UK MCA 4th Class Oral

SOUTH TYNESIDECOLLEGE FACULTY OF MARINE AND MECHANICAL ENGII\EERING CLASS 4 EXAMINATION OUESTIONS l.

Explain what you know about 66M"Notices. Merchant shipping notices, or "M" notices as they arecommonlycalled,occupya specialposition. are advisory notices which do not have a force in law, but thosewhich give advice on safety matter regarded as authoritative documents by courseof inquiry into shippingcasualtiesand as such woulr considered extremely persuasivein a legal sense. There are now three tlpes of notice issuedby the MCA 1. MGN ( Marine Guidance Notes ) Blue Provide advice and guidance on safety and pollution matters. 2. MIN ( Marine Information Notices ) - Green Provide information intended for a more limited audienceor of shortterm duration. 3. MSN ( Marine Shipping Notice ) White Will contain mandatory information relating to the legal requirementsetout in related statutory instruments. There is no legal requirements to carry Marine GuidanceNotes andMarine information Notes on UK registeredvessels. It is a legal requirement to carry Merchant ShippingNotices.

2.

Explain what you know about " Code of Safe Working Practices". Accidents are usually the result of carelessness, mistakes,lack of thoughtor careand often result in Consideration must be given on how to avoid accidentshencethe " Codeof Safe Working practice Examples include the wearing of working clotheschosenforthe job with its hazardsin mind. They fit fairly closely with no loose flaps, strapsor raggedpockets. Ciothing shouldcover as much as the as possible and a stout pair of shoesshould be worn, with steeltoecaps.Neck chains,finger rings ar wristwatches should not be worn, particularly in the vicinity of rotatingmachinery. Where particula hazards are present appropriate protection such as gogglesor ear muffi, shouldbe worn. When overhauling machinery or equipment it must be effectively isolatedfrom all sourcesof power may involve unplugging from an electrical circuit, the removal of fusesor the securing open of circu breakers. . Suction and discharge valves of pumps shouldbe securelyclosedand the pump casing rel pressure. Special care should be taken with steamoperatedor steamusingequipmetrt to "ngye no F build up occurs. When lifting components during overhaul, screw in eyeboltsshouldbe usedwhere possible. These : be fully entered up to the collar and the thread of the eyebolt shouldbe in good condition. Lifting w should be in good condition without broken strandsor sharpedges. Before any work is done on the main engine, the turning gear shouldbe engagedand a warning notic posted at the control position. Lubricating oil in the working areashouldbe cleaned up and where necessary suitable staging erected. The turning gearshould be madeinoperativeif nofrequired durir overhaul- Where it is used, care must be taken to ensureall personnelareclear before it is used. Overhead working, boiler operation. Entry into enclosedspacesare otherexampleswhere special car procedures have to be rigidly followed never taking short cuts.

3'

What portable extinguishers would you expectto find in an engine room and what colo used?

The outercontainercontainssodiumbicarbonate powder. A capsuleof carbon dioxide gasis locatr beneatha plungermechanismin thecentralcap. bn depressing the plunger the carbondioxide gas the powderup a dischargetubeandout if the discharge-nozzle. The dry powderextinguisherconbeusedon all classes offire but it hasno cooling effecl It is t, locatednear electricalequipmentin the mochinerytpori and elsewhereon the ship. Foam- Red 5% Cream/Buff--Chemical The main containeris filled with sodiumbicarbonate solutionand a long inner polyhene container with aluminiumsulphate.Theinnercontaineris sealedby a capheld in place Uy r plunger. When plungeris unlockedby turningit , thecapis released.Theextinguisheris then inverted-forthe two to mix- Carbondioxideis producedby thereactionwhichpressurisesthe container and forcesout t foam. Foam- Red 5% Cream/Buff--Mechanical The outercontainerin this caseis filled with water.The centralcontainerholds a carbondioxidech a foam solution.A plungermechanism with a safetyguardis locatedabovethe central container. Whenthe plungeris depressed thecarbondioxideis releasedandthe foam solution and the watern: arethen forcedout througha specialnozzlewhichcreatesthe mechanicalfoam. This extinguisher I internalpipeandis operatedin theuprightposition. Foam extinguishersare usedon classB fires and witl be located in the vicinity ofjtammabte tiqa C.O2- Red 5% Black A very strongcontaineris usedto storeliquid carbondioxideunderpressure. A central tubeprovidr outerpassage for the carbondioxidewhichis releasedeitherby a plunger bursting a disc or a valve operatedby a trigger. The liquid changes to a gasasit leavesthe ixtinguisher *d pursesthroughth swivelpipeor hoseto a discharge horn. Carbondioxideextinguishersaremaintyusedon ClassB and Cfires and wig befound in the ma space,particularly near electricalequipmenl The carbon dioxitle extinguisher i not permitted it accommodationsince,in a conJinedspaceit is lethal. - Red CFC Extinguishers

