BS 8010-2.1

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A single copy of this British Standard is licensed to

Akin Koksal

29 March 2003

This is an uncontrolled copy. Ensure use of the most

current version of this document by searching British

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Amendment No. 1

Code of practice for

Pipelines —

Part 2: Pipelines on land: design,

construction and installation —

Section 2.1 Ductile iron

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This British Standard, having been prepared under the direction of the Civil Engineering and Building Structures Standards Committee, was published under the authority of the Board of BSI and comes into effect on

27 February 1987 © BSI 12-1998

This publication of this British Standard was entrusted by the Civil Engineering and Building Structures Standards Committee (CSB/-) to Technical Committee CSB/10, upon which the following bodies were represented:

Association of Consulting Engineers British Compressed Gases Association British Gas Corporation

British Plastics Federation

British Precast Concrete Federation Ltd. British Railways Board

Chemical Industries Association Concrete Pipe Association Country Landowners’ Association County Surveyor’s Society

Department of Energy (Petroleum Engineering Division) Ductile Iron Producers Association

Electricity Supply Industry in England and Wales Engineering Equipment and Materials Users’ Association Federation of Civil Engineering Contractors

Health and Safety Executive Home Office

Institute of Petroleum Institution of Civil Engineers Institution of Gas Engineers Institution of Mechanical Engineers Institution of Public Health Engineers Institution of Water Engineers and Scientists Ministry of Agriculture, Fisheries and Food National Farmers’ Union

Pipeline Industries Guild

Royal Institution of Chartered Surveyors Society of British Gas Industries UK Offshore Operators Association Ltd. Water Authorities Association

Water Companies Association Water Research Centre

The following body was also represented in the drafting of the standard, through subcommittees and panels:

Association of Municipal Engineers

Amendments issued since publication

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Page Figure 1 — Push-in joint (type 1) 20 Figure 2 — Bolted mechanical joint (type 2) 20 Figure 3 — Slip-on coupling (type 3) 21 Figure 4 — Flange adapter (type 4) 21 Figure 5 — Self-anchoring flange adapter (type 5) 22 Figure 6 — Self-anchoring push-in joint (type 6) 22 Figure 7 — Self-anchoring tie-bar joint (type 7) 23 Figure 8 — Self-anchoring bolted mechanical joint (type 8) 23 Figure 9 — Lead-caulked joint (type 9) 24 Figure 10 — Flanged joint (type 10) 24 Table 1 — Maximum hydraulic working pressures, exclusive of surge,

for ductile iron pipes and fittings and flanged joints 6 Table 2 — Maximum site hydrostatic test pressures for

ductile iron pipes and fittings and flanged joints 7 Table 3 — Stacking heights 13 List of references Inside back cover

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Foreword

This Section of BS 8010 has been prepared under the direction of the Civil Engineering and Building Structures Standards Committee. The standard is being published in four Parts to form a complete revision of all Parts of CP 2010 as follows.

— Part 1: Pipelines on land: general;

— Part 2: Pipelines on land: design, construction and installation; — Part 3: Pipelines subsea: design, construction and installation; — Part 4: Pipelines on land and subsea: operation and maintenance. The new Part 1 (which will supersede CP 2010-1:1966) is intended to contain general information which is relevant to a variety of pipeline construction materials and a variety of transported materials. It deals with those aspects of pipeline development which affect the owner and occupier of land through which the pipeline passes.

Part 2 is divided into several Sections which will be published as separate documents as follows.

— Section 2.1: Ductile iron; — Section 2.2: Steel;

— Section 2.3: Asbestos cement; — Section 2.4: Prestressed concrete;

— Section 2.5: Glass reinforced thermosetting plastics; — Section 2.6: Thermoplastics;

— Section 2.7: Precast concrete.

Each Section will contain information on the design, construction and installation of a pipeline in the particular material. These Sections will supersede the existing Parts 2, 3, 4 and 5 of CP 2010.

This Section supersedes CP 2010-3:1972. The content and the title of the 1972 edition have been changed to refer to ductile iron only, as grey iron is no longer used as a material for pipelines. By the exclusive use of ductile iron it has been possible to raise the pressure ratings and introduce self-anchoring joints. Part 3 will include information relevant to the design, installation and commissioning of subsea pipelines in steel and other materials.

Part 4 will contain advice on the operation and maintenance of pipelines and will probably be in Sections related to the conveyed material.

Appendix A describes and illustrates some typical types of joint used with ductile iron pipe.

Appendix B gives requirements for non-metallic materials for use with potable water.

It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. Attention is drawn to the following principal statutory legislation in the UK. This list is not intended to be complete and the relevant authorities should be consulted and reference made to Part 1. These Acts are supplemented by Statutory Instruments.

Acquisition of Land Act 1981; Control of Pollution Act 1974; Countryside Act 1968;

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Countryside (Scotland) Acts 1967 and 1981; Gas Acts 1965 and 1972;

Land Powers (Defence) Act 1958; Pipelines Act 1962;

Public Health Acts 1936 and 1961;

Requisitioned Land and War Works Act 1948; Water Acts 1945, 1948, 1973, 1975, 1981 and 1983; Water (Scotland) Acts 1946, 1949, 1967 and 1980.

A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity from legal obligations.

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Subsection 1. General

1

Scope

This Section of BS 8010 gives design considerations and construction and installation recommendations for ductile iron pipelines and should be read in conjunction with Part 11).

This British Standard code of practice is not intended to replace or duplicate hydraulic, mechanical or structural design manuals.

NOTE 1 The numbers in square brackets in the text of this Section refer to the numbered references in Appendix C. NOTE 2 The titles of the publications referred to in this standard are listed on the inside back cover.

2 Definitions

For the purposes of this Section of BS 8010, the following definitions apply.

2.1

ductile iron2)

iron in which graphite is present substantially in spheroidal form, instead of in flakes such as occur in grey iron

2.2 pipeline

a line of pipes, of any length, without frequent branches. It does not include piping systems such as process plant piping within refineries, factories or treatment plant

2.3

flexible joint2)

a connection between individual pipes and/or fittings that provides angular deflection or axial movement, or a combination of both, in service, without impairing the efficiency of the connection

NOTE See Appendix A.

2.4

rigid joint

a connection that is designed not to permit angular deflection or axial movement in service

2.5

self-anchoring joint

a connection that is designed to prevent separation under the axial thrust induced by internal pressure, temperature fluctuations or ground movement whilst still permitting angular deflection and/or axial movement without impairing the efficiency of the joint

2.6 stringing

the placing of pipes in line on the ground ready for laying

2.7

surge pressure

pressure that is produced by a change in velocity of the moving fluid. Surge pressure may be positive or negative

3 Applications

The pipelines covered by this Section of BS 8010 are generally suitable for conveying water, sewage, trade waste, slurries, sludges, non-corrosive gases, brine and certain chemicals. Ductile iron pipes are used in distribution systems for natural and town gases and they may also be used in pipelines for the conveyance of these fuel gases under similar service conditions. For limits of pressure adopted by the British Gas Corporation in the United Kingdom and guidance in connection with the installation of ductile iron pipelines for gas, reference may be made to IGE/TD/3 [1]. When used for the conveyance of sewage, reference should be made to BS 8301 and CP 2005. Ductile iron is suitable for pipelines in locations where ground instability, traffic loading and frost effects present potential hazards and in areas where damage risks are high.

