JPS54125503A - Re-circulating control method for pump - Google Patents

Abstract

PURPOSE: To prevent re-cycle valve chattering by setting a limit to a re-cycling control signal so that the re-cycle valve may be kept open to a certain degree until the suction rate reaches a fixed rate.

CONSTITUTION: While the load on a boiler is small and the flow rate of water supply is sufficiently smaller than the fixed value fMIN of the suction rate of a water supply pump BFP, the output signal of a control arithmetic unit COM becomes maximum and the opening of a recycle valve VLV is controlled symmetrically to the increase and decrease of supply rate of water into the boiler so that the suction rate of the water supply pump BFP is controlled to be equal to the fixed rate fMIN. As the water supply into the boiler increases, the output signal of the controlarithmetic unit CON decreases, decreasing the opening of the re-cycle valve VLV. However, when the output signal value of the control arithmetic CON becomes less than the opening α%, the output signal α is selected by a maximum value selector SEL to keep the opening of the re-cycle valve VLV larger than α%. Thus, chattering is prevented.

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