单项选择题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.单项选择题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.单项选择题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.单项选择题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.单项选择题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.单项选择题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

6.单项选择题Although lube oils used in the main lubricating service systems should have a relatively high flash point to avoid ignition, they can create smoke and fire hazards when they ().

A.are exposed to a vacuum
B.come in contact with extremely hot surfaces
C.are reduced in temperature to just above the pour point
D.become extremely agitated or aerated

7.单项选择题The viscosity of an oil is a measure of its ().

A.weight
B.internal friction
C.demulsibility

8.单项选择题The pour point of lubricating oils is affected the most by which of the following?()

A.Extensive centrifuging
B.Wax content
C.Water content
D.Acid content

9.单项选择题Which of the following statements is correct concerning the viscosity of lubricating oil?()

A.Viscosity will increase as temperature increases
B.Viscosity is a measure of a fluid s internal resistance to flow
C.Viscosity will decrease as temperature decreases
D.Viscosity is not dependent on temperature

10.单项选择题Under normal operating conditions, the rudder is hydraulically locked unless ().

A.the manual trick wheel is engaged for steering
B.the variable stroke pump is off stroke
C.a rudder order is given by the control system
D.an electric power system failure occurs at the steering gear