单项选择题

Before an auxiliary boiler is shutdown for an extended period of time, the water in the boiler should have a pH value of （）.

A.10
B.7
C.4
D.1

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单项选择题

If over a period of weeks the air-box pressure of a turbo-charged, diesel engine, operating at full load, appears to be dropping off, the cause can be （）.

A.open air-box drains
B.loss of cooling water to the diffuser
C.gradual fouling of the air filters
D.improperly timed exhaust valves

单项选择题

The most common cause of scale formation in an auxiliary boiler is （）

A.concentrations of calcium sulfate in the boiler water
B.fuel oil in the feed water
C.improper treatment of the feed water with calcium sulfate
D.excessive feed water alkalinity