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GMA CoC EOOW practice questions

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Question 1Marine engineering watchkeeping and safe operation of machinery

During an unmanned machinery space (UMS) period, which alarm must be arranged to initiate an engineer call-out to the accommodation even if the duty engineer is not in the ECR?

  1. The extension alarm for any critical machinery alarm Correct answer.
  2. The fire detection alarm only
  3. The bilge high-level alarm only
  4. The steering gear low oil level alarm only

Explanation

Under UMS operation the class rules require a duty engineer alarm system that transmits critical machinery alarms to a location outside the machinery space, typically the accommodation, so that the engineer is alerted even when the ECR is unattended. Individual alarms such as bilge high level are inputs to that system, not substitutes for it.

Question 2Marine engineering watchkeeping and safe operation of machinery

The main engine is running and the low lubricating oil pressure alarm activates. What is the first action of the engineer on watch?

  1. Check the pressure gauge and alarm panel to confirm the condition Correct answer.
  2. Increase engine load to raise oil pressure
  3. Silence the alarm and continue the watch
  4. Stop the lube oil purifier immediately

Explanation

The first step in alarm response is to verify the alarm against an independent indication such as the local pressure gauge, because a faulty sensor and a genuine pressure loss require very different responses. Only after confirming the actual condition should protective action or machinery adjustment follow.

Question 3Marine engineering watchkeeping and safe operation of machinery

Which document must be completed before a main engine is restarted after a planned overhaul involving removal of a bearing cap?

  1. A check-off list confirming the work is complete and the engine is safe to run Correct answer.
  2. A ballast water exchange record
  3. A stowaway search record
  4. A bunker delivery note

Explanation

Restarting machinery after maintenance requires a formal check that all work is finished, tools and personnel are clear, and guards and interlocks are restored. This is normally recorded on a check-off or work-completion list signed by the responsible engineer.

Question 4Marine engineering watchkeeping and safe operation of machinery

During a machinery space round, you find the level in the main engine expansion tank falling steadily with no visible external leak. Which action is most appropriate?

  1. Top up and take no further action
  2. Reduce the cooling water pump speed
  3. Open the expansion tank vent to atmosphere
  4. Investigate for internal leakage into the engine or a failed cooler, and inform the duty engineer Correct answer.

Explanation

A steady loss of cooling water with no external leak points to an internal path such as a cracked liner, leaking gasket or a tube failure in a heat exchanger. The cause must be found before topping up, since water entering the lube oil or cylinders can cause serious damage.

Question 5Marine engineering watchkeeping and safe operation of machinery

What is the purpose of the dead-man alarm or watchkeeping timer in the engine control room during UMS operation?

  1. To log the engine rpm every hour
  2. To require the watchkeeper to acknowledge at set intervals, proving they are alert Correct answer.
  3. To record fuel consumption
  4. To start the standby generator automatically

Explanation

The dead-man alarm requires periodic acknowledgement within a set time; failure to acknowledge raises an alarm and may escalate to a general call-out. It exists to confirm the watchkeeper is conscious and attentive, not to perform logging or control functions.

Question 6Marine engineering watchkeeping and safe operation of machinery

The low sea water pressure alarm sounds while the main engine is at full sea speed. Which immediate action best protects the machinery?

  1. Ignore the alarm until the next watch
  2. Open the sea water overboard valve further
  3. Increase the sea water pump speed without checking
  4. Reduce main engine load and investigate the sea water pump and strainer Correct answer.

Explanation

Loss of sea water pressure threatens the central coolers and hence lube oil and jacket water temperatures, so load should be reduced to cut heat input while the cause is found. Investigation should cover pump condition, suction strainer blockage and valve line-up.

Question 7Marine engineering watchkeeping and safe operation of machinery

Which of the following is a requirement before entering a fuel oil tank for inspection?

  1. An open tank lid for natural light
  2. A gas-free certificate and enclosed space entry permit with standby man Correct answer.
  3. Only a torch and gloves
  4. Verbal permission from the chief engineer

Explanation

Tank entry requires atmosphere testing, a gas-free or safe-for-entry certificate, an entry permit, ventilation and a standby man at the entrance. These controls protect against oxygen deficiency and flammable or toxic atmospheres.

Question 8Marine engineering watchkeeping and safe operation of machinery

What does the term 'standby' mean when the bridge orders main engine standby?

