USCG Chief Engineer Offshore Supply Vessels (OSE01)

On a medium-speed marine diesel driving an OSV main generator, what is the primary purpose of fuel injection timing?

• ATo control jacket-water outlet temperature
• BTo regulate scavenge-air mass flow into the cylinder
• CTo set the crank angle at which fuel begins to burn so peak pressure occurs shortly after…
• DTo set main-bearing lube-oil pressure

A diesel engine will not turn on starting air even though bottle pressure is normal and the air-start distributor appears to cycle. The most likely cause is that the:

• ACooling-water expansion tank is slightly low
• BTurning gear is still engaged
• CDay-tank fuel viscosity is higher than design
• DCrankcase oil level is slightly above the high mark

In a four-stroke-cycle diesel, how many crankshaft revolutions complete one full cycle in each cylinder?

• AOne revolution (360 degrees)
• BOne-half revolution (180 degrees)
• CThree revolutions (1080 degrees)
• DTwo revolutions (720 degrees)

What is the chief function of scavenging on a two-stroke marine diesel?

• ATo inject fuel at the correct crank angle
• BTo remove burned gases from the cylinder and replace them with fresh air
• CTo circulate lube oil to the crosshead
• DTo cool the injector tip between firings

The fuel oil service (day) tank on a marine diesel installation is provided to:

• AHold the vessel's entire fuel bunker in one place
• BKeep a settled, treated quantity of fuel ready for immediate use by the engine
• CSeparate lube oil from the fuel before injection
• DSupply starting air when the receivers run low

Exhaust valve rotators (rotocaps) are fitted on many four-stroke marine diesels to:

• AHold each valve at a fixed angular position for accurate timing
• BTurn the valve slightly on every lift so seat deposits are wiped and wear is spread aroun…
• CIncrease valve lift automatically at high load
• DCirculate jacket water through the valve stem

The primary purpose of a charge-air cooler (intercooler) on a turbocharged diesel is to:

• AIncrease exhaust-gas temperature for aftertreatment
• BCool compressed charge air so denser air enters the cylinders
• CHeat fuel oil to injection viscosity
• DCondense water vapor from the crankcase

An engine-driven jacket-water circulating pump is backed up by a motor-driven standby pump mainly so that:

• AThe engine can be run for short periods with no coolant at all
• BCirculation can be maintained when the engine is stopped or the attached pump fails
• CSea water can be admitted directly into the engine jackets
• DJacket-water pressure can be raised above fuel injection pressure

White smoke during a cold diesel start that clears as the engine warms most often indicates:

• ASevere main-bearing failure
• BCondensed water vapor and incomplete combustion while cold
• CExcessive cylinder lube-oil feed rate only
• DA crankcase explosion in progress

The main purpose of a diesel engine lube-oil filter is to:

• ARaise oil pressure above the relief-valve setting
• BRemove particulate contaminants that would damage bearings and journals
• CCool the oil below ambient sea temperature
• DMeter cylinder oil to each liner

If an oil-mist detector alarms on a medium-speed diesel, the chief engineer's immediate priority action is to:

• AOpen crankcase doors to ventilate the mist
• BSlow or stop the engine per procedure and keep crankcase doors closed
• CIncrease fuel rack to burn off the mist
• DBypass the detector and continue at full load

A rising exhaust temperature on one cylinder with falling peak pressure often indicates:

• ALate or incomplete combustion in that cylinder
• BExcessive scavenge-air pressure only
• CA stuck-open jacket-water thermostat
• DNormal equalized combustion

On suspected scavenge-fire conditions (rising scavenge temperature, smoke at scavenge drains), the preferred immediate action is to:

• AIncrease fuel to all cylinders to clear deposits
• BReduce load or stop, secure fuel to affected units, and apply the manufacturer's firefigh…
• COpen scavenge doors wide while running
• DShut off all lube oil immediately while at full speed

Mean effective pressure (MEP) derived from an indicator diagram is primarily used to:

• ASet jacket-water chloride limits
• BEstimate cylinder work and compare power among units
• CCalibrate the reverse-power relay
• DMeasure bilge oil content in ppm

A sudden drop in main-engine lube-oil pressure with rising oil temperature most strongly suggests:

• AA cold start with thick oil only
• BBearing wipe, dilution, pump failure, or major internal leakage requiring immediate load…
• CNormal automatic viscosity control
• DExcessive charge-air cooler efficiency

Why are starting-air bottles fitted with relief valves and kept free of oil accumulation?

