Patent ID: 7490627
Filing Date: 2009-02-17
Classification: F16K,Y10T

Abstract:
1. A butterfly valve with a water-filling function, comprising: a valve casing; a valve casing seal disposed inside the valve casing; a valve rod; a valve body that rotates around a shaft center of the valve rod and comes into sliding contact with the valve casing seal at a completely closed position; a pair of disk tail portions each provided at the back side of the valve body in a rotation direction in an opening operation of the valve body, the disk tail portions each having a spherically curved outer periphery that comes into sliding contact with the valve casing seals; a water flow hole formed in at least one of the disk tail portions, the water flow hole having one end opened to the outer periphery of the disk tail portion and the other end opened to the back side of the valve body; and a steady region where, in a graph of a relationship between a loss factor and an opening degree of the valve body, a change in the loss factor with respect to a change of the opening degree of the valve body is smaller than a change in the loss factor with respect to a change of the opening degree around the steady region, wherein water filling velocity V inside an upstream pipe of the butterfly valve for filling water from the water flow hole is set to approximately 0.5 m/s, and pressure head H upstream of the butterfly valve is set to approximately 100 m, a loss factor value fv determined by an equation below based on the set water filling velocity V and the set pressure head H is approximately 8000: a total opening area of the water flow hole is set such that the loss factor in the steady region generally equals the loss factor value determined by the above equation, and the opening degree of the valve body is kept at an opening degree corresponding to the steady region, when water filling is performed.