5%Green

Soda- Acid Red The containerof this extinguisherholdsa sodiumbicarbonatesolution. The screw-on cap containsr plungermechanism coveredby a safetyguard.Belowtheplungeris a glassphial containingsulphur Whenthe plungeris strucktheglassphialis brokenandthe acidand sodium bicarbonatemix. The resultingchemicalreactionproduces carbondioxidegaswhichpressurisesthe spaceabovethe liquir forcing it out throughthe internalpipeto the nozzle. This extinguisheris usedfor classAfires and will befound in the accommodation ereas. 4.

what type of fire extinguisherwouldbe usedon a fire in:-? (a) Galley (b) Accommodation(c) ControlRoomor Radio Room (d) Electrical Switchboard (e) Pump Room (a) Galley- CO2andDry Powder (b) Accommodation- SodaAcid Extinguisher ( seebelowfor description) (c) control Roomor RadioRoom- coz or Dry powder (d) ElectricalSwitchboard- COZor Dry powder (e) Pumproom- Foam,COzor Dry powder

5.

what are the main causesof serious engine room fires ? oil leaks. Fuel, hydraulicor lubricating oil onto hot surfaces. Smoking, burningor welding. Rags and combustibledebrisallowed to build up in the bilge's

6.

\ilhat immediateaction must be taken if a fire becomes serious enough to have to evacuate all personnel from the engineroom and what precautions must be taken before re-entering? Flood the machineryspacewith whatever fixed fire installation is fitted. Say CO2. Before flooding get everybodyout. - do a head count. Where possibleall personnelmust be made aware of the decision to flood the machinery spacewith The spacemust thenbe completely sealed4gainst the entry and exit of air and all oil suiplies isolatr tank valves. When all thesemattershave beenattendedtoothe COz can be admitted and if the srurounding bulkl hold to containthe ftre , it will quickly go out. Cooling of the boundary bulkheads should continue outside the spacewhile flooding is taking place. When the extinguished fir. has been left long enou cool down the spacecan be re-entered. This should be done from the tunnel, if there is one, oi frolowest point from the seatof the fire. Engineers wearing breathing apparatusmay now enter, taki water sprayhoseswith them to cool down any hot surfaces. Coolingand smoke dispersalare the fir priorities, to providean atmospherein which others can operate andgradually bringthe machinery s back into service. Where a machineryspacefire involves electrical equipment then only dry powder or Co2extinguisl be used until the equipmentis isolated.

7.

What pumps on board ship can be used to supply water to the fire main ? Fire pump.- usuallytwo or three fitted Fire and bilge pump. General servicepump. Emergencyfire pump.

8.

Is there an emergencyfire pump ? If the answer is y€s, where is it fitted and how is it tested? External to the machineryspace.-Run on a weekly basis. Some pumps maybe fitted in the steeringcompartrnent.

9.

Define what you would considerto be an enclosed space where the internal atmosphere may br frequently hazardousto personnelwho may enter. Duct Keel, doublebottomtanks,cofferdams,boilers, CO2 rooms, pumprooms. Bow thruster compartmentsshouldbe teated with caution if ventilation fans have not been running. Fore peak anr peak tanks shouldalsobe well ventilated and tested before entry.

10.

Describe the procedurewhich should be adopted:(a) Before anyoneis allowed to enter an enclosed space. (b) While anyoneis working inside a closed space. (i) Ventilation for at least24 fus. (ii) Test of atrnosphere by a chemist or Chief Officer for Oxygen and Hydrocarbon content.Zlyo o> (iii) Tank entry permit and tally board for personnel to enter tank. (iv) Breathingapparatusat tank entrance,lifeline and portable lights(air), communication, ild tallier people enteringalongwith ELSA sets. (b) While anyoneis working in the tank there must be a man at the entrance at all times with a mezu communicationbetweenhim and the person(s) in the tank and the Bridge.

ll.

what types of pumps are suitable for useas bilge pumps? Positivedisplacement.- small volumesfor usewifi ows centrifugal with priming pump - Largevolumedischarge.

12.

Give reasonswhy a bilge pump may not be able to removewater from bilges. state typical suction and delivery pressures. Blockedstrum box. ( very high nuru.r* on the gauge) Hole in suction line. ( zero or very low vacuumon the gauge ) Primingpump not functioning if working in serieswith centrifugalpump.

13.

Explain what is the emergency bilge suction( injection).Why is it necessarT and how is it bn into operation? A bilge injection valve is fitted to the end of a branchline connectingwith themainseawatersuct The bilge injection valve is always of the screwdownnon-returntype. This valveenablesthe larg seawatercooling pump to be usedas a bilge pumpin an emergency.To bring thebilgeinjectionv useduringan emergency, the bilge injectionvalveis openearutyand the seasuctioi valveis full; After it is establishedthat the seawatir pumpis capableof loweringthewater levelin theengine seawatersuction may be openedslowly. This shouldbe donein stales sothatthetanktopsareno dry,asthis would causethe seawaterpump to losesuction. Careshould betakento ensuethatthe oftensituatedon the outlet from the main condenser doesnot dischargenearanyelectricalequipmr NB. Seawater pumps are not usually self priming,if of the centrifugiltype.

