| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a head loss estimating device and a method of a backflow preventive check valve for detecting a head loss of the backflow preventive check valve for preventing a backflow to a tap water main pipe from a water supply device when stopping a pump in pump operation, in a direct feeding water system controlled by delivery pressure constant control or estimating end pressure constant control for operating a variable speed pump driven by variable voltage and a variable frequency power source. Ž<P>SOLUTION: This head loss estimating device and the method of the backflow preventive check valve detect that the water supply device enters small flow rate operation by an operation signal of a small flow rate detecting float switch equipped in the water supply device, and detect a delivery head and a pushing-in head of the water supply device at this time, and calculate a pump delivery head by a head approximate expression of the pump, and arithmetically operate as (the delivery head of the pump)+(the pushing-in head)-(a head of a water supply system)=(a fixed head loss of the backflow preventive check valve). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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