What is the purpose of interlocks in a boiler fuel train?

• A. To monitor flame color and adjust fuel accordingly.
• B. To prevent unsafe sequences (fuel being supplied without proper air or flame) and to ensure safe operation.
• C. To regulate combustion air only.
• D. To provide a backup signal for water level.

Answer: (B)

Interlocks in a boiler fuel train are safety controls that ensure the burner only operates under safe conditions. They link fuel delivery to the essential preconditions of proper air supply and an established flame. If air is not adequate or no flame is detected, the interlocks prevent fuel from being supplied or shut the fuel valves off if a flameout or fault occurs. This prevents dangerous situations like fuel flowing without enough air or without ignition, which can lead to incomplete combustion, fuel buildup, or an explosion. In short, interlocks enforce a safe sequence so the boiler can only run when everything necessary for safe combustion is present.