long) for the new pipes,• intermediate pits for the house connections or branch pipelines.

The distance between the intermediate pits depends on the nominal size of the old pipe-line and on the condition it is in, on the nominal size of the new pipeline, on the machin-ery used, on the nature of the soil, on the trees present and their roots and of course on the conditions relating to traffic and the medium involved. Depending on the technique and the locality, the distance between the intermediate pits should not be more than 2� to �0 metres. With a straight run of pipes or one with a radius of curvature of not more than 170 metres, the distance between the launch and arrival pits is normally from 100 to 180 metres. Before the replacement operation, the old pipeline has to be taken out of service. The supply of the adjacent houses and other premises is maintained through temporary interim pipelines, the water from which is fed into the house connecting pipes, the ends of which have been closed off, in the pits for the house connections.

3�

3.1Thepress-pulltechnique

With this technique, the old pipe is pressed onto a breaker cone and shattered and is removed from the machine pit in fragments. The new pipes, which have longitudinal force-fit restrained joints – e.g. Buderus BLS® joints – are hooked on at the end of the last old pipe by means of a traction head and are pulled into the cavity which is left free. The two steps take place simultaneously.

Once the pits required have been dug and lined, the sections of old pipeline contained in them are cut out and removed. Specially prepared launch/assembly pits make it easier for the pipes to be installed and stop any fouling or contaminants from getting it (Fig. 3.�). First of all, a traction linkage which can be coupled together is pushed through the old pipeline and anchored to an adjusting adapter at the end of the old pipeline, thus allowing the old pipes to be pressed out of the earth in the course of the replacement operation. No fragments are left in the bedding zone for the new pipeline. The new pipes are fastened to the adjusting adapter and, as the old pipe is pushed out, they are pulled in behind it at the same time.

Fig. 3.4 A DN 150 pipe in the pull-in pit


37

Fig. 3.5 Hydraulic unit

The press-pull technique

Via the adjusting adapter, the tractive forces from the traction linkage are applied to the end of the old pipeline as axial thrust forces. Hence the only traction-generated forces which act on the new run of pipe that is being pulled in are those generated by its own weight and the friction against its outer circumference. Arbeitsblatt GW 322-1 requires these forces to be continuously measured and recorded so that the new pipeline will not be stressed by tractive forces higher than those permitted. The measurement of the tractive forces is proof that the permitted load has not been exceeded during the replace-ment operation (for quality assurance). The socket acts in a similar way to a bore-widen-ing device, which means that it is generally only at the socket that forces are generated by friction against its outer circumference. The �-metre long main body of the pipe on the other hand, which is smaller in diameter, plays no part in generating any such frictional forces. Points of intended fracture, audio warnings of overloads, and similar provisions are not good enough as a guarantee of safety.

The hydraulic press-pull unit is supported against the rear wall of the arrival pit via a steel abutment plate (Fig. 3.�). This plate is sized to suit the reaction forces and the nominal size of the pipes and there is only a small gap between it and the pipe so that, as far as possible, no earth will be forced into the pit.

Fig 3.7 The technique takes place in three steps

Launch pit 1st pull-in step

intermediate pit intermediate pit Machine pit/arrival pitwith press-pull unit

New pipeline

Traction head

Breaker cone

Old pipeline

Traction linkage

Abutmentplate

38

The hydraulic traction cylinders of the press-pull unit allow the old pipes to be pressed out without percussion or jerks. In the intermediate pits (Figs. 3.7 and 3.8), the old pipe is slid over a breaker cone or is smashed into pieces by an automatic pipe smasher (Fig. 3.9). The fragments are conveyed to the surface in bins. In the final pull-in step, the old pipe, as it is pulled into the arrival pit, is generally broken as the traction cylinders made their backward stroke (Fig. 3.10).

Fig. 3.8 Next step of the operation: Changing over the breaker cone in the intermediate pits

Fig. 3.9 The hydraulic pipe smasher

Fig. 3.10 Final step: Changing the breaker cone over to the destination pit


2nd pull-in step

New pipeline Traction head Breaker cone

Old pipeline

Traction linkage

Abutmentplate

3rd pull-in step

New pipeline Traction head

Breaker cone

Old pipeline

Traction linkage

Abutmentplate

39

3.2Theauxiliarypipetechnique

In the auxiliary pipe technique, the replacement process is divided into a number of steps.As in the press-pull technique which was described in section 3.3, in this case too a machine pit and a launch/assembly pit are required, together with the intermediate pits at house connections or branch pipes. The distances between the individual pits are similar.In the first step, the installing and intermediate pits are dug, the connecting pipes to houses are sealed off and the pipes to provide an emergency supply are connected up (Fig. 3.11).

The auxiliary pipe technique

Fig. 3.11 Making the assembly/launch pit and cutting the old pipes in the intermediate pits

Missing pieces of the old pipe, resulting from the removal of house connections or similar are replaced by transition pieces. Then, by means of auxiliary steel pipes connected by longitudinal force-fit restrained joints, the pressing unit presses the old pipes into the assembly/launch pit until they have all been removed (Fig. 3.12)

Fig. 3.12 Pressing out the first, second and third sections of the old pipe by means of an auxiliary pipe

Machinery pit with pipe replacing unit

intermediate pit Pipe assembly/launch pit

Old pipe

Hydraulics intermediate pit

Old pipeOld pipeAuxiliary pipe


intermediate pit Launch/assembly pit

Old pipe

Hydraulics intermediate pit

Old pipeOld pipeAuxiliary pipeTransition

pieceTransition

piece

�0

It may be helpful in this case for individual sections to be detached by means of hydraulic jacks before the entire run of old pipe is pushed through into the launch/assembly pit. Because sections measuring up to � metres in length can be removed from this pit, the technique is also an obvious one to use for the replacement of old steel pipes, because these cannot be burst over a breaker cone (Fig. 3.13).

Fig. 3.13 Full-length old pipes

The whole of the last old pipe having been removed, the run is filled by the re-usable auxiliary pipes (Fig. 3.1�). These now carry the loads from the top cover and the traffic load and thus safeguard the bore for the pipeline.

Fig. 3.14 Auxiliary pipes occupying the whole of the run


Pipe assembly/launch pit


intermediate pitHydraulics intermediate pit

Auxiliary pipe

�1

In the final stage of the operation, the new pipe is coupled to the auxiliary pipes present in the bore for the pipeline by means of a traction head with built-in facilities for measur-ing tractive force. The auxiliary pipes are pulled back into the machine pit and the new pipeline is thus drawn into the existing bore (Fig. 3.1�). The assembly of the new pipes in the launch/assembly pit proceeds in parallel with the dismantling and removal of the auxiliary pipes in the machine pit. If a traction head which enlarges the bore is used, new pipes of larger sizes can be pulled in. Operations usually take place with a small oversize of 10 to 1�% on top of the outside diameter of the sockets.

If the old pipe is unable to withstand the compressive forces which can be expected, it is cut in the intermediate pits and removed in short section.The permitted tractive forces for the new pipe and its joints must not be exceeded.

The auxiliary pipe technique

Fig. 3.15 Pulling-back of the auxiliary pipe and pulling-in of the new one

Pipe assembly/launch pit


intermediate pitHydraulics intermediate pit

Auxiliary pipe New pipeTraction head with force-measuring equipment

�2

3.3Requirementsforthenewpipe

The new pipe and its joints have to withstand high tractive forces and still have to have large safety margins when they do so. The pipe has to have rugged outside protection because it cannot be guaranteed that there will not be any debris, stones or fragments in the zone where the pipeline is situated. It is important for the traction head to be able to be fitted and removed quickly and straightforwardly when it is being recovered, even when the weather is very bad. The pipe and its joints have to be long-lived and resistant to tree roots. Because the paths followed by many pipelines are not exactly straight, it is vital for the sockets to be able to accommodate angular deflections. In inner-city areas, launch pits are a maximum of 7 metres in length so the ratio between the size of the launch pit and the number of joints to be made is very good. Because a combination of trenchless and open-trench techniques is often used, the types of pipe used have to be compatible and there has to be a complete range of fittings available, including for use in the intermediate pits.Buderus ductile cast iron pipes with cement mortar coatings and BLS® joints have all these essential prerequisites. They are thus the ideal pipes for the trenchless replacement of pipelines. What is more, there are fittings for performing leak tests which are very easy to use and which are easily fitted and removed. The requirements in respect of permitted tractive forces, angular deflections and minimum radiuses of curves which have to be met under the DVGW rules and the internal rules of Berliner Wasserbetriebe are given in Tables 2.1 and 2.2 in section 2.When the technique is being used in sandy soils, the external shape of the socket, with its shoulder-like transition to the main body of the pipe, has been found to be very successful. Where, in soils containing non-cohesive material, there is a transition to material of this kind individual pebbles tend to roll under the main body of the pipe during the pulling-in process, and the entire pipe string thus undergoes an upward movement as it is pulled in. The result may be excessively thin cover over the pipe and even pushing-up of the

pavement at the surface. For special cases of this kind, Buderus has developed the ZMU-PLUS pipe on which the transition between the main body and the socket is filled in with additional layers of the cement mortar coating so that the upward movement described above will not occur (Figs. 3.1� and 3.17).


Fig. 3.16 A stack of DN 300 ZMU-PLUS pipes

�3

Requirements for the new pipe

3.4Requirementsforthesite

It goes without saying that when trenchless installation techniques are being, exacting demands are made not only on the pipes and the accessories but also on the machin-ery used by the companies doing the work and on their qualified specialist personnel. There has to be sophisticated quality assurance system in this case to ensure a high standard of safety and quality for the new pipeline. The company provides evidence that it is suitably qualified by having the appropriate certification under DVGW Arbeits-blatt GW 301 [3.�] in supplementary group GN 1. This ensures that the pipeline which is installed by trenchless means will meet the demands that are made on it not only from the point of view of cost of installation but also in the long term, even beyond the full operating life that is demanded. For a deposit, Buderus Giesserei Wetzlar GmbH will supply traction heads, which can also be used for other trenchless installation techniques, on hire. There are now a wide variety of variant traction heads which can be obtained through machinery suppliers.

Fig. 3.17 ZMU-PLUS sockets and an inserting end

��

3.5Referencedocuments

[3.1] DVGW Arbeitsblatt GW 322-1: Grabenlose Auswechslung von Gas- und Wasserrohrleitungen – Teil 1: Press-/Ziehverfahren – Anforderungen, Gütesicherung und Prüfung)

[Trenchless replacement of gas and water pipelines – Part 1: Press-pull method – Requirements, quality assurance and testing]

[3.2] DVGW-Arbeitsblatt GW 322-2: Grabenlose Auswechslung von Gas- und Wasserrohrleitungen – Teil 2: Hilfsrohrverfahren – Anforderungen, Gütesicherung und Prüfung

[Trenchless replacement of gas and water pipelines – Part 2: Auxiliary pipe method – Requirements, quality assurance and testing]

[3.3] DIN EN ��: Rohre, Formstücke, Zubehörteile aus duktilem Gusseisen

und ihre Verbindungen für Wasserleitungen – Anforderungen und Prüfverfahren [Ductile iron pipes, fittings, accessories and their joints for water

pipelines – Requirements and test methods]

[3.�] DVGW-Arbeitsblatt GW 301: Qualifikationskriterien für Rohrleitungsbauunternehmen

[Qualification criteria for pipeline construction companies]


��

Reference documents

��

The burst lining technique is used for the trenchless renovation of pipelines where the pipeline is to follow the same path. For this purpose, the existing old pipeline is destroy-ed by a bursting head and at the same time the fragments are pushed into the surroun-ding soil and the new run of pipe is pulled in.

With burst lining, a distinction is made between the dynamic and static variants.

In its dynamic form (Fig. �.1), the burst lining technique was developed from the tech-nique that uses a rocket plough with a widening head and was originally used for the renovation of stoneware sewer pipes. However, where adjacent lines and structures were too short a distance away, they were found to be at risk from the vibrations that were generated.

This was why the static variant of the burst lining technique was subsequently developed. In this case a widening head (Fig. �.2), the first widened part of which may be fitted with breaker ribs (Fig. �.3), is pulled through the old pipeline by pulling units which operate continuously and without any vibration, and in this way the old pipeline is burst open. The new pipes are coupled straight to the bursting/widening head and are pulled into the bore, which is widened to approximately a 10% oversize.

4. Theburstliningtechnique

The burst lining technique

4.1General

Fig. 4.1 The dynamic variant of the burst lining technique

�7

Both the variants of the burst lining technique, both the static one and the dynamic one, are in practical use at the present moment and are widely used. The DVGW has catered for this fact with its Merkblatt GW 323 [�.3] and has thus established criteria for the execution of the techniques and also the related requirements and quality assurance measures. The burst lining technique is particularly well suited to old pipes made of brittle materials such as asbestos cement, stoneware and grey cast iron. Ho-wever, by using the static variant and special cutting heads it is also possible for steel and ductile cast iron pipes to be burst. The new pipe which is pulled in may be of the same nominal size as the old pipe or, as dictated by the widening head which is used, of a larger size. (The widening head has to be at least the same size as the socket of the new pipe).

Another advantage that the burst lining of old pipes can be considered to have is that, compared with replacement in open trenches, there is none of the tricky work of hand-ling the old pipes that there is in open trenches and none of the problems with safety at work which this causes. This is true whether replacement is to the same nominal size or a larger one. An increase in nominal size of up to two increments is possible. If the new pipeline can be smaller than the old one, an attractive alternative is pipe relining (see section 7).

In the field of distribution systems, the use of the burst lining technique (or of any trenchless replacement technique) depends mainly on the number of intermediate pits required. Intermediate pits should be set up for house connections, fittings, changes of direction and cross-section and branch pipes. Bends up to 11° can usually be passed through. If there is too close a succession of house connections, open trench replace-ment may be more economical [�.�]. Equally important is the accuracy of the documen-tation on the existing old pipeline. If there are too many „surprises“ during the installati-on phase, the customer may find himself faced with a plethora of additional charges.

