Boiler Master (basic firing rate demand) computation is dependent on the Current operating mode like.
Boiler Master (Firing Rate Demand)
- Coordinated mode,
- Boiler Follow mode,
- Turbine Follow mode,
- Manual mode.
This demand is transmitted in parallel to the fuel and air control sub -loops.
(1) Unit Startup
During the unit startup, Boiler Master is determined as a fixed demand with the rate to obtain the optimum boiler steam temperature rising and steam flow until HP turbine bypass control valve is fully closed. This demand will be adjusted manually or automatically according to the unit startup mode.
During this period, Main steam pressure is controlled by HP turbine bypass control valve. During the unit start up, the operating mode will be Manual Mode both Turbine governor and Boiler Master manual.
(2) Normal operation
After HP turbine bypass control valve is fully closed, the operating mode will be normally transferred to Coordinated Control Mode.
In case of Coordinated Control Mode, the turbine governor controls MW and Boiler Master controls the main steam pressure.
In case of Boiler Follow Mode, Boiler Master also controls the main steam pressure.
In case of Boiler Master Manual or load runback, the operating mode becomes Turbine Follow Mode and turbine governor controls the main steam pressure.