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GENERALSPECIFICATION
G1.2 PIPEWORK
CONTENTS
G1.2 PIPEWORK.............................................................................................................................. 3
G1.2.1 General..................................................................................................................... 3
G1.2.2 ReferenceStandards.................................................................................................. 4
G1.2.3 Material,WorkmanshipandWeldingStandards........................................................ 6
G1.2.3.1 HydraulicTestingofPipesatPlaceofManufacture.................................................... 7
G1.2.3.2 ProtectionofSteelPipesinTransit............................................................................ 7
G1.2.3.3 Delivery..................................................................................................................... 7
G1.2.3.4
Storage
......................................................................................................................
8
G1.2.3.5 ExaminationofSteelPipesPriortoInstallation.......................................................... 9
G1.2.3.6 RepairofPipeLiningsandSheathing.......................................................................... 9
G1.2.4 SubmissionsbytheContractor................................................................................. 10
G1.2.4.1 DrawingsandData.................................................................................................. 10
G1.2.4.2 ConsignmentNotes................................................................................................. 10
G1.2.4.3 RecordstobeKept.................................................................................................. 10
G1.2.4.4 TestCertificates....................................................................................................... 11
G1.2.4.5 MethodandProgrammeofPipelineConnections,TestingandCleaning................... 11
G1.2.5 PipeworkMaterials................................................................................................. 11
G1.2.5.1 Introduction............................................................................................................ 11
G
1.2.5.2
Steel
Pipework
........................................................................................................
11
G1.2.5.3 InternallyLinedSteelPipes...................................................................................... 12
G1.2.5.4 DuctileIronPipesandFittings.................................................................................. 13
G1.2.5.5 CastIronSoilPipesandFittings................................................................................ 14
G1.2.5.6 PolyvinylChloride(PVC)Pipes................................................................................. 14
G1.2.5.7 PE100PolyethylenePipes........................................................................................ 15
G1.2.5.8 VitrifiedClayPipes................................................................................................... 15
G1.2.5.9 StainlessSteelPipesandFittings.............................................................................. 15
G1.2.5.10 FibreglassReinforcedPlastic(FRP)Pipes.................................................................. 16
G1.2.6 PipeCutting............................................................................................................. 17
G1.2.7 ClosingLengths........................................................................................................ 17
G1.2.7.1 General................................................................................................................... 17
G1.2.7.2
Steel
Pipes
...............................................................................................................
18
G1.2.8 InternallyLinedFittings........................................................................................... 18
G1.2.8.1 RetainingRingsforInternallining............................................................................ 19
G1.2.9 Jointing.................................................................................................................... 19
G1.2.9.1 General................................................................................................................... 19
G1.2.9.2 InstallationProcedure............................................................................................. 21
G1.2.9.3 SpigotandSocketJoints.......................................................................................... 22
G1.2.9.4 FlangedJoints.......................................................................................................... 22
G1.2.9.5 MechanicalCouplings,FlangeAdaptersandExpansionJoints.................................. 23
G1.2.9.6 Welding................................................................................................................... 25
G1.2.10 AccesstoInteriorofPipelines.................................................................................. 29
G1.2.11 InstallationofUndergroundPipes............................................................................ 29
G1.2.11.1 General................................................................................................................... 29
G1.2.11.2 SteelPipes............................................................................................................... 30
G1.2.11.3 InstallationofPE100PolyethylenePipes.................................................................. 31
G1.2.11.4 InstallationofSolventWeldedThermoplasticsPipes............................................... 31
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G1.2.11.5 InstallationofValves............................................................................................... 31
G1.2.11.6 BeddingtoPipes...................................................................................................... 32
G1.2.12 ProtectionGeneral................................................................................................ 34
G1.2.12.1 CleaningandPriming............................................................................................... 34
G1.2.12.2 ExternalProtection.................................................................................................. 35
G1.2.12.3 ExternalWrapping................................................................................................... 37
G1.2.12.4
Polyethylene
Sleeving
..............................................................................................
38
G1.2.12.5 FusionBondedEpoxyCoating.................................................................................. 38
G1.2.12.6 InternalProtection................................................................................................... 38
G1.2.12.7 ProtectionofPipesandValvesinChambers............................................................. 41
G1.2.12.8 PaintingPipeworkaboveGround............................................................................. 42
G1.2.13 PipeSupports.......................................................................................................... 42
G1.2.13.1 Workmanship.......................................................................................................... 42
G1.2.13.2 Handling.................................................................................................................. 42
G1.2.13.3 PipeSupportsforExposedPipeworkwithinBuildings.............................................. 43
G1.2.14 InspectionandTesting............................................................................................. 45
G1.2.14.1 SpecialistInspectionandTesting.............................................................................. 45
G1.2.14.2 InspectionatTimeofInstallation............................................................................. 46
G1.2.14.3
Inspection
Prior
to
Water
Testing
.............................................................................
46
G1.2.14.4 CleaningPipelines.................................................................................................... 46
G1.2.15 TestingPipelinesGeneral...................................................................................... 47
G1.2.15.1 ProcedureforPressureTesting................................................................................ 48
G1.2.15.2 TestingGravityPipelines.......................................................................................... 51
G1.2.16 FlushingandSterilizationofPipelines...................................................................... 52
G1.2.17 Design,InstallationandBuildinginofPipework....................................................... 53
G1.2.18 WorkinsidePipelines............................................................................................... 53
G1.2.19 DangersofFloatation............................................................................................... 53
G1.2.20 PipelinesintheSameTrench................................................................................... 54
G1.2.21 AnchorandThrustBlocks......................................................................................... 54
G
1.2.22
Pipelines
Built
Into
Structures
..................................................................................
55
G1.2.23 InstallationofPipelinesotherthanBuriedPipelines................................................ 55
G1.2.24 ConnectionsbetweenDifferentPipeMaterials........................................................ 56
G1.2.25 ConnectingtoExistingPipelines............................................................................... 56
G1.2.26 PluggingofDeadEnds.............................................................................................. 57
G1.2.27 CablesSharingPipelineTrenches............................................................................. 57
G1.2.28 MarkerTapeforBuriedServices.............................................................................. 57
G1.2.29 RouteMarkerPosts................................................................................................. 57
G1.2.30 RepairofFusionBondedEpoxyCoatings.................................................................. 58
TABLEG1.2.2:MAXIMUMSPACINGBETWEENPIPESUPPORTSFOREXPOSEDSTEEL,DUCTILE IRON
ANDCOPPERPIPES............................................................................................................................ 45
TABLEG
1.2.3:
MAXIMUM
SPACING
BETWEEN
PIPE
SUPPORTS
FOR
UPVC
PIPES
...............................
45
TABLEG1.2.4:MARKERTAPE............................................................................................................ 57
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G1.2 PIPEWORK
G1.2.1 General(a) The term pipework shall include all necessary supports, saddles, slings,
fixing bolts and foundation bolts required to support the pipes and
associatedequipment.
(b) Pipeworkinbuildingsshallbearrangedanddesignedsoastofacilitatetheerection, painting in situ and dismantling of any section for maintenance
andtogiveaconstantanduniformflowoffluidwithaminimumheadloss.
Where steel pipework is used, the number of flanges shall be kept to a
minimumandthelengthofeachunitofpipeworktakenintoconsideration
theeaseofhandling,installationandgeneralappearanceofthecompleted
pipe system. Positions of flanges shall take into account any necessary
concretepipesupportsorthrustblocks.Flangesshallnotbecastintofloors
orwallsandshallbelocatedsuchthattheycanbereadilydismantled.
(c) Water velocities in the gravity main shall be less than 1m/s. Watervelocitiesinthesuctionbranchofapumpshallnotexceed1.5m/sandthedischargebranchshallnotexceed2.5m/s.
(d) Flexiblejoints/mechanicalcouplingsshallbeprovidedwherenecessarytofacilitate removal of Plant and/or to allow for differential settlement of
building structure. Flexiblejoints/ mechanical couplings shall be provided
with tie bolts or other means to transfer longitudinal thrust along the
pipeworkasawhole.Pipesupportsshallnotbeusedtoabsorbthrust. All
valves, flowmeters, static mixers that cannot easily be removed for
maintenanceshallbeprovidedwithflangeadapterstomaketheirremoval
and replacement easier. Flange adapter may only be omitted with the
approvalof
the
SO.
(e) In general, all pipes and fittings up to and including 100 mm in diametershallbemanufacturedeitherinsteelorinuPVCunlessotherwiseshownon
theDrawingsorrequiredaspartofapackageplant.
(f) Wheresteelandcastflangesarematedtogether,thesteelflangeshallbemachinedoveritsfullfaceafterweldingtoitsrespectivepipeiscompleted.
Wherever possible standard fittings shall be used in preference to
fabricatedorspecialfittings.
(g)
Facilities
shall
be
provided
for
draining
the
pipe
system
and
releasing
air.
Thedrainedfluidshallbepipedtoanapproveddischargepoint.
(h) Wherever possible, heavy equipment such as valves, strainers and otherdevicesmounted inthepipeworkshallbesupported independentlyofthe
pipestowhichtheyconnect.
(i) Unlessotherwisespecified,flangesshallconformtoBSEN1092andshallbedrilled in accordance with the appropriate pressure designation but
generallynotlessthanPN16.
(j) Whereapipepassesthroughareinforcedconcretewall,retainingwallorissubject
to
thrust,
it
shall
incorporate
apuddle
flange,
which
shall
conform
tothedimensionsstatedinBSEN1092butshallremainundrilled.
