GB2033054A

GB2033054A - Butterfly valve

Info

Publication number: GB2033054A
Application number: GB7843117A
Authority: GB
Original assignee: WESTAD ARMATURFABRIK AS
Current assignee: WESTAD ARMATURFABRIK AS
Priority date: 1978-11-03
Filing date: 1978-11-03
Publication date: 1980-05-14
Also published as: GB2033054B

Abstract

The valve, for use with cryogenic fluids, comprises a valve disc 1 with a peripheral sealing surface 4 which cooperates with a sealing ring 5 disposed in an internal groove 6 provided in the valve body 2 between an annular seat 7 in the wall of the valve body and a retaining ring 8. The groove 6 is undercut and exhibits a radial, inwardly open slot 16 through which a radial, inwardly-projecting sealing lip 19 on the sealing ring 5 extends to cooperate with the sealing surface when the disc 1 is in the closed position. The sealing ring 5, which may be of FEP resin, has a substantially U-shaped cross-section with the lip 19 disposed at the middle portion of one U-leg, and with a radial, outwardly-projecting flange 20 extending from the lateral edge of the U-bottom, the flange 20 being retained in an annular space 21 between the retaining ring 8 and the seat 7. A clamping ring 22 of stainless steel is disposed between the legs of the U- shaped sealing ring 5 for exerting a radial, inwardly-directed pressure on the sealing lip 19. The clamping ring 22 has a U-shaped cross-section, the bottom 25 and legs 24 thereof being adjacent to the bottom and legs of the sealing ring 5 and the U-bottom 25 being displaced from a radial plane through the lip 19. The clamping ring 22 consists of U-shaped members 26 connected to one another in the circumferential direction of the clamping ring. <IMAGE>

Description

SPECIFICATION Butterfly valve This invention relates to a butterfly valve of the kind comprising a valve disc with a peripheral sealing surface and an axis of rotation in the body of the valve which is dis placed in relation to a plane through said sealing surface, said sealing surface cooperating with a sealing ring disposed and retained in an internal groove in the valve body provided between an annular seat in the wall of the valve body and a retaining ring which is pressed against the sealing ring to hold the sealing ring in place, said internal groove being undercut and exhibiting a radial, inwardly open slot through which a radial, inwardly-projecting sealing lip on the sealing ring extends to cooperate with said sealing surface when the disc is in the closed position, said sealing ring having a substantially U-shaped cross-section with said radial, inwardly-projecting sealing lip disposed at the middle portion of one U-leg, and with a radial, outwardly-projecting flange extending from the U-bottom, said flange being retained in an annular space in said groove between said retaining ring and the annular seat in the valve body wall, and a clamping ring of stainless steel disposed between the legs of the U-shaped sealing ring for exerting a radial, inwardly-directed pressure on said sealing lip.

In butterfly valves of the kind referred to, when using sealing rings of an inelastic material such as fluorinated ethylene-propylene (FEP) resin or the like, it is known to use a form of clamping ring which, under the various relevant temperature conditions, presses the sealing ring more or less against the valve disc sealing surface when the butterfly valve is closed. In a known type of butterfly valve, such a clamping ring takes the form of a ring of aluminum which lies radially outside the sealing ring but in the groove in which the sealing ring is located. When such butterfly valves are used with cryogenic fluids, the clamping ring will shrink more than the material of the valve disc and body, and thereby increase the sealing pressure, pressing the sealing lip on the sealing ring against the valve disc sealing surface.However, since the circumferential elasticity of such a ring is limited, this type of valve structure requires very close tolerances and does not completely prevent permanent deformation of the sealing ring material at the variations in temperature to which the butterfly valve is subjected.

In order to provide a seal in butterfly valves of the kind referred to whereby the sealing ring itself, with its clamping ring, is rendered significantly more elastic or resilient in the circumferential direction of the clamping ring, in order thereby to avoid permanent deformation of the sealing ring material, and to obtain the effect that the elastic spring force of the clamping ring increases with decreasing tem perature, thereby forcing the sealing lip of the sealing ring even more tightly against the sealing surface of the disc, it is known from Norwegian Patent Specification No. 131,003 to construct the clamping ring as an annular coil spring, preferably wound from ribbonshaped material such as, e.g. stainless steel, said clamping ring giving the sealing ring the desired elasticity in the radial direction by means of each individual coil spring winding but without affecting the circumference of the sealing ring to an appreciable degree, the annular coil spring, as opposed to the previously-mentioned aluminum ring, being easily extensible in the circumferential direction.