4 Safety

4.1 General

The recommendations of this Section of BS 8010 are considered to be adequate for public safety under conditions usually encountered in ductile iron pipelines, including pipelines within towns, cities, water catchments and industrial areas. Attention is called to the need to consider measures to prevent damage or leakage arising from:

a) corrosive soil conditions; b) internal corrosion/erosion;

c) external damage by mechanical equipment used on other works;

d) erosion or ground subsidence; e) any abnormal circumstances.

4.2 Preventative measures

Consideration should be given to the use of preventative measures such as the following:

a) additional external protection (see 19.2);

1) _{In preparation.}

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b) additional internal linings (see 19.3) and/or limitation of flow velocities;

c) provision of increased cover or a concrete cover as a protection against external mechanical damage, or erosion;

d) for serious subsidence, additional flexible joints, anchored joints, rafts or piling;

e) indication of the presence of the pipeline with additional markers particularly in congested areas or areas where future development is known to be planned, and adequate marking at river and water course crossings;

f) provision of protection from frost for pipelines above ground or in ducts.

5 Inspection

The integrity of a properly designed pipeline depends more on the standards and quality of inspection applied at all stages than on any other single feature.

Particular attention should be given to inspection of the pipe and coating before installation for possible damage, of the bedding of the pipeline, jointing and anchoring and to testing. Any sub-standard

materials or workmanship detected should be rectified or, where necessary, rejected, before any further work is done.

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Subsection 2. Materials and availability

6 General

Ductile iron pipes and fittings should comply with BS 4772. Ductile iron possesses high tensile strength, ductility and resistance to impact fracture, which makes it suitable for the

applications referred to in clause 3. It is capable of deforming to a significant extent before fracture. All materials should be compatible with the products that are to be conveyed in the pipeline. All materials, including repair materials, likely to come in contact with potable water should be incapable of permitting bacterial growth. Non-metallic materials should comply with the requirements for the effect of non-metallic materials on water quality (see Appendix B).

7 Pipes

7.1 Spigot and socket pipes

Ductile iron pipes are manufactured in accordance with BS 4772 in lengths of 5.5 m for DN 80 to DN 800 inclusive and lengths of 8 m for DN 900 to DN 1600 inclusive.

A percentage of the pipes supplied may be of shorter length, in accordance with BS 4772. Special arrangements should be made for procuring shorter lengths, where these are considered necessary. External diameters for metric size ductile iron pipes complying with BS 4772 and metric size grey iron pipes complying with BS 4622 are such that the pipes are directly interchangeable. Metric size ductile iron pipes are not directly interchangeable with ductile or grey iron pipes in imperial sizes and appropriate change fittings should be used in accordance with BS 4772.

7.2 Flanged pipes

Flanged ductile iron spun pipes are manufactured by casting the pipe barrel centrifugally and then welding or screwing loose ductile iron flanges on to specially prepared ends. Short lengths are often supplied with integrally cast flanges. The lengths available will vary according to the source of supply. Flanged pipework is available in sizes DN 80 to DN 1600 inclusive.

7.3 Fittings

Fittings are generally of the all socket or flanged type. BS 4772 permits the supply of fittings beyond the specified range in certain aspects, such as:

a) laying dimensions; b) pressure rating;

c) permutations of branch/main diameters; d) configurations such as angle branches, crosses, etc;

e) joint ends, e.g. socket and spigot bends. Such fittings are deemed to comply with BS 4772 and are required to be marked as specified in BS 4772.

8 Valves

8.1 Control valves

Control valves should comply with one of the British Standard specifications listed below.

Valves outside the range of sizes, or differing in type or otherwise not complying with the specifications listed may be used, provided that they have at least equal strength and tightness and are capable of withstanding the test requirements of the appropriate specifications and the tests recommended in this Section of BS 8010.

A clear indication should be given on all valves of the direction of rotation needed to close the valve (see clause 12).

8.2 Air valves

Automatic air valves are available in a number of forms. The most common are single orifice, double orifice and kinetic. Reference should be made to the manufacturer’s recommendations.

9 Flanges

Dimensional details of flanges designated PN 10, PN 16, PN 25 and PN 40 should comply with BS 4772. These are dimensionally compatible with the corresponding flanges in accordance with BS 4504. Unless otherwise specified by purchaser, PN 16 flanges are supplied for working pressures up to and including 16 bar.

BS 4772 permits the use of high tensile steel bolts of smaller diameter than the corresponding low carbon steel bolts, to facilitate manufacture and

installation of larger diameter flanges. Such flanges are marked accordingly. Where high tensile bolts are used with flanges holed for low carbon steel bolts, special washers should be used in accordance with the pipe manufacturer’s recommendations.

BS 5150 Cast iron wedge and double disk gate valves for general purposes. BS 5152 Cast iron globe and globe stop

and check valves for general purposes.

BS 5153 Cast iron check valves for general purposes.

BS 5155 Specification for butterfly valves. BS 5163 Double flanged cast iron wedge

gate valves for waterworks purposes.

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NOTE Flanges complying with other standards may be supplied against special orders.

10 Bolts, nuts and washers

Low carbon steel bolts and nuts should comply with BS 4190 and high tensile steel bolts and nuts should comply with BS 3692, minimum grade 8.8. Washers should comply with BS 4320.

11 Gaskets

11.1 General

Elastomeric components of gaskets should comply with the requirements of BS 2494 but other materials may be used if they have been proven to be more suitable.

The section of gaskets which is likely to come in contact with potable water, and gasket lubricants, should be incapable of permitting bacterial growth and should comply with the requirements for the effect of materials on water quality

(see Appendix B). Where the product conveyed might have a deleterious effect on the gasket, the gasket should be provided with a protective tip of suitable material to isolate it from the contents of the pipeline.

Maximum temperature limitations apply to the use of both natural and synthetic rubbers. These limitations vary with the type of material used and the design of joints. The manufacturer’s advice should be sought if the likely temperature is below 0 °C or above 50 °C for mechanical joints or above 60 °C for push-in joints (see Appendix A). Gaskets should be protected from unnecessary exposure to the effects of ultra-violet light and ozone.

NOTE Gaskets for flexible joints are frequently referred to as joint rings.

11.2 Flange gaskets

The dimensions of gaskets for flanges designated PN 10, PN 16, PN 25 and PN 40 should comply with BS 4865. The use of moulded gaskets designed to suit a range of nominal pressure ratings is permitted.