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(k) Vertical pipework may be supported on duckfoot bends mounted on thecivil structure. When used, duckfoot bends shall be bolted to the civil
structure.
(l) SpecificrequirementsforchemicalpipeworkarespecifiedintherespectivesectionoftheSpecification.
(m) Excavationandrefillingofpipetrenchesshallbecarriedout inaccordancetoSectionsG3andP3oftheSpecification.
(n) Further requirements specific to external protective coatings of pipeworkaregiveninSectionG1.5.
(o) Further requirements specific to pipework and valves for air conditioningandfirefightingsystemsaregiveninSectionG7.0.
G1.2.2 ReferenceStandards
(a) Unless otherwise specified and approved by the S.O., pipelines andpipework shall comply with the relevant Singapore Standards and the
ReferenceStandardslistedbelowwhereapplicable:
Standard Subject
BS65 Specification for Vitrified Clay Pipes, fittings
andDucts
BS437 Cast iron spigot and socket drain pipes and
fittings.
BSEN124 Gully tops and manhole tops for vehicular
andpedestrian
areas.
BS534 Steelpipes,jointsandspecialsforwaterand
sewage.
BSEN295 Vitrified Clay Pipes, Fittings and Pipe Joints
forDrainsandSewers
BS1154 Naturalrubbercompounds
BSEN1982 Copperalloyingotsandcopperalloyandhigh
conductivitycoppercastings.
BSEN1561 Flakegraphitecastiron.
BSEN6811 Elastomeric seals forjoints in pipework and
pipelines.
BS
2633
Class
I
arc
welding
of
ferritic
steel
pipework
BS2971 ClassIIarcweldingofcarbonsteelpipework
BSENISO35061,2,3 Mechanical properties of corrosion resistant
steelfasteners.
BSEN122011,2,3,4 Plastic piping systems for water supply:
Polythene.
BS3416 Bitumenbasedcoatingsforcoldapplication.
BSENISO1452 Plastic piping systems for water supply
unplasticizedpoly(vinylchloride)
BS3506 uPVCpipeforindustrialuses
BS3600 SpecificationforDimensionsandmassesper
unit length of welded and seamless steel
pipesand
tubes
for
pressure
purposes
BSEN102161 Seamless nonalloy steel tubes for pressure
purposes
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BSEN102171 Welded nonalloy steel tubes for pressure
purposes
BSEN10300 Bitumen based hot applied protective
coatings
BS4190 ISO metric black hexagon bolts, screws and
nuts.
BSENISO4320 Metal washers for general engineering
purposes,metricseries.
BSEN10029,BS7668 Weldablestructuralsteels.
BSEN10921,3 Circularflangesforpipes,valvesandfittings:
Steelandcopperalloy.
BSEN15151 Flangesandtheirjoints bolting
BS45151&2 Welding of steel pipelines on land and
offshore
BSEN545 Ductile iron pipes and fittings for water
application.
BSEN598 Ductile iron pipes and fittings for sewage
application.
BSEN
1514
Part
1to
4
Dimensionsof
gaskets
for
pipe
flanges
to
BS
EN1092.
BSEN1171 Castirongatevalves.
BSEN12334 Castironcheckvalvesforgeneralpurposes.
BS5292 Jointingmaterialsandcompounds.
BSEN1796 Glass reinforced plastics (GRP) pipes and
fittingsforuseforwatersupplyorsewerage.
BS5500 Unfiredfusionweldedpressurevessels
BS2782 11 General requirements for dimensions and
pressure ratings for pipe of thermoplastics
materials.
BS5911 Precast concrete pipes, fittings and ancillary
products.
BS6076 Tubular polyethylene film for use as
protectivesleevingforburied ironpipesand
fittings.
BSEN122021,2,3 Blue polyethylene pipes up to nominal size
63forbelowgrounduseforpotablewater.
BS6956 JointingofMaterials
BS7079:Part0 Preparationofsteelsubstrates.
BS8010:Parts1&2 Code of Practice for pipelines: Pipelines on
land
API5L Linepipes
API
5LS
Spiral
welded
line
pipes
API1104 Standard for welding pipelines and related
facilities
ASTMC582 Standard Specification for ContactMolded
Reinforced Thermosetting Plastic (RTP)
LaminatesforCorrosionResistantEquipment
ASTMD2310 Standard Classification for MachineMade
Fiberglass (GlassFiberReinforced
ThermosettingResin)Pipe
ASTMD2996 Standard Specification for FilamentWound
"Fiberglass" (GlassFiberReinforced
ThermosettingResin)Pipe
AWWAM11
Steel
pipe
design
and
installation
AWWAC208 Dimensions for Fabricated Steel Water Pipe
Fittings
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AWWAC213 Fusionbondedepoxycoatingforinteriorand
exteriorofsteelwaterpipelines
WIS*43202 Polyethylene pressure pipe for cold potable
water(undergrounduse).
WIS*43203 Polyethylene pressure pipe for cold potable
water(fornominalsizesgreaterthan63).
WIS*43204 Polyethylenefusionjointsandfittingsforuse
withcoldpotablewaterpressurepipes.
WIS*43206 Polyethylene electrofusion couplers and
fittings
WIS*43208 Fusion jointing of polyethelene pressure
pipeline systems using PE80 and PE100
material
WIS*45201 Polymericanticorrosion(barrier)coatings
WIS*45201A Polymeric anti corrosion (barrier) coatings
amendments
(* WRC (UK) Water Treatment Specifications, previously called
InformationandGuidanceNotes)
(b) Thislistisnotintendedtobeexhaustive.Thesestandardsforequipmentormaterialsprovidedaspartoftheworksmaybeapplicabletotheapproval
oftheS.O.
G1.2.3 Material,WorkmanshipandWeldingStandards(a) All pipes, flanges, fittings supplied shall be supplied with manufacturers
guaranteetoensurethesuitabilityofthesuppliedmaterialfortheintended
use.
(b) Material inspectionbeforerollingshallbecarriedouttocheckagainstMillCertificatessubmitted.Thisshallincludedeterminationofcountryoforigin,
manufacturer, physical inspection, checking of thickness and visual
inspectionofedgesforlamination.
(c) As a control on weld quality, the Contractor shall carry out and submitradiographs for 3% of all butt welds for the S.O.'s clearance. The S.O. will
advise the Contractor where he requires the radiographs to be taken.
Radiographsshallbetakendailywheneverweldingofpipesandspecials is
inprogress.Theclearanceandacceptanceoftheseradiographsshallbe in
accordancewithAPIStandard1104unlessotherwisedirectedbytheS.O.
(d) Weld defects shall include cracks, leaks, laminations, lack of completepenetration, lack of complete fusion, dents exceeding one eighth of the
specifiedwallthicknessandundercuttingorreductioninpipewallthickness
adjacenttoaweldexceeding0.5mmindepth.
(e) Slag inclusions and gas pockets or voids considered to be minorimperfectionsmaybeacceptedifthemaximumsizeanddistributionsdoes
notexceedthelimitsshowninSection9ofAPIStd5LorSection7ofAPIStd
5LS.
(f) Whereradiographicexaminationrevealsdefects inthewelds,theS.O.willeither reject the length of pipe containing such defects or will permit the
Contractortocarryoutrepairsandtosubmitradiographsofsuchrepairsfor
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clearance. Lengths of pipe containing defects in welds after repair will be
liabletoberejected.
(g) Ifdefects inweldsarefound ina lengthofpipeorfitting,theweldsofthepipesandfittingsimmediatelybeforeandafterthedefectivepipeorfitting
intheproductionlineshallberadiographeduntiltheS.O.issatisfiedthatall
the welds are considered satisfactory. The cost of such radiographs and
radiographsofrepairedweldsshallbebornebytheContractorandshallbe
includedintheContractratesandshallnotformpartofthe3%ofallwelds
specifiedinapreviousparagraphofthisClause.
G1.2.3.1 HydraulicTestingofPipesatPlaceofManufacture(a) All pipes shall be hydraulically tested at the place of manufacture in
accordance with Section 5 of API Standard 5L or API Standard 5LS as
appropriate. Full test pressures shall be maintained for at least 3 minutes
during
testing
at
the
factory
and
automatic
pressure
recorders
must
beinstalledonhydraulictestingmachines.
(b) Any pipe which fails to withstand the hydraulic test pressure or whichexhibits signs of porosity shall be deemed not to comply with this
SpecificationandshallberejectedunlessotherwisedecidedbytheS.O.
(c) Unless otherwise specified, physical testing of the pipes shall also be inaccordance with Section 4 of API Standard 5L or API Standard 5LS as
appropriate.
(d) Allthepipessuppliedshallbetestedfortheintendedoperatingconditions,pressure/
vacuum,
at
the
manufacturers
place
and
acertificate
stating
the
suitabilityshouldbeissued.
G1.2.3.2 ProtectionofSteelPipesinTransit(a) Allsteelpipesshallbeprotectedpriortodespatchfromthemanufacturer's
works. All flanges shall have wooden discs bolted on. All other ends of
pipes and fittings shall be protected against impact damage and entry of
foreignmatter. Theprotectionshalltakeintoaccounttheenduseintended
for
the
pipes
and
whether
or
not
the
final
protection
has
been
completed.
(b) Pipes and fittings shall be wrapped or cushioned so that no load is takendirectlyontheexternalcoating.
G1.2.3.3 Delivery(a) TheContractorshallsubmittotheS.O.advancenoticesofallconsignments
of steel pipes. Every consignment shall be accompanied by a detailed
deliverynotewiththeitemnumberofeachpipeorfitting.
