The figure below represents a typical automatic water level control system for boilers.
Fig.1 Automatic water level control system
Feed water pump draws feed water from Feed water tank and delivers through the Automatic feed water regulating valve(B) to the boiler.
Level transmitter(A) continuously monitors water level in the boiler & sends feedback to the Level controller(LC) at the Control panel.
Automatic feed water regulating valve(B) is pneumatically operated & fitted with an I/P positioner.The I/P positioner is connected to a control air supply at 7 bar through a filter regulator(F).Electronic signal from Level controller (LC) through control panel is transmitted to the I/P positioner and converted into corresponding pneumatic signal for regulating Automatic feed water valve (B) to maintain boiler water level within preset range.
Fig.2 Automatic feed water regulating valve