單項(xiàng)選擇題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


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1.單項(xiàng)選擇題When the steering gear is in operation, you should ().

A.check hydraulic oil levels every hour
B.check the rams for overheating
C.check for excessive oil leakage from rams
D.drain water from telemotor cylinders each watch

2.單項(xiàng)選擇題The oil in a cargo winch gear box should be sampled periodically to ().

A.prevent the gear box from leaking
B.prevent the oil from becoming inflammable
C.make sure it has not become contaminated
D.make sure the motor bearings are lubricated

3.單項(xiàng)選擇題A spur gear pump should be operated with the discharge valves ().

A.slightly opened
B.throttled
C.fully opened
D.halfway opened

4.單項(xiàng)選擇題The capacity of a centrifugal pump can be increased by the installation of a larger diameter impeller Another means of increasing the pump capacity is to ().

A.increase speed
B.increase the size of the cardent assembly
C.reduce wearing ring clearances
D.change the pump to a "close coupled" arrangement

5.單項(xiàng)選擇題Which of the following forms of energy is demonstrated through the process of combustion?()

A.Chemical energy
B.Mechanical energy
C.Thermal energy
D.Electrical energy