(b) TheContractorshalltakedeliveryofandoffloadpipes,valves,andprecastmanholesectionswhichheisrequiredtoprovide,attimesandatlocations
or storageareas on or about the Site to be arranged by him with his
suppliers,subjecttotheapprovaloftheS.O.. Anysuchlocationorstorage
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area which does not form part of the Site shall be arranged for by the
Contractorathisownriskandexpense.
(c) After pipes, valves and precast manhole sections have been delivered toandoffloadedatdeliverylocationsasaforesaid,theContractorshallmake
all arrangements for subsequent transport and handling on or about the
Sitetothepointof installation, includingwherenecessary,anymovement
intoandoutoftemporarystorage.
(d) TheContractorshall inspectallpipes,valvesandprecastmanholesectionsupondeliveryfromthemanufacturerandshallnotealldamaged,brokenor
otherwiseunsatisfactoryitemsandshalltakeimmediatestepstorectifyor
replace such broken or damaged or unsatisfactory items. Items with
damagedfusionbondedepoxycoatingsshallbetreatedinaccordancewith
therequirementsofSectionG1.5oftheSpecification.
G1.2.3.4 Storage
(a) TheContractorshalltakeintotemporaryprotectivestorageallpipes,valvesandprecastmanholesectionsnotrequiredforimmediateinstallationinthe
Works or, inthecaseofpipesand precast manholesections, for stringing
outalongthepipelineroute.
(b) Valves shall be stored under cover until they are required for installationand particular care shall be taken for the protection of any associated
electricalormechanicalequipment.
(c) TheContractorshallpreparepipestorageyardsatlocation(s)asdirectedbythe
S.O.
on
Site
at
which
the
steel
pipes
and
fittings
shall
be
delivered.
The
areasshallbeclearofvegetationand levelledoffandtheContractorshall
constructandmaintainadequatetemporaryaccesstothestorageyard(s).
(d) TheContractorshallprovideatnoextracosttotheEmployer,timberpiecestokeepallstoredpipes,clearoftheground. TheContractorshallmaintain
thestorageyardsinaconditionsatisfactorytotheS.O.untilcompletionof
theWorks.
(e) Pipesinstorageshallbelaidonwedgedtimberbearerssoastobeatleast75mm clearof the ground;steel pipes shall be stacked in one layer only,
other
pipes
may
be
stacked
up
to
three
pipes
high,
if
suitable
protective
packingisplacedbetweenthelayers. Topreventdamagetothesheathing
ofpipeswhicharesheathedwithbitumenthebearersshallbepositionedat
theunsheathedendsofthepipes.
(f) The period between taking delivery of a pipe and the completion of itsinstallationshallbekeptto aminimum and in thecase of steelpipesthis
periodshallnotexceedsixmonths. Anyperiodduringwhichthepipesare
strungoutalongthepipelinerouteorplacedalongsidetheWorksawaiting
installation shall also be kept to a minimum. Jointing parts and materials
shallinanycasebestoredundercoverasforvalves.
(g) Subject to the foregoing and to any restrictions of the duration oftemporary occupation of parts of the Site, pipes may be strung out along
the pipeline route prior to installation providing that any necessary
temporaryfencinghasfirstbeenerected.
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G1.2.3.5 ExaminationofSteelPipesPriortoInstallation(a) All pipes and specials shall be thoroughly brushed through, cleaned and
carefullyexaminedforcracksandflaws,bothinternallyandexternallyprior
tolaying. Materialsfoundtobedamagedinanywayshallbeshowntothe
S.O.whowillgiveinstructionsregardingremedialworkorotherwise.
(b) Whereendstobejointedbyweldingaretobecoatedwithensisoilattheplaceofmanufacture.Theendsshallbethoroughlycleanedwiththeensis
oilremovalpriortowelding.
(c) The ends of pipes and specials shall be wire brushed if necessary andthoroughlycleanedtoremovealltracesofrustanddirt.
(d) Should any pipe or specials be found to be damaged, it shall be excludedfromtheworkuntilrepairshavebeencarriedouttothesatisfactionofthe
S.O. Ingeneral,nopipeshallbe laid ifanendhassuffereddistortionfrom
the circular and a mechanical coupling or socket cannot be fitted or, if
damage
to
the
internal
and/or
external
protection
has
not
beensatisfactorilyrepaired.
G1.2.3.6 RepairofPipeLiningsandSheathing(a) Only specially competent and skilled men shall be employed to carry out
repairworktodamagedliningsandsheathing.
(b) Small cracks and flaws in the internal mortar lining of steel pipes andspecialsmay,withthepriorapprovaloftheS.O.andiftheyareaccessible,
berepaired
on
Site.
Such
cracks
may
be
repaired
by
cutting
out
a9mm
x9
mmdovetailedkeyandmakinggoodwithasemidrymortar(proportion1
partcementto2partscoarsesand)welltampedintothegroove,andcured
by keeping it damp for 7 days. Alternatively, small cracks may be caulked
withepoxyresinfiller.
(c) The external sheathing of steel pipes and specials shall be made goodwherever the steel has been exposed or the thickness of the coating
seriouslyreducedbydamage,orwherethecoatingdoesnotadheretightly
to the steel. Where the steel has been exposed, all rust and dirt shall be
removedcarefullybywirebrushingorotherwise,andwhenperfectlyclean
and
dry,
a
coat
of
approved
special
quick
drying
primer
applied
before
refettling. Small stones which may have become embedded in the
sheathing shall be picked out and the coating refettled by heating locally
with a blow lamp and smoothing over with a fettling knife. Additional
externaljointingmaterialshallbeaddedwherevernecessary.
(d) All defects to linings and sheathings shall be made good to the entiresatisfactionof the S.O. Where, in S.O.s opinion, the damage is such that
satisfactory repairs on Site will not be practicable, e.g. when damage or
cracking isextensive and/or inaccessible, the pipes or specials in question
shall be either returned to the factory for repairing properly or replaced
completely. TheContractorshallberesponsible ineithercaseforallcosts
involved
in
this
respect
and
for
any
delays
to
construction
work
thereby
caused. The compound used for repairing sheathings shall be compatible
withthesheathingmaterialandshallbeapprovedbytheS.O.
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G1.2.4 SubmissionsbytheContractorG1.2.4.1 DrawingsandData
(a) Submissions which the Contractor is required to make in relation topipelinesinclude,whererelevant,thefollowing:
(i) Typicaldrawingsofstandarditems.(ii) Detaildrawingsofspecialitems.(iii) Manufacturer's calculations, catalogues and data sheets including
pressure/temperatureratingsforpipes,fittingsandjoints.
(iv) Forsteelpipes,drawingswithdescriptionsoutliningthemethodofformingpipesandspecials instandard lengthsfromsteelsheetor
strip.
(v) Welding procedure details including plant, method, number ofruns, weld materials, air testing of joints and names and
qualificationsofwelders.
(vi) Contractor'scalculationsforpipeandfittingdesign(vii) Full details of internal and external protection and lining systemsincludingmethodofapplication,materials,curing,etc.(viii) Evidence of compliance with requirements for materials,
substances and products in contact with water which is to be
suppliedfordrinking.
(ix) Methodofboxingoutforandbuildingpipesintostructurewalls.(x) Methodsofcontroloflineandlevelofpipelineduringinstallation.(xi) Methodsforpipehandling,installationandbackfill(xii) DetailsofContractor'spipesupports
G1.2.4.2 ConsignmentNotes
The Contractor shall forward to the S.O. advanced notices of all consignments.
Everyconsignmentshallbeaccompaniedbyadetaileddeliverynotewiththe item
numberofeachpipeorfitting.
G1.2.4.3 RecordstobeKept(a) TheContractorshallkeepdetailedanduptodaterecords ina formtobe
approved
by
the
S.O.
of
all
pipes
and
valves,
showing
the
quantities
of
each
type,sizeandclasswhichhavebeen
(i) orderedduringthecourseoftheWorks;(ii) deliveredduringthecourseoftheWorks;(iii) declaredondeliverytobefaultydamagedordeficient;(iv) usedintheWorks;(v) brokendamagedorlostduringthecourseoftheWorks.
(b) EachweektheContractorshallprovidetheS.O.withanuptodatecopyofthe above records. In the case of steel pipes, the Contractor shall also
recordtheBillofQuantitiesitemwise.
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G1.2.4.4 TestCertificates(a) TheContractorshallforwardtotheS.O.beforedespatch,certificatesfromthe
manufacturerstoshowthatpipesandvalveshavebeentestedandcomplywith
theappropriateStandard(s).
(b) The Contractor shall forward to the S.O. copies of the certificates of all weldtestscarriedoutonsteelpipework.
G1.2.4.5 MethodandProgrammeofPipelineConnections,TestingandCleaning(a) The Contractor shall submit for the approval of the S.O., details of his
proposed methods and programme for pipeline connections to existing
pipelines,testing,swabbing,disinfectionandcleaning(includingdetailsoftest
andcleaningequipment).
G1.2.5 PipeworkMaterialsG1.2.5.1 Introduction
(a) ThisSectionisspecifictothematerialrequirementsforpipework.(b) Pipework shall be manufactured to the specification given hereunder and
shall be provided by the Contractor except as specified otherwise. The
particulartype,sizeandclassofpipesandvalvesforeachpartoftheWorks
shall
be
as
specified
or
as
described
on
the
Drawings
or
in
the
Bills
of
Quantities.
G1.2.5.2 SteelPipework(a) Pipes shall be specified by nominal diameters inaccordancewith BS 3600
Table1.
(b) CarbonsteelpipesshallbeinaccordancewithBSEN10216orBSEN10117asapplicable.
