A.contraction
B.retraction
C.expansion
D.shrinkage
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A.Hydraulic pumps
B.Valves
C.Hydraulic cylinders
D.Hydraulic motors
A.the slewing motor
B.the luffing motor
C.the hoisting motor
D.none of the above
A.unusual vibration
B.excessive worn parts
C.abnormal pressure
D.any of the above
A.Relief valve
B.Direction control valve
C.Stop valve
D.Pressure control valve
A.flow of oil
B.pressure of oil
C.A and B
D.temperature of oil
最新試題
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
Which of the following statements is correct concerning heat transfer?（）
When the steering gear is in operation, you should （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
A salinity indicator is used to determine the （）.
The general purpose of a heat exchanger is to （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
A pressure drop through the refrigerant liquid line may cause （）.