14.

lhat is the purpose of the oily water separator? To allow the bilges to pumped overboardwith an oil contentof not more thanl5ppm. ReadMARPOL regulations.

15.

Explain in detait the procedure for testingthe steeringgear beforeleaving port. check for oil leaks and any loose linkageson th. steeringgear. check for correctoil level and test low level alarm. Run oneunit at a time, 30 degs-to 35 degs.in 28 secsat full power. where onlyonemainunit is fi anx' unit, the auxiliaty unit must go from 20 degs.to 20 degs.In 60 secs. g at knotsor half speed. Testthe communicationlink betweenthe Bridgeandthe Stee.irrgcompartment.

16.

What is the duty of the engine room crane? To enablelarge and hearryengine componentsto be manoeuwedaround theEngineroomin a safe manner.

17.

Detail checkswhich should be carried out beforeusingthe crane and possible hazardsif not functioning correctly. CheckSWL is not exceeded. Checkthat the direction indicators on the controlscorrespondto the actual movement ^^!of ' v^thecrane. Checkthatthe limit switchesare working. Checkthat the brake is operational. Checkthat all personnelinvolved understandthe signalsto be usedin anyrepairor overhaul.

18.

Give the correct procedure for starting an air compressor. (a) Checkthe oil level (b) Checkthe cooling water. (c) Ensurethat the interstage drains are open. (d) Checkthat all the correct valves *" ol"n fully to the air receiver andthatthereis sufficientca1 availablein the air receiver.. (e) If a manualunloaderis fitted ensurethat it is open.( machine mustbestartedin theunloaded position). (D Whenthe machineis up to speed,closethe unloaderand the interstage drains.

19.

What is the purpose of fitting a bursting disc into the air compressorcasing? A bursting disc' or sometimes a water jacket relief valve are fittedto prevent a build-up of pressur€ a cooler tube fail allo*ing high pressureair to enterthe cooling *ut.i space.

20.

Describe the procedure required to connect in parallel one dieselor steamdriven alternator already on the switchboard with another alternator. Three-phase alternators ilranged for parallel operationrequire a considerableamount of instrume This will include arnmeters, wattmeter, voltmeter, frequencymeteranda synchronising device. M these instruments will use transformers to reducethe actual valuestakento the instrument. This al enables switching, for instance, between phasesor an incoming machineand the bus-bar, so that o: instnrment can display one of a number of values. The watfinetermeasuresthe power being used ir circuit' which' because of the power factor aspectof alternatingcurrentload. will be less thL the p: the volts and amps. Reverse power protection is provided to alternatorssincereversecurrentprotection cannot be used. Alternatively various trips may be provided in the event of the prime mover failure to ensure that th alternator does not act as a motor. The operation of paralleling two alternatorsrequiresthe voltage to be equaland in phase. The alter current output of any machine is always changing,so for two machinesto operatetogether their vol must be changing at the same rate or frequencyand be reachingtheir ma,rimum( or Ly other value together They are then said to be' in phase'. Use is nowadaysmade of a synchroscope when paralleling two machines. The synchroscope has two windings which are connectedoneto eachside of th. p*utt"l switch. A pointer is free to rotate and is moved by the magneticeffect of the two windings. When the two v supplies are in phase the pointer is stationaryin the 12 o'clock position. If the pJinter is rotating tht frequency difference exists and the dial is marked for clockwise rotationFAST and anti-clockwise r sl-ow, the reference being to the incoming machinefrequency. To parallel an incoming machine to a running machinetherefore,it is necessaryto ensure firstly tha voltages are equal. Voltmeters are provided for this purpose. Secondlythe frequencies must ULUro into phase. In practice the synchroscopeusually *orr.r slowty in the fast direction and the parallelir switch is closed as the pointer reachesthe l1 o'clock position. This resultsin the incoming machinr immediately accepting a small amount of load. A set of three lamps may also be provided to enablesynchronising. The sequence method of lamp connection has a key latnp connectedacrossone phasewith the two otherlamps connected over the two phases. If the frequencies of the machinesare different. The lampswill brighten and darken in rotation, depending upon the incoming frequencybeing FAST or SLOW. The correct moment for synchronising is when the key larnp is dark and the other two are equallybright.

21.

What is the purpose of having a synchroscopeand why must it not be allowed to run continuo To ensure alternators to be connectedto bus-barsare at th; correctfrequency. Not to be allowed to rtrrt continuously becausethey are not continuousiyratedand will burn out.

