What is a common requirement for once-through steam generators concerning feedwater?

Once-through steam generators are designed to produce steam directly from the feedwater without recirculation. Therefore, the quality of the feedwater is critically important to ensure efficient operation and to avoid issues such as scaling, corrosion, and impurities that can affect both the generator and the steam's quality.

Ultra pure feedwater is a common requirement for once-through steam generators because impurities in the water can lead to significant problems. For example, dissolved solids can cause scaling on heat exchange surfaces, reduce thermal efficiency, and potentially lead to equipment failure. Additionally, impurities can also contribute to corrosion, which can compromise the integrity of the system. Using ultra pure feedwater minimizes these risks and helps maintain the efficiency and longevity of the generator.

Moreover, once-through systems often operate at high pressures and temperatures, making them more susceptible to the adverse effects of water contaminants. Therefore, ensuring the feedwater is of the highest purity is a critical necessity in their operation, reinforcing the importance of this requirement.