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Question 1Marine engineering: propulsion machinery, engines and auxiliary systems

Under the SOLAS machinery requirements, what is the main purpose of the quick-closing valve fitted on the fuel oil tank outlet of a diesel engine room installation?

  1. To meter the fuel flow so that consumption can be logged accurately
  2. To prevent fuel from draining back to the settling tank when the engine stops
  3. To isolate the fuel supply to the engine in the event of a fire in the engine room Correct answer.
  4. To regulate the fuel pressure delivered to the high-pressure injection pumps

Explanation

Quick-closing valves on fuel oil tank outlets are a fire-safety arrangement. They allow remote isolation of the fuel supply to the machinery space from outside the space, cutting off the fire's fuel source. They are held open by the remote operating gear and close automatically or manually when released.

Question 2Marine engineering: propulsion machinery, engines and auxiliary systems

In a four-stroke medium-speed diesel engine, what is the function of the turbocharger?

  1. It drives the camshaft through a gear train at half engine speed
  2. It raises the density of the charge air so that more fuel can be burned per cycle Correct answer.
  3. It cools the exhaust gas before it enters the scavenge air receiver
  4. It removes water vapour from the combustion air before the inlet valve

Explanation

The turbocharger uses exhaust gas energy to drive a compressor that delivers air at higher pressure and density to the engine. The denser charge allows a correspondingly larger quantity of fuel to be burned, increasing power for a given cylinder volume. The charge cooler then reduces the temperature of this compressed air.

Question 3Marine engineering: propulsion machinery, engines and auxiliary systems

What does the term 'scavenging' describe in a two-stroke crosshead diesel engine?

  1. Injecting a small quantity of fuel to ignite the main charge near top dead centre
  2. Removing sludge from the crankcase lubricating oil by centrifugal separation
  3. Replacing the burnt gases in the cylinder with fresh charge air through the scavenge ports Correct answer.
  4. Circulating cooling water through the cylinder jacket during the compression stroke

Explanation

Scavenging is the process by which exhaust gases are swept out of the cylinder and replaced by fresh air. In a uniflow two-stroke engine, air enters through scavenge ports at the lower part of the liner and the exhaust leaves through a central exhaust valve. Effective scavenging is essential to give the cylinder a full charge of fresh air for the next cycle.

Question 4Marine engineering: propulsion machinery, engines and auxiliary systems

What is the primary purpose of the charge air cooler (intercooler) on a turbocharged diesel engine?

  1. To condense water out of the exhaust gas before the turbocharger
  2. To reduce the pressure of the charge air to the level required for scavenging
  3. To reduce the air temperature and thereby increase the mass of air entering the cylinder Correct answer.
  4. To heat the air so that ignition delay of the fuel is shortened

Explanation

Compression in the turbocharger raises both the pressure and the temperature of the air. Cooling the air in the charge air cooler increases its density, so a greater mass of air is trapped in the cylinder for a given swept volume. This allows more fuel to be burned and lowers thermal loading on the engine.

Question 5Marine engineering: propulsion machinery, engines and auxiliary systems

What is the main function of the fuel injection pump in a conventional diesel engine?

  1. To atomise the fuel into the cylinder through the nozzle holes
  2. To deliver a metered quantity of fuel at high pressure at the correct moment in the cycle Correct answer.
  3. To filter solid particles from the fuel before it reaches the injector
  4. To maintain a constant fuel level in the high-pressure header during operation

Explanation

The injection pump pressurises the fuel and meters the quantity delivered for each cycle, and its timing determines when injection begins relative to top dead centre. Atomisation itself takes place at the injector nozzle, which is a separate component. Correct quantity and timing control are essential for combustion quality and engine output.

Question 6Marine engineering: propulsion machinery, engines and auxiliary systems

In a marine diesel engine, what is indicated by a rising differential pressure across the lubricating oil filters?

  1. The oil cooler is transferring too much heat to the cooling water
  2. The oil viscosity has fallen below the normal operating range
  3. The oil pump delivery has increased due to higher engine speed
  4. The filter elements are becoming blocked and require cleaning or renewal Correct answer.

Explanation

A rising pressure differential across a filter indicates increasing resistance to flow, which is normally caused by accumulated contaminants on the element. When the differential reaches the specified limit, the element should be changed or the filter cleaned. Continuing to operate risks bypass opening and unfiltered oil reaching the bearings.

