单项选择题
A.closed B.opened fully C.cracked open D.partly open
When starting a centrifugal pump, the discharge valve s...
单项选择题When starting a centrifugal pump, the discharge valve should be （）.
When start a screw pump, the by pass valve should be （）...
单项选择题When start a screw pump, the by pass valve should be （）.
A centrifugal pump can’t supply water after startingYou...
单项选择题A centrifugal pump can’t supply water after startingYou should check （）.
A.priming water B.power supply C.packing gland D.bearing lubrication