22.

Explain how an emergency alternator starts and supplies power in the event of a blackout. (a) Double pole switch trips on lose of power and on tripping makescontact with emergencyswitch supplying power to emergencygeneratorstartermotor. (b) A low voltage coil, typically 24v, is connectedto the main switchboard. This coil is normally energised and corutected to a normally open contactoron the air startsystemfor the alternator. r the main power fails the coil de-energises,thus completingthe air startsystemand starting the alternator. once the alternator has startedthe air will shut off. When the machine is up to speedand has the correct cyclesand volts, the auto synchroniser will the breaker and put it on the board, (emergencyboard) to supply the essentialservices.

23.

How can a blackout be simulated to test the operation of the emergency alternator? Turn auto synch to offposition to preventthe emergencygenerator tying to put itself on the board starts. Shut power offto startingcoil, this will de-energisecoil and machine will start.

24.

How often should an electric motor be cleaned? Unless there are any specific problemsevery 5 years. Use of vibration monitors are helpful in high bearing problems and thermal trips in the windings can give prior warning of impending problems.

25.

How would you overhaul an electric motor that has been flooded with sea water? Strip down and wash with distilled water,then dry out, if possible in an oven, then check meggar r Should be minimum of I megohm. Heatinglamps can also be used. On completion coat with ,. gor quality electrical varnish.

26.

Explain how to check the insulation resistanceof the motor using a ..Meggerrr. Corurectthe Meggar betweeneachphasein nrrn and the motor casing, after good contact has been : removing paint etc. Resistanceshouldbe I megohm.

27.

Outline the dangers to pensonnelwho may have to enter a battery room to check the conditio: batteries on charge. Hydrogen fumes in poorly ventilatedbatteryrooms which contain lead-acid batteries can be fatal. lr naked flames and dangerfrom sulphuricacid burns. Safety gear must be worn including full face v No smoking as there could be dangerof explosion.

28.

What is the temperature inside low pressureevaporators and why is the water produced suitr drinking? Drinking water can only be madefrom salt water in evaporatorsif it is boiled above 75 degs. C. Mr the low pressureplants operateat tempsranging from 4d degs C. to 60 degs C. and are therefore ur for making drinking water. Other problems to look out for areadditivesusedin diesel engine cooling systems and inhibitors u' water systemsto prevent fouling by marinegrowth.The evaporator should not be used within 12 mi. land

29.

what are the reasonsfor using the main engine turning gear? (a) To ensurethat the engineis warmedup evinly dissipalittg *y thermal stresses in materials ever therefore the enginecan be loadedmore quickty. (b) For warming through with the indicator cocks open to ensure there is no water leakage in the cy (c) To be engagedif any major overhaulof the engine is taking place. (d) For taking deflections.

30.

Why is tappet clearancenecessaryand what effect would insufficient or excessive clearance h: engine operation? Tappet clearancesare necessaryto allow for the thermal expansion of the valve spindle length at wo temperatures'and to ensurethat positive closing of the valve continues as it wears or seats d*irrg ,r, Clearancesshould normally be setwhile the engineis cold and the czrm follower is offthe cam peak wear of the valve gearwill tend to increaseclearances. Excessive tappet clearanceswill causethe valve to open late and close early in the cycle and will rec ma'ximum lift- It will also causenoise,and eventually damage,from the impact of working surfaces Insufficient clearancewill causethe valve to open early and close late with increased marimum lift. extreme cases'it may preventthe valve from closing completely as it expands or beds in. This in tul causehot gasesto blow past valve faces,causing.ruln burning and low compression.

31.

Describe how to prepare the main enginefrom cold to ready to start to manoeuvring includi: that require to be carried out. (1) Before a large diesel engineis startedit must be warmed through bv circulating hot water thror jackets etc' This will enablethe various engine parts to expand in relation to one another and a engine load to be increasedsoonerratherthan later. The lubricating oil should also be heatedand circulated around the bearings etc., and the pisto: cooled. The various return pipes on both the water and oil systemsshould be checked to ensureno blo and the return temperatuesshouldbe monitored. (2) The various supply tanks, filters, valvesand drains are all to be checked and opened or closed i required (3) All control equipment,alarmsetc. shouldbe examined for correct operation. (4) The indicator cocks should be openand the turning gear engaged and started to ensurethat ther water presentin the cylinders.If any water issuesfurth.r investigation can be ca:ried out to asc

Tnecause. (5) All oil levelsshouldbechecked, i.e.sump,turbochargers, governorsetc. (6) The fuel oil systemcanbelinedup andcirculatedwith hot fuel. (7) Any scavenge blowersif manuallyoperated, shouldbe started. (8) Manuallyoperatethe cylinderlubri.utorr. (9) The turninggearshouldberemovedandtheengineblown over on air before closing the indica cocks. (10) The engineis nowavailablefor standby. , l

32.

