A.either all the way open or all the way closed
B.normally open
C.throttled depending on load
D.controlled by suction pressure
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When a hydraulic vane pump is working, which of the following is in contact with the vanes?（）
(1) the rotor
(2) the internal surface of the housing
(3) the external surface of the housing
A.(1) only
B.(2) only
C.(1) and (2)
D.(1), (2) and (3)
A.Control of evaporation
B.A separate means to prevent feed-water contamination
C.Power circulating pump
D.Super-heater
A.check and regulate the water level
B.close the air cock once fires are lit
C.blowdown the gage glass
D.crack the steam stop to assure protective steam flow
A.furnace to be re-purged
B.electric charge to buildup in the igniter
C.fuel pump to restart
D.drum level to stabilize
A.The blow down valve
B.The scum valve
C.The air release cock
D.Scot-blower
最新試題
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
The general purpose of a heat exchanger is to （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
A pressure drop through the refrigerant liquid line may cause （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.