This known clamping ring, in the form of an annular coil spring, provides very good elasticity at all temperatures in both the circumferential and radial directions, and it also has the advantage that the tension of the spring in the radial direction increases with decreasing temperature owing to the increasing rigidity of the material at decreasing temperature.

The present invention aims to provide a butterfly valve having a clamping ring which retains the above good characteristics but which also can be produced more reasonab!y, or a clamping ring which only exerts force in the radial direction on the sealing ring at the temperature variatgions to which the butterfly valve is subjected. In addition, it is an aim of the invention to obtain a clamping ring which gives an increased radial tensile force, in order thereby to increase the capability of the butterfly valve to withstand pressure on the side opposite the main pressure side of the valve.

According to the invention, a butterfly valve of the kind referred to, is characterised in that said clamping ring is of U-shaped cross-section, the bottom and legs of the U-shaped clamping ring being adjacent to the bottom and legs of the sealing ring and the U-bottom of the clamping ring being displaced from a radial plane through said sealing lip, said clamping ring consisting of U-shaped members connected to one another in the circumferential direction of the clamping ring.

In a butterfly valve in accordance with the invention each individual member of the clamping ring is able to move relative to adjacent members so that the circumference of the clamping ring and thus its diameter are permitted to change and thus to adapt to the dimensional variations which occur in the butterfly valve under the variations in temperature to which it is subjected.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a sectional view of one embodiment of a butterfly valve in accordance with the invention, the section being taken perpendicular to the axis of rotation of the valve disc, Figure 2 is a detail view, on an enlarged scale, of part of the valve of Fig. 1, Figure 3 is a perspective view, on an enlarged scale, of part of Fig. 2, Figure 4 is a perspective view of the clamping ring of the valve of Fig. 1, and Figure 5 is a view similar to Fig. 4 of a modified embodiment of the clamping ring.

Fig. 1 shows a butterfly valve of conventional type, comprising an eccentricallymounted valve disc 1 in a valve body 2. The axis 3 of rotation of the disc 1 is displaced relative to a central plane through the peripheral sealing surface 4 of the disc which surface, in the closed position of the valve, cooperates with a sealing ring 5 positioned in an internal groove 6 in the valve body 2. The internal groove 6 is provided between an annular seat 7 in the wall of the valve body 2 and a retaining ring 8 which is pressed against the sealing ring 5 by appropriate means.In the example illustrated, a ring 9 is axially spaced from the retaining ring 8 on the side of the latter remote from the sealing ring 5, the ring 9 being locked against axial movement in the valve body 2 in a direction away from the disc 1 by means of a locking ring 10 disposed in a groove 11 in the wall of the valve body and cooperating with a radial offset 12 in the ring 9. A plurality of screwthreaded holes 1 3 are provided in the ring 9 for bolts 14, which are tightened to press against the retaining ring 8, which thus holds the sealing ring 5 in place.

Fig. 2 shows the groove 6 with the sealing ring 5 and the retaining ring 8 on an enlarged scale. This Figure clearly shows that the sealing ring 5 is positioned in an undercut groove, which is formed because the retaining ring 8 has an annular lip 1 5 which extends axially and reduces the axial width of the mouth 16 of the groove. Furthermore, the side of the groove 6 remote from the ring 8 is restricted by a corresponding lip 1 7 on an enclosing ring 1 8 which is in contact with the annular seat 7 in the valve body 2 and which, on its side remote from the seat 7, is shaped to fit against and to hold in place the sealing ring 5.

