In a two-element feed water control system, what does it compensate for?

In a two-element feed water control system, the primary role is to manage and compensate for changes in the water and steam conditions within a boiler. Specifically, it addresses the phenomenon known as "shrink and swell," which refers to the changes in water level within a steam drum caused by fluctuations in steam generation and feedwater input.

The "shrink" occurs when steam is drawn from the boiler more quickly than it can be replaced by feedwater, lowering the water level in the steam drum. Conversely, the "swell" happens when the steam generation decreases or the feedwater flow increases, leading to an elevated water level in the drum. The two-element control system utilizes measurements of both drum level and steam flow to maintain an optimal water level, ensuring efficient boiler operation and preventing issues such as flooding or low water conditions.

By effectively addressing these shrink and swell phenomena, the system maintains steady operation and enhances safety and performance in the boiler system.