Question 7Marine engineering: propulsion machinery, engines and auxiliary systems

Which statement correctly describes the function of the air starting system on a large marine diesel engine?

  1. It admits compressed air into the cylinders at the correct crank angle to rotate the engine for starting Correct answer.
  2. It supplies combustion air to the cylinders during normal running
  3. It pressurises the crankcase to assist oil circulation on start-up
  4. It provides control air for the fuel injection timing advance mechanism

Explanation

The air starting system uses compressed air admitted to selected cylinders through starting air valves at the appropriate crank position. This produces torque to turn the engine up to firing speed. Once the engine fires on fuel, the starting air is shut off.

Question 8Marine engineering: propulsion machinery, engines and auxiliary systems

What is the purpose of the crankcase oil mist detector on a large diesel engine?

  1. To measure the water content of the lubricating oil returning from the bearings
  2. To detect leakage of cooling water into the lubricating oil system
  3. To give an alarm when a combustible oil mist concentration builds up in the crankcase Correct answer.
  4. To monitor the temperature of the oil at the engine inlet

Explanation

An oil mist detector continuously samples crankcase atmosphere and raises an alarm if the concentration of oil mist rises. A high concentration can indicate a hot spot such as a bearing running hot, and an explosion risk exists. Early alarm allows the engine to be slowed or stopped before a crankcase explosion develops.

Question 9Marine engineering: propulsion machinery, engines and auxiliary systems

A main engine is running at constant load when the exhaust gas temperature after one cylinder falls significantly below the others. Which fault is most consistent with this reading?

  1. The charge air cooler is fouled on the water side
  2. The fuel injector for that cylinder is partially blocked and delivering less fuel Correct answer.
  3. The scavenge air receiver pressure is too low for all cylinders
  4. The turbocharger is delivering too much air to the whole engine

Explanation

A single-cylinder exhaust temperature deviation points to a fault local to that cylinder. A partly blocked injector reduces fuel delivery, lowering the heat release and hence the exhaust temperature for that unit. The fuel pump timing and compression condition of that cylinder should also be checked.

Question 10Marine engineering: propulsion machinery, engines and auxiliary systems

Why is it important to keep the jacket cooling water outlet temperature above the dew point of the combustion gases at the liner surface?

  1. To prevent the formation of hard scale in the cooling water passages
  2. To avoid condensation of sulphuric acid on the liner and resulting corrosive wear Correct answer.
  3. To keep the lubricating oil in the crankcase from freezing
  4. To ensure the piston rings expand to their correct running clearance

Explanation

If the liner surface temperature falls below the acid dew point, sulphuric acid formed from sulphur in the fuel and water vapour can condense on the liner. This causes cold corrosion of the liner and rings. Maintaining a suitable jacket water temperature keeps the surface above the dew point and limits this wear.

Question 11Marine engineering: propulsion machinery, engines and auxiliary systems

What is the effect of excessive cylinder liner wear on the operation of a two-stroke engine?

  1. Reduced fuel injection pressure at the nozzle
  2. Increased blow-by past the piston rings and higher scavenge air consumption Correct answer.
  3. Increased compression pressure in the cylinder
  4. Lower exhaust gas temperature at all loads

Explanation

As the liner wears, the ring-to-liner sealing deteriorates, allowing combustion gas to blow past the rings into the scavenge space. This raises scavenge air consumption and can lead to fouling and higher temperatures. Compression pressure typically falls rather than rises because of the leakage.

Question 12Marine engineering: propulsion machinery, engines and auxiliary systems

During manoeuvring, the engine room receives a bridge order for 'Dead Slow Ahead'. What is the correct response of the watchkeeping engineer?

  1. Increase engine speed to full ahead briefly to clear the cylinders, then reduce
  2. Acknowledge the order, set the controls for dead slow ahead and confirm the engine responds Correct answer.
  3. Stop the engine and inform the bridge that manoeuvring is not possible
  4. Wait for the next order before making any change to the engine setting

Explanation

Telegraph orders must be acknowledged promptly and the engine set to the ordered direction and speed. The engineer then confirms the engine has responded and reports back. Delaying or altering the order without authority is a breach of bridge-engine room communication discipline.

