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單項選擇題

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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單項選擇題

A pressure drop through the refrigerant liquid line may cause （）.

A.solenoid valve to seize
B.compressor to hunt
C.formation of flash gas in the liquid line
D.expansion valve to freeze open

單項選擇題

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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