Upload
666667
View
213
Download
0
Embed Size (px)
DESCRIPTION
kyuky
Citation preview
6/10/2015 marinediesels.co.ukSecondengineerssamplequestionMarch2002question1
http://www.marinediesels.info/samples/2nd_Class_Mar_2002_Q1_sample.htm 1/2
marinediesels.co.uk
SampleQuestions
SecondEngineersMotorEKs
OtherPages TheBasics The2StrokeEngine The4StrokeEngine Operation Members
March2002Question1.
a. Describe,withtheaidofasketch,achargeaircooler.(6)
b. Describetheproceduresandprecautionstakenwhencleaningbothairandwatersidesofachargeaircooler.(7)
c. Statewhyitisnecessarytomaintaincorrectchargeairtemperature.(3)
a.
Thesketchillustratesachargeaircooler.Thecoolingwatermakestwopassestomaximisecoolingeffecttheairmakesasinglepasstokeepthepressuredroptoaminimum.Amanometerconnectedacrossthecoolerwillgiveanindicationofanyfoulingonthe airside.Themoving tubeplateallowsforexpansion.Sacrificialanodesmaybefitted in thewaterboxestoreducecorrosiveattack,especially if thecoolingmediumisseawater.Theflowofcoolingwater through thecoolerisautomaticallycontrolledtokeeptheairinlettotheengineatoptimumtemperature.
b.
CleaningAirSide
Onalarge2strokecrossheadenginetheaircoolermaybecleanedbyinjectinganaircleanerchemicalintothechargeairwhile theengine is running.Thechemicalused ishazardous tohealthand thusprotectiveclothingmustbeworn, andmanufacturersinstructionsfollowed.Alternatively,asystemusingachemicalcirculatingtank,pumpandbuiltinspraysmaybeusedwhentheengineisstopped.Aftercirculatingthechemicalforaperiodoftimeasinstructed,theaircoolermustberinsedusingfreshwater.Ensuredrainsfromtheaircoolertobilgeareclear.
Onamediumspeedengine,theaircoolercanbecleanedinsitu(withtheenginestopped)byblankingtheairinletandoutletandfillingwithacleaningsolution.Howeveritwillbenecessarytosupporttheaircooler,asthefasteningsusedmaynotbedesignedtocopewiththeextraweight.Howeveritmaybeeasiertoremovethewholeaircoolerandplaceitinabathofcleaning solution.Againprotective clothingmust beworn, and suitable ventilationprovided. It is normalpractisetopressuretestthecoolerstackwhenitisintherinsingbathtocheckforleakingtubes.
CleaningWaterSide
6/10/2015 marinediesels.co.ukSecondengineerssamplequestionMarch2002question1
http://www.marinediesels.info/samples/2nd_Class_Mar_2002_Q1_sample.htm 2/2
Thisisnormallydoneinsituwiththeenginestopped.Afterisolationanddraining,theendcoversonthecoolingwaterboxesareremovedandthecooler is rodded throughorblastedusingapressure lance. In thecaseof the lattersuitableprotectiveclothingmustbeworn.Cleaning thewater side isnormallyonlycarriedoutonaircoolers using seawater.sacrificialanodesshouldbeinspectedandreplacedasnecessary.
c.
Itisnecessarytomaintainthecorrectchargeairtemperatureforthefollowingreasons:
1. Sothatthecorrectmassofairisallowedintothecylinderforcombustionofthefuel.(thehigherthetemperaturethegreaterthespecificvolume)
2. Tokeeptheexhaustgastemperatureatacceptablelevels.(willriseifairtempistoohigh)
3. TopreventwaterdepositingonthelinersurfacedestroyingL.O.filmiftempistoolow.
4. Topreventthermalshockingoflineriftempistoolow.
DHTMLMenu/JavaScriptMenuPoweredByOpenCube