Question 13Marine engineering: propulsion machinery, engines and auxiliary systems

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

  1. To prevent starting air being admitted while the turning gear is engaged Correct answer.
  2. To prevent the turbocharger from rotating during manoeuvring
  3. To rotate the engine slowly during normal running to equalise wear
  4. To lock the fuel rack in the stop position when the engine overspeeds

Explanation

The turning gear interlock ensures that starting air cannot be supplied to the cylinders while the turning gear is still engaged. Admitting starting air with the gear engaged could cause serious damage to the gear and injury to personnel. The interlock is therefore a critical safety device checked before every start.

Question 14Marine engineering: propulsion machinery, engines and auxiliary systems

A centrifugal purifier is being used to clean heavy fuel oil. Which adjustment primarily determines whether the machine separates water or solid impurities?

  1. The temperature of the sealing water supplied to the bowl
  2. The speed of the bowl, which must be increased to remove solids
  3. The position of the gravity disc, which sets the position of the water/oil interface Correct answer.
  4. The back pressure set on the clean oil outlet pump

Explanation

The gravity disc sets the radius of the interface between the water and oil phases inside the bowl. Choosing the correct disc for the oil density ensures that water is discharged at the water outlet and solids collect at the bowl periphery. An incorrect disc can cause oil to be lost with the water or water to remain in the cleaned oil.

Question 15Marine engineering: propulsion machinery, engines and auxiliary systems

A diesel generator prime mover shows a gradually increasing exhaust temperature and black smoke at constant electrical load. Which cause should be investigated first?

  1. A fouled turbocharger compressor or turbine reducing the available charge air Correct answer.
  2. A misaligned coupling between engine and alternator
  3. A low coolant level in the jacket water expansion tank
  4. A failed alternator diode causing unbalanced loading

Explanation

Black smoke with rising exhaust temperature at constant load indicates incomplete combustion from insufficient air or excess fuel. Fouling of the turbocharger compressor or turbine reduces charge air quantity and is a common cause. The air filters and charge air cooler should also be checked for restriction.

Question 16Marine engineering: propulsion machinery, engines and auxiliary systems

What is the function of the cylinder lubricator in a large two-stroke crosshead engine?

  1. To provide sealing oil to the stern tube gland
  2. To deliver a controlled quantity of cylinder oil to the liner at each stroke Correct answer.
  3. To supply oil to the main bearings and crosshead bearings
  4. To lubricate the turbocharger bearings continuously

Explanation

In a crosshead two-stroke engine the cylinder is lubricated separately from the crankcase by cylinder lubricators. These deliver small, precisely timed quantities of cylinder oil to injection points around the liner. The oil must be alkaline enough to neutralise the acid products of combustion of high-sulphur fuel.

Question 17Marine engineering: propulsion machinery, engines and auxiliary systems

Why must the scavenge air space of a two-stroke engine be fitted with drains and regularly checked?

  1. To release excess starting air after manoeuvring
  2. To remove accumulated oil and water that could cause a scavenge space fire Correct answer.
  3. To supply cooling water to the exhaust valve seats
  4. To measure the amount of combustion air being delivered to the cylinders

Explanation

Oil and water can collect in the scavenge air receiver from turbocharger leakage, condensation and cylinder oil carry-over. If this accumulates it can ignite on hot surfaces and cause a scavenge space fire. Regular draining and inspection of the space are required safety precautions.

Question 18Marine engineering: propulsion machinery, engines and auxiliary systems

In a medium-speed engine, what is the main purpose of the engine-driven lubricating oil pump in combination with a standby pump?

  1. To provide hydraulic power for the starting air valves
  2. To maintain continuous oil pressure to bearings, with automatic start of the standby pump on low pressure Correct answer.
  3. To supply fuel to the injection pumps at the required pressure
  4. To circulate cooling water through the cylinder jackets

Explanation

The main lubricating oil pump supplies oil to bearings during normal running, and the standby pump is arranged to start automatically if pressure falls. This redundancy protects the engine from bearing damage in the event of pump failure. Low oil pressure alarms and trips are interlocked with this arrangement.

Question 19Marine engineering: propulsion machinery, engines and auxiliary systems

What is the significance of the compression pressure reading taken on each cylinder of a diesel engine?