Why shouldthe cylinderindicatorcocksbeleft openuntil the engine has first beenturned ov, starting air? To ensurethatno waterissuesfromthecockswhich would indicate a leak from the liner, cylinder head,pistoncooling,turbobroweror injectorcooling.

33.

Describethe routineinspectionyouwould carry out beforetaking over the watch on a manne engineroom arrangement.. Checkthe firnnelemissions.Whitesmoke,blacksmoke,steamor sparks. Checksteeringgearandfridgeflats. Enterthe engineroomfrom thetop. Do not usethe lift. Checkcoolingwaterheadertank. check main enginecoolingwaterreturnsandtemperatures. check pistoncoolingwaterreturnsandtemperatures. Listenfor anyunusualnoises. Checkturbochargeroil levels Checkobservation tankfor signsof oil. Checkmist detector. Checkconditionof bilges. Checkpurifier flat andconditionof thefuel oil tanks.i.e. full, empty, temperature.Drain of water. Entercontrol.oop: check log bookandnoteanyirregularities. Confirm the conditionof the electricalsupplyequipmint. How many alternators on load,) amountof J ----on the board.Earthfaults.Standby machines. Readany curent standingorders. The duty engineershouldthen 1nfo* theengineertakingoverthe watch of any abnormal operating conditionswhichhaveoccured duringthewatch.Any oidrr, from the Bridge, recordedin the log br shouldbe pointedout.Any repairsshouldbereportedtogetherwith information on any machinerytt beendismantled'Thepresence of anyothermembersoflhip's staff in the engineroom e. g. Dayvor shouldbe reported.

34.

Give the various operating pressures and temperatures of an engine you are familiar wi

Scavenge air temperatureScavenge air pressure L.O.pressure L.O.temperafire JacketC.W.pressure

40/45 degs.C 1.0 Bar 2.0 Bar 45 degs.C 3.0 Bar

JacketC.W. temperatue -

65 degs. C

- 5/6Bar F.O.Pressure F.O. Temperahre 125 Degs.C Cylinderoil pressure- 40 bar

35.

What factors must be present for an explosion to occur in the diesel engine crankcase? For a crankcaseexplosion to occur, oil mist must be present in the crankcase,and a hot spot must develop,perhapsfrom bearing wear or stuffing box rub etc. The hot spot then ignites the oil mist ca an explosion. ( Seehandout on crankcase explosions or Note 22 CLass4 )

36.

What devicemay be used to detect and warn of dangerous conditions within the crankcase? A Gravineroil mist detector is used to detect and warn of dangerouslevels of oil mist in the crankca The detectorconsistsof two tubes, fitted at one end of each is a photo electric cell, the other end is a lens to allow the passageof light through the tube of the P.E. cell. Light comesfrom a singlebulb a reflectedto eachtube by a mirror. One tube is sealed and contains clean air and is termedthe referer tube. The other tube is called the measuring tube and is used to pass samplesthrough it. Samplesa drawn from the crankcaseusing a fan drawing through a rotary valve. If a large amountof mist is dr into the measuringtube, less light can penetrate the tube to the P.E. cell, so therewill be a differencr output from each sample and depending on the amount of difference will activatean alarm. In the er an alarm,the load of the engine should be reduced immediately by slowing to Dead Slow Aheadand soonas possiblethe engine should be stopped and the turning gear engaged. Openthe indicator coc turn the engineto prevent seizure. Allow engine to cool to normal operatingconditionsby observin returntemperatures.Whensafe BUT NOT BEFORE 20 MINS the crankcasedoors can be openedar crankcaseinspected. A visual inspection from outside the crankcaseshould be madefor signsof wl metal or excessiveoil leakagefrom bearings or anything which might indicate a problem. If nothing obviousthe lubricating oil pump can be stopped and a more detailed inspectioncarried out.

37.

What immediate action should be taken in the event of a warning being given? Reducepower manually if crankcase mist detector does not do so automatically. Receivepermission the bridgeto stop the engine. Allow to cool down before inspecting the crankcasefor signsof the hc (Seenote23 Class4 notes)

38.

What factors must be present for a scavenge air manifold fire to start? Dirry scavengeair trunking. lncorrectamount of cylinder lubricating oil. Defectivefuel valve and bad combustion. lncorrectfuel valve timing. Worn piston rings and liner. Chokedexhaust. Defectivestuffing box. ( Seeclass 4 notes page 20 )

39.

How would you becomeaware that a scayenge fire had started? Erratic enginespeed. High exhausttemperatures. Smell of burning paint. Turbochargersurge. Smokefrom funnel. Rise in J.W. temperafire of affected unit.

40.