  1. The engine is running at full sea speed
  2. The main engine is ready for immediate manoeuvring and the engineer is at the control station Correct answer.
  3. The engine is stopped and the watch is closed down
  4. The engine is being overhauled

Explanation

Standby means the propulsion plant is prepared for immediate manoeuvring: the engineer is at the controls, auxiliary systems such as steering gear and starting air are confirmed ready, and the engine can respond to telegraph orders at once.

Question 9Marine engineering watchkeeping and safe operation of machinery

A fuel oil purifier begins to vibrate heavily and the bowl discharge is abnormal. What is the correct immediate response?

  1. Continue running until the next port
  2. Stop the purifier, isolate it and investigate before restarting Correct answer.
  3. Increase the throughput to flush the bowl
  4. Loosen the bowl lock ring while running

Explanation

Severe vibration and abnormal discharge usually indicate bowl imbalance, sludge accumulation or incorrect assembly, which can lead to catastrophic bowl failure. The machine should be stopped and isolated before any inspection.

Question 10Marine engineering watchkeeping and safe operation of machinery

The main engine tachometer shows a sudden drop in rpm with the fuel index unchanged. Which is the most likely cause to investigate first?

  1. A change in the ship's draught
  2. Higher fuel oil viscosity
  3. Increased propeller slip due to weather
  4. A fouled turbocharger or air cooler restricting scavenge air Correct answer.

Explanation

If the fuel rack position is unchanged but rpm falls, the engine is losing power, and a common cause is reduced scavenge air from a fouled turbocharger or air cooler. Weather and draught affect load but would normally be accompanied by a governor-driven change in fuel index.

Question 11Marine engineering watchkeeping and safe operation of machinery

Why must starting air lines be drained regularly?

  1. To increase the air compressor delivery temperature
  2. To lower the receiver pressure
  3. To reduce starting air consumption
  4. To prevent accumulated oil and condensate from causing a starting air line explosion or fire Correct answer.

Explanation

Oil carried over from compressors can accumulate in starting air lines and, on contact with high-temperature air during starting, ignite or detonate. Regular draining of receivers and line drains removes this hazard.

Question 12Marine engineering watchkeeping and safe operation of machinery

During manoeuvring, the bridge requests repeated engine orders in quick succession. What is the engineer's key responsibility?

  1. To acknowledge each order and execute it promptly, recording times and orders Correct answer.
  2. To leave the controls to check the steering gear
  3. To wait until the manoeuvre is complete before acting
  4. To increase the governor setting to maximum

Explanation

The engineer on watch must acknowledge every telegraph order, execute it without delay and record the order and time in the bell book or manoeuvring record. This provides a legal and operational record and ensures the bridge's requirements are met.

Question 13Marine engineering watchkeeping and safe operation of machinery

Which condition would justify slowing down or stopping the main engine while on passage?

  1. A small change in sea water temperature
  2. Routine cleaning of the engine room floor
  3. A slight rise in fuel oil temperature
  4. Loss of lubricating oil pressure that cannot be restored Correct answer.

Explanation

Loss of lube oil pressure threatens bearing failure within seconds and, if it cannot be restored, requires immediate reduction or stoppage of the engine. The other conditions are minor and do not affect the safety of the propulsion plant.

Question 14Marine engineering watchkeeping and safe operation of machinery

What is the function of the engine room alarm and monitoring system's 'first-up' indication?

  1. To log the watchkeeper's rounds
  2. To identify which alarm activated first in a sequence of related alarms Correct answer.
  3. To record the highest temperature reached
  4. To display the current fuel index

Explanation

First-up indication distinguishes the initiating alarm from the alarms that follow as a consequence, which is essential for correct fault diagnosis. Without it the watchkeeper may respond to a secondary symptom rather than the root cause.

Question 15Marine engineering watchkeeping and safe operation of machinery

The auxiliary boiler is firing and the water level in the gauge glass cannot be seen. What is the correct action?

  1. Add feed water and continue firing
  2. Open the blowdown valve briefly and then continue firing
  3. Shut off fuel and air to the burner and investigate before restoring firing Correct answer.
  4. Increase firing rate to raise level

Explanation

An unreadable water level may mean the boiler is empty or overfull; either condition makes continued firing dangerous. Fuel must be cut off and the burner secured, then the level verified by gauge glass blowing through before any decision to restore firing.

