What is the purpose of the lower part of the water column in a boiler?

The lower part of the water column in a boiler serves primarily to collect sediments and foreign material that may settle out of the water. Over time, various impurities and solids can accumulate in the bottom of the water column due to factors such as water treatment chemicals, minerals, or scale. This function is crucial because it helps maintain the quality of the water being circulated within the boiler system and ensures that sufficient water quality is maintained to prevent operational issues, such as corrosion or inefficiency.

In contrast, the upper part of the water column is utilized differently, such as to gauge water levels correctly. While measuring water level is essential for safe boiler operation, this action takes place primarily in the upper section, which is distinct from the settling purpose of the lower section. Therefore, the correct answer highlights the importance of maintaining water quality by collecting any foreign matter that can potentially interfere with the efficient operation of the boiler.