單項選擇題

Excessive alkalinity of the water in an auxiliary boiler can cause （）.

A.caustic embrittlement of the boiler metal
B.acidic corrosion of the boiler metal
C.hard scale deposits on the boiler tubes
D.etching of the heat exchange surfaces

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單項選擇題

The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.

A.assist in a quick cutoff of fuel injection
B.allow oil backflow from the injector to the helix
C.reduce fuel oil pressure between injection strokes
D.meter the quantity of fuel delivered

單項選擇題

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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Excessive alkalinity of the water in an auxiliary boiler can cause （）.

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The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.

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