02COLD WATER SUPPLY

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1、CITYUNIVERSITYOFHONGKONGDIVISIONOFBUILDINGSCIENCEANDTECHNOLOGYCourse:BST21541PipedServicesChapter2-ColdWaterSupply1.MainsDistributionThewatersupplysystemsbeginfromtwooutletsfromservicereservoirslinkingintoavarietyoftrunkmainstoservenearlyalldistrictsinHongKong

2、.Withineachdistrict,servicesreservoirwillalsobeprovidedandtrunkmainsintheformatofringmains(supplyfromtwoindependentservicesreservoirs)forthegeneralsupply.Fromthesetrunkmains,branchesofsub-mainwillbeteedtowardsroads,streetsandevenprivateroadsforthewatersupplysy

3、stems.Servicewaterpipesarerunfromthesemainstoindividualpremises.Theservicemainsaredividedintosectionsandsluicevalves(ofthegatetype)areusedtoisolateeachsectionforrepair,maintenanceoranyotherpurpose.Inlayingwatermains,structuralconsiderationssuchasloadduetotraff

4、ic,backfill,etc.shouldnotbeignored.Normally,theminimumdepthis0.9munderroadsistheprimaryconsideration.Inthepavement,pipecannotbeburiedlessthan0.6m.Nearly100%availabilityofthecoldwatermainsand70~75%coverageinflushingwatermainscanusuallybeconnectedinHongKong(Thep

5、ercentageisinanareafactor).SomeareasinHongKongsides,IslandsandNortheastareasinNewTerritoriesarelackofflushingwatersupply.TheinformationcanbeavailablebyconsultingtoTheWaterSuppliesDepartmentintheformofaletterofenquiry.2.PressureandFlowinMainsTrunkmainsusuallypr

6、ovidewithsufficientpressureandquantitiesofwatertosupplyvariouspremises.Thetrunkmainsusuallymeetthemaximumdemandduringpeakhoursfromitsoutletstoallconnections.Trunkmainsarenormallyintherangeof75to300mmdiameterorevengreater.100and150mmdiametermainpipesareprobably

7、beingthemostcommonsizesinsideastreetorroad.Butthetrunkmainundertheroadfromtheservicereservoirwillbenormallylarger.Submainteedofffromthetrunkmainleadingtowardsprivateareaswillbedesignedbythedeveloperwithasufficientcapacitytosupplyanyprojectdevelopment.Mainsshou

8、ldcoverfresh(cold),flushingwater,andfireservicesringmains.But,itdependsonthelocation(district).Itmayonlyhaveoneortwotypesofwatersuppliesbutnotthreeofall.Metallicandmostrecentlyplas