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Subsection 3. Design considerations

12 Pipeline design

The necessary hydraulic, structural and economic assessments should be made in accordance with recognized practice [2] and [3].

On new installations, consideration should be given to standardizing the direction of rotation needed to close valves as clockwise.

A clear indication should be given on all valves of the direction of rotation needed to close the valve. The direction of rotation for closure should be the same for any one pipeline installation.

13 Pipe design

13.1 Works hydrostatic test pressure

Each pipe and fitting should be subjected to a hydrostatic test at the manufacturer’s works. The pressure is required to be applied steadily and maintained for a period sufficient to facilitate adequate inspection and not less than 15 s.

NOTE Practical considerations limit the works hydrostatic test pressure to values which may be lower than the site test pressure.

13.2 Working pressure

Maximum working pressures for classes of pipes and fittings in accordance with BS 4772 are given in Table 1.

13.3 Surge pressures

The maximum surge pressure should be calculated. It is essential that the total pressure of the pipeline, including surge, does not exceed the pressure given in Table 2. Should it be found that this pressure is likely to be exceeded then protective devices, such as those described in clause 17, should be installed to reduce the actual surge pressure so that the above criterion can be met.

13.4 Site hydrostatic test pressure

The site hydrostatic test pressures for ductile iron pipes and fittings and flanged joints in accordance with BS 4772 should be not less than:

a) the working pressure + 5 bar;

b) the maximum pressure under surge conditions; but should not exceed the pressures given in Table 2.

14 Service and environmental

considerations

14.1 General

The pipeline internal pressure may be subject to limitations according to the service and

environmental conditions in which the pipeline operates.

14.2 Pipelines for liquids

The internal design pressures for the conveyance of liquids should not exceed the pressures given in Table 1.

14.3 Pipelines for gases

Where the pipeline conveys a gas and there is, therefore, a considerable amount of energy stored in the compressed gas in the pipeline, operating pressures are restricted, see IGE/TD/3 [1]. Gas operating pressures of the order of 8 bar may be permitted in ductile iron pipelines depending on the type of joint used and the environmental conditions. At these pressures, consideration should be given to the use of self-anchored mechanical joints.

NOTE Such joints provide restraint within the joint and thus dispense with the need for the traditional form of concrete thrust or anchor block (see Appendix A).

14.4 Pipelines for liquids and gases

14.4.1 Vacuum and external fluid pressure. The

pipeline should be capable of withstanding a differential pressure brought about by internal vacuum or external fluid pressure

(e.g. ground water). Where external pressure exceeds internal pressure by more than 1 bar, the manufacturer’s advice should be sought on the choice of joint.

14.4.2 External loading. Ductile iron pipes have

adequate strength for all normal installations when operating up to the maximum recommended internal pressures for each type of pipe. Where it is necessary to consider the effects of external loads, calculations should be made in accordance with one of several recognized approaches for computing trench loads, pipe deflection and pipe stress, some of which are listed in Appendix D. Consultation with manufacturers should be made where abnormal laying conditions are encountered, e.g. very deep or very shallow with vehicular loading.

14.4.3 Thermal insulation. Pipelines carrying water

that have a depth of cover of at least 0.9 m are not normally subject to freezing in the UK. Where this depth of cover cannot be achieved, adequate thermal insulation should be provided and maintained (see CP 3009) or the system should be designed so that there is always a flow through the pipeline.

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Table 1 — Maximum hydraulic working pressures, exclusive of surge, for ductile iron pipes and

fittings and flanged jointsb

Nominal

size DN Maximum hydraulic working pressures Class K9 centrifugally cast pipes.

Class K12 fittings (including flange pipes with integrally cast flanges)

Class K14 fittings

(i.e. tees) and thicker Flanged joints

PN 10 PN 16 PN 25 PN 40

barc _bar _bar _bar _bar _bar

80 60 60 10 16 25 40 100 60 60 10 16 25 40 150 60 60 10 16 25 40 200 60 50 10 16 25 40 250 53 40 10 16 25 40 300 47 40 10 16 25 40 350 43 25 10 16 25 40 400 40 25 10 16 25 40 450 38 25 10 16 25 40 500 36 25 10 16 25 40 600 33 25 10 16 25 40 700 31 25 10 16 25 800 29 25 10 16 25 900 28 25 10 16 25 1 000 27 25 10 16 25 1 100 26 25 10 16 25 1 200 25 25 10 16 25 1 400 25 25 10 16 25 1 600 25 25 10 16 25

NOTE 1 The maximum hydraulic working pressures of pipes and fittings in other classes will vary from those given in Table 1. The manufacturer should be consulted by the purchaser with regard to the production of such pipes and fittings.

NOTE 2 Not all flexible joints are suitable for the pressures given in Table 1 and manufacturers should be consulted for the maximum hydraulic working pressures for particular joint designs.

NOTE 3 The maximum hydraulic working pressures given for flanged joints apply to joints in which axial thrusts generated by internal pressure impose tensile stresses to the bolting. Where the bolting of flanged joints is not subjected to tensile stresses created by axial thrusts from internal pressure (e.g. flanged valves connected by flanged sockets and flanged spigots in a spigot and socket non-anchored pipeline) the preferred PN 16 flange is capable of operating at the pressures given for class K9 centrifugally cast pipe.

NOTE 4 The maximum hydraulic working pressure ratings of flanged pipes and fittings is the rating of the flange or the rating of the pipe or fitting body, whichever is the lower.

NOTE 5 The maximum hydraulic working pressures for pipes and fittings with flanges are applicable in the temperature range – 10 °C to 120 °C. The manufacturer should be consulted in connection with maximum hydraulic working pressures for temperatures outside this range and for information in respect of the suitability of specific gasket materials for operating at particular temperatures.

NOTE 6 Internal pressure induces higher stresses in fittings with branches, i.e. tees, than in fittings without branches, consequently the maximum hydraulic working pressures for tees in classes K14 and thicker are often lower than for class K12 fittings without branches.

b _{This table extracted from BS 4772.} c _{1 bar = 10}5_N/m2_{= 100 kPa.}

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Table 2 — Maximum site hydrostatic test pressures for ductile iron pipes and fittings and flanged joints

Nominal size DN

Maximum site hydrostatic test pressures Class K9 centrifugally cast pipes.

Class K12 fittings (including flange pipes with integrally cast flanges)

Class K14 fittings (i.e. tees) and thicker

Flanged joints

PN 10 PN 16 PN 25 PN 40

bar bar bar bar bar bar

80 65 65 16 25 40 45 100 65 65 16 25 40 45 150 65 65 16 25 40 45 200 65 55 16 25 40 45 250 58 45 16 25 40 45 300 52 45 16 25 40 45 350 48 30 16 25 40 45 400 45 30 16 25 40 45 450 43 30 16 25 40 45 500 41 30 16 25 40 45 600 38 30 16 25 40 45 700 36 30 16 25 30 800 34 30 16 25 30 900 33 30 16 25 30 1 000 32 30 16 25 30 1 100 31 30 16 25 30 1 200 30 30 16 25 30 1 400 30 30 16 25 30 1 600 30 30 16 25 30

NOTE 1 The maximum site hydrostatic test pressures of pipes and fittings in other classes will vary from those given in Table 2. The manufacturer should be consulted by the purchaser with regard to the testing of such pipes and fittings. NOTE 2 Not all flexible joints are suitable for the pressures given in Table 2 and manufacturers should be consulted for the maximum site hydrostatic test pressures for particular joint designs.

