| 摘要 |
PURPOSE:To prevent a water supply pump from overheat while restraining external disturbances to water supply for a boiler by providing a recirculation valve opening/closing speed regulating means for opening the recirculating valve with low speed when intake flow deviation is large and with high speed when same is small. CONSTITUTION:An intake flow set value W is obtained by a function generator 8 on the basis of the rotational frequency N of a water supply pump for supplying water to a boiler. Also, an intake flow deviation X is obtained by a controller 10 according to the output of a deviation calculating section 9 for calculating the deviation of intake flow Q of the water supply pump form that set value W and the valve opening signal Y corresponding to the deviation X is generated from a opening/closing speed regulating circuit 16 to controllably open and close a recirculation valve. Then, said circuit 16 is provided with a deviation calculator 12, a signal limiter 18, an integrator 14 and additionally a opening direction limit value function generator 17. This function generator 17 is constituted to output the opening direction limiting signal which is changed to low speed when the intake flow deviation X is large and to high speed when same is small respectively.
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