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单选题
The packing installed in the pump stuffing box is lubricated by （）.
A
gravity and feed oil cups
B
grease cups
C
hand during installation
D
leakage through the stuffing box
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单选题Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）A
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The pump packing gland overheats after short operating periodsC
The motor over-current protective device continually shuts the pump downD
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lantern tings between the packing ringsC
a liquid sealD
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