What is the purpose of a blowdown in a boiler?

The purpose of a blowdown in a boiler is to remove impurities, making option C the correct choice. During normal operation, boilers can accumulate sediment, minerals, and other contaminants in the water. These impurities can lead to several issues, including reduced efficiency, corrosion, and even damage to the boiler itself.

Blowdown involves intentionally discharging a portion of the water from the boiler. By doing this, the concentration of dissolved solids within the remaining water is reduced, helping to maintain water quality and preventing the buildup of harmful substances. This practice is essential for the long-term health of the boiler and ensures safe and efficient operation.

In contrast, releasing steam primarily serves the purpose of utilizing the energy from the steam rather than managing water quality. Reducing water level is a separate operational action that may be needed for maintenance or safety reasons but is not the primary goal of blowdown. Increasing pressure relates to raising the operational pressure of the boiler, which is not accomplished through blowdown but rather through combustion processes and control mechanisms. Thus, option C is pivotal in maintaining operational safety and efficiency in boiler systems.