Fig. 4.2 Widening head and cast iron pipe Fig. 4.3 Bursting head with breaker ribs

General

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4.2Adescriptionofthetechnique

As has already been mentioned, a distinction is made between the dynamic and static variants. In both, a bursting head is used to apply forces to the old pipeline which de-stroy it. Brittle materials are burst apart into fragments (�.�) and all the others are cut open (Fig. �.�). The fragments or the cut-open parts of the pipe are pushed into the surrounding soil.

4.2.1Thedynamicvariant

The force required for bursting is applied in the longitudinal direction of the pipe by a sort of soil rocket. This is driven by a compressor which is connected to it by a flexible hose. To guide the bursting head, it is pulled along by a winch from the arrival pit on a hook-equip-ped pulling rope which is pulled through the old pipe. The dynamic variant is particularly suitable for highly compacted and stony soils and for old pipes which are brittle.

Fig. 4.4 Fragments of grey cast iron Fig. 4.5 An old pipe that was cut open under control

Fig. 4.6 The staticvariant

4.2.2Thestaticvariant

In this case the force is applied to the bursting head by a traction linkage which, starting from the arrival pit, runs from the pulling unit through the old pipeline to the bursting head (Fig. �.�).

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During the pulling process, the traction unit is supported against the wall of the arrival pit. Successive parts of the traction linkage are taken apart backwards. The static variant is well suited to homogeneous soils which can be displaced easily.

There has now also been practical experience of the replacement of ductile pipe materi-als (ductile cast iron and steel) with pipes of ductile cast iron. In this case the old pipes are cut open (Fig. �.�) with special perforating and cutting wheels (Figs. �.7 and �.8) and are bent open by the widening head which follows sufficiently far to allow the new pipeline to be pulled in after the head. Trials of the use of this technique have been conducted up to a nominal size of DN �00 [�.1]

There have also been isolated instances where combinations of ductile cast iron pipes for the water pipeline and a plastic pipe as an accompanying duct to protect cables have been pulled into a steel pipe which had been cut open (Fig. �.9).

A description of the technique

Fig. 4.7 Perforating wheel for ductile materials Fig. 4.8 Roller cutting blade

Fig. 4.9 Traction head for pull-ing in two pipes in parallel

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4.3Pipelinematerials

Because the soil conditions are generally unknown and above all because of the sharp-edged fragments (Fig. �.�) which most certainly occur with the burst lining technique, care should be taken to see that the pipeline material used is one which is not sensitive to factors of this kind.

4.3.1Outsideprotection

The coating of plastic-modified cement mortar (ZMU) which is used on ductile cast iron pipes provides excellent protection against the risks which are mentioned above. The socket joint is fitted with a cement mortar protecting sleeve or a shrink-on sleeve and is protected by a sheet-metal cone (Fig. �.10).

Plastic pipes may only be used if they have a protective outer sheath. (Please note that the investigations described in GWF 3/2000 [�.�] clearly indicate that even this protec-tive outer sheath does not always provide protection against damage to the pipe within it caused by point loads.)

Fig. 4.10 Ductile cast iron pipe with a BLS® joint, cement mortar coating, shrink-on sleeve and sheet-metal cone

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4.3.2Joints

As in virtually all trenchless installation techniques, so with the burst lining technique too, there are quite high forces which are applied to the joints between the pipes and to the bodies of the pipes. The obvious course is therefore to opt for the joint which, of all the current pipe materials, is the one which has the highest permitted tractive forces, namely the BLS® restrained joint (see Fig. 2.19 on page 22). Where this is particularly important is in highly compacted and rocky soils because it is precisely in these that very high tractive forces may occur. The permitted tractive forces for the BLS® joint can be seen from DVGW Arbeitsblatt GW 323 or from Table 2.1 on page 20. A rule that applies generally is that on-line measurements must be made and documented to ensure that the maximum permitted tractive forces are being observed. It must be re-membered in this case that the permitted tractive forces have to be reduced for plastic pipes as a function of their temperature and of time.

4.4Tosumup

Ductile cast iron pipes with a cement mortar coating and BLS® joints are outstanding well suited to the burst lining technique. The principal factors are the particularly high loads the BLS® joint is able to carry and the extremely highly resistant cement mortar coating, which means that you can be sure of getting a pipeline which will be both safe and reliable in the long term. Table �.1 shows a selection of pipelines that have already been installed by Buderus using the burst lining technique.

InstallationsNominal size

DNLength

[m]Year

Erfurt 1�0 12� 2001

Gladenbach - Erdhausen

1�0 700 200�

100 �0 200�

Bad Laasphe 100 �00 200�

200 �00 2007

Ober Rabenstein 2�0 3000 200�/07

Zittau 200 �00 2007

Siegen 1�0 2�0 2007

Table 4.1 Excerpt from the list of reference installations made by the burst lining technique us-ing Buderus Giesserei Wetzlar GmbH ductile cast iron pipes

Pipeline materials

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[�.1] Levacher, R. Erneuerungen einer Verbindungsleitung DN �00 zwischen zwei Wasserwerken im Berstlining- und Spülbohrverfahren [Renovations of a DN �00 connecting pipe between two waterworks by the burst lining and directional drilling methods] GUSSROHRTECHNIK �0 (200�), p. 17

[�.2] Klemm, K. und Rink, W.: Einbau duktiler Gussrohre DN 2�0 mit dem Berstlining-Verfahren in Nähe der Burg Rabenstein bei Chemnitz [Installation of DN 2�0 ductile cast iron pipes by the burst lining technique close to Rabenstein Castle near Chemnitz] GUSSROHRTECHNIK �1 (2007), p. �7

[�.3] DVGW–Merkblatt GW 323, Grabenlose Erneuerung von Gas- und Wasserversorgungsleitungen durch Berstlining ; Anforderungen, Gütesicherung und Prüfung, Juli 200� [Trenchless renovation of gas and water supply pipelines by the burst lining method; requirements, quality assurance and testing, July 200�]

[�.�] Emmerich, P. und Schmidt, R.: Erneuerung einer Ortsnetzleitung im Berstliningverfahren [Renovation of a pipeline in a local system by the burst lining method] GUSSROHRTECHNIK 39 (200�), p. 1�

[�.�] GWF Heft Wasser/Abwasser, 1�1. Jahrgang, Oldenburg Industrieverlag München, März 2000 – Punktbelastung an Kunststoffrohren von Uhl, Haizmann (FHW Oldenburg) [Point loading on plastic pipes by Uhl, Haizmann (Oldenburg School of Economics)]


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Reference documents

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Since the early 1990‘s, there has been a close relationship between the development of this technique and ductile cast iron pipes. Back in 1993, Nöh [�.1] conducted some exploratory tests in which �0 m long DN 1�0 pipelines with positive locking joints were installed and were then withdrawn again from the bore to allow the surface stresses which had occurred to be assessed. The excellent results provided the justification for a 2 x DN 1�0 double culvert pipe about 200 metres long which was pulled in under the river Mosel in 199� at Kinheim, partly through rocky subsoil.

5. Thehorizontaldirectionaldrillingtechnique

Fig. 5.2 Arrival at the arrival pitFig. 5.1 Pre-assembled DN 500 pipeline

The horizontal directional drilling technique

5.1General

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Fig. 5.3 Assembly of the string of DN 900 pipes in a floodable trench

Fig. 5.4 The string of DN 900 pipes floating in the trench when flooded

Fig. 5.5 Beginning of the pulling-in with a bar-rel reamer ahead of the string of pipes

After this satisfactory experience, development went ahead at a very rapid pace: In 199� the pipes were of DN �00 size [�.2] (Figs. �.1 and �.2), in 2000 the bar was raised to DN �00 [�.3] and in 2003 DN 700 pipes were pulled in by the horizontal direc-tional drilling technique in the Netherlands [�.�]. The current record – held by Buderus Giesserei Wetzlar GmbH pipes with BLS® joints and ZMU – is approximately �00 metres of DN 900 pipes in Valencia in Spain (Figs. �.3 to �.�).In parallel with this the DVGW was developing technical rules for the technique, and these took the form of Arbeitsblatt GW 321 Steuerbare horizontale Spülbohrverfahren für Gas- und Wasserrohrleitungen – Anforderungen, Gütesicherung und Prüfung [Steer-able horizontal directional drilling methods for gas and water pipelines – Requirements, quality assurance and testing], which was published in October 2003 [�.�].

General

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The steerable horizontal directional drilling technique (HDD), which will be referred to below simply as the directional drilling technique, is the most widely used trenchless technique for installing new pressure pipelines for gas and water supply. DVGW Arbeitsblatt GW 321 gives rules relating to requirements, quality assurance and testing for it to ensure that quality is properly assured.

The sequence of operations in the directional drilling technique is generally divided into the following three successive steps:• a pilot bore• an upsized bore or bores• pulling-in

5.2.1Thepilotbore

This is the first step in producing a bore, running from the starting point to the arrival pit, into which the string of pipes can be pulled. The pilot bore is driven under steered control by a drilling head at the tip of a drilling string. Emerging at high pressure from the drilling head as it drives is an aqueous suspension of bentonite, the so-called drill-ing mud, which is pumped through the drilling string to the drilling head by the drilling machine. The drilling mud serves both to carry away the material which is cut away and to support the bore. There are different designs of drilling heads for all types of soil. In sandy soils, all that is generally needed for detaching and carrying away the cuttings are

Fig. 5.6 Drilling head for the pilot bore


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the outlet nozzles. In rocky soils, drilling heads fitted with roller chisels can be used. The pilot bore is steered by controlled rotation of the bevelled steering surface of the drilling head. This surface moves off-line and it can be forced to move off-line in the desired direction by rotating it (Fig. �.�).The actual position of the drilling head is detected above the path of the bore by means of radio signals from a transmitter housed in the drilling head. Any deviations from the desired line are corrected by appropriate steered movements. Today, the accuracy of steering is so high that, after being driven for a length of more than 1000 metres, pilot bores can be made to arrive within a target area measuring only a square metre in size.

Fig. 5.7 The tool for the first stage of upsizing

Fig. 5. 8 The tool for the second stage of upsizing

5.2.2Theupsizedboreorbores

If the pilot bore needs to be upsized, suitable tools are used to upsize it, in a number of stages, to a diameter suitable for the pulling-in of the medium-carrying pipe. For this purpose, an upsizing head is fitted to the pilot drilling linkage, the size and configura-tion of this head being governed by the particular soil conditions and the size of the pipe which is subsequently going to be pulled in (Figs. �.7 and �.8). The upsizing head is pulled through the bore while rotating continuously and in this way it enlarges the size of the pilot bore. The soil which is cut away is carried out with the drilling mud and this latter supports the bore at the same time. The upsizing process is repeated with increasingly large heads until the bore is of the desired inside diameter.


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5.2.3Pulling-in

Once the bore has reached its final diameter, the string of pipes can be pulled in. A reaming tool (Fig. �.9), then a rotary joint that stops the string of pipes from turning with the reaming tool, and then a traction head matched to the pipes that are going to be pulled in (Fig. �.10) are fitted to the drilling linkage which is still in the bore. The traction head is connected to the string of pipes by friction locking and positive lock-ing. The length of the string of pipes depends on local conditions. When the site is very cramped for space, part-strings can be assembled or even single pipes can be installed. When this has to be done, the pulling-in process is stopped after whatever length of string is possible in the given case and another part-string is coupled on. Drilling mud is also pumped through the drilling linkage while the pulling-in is progressing. It emerges from the reaming tool and as it does so carries away the drillings and at the same time lessens the frictional forces. The forces which act on the new string of pipes when it is being pulled in have to be measured and a record has to be kept of them.

Fig 5.9 Reaming tool


Fig. 5.10 DN 900-BLS® traction head

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5.3Generalrequirements

Companies with which orders for directional drilling operations are placed must have the requisite qualifications. This is considered to be the case if the company holds a DVGW certificate under DVGW Arbeitsblatt GW 301 [�.�] or GW 302 [�.7] as the case may be, in the appropriate class GN 2. As well as this, a specialist supervisor who is qualified under DVGW Arbeitsblatt GW 329 [�.8} has to be appointed within the company.

5.3.1Pipesandjoints

The pipes and joints must be suitable for the stresses which the technique produces. The permitted tractive forces, radiuses of bends and angular deflections are specified in Appendix A to Arbeitsblatt GW 321 for the usual pipe materials, namely steel, cross linked polyethylene (PE-X), PE 100 and ductile cast iron (see also Table 2.2 in section 2). Depending on the material, the pipes may have to be given suitable outside protec-tion which will protect them against damage such for example as scoring.

5.3.2Ductilecastironpipes

Ductile cast iron pipes to DIN EN �� (for drinking water) or DIN EN �98 (for sewage) are particularly suitable for trenchless installation by the directional drilling technique. A first feature which can be mentioned as being of significance in this connection is the actual material of the pipes. Ductile cast iron has the ability to survive extreme loads unscathed. Hence there is also virtually no chance of the wall of the pipe suffering damage from objects lurking unseen within the ground.

Another excellent feature is the outside protection. Ductile cast iron pipes for the directional drilling technique are provided with a five millimetre thick coating of plastic-modified cement mortar (ZMU) to DIN EN 1��2 [�.9]. This effectively prevents any damage to the body of the pipe and is suitable for soils of whatever aggressiveness (under DIN 30�7�-2 [�.10]).

The third prerequisite for the use of ductile cast iron pipes for the HDD technique is the BLS® restrained joint. The BLS® restrained joint, which is a longitudinal force-fit joint and a positive locking joint combines functionality and easy, quick and secure assembly. Without any great effort, it can be assembled in a matter of minutes even under the most adverse conditions, such as ice and snow. In this way it cuts the amounts

General requirements

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of time that are lost during the pulling-in process when single pipes or part-strings are being fitted together to an almost irreducible minimum. At the same time it has, under DVGW Arbeitsblatt GW 312, the highest permitted tractive forces of all the usual pipe materials which are used for installing pipelines. These permitted tractive forces can be used without being reduced in any way the moment the joint has been assembled. Cooling times or reductions in the tractive forces due to high pipe-wall temperatures or ambient temperatures or due to protracted pulling-in times are unknown when ductile cast iron pipes are being installed. The permitted tractive forces, operating pressures and angular deflections are given in Table 2.1 in section 2. For the maximum permitted tractive forces given in the table, the use of an (additional) high-pressure lock is laid down for nominal sizes from DN 80 to DN 2�0. The operating pressures and tractive forces shown are based on a wall thickness class of K9. Higher figures, both for operating pressure and also for tractive force, are possible by, for example, increasing the wall thickness class. If the angular deflections are ≤ 0.5° per joint, the figures quoted can be raised by a further �0 kN. Because of the angular deflections of up to �° which are possible at each joint, a very small radius of curvature of only �9 metres can be achieved.