NOTE 3 The maximum site hydrostatic test pressures given for flanged joints apply to joints in which axial thrusts generated by internal pressure impose tensile stresses to the bolting. Where the bolting of flanged joints is not subjected to tensile stresses created by axial thrusts from internal pressure (e.g. flanged valves connected by flanged sockets and flanged spigots in a spigot and socket non-anchored pipeline) the preferred PN 16 flange is suitable for the test pressures given for class K9 centrifugally cast pipe.

NOTE 4 The maximum site hydrostatic test pressure of flanged pipes and fittings is the lower of that applicable to the flange or the pipe or fitting body.

NOTE 5 The maximum site hydrostatic test pressure for pipes and fittings with flanges are applicable in the temperature range –10 °C to 120 °C. The manufacturer should be consulted in connection with maximum site hydrostatic test pressures for temperatures outside this range and for information in respect of the suitability of specific gasket materials for operating at particular temperatures.

NOTE 6 Internal pressure induces higher stresses in fittings with branches, i.e. tees, than in fittings without branches, consequently the test pressures for tees in classes K14 and thicker are often lower than for class K12 fittings without branches. NOTE 7 When operating temperatures in excess of 60 °C are expected consideration should be given to carrying out the test at the operating temperature.

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14.4.4 Temperature range. The temperature range for ductile iron pipelines is limited to that of the gasket and is normally 0 °C to 50 °C or 60 °C as appropriate (see clause 11). Special elastomeric gaskets are available for the temperature

range – 10 °C to 120 °C with peaks of up to 130 °C. Gaskets of other materials should be used for temperatures beyond this extended range. Where substantial variations in pipeline temperature may occur, provision should be made for thermal movement. Flexible joints can accommodate normal thermal movement but special installations, such as bridge crossings where the movement may be localized, may require the inclusion of a special expansion joint. Where pipelines are subjected to substantial temperature variations, the effects of fluid expansion of the internal pressure during shut-down should be taken into account and pressure-relieving devices should be installed, if required.

15 Pipelines on supports

15.1 General

For pipelines or sections thereof carried on supports, whether above ground, or buried in ground having an inadequate load bearing capacity, the spacing of the supports depends upon the type of joint and the load imposed on the pipeline. Account should be taken of the variation in length of pipes permitted in BS 4772. In all cases the beam strength and the effect of load concentration at supports should be checked. Adequate anchorage of the pipe to the support should be provided.

15.2 Pipelines on piers above ground

15.2.1 Flexibly jointed pipes. In normal installations

where the pipe is required to carry only its own mass and contents, one support per pipe, cradling the pipe over at least 90° and positioned immediately behind the socket, is recommended.

NOTE This arrangement allows free articulation of the joint to accommodate temperature movement or settling of the support and ensures that each support carries an equal share of the load.

Where double spigot pipes and coupling are used, twin supports should be provided adjacent to and on each side of the coupling.

Where a pipeline is required to span more than one pipe length, e.g. at stream crossings, special supporting arrangements should be provided to allow a single span of two pipe lengths for socket and spigot pipes. The manufacturer’s advice should

15.2.2 Flanged pipes. In installations where the

pipe is required to carry only its own mass and contents, the maximum span should be 8 m for sizes up to and including DN 250 and 12 m for sizes DN 300 and above. These spans may be increased in some circumstances, e.g. where the pipeline is working at less than the rated pressure of the flange or where the pipeline can be designed as a

continuous beam. The manufacturer’s advice should be sought if increased spans are required.

In all cases, the supports should be accurately aligned to ensure that each carries the designed load and cradles the pipe over at least 90°.

15.2.3 Pipes carrying superload. The

manufacturer’s advice should be sought where the pipes are required to carry loads greater than their own mass and contents.

15.3 Pipelines on piers below ground

Pipelines laid on piers below ground may be subject to extremely high loads and the manufacturer’s advice should be sought. Where buried pipelines are supported on wooden piers, a layer of isolating material, e.g. polyethylene sheet., should be inserted to prevent contact between the pier and the pipeline.

16 Access to the pipeline

The design should take full account of the pipeline route and layout and ensure that adequate access is available to all parts of the pipeline. In large diameter pipes, internal access should be provided at suitable intervals for inspection, maintenance and removal of obstructions and consideration should be given to the need to provide a safe working environment at all times. Where the use of scraping or swabbing equipment is contemplated, provision for insertion and extraction and the removal of debris should be made at suitable locations.

17 Protective devices and under

pressure connections

Protective devices such as relief valves, surge chambers, pressure limiting stations, and automatic shutdown equipment should be provided where necessary, to ensure that the internal pressure at any point in the pipeline system does not exceed the site hydrostatic test pressure of the pipes used. This is particularly important where any pipeline is connected to another pipeline that is designed for a

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17.1 In-line valves

Valves should be placed in the pipeline at intervals so that sections of the pipeline can be isolated and emptied, if necessary, within a reasonable time and without too great a loss of material. At special crossings of major roads, water courses, and railways or other such major points, or in extremely hazardous locations, consideration should be given to the fitting of valves to isolate the section

concerned, having due regard to the material being conveyed. Consideration should be given to

providing locking arrangements for valves, particularly if butterfly valves are used. Valves should be placed in positions which allow easy access and minimize interference with the use of the land. On larger pipelines in-line valves should be fitted with devices to indicate the degree of opening. Bypass and hydrant arrangements are also

recommended for ease of operating and recommissioning sections.

17.2 Air valves

Air release valves should be provided between isolating valves on pipelines transporting liquid, for the release and admission of air during filling and emptying of sections of the pipeline and for bleeding off air released by solution during operation of the pipeline.

The type of air valve (small single orifice, large single orifice, double orifice or kinetic) should be selected after consideration of the duty and location of the valve and the nature of liquid or gas to be conveyed. Air valves should be located at all topographic high points and at high points on the pipeline with respect to the hydraulic gradient, and should also be located at intervals along any sections where the gradient of the pipeline is parallel to or less than the hydraulic gradient. On long sections of pipeline of even gradient, air valves should be positioned at intervals of

approximately 0.5 km, depending on the diameter of pipeline and the air valve chosen. Air valves may also be required where the gradient of the pipeline changes.

The chamber housing an air valve should be designed to be free draining and free from risk of flooding or possible back siphonage. It is essential that the chamber housing an air valve is properly ventilated or provided with an adequate discharge into the atmosphere.

