PURPOSE: To prevent inching operation and unnecessary parallel operation from occurring, by detecting a position of a valve disc of each discharge pressure constant control valve for plural pumps, and controlling the introduction and parallelling-off of the succeeding pump.
CONSTITUTION: When an automatic feed water system is constituted of two pumps P1 and P2, by way of example, discharge pressure constant control valves Va and Vb with each built-in flow detector are connected to respective discharge pipes 1a and 1b. When a flow rate of the succeeding pump increases and a valve disc 21 moves up to a position of its 21a in and around the full open, a switch 23 is operated by action of a permanent magnet 22, operating the succeeding pump. When the flow rate decreases and opening of the valve disc 21 moves downward up to a full line display position 21 in and around the half-open, a switch 24 operates and the succeeding pump comes to a stop. If control takes place like this, performance of the preceding pump can be sufficiently utilized. In addition, such a fear that the succeeding pump will operate parallely with the preceding pump is preventable.
SUGITA MATSUO
TAKEMURA HIDEAKI
KAWAGUCHI HITOSHI
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