With regard to protection for the joints, the following options are available:• a sleeve of heat-shrink material to DIN 3072• a sleeve of heat-shrink material to DIN 3072 plus a sheet-steel cone• a cement mortar protecting sleeve plus a sheet-steel cone.The crucial factor in deciding on the protection for the socket is the installation tech-nique which has been selected.

There are basically two variant procedures that can be followed in pulling in ductile cast iron pipes:1. pulling-in of a string or part strings of pipes2. pulling-in of individual pipes.

A point in favour of the first variant, the pulling-in of a string of pipes, is that the string of pipes is first assembled from individual pipes and is then filled with water and pressure tested before being pulled into the bore which has now been completed. For a long time, this variant was even laid down by insurers because it was considered safest. Dur-ing the pulling-in there is only a brief interruption in the traction to allow the traction rod to be removed at the machine end. The time this takes has to be kept as short as possible to stop the thixotropic effect from taking place in the drilling mud. This effect causes it to solidify.


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A prerequisite for this procedure is sufficient space for a complete pipe string, or part-strings situated next to one another, to be assembled. A disadvantage is the total weight of the pipe string, which increases the tractive forces required due to the friction of the string against the ground on which it is resting. This friction can be reduced by, for example, sheets of metal greased with lubricant on which the string is assembled or by inflated rubber rollers. If there are water-filled channels available, the string can float in them (Fig. �.�). Generally speaking, it has to be said that the pulling-in of a complete string (Fig. �.1) destroys the advantage of the point sites which are used in trenchless installation techniques. Basically, this is true no matter what the material of which the pipes are made. The pulling-in of single pipes is particulary suitable for point sites but normally cannot be used for pipes which have to be joined together into strings by welding because the time taken by the welding and cooling and by the testing of the welds is too long. The inevitable consequence is that the drilling mud solidifies due to thixotropy.

This is where the advantage of the BLS® joint lies. The time taken to assemble the Buderus BLS® joint is short and is similar to the time required to remove the traction rod at the machine end (see Table 2.� in section 2). This gives ductile cast iron pipes with BLS® joints an unbeatable lead over pipes of other materials, with the possible exception of PE pipes supplied in coils. The space required at the end from which the pipeline is pulled in is only slightly more than the length of a pipe. Launch pits seven to eight metres in length are generally all that are required (Fig. �.11), or else the pipes are joined together on an assembly ramp. A point site is possible with these latter pipes. There are no forces generated by friction on the ground below which have to be allowed for and in general the next smaller size of machine can even be used, which

Fig. 5.11 General diagram of an assembly pit

Allgemeine Anforderungen

7 - 8 m

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is another thing which has beneficial effects on cost. The connecting together of single pipes on a ramp also has the advantage that the work can be done at eye level, virtually under workshop conditions, which is important from an ergonomic point of view (Fig. �.12). Another inestimable advantage with regard to drinking water hygiene and the subsequent release that is required is that the assembly of the joints on a ramp takes place some distance away from any dirt and mud.

Fig. 5.12 Assembly ramp

Fig. 5.13 cement mortar protecting sleeve with a sheet-metal cone

It is clear that the gain in speed with the variant procedure described above must not be lost again by the application of a heat-shrink sleeve. This is where the cement mortar protecting sleeve serves its purpose. It can be quickly and easily rolled on and it has a sheet-metal cone to protect it against the unknown roughnesses which may be present in the bore. This cone is slid over the socket of the pipe, together with the cement mor-tar protecting sleeve, before the joint is assembled. Once the joint has been assembled, it is moved into position (Fig. �.13) and folded in at the edge if required.


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Table �.1 provides an overview of the possible ways of protecting the joint with the different variant procedures:

Table �.1: Possible ways of protecting the joint

General requirements

Variant Outside protection Joint protection

Pulling-in of single pipes ZMUCement mortar protecting

sleeve plus sheet-metal cone

Pulling-in of pipe strings or part-strings

ZMUCement mortar protecting

sleeve or shrink-on sleeve plus sheet-metal cone 1)

1) Information on this subject can be found in our product catalogues. Shrink-on sleeves of tape material should be avoided on directionally drilled pipelines if at all possible.

The two installation procedures mentioned above, namely the pulling-in of single pipes and the pulling-in of pre-assembled pipe strings or part-strings, are used as dictated by the amount of space available on site. In built-up inner city areas, it is, for the most part, the pulling-in of single pipes which has to be considered. A launch pit about seven to eight metres in length is required for this. Assembly and the protecting of the sockets take place in the pit. Interference with the surface of the street can be even smaller if the pipes are joined together on a mobile ramp. Depending on the governing condi-tions, such as nominal diameter, supporting ground and the preparation of the sliding surface of the pipe string, lengths of some hundreds of metres can be pulled in.

Example:DN 200 ductile cast iron pipes with cement mortar coating, BLS® joints and high-pressure locks, wall thickness class K9• permitted tractive force Fzul: 3�0 kN (PFA �� bar)• weight of pipe Gpipe: 271,5 kg = 45,25 kg/m ≈ 0,46 kN/m• coefficient of friction µ = 1,0What is thus obtained for the permitted length of the pipe string, from the formula Lperm = Fperm / (Gpipe * µ) = 350 kN / (0,46 kN/m * 1,0) ≥ 7�0 m

In many cases, the coefficient of friction µ that will occur will be appreciably less than 1.0, thus enabling substantially longer lengths to be installed. In this way, coefficients of friction of between 0.�� and 1.0 were found in a series of measurements of tractive force made on DN �00 pipes and the average was µ = 0.78 [�.11]

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5.4Tosumup

In their current form, Buderus Giesserei Wetzlar GmbH‘s ductile cast iron pipes with coatings of plastic-modified cement mortar and BLS® restrained joints are not only suit-able for laying in open trenches but are also a useful alternative when modern trenchless installation techniques, such as steerable horizontal direction drilling, are being used. They combine a very simple joint system which can be assembled quickly and under almost any conditions but is still able to carry high loads with a coating which is equal to the demands made on it. What is more, the pipes will withstand virtually all the external stresses that occur in directional drilling and their material has what is by far the longest technical operating life of all pipe materials under DVGW Hinweis W �01 [�.12].

Ductile cast iron pipes are the right choice when it is a matter of making a lastingly worthwhile capital investment. Word has spread that this is the case, and proof of this can be seen in the many pipelines that have been installed in recent years and decades using the horizontal directional drilling technique. The list of reference installations giv-en in Table �.2 can only show a small number of the most interesting of these directional drilling projects.


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Installations Nominal size DN

length[m] Year

Valencia, Spanien 900 ��0 2007

Blankenfelde Mahlow, Kreuzung L�0 300 90 200�

Schwante, Dorfstraße 300 192 200�

Nieder Neuendorf, Düker Havelkanal 200 3�0 200�

Wolfenbüttel �00 2�� 200�

Halle, Maxim-Gorki-Straße 1�0 28� 200�

Rügen, Prora 3. BA3002�0

�2��0

200�

Großbeeren, Kleinbeerener Straße 300 12� 200�

Nieder Neuendorf, 1 BA 200 3�� 200�

Eichwalde 300 12� 200�

Berlin Frohnau 100 78 200�

Münster bei Dieburg 100 90 200�

Dieburg, Groß-Umstädterstr. 1�0 208.� 200�

Pegau 300 300 1998

Schönebeck, Abwasserdruckleitung �00 220 1997

Rostock �00 180 1997

Wutha �00 ��0 1997

Henningsdorf �00 �22 199�

Oranienburg �00 �32 199�

Frankfurt am Main 100

1801�� 90 80 70

199�

Offenbach 100100270280

199�

Kinheim, Moseldüker 1�0 2 x 172 199�

Table �.2: List of reference installations on Buderus Giesserei Wetzlar GmbH‘s most important HDD projects

This list of reference installations shows only a few of the installations which have been made by directional drilling using ductile cast iron pipes and is intended to provide an over-view of the opportunities which exist and of the wealth of experience that we have had with installation work of this kind.

List of reference installations

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[�.1] Nöh, H.: Moseldüker Kinheim, grabenloser Einbau von Gussrohrleitungen mit der FlowTex-Großbohrtechnik

[Kinheim culvert under the Mosel. Trenchless installation of cast iron pipelines by the FlowTex large-bore drilling technique]GUSSROHRTECHNIK 30 (199�) p. 2�

[�.2] Hofmann, U. u. Langner, T.: Einziehen eines �32 m langen Rohrstranges DN �00 mit gesteuerter Horizontalbohrtechnik – ein wichtiger Beitrag zum Umweltschutz in Oranienburg an der Havel

[Pulling in of a �32 m long DN �00 pipe string by the steered horizontal directional drilling technique – An important aid to environmental protection in Oranienburg on the Havel]

GUSSROHRTECHNIK 32 (1997) p. �

[�.3] Fitzthum, U.; Jung, M. u. Landrichter, W.: Eine Baumaßnahme der besonderen Art: 1100 m Leitungsbau mit duktilen Gussrohren DN �00 blieb von den Anliegern in Fürth unbemerkt

[A special kind of construction project: local residents did not notice the installation of a 1100 m long pipeline of DN �00 ductile cast iron pipes]

GUSSROHRTECHNIK 3� (2000) p. 33

[�.�] Renz, M.: Rekordpremiere mit duktilen Gussrohren DN 700 im Spülbohrverfahren in den Niederlanden

[A record first for DN 700 ductile cast iron pipes installed by the directional drilling technique in the Netherlands]

GUSSROHRTECHNIK 37 (2003) p. 3�

[�.�] DVGW Arbeitsblatt GW 321: Steuerbare horizontale Spülbohrverfahren für Gas- und Wasserrohrleitungen – Anforderungen, Gütesicherung und Prüfung, Okt. 2003

[Steerable horizontal directional drilling methods for gas and water pipelines – Requirements, quality assurance and testing]


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[�.�] DVGW Arbeitsblatt GW 301: Qualifikationskriterien für Rohrleitungsbauunternehmen Juli 1999

[Qualification criteria for pipeline construction companies, July 1999]

[�.7] DVGW Arbeitsblatt GW 302: Qualifikationskriterien an Unternehmen für grabenlose Neulegung und Rehabilitation von nicht in Betrieb befindlichen Rohrleitungen, Sept. 2001

[Qualification criteria to be met by companies for the trenchless relaying and rehabilitation of out-of-service pipelines, Sept 2001]

[�.8] DVGW Arbeitsblatt GW 329: Fachaufsicht und Fachpersonal für steuerbare horizontale Spülbohrverfahren; Lehr- und Prüfplan, Mai 2003

[Specialist supervisors and specialist personnel for steerable horizontal direction drilling methods; plan for instruction and testing, May 2003]

[�.9] DIN EN 1��2: Rohre, Formstücke und Zubehör aus duktilem Gusseisen – Zementmörtelumhüllung von Rohren – Anforderungen und Prüfverfahren, Sept. 200�

[Ductile iron pipes, fittings and accessories – External cement mortar coating for pipes – Requirements and test methods]

[�.10] DIN 30�7�-2: Äußerer Korrosionsschutz von erdverlegten Rohrleitungen; Schutzmaßnahmen und Einsatzbereiche bei Rohrleitungen aus duktilem Gusseisen., April 1993

[External corrosion protection of buried pipes; corrosion protection systems for ductile iron pipes, April 1993]

[�.11] Renz, M.: Premiere des Spülbohrverfahrens mit duktilen Gussrohren DN �00 bei Einzelmontage in den Niederlanden

(A first for the directional drilling technique using individually assembled DN 700 ductile cast iron pipes in the Netherlands]

GUSSROHRTECHNIK �0 (200�) p. 13

[�.12] DVGW Hinweis W �01: Entscheidungshilfen für Rehabilitation von Wasserrohrnetzen

[Aids to decision-making for the rehabilitation of water-pipe systems]

Reference documents

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6.1General

For quite some time now, it has been the practice in rural areas for cables and plastic pipelines to be ploughed in from a drum provided there was no existing infrastructure or other obstacles along the path of the run. Where this is preferably done is along farm roads at the edges of areas used for agricultural purposes. The technique was successfully tried out for the first time using ductile cast iron pipes in 2000, as part of a research project, and it has now developed into a standard technique which has now been covered in the sets of rules issued by the DVGW and DWA. What is used for the installation of ductile cast iron pipes is the trailing plough procedure detailed in ATV DVWK Merkblatt M 1�0 [�.1] and DVGW Arbeitsblatt GW 32� (draft of �/0�) [�.2].


A cavity is produced by a widening body shaped like the nose of a rocket at the bottom end of a ploughshare. A pipe string, which is attached to the widening body, is pulled into this cavity in the same stage of the operation. Fig. �.1 shows the principle of the technique. So far it has been used with pipes of nominal sizes from DN 80 to DN 300. The machinery required consists of the traction vehicle (Fig. �.2) and a plough (Fig. �.3) carrying a ploughshare. To ensure that the vertical position of the path followed by the run remains constant when the profile of the terrain varies, the depth of penetration of the share can be controlled hydraulically.

6. Installingductilecastironpipesbythe rocketploughtechnique

Fig. 6.1 The rocket plough technique

The rocket plough technique

Pipe string withtraction-resistant joints

Rocket plough Traction vehicle

Winch

Launch pit

Widening body

Plough-share

Pilling rope

Support plateWarning strip

�9

A steel rope (Fig. �.�) connects the plough to the traction vehicle and the latter can be supported on the ground by means of a support plate, to enable the tractive forces to be transmitted into the ground. The string of ductile cast iron pipes, which is connected by longitudinal force-fit joints, is laid out along the line of the run. The string is then hooked onto the widening body (Fig. �.�) and is ploughed into the earth (Fig. �.7) from a launch pit with an inclined ramp (Fig. �.�). The length of the launch pit depends on the angular deflection of which the longitudinal force-fit restrained joints are capable.

