Before starting a reciprocating, steam-driven pump that has been idle for a period of time, you should （）.

单项选择题When air becomes trapped in the hydraulic fluid of a steering system, the （）.

A.rudder will respond sluggishly
B.hydraulic rams will over-speed
C.sight glass will show bubbles
D.ram relief valves will lift

单项选择题If a refrigeration system were short of refrigerant, the condition would result in （）.

A.continuous running of the compressor
B.high suction pressure
C.high discharge pressure
D.short cycling of the compressor on the water failure switch

单项选择题Condensate must be drained from the intercooler and after-coolers of an air compressor because （）.

A.the cooling effect of the condensate reduces the compressors efficiency
B.a danger of explosion exists whenever water is present in a compressor
C.water causes erratic operation of pneumatic components
D.the volumetric capacity of the first stage is reduced if water remains

单项选择题In the refrigeration system, a shortage of refrigerant is indicated by （）.

A.the compressor short cycling on high pressure cut out switch
B.high suction pressure
C.high head pressure
D.bubbles in the sight glass

单项选择题Which of the following conditions must exist for heat to flow from one object to another?（）

A.The two objects must be in physical contact
B.The two objects must be the same size
C.There must be an existing temperature differential
D.There must be an existing weight differential