單項選擇題Purging air from a hydraulic system is necessary when（）

A.adding small amounts of oil to the system
B.the system has been overheated
C.the system has been drained and then filled with new oil
D.the system has been idle for a long period of time


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1.單項選擇題Leakage of hydraulic fluid from around the shaft of a hydraulic motor may be caused by（）

A.permanent loss of pump suction
B.worn shaft seals
C.high level in the oil sump
D.low motor RPM

2.單項選擇題Air trapped in the hydraulic fluid of a steering system would be indicated by（）

A.an improper rudder response
B.hammering noises in the equipment or transmission lines
C.popping or sputtering noises
D.all the above

3.單項選擇題How can the chance of contaminating hydraulic fluid be decreased when working on hydraulic system?（）

A.clean the fittings before they are disconnected
B.Place drip pans under leaky fittings
C.Seal any cracks in lines with Permatex
D.Coat all threads with graphite oil

4.單項選擇題In the design of hydraulic piping and equipment consideration is given to minimize turbulence in the hydraulic fluid, as this will cause（）

A.molecular fluid vibration
B.energy losses
C.wide pressure variations
D.mechanical damage to control valves

5.單項選擇題One function provided by a hydraulic accumulator is to（）

A.provide an area where air can separate from the oil
B.provide an area to separate solid contaminants from the oil
C.act as an oil and water separator
D.absorb shocks occurring in the system