Fig. 6.2 Traction vehicle Fig. 6.3 Plough on low-loader Fig. 6.4 Traction vehicle and steel rope

Fig. 6.5 Ploughshare with widening body

Fig. 6.6 Launch pit

Fig. 6.7 Ploughing-in process


70

6.3Outsideprotection

With the rocket plough technique, the outside protection of the pipes is a matter of par-ticular importance because the string of pipes which is hooked on is generally ploughed into the existing soil without any lubricants (bentonite or the like). Because there is gen-erally no exact knowledge of just what the conditions are in the subsoil, the pipes require an outside protection which is able to carry high loads and which will remain undamaged even when subjected to extreme mechanical stresses and will thus stay effective for the entire life of the pipeline.What is used for this purpose in the case of ductile cast iron pipes is a plastic-modified cement mortar coating (Fig. �.8) to DIN EN 1��2 [�.3].What is used to protect the socket joints is either polyethylene shrink-on material (Fig. �.9) to DIN 30�72 [�.�], with an additional sheet-metal cone to provide the shrink-on material with mechanical protection during the pulling-in process, or a cement mortar protecting sleeve with a sheet-metal cone for mechanical protection

Fig. 6.8 Plastic-modified cement mortar coating

Fig. 6.9 Joint protection

Fig. 6.10 Sheet-metal cone


Cement mortar coating

Zinc coating

Cement mortar lining

Ductile cast iron

71

6.4Joints

The longitudinal force-fit BLS® restrained joint (Fig. �.11) is used for the rocket plough technique. Over the size range from DN 80 to DN 2�0, this BLS® joint is supplemented by a high-pressure lock (Fig. �.12) to enable the transmission of the tractive forces to be maximised.

Fig. 6.11 BLS® joint Fig. 6.12 Joint with a high-pressure lock

6.5Permittedtractiveforcesandminimumradiusesforcurves

The permitted tractive forces and the minimum radiuses for curves are given in DVGW Arbeitsblatt GW 32� (draft of �/0�) and in ATV Merkblatt ATV-DVWK-M 1�0 (Table 1) or can be seen from Table I in section 2. With regard to the design and construction of the components of the longitudinal force-fit joints, the VRS joint which is dealt with in the DVGW Arbeitsblatt and the ATV-DVWK Merkblatt corresponds in all respects to the BLS® restrained joint.

Fig. 6.13 BLS® traction head

Outside protection, joints, tractive forces, radiuses of curves

Catch

Left lock Right lock

High-pressure lock

72

6.6Areasofapplicationandadvantagesoftheinstallationtechnique

The rocket plough technique is particularly suitable for the installation of pipelines in rural areas and in areas where ground water and surface water is subject to statutory protection. Intersections with small, shallow bodies of surface water and installation in embankments do not present any problems for this installation technique. Installation below the water ta-ble is equally possible. The terrain must not be surfaced and must not contain any obstacles of any great size in the area through which the path of the pipeline runs. The exact position of any intersecting pipes or lines must be precisely known in advance. The rocket plough technique is very suitable for use in types of soil which can be easily displaced. Displaceable soils include unconsolidated deposits of mixtures of gravel and silt, mixtures of gravel and clay, mixtures of sand and silt and mixtures of sand and clay.

Additional protective pipes, cables and warning strips can be installed at the same time as the pipeline is being pulled in (Fig. �.1�). A suspension of bentonite can be fed in to fill up the annular space or to reduce the frictional forces. Individual strings of pipes are connected together by means of collars (Figs. �.1� and �.1�).

Fig. 6.14 Pipeline, protective pipe and warning strip

Fig. 6.15 Connection between strings of pipes

Fig. 6.16 Connection made with a collar Fig. 6.17 Surface of ground after the pulling-in


73

The disturbed soil that is left on the surface after the pipeline has been pulled in (Fig. �.17) is smoothed down again with a digger.

These are some other advantages of the rocket plough technique:• low installation costs compared with conventional techniques• short installation times• no removal of top-soil required• space required for making the run is not very wide (up to about six metres)• there is no mixing of soils• depths of installation of up to two metres.

A feature which needs to be stressed is the speed of installation which can be achieved: it is generally between two and seven metres a minute.

Table �.1 shows some of the pipeline installation projects which have been carried out in recent years with the rocket plough technique.

Table �.1: Excerpt from the list of reference installations entitled „Ploughing-in of ductile cast iron pipes“

No. Location Nominal Size Length

1 Laue-Poßdorf (near Delitzsch) 200 1.2�8 m

2 Impfingen 1�0 797 m

3 Hergenstadt 1�0 2.�00 m

� Untersollbach 1�0 2.037 m

Areas of application, advantages and reference installations

7�


[�.1] DVGW Arbeitsblatt GW 32� (Entwurf �/0�) – Fräs- und Pflugverfahren für Gas- und Wasserrohrleitungen; Anforderungen, Gütesicherung und Prüfung

[Cutting and ploughing techniques for gas and water pipelines; requirements, quality assurance and testing]

[�.2] ATV-DVWK-Merkblatt M 1�0 Fräs- und Pflugverfahren für den Einbau von Abwasserleitungen und -kanälen, Oktober 2003

[Cutting and ploughing techniques for the installation of sewage pipes and conduits, October 2003]

[�.3] DIN EN 1��2: Rohre, Formstücke und Zubehör aus duktilem Gusseisen – Zementmörtelumhüllung von Rohren – Anforderungen und Prüfverfahren, Sept. 200�

[Ductile iron pipes, fittings and accessories – External cement mortar coating for pipes – Requirements and test methods]

[�.�] DIN 30�72: Organische Umhüllungen für den Korrosionsschutz von in Böden und Wässern verlegten Rohrleitungen für Dauerbetriebstemperaturen bis �0° C ohne kathodischen Korrosionsschutz – Bänder und schrumpfende Materialien, Dez. 2000

[External organic coatings for the corrosion protection of buried and immersed pipelines for continuous operating temperatures up to �0°C – Tapes and shrinkable materials, Dec. 2000]


7�

Reference documents

7�

7.1General

When pipelines are renovated by the relining technique, a new pipeline is pulled or pushed into an existing pipeline. This always results in a reduction in the hydraulic cross-section of the pipeline. When relining is carried out with ductile cast iron pipes, the reduction in the cross-section of the pipeline depends on the outside diameter of the sockets in the new pipeline. The pipeline suffers a loss of hydraulic performance. To some degree this is compensated for by the smooth interior surface of the new pipeline (the low roughness of its walls). Old pipelines are often encrusted on the inside and the roughness of their walls is therefore high. The relining technique can be used for drinking water pipelines, industrial water pipelines, pressure waste water pipelines and gravity waste water pipelines.

In Germany, the consumption of drinking water by the population and by industry is going down. A reduction in the hydraulic cross-section of a pipeline is therefore often an advantage to the operator, because the rate of flow of the water is accelerated again and the dwell time of the water in the pipeline is shorter, by which means it is often possible for health problems to be avoided.

With waste water pipelines too, the rate of flow goes up as a result of the relining, and in many cases this is a way of stopping the solids carried in the waste water from set-tling. Because of deposits of solids, waste water pipelines often have to be cleaned at relatively short intervals by high-pressure flushing or by using go-devils.

Wherever there are pipelines where the intervals between changes of direction or lateral connections are not too short, renovation by the relining technique is always more economical than renovation by relaying in open trenches. This is true above all of runs of pipes below paved or metalled surfaces (e.g. surfaces carrying traffic) or in built-up areas.

7. Renovationofsupplyanddrainagepipelineswithductile castironpipesbythereliningtechnique

The pipe relining technique

77


In the relining technique, ductile cast iron pipes to DIN EN �� [7.1] or DIN EN �98 [7.2] are pushed or pulled into the existing, old pipeline. They slide on their sockets when this is done. What is important in this case is for the old pipeline to be properly prepared. When work of this kind was done in the past, it was found that a coefficient of friction of µ < 1.0 can always be achieved if the old pipe is properly prepared – if en-crustation is removed (Fig. 7.1), if gaps in the floor of the pipe at the sockets are closed off, if lubricant is applied to the floor of the pipe, and so on.Generally speaking, the annular space left between the old pipe and the new pipe is filled with an alkaline insulating material. If this is done, ductile iron pipes with zinc coating and cover coating are sufficient (Fig. 7.2). If not, ductile iron pipes with cement mortar coating have to be used.

Fig. 7.1 High-pressure cleaning of the old pipeline

Fig. 7.2 Insulation of the annular space

7.2.1Pulling-in

For pulling-in, the positive locking longi-tudinal force-fit BLS® restrained joint (Fig. 7.3) needs to be used.

Fig. 7.3 Cut-away views of the DN 80 to DN 500 and DN 600 to DN 1000 BLS® restrained joints

A description of the technique, pulling-in

78

The maximum tractive forces which are permitted in this case are taken from the type tests to DIN EN �� for movable longitudinal force-fit restrained joints. From the al-lowable component operating pressures PFA and PMA which were determined in these tests, the permitted tractive force is calculated using the formula Ptype = 1,� x PFA + � bar, decreased by a safety factor of S = 1.1.

The worst-case incidental conditions were taken as a basis for the type testings. These were for example:• joint with largest annular space that is possible and subject to load at the crown• joint with largest annular space that is possible and at maximum angular deflection• 2�,000 cycles of internal pressure varying cyclically between PMA and (PMA-�)

The permitted tractive forces which were determined in this way are specified in DVGW Arbeitsblatt GW 321 [7.3], DVGW Arbeitsblatt GW 322 [7.�] and DVGW Merkblatt GW 323 [7.�].

The permitted tractive forces and the maximum possible angular deflections for the BLS® restrained joint, and also the minimum radius which is possible for curves, can be found in Table 2.2 in section 2. Higher figures, both for operating pressure and for tractive force, are possible by, for example, increasing the wall thickness class. If the angular deflections at the sockets are ≤ 0.5°, then the figures given can be increased by a further 50 kN.It has proved successful for the new string of pipes to be pulled in with traction rods and a report on this appears in [7.�]. Pulling-in with a winch and steel rope is not recom-mended nor is the use of friction-locking longitudinal force-fit joints. A traction head is always required for pulling in the new string of pipes. This is produced from a BLS® restrained joint (Fig. 7.�).

Fig. 7.4 Representation of pipe plus traction linkage

Fig. 7.5 BLS® traction head


79

Buderus Giesserei Wetzlar GmbH is able to make traction heads available to the companies doing the work on hire against a hire charge. At least two pits are always required for renovation by the relining technique. The size of the pits depends on the traction equipment that is used. The pipes are six metres in length and because of this the assembly pit should be at least eight metres long. The width of the assem-bly pit depends in the nominal size of pipe which is going to be installed (Fig. 7.�).

7.2.2Pushing-in

Fig. 7.6 View of an assembly pit

For pushing-in, ductile cast iron pipes having TYTON® restrained joints which are not of the longitudinal force-fit type are pushed into the old pipeline. When this is done, the axial thrust is transmitted to the end-wall of the TYTON® socket from the end-face of the inserting end. Because the inserting ends of the pipes are bevelled, it is not the entire cross-section of the pipe-wall that is available to transmit the axial thrust (Fig. 7.7). Also, allowance must be made under DIN EN �� for the smallest outside diameter that is possible for the pipes.

The compressive strength of ductile cast iron is σD = ��0 N/mm².Leaving aside any safety factor, a pressing force of P = σD x Awall is thus possible, where Awall is the cross-sectional area of the wall of the cast iron which transmits the force.

Fig. 7.7 Transmission of force in pushing-in


P = σD x AWall

80

However, the figures obtained by adopting this theoretical approach cannot under any circumstances be taken as permitted pushing-in forces. In view of the incidental con-ditions which may apply in the given case, such as possible angular deflections of the joints, the roughness of the wall of the pipe which is to be renovated, the annular gap which is left, and so on, it may be necessary to allow a considerable safety factor.

Table 7.1 Calculation of theoretical pushing-in forces

DN d1[mm]

Wall thick-ness class

smin[mm]

Perm.σ =[N/mm2]

Fperm[kN]

80 98 K 10 �.7 ��0 2��

100 118 K 10 �.7 ��0 32�

12� 1�� K 9 �.7 ��0 �00

1�0 170 K 9 �.7 ��0 �77

200 222 K 9 �.8 ��0 ��

2�0 27� K 9 �.2 ��0 1010

300 32� K 9 �.� ��0 1�2�

3�0 378 K 9 � ��0 1913

�00 �29 K 9 �.� ��0 2��

�00 �32 K 9 7.2 ��0 3787

�00 �3� K 9 8 ��0 21��

700 738 K 9 8.8 ��0 3�99

800 8�2 K 9 9.� ��0 �1�1

900 9�� K 9 10.� ��0 70�0

1000 10�8 K 9 11.2 ��0 92�2

The pushing-in forces which are shown do not include a safety factor. This must be suited to the local conditions and must be agreed with the Applications Engineering Division of Buderus Giesserei Wetzlar GmbH.

Example: DN 900, wall thickness K 9, Awall = 12.83� mm² Pressing force with no safety factor allowed forP = σD • Awall = ��0 N/mm² x 12.83� mm² = 70�0 kNWith an assumed length for the pipe string of 200 m, DN 900 and wall thickness K 9, the weight of the pipe string would be ��,000 kg (�� t). With a coefficient of friction µ = 1.0 a pressing force of ��0 kN would be required. The theoretical maximum permitted pressing force Fperm on the other hand is 70�0 kN (see Table 7.1).

