单项选择题
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
The furnace of an oil fired boiler should be （） before ...
单项选择题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
（） are mounted in pairs to protect the boiler against o...
单项选择题（） are mounted in pairs to protect the boiler against overpressure.
A.Safety valves B.Water tubes C.Steam stop valves D.Blow down valves
In a （） boiler the hot gases from the furnace pass thro...
单项选择题In a （） boiler the hot gases from the furnace pass through the tubes while the water is on the outside.
A.water-tube B.fire-tube C.exhaust gas D.None of the above is true
