What is Blow Down Valve?
The open position of the blowdown valves is used for the operation. The primary role of the blowdown valve is primarily to regulate a steam/fluid constant flow under elevated differential pressure.
The primary purpose of a blowoff valve is removal of dirt, sediment and scale, the boiler code requires that valves which have dams or pockets in which sediment can accumulate cannot be used in blow-off service.
Also, the valves are useful in keeping boiler level rise within desirable boundaries during the rapid start of high pressure systems.
Construction of Blowdown valve:
The robust construction of these valves can effectively resist the mixture of service-related issues-a service in which elevated pressures result in elevated speeds that can lead to wire drawing and cavitation of metal surfaces.
The valves must also withstand the corrosive environment created by acid cleaning of boilers, and the potential wear problems caused by precipitated solids.
Types of Blowdown valves
Continuous blowdowns are generally continuous, while intermittent blowdowns are conducted as required.
Continuous Blowdown (CBD) valves:
Continuous Blowdown (CBD) valves are intended to work in a constant open position by continually releasing water from the boiler water surface through a blowdown tap, thus keeping the TDS level in the boiler drum.
Continuous Blowdown Valve is an angle type valve in a venturi diffuser with a needle-shaped trim. The venturi diffuser offers enough space for high-speed flashing water to avoid choked flow.
Intermittent Blowdown (IBD) valves:
Intermittent Blowdown (IBD) valves are intended to function at predetermined intervals by periodically releasing water & accumulated sludge through a blowdown tap close to the boiler’s bottom. These valves ’ main requirement is to ensure tight shut-off even after repeated blowdown activities.
Earlier, two distinct valves mounted in series and operated in a definite sequence performed these two tasks (blowdown and sealing). Intermittent Blowdown Valve performs both of these tasks in series, i.e. open-position blowdown and closed-position sealing.