What is added to the feed water control system to prevent flooding of the boiler?

The correct response is the addition of a condensate receiver to the feed water control system to prevent flooding of the boiler. A condensate receiver acts as a collection vessel for condensed steam, ensuring that the returned condensate is properly managed before it is fed back into the boiler. By storing condensate temporarily, it helps maintain the appropriate water level in the boiler, preventing it from being overwhelmed by excess water.

If flooding occurs, it can lead to operational inefficiencies or even damage the boiler due to excessive water levels affecting heating surfaces and reducing effective steam production. The condensate receiver ensures that the system efficiently returns only the appropriate amount of water for proper boiler operation.

Other options, like a pressure relief valve, are used to relieve excess pressure within the system rather than manage the water feed levels. A vacuum gauge measures the pressure below atmospheric levels, which is also not related to preventing flooding. A steam separator is used to separate steam from water in the steam lines but does not directly affect the feed water control system of the boiler.