Question 58

The Correct Answer is B. The main feed check valve is a non-return valve installed between the feed line and the boiler drum (or economizer inlet). Its primary function is safety and operational integrity. It is crucial to **prevent the high-pressure water and steam within the boiler from flowing back into the feed line** and potentially damaging the feed pump or other components in the feed system, especially if the feed pump stops running (fails) or loses discharge pressure. ### Why other options are incorrect: **A) reduce feed pump discharge pressure loading:** The check valve introduces a slight pressure drop, but its main purpose is not to manage or reduce the overall discharge pressure loading on the pump. Pressure reduction is typically handled by regulating valves or line resistance. **C) check pressure pulsations in the feed line:** While valves and fittings influence flow, specialized components like dampeners are used to manage significant pressure pulsations. The feed check valve's primary role is flow direction control (non-return), not pulsation damping. **D) provide feed pump positive discharge head:** The feed pump itself generates the discharge head necessary to overcome boiler pressure. The check valve is installed *after* the pump and relies on the pump's generated pressure to open. It does not actively contribute to the pump's positive discharge head; rather, it protects the system from reverse flow.