Which of the following statements concerning butterfly valves is correct?
A.Special tools are required for lapping or grinding
B.It is impossible to throttle flow with a butterfly valve
C.To close the valve, it is only necessary to turn the handle a quarter of a turn
D.The butterfly valve should never be used in a freshwater system
第1题
A.one-half engine speed
B.the same as engine speed
C.twice engine speed
D.four times engine speed
第2题
A.the main engines
B.the auxiliary engines
C.the emergency generator engine
D.the auxiliary engines and the main engine(s)
第3题
A.open / “stop”
B.closed / “stop”
C.open / “start”
D.closed / “start”
第4题
A.flanges
B.nuts
C.expansion joints
D.bolts
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