单项选择题
A.Hydraulic pumps B.Valves C.Hydraulic cylinders D.Hydraulic motors
In a general cargo crane, （） is fitted to raise or lowe...
单项选择题In a general cargo crane, （） is fitted to raise or lower the jib.
A.the slewing motor B.the luffing motor C.the hoisting motor D.none of the above
External and internal leakage in hydraulic systems may ...
单项选择题External and internal leakage in hydraulic systems may be caused by （）.
A.unusual vibration B.excessive worn parts C.abnormal pressure D.any of the above
What type of valve is used to direct the flow of hydrau...
单项选择题What type of valve is used to direct the flow of hydraulic fluid?（）
A.Relief valve B.Direction control valve C.Stop valve D.Pressure control valve