Reports on relining work carried out using this technique appear in [7.7] and [7.8].At the present time, no permitted pushing-in forces for ductile cast iron pipes are laid down in the existing sets of rules. The appropriate DVGW-Arbeitsblatt GW 320-1 cur-rently exists as a draft. If there is an application, we always recommend consulting our Applications Engineering Division so that the pressing force which is permissible in the given case can be determined. When pipes are being pushed in, it is always the inserting end which leads and which is pushed into the socket of the pipe that was pushed in previ-ously. The inserting end of the first pipe which is pushed in has to be fitted with a centring head. This can be made available on hire by Buderus Giesserei Wetzlar GmbH.As with pulling-in, at least two pits are required. The size of the pushing and as-sembly pit depends on the length of the pipes (which is usually six metres), on the pushing equipment used and on the nomi-nal size of the pipes that are going to be in-stalled. The size of the arrival pit depends on the nominal size and any other fitments which there may be.


81

Fig. 7.8 Pushing in a pipe

Reports on relining work carried out using this technique appear in [7.7] and [7.8].At the present time, no permitted pushing-in forces for ductile cast iron pipes are laid down in the existing sets of rules. The appropriate DVGW-Arbeitsblatt GW 320-1 cur-rently exists as a draft. If there is an application, we always recommend consulting our Applications Engineering Division so that the pressing force which is permissible in the given case can be determined. When pipes are being pushed in, it is always the inserting end which leads and which is pushed into the socket of the pipe that was pushed in previ-ously. The inserting end of the first pipe which is pushed in has to be fitted with a centring head. This can be made available on hire by Buderus Giesserei Wetzlar GmbH.As with pulling-in, at least two pits are required. The size of the pushing and as-sembly pit depends on the length of the pipes (which is usually six metres), on the pushing equipment used and on the nomi-nal size of the pipes that are going to be in-stalled. The size of the arrival pit depends on the nominal size and any other fitments which there may be. Fig. 7.9 Centering head with skids for sliding


82


If the annular space left between the old pipe and the new one is filled with an al-kaline insulating material, all that the pipes require is the outside protection consist-ing of a zinc coating with a cover coating.The sockets do not require any mechani-cal protection for pulling-in or pushing-in.If the annular space which is left is not filled, we recommend the use of pipes with a cement mortar coating (ZMU) to DIN 1� ��2 [7.9]. The restrained joints are protected by cement mortar protect-ing sleeves of rubber or shrink-on poly-ethylene material to DIN 30 �72 [7.10]. The restrained joints are also given additional mechanical protection when being pulled in or pushed in (Fig. 7.10).

7.4Advantagesofductilecastironpipes

Ductile cast iron pipes are capable of carrying high loads. This ensures that all the forces which act on the pipeline both from inside and outside can be withstood without any problems just as they would be by a new pipeline that was laid in an open trench. The conditions, behaviour and steadiness of the old pipeline do not affect this. This is not something that is always ensured with plastic pipes.

The economic advantage comes from the TYTON® restrained joint, which is quick and safe to assemble. Depending on the nature of the pipe and its nominal size, with steel pipes the joints have to be welded in most cases, as they also do with plastic pipes. This is usually very time-consuming. While the welding is being done, the rest of the site per-sonnel have to take a break and all the machines and other equipment are standing idle.

Another point that Buderus ductile cast iron pipes have in their favour is their long technical operating life.

Fig. 7.10 Ductile cast iron pipe with ZMU, shrink-on sleeve and sheet-metal cone


83

7.5Referenceinstallations

No. Location Year Old pipe New pipe Length Procedure

1Berlin,

Togostraße2003

DN 1000 asbestos cement

DN 800ductile cast

iron1�0 Pulling-in

2Berlin, B 101State border

200�

Doppellei-tung- 2x DN 1000, grey cast iron &

steel

2x DN 800 ductile cast

iron2x 1100 Pushing-in

3Berlin,

Berliner Allee200�

DN 1000 steel

DN 800ductile cast

iron300 Pushing-in

�LeipzigMölkau

200�DN 1100

grey cast iron

DN 900ductile cast

iron372 Pushing-in

�

Leipzig,long-distance

pipeline Thallwitz

200�DN 1100

grey cast iron

DN 900ductile cast

iron3�� Pushing-in

�FWV Elbaue-

Ostharz Güsten200�

DN 1000 StB steel

DN 800 ductile cast

iron7�2 Pulling-in

Outside protection, Advantages, Reference installations

8�


[7.1] DIN EN �� Rohre, Formstücke, Zubehörteile aus duktilem Gusseisen und ihre Verbindungen für Wasserleitungen – Anforderungen und Prüfverfahren [Ductile iron pipes, fittings, accessories and their joints for water pipelines – Requirements and test methods]

[7.2] DIN EN �98 Rohre, Formstücke, Zubehörteile aus duktilem Gusseisen und ihre Verbindungen für die Abwasser-Entsorgung Anforderungen und Prüfverfahren [Ductile iron pipes, fittings, accessories and their joints for sewerage applications – Requirements and test methods]

[7.3] DVGW-Arbeitsblatt GW 321 Steuerbare horizontale Spülbohrverfahren für Gas- und Wasserrohrleitungen – Anforderungen, Gütesicherung und Prüfung [Steerable horizontal directional drilling methods for gas and water pipelines – Requirements, quality assurance and testing]

[7.�] DVGW-Arbeitsblatt GW 322-1 Grabenlose Auswechselung von Gas- und Wasserleitungen – Teil 1: Press/Ziehverfahren – Anforderungen, Gütesicherung und Prüfung [Trenchless replacement of gas and water pipelines - Part 1: Press-pull method – Requirements, quality assurance and testing]

[7.�] DVGW-Merkblatt GW 323 Grabenlose Erneuerung von Gas- und Wasserversorgungsleitungen durch Berstlining; Anforderungen, Gütesicherung und Prüfung [Trenchless renovation of gas and water supply pipelines by the burst lining method; requirements, quality assurance and testing]


8�

[7.�] Rink, W.: Langrohrrelining mit duktilen Gussrohren DN 800 [Pipe relining with DN 800 ductile cast iron pipes] GUSSROHRTECHNIK 38 (200�), p. 17

[7.7] Schnitzer, G.; Simon, H. und Rink, W.: Langrohrrelining DN 900 in Leipzig – Mölkau [DN 800 pipe relining in Leipzig – Mölkau] GUSSROHRTECHNIK 39 (200�), p. 20

[7.8] Bauer, A.; Simon, H. und Rink, W.: Sanierung der Thallwitzer-Fernleitung DN 1100 mit Langrohrrelining DN 900 [Renovation of the Thallwitz DN 1100 long-distance pipeline by DN 900 pipe relining] GUSSROHRTECHNIK �0 (200�), p. 28

[7.9] prEN 1��2: Rohre, Formstücke und Zubehör aus duktilem Gusseisen – Zementmörtelumhüllung von Rohren – Anforderungen und Prüfverfahren, Sept. 200� [Ductile iron pipes, fittings and accessories – External cement mortar coating for pipes – Requirements and test methods, Sept. 200�]

[7.10] DIN 30�72: Organische Umhüllungen für den Korrosionsschutz von in Böden und Wässern verlegten Rohrleitungen für Dauerbetriebstemperaturen bis �0° C ohne kathodischen Korrosionsschutz – Bänder und schrumpfende Materialien, Dez. 2000 [External organic coatings for the corrosion protection of buried and immersed pipelines for continuous operating temperatures up to �0°C – Tapes and shrinkable materials, Dec. 2000]

[7.11] DVGW- Arbeitsblatt GW 320-1 (Entwurf) Erneuerung von Gas- und Wasserrohrleitungen durch Rohreinzug mit Ringraum

[Renovation of gas and water pipelines by pulling-in with annular space]

Reference documents

8�

An interesting variant technique for the trenchless installation of new ductile cast iron pipelines was seen for the first time in 200� at the Berlin Water Exhibition [8.1]: a steered pilot bore was run to the arrival pit over a distance of approximately 70 metres using a tunnelling machine for microtunneling. As a second step, this pilot bore was upsized to a diameter of �80 millimetres by soil removal through auxiliary pipes containing an auger feeder. The third step was to withdraw the auxiliary pipes while at the same time pulling in individual ductile cast iron pipes. The accuracy which can be achieved with this variant technique is so great that even the stringent requirements of draft DWA Arbeitsblatt A 12� [8.2] for gravity pipes can be met.


The first step is to make the pilot bore. Starting from the launch pit, the pilot pipe is pressed through the displaceable soil to the arrival pit. An optical system, a steering head, a theodolite fitted with a CCD camera and a display are used to enable the target point to be homed in on exactly while direction and inclination are constantly monitored (Fig. 8.1).

8. Installationwithsteeredpilotbore

Fig 8.1 Step 1: Pilot bore

The steered pilot bore technique

8.1General

1. Pilot bore

Launch pit

BohrtecBM �00

Surface of ground

Drive of pilot bore

Arrival pit

87

In the second step, the pilot is upsized by pressing in protective steel casing pipes with an outside diameter of �20 millime-tres (Fig. 8.2). Together with the steel cas-ing pipes, the lengths of pipe in the pilot bore are pushed to the arrival pit, discon-nected there and recovered. The soil that is dug out as the bore is upsized is fed back to the launch pit by a feed auger which is in one metre long sections. In the launch pit the soil is collected in a bin, raised to the surface with the site hoist and collected in containers to be taken away (Fig. 8.3)

Fig. 8.2 Lowering the casing pipe

Fig. 8.3 Step 2: Pressing in the casing pipe


2. Pressing in the casing pipe

Launch pit

BohrtecBM �00

Surface of ground

�20 mm dia. casing pipeplus hoses for betonite

Arrival pit

Excavated soil Feed auger

88

In the third step of the operation, the first DN 300 ductile cast iron pipe for medium with BLS® joints is lowered into the arrival pit (Fig. 8.�) and coupled to the traction head on the front casing pipe. The casing pipes, which are connected by longitudinal force-fit joints, are now pulled back to the launch pit; there they are recovered together with the feed auger. It takes next to no time for all the other pipes for medium to be coupled onto the pipe that has already been pulled in (Figs. 8.� and 8.�). The traction head carries equipment for measuring the tractive force; this is used to measure the pulling-in forces acting on the string of pipes and, later on, to document them in a print-out.

Fig. 8.4 Step 3: Pulling-in of the pipes for medium

Fig. 8.5 Lowering a pipe into the arrival pit

Fig. 8.6 Coupling on a fresh pipe


2. Pressing in the casing pipe

Launch pit

BohrtecBM �00

Surface of ground

�20 mm dia. casing pipe

Arrival pit

The casing pipes and pipes for medium must be fitted with longitudinal force-fit joints

DN 300 ductile cast iron pipes

Traction head & equipment for measuring tractive force

89

Outside protection, joints, other points

Fig. 8.7 BLS® collar

Fig. 8.8 BLS® flanged socket


With this technique, the outside protection of the ductile cast iron pipes consists of plastic-modified cement mortar (ZMU) to DIN EN 1� ��2. The joint area has to be protected with a shrink-on sleeve. Shrink-on sleeves of tape material should not be used in this case.

8.4Joints

Because the pipe for medium is pulled in by steered pilot boring, BLS® joint also has to be used in this case. The permitted tractive forces and operating pressures for the BLS® joint are shown in Table 2.1 in section 2. However, due to the oversize, the tractive forces which can be expected will not be excessively high.

8.5Otherpoints

The individual sections of the pipeline can be connected together in the convention-al way in the assembly pits (which were previously the arrival and pull-in pits) us-ing standard fittings. For pipelines con-nected entirely by longitudinal force-fit joints, BLS® collars conforming to a fac-tory standard are available (Fig. 8.7). For pressure tests, the sections are sealed off with thrust-locked fittings from the BLS® range (Fig. 8.8, 8.9 and 8.10). There is thus no need for the end pieces to be supported on the pit lining. At �20 mil-limetres, the outside diameter of the cas-ing pipe is so adjusted that there is a small oversize for the �20 millimetre sockets of the cast iron pipes. The outside diameter of the main body of the cast iron pipes, including the cement mortar coating, is approx. 33� millimetres.

90


The approximately �0 mm wide annular gap which this leaves fills up on its own if the soil is of a suitable type. So far, there have not been adverse effects on the ground surface due to settling.

The technique is fully developed in tech-nical terms. It combines the well known steered pilot boring technique which has proved its worth in the field of sewage pipe installation with the technique of pull-ing in ductile cast iron pipes with longitudi-nal force-fit restrained joints. There is only a small amount of interference with traf-fic and the environment. This technique is proving to be very economical and the reasons for this are the short installation times, the saving on below-ground work, such for example as the lining of pipe trenches, the temporary storage of soil, and transport to and from the site, the kindliness to any adjacent infrastructure, and the low-emission nature of the instal-lation work.

Fig. 8.9 BLS® flanged spigot

Fig. 8.10 BLS® plug

91


[8.1] Richter, D. und Rau, L.: Grabenloser Einbau von DruckrohrenDN 300 im Einzug nach gesteuerter Pilotbohrung [Trenchless installation of DN 300 pressure pipes by pulling-in after a steeredpilot bore]GUSSROHRTECHNIK �0 (200�), p. �2

[8.2] DWA Arbeitsblatt – A 12� Rohrvortrieb, 09/9� [Pipe driving, 09.9�]

Reference documents

92

The view generally held today is that a technique for installing pipes can be considered economical when the pipeline to be installed with it can be tendered for and installed at the lowest price. If this is the view that is adopted, then it will be only very rarely that the costs of operating and maintaining the pipeline are considered, let alone the costs of replacing it at the end of its normal operating life.

§ 21, no. 2 of Part A of the German Regulations relating to the Placing of Contracts for Construction Services (the VOB/A) demands that tenders be checked from an economic point of view. Even today, there are specialist commentaries that put an interpretation on this demand, as follows:

There is a close connection between the checking of tenders from an economic point of view and their consideration from a technical point of view.Whether a price is reasonable is determined by the best ratio between price and per-formance, including operating life, operating and maintenance costs, and any other costs which may arise at times close to or remote from the present.

