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单选题
When adding oil to a refrigeration system, precautions must be taken to ensure that （）.
A
the compressor suction pressure is not too high
B
all air is purged from the pump and charging fittings
C
the high pressure cutout switch is held open to prevent accidental starting
D
the condenser is completely shutdown first
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When adding oil to a refrigeration system, precautions must be taken to ensure thatA.the compressor suction pressure is not too highB.all air is purged from the pump and charging fittingsC.the high pressure cutout switch is held open to prevent accidental startingD.the condenser is completely shutdown first
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Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur when the compressorA.has run continuously for a long periodB.suction pressure is below normalC.oil level is below normalD.starts after a long idle period
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Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause______.A.carbon deposits on the compressor suction valvesB.the evaporator temperature to increaseC.rapid corrosion of the thermal expansion valveD.no operating problems
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单选题Purging air from a hydraulic system is necessary when（）A
adding small amounts of oil to the systemB
the system has been overheatedC
the system has been drained and then filled with new oilD
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单选题A refrigeration system compressor crankcase is sweating or unusually coldThis is an indication of（）.A
a shortage of refrigerant in the systemB
air in the systemC
an accumulation of liquid refrigerant in the crankcaseD
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单选题Refrigeration system compressor crankcase sweating is an indication of （）.A
insufficient lube oil circulating through the systemB
excessive circulation of lube oil through the systemC
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单选题When adding oil to a refrigeration system, precautions must be taken to ensure that （）.A
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the condenser is completely shutdown first
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单选题When it is necessary to open a refrigeration system for repairs and the system will be open for more than a few minutes, the open ends of the system should be （）.A
dehydratedB
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pluggedD
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单选题Moisture is removed from a refrigeration system by（）.A
bleeding refrigerant from the condenserB
opening a drain petcock on the oil separatorC
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单选题Which of the following statements is correct concerning a typical shipboard multi-coil refrigeration system?（）A
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单选题When normal operating pressure is applied to the hydraulic oil used in a high-pressure system, the oil （）.A
viscosity will decreaseB
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考题
单选题Crankcase sweating in a refrigeration system is caused by （）.A
a stuck solenoid valveB
a shortage of refrigerantC
too much oil in circulationD
too much superheat
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单选题The accumulation of air and other non-condensable gases in a refrigeration system will （）.A
cause a loss of the liquid sealB
create a vapor lock in the liquid receiverC
collect in the condenserD
cause foaming of the oil in the crankcase
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单选题When welding or burning aboard a vessel, you must be certain that the space （）.A
is properly ventedB
contains no explosive fumesC
has no oil in the bilgesD
all of the above
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单选题Which of the listed statements is correct concerning refrigeration systems?（）A
Dehydrators must be used continuously in a refrigeration systemB
A 25 ton refrigeration system has the same cooling effect as melting 25 tons of ice in 24 hoursC
A thermostatic expansion valve is used to control refrigerated space temperatureD
The liquid receiver functions to collect and remove non- condensable gases
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单选题A purge recovery system is used in a centrifugal air conditioning or refrigeration system to （）A
purge lube oil from the liquid refrigerantB
recover water purged from the systemC
separate foul gases from the receiverD
purge non-condensable gases without losing refrigerant
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单选题Which of the following precautions must be taken if an electric immersion heater is used to keep the coolant in a diesel engine warm during the time the engine is secured?（）A
The coolant temperature must be maintained at 180℃B
The thermostatic bypass valves must be manually opened before the engine is startedC
The pressure cap must be removed while the engine is securedD
Electrical power to the heater must be secured before the cooling system is drained
考题
单选题Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur（） when the compressor.A
has continuously for a long periodB
suction pressure is below normalC
oil level is below normalD
starts after a long idle period
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单选题When running a large, low-speed, main propulsion diesel engine on heavy fuel, which of the following precautions should be observed when switching back over to diesel oil?（）A
The diesel oil must never be allowed to mix with the heavy fuelB
The temperature of the fuel from the pre–heater should be gradually reduced after switching over the three–way valveC
The heating steam to the pre-heater should be secured as soon as the diesel fuel passes through the three-way valveD
The heating steam must be secured before the diesel oil passes through the three-way valve
考题
单选题Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause （）.A
carbon deposits on the compressor suction valvesB
the evaporator temperature to increaseC
rapid corrosion of the thermal expansion valveD
no operating problems
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