A.reduce radial thrust to the impeller
B.double the liquid velocity through the pump when compared to a single volute
C.reduce hydraulic end thrust
D.provide the effect of multi-staging
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A.dirt will cause corrosion of bearing
B.bearings will leak oil excessively
C.dirt is very abrasive when mixed with grease
D.grease will become inflammable
A.promote refrigerant dehydration
B.be absorbed in the receiver
C.cause low condensing pressure
D.carry moisture and lead to corrosion
A.frosting of the liquid line
B.higher than normal head pressure
C.a clear sight glass
D.abnormally cold reefer boxes
A.The hose should not be twisted
B.The hose should be protected with a sleeve if it is subjected to rubbing
C.There should be some slack in the hose
D.All of the above
A.acid
B.fuel oil
C.sediment
D.water
最新試題
A pressure drop through the refrigerant liquid line may cause （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
Which of the listed pumps is NOT a positive displacement pump?（）
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
Low compressor head pressure in a refrigeration system can be caused by（）.