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）
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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
A.variable stroke pumps
B.multistage pumps
C.positive displacement pumps
D.triple-ported pumps
A.mixed-flow pump
B.axial-flow pump
C.centrifugal pump
D.displacement pump
最新試題
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
The major source of chemical contaminants in hydraulic fluid is （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
One cause of high head pressure occurring in a refrigeration system can be （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
A grease gun is generally used to lubricate a （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
The usual symptoms of cavitation in a centrifugal pump is （）.