Question 16Marine engineering watchkeeping and safe operation of machinery

Why is a crankcase oil mist detector fitted to a large diesel engine?

  1. To detect a build-up of oil mist that could lead to a crankcase explosion Correct answer.
  2. To control the oil purifier
  3. To monitor the oil temperature
  4. To measure oil consumption

Explanation

A local hot spot can vaporise lube oil and produce an explosive oil mist in the crankcase, and the mist detector gives early warning. On alarm the engine is slowed and stopped and the crankcase is not opened until it has cooled.

Question 17Marine engineering watchkeeping and safe operation of machinery

The steering gear hydraulic oil level is falling and the bridge reports sluggish response. What should the engineer do?

  1. Reduce the rudder angle limit
  2. Increase the steering gear oil temperature
  3. Switch to the second steering gear pump and investigate the leak Correct answer.
  4. Ignore until the next port

Explanation

Sluggish response with falling oil level indicates a leak or internal bypass, and the standby pump should be brought in to maintain steering capability while the fault is located. Steering is a critical safety system and must not be left degraded.

Question 18Marine engineering watchkeeping and safe operation of machinery

During a blackout, the emergency generator fails to start automatically. What is the correct sequence for the engineer to attempt?

  1. Start the main engine immediately
  2. Start the emergency generator manually from its local panel and restore emergency switchboard supply Correct answer.
  3. Reset the main alternator protection and close the main breaker
  4. Open all circuit breakers on the main switchboard

Explanation

Emergency power for lighting, steering and radio is the priority after a blackout, so the emergency generator should be started manually from its local control position and its breaker closed. Main machinery can only be restored once the main switchboard is re-energised safely.

Question 19Marine engineering watchkeeping and safe operation of machinery

Which of the following best describes the purpose of a planned maintenance system (PMS) on board?

  1. To schedule and record maintenance at defined intervals with defined tasks Correct answer.
  2. To record crew wages
  3. To calculate the ship's stability
  4. To replace the chief engineer's judgement entirely

Explanation

A PMS defines the maintenance tasks, intervals and records for machinery, providing traceability and ensuring statutory and class requirements are met. It supports, but does not replace, the engineer's judgement.

Question 20Marine engineering watchkeeping and safe operation of machinery

A fuel oil transfer operation is in progress and the high-level alarm on a settling tank fails to sound. What is the appropriate action?

  1. Stop the transfer, verify the tank level and repair or replace the alarm before resuming Correct answer.
  2. Close the tank vent to prevent overflow
  3. Increase the transfer rate to finish quickly
  4. Continue transfer and rely on sounding the tank manually every hour

Explanation

A failed high-level alarm is a critical safety defect during transfer, and continuing risks overflow of fuel into the engine room or overboard. Transfer should be stopped, the level verified by independent means, and the alarm repaired before resuming.

Question 21Marine engineering watchkeeping and safe operation of machinery

The main engine is on bridge control and the telegraph fails to respond to a command. What is the safest immediate action?

  1. Continue on the last command until the bridge calls
  2. Reset the control system repeatedly while the engine runs
  3. Increase the governor setting to compensate
  4. Switch to local engine room control and follow orders by telephone or voice communication Correct answer.

Explanation

Loss of remote control requires an immediate transfer to local control so the engineer can execute orders directly, with communication established with the bridge. Continuing on the last command or repeatedly resetting the system leaves the vessel without reliable propulsion control.

Question 22Marine engineering watchkeeping and safe operation of machinery

What is the significance of the load diagram limit curve when operating a large two-stroke engine in heavy weather?

  1. It shows the maximum fuel index permitted at a given speed to avoid overloading the engine Correct answer.
  2. It defines the alarm set point for exhaust temperature
  3. It sets the purifier throughput
  4. It indicates the minimum rpm for idle running

Explanation

The load diagram relates engine speed to power and shows the limits beyond which the engine is overloaded, for example in heavy weather when propeller demand rises. Keeping operation within the limit curve protects against thermal and mechanical overstress.

Question 23Marine engineering watchkeeping and safe operation of machinery

During a crankcase inspection after an oil mist alarm, the crankcase is still hot and the alarm has cleared. What is the correct procedure?

