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
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
Which of the listed pumps is NOT a positive displacement pump?（）
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
Thermostatic expansion valves can be adjusted for （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
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?（）
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If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.