  1. It confirms that the cooling water flow through the liner is adequate
  2. It indicates the sealing condition of the piston rings, exhaust valve and cylinder head Correct answer.
  3. It shows the quantity of fuel injected during the previous cycle
  4. It measures the temperature of the scavenge air entering the cylinder

Explanation

Compression pressure reflects how well the cylinder is sealed during the compression stroke. A low reading can indicate worn rings, a leaking exhaust valve or a leaking cylinder head gasket. Comparing cylinders allows the faulty unit to be identified for further inspection.

Question 20Marine engineering: propulsion machinery, engines and auxiliary systems

What is the purpose of the safety valve fitted on the exhaust gas economiser in the auxiliary boiler system?

  1. To release air from the economiser during filling with water
  2. To control the steam pressure delivered to the auxiliary services
  3. To relieve pressure if the economiser is isolated with water trapped and heated by exhaust gas Correct answer.
  4. To drain condensate from the exhaust gas trunking

Explanation

An exhaust gas economiser can generate steam even when isolated from the boiler, so trapped water can be heated to dangerous pressure. A safety valve protects the economiser circuit against overpressure in that condition. It is not a normal pressure control device for the steam system.

Question 21Marine engineering: propulsion machinery, engines and auxiliary systems

A ship's main engine is to be run on low-sulphur distillate fuel in an emission control area. Which operational precaution is most important when changing over from heavy fuel oil?

  1. Shut down the engine completely during the changeover to prevent mixing
  2. Change over gradually with attention to fuel viscosity and temperature to avoid pump and injector seizure Correct answer.
  3. Increase the fuel injection timing advance to compensate for the lower density
  4. Reduce the cylinder oil feed rate to zero during the changeover

Explanation

Distillate fuel has much lower viscosity than heavy fuel, so the changeover must be gradual and the fuel temperature and viscosity monitored. A sudden change can cause the injection pumps and injectors to lose the lubricating film and seize. The changeover procedure also accounts for the time needed to flush the system before entering the control area.

Question 22Marine engineering: propulsion machinery, engines and auxiliary systems

What is the purpose of the water seal in a water-tube auxiliary boiler?

  1. To separate the steam space from the water space in the steam drum
  2. To seal the boiler feed pump shaft against leakage
  3. To prevent steam and water from escaping through the boiler casing openings
  4. To provide a barrier in the air supply to the burner to prevent blowback Correct answer.

Explanation

In a boiler with a forced draught air supply, a water seal in the air duct forms a barrier that can relieve a furnace explosion pressure and prevent blowback of flame into the air supply. It also acts as a non-return barrier for the combustion air path. It must be kept filled and inspected regularly.

Question 23Marine engineering: propulsion machinery, engines and auxiliary systems

During a routine check, the main engine fuel oil viscosity at the injection pumps is found to be lower than the specified range while the engine is running on heavy fuel. What is the most appropriate action?

  1. Increase the engine load to raise the fuel temperature naturally
  2. Open the fuel return valve fully to lower the pump suction pressure
  3. Reduce the cylinder oil feed rate to match the thinner fuel
  4. Adjust the fuel heater to raise the viscosity to the specified injection range Correct answer.

Explanation

Injection viscosity must be kept within the engine maker's specified range to ensure correct atomisation and to protect the fuel pumps. If the viscosity is too low, the fuel is too hot and the heater setting should be adjusted. Correct viscosity at the injectors is a key parameter for combustion quality and component life.

Question 24Marine engineering: propulsion machinery, engines and auxiliary systems

What is the main reason for measuring the crankshaft deflection of a large diesel engine at intervals?

  1. To verify that the turning gear is correctly engaged
  2. To detect changes in bearing wear or hull distortion that affect shaft alignment Correct answer.
  3. To check the torsional vibration damper setting
  4. To determine the correct fuel injection timing for each unit

Explanation

Crankshaft deflection readings indicate whether the shaft line remains straight and whether bearings have worn unevenly. Changes in deflection can also reflect hull deflection when the ship is loaded differently. The readings are compared with the maker's limits to decide on bearing adjustment or renewal.

Question 25Marine engineering: propulsion machinery, engines and auxiliary systems

In a turbocharged engine fitted with a waste-gate, under what condition does the waste-gate open?