  1. Start the engine to check whether the alarm recurs
  2. Spray cooling water into the crankcase to speed cooling
  3. Keep the crankcase closed, continue cooling and do not open until it is safe, following the company procedure Correct answer.
  4. Open the crankcase doors at once to inspect the bearings

Explanation

Opening a hot crankcase admits air that can cause an explosion of oil mist, so the crankcase must be kept closed and cooled before entry. The engine should not be restarted until the cause has been investigated in accordance with the maker's and company's procedure.

Question 24Marine engineering watchkeeping and safe operation of machinery

A ship is manoeuvring in port and the main engine repeatedly trips on the overspeed protection. Which analysis is most appropriate?

  1. The overspeed device is always at fault and should be bypassed
  2. Run the engine on emergency manoeuvring mode permanently
  3. Investigate whether the trip is caused by governor or control system malfunction, fuel rack sticking or a genuine overspeed, before any reset Correct answer.
  4. Increase the overspeed set point to stop the trips

Explanation

Repeated overspeed trips in port indicate a control or fuel rack fault, or a genuine overspeed caused by propeller unloading, and each possibility requires investigation. Bypassing protection or raising set points removes the safeguard against catastrophic overspeed.

Question 25Marine engineering watchkeeping and safe operation of machinery

Why does a two-stroke engine's scavenge fire risk increase when running at reduced load for long periods?

  1. Incomplete combustion deposits unburnt oil and carbon in the scavenge space, which can ignite Correct answer.
  2. Lube oil viscosity falls at low load
  3. Scavenge air pressure is higher at low load
  4. Cylinder cooling water flow increases

Explanation

Prolonged low-load running produces incomplete combustion, and the resulting oily carbon deposits accumulate in the scavenge air space where they can ignite. Watchkeepers should monitor scavenge space temperatures and drain deposits, and avoid long periods at very low load.

Question 26Marine engineering watchkeeping and safe operation of machinery

During a machinery space round, the engineer finds the auxiliary engine fuel oil day tank level dropping faster than normal, with no increase in generator load. What is the most appropriate first action?

  1. Switch off the fuel booster pump to stop consumption
  2. Check for fuel oil leakage from the auxiliary engine and its supply line Correct answer.
  3. Record the observation and continue the round
  4. Increase the fuel transfer rate to maintain tank level

Explanation

A falling day tank level with unchanged load indicates a leak or abnormal consumption. The engineer must first locate and isolate the source to prevent fire or flooding risk, then report and rectify.

Question 27Marine engineering watchkeeping and safe operation of machinery

What is the purpose of the 'dead man' alarm or vigilance device on the engine room console?

  1. To alert the bridge if the engineer leaves the console
  2. To automatically start the standby generator on loss of power
  3. To log all alarm events for later analysis
  4. To require periodic acknowledgement from the watchkeeper and raise an alarm if not received Correct answer.

Explanation

The dead man alarm demands the watchkeeper periodically reset a timer; failure to do so triggers an alarm to warn others that the watchkeeper may be incapacitated. It is a watchkeeping safety device, not a logging or starting system.

Question 28Marine engineering watchkeeping and safe operation of machinery

The main engine is running at full sea speed when the lubricating oil pressure alarm sounds and the pressure gauge shows a steady decline. What is the correct immediate action?

  1. Stop the main engine immediately and inform the bridge
  2. Increase cooling water flow to the oil cooler
  3. Switch to the standby lubricating oil pump and continue monitoring
  4. Reduce engine speed to idle and investigate the cause Correct answer.

Explanation

A steady lubricating oil pressure decline at full load threatens bearing damage. The engineer should reduce load to idle to lower demand while investigating, and be ready to stop the engine if pressure continues to fall.

Question 29Marine engineering watchkeeping and safe operation of machinery

An engineer is transferring fuel oil between tanks when the high-level alarm on the receiving tank fails to activate. What is the most appropriate action?

  1. Stop the transfer immediately and investigate the alarm fault Correct answer.
  2. Reduce the transfer rate and inform the bridge
  3. Switch the transfer to another tank and continue
  4. Continue the transfer and monitor the tank level manually

Explanation

A failed high-level alarm removes the primary safeguard against overflow. The transfer must be stopped and the fault rectified before resuming, as manual monitoring alone is not an acceptable substitute for a safety device.

Question 30Marine engineering watchkeeping and safe operation of machinery

During manoeuvring, the main engine is required to operate at very low load for extended periods. Which condition is most likely to develop and requires close monitoring?

