Double eccentric butterfly valve and manufacturing method therefor
An eccentric butterfly valve, suitable for high-pressure fluids, in which: even if a dimensional error among components is large, the seat ring is aligned with the disk while sealability between the seat ring and the body is ensured; for either pressure, positive pressure or counter pressure, the seal surface pressure between the disk and the seat ring is ensured to achieve sealability; and a continuous seal portion is ensured between the body and the seat ring, thereby reliably inhibiting fluid leakage, and a method of manufacturing the eccentric butterfly valve. A tapered surface 31 formed on a seat ring 20 and a step portion 30 formed on a body 2 are opposed to each other. With a corner portion 35 of the step portion 30 on a tapered surface 31 side digging into the tapered surface 31, an annular seal portion 33 is formed on an opposed plane between the body 2 and a seat ring 6.
1. A manufacturing method of a double eccentric butterfly valve in which a disk is rotatably and axially supported via a stem inside a cylindrically-shaped body at a position eccentric from each of a center of a flow path and a sealing surface and this disk is provided to be able to seal in a hermetically-sealing state by a seat ring fixed with a seat retainer inside the body and made of an elastic material, wherein the disk is caused to be in a closed state and the seat retainer is accommodated in an annular attachment concave portion formed in the body; the seat ring is aligned with a position of the disk in a range of a clearance formed between this attachment concave portion and an outer circumference of the seat retainer; a tapered surface formed on the seat ring and a tilted surface of a step portion formed on the body are caused to be opposed to each other at a tilt angle crossing each other in a radial direction; at assembling, with a corner portion of the step portion on the tapered surface side digging into the tapered surface, the seat ring is elastically deformed along a shape of the tilted surface; an annular seal portion is formed on an opposed plane between the body and the seat ring; and, in a state in which a seal surface of the seat ring as an end face on an inner circumferential side and a sealing surface of the disk as an outer circumferential surface can be annularly sealed, the seat retainer and the body are fixed together.
2. The manufacturing method of the double eccentric butterfly valve according to claim 1 , wherein the seat ring is formed of a seat ring main body and a gasket portion integrally provided to extend on an outer circumferential side of this seat ring main body and, in vicinity of a boundary portion between the seat ring main body and the gasket portion, the tapered surface of the seat ring and the step portion of the body are opposed to each other.
3. The method of manufacturing the double eccentric butterfly valve according to claim 1 , wherein a length of the clearance in a radial direction is shorter than a width of the tapered surface in a radial direction.
4. A double eccentric butterfly valve in which a disk is rotatably and axially supported via a stem inside a cylindrically-shaped body at a position eccentric from each of a center of a flow path and a sealing surface and this disk is provided to be able to seal in a hermetically-sealing state by a seat ring fixed with a seat retainer inside the body and made of an elastic material, wherein a tapered surface formed on the seat ring and a tilted surface of a step portion formed on the body are opposed to each other at a tilt angle crossing each other in a radial direction and, at assembling, with a corner portion of the step portion on the tapered surface side digging into the tapered surface, the seat ring is elastically deformed along a shape of the tilted surface and an annular seal portion is formed on an opposed plane between the body and the seat ring.
5. The double eccentric butterfly valve according to claim 4 , wherein a protruding portion protruding in vicinity of an opposed portion between the tapered surface and the step portion is formed on the seat retainer, and this protruding portion is partially or entirely provided at a position of being superposed on the step portion in the flow path direction.
6. The double eccentric butterfly valve according to claim 4 , wherein the seat ring is formed of a seat ring main body and a gasket portion integrally provided to extend on an outer circumferential side of this seat ring main body, the tapered surface of the seat ring and the step portion of the body are opposed to each other in vicinity of a boundary portion between the seat ring main body and the gasket portion.
7. The double eccentric butterfly valve according to claim 4 , wherein, in an opposed region between the tapered surface and the step portion, a volume of a region crushed by the step portion digging into the tapered surface and a volume of a space region where the step portion does not dig into the tapered surface have a substantially equivalent size.