SEALING DEVICE FOR BUTTERFLY VALVE

PURPOSE:To readily and effectively perform the opening and closing operations of a butterfly valve by providing an adjustable disc seat on the outer periphery of the valve body of the butterfly valve and intimately contacting the disc seat with a seat ring by utilizing hydraulic pressure acting on the valve body. CONSTITUTION:An adjusting ring 6 is clamped to a valve body 2 with a bolt 8, a wedge-like action is produced with the inner peripheral end face 2a and the tapered surface of the inner peripheral surface of the ring 6, a disc seat 6 is projected by the clamping margin of the ring 6 in an outer peripheral direction, and the contact of a seat ring 3 with the disc seat 5 is adjusted. Since a plurality of bolts 8 are provided at the ring 6 in the periphery direction, the bolts are clamped differently at the deflected part from the other part so that the seat ring 3 is intimately contacted over the entire periphery of the disc seat 5. Further, the tapered surface of the inner periphery of the seat ring is produced with a slight gap when hydraulic pressure is not operated on the valve body, and the seat 5 is intimately contacted with the ring 3 by the deflection of the valve body producted by the hydrulic pressure produced at the valve body when the valve is closed.