In § 2�, no. 3, paras. 2 and 3 of the VOB/A it is even stated that:„ … in assessing reasonableness, the economy of the method of construction, the technical solutions adopted or other favourable conditions of execution must be taken into account.“„ … the contract is to be awarded to the tender which appears most economical in the light of all the relevant considerations, such for example as price, deadline for completion, operating and consequential costs, design, profitability or technical merit. The lowest tendered price alone is not the deciding factor.“ [9.1]

Costs which have not generally been considered in the past are those which are caused by the work of installing or laying pipelines, in its surroundings, and which the general public have to acquiesce in paying, without any prospect of reimbursement, in the form of interference with traffic, noise nuisance and environmental pollution. This being so, it is almost impossible for any fair financial comparison to be made between the trench-less and open-trench techniques because the „social“ costs paid by the general public, though it may be perfectly possible to put a figure on them, are not taken into account when contracts are being placed. However, if the external incidental conditions make it difficult from the constructional point of view for a pipeline to be installed by the

9. Aconsiderationoftheeconomicsoftrenchlesstechniques

A consideration of the economics of trenchless techniques

93

open-trench technique, then to an increasing degree there are better prospects for the trenchless techniques. The wide range of variant techniques which have today been developed to a high level of technical sophistication make it possible for a suitable and economical technique to be selected for every project. The operator‘s requirement for a network of drinking water pipes to be safe is reflected in DVGW Hinweis W �09 „Effects of the construction procedure and method on the economy of the operation and maintenance (on the network operating costs) of water distribution systems“ [9.2]. From the operating point of view, there are advantages in laying pipelines in open trenches; extensive and well-founded experience is available:

Existing pipelines are visible and preset minimum spacings can be closely maintained.

The pipeline can be installed, pressure-tested and measured out by „visual inspection“.

Any adverse effects on the new pipe (e.g. from stones) can be almost ruled out.

All the joints between pipes can be checked before the trenches are backfilled.

Hydrants or connecting pipes can be installed at any later date.

If pipes are damaged then, in the present state of the art, there are no restrictions on the locating of leaks.

Planned requirements relating to high and low points and to lateral spacings can readily be satisfied by the construction work.

Any damage to facilities belonging to third parties can be very largely ruled out.

For trenchless techniques on the other hand, W �09 makes the proviso that, due to the fact that the renovated or rehabilitated pipeline will not be fully visible, there will have to be increased expenditure on monitoring of the installation work and on quality con-trol. Nevertheless, experience is gradually showing that, generally speaking, trenchless installation and renovation techniques may be more economical than the conventional open-trench techniques if the regional competition for pipeline projects which are put out to tender is focussed on these techniques. Thus, one regional gas and water supply company has for example published a comparison between open-trench and trenchless construction as shown in Table 9.1.


9�

Conventional construction Trenchless construction

Length of pipeline 100% 100%

Digging up of surface 100% 1�%

Construction time 100% 30%

Cost 100% �0 - 70%

Operating life 100% 70 - 100%

Kindliness to resources 20% 80%

Noise, environment, adverse effects

100% Intangible gain

Table 9.1 Overall comparison of open-trench construction with trenchless construction [9.1]

A rough comparison of the costs of trenchless renovation techniques with those of the open-trench method likewise shows clear potential savings for the trenchless techniques (Table 9.2)

Open-trench construction Trenchless construction

BurstingRocket

ploughingPress-pulltechnique

Relining

100% 70% 70% 80%With

annular gapWithout

annular gapHoses

�0% 70% �0%

Table 9.2: Rough comparison of the costs of the construction techniques [9.1]

Quite a large project for conduit renovation which was carried out in Friedrichshafen by the burst lining technique gave a figure of 3�% for the reduction in costs compared to the conventional technique, and thus confirmed [9.3] the details given in [9.1]. Replace-ment in the same nominal size of 800 metres of DN �00 ductile cast iron pipes by the static burst lining technique has shown a cost saving of 22% [9.�]. The point at which the trenchless techniques cease to be economical is when the density of the house connec-tions rises beyond a certain figure, because the cost of below-ground work and restora-tion of the surface then rises to a disproportionate extent [9.�].To ensure the quality of drinking water pipelines which are renovated or installed trench-lessly, the DVGW has in recent years worked out comprehensive technical rules in the


9�

form of the series of documents numbered GW 321 et seq. which ensure exactly that. The parameters of current trenchless installation and renovation techniques which are relevant to quality are described and laid down, together with limit values and directions for measuring them.DVGW Hinweis W �09 stresses the paramount influence which the pipe system selected has on the choice of the installation or renovation technique. The principal considera-tions affecting the choice of the pipe system are stated to be the following:1. Bedding conditions and conditions of use (e.g. diffusion characteristics, reserves of

performance)2. Functionality of the corrosion protection systems and the connecting technology3. Whether experience has been good with the given system�. Reasonable availability (delivery times, stocks held, continuity of systems).

In what follows, the system consisting of ductile cast iron pipes with BLS joints and ce-ment mortar coatings will be looked at more closely to see how well these four principal requirements are met.

Requirement1:Experience shows that ductile cast iron pipes are the pipes least sensitive to faults in the bedding. The disadvantage which trenchless techniques have that the bedding for the pipes cannot be checked is of least significance with pipes of this type, a fact which is proved not least by the excellent results shown by the DVGW‘s damage statistics for the water industry [9.�]. The non-diffusiveness of ductile cast iron pipes makes them preferable to plastic pipes in contaminated soils [9.7]. Because of their high energy of deformation, ductile cast iron pipes have the greatest reserves of performance, both in respect of static and dynamic loads from the internal pressure or the covering earth and in respect of the permitted tractive forces (see section 2).

Requirement2:Given that the bedding and supporting conditions are unknown and uncheckable with trenchless installation techniques, it is ductile cast iron pipes with, usually, a cement mortar coating to DIN EN 1��2 that are used for these techniques. An at least five millimetre thick layer of plastic-modified cement mortar is applied in this case to a zinc covering of a weight of 200 g/m2. This coating is able to withstand extreme mechanical loads and is resistant to scoring by pointed fragments with the burst lining technique or by stones with the directional drilling technique. In the unlikely event of damage being done to this coating, the zinc covering is still available to provide active protection and its effect operates for a distance of up to 20 millimetres.


9�

The advantage of ductile cast iron pipes whose effect is most far-reaching is the connect-ing technology using the longitudinal force-fit BLS® restrained joint. This is due in the first place to the tractive force permitted for the material of the pipes, which is the highest for any of the materials used in the water supply industry (section 2, Fig. 2.19). When part-strings are required, this has a beneficial effect on their lengths. In the second place however, the most important prerequisite for economy is the short assembly time for the BLS® joint. The fact that single pipes can be assembled means that short installation pits and point sites are possible and that the speed of installation is determined by the time taken to change over the drilling and traction linkages at the machine end. The full permitted tractive forces can be applied the moment the short process of assembling the joint has been completed; there is no cooling time and no need for temperature-related reductions. These facts are the key to economic success when using ductile cast iron pipes for trenchless installation and renovation techniques.

Requirement3:Cast iron is the oldest material used for industrially manufactured water pipes. Approxi-mately half of the existing water supply network consists of pipes made of materials falling within this group. The resistance of ductile cast iron pipes and their long life is the basis for the excellent experience that has been had with them in practice, experience which has once again been corroborated in very recent times [9.7 and 9.8]

Requirement4:Buderus Giesserei Wetzlar GmbH is an important manufacturer in the German cast iron pipe industry and it is precisely in very recent times that, with its technical developments for trenchless installation techniques, it has shown itself to be a pioneer, though with-out of course losing sight of the ties it has with the traditional techniques. For Buderus Giesserei Wetzlar GmbH reliable supply and continuity of its systems have always been the supreme commands in a customer-oriented business strategy which will continue to contribute to the success of the group in the future.


[9.1] Steinhauser, P.: Wirtschaftlichkeitsbetrachtungen, Betrachtungen bei der grabenlosen Erneuerung. [Economic considerations, considerations relating to trenchless renovation]. Script of a talk given at the NO DIG Seminar on trenchless renovation of old, damaged pipes. Hanover Technical Academy, 18.01.2007

A consideration of the economics of trenchless techniques, Reference documents

97

[9.2] DVGW-Hinweis W �09: Auswirkungen von Bauverfahren und Bauweise auf die Wirtschaftlichkeit von Betrieb und Instandhaltung (operative Netzkosten) der Wasserverteilungsanlagen, Jan. 2007

[Effects of the construction procedure and method on the economy of the operation and maintenance (on the network operating costs) of water distribution systems, Jan. 2007]

[9.3] Sommer, J.: NODIG-WALKING-Friedrichshafen Markus Mendek von der Stadtentwässerung Friedrichshafen erhält Goldenen Kanaldeckel 200� für Erneuerung im Berstlining-Verfahren [Markus Mendek of Friedrichshafen Civic Drains and Sewers Utility awarded the 200� Golden Manhole Cover for renovation by the burst lining method]

[9.�] Levacher, R.: Erneuerung einer Verbindungsleitung DN �00 zwischen zwei Wasserwerken im Berstlining- und Spülbohrverfahren

[Renovations of a DN �00 connecting pipe between two waterworks by the burst lining and directional drilling methods]

GUSSROHRTECHNIK �0 (200�), p. 17

[9.�] Emmerich Peter, Schmidt Rainer: Erneuerung einer Ortsnetzleitung im Berstlining-Verfahren

[Renovation of a pipeline in a local system by the burst lining method] GUSSROHRTECHNIK 39 (200�), p. 1�

[9.�] DVGW Wasser-Information Nr. ��: DVGW-Schadenstatistik Wasser Auswertungen für die Erhebungsjahre 1997-1999 [DVGW Water Information Release No. ��: DVGW Water Industry Damage Statistics – Assessments for the years surveyed 1997-1999]

[9.7] Hannemann, B. und Rau, L.: Duktile Gussrohre aktuell wie eh und je [Ductile cast iron pipes just as up-to-date as ever] GUSSROHRTECHNIK �1 (2007), p. ��

[9.8] Barthel, P.: Moderne Wasserversorgung – natürlich mit Gussrohren! [Modern-day water supply – with cast iron pipes of course!] GUSSROHRTECHNIK �1 (2007), p. �2

Reference documents

98

10.Technicaldatasheets

SocketpressurepipeswithBLS®restrainedjointstoDINEN545/598Inside: cementmortarlining(CML)Outside:cementmortarcoating(ZMU)

Technical data sheets

DN Dimensions [mm] [bar] Weight [kg] ≈

Ø d1 CML s

PFA 1) ZMUper � m pipe

One pipe2)

Body length �m

803) 98 � 110 19.� 92.2

1003) 118 � 100 2� 113.�

12� 1�� 100 28 139.7

1�0 170 � 7� 33 1��.1

200 222 � �3 �3 228.�

2�0 27� � �� 2 30�.2

300 32� � �0 �3 38�.1

�00 �29 � 30 82 �89.�

�00 �23 � 30 101 807.�

�00 �3� � 32 121 1037

700 738 � 2� 1�0 13��

800 8�2 � 1�/2�3) 1�0 1��

900 9�� 1�/2�3) 179 200�

1000 10�8 � 10/2�3) 199 2382

1) PFA: Allowable component operating pressure in bars, DN 80 - DN 250 inc. high-pres-sure lock; higher pressures available in request2) Inc. cement mortar lining and thrust locking chamber, wall thickness class K93) Wall thickness class K10

Body length = � m

99


BLS®restrainedjointDN80toDN500

DN

Dimensions [mm]

PFA 2)*Possible

angular de-flection 3)

Number of locks Lock

set[kg]

Ø d1 Ø D1) t

80** 98 1�� 127 110 �° 3 0.70

100** 118 182 13� 100 �° 3 0.83

12� 1�� 20� 1�3 100 �° 3 1.13

1�0 170 239 1�0 7� �° 3 1.3�

200 222 293 1�0 �3 �° 3 1.9�

2�0 27� 3�7 1�� ° 3 2.70

300 32� �10 170 �0 �° � 2.70

�00 �29 �21 190 30 3° � �.�0

�00 �23 �3� 200 30 3° � �.�0

1) Guideline value2) PFA: Allowable component operating pressure in bars, up to DN 250 includes high-pressure lock3) When of the nominal dimensions*) Basis for calculation is wall thickness class K9; higher pressures available on request**) Wall thickness class K10

Retaining chamber

Welding beadTYTON® gasket

Socket

Catch

Left lock

Right lock

100

BLS®restrainedjointDN600toDN1000


DN

Dimensions [mm]

PFA 2)Possible angular

deflection

Number of locks

Clamping ringsØ d1 Ø D1) t

�00 �3� 732 17� 32 2° 9 9

700 738 8�9 197 2� 1.�° 10 11

800 8�2 9�0 209 1�/2�3) 1.�° 10 1�

900 9�� 1073 221 1�/2�3) 1.�° 13 13

1000 10�8 1188 233 10/2�3) 1.�° 1� 1�

1) Guideline value2) PFA: Allowable component operating pressure in bars, up to DN 250 includes high-pres-sure lock3) Wall thickness class K10Note: The locking segments must be fixed in place with a clamping strap! See installation instructions

Retaining chamberWelding bead

TYTON® gasket

SocketLocking

segment

101


102

11.Installationinstructions

11.1General

Applicability

These installation instructions apply to DN 80 - DN �00 ductile cast iron pipes and fit-tings with longitudinal force-fit BLS® restrained joints.Where appropriate the installation instructions for pipes with cement mortar coatings (ZMU) should be followed.For very high internal pressures (e.g. in snow making facilities) and for trenchless instal-lation techniques (e.g. the press-pull, rocket plough or horizontal directional drilling techniques) an additional high-pressure lock has to be used (see section headed „High-pressure lock“).In the case of buried pipelines, the number of joints to be locked has to be decided in accordance with DVGW Arbeitsblatt GW 3�8.The permitted tractive forces for trenchless installation techniques are laid down in DVGW Arbeitsblätter GW 321, 322-1, 323 and 32� (draft), or see section 2, page 20.

Bundling, transport and storage

Pipes of up to DN 3�0 size are supplied bundled

DN 80 100 12� 1�0 200 2�0 300 3�0

Pipes per bundle

1� 1� 10 � � � � �

To stop the pipes from being damaged or fouled, wooden supporting timbers and spacing blocks should be used both when the pipes are being stored temporarily and when they are being laid out along the run.The steel straps holding the bundles of pipes together must only be removed with tin-snips or side cutters. Chisels, crowbars and certainly pickaxes will damage the outside protection that the pipes have.