• AOil improves compressor efficiency
• BOil in high-pressure air can form an explosive mixture and relief valves limit overpressu…
• CRelief valves meter fuel to the injectors
• DBottles must never be depressurized for maintenance

Turbocharger surge is most likely when:

• AAirflow suddenly falls while compressor speed remains high
• BJacket water is slightly cool
• CThe engine is at steady full load with clean filters
• DThe governor is in isochronous mode only

On a controllable-pitch propeller plant, shaft RPM can remain nearly constant while ship speed changes primarily because:

• AFuel is shut off whenever speed changes
• BBlade pitch is varied to change thrust at essentially constant shaft speed
• CThe turning gear sets ship speed
• DOnly reverse reduction gears can change thrust

A diesel shows steadily rising crankcase pressure and mist without an oil-mist detector trip yet. The management-level concern is:

• AImproved ring sealing
• BDeveloping blow-by or hot spot that can progress to crankcase explosion
• CNormal turbocharger boost only
• DThat bilge pumps are running too often

After a main-bearing high-temperature alarm, the safest first management action is to:

• AIncrease RPM to throw more oil into the bearing
• BReduce load/speed promptly and prepare to stop while monitoring oil pressure and temperat…
• CAdd cold seawater directly into the crankcase
• DDisable the alarm and finish the voyage at full load

Cylinder oil feed rate on a crosshead diesel is primarily adjusted based on:

• AGenerator reactive load only
• BFuel sulfur, load, and the maker's feed-rate guidance for liner protection
• CMARPOL Annex V garbage categories
• DBattery specific gravity

Fuel oil viscosity at the injectors is controlled mainly to:

• AEnsure proper atomization and spray pattern for combustion
• BRaise flash point above 150°C
• CEliminate the need for purifiers
• DIncrease cetane number permanently

A stuck-open fuel injector on one cylinder typically produces:

• ALower exhaust temperature and higher peak pressure on that unit
• BHigh exhaust temperature, knocking or roughness, and possible white/black smoke
• CImmediate reverse-power trip of the switchboard
• DZero jacket-water flow

Indicated power of a multi-cylinder diesel is most directly related to:

• AMEP, cylinder dimensions, number of working cycles per unit time, and number of cylinders
• BOnly the alternator nameplate kVA
• COnly seawater pump RPM
• DOnly the OWS 15 ppm alarm setpoint

A four-stroke diesel cylinder has mean effective pressure of 12 bar, bore 0.30 m, and stroke 0.40 m. Indicated work per cycle for that cylinder is best computed as:

• AMEP × piston area × stroke
• BMEP divided by RPM only
• CBore divided by stroke times 600
• DGenerator voltage times current

During a crash stop with CPP, the engineering management priority is to:

• AIgnore pitch demand and maximize fuel rack
• BCoordinate pitch reduction/astern demand with engine load limits and thermal limits to av…
• COpen crankcase doors for cooling
• DTrip all generators immediately regardless of hotel load

After a scavenge fire is extinguished, before restoring full load the chief engineer should ensure:

• AScavenge spaces are inspected, residual fire risk is clear, and systems are restored per…
• BFuel sulfur is increased to clean deposits
• CAll crankcase relief valves are wired shut
• DOil mist detectors are permanently bypassed

A diesel burns 360 kg/h of fuel with lower calorific value 42,000 kJ/kg and develops 1,800 kW brake power. Approximate brake thermal efficiency is:

• AAbout 14%
• BAbout 86%
• CAbout 43%
• DAbout 100%

A chief engineer compares two sister engines: Engine A has higher peak pressure but lower exhaust temperature than Engine B at the same load. The most likely interpretation is:

• AEngine A has earlier, more complete combustion; Engine B is burning late
• BEngine A has no fuel; Engine B is normal
• CEngine B has higher compression ratio always
• DBoth engines have identical injection timing

When securing a medium-speed diesel after heavy load, why is a cool-down period at reduced load often required?