17.3 Drainage valves and washouts

Drainage valves should be provided between isolating valves for emptying sections of pipelines transporting liquids and for flushing out the pipeline while in service. Drainage valves on water pipelines should discharge to a watercourse or ditch through a washout pipe, although in urban areas it may be necessary to construct a discharge chamber from which water is pumped to the surface water drainage system. On sewage pipelines, discharge should be made to a watertight chamber, controlled by a valve at the end of the washout pipe or be returned to a convenient gravity foul sewer. The relevant water or drainage authority should be consulted with respect to the allowable size and location of washout discharge.

NOTE The gradient between air release valves and between drainage valves should not normally be less than 1:250 although in special cases a minimum gradient of 1:400 may be used.

17.4 Under pressure connections

These specialized fittings are used to take branches from existing live pipelines. Several designs are available and the particular manufacturer’s recommendations should be followed.

18 Joints

18.1 General

Flexible joints are of proprietary design and the manufacturer’s guidance should be sought

regarding interchangeability. The gasket and pipe joint should be in accordance with the

manufacturer’s dimensions and tolerances. The gasket should be of such size and shape that, when jointed in accordance with the manufacturer’s instructions, it provides a positive seal within the manufacturer’s range of maximum joint deflection and spigot withdrawal, under all combinations of joint and gasket dimensional tolerances and in the range of pressures likely to occur along the pipeline including, where applicable, pressures below atmospheric.

18.2 Types of joint

18.2.1 Joint selection.The pipeline should either be

designed with sufficient flexibility or be provided with sufficient restraint to prevent thermal movement from causing excessive stresses in the pipes, excessive bending or unusual loads at joints, and to prevent undesirable forces at or adjacent to points of connection to equipment or supporting structures, or at anchors, valves and branches. Account should also be taken of the effects of ground movement. The type of joint to be used should be selected from those described below and illustrated in Appendix A.

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(type 1, see Appendix A) or a mechanical form (types 2, 3 and 4, see Appendix A).

Such joints offer little or no resistance against spigot withdrawal due to internal pressure and dynamic loading and should usually be anchored at changes of direction and at blank ends (see 26.3).

NOTE For low pressure gas installations, underground anchorage may not be required.

18.2.3 Flexible self-anchored joints.Flexible

self-anchored joints are either of the push-in form (types 6 and 7, see Appendix A) or mechanical form (type 8, see Appendix A). At changes in direction, blank ends, etc. these joints are an ideal alternative to the traditional concrete anchor block especially in areas where the latter is undesirable on technical grounds, e.g. very soft ground conditions, remote areas, in busy streets, etc. Careful consideration should be given to the number of anchorage points in order to achieve satisfactory anchorage using self-anchoring joints. It is rarely satisfactory to anchor the fitting alone since this will only move the point of possible separation further along the pipeline. However, it is not normally necessary to anchor the entire pipeline and the manufacturer or other expert authority should be consulted to give guidance on the number of joints which need to be anchored.

NOTE Specific recommendations for gas pipelines are given in IGE/TD/3 [1].

18.2.4 Rigid non-anchored joints.Where connections

are to be made to existing pipelines, which may be in imperial sizes, it may be necessary to use the traditional lead-caulked joint

(type 9, see Appendix A). This joint allows no deflection or spigot withdrawal and it is essential that it be anchored if there is any possibility of joint separation.

18.2.5 Rigid anchored joints.Rigid anchored joints

are of the flanged design (type 10, see Appendix A). They give no provision for deflection but are self-anchored and, therefore, no external anchorage is required at changes in direction or at blank ends. Self-anchoring flange adapters

(type 5, see Appendix A) obviate the need for external anchorage but offer limited resistance to deflection and should be supported to prevent sag under the mass of the pipe and its contents. It is essential that flanged joints are tightened to a predetermined torque using clean bolts, lubricated on all mating surfaces, to ensure that the design load is obtained. Advice on recommended torques should be obtained from the manufacturer.

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Subsection 4. Protection against corrosion

19 Pipes and fittings

19.1 General

Pipes should comply with the requirements for corrosion protection specified in BS 4772. In sizes DN 80 to DN 800 the pipes are required to be zinc coated externally prior to bitumen coating

internally and externally. For sizes DN 900 to DN 1600 pipes are required to be cement mortar lined and coated externally with bitumen. All fittings are required to be coated internally and externally with a bitumen material. The bitumen to be used should comply with BS 3416 type II or BS 4147 type 1.

19.2 Additional external protection

In naturally corrosive soils (usually water-logged heavy clays and saline and peat marshes

characterized by an electrical resistivity

below 40Ω⋅m) additional external protection should be provided, e.g. by the correct application of loose polyethylene sleeving as specified in BS 6076.

NOTE Guidance on the correct application of polyethylene sleeving is available from pipe manufacturers and Water Research Centre Information and Guidance Note No. 4-50-01 [4].

In made-up ground containing industrial debris, or in natural soils containing large, sharp-edged stones, shale or flints, the polyethylene sleeving may be liable to mechanical damage during backfilling. Selected backfill should be used to prevent damage to polyethylene sleeving. Where there is a risk of electrical interference currents, or in abnormally corrosive ground, consideration should be given to the use of a more robust protective coating, such as bitumen

sheathing or protective tape, alone or with cathodic protection, and advice should be sought from manufacturers or other expert advisory body.

19.3 Additional internal linings

Where the contents of the pipeline are conducive to tuberculation, the pipes should be cement mortar lined or protected by other suitable linings.

20 Joints containing steel components

Where steel is used for bolts, nuts and washers, slip-on couplings, or anchorage devices, protection from corrosion should be provided.

Protection can be afforded by packing a suitable mastic material over the components and the adjacent external surface of the pipe so as to form a continuous layer with a smooth profile which can subsequently be wrapped with a compatible cold-applied tape (e.g. petrolatum-based or plastic-backed types, depending on the mastic used). Care should be taken to ensure there are no voids between the mastic and the pipe component substrate, nor between the tape and the mastic. Alternatively, heat-shrinkable sleeves can be obtained for the protection of certain profiles, e.g. flanged joints, bolted flange couplings.

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NOTE See BS 8010-1 for procedures to be followed before any work is commenced. Part 1 details procedures and

recommendations for work on land which are common to all types of pipelines.

21 General

Pipes should be loaded and handled with reasonable care in accordance with the manufacturer’s

recommendations and should not be dropped. Although ductile iron pipes are not susceptible to breakage by impact loading, bad handling can result in damaged coatings or linings and, in severe cases, deformation of the spigot, which could affect the sealing of the joint.

Particular attention should be paid to the following to prevent damage to pipes or joint components:

a) securing of loads on lorry or wagon;

b) correct use of suitable handling equipment; c) correct stacking methods;

d) proper storage of joint components.