How would you deal with a scavenge fire? In the event of a scavenge fire the bridge must be informed, as should the C/E, that the enginehasto reducedto D.S. Ahead immediately. Increasecylinder lubrication to all units by increasing the mechanicallubricator flow to mar g.4 Add sulph'ric acid,strength0. 02N from a me€rs'redb'rette until the samplegoesclear. ppm CaCo3:ml O.O2Nx l0 Chlorides Retainabovesample Add a few dropssulphtrricacid o.o2N to ensure solutionis no longeralkaline. Add 10dropspotassiumchromate. Samplewill turn yellow. Add silvernitratefrom a measuredburette until samplejust turnsa brick red colot'. Ppm CaCo3 : ml silvernitratex l0

IDS 100ml sample ldd l0 dropsof phenolphthaleinindicator. Neutralisewith I drop of aceticacid lT. a samplein pot & fitto conductivity meter. Takea readingof meter - temperaturecompensate andreadoffscale. ( VanadomolybdateTest tLq!@ ) Place5 ml distilledwater in r 0 ml left hana tube. Place5 ml Boiler water in r 0 ml right hand tube. Topup to 10 with reagent- Stopler and shakeandallow to standfor 3 mins. $ Placeleft hand tubein L.H. sideof lovibond competitor Placeright handtube in R.H. side of lovibond compactor Hold up to light andfind colour match - take readingof cardin ppm. (colourmetrictest) @ Thoroughlyrinsesamplebottle with the water to be tested. Arrangetr;rro50 ml nesslertubesside by side Add 0'2 ml of thymol blue indicator soiution from a graduatedglassdropperinto theR.H. nesslertt Add 50 ml of sampleto the R.H. nesslertube. Add 50mlof sampleto the othernesslertube. (This is theblank) Placethe samplecylinder in the R.H- compartment of theNessleriser andthe blankcylinderin the compartment.

ilff,ffilii,fi:#,il;ffiffiTffi:'*.the

corours intherwo windows using aconstant right s,

Hvdrazine Reselve. Arrangetwo 50 ml nesslertubesside by side. Agd 15ml hydrochloricacid 0.5N ,t "rreilhto eachcylinder Add to the R'H' cylinderby pipette zs iitof sampleandmix with a glassrod. Add to the R'H' cylinderby pipette l0ml of dimethyl,amineamineberzaldehydesolution andthoror mix. Add to L.H. cylinderby pipene 35 ml of sample andthoroughlymix.

ftfiliifrT::H"ffi,*|"

"' cvlinder in theR-H.comparnnent ofthenessleriser andtheL.H.cyri

Matchthe samples4gainstthe colo'rs of the disc. Disc readine : ppm hydrazine ml of sample

49.

what is the purposeof adding chemicalsto the boiler water? To increasethe alkalinityor thJphosphatereseryeor to actasa Coagulant.In other words to mainti limits requiredby the manufacturerof the boilerandto minimisedamageto the plant.

50.

Explain how the water levelin the gaugeglasscanbe verified

I E

t t

as correct.

Close2 &3 and0penI - If freeflow from gauge thendrainis clear.Open2 - if free flow steam connection is clear.(No waterlevel in glass) Closez-------Open 3 - freeflow from ar"i", water connection is clear.Notegaugeglasswill be showing full. Finallyclose3 andopen2leaveio allow gaugeglasslo retumto workinglevelagainthenclose I and open 3, levelmaybeslightlyhigh until water temperaturereturns to normal. Seeblowinggaugeglassnotes 32,33.

51.

If you find no visible water in the boiler gaugeglass what immediate action should be takeni If there is no automatic shut-offof boiler nir to birners then shut-offthe fuel manually. sound tht Engineers alarm and call the Chief Engineer. Blow the gauge glass to seeif there is iven the slightest bit of water in the gauge glass. If no water Do Nor ADD WATER until the correct level oitt. boiler waterhas beenestablishedbecausett shock of adding water to overheatedboiler tubescould collapsethe boiler tubes.It is better to let tl cool naturally to their working temperature.

52.

Why is the presenceof oil in the boiler water most undesirable? (a) Cuts down the heat transfer when oil adheres to boiler tubes(internally) (b) Causespriming resulting in water and oil carry over to the superheatersand turbines. (c) Combines with suspendedsolids in the boiler waterto producesticky deposits.

53.

why should oxygen content of boiler feed water be reducedto a minimum? (A) Attacks on boiler metal resulting in pitting anddepositionof iron oxide on the boiler tubes. (B) Corrosion of the condensatesystemto produce iron and copper** in the condensate. *:$ copper is attacked by ammonia in the presenceof oxygen.

54.

