7. Drum-Level and Feedwater Controls
The boiler-drum control system is provided for the conventional drum-type boilers in subcritical power plants with a normally pulverized fuel-fired (coal/lignite) furnace. The boiler drum in this case acts as a reserve vessel that gets the feedwater as the supply at the inlet and saturated steam as the outlet.
There are number of control valves for drum-level control with various types of operating range and provisions for redundancy. To force the feedwater into the drum, there are a number of constant- or variable-speed FW pumps. If the feedwater level in the drum becomes too high, water particles can be carried over by the main steam going to the turbine and catastrophic damage might result. On ...