單項(xiàng)選擇題A centrifugal pump vibrates excessively during operationUpon disassembling the pump it is found that the impeller is out of balanceWithout an available spare, you should （）.

A.drill holes through the heavy side of the impeller until it balances
B.weld counterweights to the light side of the impeller
C.remove metal from the heavy side by machining in a lathe
D.acid wash and serape the heavy side until it balances


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1.單項(xiàng)選擇題An axial piston, variable stroke pump is used in a vessels hydraulic steering gearUnder pressure, oil continually leaks out from between the valve plate/cylinder barrel and will（）.

A.cause loss of hydraulic oil from the system
B.result in extreme damage to the pump
C.cause damage to the pump ff not continually drained from the pump casing
D.result in the system high side pressure to substantially drop off

2.單項(xiàng)選擇題In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.

A.saltwater heater shell
B.second-stage condenser
C.atmosphere
D.second-stage flash chamber

3.單項(xiàng)選擇題Which of the listed characteristics of lube oil are the most important to the engineer from an operational standpoint?（）

A.Ash content, carbon residue, and gravity
B.Viscosity, acidity, and demulsibility
C.Pour point, flash, point, and precipitation number
D.Auto-ignition point, viscosity index, and film strength

4.單項(xiàng)選擇題Which of the following statements describes the function of an air compressor intake filter?（）

A.Protects against suction valve float
B.Provides a positive pressure on the air inlet valves
C.Prevents lubricating oil contamination of the compressed air supply
D.Protects against the damaging effects of airborne solid particles

5.單項(xiàng)選擇題Hydraulic cranes must be properly warmed-up before being operated because （）.

A.warm-up allows the hydraulic system to become charged with oil
B.warm-up allows the relief valves to be properly tested
C.hydraulic strainers operate only during the warm-up period
D.hydraulic fluid must be at the proper viscosity