VALVES HAVING A TURNABLE VALVE MEMBER

Abstract: A butterfly valve has a seal assembly (6) for engaging with the closed valve disc (4) in the form of a primary seal (14) carried in one recess of an H-shaped (figure 1) or h-shaped (figure 2) seal carrier (7), the seal carrier (7) being axially slidable with respect to the valve housing (1), and being biassed axially by a resilient washer (8), whereby the primary seal (14) is biassed against the closed disc (4).

Description: VALVES HAVING A TURNABLE VALVE MEMBER This invention relates to valves having a turnable valve member such as butterfly and ball valves. Such valves are commonly used in pipelines for controlling fluid flow. There have been very many proposals for sealing assemblies in such valves, but the sealing requirements become more stringent whilst the cost of manufacture needs to be reduced if possible whilst retaining valve performance. Various known seal assemblies utilise a resilient Massing of the seal against the valve member. For example specification no. US 3,570,811 shows a typical proposal in which a sealing ring is carried by a resilient washer assembly. According to the invention a valve comprises a valve housing provided with an axially directed fluid passage in which is mounted a turnable valve member, and an annular seal assembly encircling the passage and adapted to seal with the valve member at least in a closed position of the valve member, the seal assembly comprising an annular seal carrier which is mounted for limited axial movement in an annular recess in the housing, and a resilient energiser ring which, in radial cross-section of the seal assembly, comprises a substantially radially extending arm, a radially outer portion of the arm bearing against the housing, and a radially inner portion of the arm bearing against one axial end of the seal carrier, at least in some conditions of the valve, the seal carrier carrying on its radially inner side an annular primary seal for sealing engagement with the valve member, at least in the closed condition thereof, and means sealing the radially outer side of the seal carrier tc the valve housing. The last-mentioned sealing means is preferably located in a radially external recess provided in the seal carrier. The radially outer portion of said arm is preferably rigidly clamped to the housing. The housing recess in which the seal carrier is mounted is preferably defined by a substantially radial housing wall at one axial end, but is open at the opposite axial end, at which the radially inner portion of said arm is positioned. In one embodiment of the invention, the seal carrier is of substantially H-shape in radial cross-section, an annular seal being located in the recess defined by the lower half of the H-shape, and the primary seal being located, but projecting radially inwards from, the recess defined by the upper half of the H-shape. The arrangement is particularly.suited to a soft primary seal, such as a PTFE primary seal. In a second embodiment, the seal carrier is of substantially h-shape, the primary seal sitting in the open recess defined by the upper limb and horizontal bridge of the h-shape. That arrangement is particularly suitable for a hard primary seal. A gasket is preferably provided between said upper limb of the h-shape seal carrier and the primary limb to provide an effective seal between the primary seal and the seal carrier. Two butterfly valves, and a modification, all in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a partial axial cross-section of a first butterfly valve, the seal assembly being shown in the assemblec condition thereof but prior to closing of the disc, Figure 2 is e similar cross-sectional view cf a second butterfly val e, and Figure 3 shows a modification of the valve of Figure 1. Although the valve disc is shown in the closed position in both Figures 1 and 2, this has been done simply to show how there is interference with the primary seal. This interference will in practice result in some axial deflection of the seal carrier to the right in the drawings, against the resilient biassing then exerted by the radially inner portion of the energiser. The valve of Figure 1 comprises an annular valve housing 1 defining an axial fluid passage 2 Cthe axial direction being dictated by arrow 3) in which is pivotally mounted a butterfly valve disc 4 presenting a part-spherical seal-engaging surface 5 to an annular seal assembly 6 carried by the housing. The seal assembly 6 comprises a metal annular seal carrier 7 of H-shape in radial cross-section, as shown in Figure 1, resiliently biassed in the axial direction by a resilient energiser ring 8 in the form of a flat annular washer, the radially inner portion 9 of the ring 8 bearing against an annular, axially directed rib 10 on the seal carrier 7, and the radially outer portion 11 of the ring 8 being clamped between the housing 1 and an annular, metal retaining ring 12, gaskets 13 being provided on either side of the clamped outer portion 11. Seal carrier 7 carries an annular primary seal 14 of PTFE of substantially right-angle trapezium shape in radial cross-section fitting snugly the annular radially inwardly facing recess of the seal carrier, and a proprietary O-ring 15 housed in the radially outwardly facing recess of the seal carrier. Instead of the O-ring 15 the corresponding recess can be filled with graphite to provide a graphite ring. Such a graphite ring is suitable for both high temperature and cryogenic applications of the valve. The seal carrier itself is slidable axially of the housing in an internal corner-recess in the housing 1, the recess being defined by a radial housing face 16 and by a cylindrical radially inwardly facing or axial face 17, and the seal carrier is sealed to the axial face 17 by the seal 15, and in turn to the closed valve disc 4 by the sealing engagement between the primary seal 14 and the face 5 of the closed disc 4. Sliding engagement between seal carrier 7 and surface 17 prevents tilting of the seal carrier 7. As previously mentioned, Figure 1 does not show the rightwards axial deflection of the seal carrier 7 from housing face 16 which results from the engagement between the disc face 5 and the primary seal 14 when the disc 4 is turned to the closed position shown. Only the interference between the dimensions of the closed disc and the undeflected primary seal 14 is shown in Figure 1. The resulting rightwards movement of the seal carrier 7 on closure of the disc 4 results in resilient deflection of the radially inner portion 9 of the energiser ring 8 to the right, relative to housing 1, through the engagement of rib 10 on portion 9. The provision of rib 10 ensures that the length of the lever arm of the portion 9 is precisely determined so as to provide a controlled biassing force urging primary seal 14 against disc face 5. In Figure 2 parts corresponding to those of the valve of Figure 1 have been given corresponding reference numbers. In the seal assembly of Figure 2 the PTFE soft seal 14 has beer, replaced by a relatively hard seal 14 of a sintered nickel /graphite composite backed by an annular gasket 14 of graphite, and since the hard seal 14 retains its shape, it is not necessary to confine the seal 14 to the same degree as in Figure 1. Accordingly the h-shape of the seal carrier 7 of Figure 1 has been replaced by a metal sea" carrier 7 of h-shape in cross-section, the sea "1 14 being housec ir tne corner recess of the h-shape. As with Figure 1, the rightwards deflection of the seal carrier 7 in Figure 2 resulting from closing of the butterfly disc 4 has not been shown in Figure 2. Such a deflection is generally enhanced in a butterfly valve by arranging the disc to have a double-offset of the pivotal axis of the disc from the centre of curvature of disc surface 5. This double-offset feature is well known and well understood by the skilled person in this field and will not be further described. When the invention is applied to a ball valve, then since the seal 14 engages with the ball surface for all states of opening and closing of the valve, the axial position of the carrier 7 will not change significantly during opening and closing • of the valve. With a ball valve the seal 14 is dimensioned such that the carrier 7 is permanently displaced rightwards from the valve surface 16, whereby the energiser ring 8 permanently exerts a leftwards force on the carrier 7. In the modification of Figure 3, the energiser ring 8 of Figure 1 has been extended radially inwardly as a cusp 18 which engages with surface 5 in the closed condition of the valve to provide a secondary seal with the valve member. In the Figure 1 arrangement this secondary seal can provide a fire-safe function, whereby seal 14 provides a normal soft seal with the valve disc, and the metal cusp 18 provides a reserve seal in the event of destruction of the soft seal 14. The manner of operation of the cusp 18 can be arranged to be as described in our patent specification no. GB 2,105,823B. In that specification the cusp is described as having a rolling/wedging action under certain conditions of use.

