單項(xiàng)選擇題A double suction centrifugal pump impeller has been installed in the reverse direction, and will （）.

A.have a greater head capacity
B.operate with increased impeller efficiency
C.discharge through the suction side of the pump casing
D.require more power to run the shaft


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1.單項(xiàng)選擇題Hydraulic machinery failures are commonly caused by misalignment of the system components and by （）.

A.hydraulic fluid contamination
B.excessive fluid friction
C.turbulent fluid flow
D.fluid pressure surges

2.單項(xiàng)選擇題Air compressor receivers should be “blown down” at least （）.

A.yearly
B.quarterly
C.monthly
D.daily

3.單項(xiàng)選擇題A thermostatic expansion valve is properly controlling evaporator superheatAdjusting this valve to lower the superheat will result in a/an （）.

A.evaporator pressure decrease
B.evaporator coil over-feed
C.evaporator capacity increase
D.expansion valve diaphragm rupture

4.單項(xiàng)選擇題It is possible to mount a double suction centrifugal pump impeller with the vanes facing in the wrong directionThis would cause the pump （）.

A.head capacity to improve
B.discharge to be reversed
C.efficiency to decrease
D.slippage to decrease

5.單項(xiàng)選擇題Water allowed to accumulate in the hydraulic system oil will cause an oxidation process producing by- products which are normally （）.

A.gums, acids, and varnishes
B.removed by cellulose type filters
C.neutralized by oil additives
D.not removed by absorbent filters