A.Special tools are required for lapping or grinding
B.It is impossible to throttle flow with a butterfly valve
C.To close the valve, it is only necessary to turn the handle a quarter of a turn
D.The butterfly valve should never be used in a freshwater system
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A.closely observe the pump discharge temperature
B.close off the discharge valve, and watch for a rise in pressure
C.momentarily close off the suction valve, and watch for a rise in pressure
D.use a clamp on ammeter and compare the readings to past records
A.removing all but the frictional load during starting
B.relieving intercoolers of high temperature buildups
C.providing high starting torque in the drive motor
D.seating valve plates during compressor shutdown
A.loose expansion valve control bulb
B.low differential setting on the H-Pcutout
C.blown fuse in the motor circuit
D.faulty suction pressure regulator
A.prevent an internal explosion in the pump when it is overheated
B.enable a visual inspection of the pump while it is running
C.insure a proper alignment of the pump coupling to the driver
D.accommodate for friction between the impeller and the easing
A.explosive range
B.flash point
C.ignition temperature
D.combustion temperature
最新試題
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
A pressure drop through the refrigerant liquid line may cause （）.
Low compressor head pressure in a refrigeration system can be caused 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?（）
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
The major source of chemical contaminants in hydraulic fluid is （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The usual symptoms of cavitation in a centrifugal pump is （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.