Installation instructions

103

General

Pipes must not be:• dropped or put down with a jolt,• thrown off the vehicle,• rubbed against surfaces or rolled for long distances.Slinging straps should be used for loading and unloading pipes. If single pipes are un-loaded with crane hooks, this must be done with long padded hooks which are hooked in at the ends of the pipes, as otherwise the local pressure on the layer of cement mor-tar will be too high. Particularly with large sizes of pipe, a shoe matched to the shape of the pipe must be fitted under the crane hook to protect the cement mortar lining from damage.If ductile cast iron pipes are stored in a stack, they should be put down on lengths of timber at least 10 centimetres wide spaced about 1.� metres away from the ends of the pipes. Damage to the inside or outside protection should at once be carefully repaired

DN Layers

80 - 1�0 1�

200 - 300 10

3�0 - �00 �

700 - 1000 2

Maximum permitted stacked heights

For reasons of accident prevention, stacked heights of more than 3 metres should be avoided.

10�


Pipe closures

Pipes to DN EN �� with cement mortar linings are supplied fitted with pipe closures which are intended to stop the interiors of the pipes from becoming fouled. The closures should not be removed until immediately before the pipes are going to be connected. Treatment of gaskets on the site

To ensure that the pipeline will be reliable in operation, only the gaskets meeting the relevant quality requirements which are supplied by the manufacturer of the cast iron pipes must be fitted.The gaskets must be stored in an undeformed state in cool and dry conditions. They should be protected from direct sunlight. Care must be taken to see that they are not damaged or fouled.There is a certain increase in the hardness of the gaskets at temperatures of less than 0°C. Where the outside temperatures are below 0°C, the gaskets should therefore be stored at a temperature of more than 10°C to make them easier to fit.The gaskets should not be removed from the place where they are stored until immedi-ately before they are fitted.

Pipe pits and bedding of the pipes

The pipe pit should be set up in accordance with the existing technical specifications.These are, amongst others: DIN EN 80�, DIN EN 1�10, DIN 18 300, DIN �12�, DIN �0 929 part 3, DIN 30 37� part 2, DVGW Arbeitsblätter W �00-2 or GW 9, ATV DVGW Arbeitsblatt 139 and the technical bulletin for the filling of pipeline trenches. Installation

The installation of pipes and fittings should be carried out in accordance with our instal-lation instructions. If the soil in-situ is aggressive (see DIN �0 929, part 3 and DVGW Ar-beitsblatt GW 9 on this point), a satisfactory enclosing layer of sand should be applied.When installation is in highly aggressive soils, we recommend pipes with cement mortar coatings (ZMU) to DIN EN 1� ��2.Pipe coatings should be decided on in accordance with the fields of use shown in DIN 30 �7�-2.

10�

DN 80 - DN �00 BLS® joints

Filling in the pipe pit

The pipe pit in the pavement should be filled in accordance with the „Merkblatt für das Verfüllen von Leitungsgräben“ [Directions for the filling of pipeline trenches] issued by the Road and Traffic Research Society (FGSV) of Cologne and with the „Zusätzliche Technische Vertragsbedingungen und Richtlinien for Erdarbeiten im Strassenbau“ [„Ad-ditional Technical Contractual Conditions for Earthmoving Work in Roadbuilding“] (ZTV E - StB 9�).

Pressure testing

The documents that govern the execution of pressure tests on water pipelines are DIN EN 80� and DVGW Arbeitsblatt W 200-2.

Construction of the DN 80 - DN 500 joint

Cleaning

The locks and those surfaces of the seating for the gasket, the retaining groove and the locking chamber which are indicated by ar-rows should be cleaned and any build-ups of paint should be removed.A scraper, e.g. a bent screwdriver, should be used to clean the retaining groove.

Clean the inserting end.

11.2InstallationinstructionsforDN80toDN500BLS®joints

Retaining chamber Welding bead

TYTON® gasket

Socket

Leftlock

CatchRight lock

Inserting end

10�


Carefully wipe a thin layer of the lubri-cant supplied by the pipe manufacturer onto only the surfaces which are shown hatched.

Assembling the joint

Fitting the TYTON® gasket

Clean the TYTON® gasket and pull it into a heart shape

Insert the TYTON® gasket into the socket in such a way that the external claw of hard rubber engages in the retaining groove in the socket

Then press the loop in the gasket flat.

If you have difficulty pressing the loop flat, pull out a second loop on the opposite side. These two small loops can then be pressed flat without any trouble.

107


There must never be a gap between the inner edge of the hard rubber of the TYTON® gasket and the locating bead.

Apply a thin film of lubricant to the TYTON® gasket.

Right

Apply a thin film of lubricant to the insert-ing end, and particularly the bevel, and then insert it into the socket until it is rest-ing concentrically against the TYTON® gasket. The axis of the pipe or fitting which is already in place and the axis of the one which is going to be pulled in must be in a straight line with one another.

Wrong

DN 80 to DN 2�0 DN 300 to DN �00

Positions of the openings in the socket when in the pipe pit

For the locks to be inserted or the clamping strap to be screwed up, it is advisable for the positions of the openings in the socket to be as shown.In the case of fittings, the positions of the openings will be governed by the installation situation.

108


Inserting end with welding bead

The inserting end having been cleaned, particularly at the bevel, wipe a thin film of lu-bricant over it and push or pull it in until it butts against the end-wall of the socket. The pipes must not be deflected to an angle when the locks are being inserted.

1) Insert the „right“ lock (1) in the opening in the socket and move it clockwise until it will not move any further.

2) Insert the „left“ lock (2) in the opening in the socket and move it anti-clockwise until it will not move any further.

3) Press the catch (3) into the opening in the socket

On pipes of DN 300 size and above, steps 1 to 3 have to be performed twice, because 2 x 2 locks and two catches are inserted in this case.

31

2Inserting end with no welding bead(not suitable for trenchless installation!)

1.) Insert the split clamping ring. The two halves of the clamping ring are first inserted in the thrust locking chamber separately and are then loosely connected with the two bolts.

2) Mark the depth of penetration (= the depth of the socket) on the inserting end.3) Pull in the inserting end. The inserting end having been cleaned, particularly at the

bevel, wipe a thin film of lubricant over it and push or pull it in until it butts against the end-wall of the socket. The pipes must not be deflected to an an-gle when it is being pulled in. After the inserting end has been pulled in, the previously made mark which it carries should be almost in line with the end-face of the socket.

�) Pull the clamping ring as far as is possible towards the end-face of the socket and then tighten the bolts to a torque of at least 50 Nm!

A high-pressure lock should always be used for trenchless installation techniques using DN 80 to DN 2�0 size pipes (see p. 11�).

Do not remove the lifting device until the joint has been made

109


Use of clamping ring joints

When clamping ring joints are used, care must be taken to see that they are not used in socketed bends, EN-pieces and the like!For this purpose the length of pipe for mating purposes which is cut off, which has two smooth ends, is turned through 180° so that the end carrying the welding bead can be inserted in the socket of the bend. Before the short pipe that is left, which has a socket, is fitted, an uncut pipe is connected on and it is only in the socket of this latter that the inserting end without a welding bead is inserted.

Note on the use of clamping rings

Before clamping rings are used in bridge or culvert pipes, and before they are fitted on steep slopes, in protective pipes or in collector pipes, our Applications Engineering Division should be consulted. The use of clamping rings should be avoided in these cases and in trenchless installation techniques. Pipes for mating purposes which are required should be provided with welding beads (see the section headed „Retrospective applica-tion of welding beads“).

Factory-made welding bead On-site cut

Direction of laying

Clamping ring joint(no welding bead)

Uncut pipe carryinga welding bead

Clamping ring joint(no welding bead)

Lock joint(has a welding bead)

Lock joint(has a welding bead)

110


Locking

Pull or press the pipe out of the socket until the locks or the locking ring, as the case may be, are in abutment in the locking chamber, using a laying tool for example.

The joint is now locked against longitudinal forces.

Angular deflection

Once the joint has been made, pipes of the nominal dimensions shown can be deflected to the following angles:DN 80 to DN 1�0 – �°DN 200 to DN 300 – �°DN �00 and DN �00 – 3°For a pipe � metres in length, an angular deflection of 1° gives a movement off the axis of the pipe or fitting fitted previously of about 10 centimetres, i.e. a deflection of 3° = 30 centimetres.

111


Notice on assembly

It should be borne in mind that, as a function of the internal pressure and the tolerances on the joints, stretches of up to about eight millimetres per joint may occur.To allow for the amount by which the pipeline moves outwards when stretched by pres-sure, the pipes should be offset inwards at all bends by deflecting the joints inwards to their maximum permitted angular deflection. See the diagram below.

45°

Shortening pipes

Attention must be paid to the ability of pipes to be cut. Up to and including the DN 300 size, any pipe can be cut at up to a metre back from the socket. At DN �00 and above, pipes which can be cut are specially identified by a lengthwise white stripe or the letters „SR“ printed on the end-face of the socket. 1 m

Tools

The most suitable pieces of equipment for cutting ductile cast iron pipes are disc cutters and grinders with drives of various sorts such for example as compressed air, electric motors or petrol engines.The cutting discs we recommend are silicon carbide discs of the C 2� RT Spezial type. These are cutting discs for stone which have proved successful in practice for the cutting of ductile cast iron pipes.When pipes lined or coated with cement mortar are being cut, protective goggles and respiratory protection must be worn.

Position when installed

Position after stretching

112


Any ground-off material which occurs must be carefully cleaned out of the inside of the pipe.

With pipes of large nominal sizes, it may happen that the new inserting ends which exist after the shortening are slightly oval. If necessary, inserting ends of this kind must be made round again with suitable devices which are applied to the inside or outside of the pipe, such for example as hydrau-lic jacks or mounting clamps. The device should not be removed until the joint has been completed.

Machining of cut faces

Pipes which are shortened on site must be bevelled at the cut faces to match the original inserting end.The bevel must be made as shown in the diagrams below.

The bright metal face should be painted with bituminous paint (or equivalent) which is suited to the external protection on the pipe. What is suitable for this purpose is a quick-drying cover coating which meets the requirements of the German Foodstuffs Law.

For quicker drying, it is advisable for the ends of the pipe to be warmed beforehand, and the paint itself afterwards, with a gas burner.

3-4

10-12

5-6

20-22

DN 80 to DN �00 DN 700 to DN 1000

Slightly radiused Slightly radiused

Block of timber

Block of timber

113

To ensure that the welding bead is properly made and uniform, a copper clamping ring must be fastened in place on the inserting end to enable the welding bead to be ap-plied at the correct distance from the end (see table).The zone in which the weld is made must be bright metal. Contaminants or zinc coatings must be removed by filing or grinding.Once the copper clamping ring has been removed, the cut edge at the inserting end must be restored to the original form and both it and the region occupied by the weld-ing bead must be cleaned. Finally, these regions must be provided with the appropriate protective coating.


Retrospective application of welding beads

If pipes have to be shortened on site, the welding bead needed for the BLS® restrained joint has to be applied using an electrode laid down by the manufacturer. The welding work is to be carried out as directed in DVS Merkblatt 1�02.The size of the bead and its distance from the inserting end are to be as shown in the table below.Type of electrode, e.g. Castolin 7330-D

DN 80 100 12� 1�0 200 2�0 300 �00 �00

a 8�±� 91±� 9�±� 101±� 10�±� 10�±� 10�±� 11�±� 120±�

b 8±2 8±2 8±2 8±2 9±2 9±2 9±2 10±2 10±2

c � � � � �.� �.� �.� � �

ab

c

Disconnecting

Push the pipe into the socket until it is in abutment. Take out the catch through the open-ing in the socket. Move the locks and remove them through the opening in the socket. If there is a high-pressure lock, use a shallow object (e.g. a screwdriver) to push it away from the floor and to the opening in the socket and take it out.

+0,�-1

+0,�-1

+0,�-1

+0,�-1

+0.�-1

+0.�-1

+0.�-1

+0.�-1

+0.�-1

Copper clamping ring

11�


Disconnecting clamping ring joints

Push the pipe into the socket in the axial direction until it is in abutment.The bolts holding the clamping ring together having been removed, loosen the halves of the clamping ring by hitting them with a hammer. While disconnection is proceeding, make sure that the halves of the clamping ring stay loose (if necessary repeat the ham-mering process while the inserting end is being pulled out). The clamping ring can also be prevented from jamming against the inserting end when the joint is being disconnected by clamping a square metal bar between the arms of the clamping ring. Under no circum-stances must the socket or the main body of the pipe be hit with the hammer!

The high-pressure lock

For very high internal pressures (e.g. in the case of snow making facilities and pipelines for turbines) and for trenchless installation techniques (e.g. the press-pull, rocket plough or horizontal directional drilling techniques), an additional high-pressure lock has to be used.The high-pressure lock is inserted in the locking chamber through the opening in the socket and is positioned at the floor of the socket before the right and left locks are inserted. The locks can then be inserted, which means that the high-pressure lock is situated between their smooth ends. The locks are then fixed in place with the catch in the usual way.Shown in the illustration below is a fully assembled BLS® socket including a high-pressure lock. The high-pressure lock is used for nominal sizes from DN 80 to DN 2�0.

Catch

Right lockLeft lock

High-pressure lock

11�

DN �00 - DN 1000 BLS® joints

11.2InstallationinstructionsforDN600-DN1000BLS®joints

Applicability

These installation instructions apply to ductile cast iron pipes and fittings with lon-gitudinal force-fit BLS® restrained joints.Where appropriate the installation instruc-tions for pipes with cement mortar coat-ings (ZMU) should be followed.In the case of buried pipelines, the number of joints to be locked has to be decided in ac-cordance with DVGW Arbeitsblatt GW 3�8.The permitted tractive forces for trenchless installation techniques are laid down in DVGW Arbeitsblätter GW 321, 322-1, 323 and 32� (draft), or see section 2, page 20, Table 2.1.

