土木工程专业英语(1)

Plumbing
Ingeneral,plumbingreferstothesystemofpipes,fixtures,andotherapparatusudinsideabuildingforsupplyingwaterandremovingliquidandwaterbornewasters.Inpratice,thetermincludesstormwaterorroofdrainageandexteriorsystemcomponentsconnectingtoasourcesuchasapublicwatersystemorapointofdisposalsuchaspublicwersystemoradomesticptictankorcesspool.
Thepurpoofplumbingsystemsis,basically,tibringinto,anddistributewithin,abuildingasupllyofsafewatertobeudfordrinkingpurposandtocollectanddispoofpollutedandcontaminatedwastewaterfromthevariousreceptaclesonthepremiswithouthazardtothehealthofoccupants.Codes,regulations,andtradepraticesaredesignedtokeepthewatersystemparatedfromdrainagesystems;topreventtheintroductionofharmfulmaterialsuchaschemicals,micro-organisms,anddirt;andtothekeepthewatersystemsafeunderalloperatingconditions.Theprotectivecodesalsoaredesignedtopreventfloodingofdrainagelines,provideventingofdangerousgas,andeliminateopportunitiesforbackflowofdangerouswastewaterintothewatersystem.Itisntialthatdia-producingorganismsandharmfulchemicalsbeconfinedtothedrainagesystem.
SincethetimeofMosmanhasbeencautionedtodispoofhiswastessafely,andcleanlinesshasbeenrelatedtotheavailabilityotwaterandassociatedwithsocialcoustom.Earlymanoftenlivednearawatersourcethatrvedashiswatersupplyanddrainagesysteminone.Itwasalsohisbath.Latrine-likereceptacleswithcrudedrainshavebeenfoundinexcavationsintheOrkneyIslandsofNeolithicstonehutsatleast10,000yearsold.Bothawatersystemandpipingudasdrainagefashionedofterra-cottapipewerepartoftheroyalpalaceofMinosinCrete,about2000BC.Thepalacealsohadalatrinewithwater-flushingrervoiranddrainage.NothingcomparabletoitwasdevelopedinEuropeuntilthe18thcentury.Eventheequipmentofthemodernbathroom,thoughmuchimprovedwithhotandcoldwaterunderpressureandlesscrudeprovisionsfordrainage,isinconceptlittledifferentfromtheMinoanversion.Itwasoutuntiltheendofthe19thcenturythatadvanceinplumbingpracticeweregivenriousattentionasanintegralpartofhousing.
Abuildingplumbingsystemincludestwocomponents,thepipingthatbringspotablewaterintothebuildinganddistributesittoallfixturesandwateroutletsandthepipingthatcollectsthewaterafteruanddrainsittoapointofsafedisposal.
Watersystems.Whenabuildingisrvedbyapublicwatersystem,theplumbingbeginsattherviceconnectionsrequiredtomakewateravailableatoutletsrvingthefixturesorequipmentwithinthebuilding.
Manypremisinruralareasarenotrvedbypublicwatersupply.Themayincludeprivatedwellings,apartmenthous,hotels,commercialcentres,hospitals,institutions,factories,roadsidestands,andrestaurants.
Publicwatersupplieshavesurfacewaterorgroundwaterastheirsources.Largewatersystemarealmostentirelysuppliedwithsurfacewater.Insmallercommunitiesandincertainareasgroundwaterisobtainedfromwellsorsprings.Independentmipublic,industrial,andprivate-premiwatersystemsfrequentlytakewaterfromwellsonthepremibutmay,undercertaincondtionsdrawwaterfromaspring,lake,orstream.
Publicwatersystemssupplytreatedwatermeetingpublicwater-supplydrinking-waterstandards
.Private-premisystemsareexpectedtoprovidewaterofequalquality,andtodosotheprivatesystemrequiresawater-treatmentplantincludingchlorinationasaminimunandpossiblydimentation(ttlingoutofsolidparticles)chemicaltreatment,primarilyforsoftening,andfiltration.
Waterissuppliedtofixturesandoutletsunderpressureprovidedbypumpsorelevatedstoragetanksorboth.Insomeinstallationsapumpcontrolledbyapressure-activatedswitchonapressurizedstoragetanktakeswaterfromawellandpumpsuntiltheupperlimitotpressureforthesystemhasbeenreached.Ifwaterisbeingudattherateitisbeingpumped.,thepumpoperatescontinuously.Elevatedstoragetanksareusuallyequippedwithhigh-andlow-level-floatcontrolswitchestoactivatethepump.Whenthetankgetsloethepumpstartsandcontinuespumpinguntilthetankisfull.AstoragetankmaybeconstructedasillustratedinFig.1,oritmaybelocatedontheroofofahighbuilding.Waterfromthetankfeedsthedistributionsystembygravity.Waterflowingthroughpipescausalossofheadduetofriction.Sincebuildingpipingsystemsaredesignedtodeliverwaterattherequiredoutletpressure,pipesizeisacriticalvariable.