Claims: CLAIMS 1. A valve comprising a valve housing (1) provided with an axially directed fluid passage (2) in which is mounted a turnable valve member (4), and an annular seal assembly (6) encircling the passage (2) and adapted to seal with the valve member (4) at least in a closed position of the valve member, the seal assembly comprising an annular seal carrier (7) which is mounted for limited axial movement in an annular recess in the housing (1), the seal carrier (7) carrying a primary seal (14) for sealing engagement with the valve member, at least in the closed condition thereof, and resilient means urging the seal carrier towards the valve member, characterised in that the primary seal (14) is carried on the radially inner side of the seal carrier (7), a further seal (15) is arranged to seal the radially outer side of the seal carrier (7) to the valve housing (1), and the resilient means is a resilient energiser ring (8) whicn, in radial cross-section of the seal assembly, comprises a substantially radially extending arm, a radially outer portion (11) of the arm bearing against the housing (1), and a radially inner portion (9) of the arm bearing against one axial end (10) of the seal carrier (7), at least in some conditions of closure of the valve. 2. A valve as claimed in claim 1 characterised in that the further sealing means is located in a radially external recess provided in the seal carrier. 3. A valve as claimed in .claim 1 or claim 2 characterised in that the radially outer portion (11) of said arm (8) is rigidly clamped to the housing. 4. A valve as claimed in any of the preceding claims characterise- in that the housing recess in which the seal carrier is mounted is defined by a substantially radial housing wall (16 at one axial end, but is open at the opposite axial end, at whic t r e racial1.. inner portion .9) of said arm is positioned. 5. A valve as claimed in any of the preceding claims character sed in that the seal carrier (7) is of substantially H-shape in radial cross-section, thereby defining radially inner and outer recesses, the primary and the further seal being located respectively in said recesses. 6. A valve as claimed in any one of claims 1 to 4 characterised in that the seal carrier (7) is of substantially h-shape in radial cross-section, the primary seal (14) sitting in an open recess defined by the upper limb and horizontal bridge of the h-shape. 7. A valve as claimed in any of the preceding claims characterised in that the seal carrier (7) is provided with an axially directed rib (10) to provide the contact position where the inner portion (9) of the energiser ring (8) bears on the seal carrier (7). 8. A valve as claimed in any of the preceding claims characterised in that the seal carrier (7) is slidable on a cylindrical, radially inwardly facing surface (17) of the housing. 9. A valve as claimed in any of the preceding claims characterised in that the energiser ring comprises a cusp portion (18) which is engageable with the closed valve member, at least in the event of destruction of the primary seal (14). 10. A valve substantially as described herein with reference to any one of the accompanying drawings.

Inventors: BURTON PHILIP JOSEPH, BURTON, PHILIP, JOSEPH
Applicants: WINN CHARLES VALVES, CHARLES WINN (VALVES) LIMITED
Application year: 1992
Main classification: F16K1
IPC codes: F16K1