(c) CarbonsteelfittingsshallcomplywithBSEN10253 1.(d) WeldingshallbecarriedoutinaccordancewithBS2633Class1arcwelding.
Allweldersshallbetestedbyanindependentinspectionauthorityandshall
satisfy the requirements of BS EN 287 1. Current and valid welder test
certificates shall be provided by the Contractor for approval by the S.O.
priortocommencementofsitewelding.TheS.O.mayrejectanyproposed
welder on the basis of incompetence at any time during the
implementationoftheWorks.
(e) Steel pipework fittings shall be fabricated in accordance with BS 534.WheredimensionsfortherequiredfittingsarenotgiveninBS534,AWWAStandardC208for"dimensionsoffabricatedsteelwaterpipefittings"shall
beused.
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(f) All fabrication and corrosion protection shall be carried out at themanufacturer'sworks. LiningsandcoatingsshallcomplywithSectionG1.5
ofthisSpecification.
G1.2.5.3 InternallyLinedSteelPipes(a) Steel pipes shall be manufactured, except where stated otherwise
hereunder,inaccordancewithAPISpecification5LorAPISpecification5LS.
MaterialforpipesshallbecarbonsteelplatetoGrade43AofBSEN10029
or better with a minimum lower yield stress of 275 N/mm2
for plate
thickness up to 16 mm and 265 N/mm2 for plate thickness greater than
16mmandupto40mm,andshallbesupplied in plateor strip formas of
appropriateforthemethodofpipemanufacture.Thepipesshallbeformed
bytheautomaticsubmergedarcprocess,witheitheralongitudinalseamor
a spiral seam at the option of the Contractor. With the method of
manufacture decided upon, the relevant standard will then apply i.e. API
Specification5L
for
longitudinal
seam
pipe
or
API
Specification
5LS
for
spiral
seampipe.TheAPIstandardsshallbereferredtohereunderasStd5L/Sand
shall be deemed to apply to all pipe sizes, including those whose outside
diameter(OD)fallsoutsidetheupperlimitcoveredbythestandards.
(b) TheContractorshallprovidealadleanalysisofthesteelusedforthepipesin accordance with Clause 7.1 of BS 4360:1986. Check analyses of the
finishedpipeshallbetakeninaccordancewithClause7.2ofBS4360:1986
and Clause 3.4 of Std 5L/S. In case of dispute, the methods of chemical
analysisshallbeinaccordancewithBSHandbookNo.19.
(c) Unless otherwise specified, thickness of the steel plates and the finishedoutside
diameters
of
the
pipes
shall
be
as
shown
in
the
following
table:
Table1.2.1:SteelPlatesThicknessandFinishedOutsideDiametersofPipes
NominalSize
(mm)
*Thicknessof
steelplate(mm)
Thicknessof
concretelining
(mm)
Outside
diameterof
pipe(mm)
2200
2000
1900
1800
1700
16001500
1400
1300
1200
1100
1000
900
800
750
700
600
500
450
400
300
15.9
15.9
15.9
12.7
12.7
12.712.7
12.7
12.7
12.7
12.7
12.7
9.5
8.0
8.0
6.0
6.0
6.0
6.0
6.0
6.0
25
25
25
25
25
2525
25
25
19
19
19
19
19
19
13
13
13
13
13
10
2216.2
2020
1911.3
1746.3
1720
1549.41520
1422.4
1320
1244.6
1120
1016
933.5
825.9
762
667.2
610
506.9
457
406.4
326.0
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NominalSize
(mm)
*Thicknessof
steelplate(mm)
Thicknessof
concretelining
(mm)
Outside
diameterof
pipe(mm)
250
200
150
100
6.0
6.0
6.0
6.0
10
10
6
6
273
222.0
170.0
118.0
* The above thickness of steel plates shall not be subject to any
negativetoleranceforacceptancepurpose.
(d) Thethicknessofpipesused forbranchpipeworkoffthemainpipelinesorforuseinformingfittingsshallbethegreatestofthefollowing:
(i) The thickness necessary to provide the same outside diameter towallthicknessratiospecifiedforstraightpipes;
(ii) TheminimumthicknessshowninTable6.2ofStd5LorTable6.1ofStd 5LS for pipes of the appropriate diameter (or the nearest
equivalenttherein);
(iii) Thethicknessdeterminedtobenecessary inthedesignoffittingsasshownontheDrawings.
(e) Standard length straight pipes shall be manufactured with not more thanthreecircumferentialjointsandwithaneffectivelengthasshownbelow:
Finishedinternaldia(mm) StandardLength(m)
2100to2250 9
450to2050 10
Below450 6
(f) The allowable tolerance on standard length pipes shall be 150 mm. Inaddition a number of straight pipes of half the standard length pipes and
trulycircularstandardstraightpipesshallbesupplied.Allstandardandhalf
lengthpipesshallhaveendsformedasspecifiedbelowforjointscapableof
angularrotation.Trulycircularstandardstraightpipesrequired forcutting
purposesshallbetrulycircularthroughoutthelength.
(g) Allpipeswhethermanufacturedwitha longitudinalorspiralseamshallbesubjectedtonondestructivetestingofseamweldsandskelpandwelds in
accordancewithSection9ofStd5LorSection7ofStd5LSasappropriate.
G1.2.5.4 DuctileIronPipesandFittings(a) PipeworkandfittingsshallcomplywithBSEN545forwaterserviceandBS
EN598forsewageapplication.
(b) Flangesshallbeeithercastorwelded,orscrewedondependentupontheclass designation of pipe required. Flanges shall be Type PN16 unless
otherwisestated.
(c) Except where indicated otherwise, all socket and spigot pipes and fittingsandflangedpipesandfittingsshallbetothestandardclassdesignation(K9,
K12andK14).
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(d) PipeworkshallbehydrostaticallytestedtoBSEN545andBSEN598andamanufacturer'scertificatesubmittedtotheS.O.
G1.2.5.5 CastIronSoilPipesandFittings(a) For socketless cast iron piping systems, the pipe and fittings shall be in
accordance with BS EN 877. Thejoints shall be heavy duty coupling, with
neoprene sealing sleeve, 304 stainless steel shield, and stainless steel
clamping bands, or boltedcast iron coupling withstainlesssteelbolts and
neoprenegasket. Couplingsshallbeclampedtype.
(b) Unless otherwise specified, socketless cast iron piping systems shall beappliedtobuildingsanitarydrainpiping,wastepiping,ventpiping,building
storm drain piping, and clear water waste piping at all locations except
whereburied.
(c)
Supports
shall
be
provided
at
every
hub
and
change
of
direction
of
pipe.
(d) Forsocketandspigotcastironpipingsystems,thepipeandfittingsshallbeinaccordancewithBS416:Part1.Thejointsshallberubbergasketed,push
ongasketsconformingtoBS416:Part1.
(e) Unlessotherwisespecified,socketandspigotcastironpipingsystemsshallbe applied to building sanitary drain piping, waste piping, vent piping,
buildingstormdrainpiping,andclearwaterwastepipingatalllocations.
G1.2.5.6 PolyvinylChloride(PVC)Pipes
(a) cPVCpipeworkforwaterserviceshallcomplywiththerelevantlatestASTMstandards. Piping shall comply with ASTM D1784 and ASTM F441. Fittings
shall comply with ASTM F439 for socketweld type and ASTM F437 for
threadedtype.JointsshallbesolventsocketweldedtoASTMF493,except
forconnectionstovalvesandequipment where futuredisassemblingmay
berequired.FlangesshallcomplywithBSEN1092PN16.Boltingandnuts
shallbeaccordingtoBSENISO3506.Teflontapeshallbeusedforthreaded
connection.
(b) UnplasticisedPVCpipes,jointsandfittingsfordrainsshallcomplywiththerelevant
provisions
of
BS
4660
or
BS
EN
1401
1.
(c) Unplasticised PVC pipes used as cable ducts shall comply with BS3506ClassE.
(d) Solvent cements forjointing unplasticised PVC pipes shall comply with BSENISO1452.ForpipesandfittingscomplyingwithBS4660,solventcement
mayalternativelycomplywithBS6209.
(e) All uPVC pipes for sewerage purposes shall comply with BS3506 andBS2782 11,andshallhaveaminimumsustainedpressureratingof12bar.
(f) ScrewedconnectionstometalcomponentsshallbemadewithproprietaryirontouPVCadaptorfittings.
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(g) Where flangedjoints are required, full face uPVC flanges and galvanisedmildsteelbackingringsshallbeused.
(h) WhereuPVCpipeworksystemsconnecttosteelmains,theofftakepointsshallbe isolatedbymeansofgatevalvestoBSEN1171orBS5163.Other
valvesinuPVCpipeworksystemsshallbeasspecifiedunderSectionG1.3or
as specifically approved by the S.O with regard to function, location and
operatingconditions.
(i) Pipework shall be supported in accordance with manufacturer'srecommendations and adequate provisions shall be made for thermal
expansionandcontraction.
G1.2.5.7 PE100PolyethylenePipes(a) PE100 polyethylene pipes and fittings for pressure pipelines shall be in
accordance
with
specifications
issued
by
WRC
as
Water
IndustrySpecifications(previouslycalled InformationandGuidanceNotes)43202,
43203 and43204. Themanufacturer shall beresponsible for all testing
andqualityassuranceproceduresandbecoveredbyathirdpartycertificate
scheme all in accordance with these standards. Pipes exceeding 90 mm
nominaldiametershallnotbesuppliedincoils.Pipesuptonominalsize63
shallfurthercomplywithBSEN122022.
