A.excessive condenser cooling water
B.warm food in the refrigerator
C.a shortage of refrigerant
D.s shortage of compressor oil
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A.either all the way open or all the way closed
B.normally open
C.throttled depending on load
D.controlled by suction pressure
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
A.acid
B.alkali
C.salt
D.None of the above
A.proper combustion
B.water in the fuel
C.excess air
D.cold fuel oil
A.The safety valve escape piping should be disconnected from the valve body and a blank inserted
B.The boiler vent valves should be opened
C.All hand-hole/manhole covers should be tightened up as much as possible to preclude any leaks
D.All of the above
A.The boiler oil tank
B.The steam pipe
C.The fire side
D.The safety valves
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最新试题
The usual symptoms of cavitation in a centrifugal pump is ().
The control mode in which the final control element is moved from one of two flexed positions to the other is known as ().
Low compressor head pressure in a refrigeration system can be caused by().
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump ().
A pressure drop through the refrigerant liquid line may cause ().
If the suction pressure at the refrigeration compressor is below normal, the cause can be().
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?()
A grease gun is generally used to lubricate a ().
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by ().
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is ().