《轮机英语（二三管轮）》-Lesson 20 Marine Compressors

NewWordsandExpressionsextensively[ɪkˈstensɪvli]a.广阔地screw[skruː]n.螺丝钉reciprocate[rɪˈsɪprəkeɪt]v.往复运动knob[nɒb]n.旋钮manipulate[məˈnɪpjuleɪt]v.操作contrary['kɒntrərɪ]a.相反的unload[ʌnˈləʊd]v卸载moisture[ˈmɔɪstʃə(r)]n.水分NewWordsandExpressionschamber[ˈtʃeɪmbə(r)]n.腔intermittently[ɪntəˈmɪtəntli]ad.间歇地fluctuation[flʌktʃuˈeɪʃn]n.波动onerous[əʊnərəs]a.繁重的Anaircompressorisaveryusefulmachineandisnotonlyusedextensivelyinindustryonlandbutonalltypesofshipsaswell.Onashipanaircompressorisusedtocompressairandstoreitintanksforvarioususes.Theseusescouldrangefromsimpleprocessessuchascleaninganddryingoffilterstotaskssuchasstartingtheauxiliaryenginesandthemainenginesoftheship.AirCompressorproducespressurizedairbydecreasingthevolumeofairandinturnincreasingitspressure(seeFig.20-1)(空气压缩机通过减少空气的体积，进而增加空气的压力来产生压缩空气).Differenttypesofaircompressorsareusedaccordingtotheusage.WorkingPrincipleofAirCompressorWorkingPrincipleofAirCompressorFig.20-1WorkingPrincipleofAirCompressorTherearemainlyfourtypesofcompressors:centrifugalcompressor;rotaryvanecompressor;rotaryscrewcompressor;reciprocatingaircompressor.However,onshipreciprocatingaircompressoriswidelyused.Inanaircompressor,therearetwomajorparts-acompressingsystemandapowersource.Thecompressingmechanismcanbeapiston,rotatingimpeller,orvanedependinguponwhichtypeofcompressoryouarereferringto.Asforthepower,itissuppliedbyanelectricmotororotherenergysources.Thecompressingmechanism,asthenamesuggests,helpsincompressingatmosphericairbyusingenergyfromthepowersource(顾名思义，压缩机械利用来自能源（电源）的能量压缩大气中的空气).TypesofAirCompressorsThebasicworkingprincipleofanaircompressoristocompressatmosphericair,whichisthenusedaspertherequirements.Intheprocess,atmosphericairisdrawninthroughanintakevalve;moreandmoreairispulledinsidealimitedspacemechanicallybymeansofpiston,impeller,orvane.Sincetheamountofpulledatmosphericairisincreasedinthereceiverorstoragetank,volumeisreducedandpressureisraisedautomatically.Insimplerterms,freeoratmosphericairiscompressedafterreducingitsvolumeandatthesametime,increasingitspressure(简而言之，自由空气或大气在减小其体积之后会被压缩，同时会增加其压力).TypesofAirCompressorsThereisapressuresettingknobthatcanbemanipulatedasperthedemandsoftheoperator.Whenpressureinthereceiverortankincreasestothemaximumlevel,thepressureswitchisshutoffandintakeofairinthecompressorisstopped.Contrarytothis,whenthecompressedairisused,thepressureinsidethecompressorfalls.Asaconsequence,thepressuredropstoalowsetting,andthepressureswitchisturnedon,thusallowingatmosphericairtoentertheunit.Thisway,thecycleoftakingairinsidetheunitandremovingcompressedaircontinuesinanaircompressor.TypesofAirCompressorsAllcompressorsneedtobeunloadedduringstarting,stopping,andatregularintervals.Itisforthefollowingreasons:1)Duringthestartingofamotorthestartingcurrentisveryhigh,sotoavoidfurtheroverloadingofthemotorthecompressorisstartedunloaded.Whenthecurrentcomesdowntotherunningvalue,theunloaderisclosedandthecompressorcomesonload.2)Astheairiscompressedinvolumeitreleasesalargeamountofmoisture.Thisoilywatermixtureisincompressibleandifitispresentinsidethecompressionchamberitcandamagethepistonandthevalves.Forthisreasonalsothecompressorisstartedunloadedsothatallthemoisturepresentinsideisdrained.UnloadingoftheCompressors3)Atstoppingthesameisdonesoastodrainallthemoistureinsideandinpreparationforthenextstarting.4)Intermittentlythecompressorisunloadedtoremovethecondensedwaterinsidewhichcouldgooutsidewiththeair.Therearedifferenttypesofunloadersforthepurposeofunloading.Someofthemarepneumaticandsomearesolenoidoperated.Theyallhaveatimerinthecircuitwhichenergizesthesolenoidatthestarting,stopping,andintermittently.UnloadingoftheCompressorsTheoperatingmanualoftheparticularmachinewouldgivethespecificitemstobecheckedandthesamemustbereadbythemarineengineeruponjoiningtheship(特定机器的操作手册将给出具体的检查项目，轮机员上船时必须阅读这些内容).However,aroughguidelinehasbeenpresentedbelow:1)Lubrication:checktheoillevelinthesumpandinthelubricatortank.2)Unloading:thevalvesintheunloadinglinesmustbeopen.3)Pressuregaugecocks:thecocksmustbeslightlyopentoavoidexcessivepressurefluctuationswhichcandamagethepressuregauges.4)Airfilter:checkthattheairintakefilterisclean.OperatingProcedureofaReciprocatingCompressor5)Cooling:checkthatthecoolingwaterpressureiscorrectandinthecaseofattachedpumpsavisualcheckofthepumpandallthevalvesinthelinemustbeopen.6)Reliefvalves:somereliefvalveshavehandtestingleversgivenfortesting,thesamecanbedone.7)Airlinepiping:checkthatallthevalvesinthedischargepipingareopenandcorrectlylinedup.8)Finalcheck:thecompressorcanbeturnedafewrevolutionswithaturningbartocheckforthefreemovement.Aftertheabovecheckshavebeenmadeacompressormaybestartedwiththeunloadersopen.OperatingProcedureofaReciprocatingCompressorThoughthemaintenancedoneonthecompressorsonboardwoulddependonthemanufacturersadviceandtheplannedmaintenanceprogramsetupbythecompany,thebelowisaroughguidelineaboutwhatistobedoneforanewjoiningmarineengineer.1)Cleanairfilterat250runninghours.Thoughneglectedandoftenthoughtasordinary,thisfilterisinfactveryimportantasitisfilteringthecontaminantsfromcominginsidethecompressionspaceandreducingabrasionsonthelinersurface.Alsoadirtyairinletfiltercanraisethedeliverytemperatureoftheairtoadangerouslevelwhichcanbewellabovethelubricatingoilflashpointandneartheautoignitionpoint.Thusabadlymaintainedairinletfiltercancauseanexplosion.RoutineMaintenanceofReciprocatingCompressors2)Cleanandinspectvalvesat250runninghours.Thevalveistheheartofthecompressor,anditoperatesonceeveryrevolution.Thevalvescanbedamagedduetoimpactforcesorduetotheingressofforeignparticles.Excessivelubricationalsohasbeenknowntodamagethevalves.Thevalvesshouldberemoved,inspected,andoverhauledatregularintervals.Abrokenvalvecanfallontothepistonandcauseextensivedamages,thusforthisreasonthevalvemaintenanceisofvitalimportance.3)Changecrankcaseoilat500runninghours.Lubricatingoilcanloseitspropertyoveraperiodoftimeduetotheonerousoperatingconditions.However,thesyntheticlubricatingoilscanbeusedforalongerperiod.RoutineMaintenanceofReciprocatingCompressors4)Checkdrivebeltsat250runninghours.Av-beltisgenerallyusedtodrivethecoolingwaterpump.Thetightnessofthebeltshouldbecheckedandadjustedtothecorrectvalueatproperintervals.Inaddition,abeltdressingspraywouldprotectthebeltsaswellasincreasethetransmissionofthepowerandreducetheslippage.5)Checkunloaderoperationat250runninghours.Ataregularintervaltheoperationoftheunloadersshouldbecheckedandifnotsatisfactoryshouldbeinvestigatedandcorrected.Theaboveisanexampleoftheroutinemaintenanceoftheaircompressors.Inadditiontotheaboveatroutineintervalsthepistonwouldhavetobepulledoutandthepistonringschanged,bumpingclearanceschecked,bearingschanged.Allthiswouldbedoneonthebasisoftheplannedmaintenanceprogrambasedonthemanufacturer’sadvice.RoutineMaintenanceofReciprocatingCompressorsThoughtheproblemsencounteredonboarddifferfromshiptoship,abriefguidelineisgivenregardingthecausesofthedifferentsymptoms.1)Lubeoilpressurelow:causescanbeleakageinpipes,suctionstrainerchoked,oilgradewrong,gearpumpfaulty,faultypressuregauge,increasedclearancesofthebearings,andoillevellow.2)Coolingwaterhightemperature:causescanbecoolingwatervalvesclosed,coolingwaterpipingblocked,coolingwaterpumpbeltloseorbroken,coolingwaterpumpfaulty,noflowofcoolingwater,andlowlevelofcoolingwaterintheexpansiontank.TroubleshootingMarineCompressors3)Compressornoisy:causescanbebearingsworn,crankshaftendplayhigh,dischargepressurehigh,poorfoundation,smallbumpingclearance,pistonringsworn,linerwornoutcausingpistonslap,valvesnotproperlyseated,andvalvesbrokenorfaulty.4)Firststagedischargepressurelow:causescanbethatthefirststagesuctionvalveisnotclosingfullyandallowingtheairtoleakduringthecompressionoritisnotopeningfullyallowinglessairtocomeinthechamberorthedischargevalveisfaultyandopeningprematurelyorincorrectspringshavebeenfittedwhicharecompressingonlittlepressure,intakefilterfouled,leakagefrompistonrings.TroubleshootingMarineCompressors5)Firststagedischargepressurehigh:causescanbethatthesecondstagesuctionvalveisnotholdingandwhilecompressionhighpressureairiscomingtotheinter-coolerandshowinganincreaseinthepressure,inter-coolertubeschoked.6)Secondstagedischargepressurelow:causescanbeleakagefromthepistonrings,secondstagesuctionvalvefaultyandallowingtheairtoescape,secondstagedischargevalveleakingoropeningprematurelyduetowrongspringsfitted.TroubleshootingMarineCompressors7)Secondstagedischargepressurehigh:causescanbeobstructionintheaftercooler,obstructioninthedischargevalve,airbottlepressurehigh,secondstagedischargevalvespringsverystiff(第二级排气压力高：可能会导致后冷却器阻塞，排气阀阻塞，气瓶压力过高，第二级排气阀弹簧变硬).Theaboveisjustabriefexposuretotheproblemsencounteredonboardandhowitmustbeinvestigated.Anexperiencedmarineengineerkeepsaneyeontheparametersandknowswhenmaintenanceisexpected.TroubleshootingMarineCompressorsSomeofthefaultsofSPERREHV2/285Acompressorwhichmayoccurduringoperationaresummarizedbelow:Table20-1FaultsofSPERREHV2/285ATroubleshootingMarineCompressorsFaultsymptomPossiblecauseRemedyAThecompressorhaspoorcapacityand/ordoesnotproducefullpressure.Dirty,wornordamagedvalves.Inspectandcleanallvalves.Replacedefectiveparts.