(b) The Contractor shall ensure that all PE100 polyethelene pipes and fittingsforthermalfusionjointingtoformanindividualpipelineorpipelinesystems
shallbesuppliedbyonemanufacturer,unlesstheS.O.approvesotherwise.
Electrofusioncouplingsareexemptedfromtherequirementbutmustbeof
atype
approved
by
S.O.
and
shall
incorporate
pins
which
pop
up
to
confirm
thatoptimummeltpressurehasbeenachieved.
(c) Mechanicaljointsshallbecompletewithliners.
G1.2.5.8 VitrifiedClayPipes(a) Vitrified clay pipes and pipeline fittings shall comply with the relevant
provisionsofBS65orBSEN295
(b) Vitrifiedclaypipesshallbeofnormaltypewithflexiblemechanicaljoints.
G1.2.5.9 StainlessSteelPipesandFittings(a) StainlesssteelpipesandfittingsshallgenerallybeSS316Linaccordancewith
ASTM standards. The grades of pipes to be used shall be selected to suit
mediahandledandpressuresencounteredintheapplication.TheContractor
is
responsible
for
proposing
suitable
grades
for
the
consideration
of
the
Employer.Alltheproposedfittingsshallalsobeofthesamematerialasthe
pipes. Special care shall be taken whilejoining different grades of stainless
steelmaterials.Theweldingelectrodesandproceduresshallbesubmittedto
theS.Oforapprovalpriortocommencementofwelding.
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(b) For welding of stainless steel pipes and fittings, appropriate electrodes andqualifiedweldersshallbeused.
(c) The manufacturerof the pipesand fittings shall bewellexperienced in thisfieldandshouldhavemanufacturedpipessimilarinsizesandpressureratings
forsimilarapplicationas inthisplant.TheContractorshallprovideproofof
thisalongwiththetender.
(d) The manufacturer shall be responsible for all testing and quality assuranceprocedures and be covered by a third party certificate scheme all in
accordancewiththesestandards.
(e) Where thin walled stainless steel pipe and fittings are used, prefabricatedpipe spools including all welded fittings shall be pickled and passivated
beforeshippingtoworkslocation.Flangedconnectionsshallbeprovidedat
pipespoolswherepassivatingofinteriorandexteriorfieldbuttweldsisnot
possibleduetopipesizeorotherphysicalrestraints.
G1.2.5.10 FibreglassReinforcedPlastic(FRP)PipesItem Size Description
Pipe AllSizes Fibreglassreinforcedplastic,helicallywound,
conformingtoASTMD2310Type1,vinylester
resin,TypeCglassmonofilamentsurfacingmat
and/orDynelorganicfibresyntheticsurfacing
veilorapprovedequal.Constructedin
conformancewithASTMD2996.
UVProtection:Addtothewaxcoat.
Fabrication AllSizes Interiorsurfacingveilshallbe250to
500micronsthick.Matlayersshallberesinrich,
fullywetted,1.3mmminimumthickness.
Onelayerveilandtwomatlayersbelland
spigot,buttandwrapandflanged.
Ratings Fibreglassreinforcedpipe,fittings,andflanges
shallberated690kPaasspecifiedinASTM
D2310.
Minimumcontinuous
strand
glass
filament
(coatedwithresin)wallthicknessforpipeareas
follows:
50to150mm
200mm
250mmto
300mm
350mm
400mmto
450mm
500mm
600mm
4.75mm
6.35mm
7.95mm
9.50mm
11.10mm
12.70mm
14.30mm
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Item Size Description
Joints 50mmto400mm
Greaterthan
400mm
Adhesivebondedtaperedbellandspigot.Butt
andwrap.
Flangedatvalvesandequipment.
Fittings Allsizes Fittings:ASTMC582andD2996.Surfaceveiland
matlayers
same
as
specified
above
under
Ratings.
Bendsshallbelongradius.
Structuralbodyoffittingsshallbefilament
woundorbuiltupwithalternatelayersof
wovenrovingandchoppedstandmat.Filament
woundfittingsshallbesamethicknessas
specifiedaboveunderFabrication.
Flanges AllSizes Fibreglassreinforcedplastic,flatfacedand
drilledBSEN10921PN16.
Bolting
Boltingmaterial
shall
be
A4
70
per
BS
EN
ISO3506.
NutmaterialshallbeA270perBSENISO3506.
Washershallbesamematerialasbolt.
Gaskets FlatFaceFlanges:Ethylenepropylenerubber
(EPR),3mmthick,fullfaced.
Colour Addpigmenttothefinallayeronlyofexterior
surfacingresintolightlytintthesurface,butnot
obliteratelaminatequality.Coloursareas
follows:
Green
G1.2.6 PipeCuttingWhere it is necessary to cut pipes to provide closing lengths or for laying pipe
specialsorintherepairofdamagedorchippedpipes,thecuttingshallbeneatlyand
accuratelyperformedsoasto leavetheendofthepipetrulynormaltotheaxisof
thepipe.
G1.2.7 ClosingLengthsG1.2.7.1 General
(a) The use of closing lengths shall be avoided by laying the pipes in acontinuous length. Pipes which are required to be cut to form closing
pieces inanyportionofthepipelineortoterminate inmanholesorother
partsoftheWorksshallnotbecutuntilafteralladjacentpipeshavebeen
installedand
jointed.
Pipes
for
closing
lengths
shall
be
cut
to
allow
a20
mm
gapbetweenadjacentpipeends.
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(b) TheContractorshalldeterminethelengthofeachclosingpieceandtheendof the pipe shaped up and trimmed so as to ensure an accuratejoint or
terminationasthecasemaybe.Anydamagetosheathingcoatingorlining
shallbemadegood.
(c) Pipes terminating in manholes and the like shall except where otherwisespecified be cut so that the end of the pipe is flush with the face of the
structureintowhichitisbuilt.
(d) The closing joints in pressure pipelines shall be made with detachableflexiblecouplingswithlocatingplugs.
(e) TheContractormayarrangeathisownriskforcutstobeperformedbythepipesupplier.
G1.2.7.2 SteelPipesWhereclosinglengthsarerequiredtheContractorshallusethespecial'sized'pipes
forcuttingtotheexactlengthsrequired.Thesesteel'sized'pipesmanufacturedtruly
circular along their full length shall be marked by two longitudinal bends in paint
along each pipe. Closing lengths shall be located as near to access openings as
possiblesoastoenableinternalandexternalweldingatjointstobecarriedout.
G1.2.8 InternallyLinedFittings(a) All bends, tees and other fittings shall be prefabricated and testedby the
pipemanufacturer
in
accordance
with
Section
4of
BS
534.
(b) Fittings shall be formed from completely lined and hydraulically testedstraight pipes as specified unless otherwise approved by the S.O., with
suitable rubber spacers inserted during the lining operation. The coating
and liningonthestraightpipesshallthenbecutbackfromtheendstobe
weldedorcutforasufficientdistancetoensurethatnomaterialwhich is
intendedtoremainpartofthecoating/liningisdamagedoraffectedbythe
weldingorcuttingprocess.
(c) Weldingshallbeofastandardequaltothatspecifiedforstraightpipes.Allbutt
welds
shall
be
subjected
to
a
100%
radiographic
test.
All
fillet
welds
shall be subjected to air tests where appropriate and to 100% magnetic
particletests.
(d) Branchesofteesshallbemadefromthesamematerialasthemainbody.(e) The Contractor shall design and reinforce steel fittings to withstand the
specified pressure test and to enable self support in accordance with the
methods contained in the American Water Works Association (AWWA)
Steel Pipe Design Manual, BS 5500 or by other methods approved by the
S.O.WhenusingtheAWWAM11method,thetestpressureforfittingsshall
beoneandaquartertimesthedesignpressureandwhenusingtheBS5500
method,the
test
pressure
shall
be
the
"standard"
test
pressure
determined
in accordance with Clause 5.8.5 of BS 5500. The design pressure shall be
takenasatleastoneandahalftimesthespecifiedworkingpressureorthe
specifiedpipelinetestpressure,whicheveristhegreater.
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(f) Prior to fabrication of any fitting, the Contractor shall have obtained theS.O.'sapprovalofthecalculations,drawingsandfabricationproceduresfor
thatfitting.
(g) Theoutsidediameterofspecialsshallconformtotheoutsidediametersofthestandardstraightpipes.Theendsofplainendedspecialsshallbetruly
circular and shall conform to the tolerances required for the fitting of
mechanicalcouplingsandflangeadaptors.
(h) Ring girders shall be provided to conform with details shown on theDrawings. They shall be supplied complete with all accessories. Metallic
partsaretobedescaledtosecondqualitystandardinBS7079andpainted
with two pack polyamide cured epoxy zinc phosphate primer with 75
micronsminimumdryfilmthickness.
G1.2.8.1 RetainingRingsforInternalliningAll flanged pipe ends, flanged branches and plain ends for use with mechanical
couplingsorflangeadaptorsshallhavea6mmsteelretainingringweldedintothe
bore of the pipe flush with the end of the pipe after which the ring shall be shot
blastedtoSA2toBS7079followedbyappropriatecoatingSystemasspecifiedin
SectionG1.5.Theradialthicknessoftheringsshallbesimilartothethicknessofthe
concreteliningandshallnotbelessthan6mm.
G1.2.9 JointingG1.2.9.1 General
(a) Pipejoints shall be in accordance with Section 3 of BS 534 as describedbelowwiththeamendmentsstated.
(i) Pipes jointed in the trench or above ground shall have sleevewelded (spigot and socket) joints of the hemispherical type in
accordancewithClause13.6ofBS534unlessotherwiseshown.