22 Transport

All pipes should be secured to the lorry or railway wagon during transit to prevent movement. The means of securing should be designed to minimize damage to the coating. The pipes may be loaded on to the vehicle in pyramid or straight-sided

formation.

When pyramid loaded, the pipes in the bottom layer should be restrained by the use of profiled cradles or broad wooden wedges secured to the vehicle platform. The pyramid should be built by resting the pipes between pairs of pipes in the preceding layer with the sockets in successive layers reversed. Straight-sided loading should only be used where vehicles have purpose designed supports along the sides of the vehicle platform or where special cradles separating the layers are used, or where pipes are bundled.

23 Handling and storage

23.1 Off-loading by crane

It is essential that pipe masses, type of stacking, outreach required and site conditions be taken into account when determining the suitability of lifting equipment. The lifting machine should be of the type which retains the load safely in the event of a power failure. Off-loading should be carried out smoothly and without snatch.

When cranes are used for off-loading individual pipes, slings or lifting beams with purpose designed padded hooks should always be used.

23.2 Off-loading without crane

Where lifting gear is not available and the mass of the pipe permits (normally DN 250 max.),

individual pipes should be off-loaded by rolling them down a ramp formed of timber skids extending from the vehicle side to the ground. During this

operation, suitable steadying ropes should be used to prevent the pipes from rolling down at excessive speeds and striking other pipes or objects on the ground.

23.3 Stacking non-bundled pipes

23.3.1 General. Pipes being taken to a central

stockground for storage and held pending further distribution should be arranged in stacks. The stacking area should provide a firm foundation with a suitable approach road for vehicles. Stacks should be arranged so as to provide safe vehicular and pedestrian access. During stacking and removal operations, safe access to the top of the stack is essential. In bad weather conditions, when pipe surfaces may become slippery, consideration should be given to the use of lightweight stagings placed on top of the stacks. Pipes should be stacked on a base of raised wooden battens at

least 100 mm thick × 225 mm wide. The battens should be positioned approximately 600 mm from each end of the pipe. The bottom layer of pipes should be securely anchored. Three types of stacking are recommended:

a) square stacking: suitable for pipes up to and including DN 400

b) parallel stacking using timber: suitable for pipes of all sizes;

c) pyramid stacking: suitable for pipes of all sizes.

23.3.2 Square stacking. Each tier of pipes should be

positioned with their axes at right angles to those of the preceding tier to form a stable and compact stack. The sockets of the pipes in each tier should be at the same end, except for the two end pipes which should be reversed to lock the tiers in position. Alternatively, the sockets of alternate pipes in each tier may be reversed. The pipes rest directly upon those beneath and extra care should be exercised when lowering the pipes into position to prevent damage to the protective coating.

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23.3.3 Parallel stacking using timbers. For this method of stacking, two timber battens of sufficient strength should be placed across the pipes between each tier, approximately 600 mm from the pipe ends. The sockets of pipes in each successive tier should be reversed and the battens should be of sufficient thickness to avoid metal to metal contact. An adequate number of chocks should be wedged under the outer pipes of each tier and nailed to the timber bearers to ensure stability.

NOTE Pipes may be rolled into position along the battens, thus facilitating stacking or removal from the end of the stack.

23.3.4 Pyramid stacking. In pyramid stacks, each

pipe nestles between the two pipes immediately beneath it and care should be exercised when lowering pipes into position. It is essential that the end pipes of the bottom tier be securely anchored along their length with chocks preferably fixed to timbers running the width of the stack. The axes of all pipes should be in the same direction, and the sockets should be reversed in successive tiers.

23.3.5 Stacking heights. The heights of stacks

should be determined by consideration of:

a) the stresses on the lowest layer of pipes in the stack;

b) the total lift given by the available crane; and c) the facilites available to ensure stable stacking. All these factors should be taken into consideration and the stacking heights should not exceed those in Table 3.

Table 3 — Stacking heights

23.3.6 Pipes having special external protection.

Wherever possible, pipes with special external protections should not be stacked but should be laid out in a single layer and supported on the shoulder of the socket and the unprotected spigot end, so that the whole barrel is clear of the ground. If the space available is limited, then reduced stacking may be permissible, in such circumstances the

manufacturer should be consulted. Care should be exercised when handling such pipes to avoid damaging the protection. They should be lifted by hooks engaging in the socket and spigot ends. The hooks should be as wide as possible and padded with rubber to minimize damage to cement linings. Smaller sizes, up to DN 400, may be lifted with wide fabric slings. Wire ropes or chain slings should not be used.

23.4 Stacking bundled pipes

23.4.1 General. The stacking area should provide a

firm foundation with a suitable approach road for vehicles. Stacks should be arranged to provide safe vehicular and pedestrian access. Bundles are provided with base timbers and these can be laid directly onto a good, level, hard-standing surface. The bundles should be stacked one on top of the other with the axes of pipes parallel.

The maximum recommended stacking height on a good, level, hard-standing surface is five bundles. However the maximum stacking height for any particular location should be determined by a competent supervisor.

23.4.2 Breaking down of pipe bundles. It is essential

that bundles which have been stacked be lowered to ground level before the straps are cut. Special precautions should be taken when cutting the straps of the bundles and when removing pipes from individual tiers. The manufacturer’s

recommendations should be followed.

23.5 Stringing

Pipes should be wedged or pinned to prevent accidental movement.

NOTE See also BS 8010-1.

Nominal size DN Maximum number of layers in stack 80 18 100 16 150 14 200 12 250 10 300 8 350 and 400 7 450 and 500 6 600 4 700 3 800 and above 2

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24 Trenching

NOTE See BS 8010-1 for general considerations regarding trenching.

The width of trench should be as narrow as practicable, taking into consideration the type of native soil and backfill and the compaction

equipment required. Where mechanical compaction is required, the width of the trench should be typically pipe o.d. + 600 mm but may be increased for heavier equipment.

Where mechanical compaction is not required, the width of trench should be typically pipe

o.d. + 300 mm but may be reduced where narrow trenching techniques are employed.

The trench bottom should be prepared to give an even bed for the barrel of the pipe and to ensure proper alignment. The bed should be provided with joint holes to ensure that the pipe rests on the barrel and not on the socket.

In rocky ground, the trench should be excavated at least 100 mm deeper than normally required and then made up to the required level by the addition of well compacted, selected bedding material or imported granular bedding.

Where a change in direction is being made by utilizing the lateral deflection available from flexible joints, the trench should be cut to give sufficient room for the joint to be made with the pipes in line, the pipe being deflected after the joint has been made. Deflection of any as-laid joint should not exceed 75 % of the maximum deflection

recommended by the manufacturer

(see Appendix A) to allow for subsequent movement.

25 Pipe inspection, repairs and cutting

25.1 Inspection

Ductile iron pipes are not normally susceptible to handling and transport damage but mishandling can damage protective coatings and linings or bruise and deform jointing surfaces and may create ovality. In the case of pipes to be used with a self-anchoring type 8 joint (see Appendix A), the presence, at the spigot end, of the groove for retaining the circlip should be checked.

