To provide a butterfly valve with water filling function capable of reducing time deviation between actually required time from water filling start to the full pipe sate and the time calculated in advance.
A pair of disc tail parts are provided on a rear surface side of a valve element in the direction of rotation when opening the valve element. A water passing hole is formed on both of the disc tail parts. In the relationship between opening degree of the valve element and a loss factor fv of the butterfly valve, a stable region Rb wherein the loss factor fv shows almost a constant value with respect to variation of the opening degree of the valve element exists when water is filled from the water passing hole. A water filling speed inside an upstream side pipe of the butterfly valve at the time of water filling from the water passing hole and a pressure head on the upstream side of the butterfly valve are set, the loss factor fv of a suitable value is determined by the set water filling speed and the pressure head, and a total aperture area of the water passing hole is set so that the stable region Rb has the loss factor fv of the suitable value.
Yoshihiro Morimoto
Toshiji Sasahara
Yohei Harada
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