单项选择题
Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur（） when the compressor.
A.has continuously for a long period
B.suction pressure is below normal
C.oil level is below normal
D.starts after a long idle period
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相关考题
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单项选择题
Strainers are commonly used in hydraulic systems to （）.
A.protect the pump from fine soluble contaminants
B.prevent solid particles from entering the pump
C.prevent solid particles from entering the filter
D.protect the directional control valves -
单项选择题
On which of the following heated surfaces of a flash type evaporator would you be more likely to find soft scale formation?（）
A.Feed-water heater internal tube surfaces
B.Internal distillate cooler tubes
C.Flash chamber vertical surfaces
D.Distilling condenser tubes -
单项选择题
Machinery operating features are designed to help conserve energy.Which of the following results will not contribute to energy conservation?（）
A.Reduction of friction
B.Insulation of hot surfaces
C.Lubrication of moving parts
D.Elevation of cooler outlet temperatures
