单项选择题
A.suction side of a bilge pump B.exhaust manifold of an auxiliary diesel C.discharge line from an air compressor D.chemical feed tank of an evaporator
Which of the listed statements is correct concerning th...
单项选择题Which of the listed statements is correct concerning the starting of centrifugal pumps?（）
A.They should always be started with the discharge valve closed B.They should always be started with the discharge valve opened C.A priming pump is always required to flood the impeller suction D.They should always be started with the sealing line valves closed
Excessive oil foaming in the crankcase of a refrigerati...
单项选择题Excessive oil foaming in the crankcase of a refrigeration compressor at start up can cause（）.
A.compressor damage from improper lubrication B.refrigerant absorption by the lubricant C.increased viscosity in the lubricant D.carbon deposit on the compressor suction valves
Which of the valves listed is NOT considered to be a hy...
单项选择题Which of the valves listed is NOT considered to be a hydraulic system directional control valve?（）
A.Spring-centered valve B.Unloading valve C.Three-position valve D.Two-position valve
