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Open the （）before starting an air compressor.
A . unload valve
B . cooling water
C . oil cup
D . sum
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In the refrigeration compressor the temperature of the vapor is （） by compression.
A . raised
B . risen
C . reduced
D . maintained constant
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A non-return valve in the air delivery line near to the compressor must be （）type similar to the compressor discharge valve.
A、the low inertia
B、the high inertia
C、the low velocity
D、the high velocity
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Foaming of the oil in a refrigeration compressor crankcase is caused by （）.
A . refrigerant boiling out of solution from the lube oil
B . liquid refrigerant flooding the compressor and system
C . lube oil viscosity being reduced by refrigerant dilution
D . compressor suction pressure suddenly increasing
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Sludge may form in the crankcase of an air conditioning compressor as a result of （）.
A . bubbling refrigerant
B . overheating and oxidation
C . lowered operating temperatures
D . reducing the cloud or flash point
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If the electric motor driving an air compressor fails to start, the cause may be a （）.
A . leaking unloader
B . tripped circuit breaker
C . control line leak
D . defective pop valve
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Excessive oil foaming in the crankcase of a refrigeration compressor can result in （）.
A . overheated compressor bearings
B . excess lube oil viscosity
C . carbon deposits on the compressor piston rings
D . wax crystals forming in the lubricant
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The power generated in the turbine must （） that required by the compressor.
A . be less than
B . be larger than
C . be as large as
D . not be so large a
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In terms of pressure and temperature in the refrigerant in the compressor, what happens to the primary?（）
A . its pressure and temperature are both lowered
B . its pressure and temperature are both raised
C . its pressure is lowered and its temperature is raised
D . its pressure is raised and its temperature is lowered
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The high air velocity leaving the compressor of an exhaust gas turbocharger is converted to pressure in the （）
A . inlet nozzle ring
B . turbine wheel blade
C . diffuser passages
D . inlet vol
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In the （） refrigeration compressor one end of the crank shaft extends through the crankcase house for connection, via a coupling or pulley, to an external drive motor.
A . open-type
B . hermetic
C . semi-hermetic
D . all the above
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The purpose of an air compressor unloading device is to （）
A . drain water from the air receiver
B . drain water from the cylinders
C . delay the compression process until the motor is up to speed
D . check pump alignment
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An important consideration in selecting a lubricating oil for use in a refrigeration compressor is for the oil to （）
A . have a high viscosity index
B . mix readily with refrigerant
C . have a high freezing point
D . have a low pour point
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Which of the following statements describes the function of an air compressor intake filter?（）
A . Protects against suction valve float
B . Provides a positive pressure on the air inlet valves
C . Prevents lubricating oil contamination of the compressed air supply
D . Protects against the damaging effects of airborne solid particle
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A dirty intercooler on the ship service air compressor will result in （）.
A . decreased compression ratio
B . higher than normal power consumption
C . un-loader malfunction
D . water in the lubricating oil
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Condensate must be drained from the intercooler and after-coolers of an air compressor because （）.
A . the cooling effect of the condensate reduces the compressors efficiency
B . a danger of explosion exists whenever water is present in a compressor
C . water causes erratic operation of pneumatic components
D . the volumetric capacity of the first stage is reduced if water remai
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Broken valve strips in an operating low pressure, air compressor will cause （）.
A、an immediate crankcase explosion
B、oil contamination in the compressed air
C、a decrease in compressor capacity
D、no immediate loss of the compressed air capacity
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The air charge leaving an intercooler, or after-cooler of an air compressor can be expected to be （）.
A、superheated
B、super-cooled
C、at or below the dew point
D、All of the above
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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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Air blowing from the intake air filter of an operating air compressor indicates （）.
A、broken inlet valves
B、broken discharge valves
C、pulsations in the air distribution system
D、overloading of the air distribution system
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Which of the listed operations will cause an automatically controlled refrigeration compressor to restart?（）
A . Closing of the solenoid valve
B . Closing of the expansion valve
C . An increase in the suction pressure
D . Decreasing the suction pressure
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The loss of （） from an air compressor could lead to an overheated air discharge and possibly an explosion in the pipelines leading to the air reservoir.
A、lubricating oil
B、compressed air
C、cooling water
D、sealing ring
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When a refrigeration compressor is in the ‘off’ cycle, the thermal expansion valve will（）.
A . always be wide open when the compressor restarts
B . continue to operate as if the system were in operation
C . remain open until evaporator pressure equalizes, then close until the compressor restarts
D . always be completely closed until the compressor restart
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When a refrigeration compressor is in the ‘off’ cycle, the thermal expansion valve will .
A.always be wide open when the compressor restarts
B.continue to operate as if the system were in operation
C.remain open until evaporator pressure equalizes, then close until the compressor restarts
D.always be completely closed until the compressor restarts
