A.between the suction and discharge
B.below the liquid supply
C.above the liquid supply
D.any of the above
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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
Which of the following are components of a mechanical seal? （）
(1) stationary ring
(2) rotational ring
(3) packing
(4)spring
A.(1), (2) and (3)
B.(1), (2) and (4)
C.(2), (3) and (4)
D.None of the above
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If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
When the steering gear is in operation, you should （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
Thermostatic expansion valves can be adjusted for （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
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