DBSG3050527.docx

DBSG3050527.docx

《DBSG3050527.docx》由会员分享，可在线阅读，更多相关《DBSG3050527.docx（29页珍藏版）》请在冰豆网上搜索。

DBSG3050527

REFERENCE

CAT.

WATERPUMPINSTALLATION

DeterminationofWaterTankCapacity

1.FreshWaterStorageTankandSumpTank:

Thetotalstoragecapacityoffreshwatertankiscalculatedasfollows:

a.domesticbuildingondirectsupply-NIL;

b.domesticbuildingonindirectsupply-135litresforeachofthefirst10flatsand90litresforeachremainingflat;

c.45litresperpointforeachfloorwashingtap.

d.Twinrooffreshwatertanksofapproximatelyequalvolumeshallbeprovidedtomakeupthetotalstoragecapacity.Fortwintankssystem,providepressureswitchatdischargesideofeachupfeedwaterpumptostopthewaterpumpshouldover-pressureoccur.ThecorrespondingfaultsignalisrepeatedatguardcounteronGFoftheblock.

DCMBINo.D01/08

MinutesofBSDRPMeetingheldon14Dec2009---item3.2.1.2.1therein.

A

A

A

M

M

2.FlushWaterStorageTankandSumpTank:

a.Thetotalstoragecapacityofflushwatertankislimitedto45litresforeachwaterclosetifwatersupplyistemporarilyfreshwater.

b.Twinroofflushwatertanksofapproximatelyequalvolumeshallbeprovidedtomakeupthetotalstoragecapacity.Fortwintankssystem,providepressureswitchatdischargesideofeachupfeedwaterpumptostopthewaterpumpshouldover-pressureoccur.ThecorrespondingfaultsignalisrepeatedatguardcounteronGFoftheblock.

c.Providebucket-typestrainerbeforeinletofsumptank,whichiscleansedatregularinterval.

d.Provideautomaticself-cleaningstrainer（auto-strainer）influshsaltwatersupplysystemforthedomesticbuildingsinpublichousingestates,withaviewtoreducingthefrequencyofsuspensionofflushwatersupplyarisingfromclogginginpipeworkandpressurereducingvalves.

DCMBINo.D01/08

MinutesofBSDRPMeetingheldon14Dec2009---item3.2.1.2.1therein.

MinutesofBSDRPMeetingheldon14Dec2009---item3.2.1.2.1therein.

DCMBINo.D03/09dated18May2009.

A

M

M

M

3.StorageDistributionbetweenSumpTankandRoofTankforFreshandFlushWater:

a.Thetotalstorageistobedistributedbetweenthesumptankandrooftank.TheratioofthecapacityofthesumptankandrooftankistobeinaccordancewithHongKongWaterworksStandardRequirementsissuedbyWSDandthattheeffectivevolumeofthesumptankislargeenoughforthepumptorunforatleast3minutesevenatnoin-flowcondition.

A

4.FireServicesWaterTank:

a.Thecapacityofthesumptankislargeenoughforthepumptorunforatleast3minutesevenatnoin-flowcondition.Forfireservicesroofstoragetank,thecapacityrequirementisinaccordancewiththeCodeofPracticeforMinimumFireServiceInstallationsandEquipment.

A

5.EffectiveVolumeofWaterTank:

a.Forwatertanksusingfloatswitchestocontroltheinflow,theeffectivestorageofwateristhevolumebetweenthehighlevelcut-outpositionandthelowlevelcut-inpositionexceptFH/HRandsprinklerwatertanks.

b.Itisrecommendedtosetthelowlevelcut-inswitchesto100mmabovethetopoftheoutletpipesoftheroofwatertanksasfaraspracticable.

A

DeterminationofPumpFlowRate

6.ThepumpflowrateforthefreshandflushwaterpumpsystemsisdeterminedusingthePlumbingEngineeringServicesDesignGuide.

A

7.Thepumpflowrateforthefireservicesfeedpumpsystemissuchthattheroofstoragetankistobefilledupinlessthan6hours.

A

8.Thepumpflowratesaretobecounter-checkedagainstthoserecommendedbyWSD.Wherethereisdiscrepancy,liaisewithWSDtodeterminetheflowrate.

A

DeterminationofPumpHead

9.Thepumpheadcanbecalculatedfromthefollowingformula:

Hp=Hs+Hf+Hv

whereHp=pumptotalhead

Hs=statichead

Hf=headlossthroughstraightpiperun+

headlossthroughfittings

Hv=velocityhead（=0）

A

10.Forreference,frictionlossthroughpipeworkcanbefoundbyusingHazen-Williamsformulainaccordancewithclause18ofLPCSprinklerRulesoralternatively,usingthemethodinPlumbingEngineeringServicesDesignGuideorCIBSEGuide.

A

DeterminationofSizeofWaterRisingMain

11.Thewaterrisingmainissizedsuchthat:

a.theflowvelocityislimitedtobelow2.5m/s;

b.thefrictionallossislimitedtobelow10%oftheequivalentlength.

