单项选择题
Before doing any work on a hydraulic system equipped with accumulators, you should（）
A.drain the accumulators and purge with oxygen
B.bleed off all stored energy from the accumulators completely
C.charge the accumulators to prevent system energy loss
D.pump the hydraulic fluid into the accumulators to prevent fluid loss
相关考题
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单项选择题
The ability of lubricating oils to resist viscosity changes during temperature changes is indicated by the（）
A.American Petroleum
B.Institute number viscosity index number
C.Seconds Saybolt Furol number
D.Seconds Saybolt Universal number -
单项选择题
The in the steering gear move the rudder to the required angel（）
A.control equipment
B.power unit
C.transmission mechanisms
D.fittings and pipeline -
单项选择题
Positive displacement, helical gear pumps are well suited for pumping oil because （）
A.stuffing boxes eliminate the leakage problems usually associated with other gear pumps
B.it is not necessary to closely maintain design clearances with this pump
C.they are essentially self-priming and produce a high suction lift
D.these pumps are designed with extreme tooth angled
