单项选择题
The major source of chemical contaminants in hydraulic fluid is （）.
A.microscopic steel shavings
B.abrasive waste
C.anti-oxidant compounds
D.oxidation by-products
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相关考题
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单项选择题
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
A.increase the capacity of the coil
B.increase the superheat at the bulb
C.deliver more refrigerant to the coil
D.decrease the capacity of the coil -
单项选择题
Which of the listed pumps is NOT a positive displacement pump?（）
A.Centrifugal
B.Reciprocating
C.Gear
D.Rotary -
单项选择题
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
