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Cavitation erosion in the cooling water system of a diesel engine usually occurs at the pump impeller, and on the waterside of the （）
A . fuel nozzle holders
B . exhaust value guides
C . engine cylinder liners
D . low temperature and a low viscosity
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The pH value of water in a diesel engine closed cooling water system should be maintained between （）.
A . 60 to75
B . 80 to 95
C . 100 to 115
D . 120 to 135
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In a refrigeration system, if the cooling water to the condenser fails, the（）.
A . box temperature solenoid valve will close
B . expansion valve will close
C . compressor will shutdown
D . king valve will ope
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In a central cooling system, used in some modem ships, sea water is supplied to cool （）which will circulate to other individual cooler, greatly reducing the corrosion problems.
A . fresh water
B . sea water
C . cooling oil
D . emulsio
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Which two file types must be included in a closed database backup taken with operating system commands？（）
A . data files
B . control file
C . password file
D . online redo log files
E . initialization parameter file
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In a diesel engine cooling water system, a pH of 60 indicates a/an （）.
A . slightly acidic condition
B . slightly alkaline condition
C . overtreatment of water
D . neutral condition of water
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In a closed cooling water system, which of the problems can cause the water pressure to fluctuate?（）
A . An open vent in the cooling system
B . A fouled sea chest
C . A restricted water passage in the engine
D . Air entrained in the cooling water
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If the operating element of a thermostatic valve installed in a diesel engine cooling system malfunctions, it may result in （）
A . a low level in the engine expansion tank
B . excessively high coolant pressure
C . improper temperatures
D . malfunctioning of the jacket water heater
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Fuel injectors used in heavy fuel oil systems are usually provided with cooling to reduce（）.
A . cold corrosion of the nozzles
B . fuel viscosity for better atomization
C . carbon accumulation on the nozzles
D . fuel detonation in the cylinder
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The compressor in an air-cooled condensing refrigeration system is short cycling on the high pressure cutout switch（）
A . system is overcharged with refrigerant
B . system is low on refrigerant
C . discharge valves are leaking excessively
D . discharge valves are leaking slightly
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The main distribution duct in an air conditioning system which contains the cooling coils and filters is called the（）
A . manifold
B . condenser
C . chamber
D . plenum
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In a diesel engine cooling system, the high temperature alarm contact maker will be activated on excessively high water discharge temperature from the （）
A . raw water pump discharge
B . expansion tank outlet
C . cooling water heat exchanger
D . outlet engine jacket water outlet
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（） allows for expansion and water make up in the water cooling system.
A . A top tank
B . A head tank
C . A head valve
D . A drain tank
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The jacket water temperature in a diesel engine closed freshwater cooling system is normally controlled by （）
A . regulating the level of corrosion inhibitor in the primary cooling system
B . the level of the freshwater expansion tank
C . varying the engine load to meet temperature requirements
D . the operation of the thermostatic valve
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The expansion tank for a diesel engine closed cooling system is designed to maintain a constant head on the system and （）.
A . reduce water temperature
B . reduce water turbulence
C . provide an air cushion
D . allow for an increase in water volume as the engine warms u
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In a diesel engine exhaust system, the cooling of the exhaust gases below their dew point, will result in （）
A . increased engine back pressure
B . sulfuric acid corrosion
C . surface pitting of the turbocharger
D . moisture impingement on the turbocharger compressor blade
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In the closed cooling system, the water （）.
A . is made to circulate out of the system
B . is made to circulate within the system
C . is made circulate within the system
D . is made circulate out of the system
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The most serious effect of air trapped in a diesel engine jacket water cooling system is that it（）.
A . causes colloid suspension in the cooling water
B . reduces the capability of the lubrication system
C . can form pockets which block the flow of coolant through the system
D . leads to the scuffing of cylinder wall
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Which of the following problems can cause fluctuating pressures in the closed cooling system of a main propulsion diesel engine?（）
A . Defective temperature controls in the system
B . Cavitation in the cooling water pump
C . Opened vent in the cooling system
D . Restricted water passages in the engine
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If the coolant temperature of a closed cooling water system for a diesel engine gradually increases, the trouble usually is （）
A . a broken shaft on the freshwater pump
B . an excessive accumulation of scale exchanger
C . an incorrect thermostatic element operating range
D . lube oil in the cooling water
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An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
A . restriction in refrigerant piping
B . air and non-condensable gases in the condenser
C . water in the refrigerant
D . flooding back of liquid refrigerant from the evaporator
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A cutoff valve in the fire-main system of a ship may be closed to protect the portion of the system on an exposed deck from（）.
A . damage from crane operations
B . being used for wash down purposes
C . accidental diversion of flow to wrong location
D . freezing
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With regard to the opening and closing of watertight integrity appliances not fitted with a remote operating control or alarm system, what must the Master or person in charge of a ship enter in the logbook?