  1. Increased fuel oil viscosity leading to poor atomisation
  2. Incomplete combustion leading to scavenge space and exhaust system fouling Correct answer.
  3. Overcooling of the cylinder liners causing thermal shock
  4. Excessive turbocharger overspeed due to high exhaust energy

Explanation

At very low load, scavenge air pressure and temperature are low, so combustion is incomplete and deposits form in scavenge spaces and exhaust systems. This raises the risk of scavenge fires and must be managed by following the engine builder's low-load running procedures.

Question 31Marine propulsion systems: diesel engines, steam and gas turbines

In a four-stroke medium-speed marine diesel engine, which component directly actuates the exhaust valve in a conventional cam-operated valve train?

  1. The rocker arm Correct answer.
  2. The fuel injection pump plunger
  3. The turbocharger turbine wheel
  4. The air start distributor

Explanation

In a conventional cam-operated valve train the camshaft lobe lifts a follower and pushrod, and the rocker arm transfers that motion to the valve stem to open the exhaust valve against spring pressure. The turbocharger and fuel pump are unrelated to valve actuation, and the air start distributor only sequences starting air.

Question 32Marine propulsion systems: diesel engines, steam and gas turbines

What is the primary function of the scavenge air receiver on a large two-stroke crosshead diesel engine?

  1. To damp torsional vibration in the crankshaft
  2. To store pressurised air for the starting system
  3. To separate water and oil from the exhaust gas
  4. To provide a stable reservoir of charge air for the scavenge ports Correct answer.

Explanation

The scavenge air receiver sits between the turbocharger/air cooler and the cylinder scavenge ports, giving a steady supply of charge air at the correct pressure for each scavenge period. Starting air is stored in separate starting air receivers, and exhaust gas treatment is not its purpose.

Question 33Marine propulsion systems: diesel engines, steam and gas turbines

During normal running of a marine steam turbine plant, what is the purpose of the condenser?

  1. To remove moisture from steam leaving the boiler
  2. To condense exhaust steam and maintain a low back pressure on the turbine Correct answer.
  3. To increase the pressure of steam returning to the boiler
  4. To superheat steam before it enters the high-pressure turbine

Explanation

The condenser converts exhaust steam to water at low absolute pressure, which maximises the heat drop across the turbine and therefore its efficiency. It also recovers condensate for feedwater. Superheating and moisture removal occur elsewhere in the cycle.

Question 34Marine propulsion systems: diesel engines, steam and gas turbines

In a marine diesel engine, what does the term 'valve overlap' describe?

  1. The clearance between the valve stem and rocker arm
  2. The excess lift of the exhaust valve above its seat
  3. The period when inlet and exhaust valves are both open near top dead centre Correct answer.
  4. The time delay in the fuel injection pump timing

Explanation

Valve overlap is the crank angle period around the end of exhaust and start of induction when both valves are open, using scavenge flow to clear residual gas and cool the combustion space. Valve clearance and injection timing are separate settings.

Question 35Marine propulsion systems: diesel engines, steam and gas turbines

Which statement best describes the working principle of an impulse steam turbine stage?

  1. Steam is accelerated by the moving blades and then diffused in the stator
  2. Steam pressure is converted to velocity within the rotor passages only
  3. Steam expands in stationary nozzles and the resulting high velocity is absorbed by the moving blades Correct answer.
  4. Steam pressure falls across the moving blades while velocity stays constant

Explanation

In an impulse stage the full pressure drop and acceleration occur in the stationary nozzles, producing a high-velocity jet that imparts momentum to the moving blades at essentially constant pressure. Reaction stages, by contrast, expand steam in both stator and rotor.

Question 36Marine propulsion systems: diesel engines, steam and gas turbines

A large slow-speed two-stroke engine has a scavenge air pressure that is falling while engine load is unchanged. Which of the following is the most likely cause?

  1. A fouled turbocharger compressor or air cooler Correct answer.
  2. A worn camshaft bearing
  3. A leaking fuel injector nozzle
  4. Excessive cylinder lubricator feed

Explanation

Scavenge pressure depends on the turbocharger delivering air through a clean cooler; fouling of the compressor or air-side of the cooler restricts flow and lowers receiver pressure. A leaking injector affects combustion in one cylinder, and lubricator or camshaft faults do not primarily reduce scavenge pressure.

Question 37Marine propulsion systems: diesel engines, steam and gas turbines

What is the main reason for fitting a thrust bearing in a marine steam turbine propulsion train?

