单项选择题
If an electric motor driven air compressor fails to start, it may be due to a （）.
A.leaking discharge valve B.jammed suction valve C.tripped overload relay D.broken discharge un-loader
单项选择题 Which of the following precautions should always be carried out in dry dock?（）
单项选择题 Which of the following statements about pump operations is NOT a correct statement?（）
单项选择题 Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be （）.
