A.discharge is continuous
B.it has no internal valves
C.upon accidental closing of discharge valve, excessive pressure will not build up
D.all of the above are true
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A.between the suction and discharge
B.below the liquid supply
C.above the liquid supply
D.any of the above
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （）
(1) reciprocating
(2) vane
(3) gear
A.（1）only
B.（1）and（2）
C.（1），（2）and（3）
D.（2）and（3）
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （）
(1) reciprocating
(2) rotary
(3) centrifugal
A.（1）only
B.（1）and（2）
C.（1），（2）and（3）
D.（2）and（3）
A.increased；decreased
B.decreased；increased
C.decreased；decreased
D.increased；increased
A.kg
B.MPa
C.mH20
D.None of the above
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When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
A salinity indicator is used to determine the （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
A grease gun is generally used to lubricate a （）.
Thermostatic expansion valves can be adjusted for （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.