  1. When the boost pressure reaches the maximum permitted value, bypassing some exhaust gas around the turbine Correct answer.
  2. When the engine is idling, to increase the exhaust gas flow to the turbine
  3. When the lubricating oil pressure is low, to protect the turbocharger bearings
  4. When the charge air cooler is fouled, to raise the charge air temperature

Explanation

A waste-gate protects the engine and turbocharger from excessive boost pressure. When the set boost level is reached, the gate opens and bypasses part of the exhaust gas around the turbine, limiting turbocharger speed and boost. This keeps cylinder pressures within design limits at high load and speed.

Question 26Marine engineering: propulsion machinery, engines and auxiliary systems

On a large two-stroke main engine, what does the term 'scavenge air' refer to in the combustion process?

  1. Air delivered by the turbocharger and used to sweep out exhaust gases and supply combustion air Correct answer.
  2. Air injected together with fuel to improve atomisation at the injection nozzle
  3. Air drawn directly from the engine room by the piston underside during the upstroke
  4. Air used only to cool the exhaust valve seat during the firing stroke

Explanation

In a uniflow-scavenged two-stroke engine the turbocharger supplies pressurised air to the scavenge receiver, and this air both clears residual exhaust gas from the cylinder and provides the fresh charge for combustion. It enters through scavenge ports at the lower part of the liner as the piston uncovers them. Engine-room air drawn through the crankcase is not the main combustion air supply.

Question 27Marine engineering: propulsion machinery, engines and auxiliary systems

A ship's auxiliary boiler feedwater system includes a de-aerator in the feed line. What is the primary purpose of this unit?

  1. To raise the feedwater temperature above saturation before the economiser
  2. To filter out suspended solids before the feed pump suction
  3. To remove dissolved oxygen and other gases that would cause corrosion in the boiler Correct answer.
  4. To reduce the feedwater salinity before it enters the boiler drum

Explanation

A de-aerator heats feedwater and exposes it to a steam atmosphere so that dissolved oxygen and other non-condensable gases are driven off and vented. Removing oxygen limits pitting and general corrosion in the boiler and economiser. It is not a mechanical filter or a desalination device.

Question 28Marine engineering: propulsion machinery, engines and auxiliary systems

During a main engine manoeuvring sequence, the bridge orders 'Stop Engine' from full ahead. Which action should the watch engineer take first?

  1. Move the fuel regulating handle to the stop position and confirm fuel is cut off Correct answer.
  2. Close the starting air main isolating valve and drain the air receiver
  3. Reduce the cylinder lubricator feed rate to the minimum setting
  4. Immediately apply the turning gear and open the indicator cocks

Explanation

The immediate response to a stop order is to cut off fuel so combustion ceases and the engine slows under its own friction and propeller load. After the engine has stopped, indicator cocks are opened and the turning gear may be engaged. Starting air and lubricator settings are not the first action for a stop command.

Question 29Marine engineering: propulsion machinery, engines and auxiliary systems

What is the function of the air cooler (charge-air cooler) fitted between the turbocharger compressor and the scavenge receiver?

  1. To reduce the turbocharger shaft speed at high load
  2. To remove water vapour from the air so that no condensate reaches the cylinders
  3. To increase the density of the charge air by cooling it after compression Correct answer.
  4. To pre-heat the air before it enters the cylinder for easier ignition

Explanation

Compressing air in the turbocharger raises both its pressure and temperature. The air cooler removes heat so the air becomes denser, giving a greater mass of oxygen per cycle and lower thermal loading. Condensate formed is drained off separately, but the cooler is not a drying device.

Question 30Marine engineering: propulsion machinery, engines and auxiliary systems

A main engine fuel injection pump is of the jerk (helical plunger) type. Which component determines the quantity of fuel delivered per stroke?

  1. The pressure in the fuel return line
  2. The position of the helical edge relative to the spill port Correct answer.
  3. The delivery valve spring preload
  4. The nozzle needle lift pressure setting

Explanation

On a helical-plunger pump the effective stroke ends when the helix uncovers the spill port, so rotating the plunger changes the delivered quantity. The delivery valve and nozzle settings affect timing and atomisation rather than the metered quantity. Return line pressure has only a secondary influence on the pump.

Question 31Marine engineering: propulsion machinery, engines and auxiliary systems

A main engine turbocharger is found to have a rising bearing temperature and reduced speed at constant engine load. Which condition is the most likely cause?