A

PipesandValves

12.a.Appropriatemetallicpipesandvalvesaretobeusedinhighpressurelocationwhichissubjecttohydraulicshockandmechanicalvibration,e.g.thedischargefromthepumps,therisingmainsto,anddownfeedersfrom,theroofwatertanks.Duringdesignofpipeworkandfittingsinsidepumproom,takeintoaccountthemaintenanceconsiderationinregardoftheirmountinglevel.Theycanbemountedat3mabovefinishedfloorlevelorundersoffitsofbeamsdependingonparticularsituationsatthediscretionofPBSE.

b.Foroutletvalvesofrooftanks,considerationsshouldbegiventotheiraccessibilityfordailyoperation.Theoutletvalvesshouldbelocatedabovethemainroofsuchthatthe“level”dropisnotthewholeheightofthedomesticblock,i.e.attheexternalfaçade.PAshouldbeadvisedtoallowsufficientworkingareasaroundthewatertanksforpiperunsandforerectingtheworkingplatformsandcatladderswhererequired.

A

A

13.GateandGlobeValves:

a.Agatevalveinsteadofglobevalveatthedischargesideofthewaterpumpingsystemisrecommended.

A

14.BallFloatValves:

a.Installationofballfloatvalveshouldbecarriedoutbythesub-contractor.Itisrecommendedtoinstallasfaraspracticabletheballfloatvalveatonesideofthemanhole,occupyingpartoftheopenareaofthemanholeandleavingsufficientclearanceforentrytothetankforotherpurposeasshowninFigure1.

A

DrainsforWaterLeakedfromPumpSealsinPumpRooms

15.Thewaterleakedfrompumpsealsshallbeproperlyconnectedandledtoadrainpointsuchasanopengullyatoutsideofanypumproom.

A

WATERSERVICESINSTALLATION（ByMainContractor）

16.ThescopeofwaterservicesdesignbyBuildingServicesSectionincludesallpipework,valvesandassociatedequipmentuptoandbeforethefollowingpoints,includingspecialconnectiondetails,wherenecessary:

A

a.forpotablewatersystem

i.watertapforwashingmachine,

ii.mixervalveforkitchensink,bathtub,showercubicleandwashingbasin;

b.forfloorwashingsystem

i.watertapforfloorwashing;

c.forflushingwatersystem

i.flushingcisternforwatercloset;

d.forfireserviceswatersystem

i.FSroofwatertanks.

17.Thefollowingdesigncriteriaandpracticesshallbefollowed:

a.Theworkingpressureatcoldwatertapsisintherangeof0.5–5bar.

b.Theworkingpressureatflushcisternsisintherangeof0.2–5bar.Butinordertoallowmoremarginforpressurefluctuation,ahigherminimumworkingpressureof0.7barinsteadof0.2barshouldbedesignedforthosedomesticflatsofwhichpressurereductionvalvesareinstalledinthesystemand/orwhenthedownfeedpipesareintheformofU-configurationviaG/Fresultinginextrapressurelossduetomud/gritaccumulation.Forthelatter,blow-offpointsshouldalsobeprovidedatthelowestpointstoallowpurgingofmudandgritsperiodically.

M

c.Theminimumwaterpressureatthecoldwaterinletoftowngaswaterheateris1.7barindomesticblockanddomesticelementsinnon-domesticblock.Thefollowingmaximumpressurelossfiguresshouldbeusedasareferenceindesignofwatersupplysystemandcalculationofavailablepressurebeforewaterheater.Wherenecessary,boosterpumpsystemshallbeprovided.

i.Bath/showermixerat7l/min.waterflowrate–0.25bar

ii.Showerhoseandshowerheadat7l/min.waterflowrate–0.75bar

DCMBINo.D14/99

iii.Otherpressurelosses（staticlossbetweenheightofshowerheadaboveheatercoldwaterinlet（waterheaterinstalledatapprox.1200mmabovefloor）andpressurelossinwaterpipesandfittings,andattowngaswaterheater）–0.7bar

d.AdequatepressuremarginshallbeallowedinthesystemdesigntoabsorbtheoperatingaccuracytolerancesofPRV,typicallyintherangeof+15%to–5%ofthenormalreductionratio（forexample,from2:

0.87to2:

1.05for2:

1PRV）.PRVshallbesizedaccordingtomanufacturer’srecommendations,forprovidingstableperformanceinparticular.Generallythepropersizemaybesmallerthantheconnectingpipeworksizede.g.forflowratelessthan10l/s,PRVmaybesizedatonecommercialsizesmallerthanthatoftheconnectingwaterpipe.

A

18.PipeworkmaterialshallbeselectedinaccordancewiththetableinAnnex3.

19.Communalwaterpipesshouldnotpassthroughdomesticflats.

M

EquipotentialBondingforConnectionofPipesandFittingsofDissimilarMetalsUsingDielectricFittingsorEpoxy-coatedFlanges

20.EquipotentialbondingistobeprovidedbytheElectricalSub-contractoratconnectionsofpipesandfittingsofdissimilarmetalssuchascoppertoductile/castironusingdielectricfittingsorepoxy-coatedflangestoensuretheelectricalcontinuityofthepipinginstallations.

A

FRESHWATERBOOSTERPUMPINSTALLATION

21.Provideboosterpumpinstallationforfreshwatersystemwherenecessarytoprovidesufficientavailablepressuresstatedinpara.16above.

A

IRRIGATIONSYSTEMSFORPLANTINGAREAS

22.Installationofirrigationsystemsistobelimitedtoplantingareasofrestrictedaccess.Forplantingareasinexcessof1500 m2,watersupplytoirrigationpipesmaybebyusingautomaticallycontrolledgravityfeedsystemormanually/automaticallycontrolledwaterpumps.Itsadoptionisdependento