单项选择题
When a flash-type evaporator is to be secured for an extended period of time, the entire unit should be drained, cleaned, and （）.
A.completely filled with saltwater
B.filled with de-scaling compound
C.tightly closed to exclude air
D.vented to the atmosphere
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相关考题
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Condensate must be drained periodically from the air compressor receivers to prevent （）.
A.second stage cylinder lockup
B.oil sump contamination
C.faulty operation of pneumatic valves
D.corrosion of air receiver baffles -
单项选择题
Overheating of a hydraulic system may be a result of （）.
A.changing pump discharge pressure in response to normal load variations
B.a high oil level
C.incorrect fluid viscosity
D.continued slow re-circulation of the oil -
单项选择题
The purpose of the low pressure cut-out switch is to （）.
A.maintain liquid refrigerant at the suction of the compressor
B.maintain a preset suction pressure to the compressor
C.start and stop the compressor at preset operating pressures
D.operate at minimum efficiency
