单项选择题
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
单项选择题 Air compressor receivers should be “blown down” at least （）.
单项选择题 A thermostatic expansion valve is properly controlling evaporator superheatAdjusting this valve to lower the superheat will result in a/an （）.
单项选择题 It is possible to mount a double suction centrifugal pump impeller with the vanes facing in the wrong directionThis would cause the pump （）.