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
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
A salinity indicator is used to determine the （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
Low compressor head pressure in a refrigeration system can be caused by（）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.