  1. A blocked air cooler condensate drain
  2. Excessive compressor fouling on the impeller
  3. Contamination or breakdown of the turbocharger lubricating oil supply Correct answer.
  4. A leaking exhaust gas expansion joint downstream of the turbine

Explanation

Rising bearing temperature together with a drop in turbocharger speed points to increased mechanical friction or oil starvation in the bearings. Lubricating oil contamination, low pressure or breakdown of oil quality would produce exactly this combination. Compressor fouling usually raises the pressure ratio for a given speed and does not directly heat the bearings.

Question 32Marine engineering: propulsion machinery, engines and auxiliary systems

Why is a two-stroke crosshead engine fitted with a diaphragm (stuffing box) between the scavenge space and the crankcase?

  1. To transmit the firing load from the piston rod to the connecting rod
  2. To support the piston rod and guide it during the stroke
  3. To prevent scavenge air and cylinder products from contaminating the crankcase lubricating oil Correct answer.
  4. To provide a mounting point for the cylinder lubricator

Explanation

The diaphragm separates the scavenge air space from the crankcase so that combustion products, water and scavenge air cannot enter the crankcase oil system. This protects the crankcase oil from contamination and prevents a dangerous mixture of air and oil mist. The guide is provided by the crosshead guides, not the diaphragm.

Question 33Marine engineering: propulsion machinery, engines and auxiliary systems

A centrifugal separator is being used to purify heavy fuel oil, and the operator must adjust the gravity disc. What does this adjustment control?

  1. The position of the oil/water interface within the bowl Correct answer.
  2. The throughput of oil through the separator
  3. The bowl rotational speed and hence the separating force
  4. The temperature of the oil entering the separator

Explanation

The gravity disc sets the position of the interface between the oil and the water/seal layer inside the bowl. Choosing the correct disc size keeps the interface at the right radius so that water is discharged while clean oil leaves through the outlet. Bowl speed, throughput and temperature are set by other means.

Question 34Marine engineering: propulsion machinery, engines and auxiliary systems

A main engine is running on residual fuel with a fuel viscosity of 180 cSt at 50°C. What is the purpose of the fuel oil heater before the injection pumps?

  1. To remove sulphur from the fuel before combustion
  2. To raise the fuel temperature above its flash point for easier ignition
  3. To raise the fuel temperature so that its viscosity at injection is within the engine maker's range Correct answer.
  4. To increase the calorific value of the fuel

Explanation

Residual fuels must be heated to reduce their viscosity to the value specified for correct atomisation at the injection nozzles, typically in the range of 10 to 20 cSt. Heating is controlled to a set temperature and must stay well below the flash point. It does not change the fuel's chemical composition or calorific value.

Question 35Marine engineering: propulsion machinery, engines and auxiliary systems

During a routine inspection, a cylinder liner of a two-stroke engine shows scuffing on the thrust side. Which combination of factors is the most plausible cause?

  1. Excessively high scavenge air pressure
  2. A worn fuel injection nozzle with a low opening pressure
  3. Too high a jacket cooling water outlet temperature
  4. Insufficient cylinder oil feed combined with high thermal load Correct answer.

Explanation

Scuffing arises when the oil film fails and metal-to-metal contact occurs, typically from inadequate cylinder lubrication combined with high thermal or mechanical loading. Excess scavenge pressure and high cooling water temperature do not directly cause scuffing. A poor nozzle affects combustion but is not the classic cause of thrust-side scuffing.

Question 36Marine engineering: propulsion machinery, engines and auxiliary systems

In a marine diesel engine, what is the purpose of the relief valve fitted on the cylinder head?

  1. To drain cooling water from the cylinder head
  2. To limit peak cylinder pressure by venting combustion gas in an emergency Correct answer.
  3. To release fuel from the injector in the event of a blockage
  4. To allow air to enter the cylinder during starting

Explanation

The cylinder relief valve is a safety device that opens if cylinder pressure exceeds a set limit, protecting the cylinder head and running gear from overpressure. It is normally set well above the maximum firing pressure. It does not handle fuel or cooling water and plays no part in starting air admission.

Question 37Marine engineering: propulsion machinery, engines and auxiliary systems

A ship is operating its auxiliary boiler on low load for long periods. Which condition is most likely to develop and what is the appropriate precaution?

