单项选择题

Fins are installed on the fireside of water-tubes used in waste boiler to（）

A.decrease the velocity of gases flowing past the tubes
B.increase the rate of heat transfer
C.reduce accumulations carbon deposits
D.direct the flow of gases

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单项选择题

A smoking burner with a pulsating flame in auxiliary boiler, is an indication that the（）

A.fuel oil supply temperature is normal
B.burner electrode is incorrectly positioned
C.fuel／air ratio is incorrect
D.ignition current is too low

单项选择题

The correct procedure for giving an auxiliary boiler a bottom blow, is to begin（）

A.when the boiler has been secured long enough for most solids to settle
B.when the boiler has been cooled to ambient temperature
C.only after raising the water level to within 0~5 inch of the high water cutout only
D.after bypassing the low pressure

单项选择题

Bottom blow valves are installed on auxiliary water-tube boilers to （）

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