• ATo raise exhaust temperature rapidly
• BTo equalize and remove residual heat from turbochargers, pistons, and liners before stop
• CTo fill the crankcase with seawater
• DTo trip the reverse-power relay deliberately

On a shipboard AC generator, frequency is primarily determined by:

• AField excitation current alone
• BRotor speed and the number of poles
• CPower-factor meter reading only
• DBattery float voltage

Generator terminal voltage is primarily adjusted by:

• AGovernor fuel rack only
• BField excitation
• CBilge pump staging
• DLube-oil temperature

When paralleling two AC generators, the synchroscope should indicate closing of the breaker near the:

• A6 o'clock position
• B3 o'clock position only
• C12 o'clock position
• DAny random position

Real power (kW) shared between paralleled generators is primarily adjusted by:

• AField excitation alone
• BGovernor / prime-mover fuel settings
• CGround-detection lamps only
• DShore-power transformer taps

Reactive power (kVAR) shared between paralleled generators is primarily adjusted by:

• AGovernor droop only
• BField excitation / AVR settings
• CFuel oil viscosity
• DCPP pitch alone

An interlock between the shore-power connection and the ship's generator breakers exists to:

• ALet both sources feed the bus together without any synchronizing
• BPrevent an unsynchronized generator and the shore supply from being closed onto the same…
• CRaise the available fault current at the switchboard
• DTake the ground-detection system out of service while in port

On an ungrounded shipboard distribution system, ground-detection lamps that show one lamp dark and the others bright typically indicate:

• ANormal balanced condition
• BA ground fault on the phase with the dark lamp
• CAll generators offline
• DCorrect paralleling at 6 o'clock

A motor controller thermal overload device primarily protects against:

• AShort-duration inrush only
• BSustained overcurrent that would overheat the motor windings
• CLoss of excitation on the generator
• DLow jacket-water temperature

Compared with across-the-line starting, a reduced-voltage motor starter is used mainly to:

• AIncrease locked-rotor current
• BLimit starting current and mechanical shock
• CEliminate the need for overload relays
• DRaise supply frequency

Non-linear loads such as variable-frequency drives degrade shipboard power quality mainly by:

• APulling bus frequency below the generator's rated 60 Hz
• BInjecting harmonic currents that distort the voltage waveform and overheat generators, ca…
• CReversing the phase sequence of the switchboard
• DRemoving the need for generator field excitation

Lead-acid battery rooms require ventilation primarily because charging can produce:

• ANitrogen only
• BHydrogen gas that can form an explosive mixture
• COxygen-free inert atmosphere automatically
• DCO2 total-flooding agent

A transformer is used on board primarily to:

• AConvert AC frequency from 60 Hz to 50 Hz without electronics
• BChange AC voltage level by electromagnetic induction
• CStore DC energy like a battery
• DMeasure oil mist concentration

A silicon diode rectifier converts:

• ADC to higher-frequency AC without filters
• BAC to DC by allowing current in one direction
• CHydraulic pressure to voltage
• DFuel oil viscosity to current

If two paralleled generators have equal kW but one has much higher field current, you would expect:

• AThat machine to supply more lagging kVAR (or absorb less)
• BImmediate reverse-power trip always
• CFrequency to double
• DJacket water to boil

Preferential tripping on an OSV switchboard is intended to:

• ATrip nonessential loads to preserve power for propulsion and essential services during ov…
• BAlways trip the main engines first
• CDisable ground detection
• DIncrease shore-power voltage

A PID controller's integral term is primarily used to:

• APredict future error only
• BEliminate steady-state offset by accumulating past error
• CMeasure shaft torque directly
• DReplace the need for sensors