  1. To allow the rotor to expand freely when heated
  2. To support the weight of the rotor between bearings
  3. To absorb the axial thrust created by steam forces on the blading and transmit it to the hull Correct answer.
  4. To reduce torsional vibration transmitted to the gearbox

Explanation

Steam acting on the blades produces a net axial force along the rotor, and the thrust bearing carries this load into the ship's structure while maintaining axial clearance in the blading. Radial support is provided by journal bearings, and thermal expansion is accommodated by clearances and flexible couplings.

Question 38Marine propulsion systems: diesel engines, steam and gas turbines

On a four-stroke auxiliary diesel engine, the fuel rack is found stuck in the maximum position with the engine stopped. What is the correct immediate action?

  1. Reduce the load on the engine and continue running
  2. Start the engine and observe the governor response
  3. Isolate the fuel supply and investigate the rack and governor linkage Correct answer.
  4. Increase cooling water flow to the cylinder jackets

Explanation

A stuck fuel rack represents an uncontrolled fuel condition that can cause overspeed or fuel flooding on starting, so fuel must be isolated and the linkage investigated before any attempt to run. Starting or continuing to run risks a runaway.

Question 39Marine propulsion systems: diesel engines, steam and gas turbines

Which operating parameter is the most direct indicator of fouling on the gas side of an exhaust gas boiler economiser?

  1. Rising steam drum water level
  2. Increasing exhaust gas pressure drop across the economiser Correct answer.
  3. Falling condensate conductivity
  4. Rising feedwater outlet temperature

Explanation

Gas-side fouling restricts flow and increases the pressure drop measured across the economiser, while heat transfer deteriorates. Feedwater outlet temperature would fall rather than rise, and conductivity or drum level are not direct indicators of gas-side restriction.

Question 40Marine propulsion systems: diesel engines, steam and gas turbines

In a gas turbine propulsion plant, what is the function of the regenerator (recuperator) where fitted?

  1. To transfer heat from exhaust gas to the compressed air before combustion Correct answer.
  2. To cool the turbine blades using compressor bleed air
  3. To separate water from the fuel gas supply
  4. To reduce the compressor pressure ratio at part load

Explanation

A regenerator recovers waste heat from the turbine exhaust and preheats compressor delivery air, reducing the fuel needed to reach firing temperature and improving thermal efficiency. Blade cooling, pressure ratio control and fuel treatment are separate functions.

Question 41Marine propulsion systems: diesel engines, steam and gas turbines

Why is a two-stroke crosshead engine fitted with a diaphragm gland between the scavenge space and the crankcase?

  1. To support the weight of the piston rod
  2. To allow the piston rod to rotate freely with the crankshaft
  3. To cool the piston rod during operation
  4. To prevent scavenge air and combustion products entering the crankcase and contaminating the crankcase oil Correct answer.

Explanation

The diaphragm gland seals the piston rod where it passes from the scavenge space into the crankcase, keeping contaminated scavenge air and combustion residues out of the lubricating oil. It does not carry piston rod weight, allow rotation, or cool the rod.

Question 42Marine propulsion systems: diesel engines, steam and gas turbines

A diesel generator prime mover shows a steadily rising exhaust temperature on one cylinder with normal scavenge air pressure and normal cooling water outlet. Which fault is most consistent with these readings?

  1. A blocked air cooler on the air side
  2. A low sea water inlet temperature
  3. A leaking or dribbling exhaust valve Correct answer.
  4. A partially seized turbocharger bearing

Explanation

A leaking exhaust valve allows hot combustion gas to escape past the seat, raising that cylinder's exhaust temperature while overall scavenge pressure stays normal. Turbocharger and air cooler faults would affect all cylinders and scavenge pressure.

Question 43Marine propulsion systems: diesel engines, steam and gas turbines

What is the purpose of the turning gear interlock on a large marine diesel main engine?

  1. To automatically engage the turning gear at low speed
  2. To prevent starting air being admitted while the turning gear is engaged Correct answer.
  3. To limit maximum engine speed during manoeuvring
  4. To isolate the fuel supply when the engine overspeeds

Explanation

The interlock ensures the engine cannot be started by air while the turning gear is still engaged, which would cause serious damage. Speed limiting is done by the governor and manoeuvring controls, and overspeed protection is a separate function.

