单项选择题

A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.

A.the four-way control valve failing to shift
B.the bleeder valve sticking in the open position
C.cold hydraulic fluid
D.a clogged air vent falter on the oil reservoir

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单项选择题

If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.

A.add fluid that is the same color as the fluid in the reservoir
B.add turbine oil because it is always a good substitute
C.add any oil that has the same viscosity as the hydraulic fluid
D.check the winch manufacturers instruction book

单项选择题

The output volume of a positive fixed displacement pump can be changed only by （）.

A.changing the angle of the tilting plate
B.changing the speed of the pump
C.moving the slide block and rotor
D.moving the shaft trunnion block

单项选择题

An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.

A.oil foaming in the compressor
B.higher than normal suction and discharge pressures with a higher box temperature
C.higher than normal discharge pressure with a normal box temperature
D.the compressor to run continuously