A.sealed
B.cracked
C.shape changed
D.deformed
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A.deformed
B.rusted
C.cracked
D.scaled
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
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If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
The general purpose of a heat exchanger is to （）.
The major source of chemical contaminants in hydraulic fluid is （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
Which of the listed pumps is NOT a positive displacement pump?（）
Which of the following statements is correct concerning heat transfer?（）
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
A salinity indicator is used to determine the （）.