(ii) Forchangesinpipegradeordirection,thejointsmayhaveangulardeflections
up
to
5
degrees
provided
that
the
joint
design
is
suitableandwillallowthetoleranceforweldingtobemaintained.
Theminimumoverlapofpipeendsatmaximumdeflectionshallbe
fourtimesthepipethickness
(b) Forspigotandsockettypejointsofthe hemisphericaltype,themaximumangulardeflectionshallbe2degrees.
(i) Buttweldedjointsmaybeusedasanalternativetosleeveweldedjoints for pipes to bejointed outside the trench subject to the
approvaloftheS.O..
(ii) Detachable flexible couplings shall be used where specified orwhereshownontheDrawings.
(iii) FlangejointsshallbeusedwhereshownontheDrawings.
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(iv) Welding collars in accordance with Clause 23 of BS 534 shall beusedforjointingcutpipesorclosinglengthsintrench.
(c) Spigot and socketjoints shall be of the hemispherical sleeve type with aminimum penetration of the formed ends as specified below. Thejoint
designshallprovideforthecontactsurfaceofthespigotendandthesleeve
endtobeformedtothesamesphericalradiuswhichshallnotbelessthan
50%oftheoutsideofthebarrelofthepipeforthehemisphericaltype.
(d) Pipestobeused in conjunction withweldedcollars, mechanicalcouplingsorflangeadaptorsshallbesuppliedwithplainends.
(e) Sleeve weldedjoints shall have external fillet welds on pipes of 710 mmoutsidediameterandunderbutshallhavebothinternallyandexternalfillet
weldsonpipeswithanoutsidediametergreaterthan710mm.
(f) The gap between sleeve and spigot at any weld location for internal andexternal welds on Type 3joints (i.e. hemispherical) shall nowhere exceed
1.5mm
whether
the
joint
is
deflected
or
not
and
the
average
gap
around
thecircumferenceofanyweldshallnotexceed1mm.
(g) The minimum penetration of the spigot into the socket shall not be lessthanfourtimesthepipethicknessandthisoverlapshallbeobtainedatthe
maximumdeflectionof2degrees.Atzerodeflectiontheminimumoverlap
shall be the minimum penetration as specified above increased by such
allowanceasisnecessarytoensurecontactbetweenthespigotandsocket
overthespecifiedmaximumamountofangulardeflectionatthejoint.
(h) Pipeendsofthehemisphericaltypeshallbe formedbyhydraulicpressingusing a full circle die or expanding former capable of forming ends
consistently
to
a
constant
spherical
contact
surface
throughout
the
pipe
productionrun.
(i) Fillet welds shall be strength welds having a throat thickness of not lessthan0.7timesthepipethickness.Buttweldsshallbefullpenetrationwelds
havingathroatthicknessofnotlessthanthepipethickness.
(j) Theinternalsurfaceofsleevesandtheexternalsurfaceofthespigotsshallbegroundsmoothalongthelongitudinalfusionweldsforadistanceof150
mm(measuredalongthepipeaxis)fromtheendofthepipeineachcase.
(k)
The
external
surface
of
the
plain
ended
pipes
intended
for
collar
or
mechanicallycouplingjointsshallbesimilarlyprepared.Plainpipeendsfor
use with mechanical couplingjoints shall conform to the requirements of
themanufacturerofthemechanicaljoint.
(l) For large pipes where man access is possible, welded collars shall beprovided forjointing cut pipes or closure pieces by means of internal and
externalfilletwelding.Theminimumlengthofeachcollarshallbe250mm
and the collar thickness shall be 1.5 mm greater than the equivalent
standardstraightpipethickness.Weldingcollarsmaybeprovidedassingle
split collars with temporary bolts and lugs. Split collar ends shall be
prepared for butt welding in the same manner as plain ends of pipes
prepared for butt welding. Collars shall make close contact around the
circumferencesof
both
pipes
connected
and
the
gap
between
the
ends
of
a
split collar after tightening shall not exceed 3 mm. The tolerances of the
collarshallbesuchthatnowhereshallthegapbetweenthe insidesurface
of the collar and the outside surface of the pipe at fillet weld locations
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exceed the tolerances permitted for spigot and socketjoints. The overlap
ontheweldedcollaroneachpipeshallnotbelessthan75mm.Collarjoints
shallnotberequiredtotakeanydeflection.
(m) Allweldedsleeveandcollarjointsshallbeprovidedwithtwotappedholesspacedat90degreesapartonthecircumference.Theyshallbeofnot less
than6mmdiameterandshallbeprovidedwithmatchingplugstofacilitate
theairpressuretestingoffieldwelds.Thesetappedholesshallbe located
withintheend30mmofthesocketsandshallbeclearedofweldingruns.
(n) EndspreparedforbuttweldingshallbesubjecttomanufacturingtolerancesinaccordancewithTable6.3ofAPIStandard5LorTable6.2ofAPIStandard
5LS.
(o) Plain ends for use with mechanicaljoints or flange adaptorjoints shall betruly circular with a diameter tolerance of 1 mm over a distance of 225
mmfromthepipeends.
(p) Pipes to be used for closing lengths shall be correctly sized over their fulllengthsothataccuratealignmentforsplitcollarjointscanbeobtained.Allsuchpipesshallbeclearlymarked.
(q) ThejointsforuPVC,GRPandPE100polyethelenepipesshallbemadeusingmechanical type or solvent welding or thermofusion techniques. The
method ofjointing shall be to the approval of the S.O. The pipes shall be
laidandjointedstrictly inaccordancewiththemanufacturer's instructions
andshallconformtoCP312.
G1.2.9.2 InstallationProcedure
(a) BeforemakinganyjointtheContractorshallensurethattheinteriorofeachpipeorfittingiscleanandthatitremainsclean.Immediatelybeforestarting
ajoint the Contractor shall clean the end of each pipe to bejointed and
shallpreparetheendsforjointingasnecessary.Allmechanicaljointsshall
be cleaned and have their coating made good before assembly in
accordancewiththecoatingmanufacturer'srecommendations.
(b) The Contractor shall use only the properjointing parts as specified andobtained from the suppliers of pipes or fittings. All joints shall be
assembled and tightened and shall be made only on pipes which comply
dimensionally and have been prepared in accordance with the
manufacturer'sinstructions.Alljointsshallbecapableofpassingthetestfor
individualjointsandforthecompletedpipelineasspecified.
(c) Detachable flexible couplings shall be installed where detailed on theDrawings. Thejointsshallbeassembledandtightened inaccordancewith
the manufacturer's instructions. Where shown on the Drawings,
longitudinal movement of pipesjoined by mechanical couplings shall be
restricted by a steel work harness approved by the S.O. After installation
the harness shall be cleaned and painted with two coats of bituminous
paintbeforewrapping.
(d) WheretheDrawingsshow,ortheS.O.requires,achangeofdirectiontobeachievedbythedeflectionofaflexiblejointofanykind,thedeflectionshall
not exceed 50% of the design value for the size and type of joint as
recommendedbythemanufacturer.
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(e) Boltsforflangedorothermechanicaljointsshallshowtwothreadsclearofthenutaftertightening.
(f) Stainless steel nuts and bolts shall be lubricated before assembly with anantigallinglubricant.Nutsshallbetightenedtothetorquesrecommended
bythejointmanufacturer.Torquesshallnotexceedvalueswherethereisa
riskofgalling.
(g) Aftereachjointhasbeencompleted,anyprotectiveorothercoatingshallbemadegoodandanyliningshallbecompletedasspecifiedordetailedon
the Drawings without delay. Any metaljoint which is not already coated
shallbecleanedandpaintedwithtwocoatsofbituminouspainttoBS3416
(excludingClause10).
G1.2.9.3 SpigotandSocketJoints(a)
In
jointing
iron
spigot
and
socket
pipes
and
specials
with
Tyton
or
Stantyte
typeflexiblejointstheContractorshalltakeaccountofthemanufacturer's
recommendations as to the methods and equipment to be used in
assembling thejoints. In particular the Contractor shall ensure that the
spigot end of the pipe to be jointed is smooth and has been properly
chamfered, that the rubber ring is correctly positioned in the socket and
thatthetwopipesareaccuratelyinline,beforethejointismade. Afterthe
joint has been made the Contractor shall ensure by the use of a suitable
feeler gauge that the rubber ring is evenly seated in its correct final
position. The rubber rings and any recommended lubricant shall be
obtainedonlythroughthepipesupplier.
G1.2.9.4 FlangedJointsG1.2.9.4.1 General
(a) Allflangesshallbeofsteel,weldedtothepipebytheelectricarcprocessorother approved method. They shall conform in all respects with the
requirements of BS EN 1092 or PD 5500 unless otherwise specified. They
shall be of the raised face type and shall be truly faced over their whole
width. Bolt holes shall be drilled off centre lines, truly in line end to end
withthelongitudinalaxis.Allflangesshallberatedfor16bar(PN16)unless
otherwise specified. All flanges shall be adequate to withstand test
pressuresforthefittingstowhichtheyareattached.
(b) Therequirementforboltholestobedrilledoffcentremustalsobetrueforflangesonequipmenttowhichthepipeflangesareconnected.
(c) Allmaterialsrequiredforuseinthemakingofflangedjointsincludingnuts,bolts, washers andjoint gaskets shall be supplied by the Contractor. Joint
gaskets shall be contained within the bolt pitch circle and shall be made
from4.5mmthickrubbertoBS1154ClassY3reinforcedwithtwolayersof
fabricinaccordancewithBS5292.Eachboltshallbesuppliedandinstalled
withanut
and
two
washers
(one
on
either
side
of
the
flanges
to
be
joined)
andeachboltshallbeofsufficientlengthtoshowtwothreadspastthenut
whensoinstalled.
