A.more than 28 seconds
B.more than 60 seconds
C.less than 28 seconds
D.less than 60 seconds
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A.Sodium hydroxide
B.Sodium carbonate
C.Sodium nitrate
D.Sodium polyphosphate
A.expand
B.extract
C.increase
D.decrease
A.escapes
B.overheats
C.expands
D.accelerates
A.be interrupted
B.move downwards
C.move outwards
D.retain original position
A.Height of the machine
B.Temperature of the liquid seal
C.Gravity disc
D.Bowl diameter
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When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
When the steering gear is in operation, you should （）.
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
Thermostatic expansion valves can be adjusted for （）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
Which of the following statements is correct concerning heat transfer?（）
A pressure drop through the refrigerant liquid line may cause （）.
A grease gun is generally used to lubricate a （）.