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單項(xiàng)選擇題

When steam is being raised on a boiler, the water level will normally （）.

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

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單項(xiàng)選擇題

The furnace of an oil fired boiler should be （） before the operating burner is lit.

A.filled with water
B.purged
C.cleared of air
D.None of the above is true

單項(xiàng)選擇題

（） are mounted in pairs to protect the boiler against overpressure.

A.Safety valves
B.Water tubes
C.Steam stop valves
D.Blow down valves