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(d) Test certificates for the flange material shall be provided to the S.O. ThefinishonflangejointsurfacesshallbeinaccordancewithBSEN1092.
(e) BlankflangesshallbedesignedandsuppliedbytheContractor foranendloading equivalent to the rating pressure of the flange. Lifting eyes or
handlesandairreleasecocksshallbeprovidedasnecessary.
(f) Thrustflangesshallbeweldedtotheoutsidesurfaceofpipeworkandshallbedesignedtowithstanda longitudinalforceequaltothe loadingapplied
toablankflangeofequivalentdiameter.
(g) TheContractorshallberesponsible forcheckingandensuringthatmatingflanges are compatible in all cases, includingwhereconnectionsare to be
made to existing pipe flanges and to equipment provide as part of the
Works.
G1.2.9.4.2 Installation
(a) When assembling flangedjoints the rubberjoint ring may be fastened tothe bolts with cotton thread. The use ofjointing paste, adhesive tape or
greasewillnotbepermitted. Theboresofabuttingpipesorfittingsshallbe
concentricwiththejointgasketpositionedcentrally;nojointmaterialisto
beleftprotrudingintothebore.Allnutsshallfirstbetightenedbyhandand
nutsonoppositesidesofthejointcircumferenceshallthenbealternately
andprogressivelytightenedwithaspannersoastoensureevenpressureall
round thejoint. Care shall be taken to see that thejoint rings remain in
positionundistortedwhiletheboltsaretightened. Forprecisetightening,
presettorquewrenchshallbeused.
(b) Flanged joints located in chambers shall be painted with two coats ofbituminous epoxy paint but flanges which will be subsequently buried in
trenchandnotencasedinconcreteshallbecarefullywrappedwith'Denso'
tape as manufactured by Winn and Coales Ltd., or similar approved
material.Whereflangedpipe istobeburied,the pipemanufacturerssafe
workingbendingmomentvaluesshallnottobeexceeded.
G1.2.9.5 MechanicalCouplings,FlangeAdaptersandExpansionJointsG1.2.9.5.1 General
(a) Mechanicalcouplingsforjointingplainendedpipesshallbeofanapprovedmake, capable of maintaining a watertight joint over a range of axial
movement between the pipe ends of at least 80 mm and with up to 3
degreesangulardeflectionbetweenthelongitudinalaxesofthepipes.
(b) Where mechanical couplings are used to take up the settlement instructures,theyshallbeprovidedinpairs.
(c) Flange adapters forjointing plain ended pipes to fittings shall be of anapproved
make
capable
of
maintaining
a
watertightjoint
over
a
range
of
axialmovementofatleast25mmandanangulardeflectionofnotlessthan
oneandahalfdegrees.
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(d) Expansionjoints shall be provided to conform to details as shown on thedrawing.Theyshallbesuppliedcompletewithallaccessories.
(e) Mechanical couplings, flange adapters and expansion joints shall beprovidedwithtierodswherevernecessary.Pipesupportsshallnotbeused
to absorb thrust. Where tie rods are necessary, the rods shall be of the
samediameterastheflangebolts.Flangeadapters,whichrequiretierods,
shallbeofsuitabledimensionstoallowthetierodsnottointerferewiththe
body of the flange adapter. Cutting or grinding of flange adapter to allow
installationoftierodsshallnotbecarriedout.
(f) Allnecessarycouplers,jointrings,nuts,boltsandwashers,etc.requiredforcompletingjoints shall be supplied by the Contractor. All bolts, nuts and
washershallbehotdipgalvanisedinaccordancewithBSENISO1461.
(g) Couplings shall be supplied with or without a central register or locatingplugs as required. The central collar shall be at least 1.5 mm thicker than
theequivalentstandardpipethickness.
(h) Every coupling, flange adapter and expansion joint shall be capable ofwithstandingwithoutleakagethepressurerequiredfortheworkshydraulic
testofthesectionofpipelineinwhichitwillbeincorporated.Thepressure
rating shall be clearly stamped on all couplings and adapters. The rubber
jointringsshallbeType1toBSEN6811havingahardnessrangeof4565
degrees measured in accordance with BS 903 and tensile stressstrain
propertiesdetailedinTable3correspondingtotherelevanthardness.
(i) AllmetallicpartsaretobeshotblastedtoSA2toBS7079andprotectedwithtwocoatsofapprovedtwopackepoxybasedcoatingunlessotherwise
stated. Theenamelshallbetaintfree,nontoxicandchlorineresistant.
(j) Allweldingprotrusionshallbemachinefinished.Mechanicalcouplingsandflangeadaptorsshallbehydraulictestedattheplaceofmanufactureonein
everyfiveforeachsizeofcouplingandadaptor.
(k) Everyexpansionjointshallbehydraulictestedattheplaceofmanufacturepriortodelivery.
G1.2.9.5.2 InstallationofFlexibleMechanicalCouplingsforIronorSteelPipes(a) Mechanical couplings and flange adaptorsjoints shall be installed in strict
accordance with the instructions given by the manufacturer and to the
S.O.'s approval. In particular the Contractor shall render the end of each
pipe perfectly smooth so as to allow thejoint sleeve to slide freely and
wherenecessaryshallrecoatthepipeendswithtwocoatsofquickdrying
bituminoussolution.
(b) Beforejointing,theendsofeachpipeshallbewirebrushedtoremoveanyprotective material adhering to the coating, together with any
protuberances which may have been caused by rubbing of the packing
materialandalsoberemovedallrustatexposedplacesduetostrippingof
thebitumastic
coating.
The
ends
shall
then
be
recoated
with
aquick
drying
solutionsoastoproduceasmoothcoatofuniformthickness.
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(c) Oncompletionofthejointthesurfacesofthecouplingandadaptorshallbepaintedwithaquickdryingprimerandanexternalsheathingmouldformed
toenclosethecouplingandendsoftheadjoiningpipes. Thisworkshallbe
carriedoutbyspeciallycompetentandskilledmeninstrictaccordancewith
theinstructionsgivenbythemanufacturer.
(d) Theprimerandsheathingmaterialcompatibletothesheathingmaterialonthepipesandthemouldboxesandfunnelsrequiredtoformtheprotective
mouldandwhitingusedforliningthemouldboxespriortoeachpourshall
besuppliedbytheContractor,whoshallalsosupplythenecessaryboilers
to heat the sheathing material to the application temperature. The
ContractRatesformakingcouplingandadaptorjointsshallcoverallcostsin
complyingfullywiththerequirementsofthisClause.
(e) Mechanical couplings and flange adaptors located in chambers shall bepainted with two coats of approved bituminous epoxy enamel unless
otherwisespecified.
G1.2.9.5.3 GasketsforFlexibleJoints(a) Gaskets forjoints shall be obtained from the manufacturer of the pipe or
joint.
(b) Jointgaskets shall complywiththe relevant requirements ofBSEN6811,shallbeofamaterialsuitableformakingalongtermflexiblesealbetween
the pipes and shall be resistant tomechanical, chemical or bacteriological
attack leading to deterioration of the flexible seal. Joint gaskets shall be
entirelycompatiblewiththemediabeingconveyedbythepipeline.
(c) Lubricantsusedduringjointingshallhavenodeleteriouseffectsonthejointrings,pipesorpipecoating.
G1.2.9.6 WeldingG1.2.9.6.1 General
(a) Wherethesteelpipesaretobejointedbywelding itshallbebymeansofan
internal
and
an
external
circumferential
electric
arc
weld
at
each
joint.
(b) Welded joints in trench shall generally be of the parallel short sleeve,spherical spigot and socket type with a circumferential full strength fillet
weld both internally and externally. Welding gap tolerances shall be as
specified. Full strength fillet welds shall have a throat thickness not less
than0.7timesthethicknessofthepipetobewelded.
(c) Whereprejointingofstraightrunsofpipeoutsidethetrench ispermittedby the S.O., full penetration butt welds executed by manual or automatic
procedures to the approval of the S.O. may beadopted. Butt welds shall
haveathroatthicknessnotlessthanthethicknessofthepipewall. During
welding,
the
pipe
ends
shall
be
securely
held
by
an
approved
method
ensuringacorrectanduniformrootgap.
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(d) Beforeplacingthepipestogethertheportionofthesocketsandspigotstobeweldedshallbecleanedtoabrightmetallic finish,thespigotendshall
thenbeplacedinthesocketandforcedinsidesothatthesphericalsurfaces
areincontactandthatthegapbetweenthepipesattheendofthespigotis
nowhere greater than 1.5 mm. For longitudinally welded pipes, the
longitudinalweldsonadjacentpipesshallbeatleast15ooutofline. Details
ofthesocketandspigotweldedjointareshownontheDrawings.
(e) Wherepipes aretobejointedbyaweldedcollarjoint,thepipeendsandthecollarshallbecleanedtoabrightmetallicfinish. Thecollarshallthen
beplacedcentrallyoverthetwoendstobejointedsothatthegapbetween
thepipeendsshallbeabout25mmfromthecentrelineofthecollar. The
endofeachpipeshallbeweldedtothesleevecollarusingcircumferential
fullstrengthfilletweldsbothinternallyandexternally. Whereasplitcollar
is used, the two halves shall be drawn together by tie bolts until the gap
betweenthemislessthan3mm. Thefourcircumferentialweldsshallthen
be made, after which the tie bolts shall be removed and the longitudinal
seambetweenthecollarpieceswelded. Thetieboltlugsshallthenbecut
offand
the
attachment
points
smoothed
before
the
welds
are
tested.
