單項(xiàng)選擇題Air leakage between the shaft and stuffing box packing in a centrifugal pump is prevented by ().

A.a compressed packing gland
B.lantern tings between the packing rings
C.a liquid seal
D.the stuffing box gland


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1.單項(xiàng)選擇題Tube leaks in the distillate cooler of a two stage flash evaporator will result in ().

A.loss of second stage vacuum
B.contamination of the distillate
C.lower feed inlet temperature
D.contamination of the second stage condenser

2.單項(xiàng)選擇題The pressure of a liquid leaving the pump can be referred to as the ().

A.total head
B.discharge head
C.net positive suction head
D.suction head

4.單項(xiàng)選擇題Which of the following statements describes the relationship between viscosity and specific gravity?()

A.Liquids with different viscosities will always have the same specific gravity
B.Liquids with different viscosities will never have the same specific gravity
C.Viscosity and specific gravity are directly proportional
D.Viscosity and specific gravity are not related in that one does not define or limit the other

5.單項(xiàng)選擇題Some chloronated flourocarbon refrigerants may decompose into a toxic irritating gas if it is ().

A.stored at temperatures below 60 degrees Fahrenheit
B.charged into a system having copper fittings
C.allowed to mix with compressor oil
D.exposed to an open flame or hot surface