GB2192255A

GB2192255A - Valves

Info

Publication number: GB2192255A
Application number: GB08616028A
Authority: GB
Inventors: David C Beauchamp
Original assignee: HATTERSLEY HEATON Ltd
Current assignee: HATTERSLEY HEATON Ltd
Priority date: 1986-07-01
Filing date: 1986-07-01
Publication date: 1988-01-06
Also published as: GB8616028D0

Abstract

A ring-shaped seal preferably for the closure member of a butterfly valve has two resilient portions 26 and 27 each of unclosed form and capable of being moved towards a closed form in use. In the preferred embodiment one of these portions is retained in a housing in the closure member and the other forms with the housing a slot for a resilient synthetic plastics material part 21. This arrangement facilitates manufacture and maintenance of the valve and improved operation. <IMAGE>

Description

SPECIFICATION A valve seat The present invention relates to a seat for a butterfly valve and to a valve including such a seat.

Butterfly valves are well known. Difficulties are encountered in providing a sufficient sealing action in both directions particularly under conditions of fire. In the past the usual solution has been to accommodate a composite plastics material/metal seal housed in the valve body. However, this is not entirely satisfactory and can lead to maintenance problems and to a reduction in the sealing face area available when the valve is accommodated in a pipeline.

According to the present invention there is provided a seat for a valve which is generally ring shaped and has a cross-section in a plane at right angles to the plane of the ring comprising two resilient portions each of unclosed form and each capable of being moved towards the closed form in use.

In a preferred embodiment of the invention, the seat forms part of a high performance butterfly valve. This comprises a valve member which is rotatable between open position and closed positions within a valve body. The valve member comprise two sub-members bolted together and defining therebetween a housing for the seat. One portion of the seat is held resiliently between the sub-members and the other portion is urged against the seat ona seat ring on the valve body. The seat forms one part of a composite seat the other part being a ring of synthetic plastics material such as P.T.F.E. This latter ring is also urged against the valve seat by the other portion in the closed position of the valve.

In order that the invention may be more clearly understood one embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a cross-sectional view of butterfly valve Figure 2 shows a cross-sectional view of the valve of Figure 1 along the line X-X, and Figure 3 shows a cross section of the seat of the valve of Figures 1 and 2.

Referring to Figures 1 and 2 of the drawings, the valve comprises a valve body 1 defining an aperture 2 in which a valve member 3 is disposed. The valve member 3 may be rotated between open and closed positions by means of a shaft 4. The valve body 1 is internally recessed and the recess is internally screwthreaded at 5. An externally complementary screwthreaded metal seat 6 is screwed into the recess. The section of the sealing face 7 of this metal seat has an externally convex curved form. In Figure 2 the valve is shown disposed between flanges 8 and 9 of sections of pipeline. In use sealing ring gaskets (not shown) would be interposed between flanges and valve.

The valve member 3, which is circular in form in a plane at right angles to the planes of both figures 1 and 2, comprises two circular sub-members 10 and 11. Sub-member 11 is bored through at several places. These bores match blind bores in the sub-member 10. All bores are internally screwthreaded and enable the sub-members to be fastened together by complementary screwthreaded bolts 12. The through bores in sub-member 11 lead into a ring shaped recess. This recess houses a circular gasket 13 and a metal ring 14 which is connected to the sub-member 11 by means of bolts 15 screwed through bores in the rings and into blind bores in the sub-member 11. These rings serve to protect the heads of the bolts 12 from corrosion in use of the valve.

The shaft 4 is held in position in a complementary bore in the sub-member 10 by a locking plug 16 of substantially T-shaped cross section. A gasket 17 is disposed between the head of the T and the sub-member 10. The plug 16 prevents rotation of the shaft 4 in the member 10 and enables the valve member 3 to be turned by the shaft 4. Facing circular peripheral edges of the sub-members 10 and 11 are formed to define a circular chamber which houses a composite circular seat indicated generally by the reference numeral 20. This comprises a ring 21 of resilient synthetic plastics material (P.T.F.E.) of complex cross section and a ring 22 of resilient metal material also of complex cross-section.The complex cross-section of the ring 21 includes a right angled portion which locates on a complementary projection 23 on the submember 10 and an externally convex face 24 which in use produces sealing contact with the sealing face of the metal seat 6. Referring specifically to Figure 3, The cross-section of the metal ring 22 comprises two unclosed part circular portions 26 and 27. Portion 26 is housed in an annular chamber defined between sub-members 10 and 11 and serves to hold the ring in position in the valve member.

The holding is positive and resilient as the portion 26 is held under compression due to the closing on the circular portion. Furthermore, as the portion 26 is in contact with the surrounding wall of the valve sub-members on three faces, good pressure sealing between the sub-members is provided. The other portion 27 is also compressed and this compression not only serves to urge the resilient metal ring itself into sealing contact with the metal seat 6 but also forces the resilient seat 21 into the metal seat 6. This in turn provides a positive sealing action between the valve member 3 and the valve body 1 whatever the direction of the positive pressure differential across the valve. Furthermore the combined synthetic/metal nature of the seat in the valve provides for sealing under fire conditions when the synthetic part of the seat is destroyed.

During operation of the valve by rotation of the shaft 4 and through it the valve member 3 the seat 20 is held positively within the member. The formation and disposition of the valve member is such that it cams into and out of the static metal seat 6 during operation.

The inclusion of the seal in the disc (valve member) rather than in the valve body facilitates manufacture and maintenance and enables a greater area of the valve body to be employed for sealing of the valve in a pipeline than would otherwise be the case. The two part valve members also enable the connection between member and operating shaft to be strengthened.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A seat for a valve which is generally ring shaped and has a cross-section in a plane at right angles to theplane of the ring comprising two resilient portions each of unclosed form and each capable of being moved towards the closed form in use.

2. A seat as claimed in claim 1 or 2, comprising a synthetic plastics material ring and a resilient metal ring.

3. A seat as claimed in claim 1 or 2, in which the two resilient portions of unclosed form form part of the resilient metal ring and extend to opposite sides respectively of a central plane extending through the metal ring.

4. A seat as claimed in claim 2, in which the synthetic plastics material ring is housed in an angle defined between the two resilient portions.

5. A seat as claimed in claim 2, in which the synthetic plastics material is polytetrafluoroethylene.

6. A seat for a valve substantially as hereinbefore described with reference to the accompanying drawings.

7. A butterfly valve comprising a valve body and a valve member which is rotatable between open and closed positions within the body in which the valve member incorporates a valve seat as claimed in any of claims 1 to 6.

8. A butterfly valve as claimed in claim 7, in which the seat is disposed in a substantially circular housing defined by the valve member.

9. A butterfly valve as claimed inc laim 8, in wich the valve member comprises two submembers one resilient portion being held between the sub-members and the other resilient portion being urged against a seat on the valve body.

10. A butterfly valve as claimed in claim 9, incorporating a seat as claimed in claim 2, in which the synthetic plastics material ring is disposed between a wall of the housing and one of the resilient portions.

11. A butterfly valve substantially as hereinbefore described with reference to the accompanying drawings.