单项选择题

Ammonia when used as a refrigerant is valuable because of its high efficiency, it is however （）.

A.toxic
B.flammable
C.explosive
D.all of the above

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单项选择题

Which of the following is operated from the main engine room console on an automated vessel?（）

A.Fire pump and lube oil pump
B.Lube oil pump and distilling plant
C.Distilling plant and shaft alley door
D.Shaft alley door and fixed CO2 release

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

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