Plumbingcodeshavetablesandgraphstoshowtypicalwaterdemandsoffixturesandoutletsinabuilding.Iftherequiredwaterdemandisnotmetbecauofundersizedpipingorunderpoweredpumping,thepressuredopsandsomeoutletsmayhavelittleornowaterflow.Pumpingcodesusuallyspecifypressureandratesofflowforthefixturesinabuilding.Thetotalamountofwaterthatmaybeneededtosupplythedemandcanbecalculatedfromtablesoffixturewaterdemand.Minimumpipesizesfordifferentfixtureinabuildingarespecifiedinplumbingcodes.
Sinceitisuneconomicaltodesignawaterpipingsystemthatwouldprovideflowwithalloutletsopensimultaneously,judgmentandexperienceareudtodeterminetheprobablemaximumsimultaneousdemand.
Averagedailywaterrequirementsvaryaccordingtothetypeofpremisbeingrved.Asingle-familydwellingunitaveragesfrom20to100gallons(80to400litres)perday.Apartmenthouoccupantsuless.Specialurssuchashospitalsandindustriesusuallyrequirefargreaterallowances.
DrainageSystems.Drainageofresidentialbuildingincludesthecollectionofsanitarywastesandroofdrainage.Thesanitarywastesarecollectedinsoilpipesandstacksusuallymadeofcastiron,althoughcertainportionsofconnectingpipemaybegalvanizediron.Whencorrosiveliquidsarecollected,asinlaboratoriesandindustrialplants,thesystemmayincludeplasticorglasspipesorcoatedpiping.Thejoints,bends,tees,elbows,wyes,andmanyotherspecialfittingsaredesignedtocarryawaywasteswithouthavingobstructionsinthepipeorcreatingcondtionsthatwillcaucloggingifsomelargeobjectisdroppedintoafixtureorareceptacle.Cleanoutsandreceptacleoutletsareprovidedwithscreensorgratingstopreventtheentryofcloggingmaterials.Theentirepipingsystemissizedsothatthesmallestsizeisatthefixtureoutlet.Plumbingcodesspecifytheminimumsizesfordrainageconnectionsandthestandardsapplicabletoallpipeandfittingmaterials.
Normallyallbuildingdrainageisconstructedsothatwastewaterflowsbygravitytothemainhoudrain.Thehoudrainisusuallyconnectedoutsidethebuildingtoagravity-flowhouwerthatleadstoapublicweronapointoftreatment.Inlargebuildingssuchasapartmenthou,commercialbuildings,hospitals,andindustrialplants,thehoudrainmaybelowerthanthepointofdischarge.Wastesarethendischargedtoasump,orstoragepit,andallofthebuildingdrainageisliftedbypumpsorpneumaticejectorstoapointofdischargetotheexteriorwersystem.Theliftingdevicemptywaterfromthe
storagesumponacyclingbasisactivatedbyfloatcontrolsthatpreventfloodingofthestoragearea.Suchunitsareusuallyinstalledinduplicateandoftenhavealternatesourcesofpowersuchasadiel-orgasoline-powergeneratorforemergencypumping.
Roofdrainageiscollectedinguttersandleadersandtakenbyappropriatepipingtoapointofdischargepermittedbylaw.Isolateddwellingsmaydraintosurroundingground,whilelargerbuildingshaveadrainagesystemsimilartothesanitarysystemthatconnectsintoapublicstorm-waterwersystem.
Homedisposalsystemsareudinruralareas.Thehoudrainisconnectedtoaptictankwithatiledrainagefieldortoacesspool.Theptictankremovesheavysolidmaterialsfromthewaste,andtheeffluentortreatedwaterisallowedtopercolateintothesoilthroughburied,speciallyconstructed,rock-filledtrenchesoverwhichtileswithopenjointsarelaid.Enoughtrenchmustbeconstructedtoallowpercolationwithoutfloodingthesurfaceoftheground.Theeffluentfromptictankscontainsdia-causingbacteriaandcannotbeallowedtoflowdirectlyintostreamsorundergroundwaters.Healthcodesandregulationsspecifythesizesofhomedisposalunitsandcontrolthedischargeofeffluent.
Premisoftenhaveotherwaterusincludingswimmingpools(bothoutdoorandindoor),ornamentalpools,fishpools,andfountains,Therequirewaterandarepartoftheplumbingsystem.Sinceswimming-poolwateriasilycontaminatedbybathers,itmusteitherbereplacedfrequentlyorfiltered,chlorinated,andrecirculated.