單項選擇題If you heard a ‘crackling’ noise in centrifugal pump, the most probable cause of the problem would be（）

A.insufficient speed
B.cavitation
C.excess discharge pressure
D.excessive net positive suction head B


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1.單項選擇題The valve which is most suited for regulating the flow through a pipeline is a （）

A.gate valve
B.globe valve
C.swing-check valve
D.plug-cock valve

2.單項選擇題Increasing the speed of a centrifugal pump will result in an increase in its capacity in its capacityAnother means of increasing the capacity pump is to increase the（）

A.diameter of the discharge piping, with all other factors remaining the same
B.diameter of the suction piping, with all other factors remaining the same
C.width of the impeller only
D.diameter of the impeller

3.單項選擇題Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?（）

A.Oil is discharged from the impeller through the outlet
B.Gravity causes the oil to flow toward the discharge
C.The self-priming feature of the centrifugal pump enables it to draw its own suction as it starts
D.The discharge capacity varies directly with the speed of the impeller

4.單項選擇題The static suction head of is the （）

A.distance of the suction liquid level above the line of the pump
B.distance the suction liquid level is below the center line of the pump
C.force necessary to overcome frictional losses in the pump and piping
D.amount in inches of mercury the total suction head is below atmospheric pressure

5.單項選擇題A pump is defined as device that（）

A.produces pressure
B.imparts energy to a fluid to move it from level ‘A’ to level ‘B’
C.creates a vacuum to move a liquid in all installation
D.is to develop a pressure differential