How can this be achieved when an open hotwell and feed systemis used ? (a) By keeping the hotwell temperatureat approx. 90 degs.c. The oxygen content of water at 50 d is approx. FOUR times that of 90 degsC. (b) Ensure deaeratoris functioning conectly. (c) Stop air leaks into condenser,condensate systemand boiler feed system. (d) Ensure the correct level of Hydrazine is being addedto the deaeratedfeed water. (e) Introduce Amines into the low pressure/temperaftue part of the feed system. (f) BV floating polysryreneballs on top of the tank.

tJ.

rf the plant is un-manned, what would be provided to raise the alam r'if the rsv water vv"rr/r level rrevrsrr'' in the rrr' I

too low or too high and how often are these tested?

Mowbray float alarms. Leveltransmitters.Testedweekly. Foxboro (Pneumatic)High /Low level trips.Tested*r.kly.

56'

what causesfires to start in boiler uptakes.what are the hazards.How are they deter actionsshouldbe taken? Build up of sootdepositsarea causeof fires,possibly causedfrom faulty sootblowers. They aredetectedwith temperafiresensors - thermometers or similartype devices. The hazardsarethat if left unchecked thefire maydevelopinto a hydrogenfire The actionto be takenis:_ 1. Shutdown the boilerfiresandclosetheair registers. 2' Shutdown the F.D. fan andensurevanesareclosed.( alsostandby fans ) 3' Increasefeedflow througheconomisers (if fitted),blowingdownthe boiler drum as requ

57'

on a steamship,what are the main reasonsfor using the main engineturning gear? To ensurethat the heatis evenlydistributedwhile*u*rling throughandthat turbine rotors c to pressurein the maincondenser (underslung varieties). To aid in gearboxinspections, shaftbearings-etc.

58'

Describehow to prepareand flash up a highpressure water tube boiler. 1. open drum ventsandeconomiser vents( if fitted). 2' Fill boilerto oneinchin glass.( enstueall drains on waterdrumareclosed). 3. Opensuperheater vent.(Recirc). 4. Opendrainson superheater headers. 5' Setfuel oil rail up onHFO if steamavailable, otherwiseflashup on DO. 6. Line up atomisingsteam. 7. Line up forceddraughtfan. 8. Ensureair heateris by-passed. 9' Flashup the boiler on smalltip at lowestrateaccording to manufactures recommendatior steamgraduallyleavingdrurnventopenuntil steamissues at approx.2bar.Superheatervent until flow is guaranteed.( Boileron line ). 10. Testall trips puttingboileron line.

59'

Describethe warming throughprocedurerequired prepare to the main turbines from c to ready to start of manoeuvringincludingchecks and tests. 1' Run main lubricatin-soil purnpsensr:rinfalltemperatures andpressuresare normal. 2. Startthe main circulatingpump. 3. Engagethe turninggear. 4' open up the glandsteamto maint?inu positivepressure aboveatmosphericat the turbine 5' Openthe steamto thefirst stageair ejector.( mar.vac 10ins ) 6' Startthe main condensate pumpensuringthecondensate re-circvalve is open. 7' open the auxiliaty exhaustfrom theauxiiarycondenser to the main condenser. 8. Ensureall turbinedrainsareopen. 9' Openwarmingthroughby passvalvesonthemain steamline. 10. Rotateturbinesby meansof theturninggear. I l ' Graduallyincreasethemaincondenser vacuumby slowlyopeningup steamto the air eject until fully open. 12' Adjust glandsteamasnecessary to keeppressure just aboveatmospheric. Checkoperationof varioustrips associated with mainturbines.i.e. overspeed,low lube oil, lr Dependingon the installationtheremaybevariousother trips fitted.

60. How is the main turbine prevented from over speeding and what trips would need to be reset? The main

n'bine has an overspeedtrip ( normally . ,pJ"d hmiting u.n to, ) to prevent overspeed caseof a coupling failure or the ship's propellet "I"-irrg the wavm o*ing rough seas. The trip ur fitted with three independentcircuiis, which sense trre turuine speedby meansof pick ups mo'nte, turbine pedestals,aod receive a speedsignal from three pulses iroauced by a tootled wheel. The shutsa numberof control valveslo.ut"Jin the steam chlst, which is an internal part of the H.p. tu the overspeedtrip operates,the boiler safety valves may lift, due to a suddendecreasein turbine lo when the trip operates,the mechanical movement alters the position of the trip switch which then energisesthe uppercoil of the relay and at the same instant dL- energisesthe lower coil, thus chanl position of the relay. The coil of the solenoid valve is thus de-energisedand the spring moves dov the oil pressurekeepingthe manoeuwing valve open is lost. Simultaneouslyvisual and audible alt activatedand the particular trip is indicated. After the trip has been reset, (the fault being rectified) resetswitch is madewhich energisesthe lower coil of thl relay, and the solenoidvalve is repositio: protectionsystemis thus reset. Any number of trips can be built into the system.

61.

Explain how the final superheated steam temperature is controiled on a high pressure/high temperature water - tube boiler and why is it necessary. Attemperatorsare usedto keep the final superheat t"mjeran r.s within the desiredlimits. It is necr control the temperafi[e to protect the superheater tube materials from overheatingand to reducetht depositsformed on the tubes.

