A.rise when the steam pressure is increased
B.remain constant as long as the feed pump operates
C.fall when the steam pressure is decreased
D.vary as the steam demand changes
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A.to raise water level
B.only while making steam
C.to remove scum
D.when fire are secured
A.drop as the boiler warms up
B.rise as the boiler warms up
C.remain unchanged until the boiler is hot enough
D.rise and fall with the steam demand
A.filled with water
B.purged
C.cleared of air
D.None of the above is true
A.Safety valves
B.Water tubes
C.Steam stop valves
D.Blow down valves
A.water-tube
B.fire-tube
C.exhaust gas
D.None of the above is true
最新試題
Which of the listed pumps is NOT a positive displacement pump?（）
The usual symptoms of cavitation in a centrifugal pump is （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
Which of the following statements is correct concerning heat transfer?（）
A grease gun is generally used to lubricate a （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
A salinity indicator is used to determine the （）.
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 （）.