单项选择题
A.completely drain the boiler in an emergency
B.prevent sludge from forming in the drum
C.remove floating impurities from the boiler water surface
D.remove settled solids from the water drum
单项选择题 A burner responsible for producing black smoke in an automatic auxiliary boiler, would be caused by a （）
单项选择题 A firebox explosion in an automatically fired auxiliary boiler may be the result of （）
单项选择题 The diesel engine exhaust gas bypass, as fitted with some waste heat boilers, is installed to （）