The sealing ring 5, which is held in place between the retaining ring 8 and enclosing ring 18, is preferably made of FEP resin material and has a U-shaped cross-section, with a sealing lip 1 9 extending radially inward from the middle portion of one of the legs of the U and a flange 20 extending radially outward from the lateral edge of the bottom of the U. The inwardly extending sealing lip 1 9 projects through the opening or slot 1 6 between the confronting lips 1 5 and 17, respectively, on the retaining ring 8 and the enclosing ring 18, and rests against the peripheral sealing surface 4 of the valve disc 1. The radial outwardly-extending flange 20 is held in place in an annular space 21 between the retaining ring 8 and the enclosing ring 18.A clamping ring 22, consisting of interconnected members 26 of U-shaped crosssection (see Fig. 4), preferably made of stair less steel, is positioned in the U of the sealing ring 5. Under the various relevant temperature conditions to which the valve is subjected, the clamping ring 22 exerts a spring pressure against the sealing ring 5 and forces the ring 5 and thus the inwardly-projecting sealing lip 1 9 more or less strongly against the sealing surface 4 on the disc 1 when the butterfly valve is closed.

The clamping ring 22 is positioned inside the sealing ring 5 such that the respective bottoms and legs of the two U-configurations are adjacent. The U-legs 24 of the clamping ring 22 are thus spring-biased against the Ulegs of the sealing ring 5, whereby the sealing lip 1 9 on one leg of the sealing ring is forced by spring pressure against the sealing surface 4 on the disc 1.This presupposes that the bottom 25 of the U of the clamping ring 22 is axially displaced from the radial plane through the sealing lip 1 9. By making the legs 24 of the U-shaped clamping ring 22 diverge somewhat, relative to the legs of the sealing ring 5, the effect is obtained that the legs 24 of the clamping ring, acting in the same way as each individual coil winding of the previously-discussed clamping ring, are spring-biased against the legs of the sealing ring 5 and force the sealing lip 1 9 against the sealing surface 4 on the valve disc 1. With variations in temperature, the U-shaped clamping ring 22 will operate in approximately the same way as the previously-discussed clamping ring, which comprises an annular coil spring.

The FEP resin material, of which the sealing ring 5 preferably is made, is essentially inelastic, and after the sealing ring 5 has been installed in the valve body and the disc 1 brought to the closed position, the ring 5 will become permanently deformed to a degree in order to adapt to the sealing surface 4 of the disc 1 and to any microscopic irregularities thereon.

When the valve disc 1 is in the closed position, each member 26 of the clamping ring 22 is loaded by the sealing lip 19, so that the legs 24 of each member 26 are forced somewhat together, as can be seen in Fig. 3. This effects sufficient sealing pressure at higher temperatures. On the occasion of a decrease in temperature, the spring tension of each U-member 26 will increase owing to the resultant increase in the rigidity of the material, and this will compensate for dimensional alterations in the various components of the valve, thus maintaining the sealing pressure.The sealing principle is thus based on mechanical and thermal loading, while at the same time it is pressure-sensitive because the groove 6 is connected with the main pressure side of the valve by means of bores 23 such that the pressure is transmitted to the Ushaped sealing ring and causes increased sealing pressure of the sealing lip 1 9 against the sealing surface 4 of the disc 1.

The thermal sealing arrangement subjects the sealing ring to load as a function of temperature. This is primarily due to the configuration of the clamping ring 22, shown in Fig. 4, from which it will be seen that the respective legs of each U-member 26 are connected to the corresponding legs of an adjacent member 26. If the connected Umembers 26 are imagined as straightened out, it will be appreciated that they would form a meander-like pattern. The connected members 26 thus have an elastic characteristic in the circumferential direction of the clamping ring. At lowered temperatures, this spring force will increase, as explained above, owing to the increasing rigidity of the clamping ring material with decreasing temperature.

When the valve temperature falls, the sealing pressure between the disc 1 and the sealing ring 5 increases, thus maintaining a right seal at cryogenic temperatures. When the valve temperature rises, the sealing pressure between the disc 1 and the sealing ring 5 decreases but the seal is maintained. This feature prevents permanent deformation of the sealing ring material at higher temperatures, as previously discussed in connection with the aluminum clamping ring.

