单项选择题
Air line lubricators are used in compressed air systems to lubricate （）.
A.the suction and discharge valves
B.tools and equipment served by compressed air
C.air line reducing valves
D.all of the above
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相关考题
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Which of the listed devices would be installed at a control system air pressure reducing station?（）
A.Moisture separator
B.Vacuum breaker
C.Lubricator
D.Non-return valve -
单项选择题
Power is defined as the （）.
A.rate of doing work
B.amount of force needed to overcome friction
C.amount of work accomplished
D.distance through which an object is moved -
单项选择题
To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to （）.
A.re-adjust the discharge pressure
B.clean the expansion valve screen
C.add refrigerant
D.adjust the expansion valve
