A.low water level
B.low oil pressure
C.excessively high fuel pressure
D.an improper air/fuel ratio
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A.Reciprocating pump
B.Screw pump
C.Diffuser pump
D.Water-ring pump
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
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）
最新試題
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
A pressure drop through the refrigerant liquid line may cause （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
When the steering gear is in operation, you should （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）