Blowdown Valves

Blowdown valves are used on steam boilers to remove sludge, scale, suspended solids, and concentrated dissolved solids from boiler water. Selection depends on installation location, blowdown operating mode, design pressure, temperature, differential pressure, and compatibility with the existing steam or drain system.

In bottom blowdown service, the valve operates intermittently with rapid full opening and closing to create high-velocity discharge from the lower section of the boiler and remove settled solids. Tight shut-off is critical, since seat leakage increases loss of water, thermal energy, and water treatment chemicals. Typical arrangements for this duty include valves such as ARI STEVI BBD 415 and Gestra bottom blowdown valves, with flanged ends, DIN standardization, PN 40 pressure rating, body material 1.0619+N, and pneumatic actuation where an automated blowdown sequence is required.

In continuous surface blowdown, the control objective is TDS management and the steady removal of dissolved solids from boiler water. The valve must handle continuous flow, high differential pressure, and erosion at the throttling area. Gestra continuous blowdown BAE valves are referenced for continuous blowdown duty and compliance with EN 12952 and EN 12953.

Technical evaluation should also consider the water treatment regime, blowdown frequency, flash steam losses, maintenance requirements, and the safe disposal of hot condensate or blowdown discharge.