单项选择题
Which of the devices listed is common to all types of pumps?（）
A.A power end and fluid end
B.A propeller and educator
C.A volute and impeller
D.A turbine and piston
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相关考题
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单项选择题
A centrifugal pump may fail to deliver water when first started if the （）.
A.water seal pipe is plugged
B.pump is not primed
C.seal ring is improperly located
D.impeller is flooded -
单项选择题
Which features of a centrifugal pump reduce the need for renewing worn impellers and pump casings?（）
A.Close radial clearance between impeller hub and casing
B.Low rotational speed of impeller
C.Removable end plate
D.Replaceable impeller and casing wearing rings -
单项选择题
When securing a flash-type evaporator for an extended period of time, you should （）.
A.fill the unit with saltwater
B.fill the unit with de-scaling compound
C.completely drain the unit
D.tightly seal the unit to exclude air
