PURPOSE: To prevent the generation of an insufficient condition of air upon increasing the load of the boiler by a method wherein an air volume delay correction signal, outputted through a first delay circuit and a limiter, is added to or reduced from a fuel control signal to provide a fuel set signal.
CONSTITUTION: A difference between the main steam pressure signal 5 of the boiler 1 and the main steam pressure set signal 6, set by a main steam pressure setting knob 10, is operated by adding and reducing unit 7. The difference is operated by a proportional operator 11 and an integral operator 12 and is added by an adder 13 to produce the standard fuel control signal 21. Subsequently, the primary delay circuit 17 and the limiter 19 output a signal having a delay equivalent to the delay of the changing air volume upon receiving the fuel control signal 21 while the signal is outputted from the adding and reducing unit 11 as the fuel set signal 14. The limiter in this circuit is constituted so as to pass the signal of plus side and the fuel set signal 14 is outputted by adding the delay correction signal 29 of the air volume only upon increasing of the load of the boiler.
TANABE KAZUO
MORITA TADASHI
IMAI YOSHIHIKO
