單項選擇題For safe storage, the maximum allowable temperature to which refrigerant bottles should be exposed is （）.

A.100℃
B.125℃
C.150℃
D.175℃


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1.單項選擇題One of the main functions of wearing rings, as used in a centrifugal pump, is to （）.

A.maintain radial alignment between the pump impeller and casing
B.absorb all impeller shaft end thrust
C.prevent water leakage to the atmosphere
D.prevent wear of the pump casing and/or impeller

2.單項選擇題Brine density in a distilling plant is measured with a/an （）.

A.psychrometer
B.salinometer
C.anemometer
D.sphygmomanometer

3.單項選擇題Which of the following statements is correct regarding an oil with a high viscosity index?（）

A.A large change of viscosity occurs with a minor change in temperature
B.No change in viscosity occurs with any change in temperature
C.Very little change in viscosity occurs with a significant change in temperature
D.The viscosity of the oil increases with an increase in temperature

4.單項選擇題If you were operating a centrifugal water service pump with worn wearing rings, the （）.

A.pump would be very noisy
B.pump would vibrate excessively
C.pump would develop insufficient flow
D.stuffing box would leak excessively

5.單項選擇題The packing installed in the pump stuffing box is lubricated by （）.

A.gravity and feed oil cups
B.grease cups
C.hand during installation
D.leakage through the stuffing box