Question 44Marine propulsion systems: diesel engines, steam and gas turbines

In a reaction steam turbine, what is meant by the degree of reaction?

  1. The ratio of blade speed to steam velocity
  2. The ratio of moving blade height to mean diameter
  3. The ratio of exhaust pressure to inlet pressure
  4. The ratio of rotor enthalpy drop to the total stage enthalpy drop Correct answer.

Explanation

The degree of reaction expresses how much of the stage enthalpy drop occurs in the moving blades rather than the nozzles; a 50 percent reaction stage splits the expansion equally between stator and rotor. Blade speed ratio, pressure ratio and blade geometry are distinct parameters.

Question 45Marine propulsion systems: diesel engines, steam and gas turbines

A main engine turbocharger suffers a sudden loss of lubricating oil supply while running. What is the most appropriate immediate response?

  1. Trip the engine and stop the turbocharger rotor as soon as safely possible Correct answer.
  2. Increase the turbocharger cooling water flow
  3. Continue running and monitor bearing temperature closely
  4. Reduce engine load gradually to idle

Explanation

Loss of oil supply to a high-speed turbocharger can destroy the bearings within seconds and lead to rotor seizure or fire, so the engine must be tripped and the rotor brought to rest while oil may still be available for rundown. Continuing to run or merely reducing load risks catastrophic damage.

Question 46Marine propulsion systems: diesel engines, steam and gas turbines

Why are large two-stroke diesel engine cylinder liners usually lubricated with a dedicated cylinder oil rather than the crankcase oil?

  1. Cylinder oil is formulated to tolerate the high sulphur fuel and high thermal load in the combustion space Correct answer.
  2. Cylinder oil has a lower viscosity to reduce friction
  3. Cylinder oil is cheaper than crankcase oil
  4. Crankcase oil cannot be pumped at high pressure

Explanation

Cylinder oil must neutralise acidic combustion products from high-sulphur fuel and remain effective at high liner temperatures, while crankcase oil serves the bearings and is kept separate to avoid contamination. Cost, pumping ability and viscosity alone do not explain the separation.

Question 47Marine propulsion systems: diesel engines, steam and gas turbines

In a marine propulsion gas turbine, what is the effect of compressor fouling on performance?

  1. Reduced mass flow, lower pressure ratio and higher specific fuel consumption Correct answer.
  2. Improved surge margin
  3. Reduced turbine inlet temperature at constant load
  4. Increased mass flow and higher power output

Explanation

Fouling roughens and restricts the compressor passages, reducing mass flow and pressure ratio so that fuel consumption rises for the same output and the surge margin is reduced. Output falls rather than rises.

Question 48Marine propulsion systems: diesel engines, steam and gas turbines

What is the purpose of the water seal (water gland) on a steam turbine rotor where the shaft passes through the casing?

  1. To prevent air leaking into the low-pressure turbine and steam leaking out to atmosphere Correct answer.
  2. To measure shaft axial position
  3. To lubricate the shaft journal
  4. To cool the shaft during high-load operation

Explanation

In condensing turbines the casing is below atmospheric pressure, so a water seal prevents air ingress that would raise back pressure and reduce vacuum, while also stopping steam leakage out. Journal lubrication, shaft cooling and axial position measurement are separate functions.

Question 49Marine propulsion systems: diesel engines, steam and gas turbines

A diesel engine fuel injection pump delivers fuel later than the specified timing. Which effect is most likely?

  1. Lower fuel consumption at full load
  2. Higher peak cylinder pressure and earlier combustion
  3. Increased scavenge air pressure
  4. Retarded combustion, higher exhaust temperature and reduced power Correct answer.

Explanation

Late injection delays combustion, so peak pressure falls, exhaust temperature rises and power output drops for the same fuel quantity. Early injection raises peak pressure, and scavenge pressure is not directly changed by injection timing.

Question 50Marine propulsion systems: diesel engines, steam and gas turbines

Which statement correctly describes the role of the air cooler (intercooler) in a turbocharged diesel engine?

  1. It removes water from the fuel supply
  2. It heats the charge air to improve ignition
  3. It reduces the turbocharger speed at high load
  4. It increases the density of charge air by cooling it after compression Correct answer.

Explanation

Compression in the turbocharger raises both pressure and temperature; the air cooler removes heat so the charge is denser, giving more air mass per cycle and lowering thermal load. Heating the charge, fuel treatment and turbocharger speed control are different functions.