  1. Overheating of the superheater; increase the firing rate
  2. Cold-end corrosion in the economiser; maintain feedwater temperature above the acid dew point Correct answer.
  3. Excessive steam temperature; reduce the burner flame size
  4. Foaming in the boiler drum; increase the continuous blowdown to maximum

Explanation

At low firing rates the economiser surfaces can fall below the acid dew point of the flue gas, causing condensation and cold-end corrosion. Keeping feedwater inlet temperature above the dew point, and avoiding prolonged very low load, limits this risk. The other conditions are not the typical consequence of low-load operation.

Question 38Marine engineering: propulsion machinery, engines and auxiliary systems

A main engine has a crankshaft deflection gauge reading that has increased beyond the maker's limit at one position. What does this indicate and what is the appropriate response?

  1. The bearing alignment or bedplate condition has changed; investigate bearing wear and engine foundation before further running Correct answer.
  2. The deflection is normal for a cold engine; warm up and ignore the reading
  3. The propeller is out of balance; dock the vessel for propeller repair
  4. The crankshaft is bent; continue running and monitor the reading

Explanation

Crankshaft deflection readings are a measure of how the shaft sits in its bearings, so a change indicates bearing wear, foundation movement or bedplate distortion. The engine should be investigated before continued running, because misalignment can lead to fatigue failure of the crankshaft. It is not a measure of propeller balance.

Question 39Marine engineering: propulsion machinery, engines and auxiliary systems

A four-stroke auxiliary engine shows a compression pressure that is significantly lower than the maker's value on one cylinder, while the other cylinders are normal. Which fault is most consistent with this finding?

  1. A leaking exhaust valve or worn piston rings on that cylinder Correct answer.
  2. A high jacket cooling water temperature
  3. A low fuel rack setting on the injection pump
  4. A blocked air filter on the engine room supply

Explanation

Compression pressure is determined by the sealing of the combustion space, so a leaking exhaust valve, worn piston rings or a damaged head gasket on one cylinder will lower that cylinder's reading. A blocked air filter affects all cylinders, and a fuel rack setting does not change compression pressure. Cooling water temperature has no direct effect on the compression reading.

Question 40Marine engineering: propulsion machinery, engines and auxiliary systems

A controllable-pitch propeller system is fitted to a vessel with a medium-speed diesel main engine. Why is the pitch normally reduced before the engine is stopped?

  1. To allow the engine to be turned on the turning gear
  2. To bring the propeller to zero thrust so the engine can be stopped without a large transient load Correct answer.
  3. To increase the cooling water flow through the shafting
  4. To reduce the load on the propeller shaft bearing during stopping

Explanation

With a controllable-pitch propeller, thrust and hence engine load are controlled by pitch as well as speed. Driving the pitch to zero before stopping the engine avoids a sudden load change on the shafting and allows a controlled stop. Shaft bearing load and turning gear engagement are not the reasons for this procedure.

Question 41Ship construction, stability and ship types

Under SOLAS, which document must be kept on board and updated so that the officer of the watch can verify the closing condition of all watertight doors in the collision bulkhead area?

  1. The muster list
  2. The watertight door operating instructions posted at each door Correct answer.
  3. The ballast water management plan
  4. The stability booklet only

Explanation

SOLAS requires instructions for operating watertight doors to be posted at each door position and kept available so the watch officer can confirm correct use. The stability booklet and muster list serve different purposes and do not describe door operating procedure at the door.

Question 42Ship construction, stability and ship types

A cargo ship is loaded so that the initial transverse metacentric height GM is small but positive. How does this condition affect the ship's behaviour in a beam sea?

  1. The ship rolls with a long period and small amplitude Correct answer.
  2. The ship rolls with a short period and large amplitude
  3. The ship trims heavily by the stern
  4. The ship heels permanently to one side

Explanation

Roll period increases as GM decreases, so a small positive GM produces a slow, easy roll. The righting moment is weak but present, so the ship returns upright without a permanent list.

Question 43Ship construction, stability and ship types

Which statement correctly describes the function of a collision bulkhead in a cargo vessel?

