What is boiler blowdown and why is it performed?

• A. The controlled removal of boiler water to reduce dissolved solids (TDS) and prevent scale and carryover, with continuous and intermittent blowdown options.
• B. The process of venting steam to atmosphere to reduce pressure.
• C. The method of cooling the boiler with external water jackets.
• D. The procedure of cleaning boiler tubes with solvent cleaners.

Answer: (A)

Blowdown is the controlled removal of boiler water to manage dissolved solids and other impurities. As water concentrates minerals when it turns to steam, the remaining boiler water becomes richer in dissolved solids. If these solids build up, they form scale on heat-transfer surfaces, reducing efficiency and heat transfer, and they can carry over with the steam into downstream equipment, causing damage. By blowing down, you periodically or continuously remove a portion of the hot boiler water and replace it with fresh feedwater, keeping the total dissolved solids (TDS) within design limits. Continuous blowdown slowly vents water to maintain a target TDS, while intermittent blowdown removes larger amounts at specific times (like startup or when solids spike) to purge sludge. The result is cleaner heat transfer surfaces, better boiler efficiency, and safer operation.