Under certain conditions, it may be desired to have a clamping ring 22 which does not exert force in the circumferential direction of the clamping ring. The embodiment of the clamping ring shown in Fig. 5 may then be used, the ring being shown in inverted position compared with Fig. 4, for convenience of illustration. This embodiment consists of alternate U-shaped members 26' and 26" which overlap one another. Tongues 27 on each end of a member 26' project into an opening 28 in an adjacent member 26" and are bent such that the U-members 26' and 26" are attached together.The openings 28 are dimensioned so that the members 26' and 26" can be moved somewhat relative to one another, with the result that the circumference of the clamping ring 22 can adapt itself to changes in the valve dimensions resulting from temperature variations but without elastic spring tensions occurring in the circumferential direction of the clamping ring 22. This embodiment of the clamping ring 22 can of course be adapted so that it will be forced out to its maximum circumferential dimension at a desired temperature; at a subsequent increase in temperature, it would then exert an increasing inwardly-directed radial force upon further expansion of the butterfly valve components at increasing temperatures.

The butterfly valve disclosed herein will seal tightly at all pressures when the main pressure side of the valve is on the same side of the disc 1 as the axis 3 of rotation of the disc, i.e. when the direction of flow through the valve is upwardly as viewed in Fig. 1. When the pressure is on the opposite side (i.e. with opposite direction of flow), the valve will be tight at pressures up to at least 7 bar. In order to eliminate any risk of leakage around the flange 20, the latter may be provided with one or more annular grooves, such as the groove 7', in its axially-facing surfaces. Owing to its special configuration, with the sealing ring 5 being held in place between the retaining ring 8 and enclosure ring 18, the sealing ring 5 is safe-guarded against being pulled out of position by, for example, high flow rates in the valve. Moreover, the sealing ring and the retaining and enclosing rings can easily be removed and replaced should they become damaged.

Claims

1. A butterfly valve comprising a valve disc with a peripheral sealing surface and an axis of rotation in the body of the valve which is displaced in relation to a plane through said sealing surface, said sealing surface cooperating with a sealing ring disposed and retained in an internal groove in the valve body provided between an annular seat in the wall of the valve body and a retaining ring which is pressed against the sealing ring to hold the sealing ring in place, said internal groove being undercut and exhibiting a radial, inwardly open slot through which a radial, inwardly-projecting sealing lip on the sealing ring extends to cooperate with said sealing surface when the disc is in the closed position, said sealing ring having a substantially U-shaped cross-section with said radial, inwardly-projecting sealing lip disposed at the middle portion of one U-leg, and with a radial, outwardly-projecting flange extending from the U-bottom, said flange being retained in an annular space in said groove between said retaining ring and the annular seat in the valve body wall, and a clamping ring of stainless steel disposed between the legs of the U-shaped sealing ring for exerting a radial, inwardly-directed pressure on said sealing lip, characterised in that said clamping ring is of U-shaped cross-section, the bottom and legs of the U-shaped clamping ring being adjacent to the bottom and legs of the sealing ring and the U-bottom of the clamping ring being displaced from a radial plane through said sealing lip, said clamping ring consisting of Ushaped members connected to one another in the circumferential direction of the clamping ring.

2. A butterfly valve according to claim 1, in which the end portion of one leg of each Umember of the clamping ring is connected to the corresponding leg of an adjacent U-member, the end portion of its other leg being connected to a corresponding leg on another adjacent U-member.

3. A butterfly valve according to claim 1, in which the U-members in the clamping ring are connected to one another at the bottoms thereof, consecutive tongues on every other U-member being inserted into openings on alternate U-members and bent to hold the Umembers together, the dimensions of said openings in the circumferential direction of the clamping ring being such that the bent tongues can move in said direction.

4. A butterfly valve according to claim 3, in which the U-members with tongues and the U-members with openings overlap one another.

5. A butterfly valve according to any of the preceding claims, in which the clamping ring is made of stainless steel.

6. A butterfly valve according to any of the preceding claims, in which, in use of the valve, the interior of the U-section of the sealing ring is subjected to the pressure of the fluid medium controlled by the valve.

7. A butterfly valve constructed and arranged substantially as herein described with reference to, and as illustrated in, Figs. 1 to 4 or Figs. 1 to 3 as modified by Fig. 5, of the accompanying drawings.