62.

Describethe routine inspection you would carry out before taking over a watch on a manned room of a steamship. Seequestion33 In addition :_ check deareatorlevel, check F.D. fans, bearings etc.,. Checkair heatersand economisers. Inspectboiler water levels and automatic combustion controls including fuel oil temperaturesand pressures. check aroundturbine manoeuwing controls lookin g attemperatures and pressuresand for signsof r lights etc. (Gaggedvalves ). Checkmain condenservacuum. Checkgravity tank overflow sight glass.

63.

Give the various operating pressures and temperatures of a steam propulsion plant you may t familiar with.

64.

\ilhy is there a vacuum in the main condenser? Thereis a vacuumin the main condenserto improve the efficiency of the plant, i.e. to get more wor of the steam.

65.

Give reasonswhy there may be some loss of main condenser vacuum and why is this undesiral l' If condensatetemperatureis below the saturation temperature of the condensri- ai, leakageinto condenseror incorrect operation of the air ejector. 2' If cooling water temperaturedifference is greater than normal - insufficient cooling water, or bloc tubes. 3' If cooling water temperatureis less than normal Dirty tubes, or in the extremecase,division pla washedaway. 4' lngressof air at L.P. turbine gland due to insufficient gland steam pressure. All the abovetoubles causea loss of vacuum and raises the exhaust temperatue of the tubine. This lossof vacuumcausesa loss of power and a loss in plant efficiency. The efilectof a suddenloss in vacuum will be to lift the relief valves on the flrbines. over pressu The L'P' turbine and the condenserare undesirable hence a safety device shutting the steamto the flrbines is required. To continuerunning under low vacuum condition would mean having a higher exhausttemperattu

which can causethe L.P. turbine to hog when fitted with an underslung condenser,thus produc thermal stesses. The limiting exhaust temperattrre is 77 degs C for cast iron and g2 degsC for casings. Loss of Vacuum Trip ln order to improve the efficiency of the turbine, the condenser and hence the ttrbine exhaustis rur very high vacuum(about 730 mm Hg ). This means that the saturation temperatureof the steam 50 degsC. Ideally a turbine should be designed so that at the exhaust the steam i, dry saturated.SI condenserpressure suddenlyrise i.e. the vacuum fails, then since the heat content of the steamis tl and the exhauststeamtemperafltrehas risen to the new saturation temperatrue, the steamwill now I Thus the exhaustconditions have changed, since instead of dry saflrated steam at about 50 degsC have wet steamat a temperafttrein excess of this. This change of condition will causesuddenove of the last few rows of blades,the resulting expansion causing possible blade rubbing. Furtherto tl will also be very rapid erosion as the high speed L.P. blades strike the water particles. To preventthis from occurring a vacuum trip is fitted which closes off the turbine steamsupply sht vacuumfall below a presetlevel. ( usuaily about 50% )

66.

Describethe procedure to start up a turbo-alternator from cold until it is ready to be connect switchboard including trips to be tested and reset. Stan the TA condensercooling water pump. Circulate air ejector/glandsteamcondenser (if fitted bv means of condensate pump, ensuringrecir ) is open. with the useof the priming pump, pump oil round the bearings and the gearbox sprayersensuring pressuresareregisteringon the gauges. Raisethe condenservacuum to 60Yobymeans of the air ejectors and the gland steamand openup t exhaustto the atxiliary condenser. Crack openthe mastersteamvalve having first made sure alt nrbine and line drains are fully open. Adjust steamto H.P. and L.P. glands as necessary until small amounts of steamissue from the glan, Checkoil levelsin the sump and ensuresalt water cooling is lined up to the L.O. cooler. overspeedtrip shouldbe testedevery time the machine is started. one engineer should standby tht mastervalve while anotheroperatesthe throttle valve. The L.O. hand pump should be operatedto e the steamconfol valve to open and allow steam into the turbine once the throttle valve is crackedo Tubine drainscanbe easedin but not closed. By means of a special tool pressingon the governorI the machinecan be overspedand the revs noted for the log book. Once the overspeedtrip haswork delayre-settingof the trips until machine is at approximatlly 40%of the normal speed. CheckL.O. temperatures'Resetthrottle/emergencyvalve and progressively open master steamvalve until appn turn open' Bring machineup to full rated speed by means of the throttle valve and ensuremasterva fully opened' Raisevacuumto morimum. Close all drain valves. Machine is now readyto parallel on boards.w. valvesto L.o. cooler etc. can be regulated to suit. Trips fitted are;- overspeed- Low L.o. - Back p-rr*" trip.

67.

What are nodesand anti-nodes?. Within a vibrating systemcertain points that do not move or have zeroamplitude are called NODES points wherethe amplitudesof vibratory movement are at a ma: