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单选题
The unloading system on an air compressor will （）.
A
increase compressor discharge pressure on demand
B
increase compressor operating speed as necessary
C
allow the motor to turn the compressor opposed only by friction
D
reduce the compressor frictional load when starting
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考题
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单选题Air blowing from the intake air filter of an operating air compressor indicates （）.A
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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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all air is purged from the pump and charging fittingsC
the high pressure cutout switch is held open to prevent accidental startingD
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单选题In an air conditioning system, low head pressure associated with a reciprocating compressor can be the result of （）A
broken valve springsB
tight drive beltsC
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单选题Refrigerant is normally sub-cooled in a refrigeration or air conditioning system condenser to （）.A
maintain adequate coil back pressureB
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单选题（）are supplied by main switchboard directly.A
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单选题Broken valve strips in an operating low pressure, air compressor will cause （）.A
an immediate crankcase explosionB
oil contamination in the compressed airC
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考题
单选题An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.A
oil foaming in the compressorB
higher than normal suction and discharge pressures with a higher box temperatureC
higher than normal discharge pressure with a normal box temperatureD
the compressor to run continuously
考题
单选题The air compressor pumps air to the （）.A
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air receiverD
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考题
单选题The compressor in an air-cooled condensing refrigeration system is short cycling on the high pressure cutout switch（）A
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system is low on refrigerantC
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discharge valves are leaking slightly
考题
单选题Air compressors are equipped with unloading systems for the purpose of（）.A
removing all but the frictional load during startingB
relieving intercoolers of high temperature buildupsC
providing high starting torque in the drive motorD
seating valve plates during compressor shutdown
考题
单选题The purpose of an air compressor unloading device is to （）A
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drain water from the cylindersC
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考题
单选题The air compressor pumps air to the （）.A
air cylinderB
combustion chamberC
steam drumD
expansion tank
考题
单选题The air compressor pumps air to the（）.A
engine cylinderB
air bottleC
evaporatorD
condenser
考题
单选题The air filter is fixed in the （） of an air compressor.A
inlet pipeB
outlet pipeC
inter coolerD
after cooler
考题
单选题A compressor should never be stopped （）.A
without first cooling itB
without first heating itC
without first unloading itD
without first loading it
考题
单选题The purpose of the refrigeration system low pressure cutout switch is to （）A
protect the compressor from liquid flood backB
protect the compressor from low discharge pressureC
start and stop the compressor upon system demandD
start the compressor after a drop in the evaporator pressure
考题
单选题If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the （）.A
combustion control air systemB
supply air systemC
ships service air systemD
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考题
单选题An un-loader is installed on an air compressor to （）.A
bypass the high pressure stage to the low pressure stage on 100% of the air compressors in serviceB
prevent excessive inter-stage pressure buildupC
control compressor discharge pressureD
remove all but the frictional load during starting
考题
单选题Starting air for auxiliary engines may be taken directly from the main reservoirs or through （）.A
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a controlling air bottleC
an emergency air compressorD
a main air compressor
考题
单选题To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air conditioning system, you should （）A
admit only enough fresh outside air to provide proper ventilationB
reduce the air reheating system loadC
lower the compressor head pressureD
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考题
单选题Air compressor cylinder un-loaders enable the compressor to （）.A
vary their speed according to temperature and loadB
start and come up to speed before air compression beginsC
change speed according to overload demandsD
reduce compressed air charge density
考题
单选题If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the （）.A
control air systemB
forced draft air systemC
supply air systemD
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单选题The efficiency of turbocharge system is increased by fitting a charge air cooler （） the compressor.A
insideB
beforeC
afterD
against
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