單項(xiàng)選擇題

Air compressors are equipped with unloading systems for the purpose of（）.

A.removing all but the frictional load during starting
B.relieving intercoolers of high temperature buildups
C.providing high starting torque in the drive motor
D.seating valve plates during compressor shutdown

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單項(xiàng)選擇題

When a refrigeration compressor motor fails to start, the FIRST thing that should be checked for is a （）.

A.loose expansion valve control bulb
B.low differential setting on the H-Pcutout
C.blown fuse in the motor circuit
D.faulty suction pressure regulator

單項(xiàng)選擇題

The purpose of the wearing rings used in a centrifugal pump is to （）.

A.prevent an internal explosion in the pump when it is overheated
B.enable a visual inspection of the pump while it is running
C.insure a proper alignment of the pump coupling to the driver
D.accommodate for friction between the impeller and the easing