單項(xiàng)選擇題

Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service?（）

A.Copper
B.Copper and carbon
C.Carbon
D.Bronze

你可能感興趣的試題

單項(xiàng)選擇題

For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should remain constant regardless of load changes?（）

A.Chilled water system supply temperature
B.Chilled water system return temperature
C.Compressor discharge temperature
D.Compressor suction pressure

單項(xiàng)選擇題

The flame safeguard control system of a large automatic auxiliary boiler will provide fuel shut off in the case of high （）.

A.water
B.voltage
C.fuel pressure
D.steam pressure