单项选择题
Cocks and valves control or interrupt flow, and have internal passages arranged so that they can be restricted or closed: in cocks, by rotating the plug, and in valves, by lowering, raising or rotating a disc in relation to a seating surfaceAccording to the above sentence, which of the following statements is not true?（）
A.Flows of fluids can be restricted by both cocks and valves
B.There are seats in the internal passages of valves
C.A disc of valve only moves up and down
D.We can infer that there is a bore in cock ping
相关考题
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单项选择题
It should be apparent that little or nothing is gained by opening a drain at the same time as or after admitting steamThe above sentence probably means （）.
A.There is apparent condensate in piping
B.The steam is not discovered after admitting steam
C.The condensate should be fully loaded in the piping as admitting steam
D.The condensate should be fully drained from the piping while admitting steam -
单项选择题
It is usual to identify the fluids in pipes by bands of paint at intervals, and the engineer should familiarize himself with the code in use.According to the above sentence, which of the following statements is true?（）
A.People can know the types of fluids in pipes by feeling with hands
B.There are series of rings painted in the pipes to show various fluids
C.Engineers should wear cards standing for ranks
D.Engineer knows his own code very well -
单项选择题
Disastrous explosions have been caused by accumulations of oil or oil vapour in air lines not drainedAccording to the above sentence, which of the following statements is true?（）
A.Oil vapour in air piping are dangerous
B.Explosion will cause oil vapouring in air lines
C.Oil vapour in air piping should be drained
D.Oil in air piping should not be drained