25.2 Repairs of damaged external coatings and linings

25.2.1 Damage to concrete lining or zinc coating

should be repaired in accordance with BS 4772.

25.2.2 Coatings and linings. Damage should be

25.2.3 Special external coatings and linings.

Damaged coatings and linings should be made good. The materials and method to be employed will depend upon the material originally used and the protection required and should comply with the manufacturer’s recommendations.

25.3 Cutting

25.3.1 General. Methods of cutting ductile iron pipes

should be selected from the following.

a) By hand or power operated hacksaw, using blades having teeth at a pitch of 1 mm (24 teeth per inch).

NOTE This method is suitable for pipes up to DN 200.

b) By manually operated wheel cutter, with wheels specifically designed for use with ductile iron.

NOTE This type of cutter is suitable for pipes up to DN 300.

c) By pipe cutting machine, using cutting tools of the simple lathe or milling saw type. A 7° front rake is recommended for cutter heads in machines using lathe type cutting tools.

NOTE Pipe cutting machines are available throughout the diameter range and are usually driven mechanically, e.g. by compressed air motor, although for pipes smaller than DN 300 a hand operated windlass may be used.

d) By power driven abrasive wheel cutting

machine, with abrasive discs fitted to suitable hand tools, usually driven by compressed air or small internal combustion engines. It is

important that abrasive disc cutting equipment is specifically designed for use with ductile iron pipe, that it is used by a competent operator and that the disc type, size and spindle speed of the equipment are compatible.

NOTE This is the most widely used method for cutting ductile iron pipes. It has the advantage of being suitable for all sizes, with no need for adjustment to suit pipe size or to attach machinery to the pipe.

25.3.2 End preparation of cut pipes for jointing. Any

burrs or sharp edges left after cutting should be trimmed off by filing or grinding.

Where self-anchored joints of type 8

(see Appendix A) are to be used, the cut end of the pipe may be grooved and chamfered on site by means of one of a number of proprietary lightweight cutting machines specially adapted for the purpose. Where joints of type 1 or 6 (see Appendix A) are to be used, the cut ends should be chamfered by filing or grinding similar to the original spigot ends.

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For sizes up to and including DN 300 and for larger sizes where the pipes are marked as being suitable for cutting, the diameter will be within the tape tolerances given in BS 4772, but may be outside the ovality tolerances given in BS 4772. Manufacturer’s guidance should be sought as to re-rounding. Other pipes, when cut, may have tape diameters outside the tolerance and these should be ground or machined to the tolerances given in BS 4772. The ground or machined area of spigot projecting out of the socket-face should be coated to give a similar degree of protection as the rest of the pipe, see 25.2.

26 Laying, jointing and anchoring

26.1 Laying

Pipes should at all times be handled with care in accordance with the manufacturer’s

recommendations. Pipes should be lowered into the trench with tackle suitable for the mass of the pipes. A mobile crane or a well designed set of shear legs should be used and the positioning of the sling checked, when the pipe is just clear of the ground, to ensure a proper balance. Where lifting equipment is not available, small diameter pipes (normally DN 250 max.) should be lowered by hand using suitable ropes.

All persons should vacate the section of the trench into which the pipe is being lowered.

All construction debris should be cleared from the inside of the pipe either before or just after a joint is made. This can be done by passing a pull-through along the pipe, or by hand, depending on the diameter of the pipe. When laying is not in progress, a temporary end-closure should be fitted securely to the open end of the pipeline. This may make the pipes buoyant in the event of the trench becoming flooded, in which case the pipes should be held down either by partial re-filling of the trench or by temporary strutting.

26.2 Jointing

26.2.1 General. Jointing procedures will vary

according to the type of joint being used.

Basic conditions which should be ensured for all types of joint are:

a) cleanliness of all parts;

b) correct location of components;

c) centralization of spigot within socket; and d) strict compliance with the manufacturer’s jointing instructions.

The inside of sockets and the outside of spigots should be cleaned for at least the insertion depth for each joint. Glands and gaskets should be wiped clean and inspected for damage. Where lifting gear has been used to place the pipe in the trench it should be used to support the pipe and assist in centralizing the spigot in the socket. Where the pipeline is suspected to be subject to movement due to ground settlement or temperature variation, a suitable gap should be left between the end of the spigot and the bottom of the socket.

26.2.2 Jointing pipes laid on gradients. If pipes are

laid on steep gradients where the soil/pipe friction is low, care should be taken to ensure that no excessive spigot entry or withdrawal occurs. As soon as the joint assembly has been made, the pipe should be held in place and the trench backfilled over the barrel of the pipe.

Unless the gradient is 1:2 or steeper, anchorages are not normally necessary. However, for these very steep gradients, self-anchoring joints or anchor blocks at each socket are recommended.

For pipelines laid above ground on steep gradients, self-anchoring joints should be used.

26.3 Anchoring

Unless an adequate length of the line is fitted with self-anchoring joints, external anchorage should be provided at blank ends, bends, tees, tapers and valves to resist the thrust arising from internal pressure and dynamic loading. Anchors and thrust blocks should be designed to withstand the forces resulting from the internal pressure when the pipeline is under test, taking into account the safe bearing pressure of the surrounding soil.

Consideration should also be given to forces on the pipeline, when empty, and precautions taken against possible flotation. Where possible, concrete anchor blocks should be of such a shape as to leave the joint area clear.

27 Backfilling

NOTE See BS 8010-1 for general considerations regarding backfilling, clearing-up and reinstatement.

Wherever possible, in order to minimize

misalignment of the bed with resulting shear across the joint, backfill material should not be placed on a pipe until the succeeding pipe is laid and jointed. If joints are to be individually inspected during hydrostatic testing, it is not practicable to backfill the trench completely. It is important, however, to backfill over the barrel of each pipe and to compact the backfill or take other such measures to prevent movement of pipes during the testing processes.

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On pipes greater than DN 600 special attention should be given to the compaction of the backfill material under the haunch of the pipe.

In most cases tamped, selected excavated material, from the trench will be suitable for the backfill. The material selected for backfill should exclude debris, organic material, frozen soil, large stones, rocks, tree roots or similar large objects. In instances of excessive depths, high vehicular loading or

super-loading from buildings, etc. or of very poor soil properties it may be necessary to import backfill (see also 19.2). The manufacturer or other advisory body should be consulted where any doubt exists.

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Subsection 7. Cleaning, testing and commissioning

28 Cleaning

Before a pipeline can be considered ready for service it should be cleaned internally as thoroughly as possible to ensure that no foreign matter remains inside the pipe. The first stage of the cleaning operation, i.e. cleaning individual pipes during jointing, should be performed in accordance with

26.1. Pigs of suitable design, e.g. polyurethane swabs, may be used provided that the pipeline has been constructed to allow the passage of such pigs. Where the pipeline is to be tested with water, the filling and emptying of the pipeline may to some extent cleanse the line.