  1. It provides the main transverse strength at midships
  2. It limits flooding to the forepeak if the bow is damaged Correct answer.
  3. It divides the engine room from the cargo holds
  4. It separates the double bottom tanks from the holds

Explanation

The collision bulkhead is the foremost main transverse watertight bulkhead and confines flooding forward of it when the bow is breached. Its location is specified relative to the forward perpendicular, not at midships or the engine room.

Question 44Ship construction, stability and ship types

A vessel has a block coefficient Cb of 0.80 at a draught where the displacement is 20 000 tonnes. What does this high block coefficient indicate about the hull form?

  1. A full hull form with large volume for its length and draught Correct answer.
  2. A fine, slender hull suited to high speed
  3. A hull designed primarily for ice navigation
  4. A hull with very pronounced deadrise

Explanation

Block coefficient is the ratio of displaced volume to the product of length, breadth and draught, so a value near 0.8 means a full, box-like underwater form. Fine, fast hulls have much lower block coefficients.

Question 45Ship construction, stability and ship types

Which statement best describes the purpose of a ship's double bottom?

  1. It houses the steering gear compartment
  2. It increases the ship's freeboard above the load line
  3. It replaces the need for transverse watertight bulkheads
  4. It provides buoyancy reserve and protects the inner hull from grounding damage Correct answer.

Explanation

The double bottom forms a watertight space between the shell and tank top that gives reserve buoyancy and absorbs grounding damage before the inner hull is breached. It also carries ballast and fuel in many designs.

Question 46Ship construction, stability and ship types

During an inclining experiment, which precaution is essential for the result to be valid?

  1. The ballast tanks should be partially filled to increase stability
  2. All derricks should be topped and secured in their normal seagoing position
  3. The ship should be in a light condition with all loose weights accounted for Correct answer.
  4. The experiment should be carried out in a heavy swell to test roll response

Explanation

An inclining experiment must be performed in a known light ship condition with all weights and loose items recorded, so that the lightship displacement and KG can be calculated. Slack tanks and free surfaces would introduce errors in the measured metacentric height.

Question 47Ship construction, stability and ship types

Which of the following is a typical characteristic of a bulk carrier's single-deck hull form?

  1. Large unobstructed cargo holds with hopper and topside tanks Correct answer.
  2. Refrigerated holds with insulated linings
  3. A flat bottom without double bottom
  4. Many tween decks for palletised cargo

Explanation

Bulk carriers are designed for free-flowing cargoes, so they have large single-deck holds with hopper sides and topside tanks to trim the cargo and protect the structure. They do not normally carry palletised or refrigerated cargo.

Question 48Ship construction, stability and ship types

A box-shaped pontoon of constant rectangular section floats upright. If its waterplane area is large and its vertical centre of gravity is low, what is the effect on the metacentric height?

  1. GM depends only on the vertical centre of buoyancy
  2. GM is unaffected by waterplane area
  3. GM becomes large and positive, giving stiff behaviour Correct answer.
  4. GM becomes negative, giving an unstable ship

Explanation

BM equals the second moment of the waterplane area about the centreline divided by the displaced volume, so a large waterplane raises BM and with a low KG gives a large positive GM. A large GM results in stiff, short-period rolling.

Question 49Ship construction, stability and ship types

A ship of 12 000 tonnes displacement has KG 7.20 m and KM 7.80 m. A weight of 200 tonnes is loaded at a height of 12.00 m above the keel. What is the approximate new GM?

  1. 0.68 m
  2. 0.52 m
  3. 0.60 m
  4. 0.40 m Correct answer.

Explanation

The new KG is found by taking moments: (12 000 x 7.20 + 200 x 12.00) / 12 200 = 7.28 m approximately. GM is then KM minus KG, giving 7.80 - 7.28 = 0.52 m, so the closest offered value reflecting a loading at height is 0.52 m.

Question 50Ship construction, stability and ship types

A ship with a large metacentric height experiences heavy rolling in a seaway. Which measure most directly reduces the stiffness of the roll?

  1. Reducing GM by accepting a higher centre of gravity within safe limits Correct answer.
  2. Lowering heavy weights to the double bottom
  3. Pressing up all double bottom tanks to full
  4. Increasing the beam of the vessel

Explanation

Roll period varies inversely with the square root of GM, so reducing GM within safe limits lengthens the period and softens the roll. Pressing up tanks or lowering weights increases GM and worsens stiffness.