默认题库 - 船舶辅助机械

单选题

The function of （） in a refrigeration plant using Freon is to move moisture from all refrigeration system.

A. filter
B. filter drier
C. heat exchanger
D. air cooler

单选题

The usual symptoms of cavitation in a centrifugal pump is （）.

A. noise and vibration
B. an increase in discharge pressure
C. an increase in suction pressure
D. lifting of the relief valve

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单选题

Low compressor head pressure in a refrigeration system can be caused by（）.

A. insufficient condenser cooling water
B. excessive condenser cooling water
C. air in the refrigeration system
D. excessive refrigerant in the system

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单选题

Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.

A. a high suction head
B. rotating rings
C. badly worn bearings
D. a loose stuffing box gland

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单选题

Thermostatic expansion valves can be adjusted for （）.

A. suction pressure only
B. head pressure only
C. superheat only
D. suction pressure and box temperature

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单选题

The various pumps and lines are （） to some extent so that each pump can act as an alternative for another.

A. interlocked
B. interconnected
C. interfered
D. interacted

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单选题

When operating with a negative suction head, which of the following types of pumps will require priming?（）

A. Reciprocating
B. Centrifugal
C. Rotary
D. Gear

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单选题

（） are used to limit the pressure in any particular portion and mainly control the pressure after the valve.

A. Relief valves
B. Check valves
C. Safety valves
D. Reducing valve

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单选题

Large pipes or （） are fitted between the steam and water drums to ensure good natural circulation of water.

A. fire-tubes
B. furnaces
C. down-comers
D. soot-blower

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单选题

For a purifier, changing to a gravity disc with larger hole diameter will move the interface towards the （）.

A. bowl periphery
B. bowl center
C. upper surface
D. lower surface

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