单项选择题
An un-loader is installed on an air compressor to （）.
A.bypass the high pressure stage to the low pressure stage on 100% of the air compressors in service
B.prevent excessive inter-stage pressure buildup
C.control compressor discharge pressure
D.remove all but the frictional load during starting
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相关考题
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单项选择题
After installing a new hydraulic pump in a system, what special attention should be given to the hydraulic system?（）
A.The relief valves in the system should be readjusted
B.The filters and strainers should be checked frequently
C.All system pressure should be readjusted
D.The system should be drained and renewed with a fluid of different operating characteristics -
单项选择题
For safe storage, the maximum allowable temperature to which refrigerant bottles should be exposed is （）.
A.100℃
B.125℃
C.150℃
D.175℃ -
单项选择题
One of the main functions of wearing rings, as used in a centrifugal pump, is to （）.
A.maintain radial alignment between the pump impeller and casing
B.absorb all impeller shaft end thrust
C.prevent water leakage to the atmosphere
D.prevent wear of the pump casing and/or impeller