Pistonringshavestuckintheringgrooves,oraredamaged/broken.Disassembletherings.Cleangroovesandringsandreplacedefectiveparts.Reassemble,applyingoiltothecylinderwalls.

Leakingsafetyvalve.Replacesafetyvalve.

Defectivecylinderheadgasket.Replacegasket.

Cloggedairfilter.Cleanfilter.BLPsafetyvalveblows.HPsuctionvalvedamagedordirty.Inspectandcleanvalvesandreplacedefectiveparts.

LeakingsealinHPsuctionvalve.Replaceseal.

LPsafetyvalvedefectiveordamaged.Replacesafetyvalve.TroubleshootingMarineCompressorsCHPsafetyvalveblows.Stopvalveintheairlineisclosed.Openthestopvalve.

Cloggednon-returnvalve.valve.Replacedefectiveparts.Removeandcleannon-return.

HPsafetyvalvedefectiveordamaged.Replacesafetyvalve.DValvesneedoverhaulingtoooften.Overheating.Checkcoolingwatercirculationandtemperature.Inspectandifnecessarycleancoolers.

Pollutedintakeair.Inspectintakefilter.

Poorlubricatingoil.Changeoilgrade.

Valveclampboltsnottightenedenough.Tightentheclampboltstothecorrectmoment.EOverheatingand/orabnormalnoiseincrankcase.Defectivebearings.Inspectbearingsandcheckclearances

Lowoillevelorcondensationinoil.Drainandcleancrankcasesump,fillwithnewoil.

Jammingcrankshaftbearing.Checkbearingclearances.Replacedefectiveparts.TroubleshootingMarineCompressorsFPistonoverheatingandfriction.Incorrectfittingofpistonorcrossheadbearing.Replacedefectiveparts,checkpistonclearances,ringclearancesandcrossheadbearing.Coolingmalfunction.Checkcoolingwatercirculationandtemperature.GIncreasedoilconsumption.Wornpistonrings.Replacepistonrings.