X

Construction of the DN 600 - DN 1000 joint

Number of locking segments per joint

DN �00 700 800 900 1000

n 9 10 10 13 1�

Retaining chamberWelding bead TYTON® gasket

Socket

Inserting end

View on X

Openings in socketLocking segment

Clamping strap

11�


Cleaning

The locking segments and those surfaces of the seating for the gasket, the retaining groove and the locking chamber which are indicated by arrows should be cleaned and any build-ups of paint should be removed.

A scraper, e.g. a bent screwdriver, should be used to clean the retaining grooves.

Clean the inserting end.

Assembling the joint

Fitting the TYTON® gasket (see pp. 10�-107)The opening in the end-face of the socket should always be positioned at the crown of the pipe. Use the laying tool to push the inserting end of the pipe into the socket of the pipe which is already in place until it is in abutment.

117


Inserting the locking segments

The joint must not be deflected angularly when the locking segments are being fitted.First insert the locking segments through the opening in the socket and then distribute them around the circumference working alternately left and right. Then rotate all the segments in one direction so that the last segment can be inserted through the opening in the socket and moved to a position where the joint is securely locked.Only a small part of the humps on the last locking segment must be visible through the opening in the socket. If any segments happen to jam, they should be moved to their intended position by moving the pipe as it hangs from the sling and tapping them gently with a hammer.Under no circumstances must the socket or the main body of the pipe be hit with the hammer!

Locking

Pull all the segments back towards the outside until they butt against the bevel of the locking chamber. Then fit the clamping strap over the segments in the way shown. Then tighten the clamping strap, but only gently so that the segments can still be moved. Now line the locking segments up properly. They must lie completely flat against the body of the pipe and they must not overlap. Then tighten the clamping strap up sufficiently tight for the locking segments to bear firmly against the pipe around the whole of its circumference. It is now no longer possible for the locking segments to be moved. Apply axial traction (e.g. with a locking clamp) and pull the pipe out of the joint until the welding bead comes to rest against the segments.When the joint is in an undeflected state, the longitudinal distances from the locking segments to the end-face of the socket should all the approximately the same.

118


User information for ratchet-equipped clamping strap

Clamping:1. Thread in the clamping strap2. Pull it through by hand to the desired length (to pre-tension it)3. Tighten the clamping strap by moving the handle up and downReleasing:�. This is done by pulling on the locking pawl and at the same time moving the lever through 180° to the opposite position.�. Pull the clamping strap out by hand.

General directions for use

The ratchet-equipped clamping strap must not be adversely affected by the corners on the segments. The different types are suitable for the following temperature ranges: PES: -�0°C to 100°C / PA: -20°C to 100°C / PP: -�0°C to -80°C. The temperature ranges may vary in a chemical environment (where this applies, check with the manu-facturer or supplier).Storage: in clean, dry and well ventilated surroundings, well away from any heat source. Keep away from chemicals and flue gases. Do not expose to direct sunlight or other ultraviolet radiation. Clamping straps must not be used as lashings! Check clamping straps for damage before they are used and never use them if: the clamping strap is damaged or a connecting or clamping component is severely abraded, torn or cracked, broken as a result of scuffing, fractured/distorted or severely corroded.• Never exceed the permitted tractive forces (shown on the label)• Do not twist or knot the straps.

Retaining chamber

Inserting end

Welding beadTYTON® gasket

SocketLocking segment

Clamping strap

119


Angular deflection

Once the joint has been made, pipes of the nominal dimensions can be deflected to the following angles:DN �00 – 2,0°DN 700 – 1,�°DN 800 – 1,�°DN 900 – 1,�°DN 1000 – 1,�°For a pipe � metres in length, an angular deflection of 1° gives a movement off the axis of the pipe fitted previously of about ten centimetres, i.e. a deflection of 3° = 30 cen-timetres.

Notice on installation and laying

It should be borne in mind that, because the locking segments adjust as a function of the internal pressure, stretches of up to about eight millimetres per joint may occur.To allow for the amount by which the pipeline moves outwards when stretched by pres-sure, the pipes should be offset inwards at all bends by deflecting the joints inwards to their maximum permitted angular deflection. See the diagram below.

45°

Position when installed

Position after stretching

120


DN �00 700 800 900 1000

a 117 13� 1�� 1�0 1�0

b 8±1 8±1 8±1 8±1 8±1

c � � � � �

0-2

+0.� 0

0-2

+0.� 0

0-2

+0.� 0

+0.� 0

+0.� 0

0-2

0-2

Shortening pipes

Attention must be paid to the ability of pipes to be cut (see p. 111). Pipes which can be cut are identified by a lengthwise white stripe or the letters „SR“ printed on the end-face of the socket.If pipes have to be shortened on site, the welding bead needed for the BLS® restrained joint has to be applied using an electrode laid down by the manufacturer. The welding work is to be carried out as directed in DVS Merkblatt 1�02.The size of the bead and its distance from the inserting end are to be as shown in the table below.Type of electrode, e.g. Castolin 7330-D

Combining fittings belonging to other systems with BLS® joints

When pipes end are going to be fitted to fittings belonging to other systems, our Applications Engineering Division should be consulted.

To ensure that the welding bead is properly made and uniform, a copper clamping ring must be fastened in place on the inserting end to enable the welding bead to be applied at the correct distance from the end (see table).The zone in which the weld is made must be bright metal. Contaminants or zinc coat-ings must be removed by filing or grinding.Once the copper clamping ring has been removed, the cut edge at the inserting end must be restored to the original form and both it and the region occupied by the weld-ing bead must be cleaned. Finally, these regions must be provided with the appropriate protective coating.

ab

c

Copper clamping ring

121

BLS® joint disconnection

Disconnecting

Push the pipe into the socket in the axial direction until it is in abutment and take out the locking segments through the opening in the socket.

Laying equipment and aids

The following items of laying equipment and aids are available for assembling joints and fittings

Laying equipment:

DN Pipes Fittings

80 100 12�

LeverMMA, MMB, MMR

and flanged so-ckets: Lever

Socket-bend: laying tool (e.g. V 301)

80 100 12� 1�0 200 2�0 300 (3�0) �00

Laying tool

V 301 V 302 (ZMU)

V 301

V 302 + chain-equipped fork tool of V 301

�00 �00 700 800 900 1000

Rack assembly Rack assembly

Aids:Dusting brush, cotton waste, wire brush, spatula, scraper (e.g. bent screwdriver), paint brush, lubricant, tracer.

122


11.3Installationinstructionsforductilecastironpipeswithcementmortarcoat-ings(ZMU)

Applicability

These installation instructions apply to the installation of ductile cast iron pipes to DIN EN �� with cement mortar coatings (ZMU) to DIN 1� ��2.To make the joints, the installation instruc-tions which apply in the respective cases should be followed.What also apply are the guidelines given in DIN EN 80� and DVGW Arbeitsblatt GW �00-2 (for water pipelines) or DIN EN �10 and ATV-DVWK A 138 (for waste water pipelines).

Installation

Installation must be carried out in such a way that the ZMU is not damaged.The following options are available for protecting the restrained joints• a cement mortar protecting sleeve • shrink-on material or protective tapes (to DIN 30 �72),• a mortar bandage (e.g. as produced by Messrs. Ergelit) for special applications.

Cement mortar protecting sleeves

Cement mortar protecting sleeves can be used on TYTON® and BRS® restrained joints up to DN 700 and on BLS® restrained joints up to DN �00.Before the joint is assembled, the sleeve is rolled on and, with the larger diameter lead-ing, is pulled onto the inserting end sufficiently far for the ZMU to project by approx. 100 millimetres.Fitting can be simplified by applying lubricant to the ZMU.Once the joint has been assembled and the seating of the gasket checked with the tracer, the sleeve is folded over, pulled to the end-face of the socket and rolled over the socket. It then rests firmly and closely in place.

123

Shrink-on devices and protectivetapes

As an alternative to the cement mortar protecting sleeve, the joint region can also be protected with shrink-on devices or protective tapes. The shrink-on device must be suitable for the dimensions of the particular joint involved.

Applying a shrink-on collar

The shrink-on collar has to be pulled over the socket end before the joint is made.The surface to be enclosed has to be pre-pared in accordance with DVGW Merk-blatt GW 1�, i.e. the region has to be freed of rust, grease, dirt and loose par-ticles. The surface must be pre-heated to approx. �0°C with a propane gas flame set to a soft setting and thus dried.The shrink-on collar is then pulled over the joint until it is central on it and the protec-tive backing on the inside is then removed.At the point where the end-face of the socket is situated, the shrink-on collar is then heated evenly, all round, with a pro-pane gas flame set to a soft setting until the shrinking process begins and the sleeve starts to assume the outline shape of the socket. Then, while keeping the tem-perature even, which should be done by moving the burner in the circumferential direction while fanning it from side to side, the part of the collar around the socket is first shrunk on, and then, starting from the end-face of the socket, the part around the main body of the pipe.

ZMU

~ 100

12�


The operation has been properly carried out if• the whole of the collar has been shrunk onto the joint between the pipes,• it rests down flat, without any cold spots or air bubbles, and the sealing adhesive has

been pressed out at both ends,• the �0 millimetre overlap that is required over the cement mortar coating has been

achieved.

Wrapping with mortar bandage (produced by the Ergelit company)

Soak the mortar bandage thoroughly in a water-filled bucket until no air bubbles are be-ing released. This should take a maximum of two minutes.Take out the wet bandage and squeeze it gently.Wind the bandage onto the area that is to be enclosed (cover ≥ 50 mm of the ZMU) and match it to the outline.To give a six millimetre thick layer, wind the bandage round twice or make a �0% overlap.This post-insulation is able to accept mechanical loads after one to three hours.

Filling the pipe pit

The bedding for the pipes should be laid in accordance with DIN EN 80�/ DVGW W �00-2 or DIN 1�10/ATV-DVWK A 139, as the case may be.Virtually any excavated material, even soils containing stones up to a grain size of 100 millimetres, can be used as infill (see DVGW Arbeitsblatt W �00-2). An enclosing layer of sand or foreign material is only necessary in special cases.In the region of traffic-carrying surfaces, the Merkblatt for the filling of pipelines trenches (issued by the Road Research Company of Cologne) should be followed.Restrained joints protected with cement mortar protecting sleeves or shrink-on devices should be enclosed in fine-grained material or protected with pipe protecting mats.

Shortening of pipes

Up to the DN 300 size, the pipes supplied are able to be cut in the region of their main body, at a point up to one metre away from the end-face of the socket, to enable a connection to be made.Above the DN 300 size, only pipes which carry a continuous, white, lengthwise strip are able to be cut. Pipes of this kind (cuttable pipes) have to be ordered separately.An additional identifying mark for a cuttable pipe is an „SR“ on the end-face of the socket.

12�

ZMU

L2 L

Ls2 Ls

DNTYTON®/BRS®

L [mm]BLS®

LS [mm]

80 9� 1�� 100 100 17� 12� 100 18� 1�0 10� 190 200 110 200 2�0 11� 20� 300 120 210

(3�0) 120 – �00 120 230 �00 130 2�� 00 1�� 300 700 20� 31� 800 220 330 900 230 3��

1000 2�� 3�0

In the case of TYTON®, the ZMU-free length at the inserting end applies for sockets complying withDIN 28 �03 up to DN �00, shape A DN 700 and above, shape B (restrained socket)The ZMU is cut into, to approximately half the thickness of the ZMU layer, around the entire circumference of the pipe. When this is done, care must be taken not to damage the cast iron pipe.The ZMU is then also cut into in the longitudinal direction between the two circum-ferential cuts. All the cuts are then forced apart with a chisel. After this the ZMU can be detached all round by tapping it gently with a hammer, starting at a point where it is

Before a pipe is cut, the ZMU should be removed for a length of 2 L or 2 LS, as the case may be, as shown in the table below. (Where there are collars, the dimension for the fitting of the collar should be taken into account as well).

12�


split longitudinally. On pipes of DN 700 - DN 1000 sizes, it may be necessary, before the ZMU is detached, for it to be heated with a propane gas flame. The inserting end should be cleaned with a scraper and a wire brush.The pipes can then be cut with disc cutters or grinders. Cutting discs for stone are suit-able for cutting the pipes, e.g. the C 2� RT Spezial type.Protective goggles and respiratory protection must be worn when cutting pipes.The cut edge should be bevelled to match the original inserting end using a hand-held grinder. Any material which is ground off has to be removed from the inside of the pipe. It is essential for the zinc covered inserting ends which are produced to be recoated with a suitable cover coating.

Fitting of under-pressure tapping fittings

When under-pressure tapping fittings are being fitted, the ZMU should be removed in the region of the sealing surface in such a way that the seal of the tapping fitting seals against the cleaned surface of the pipe. Once the tapping fitting has been fitted, the sur-face of the pipe which is still exposed should be re-insulated in the appropriate way.Alternatively, the ZMU can be smoothed in the region of the drilled hole with a hand-held grinder or a rasp to a level below the net bandage. An under-pressure tapping fitting is placed on this region and sealed off on the ZMU.Another possibility is for the under-pressure tapping fittings used to be ones which seal in the drilled hole. See also DVGW Merkblatt W 333.

On-site repair of the ZMU

Parts of the ZMU which have come free may only be repaired with the repair kit which is supplied with the pipes by the pipe manufacturer.The repair kit contains a mixture of cement, sand and plastic fibres, gauze tape and a mortar hardener. The materials contained in the repair kit are mixed until a mortar able to be applied with a spatula is obtained. As dictated by the outside temperature, water can be mixed in what this is done. The damaged points on the ZMU are cleaned and wetted and mortar is then applied to them with a spatula. Damaged areas of any great size (larger than the palm of the hand) must be covered with gauze tape after the mortar has been applied.Where pipes have their cement coating repaired, a wait of at least twelve hours is rec-ommended before they are installed or else the repaired area should be given adequate protection against mechanical stresses.

127

ZMU

Trenchless Installation


Bude

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Man

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Buderus Giesserei Wetzlar GmbHCast Iron Pipe Technology

P.O. Box 1240 D-35573 WetzlarPhone: +49 (0) 64 41 49 - 22 60

Fax: +49 (0) 64 41 49 - 16 13E-Mail: [email protected]

www.gussrohre.com

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