(f) All parts to be welded shall have scale, slag, loose rust, paint and otherforeignmatter removedbymeans ofa mechanicalbrush andshall be left
clean and dry immediately before welding. All scale and slag shall be
removedfromeachweldrunwhenitiscompletedbeforeweldingoverany
previouslydepositedweldmetalandpriortoairtesting.
(g) AllweldsshallbesubjecttoinspectionbytheS.O.andshallcomplywiththerequirements of Clauses 9 and 11 of BS EN 1011 for freedom from
undercutting,fusionpenetrationandsoundness.
(h) After completion of welding at eachjoint, magnetic crack detection testsshall be carried out on all fillet welds made and 100% radiographic
examinationcarriedoutonallbuttweldsmade. TheContractorshallmake
allthenecessaryarrangementapparatusandequipmentandaspecialistto
carryoutthetest.AllsuchtestsshallbecarriedoutbytheContractorinthe
presenceoftheS.O.Wherebuttjointsarebeingweldedmechanically,the
S.O. may permit the proportion of weld radiographically examined to be
reducedto20% ifandwhenandas longashe issatisfiedwiththeresults
being obtained. The standard of acceptability of welds shall be in
accordance with API 1104 Section 6. Where necessary, welds shall be
repairedinaccordancewithSection10ofAPI5L. Weldrepairsshallnotbe
made
more
than
once
at
any
position
on
the
joint.
(i) TheanalyticaltestreportsinduplicateshallbesubmittedtotheS.O.threedays after the test. Therepaired weldsshallberadiographedagain atno
extracosttotheEmployer.
G1.2.9.6.2 WeldingProcedure(a) Weldingofjoints intrenchforsteelpipesshallbecarriedoutmanuallyby
the metalarc process complying generally with the requirements of BS
4515.
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(b) Before starting the welding of pipe joints on Site, The Contractor shallsubmit fortheS.O.'s approval details of the plant, methods andmaterials
heproposestouse,includingthefollowingdetails:
(i) Make,typeandgaugeofelectrodes(ii) Size,shapeandnumberofrunsinweldedjoint(iii) Directionofwelding(iv) Currentstrength(v) Arrangementsforairtesting(vi) Welderscertificates.
(c) The Contractor shall make test specimens on pipes of the same size andthicknessesasthepipelinestobewelded. Thesepipesshallbesuppliedby
the Contractor. Thejoints shall be tested in the presence of the S.O. for
eachprocedureproposed inaccordancewiththerequirementsofClause7
ofBS4515.
(d) Only procedures approved in writing by the S.O. shall be adopted in thewelding
of
the
pipelines,
and
change
from
one
procedure
to
another
will
notbepermittedwithoutsubmittingthenewprocedureforretesting.
G1.2.9.6.3 WeldersandWelderPerformanceTests(a) OnlythemosthighlyskilledweldersshallbeemployedontheWorks,and
everywelderbeforecommencinganyjointweldingshallpreparespecimens
for testing in accordance with Clause 7 of BS 4515 for each welding
procedure proposed by the Contractor. Every welder shall be tested in
accordancetoClause8ofBS4515. TheContractorshallberesponsiblefor
thepreparation,
setting
up,
provision
of
specimen,
all
necessary
equipment
andmaterialsforthetestingofweldingpersonnel.
(b) The S.O. will advise the Contractor in writing which welders pass theperformance qualification test. Welding shall be carried out only by
weldersapprovedbytheS.O.andeachweldershall identifyhisownwork
bymeansofastencilledmark.
(c) TheContractorshallmaintainanuptodatelistofweldersapprovedbytheS.O.and,iforderedbytheS.O.,heshallremovefromtheapprovedlistany
welderwhoseworkmanship,asdemonstratedbytheresultsofairpressure
and/or
other
tests
and
visual
inspection
of
individual
welded
joints,
is
in
the
S.O.'sopinionbelowtherequiredstandard.
G1.2.9.6.4 AirTestingofWeldedJoints(a) Aftereachjointhasbeenweldeditshallbeairtestedinthepresenceofthe
S.O.
(b) Atappedhole,notlessthan6mmdiameter,shallbeprovidedinthespigotend of each pipe as specified elsewhere, into which a suitable pressure
gaugeshall
be
fitted
for
purposes
of
the
test.
An
air
pressure
of
17
bar
shall
thenbepumpedintotheannularspacebetweenthespigotandsocketand
thepumpdisconnected. Inthecaseofsplitcollarjoints,atappedholeshall
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be provided at each end of the collar and each side of thejoint shall be
pressurised.
(c) If no drop in pressure occurs over the ensuing period of ten minutes, thetest shall be deemed successful subject to careful visual inspection for
leakage during the test. If the test pressure is not maintained for ten
minutes,thepositionoftheleakshallbedeterminedusingsoapsolution.
(d) All defects in the weld shall be cut back and rewelded as directed by theS.O.andthetestreapplieduntilsuccessful.
(e) Thetappedtestholesshallbethensealedoffwithweldingintopositionthethreadedscrewplugaftereachjointhasbeensatisfactorilytested.
(f) The Contractor shall provide all necessary gauges, pumps, etc, for the airtesting.
(g) Therequirementsofthisclauseshallnot limittheContractor'sobligationsin
achieving
satisfactory
results
in
the
tests
on
completion
as
prescribed
later.
G1.2.9.6.5 ThermalFusionJointingEquipment(a) Alltoolingandequipmentusedforthermalfusionjointingshallbeoftypes
in accordance with Employer/ British Gas Standards and shall include all
equipment necessary to cut, plane and clean, clamp, heat and align pipe
andindicateorcontroltemperaturesandheatingandcoolinginaccordance
withEmployer/BritishGasStandards.
(b) Fusion tools and heating plates shall be electrically heated andthermostaticallycontrolledwithanyhandlesorbracketsmadeofmaterial
havingelectricalinsulatingpropertiesconformingtoBS2559:Part3foruse
with230Va.c.or ifmadeofwoodtheyshallconformtoBS3823:Part1.
Thetoolorplateshallbeearthedthroughthegenerator.
(c) A thermometer shall be fitted and shall have a green zone indicating thecorrectfusiontemperaturerangeforPE100polyethelenemarkedwiththe
appropriate code. Thermometers shall be suitably protected from
mechanical damage, shall be replaceable and shall be accurate to 3C
within
the
fusion
temperature
range.
If
an
alternative
temperatureindicating system is used the plate shall have provision for inserting a
suitableconventionalthermometer.
(d) Thewattageoftheheaterelementsshallbesuchthattherequiredsurfacetemperaturerange isreachedwithin15minutes instillairandatambient
temperaturesof20C5C.
(e) TheinputleadsshallconformtoBS6500Table7orotheragreedstandards.(f) The temperature control system (thermostat) shall be flameproof in
accordancewithBS4683:Part2.
(g) Hydraulicramsusedtoalignpipeendsandbringthemtogethershalleachhave independentpressuregauges. Eachgauge shallhavea performance
certificate indicatinganydeviations intruetoactualreadings issuedbyan
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independent tester not less than one month prior to its use. The
certificatesshallbemadeavailabletotheS.O.,togetherwithdatarelating
thehydraulicpressureofthemachinetothetotalforceappliedtothepipe.
G1.2.10 AccesstoInteriorofPipelines(a) Pipesprovidedwithcablepassholesshallbelaidsoastoprovidepassholes
positioned on top of the pipelines in excess of 600 mm in diameter at
intervalsofapproximately60m. Whenapasshole isno longerrequired,
thescrewplugshallbereplacedandweldedtothepipeexternallyandthe
internalandexternalprotectionsystemsshallbemadegoodovertheplug
andholidaytested.
(b) TheContractorshallrecordthelocationofallcableholepassesandensurethecorrectsealingthereof.
G1.2.11 InstallationofUndergroundPipesG1.2.11.1 General
(a) Trenchexcavationandbackfillingshallbecoordinatedwiththeconstructionof the pipeline as a whole so as to ensure expeditious completion of the
wholeoperation.
(b) Trench excavation and backfill shall be carriedout in accordance with therequirementsforEarthworksinthisSpecificationand,wherenototherwise
specified,in
accordance
with
Section
4of
BS
8010:
Part
1.
The
minimum
depth of cover above pipelines shall normally be 1000mm, the depth of
coverbeingmeasuredfromoriginalgroundleveltothetopofthebarrelof
thepipe. Anypipelinewithlessthannormalcovershallbesurroundedwith
atleast150mmofconcreteunlessotherwiseinstructed.
(c) Thelinesandlevelsofthepipelineandthepositionsofthebends,junctionsandotherfittingswhichareshownontheDrawingsmaybeadjustedbythe
S.O. as necessary before construction of a particular section commences.
The pipeline shall be accurately installed to the lines, levels, grade and
positionssetoutbytheContractorfromdatasuppliedtohimbytheS.O.so
that
the
barrel
of
the
pipe
shall
be
continuously
supported
throughout
its
lengthbythebottomofthetrenchorbybeddingmaterialasspecified.
(d) TheContractorshallsubmitfulldetailsofthemethodsheproposestouseforcontroloftheaccuracyofpipelaying. Siterailsshallbeusedtocontrol
the accuracy of pipelaying unless the S.O. directs otherwise. Where sight
rails are used, they shall be fixed and maintained at each change of
gradient,andatasmanyintermediatepointsasmaybenecessary,butnot
more than 35m apart. Sightrails shall be clearly painted in contrastin