To cope with the rise and the fall of a main pipe pressure when a water feeding device is coupled directly to a service water line main pipe.
In a liquid feeding device for a service water line having pumps 11 and 12 to feed water in a service water line main pipe 1 to the suction demand side, when a state that a pressure on the suction side of a pump exceeds a target pressure on the discharge side is continued for a given time, operation of a pump is stopped. Further, through control the operation speed of the pump, water in the service water line main pipe is sucked and the pressure on the discharge side of the pump is controlled to a target pressure and water is fed to the demand side. In the so formed liquid feeding device for a service water line, when control of the operation speed of the pump is switched so that the pressure on the suction side of the pump is adjusted to a given pressure when the pressure on the suction side of the pump is reduced, the operation speed of the pump is gradually damped to effect switching of control.
YANAGISAWA SEIJI
KAWASAKI HIROSHI
MATSUNO KOZABURO
