A.deformed
B.rusted
C.cracked
D.scaled
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A.in series
B.in parallel
C.either A or B
D.None of the above is tree
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.（2）and（3）
D.（1），（2）and（3）
Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump?（）
(1) Its discharge is continuous
(2) It has no internal valves
(3) Upon accidental closing of discharge valve, excessive pressure will not build up
A.（1），（2）
B.（2），（3）
C.（1），（2），（3）
D.（2）only
A.reduce
B.rise
C.raise
D.fall
A.increase discharge pressure
B.increase suction vacuum
C.develop pulsation flow
D.keep a steady rate of flow
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An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
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When the steering gear is in operation, you should （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
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