29 Testing

29.1 General

All pipelines should be tested before being brought into service. The type of test will depend upon the fluid which the pipeline will eventually convey and may be a hydrostatic test or a pneumatic test, or both. The hydrostatic test is safer to carry out and can be made more stringent as regards the strength of a completed pipeline. It should be used wherever practicable, but it has certain disadvantages when applied to pipelines designed to carry gases. With the exception of testing non-pressure pipelines at very low pressures (100 mm water gauge), pneumatic testing is to be avoided, if possible, because of the hazards inherent in containing large volumes of compressed air. However, there may be occasions when hydrostatic testing is not possible and air is the only medium available for applying a test pressure. For pneumatic testing of gas pipelines see 29.3.

29.2 Hydrostatic testing

29.2.1 General. The completed pipeline may be

tested either in one length or in sections; the length of section should be decided by considering:

a) the availability of suitable water;

b) the number of joints to be inspected; and c) the difference in elevation between one part of the pipeline and another.

Where joints are left uncovered until after testing, sufficient material should be backfilled over the centre of each pipe to prevent movement under the test pressure (see clause 27).

29.2.2 Initial procedure. It is prudent to begin

testing any particular pipeline in comparatively short lengths and to increase the length of test section progressively as experience is gained, until lengths of about 1.5 km or more are tested in one section, subject to consideration of the length of trench which it is permissible to leave open in particular circumstances.

Each test section should be properly sealed off, preferably with special stop ends, designed for the safe introduction and disposal of the test water and release of air, which should be secured by adequate temporary anchors.

The thrust on the stop ends should be calculated on the full spigot external diameter and on the anchors designed to resist it.

NOTE It may often be economical to provide a concrete anchor block which has subsequently to be demolished, rather than risk movement of the stop ends during testing. Hydraulic jacks may be inserted between temporary anchors and stop ends to take up any horizontal movement of the temporary anchors.

All permanent anchors (see 26.3) should be in position and, if of concrete, should have developed adequate strength before testing begins. The section under test should be filled with clean, disinfected water, taking care that all air is displaced through vents at high points or by using a pig or a sphere. After filling, the pipeline should be left at working pressure for a period in order to achieve conditions as stable as possible for testing. The length of this period will depend upon many factors, such as movement of the pipeline under pressure, the quantity of air trapped and whether the pipeline has a cement mortar lining which absorbs water. If pressure measurements are not made at the lowest point of the section, an allowance should be made for the static head between the lowest point and the point at measurement to ensure that the maximum pressure is not exceeded at the lowest point.

29.2.3 Test procedure. Site hydrostatic test

pressures should be in accordance with 13.4. The pressure in the pipeline should be raised steadily until the site test pressure is reached in the lowest part of the section. This pressure should be maintained, by pumping if necessary, for a period of 1 h. The pump should then be disconnected and no further water permitted to enter the pipeline for a period of 1 h. At the end of this period, the original pressure should be restored by pumping and the loss measured by drawing off water from the pipeline until the pressure reached at the end of the test is reached again.

The acceptable loss should be clearly specified and the test should be repeated until this is achieved. The generally accepted loss for non-absorbent pipelines such as steel and iron is 0.02 L/mm of nominal bore per kilometre of pipeline per 24 h per bar of pressure applied head (calculated as the average head applied to the section under test). The rate of loss should be plotted graphically to show when absorption is substantially complete.

A more stringent requirement may be necessary for pipelines carrying fluids other than water.

29.2.4 Detection of leaks. If the test is not

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Consideration should be given to leak detection methods such as:

a) visual inspection of pipeline, especially each joint, if not covered by the backfill;

b) aural inspection, using a stethoscope or listening stick in contact with the pipeline; c) use of electronic listening devices including leak noise correlators which detect and amplify the sound of any escaping fluid; actual contact between the probe and the pipe may or may not be essential;

d) use of a bar probe to detect signs of water in the vicinity of joints, if backfilled;

e) introduction of a gas compound into the test water, using a gas detection device to detect the presence of any gas that has escaped through the leak.

Where there is difficulty in locating a fault, the section under test should be subdivided and each part tested separately.

NOTE A pneumatic test with an air pressure not

exceeding 2 bar may be used to detect leaks in pipelines laid in water-logged ground.

29.2.5 Final procedure. After all sections have been

jointed together on completion of section testing, a test should be carried out on the complete pipeline in accordance with 29.2.3. During the test, all work which has not been subject to sectional tests should be inspected.

29.2.6 Disposal of water. It is important to ensure

that proper arrangements are made for the disposal of water from the pipeline after completion of hydrostatic testing and that all consents which may be required from land owners and occupiers, and from river drainage and water authorities have been obtained.

NOTE With some liquids, notably oil and oil products, it may be necessary to provide temporary interceptors to prevent any oil being discharged with the water. In some cases, e.g. heavily chlorinated water, some treatment may be necessary before final disposal.

29.3 Pneumatic testing of gas pipelines

29.3.1 General. A pneumatic test should be carried

out to prove the tightness of joints rather than the strength of the pipeline.

NOTE. The air pressure to be applied will vary according to circumstances.

29.3.2 Safety precautions during pneumatic testing.

Pneumatic testing could in the event of failure, give rise to a serious explosion. During each test, it is

Persons engaged on pneumatic testing operations should remain in a safe place whilst pressure is being raised and during the whole of the time the pressure is maintained. No approach should be made for inspection or any other purpose until the pressure has been reduced to the maximum working pressure.

If these precautions are not possible or if hazards to persons and property are likely to arise during pneumatic testing, then a hydrostatic test should be applied first, in accordance with 29.2.

29.3.3 Test procedure. Reference should be made to

IGE/TD/3 [1]. Ductile iron pipelines for conveying gas should be pneumatically tested at not less than the maximum gas working pressure. The maximum pneumatic pressure applied should not exceed that specified for any particular joint or any other pressure restriction that may be imposed as a result of local conditions or regulations (see 14.3).

29.3.4 Detection of leaks. If the pneumatic test is not

satisfactory the fault should be found and rectified. Consideration should be given to leak detection methods such as:

a) application of soapy water or similar solution around the joints;

b) aural inspection using a stethoscope or listening stick;

c) use of electronic listening device;

d) introduction of halogen gas into the pipeline and use of a suitable detector to indicate the presence of gas outside the pipeline; and e) introduction of a distinctive odorant into the pipeline.

30 Commissioning

30.1 General

The procedure for commissioning a completed pipeline will vary according to whether it has been hydrostatically or pneumatically tested and whether it is to convey a liquid or a gas.

30.2 Liquid pipelines

Pipelines intended to convey liquids are usually tested hydrostatically and, therefore,

commissioning consists of displacing the test water from the line by the liquid to be conveyed. Visible dirt and debris should have been removed either manually or by the use of cleaning pigs before testing (see 26.1 and clause 28). Filling and