GB2079899A

GB2079899A - Butterfly valves

Info

Publication number: GB2079899A
Application number: GB8100781A
Authority: GB
Original assignee: Charles Winn Valves Ltd
Current assignee: Charles Winn Valves Ltd
Priority date: 1977-11-08
Filing date: 1978-12-15
Publication date: 1982-01-27
Also published as: GB2079899B

Abstract

The seal of a butterfly valve comprises two primary sealing members (7, 8) and an independently secured fire-proof ring (11) therebetween. The valve disk (3) is pivotally mounted by means of two axially aligned shafts (32, 38), one of which (38) is an actuating shaft and is connected to the disk by means of a tongue (44) and groove (46) connection and is located by a fire- destructible sleeve (36) in the disk. The other shaft (32) is located in the valve housing (1) by a second fire- destructible sleeve (30). In the event of a fire destroying the sealing members (7, 8) and the locating sleeves (30, 36) the tongue and groove connection allows the valve disk to move into sealing engagement with the fireproof ring (11). <IMAGE>

Description

SPECIFICATION Butterfly valves This invention is concerned with rotary valves of the kind known as butterfly valves which comprise a valve member in the form of a pivotally mounted disk.

A butterfly valve of the kind with which this invention is concerned comprises a housing defining a passageway, a valve member pivotally mounted for movement between a closed position, in which it would prevent a flow of fluid along the passageway, and an open position in which it would allow flow, and an annular seal assembly to seal between the valve member and the housing when the valve member is in its closed position.

For use, for example, in the petrochemicals industry, there is a requirement of valves which are "fire-safe", that is to say valves which can still be closed to prevent the flow of fluid along a pipeline in the event of a fire of an expected intensity.

Fire-safe valves may be constructed to meet British Standard No. 5146.

The seals in known rotary valves commonly comprise sealing elements which are of P.T.F.E.

(polytetrafluoroethylene) or P.C.T.F.E.

(polychlorotrifluoroethylene) materials or other materials which are chosen for their useful sealing properties but which are liable to be destroyed in the event of a fire. In the event of destruction of the seals it would not be possible, unless provision is made for otherwise effecting a seal, to prevent flow through the valve.

It has been proposed, to provide a fire-safe valve, that the valve member should be movable into sealing engagement with a fireproof ring in the event of a fire destroying the primary seal. To that end it has been proposed to locate the valve member by means of fire-destructible members which would be destroyed in the even of a fire which destroyed the primary seal. so that the valve member would become free to move (under the influence of the fluid pressure in the passageway) a short distance along the passageway into sealing engagement with the ring.

It is an object of the present invention to provide an improved construction of fire-safe butterfly valve.

The invention provides a butterfly valve comprising a housing defining a passageway, a valve member in the form of a disk pivotally mounted in the housing for movement between a closed position, in which it would prevent a flow of fluid along the passageway, and an open position in which it would allow a flow of fluid along the passageway, and an annular seal assembly which comprises primary and secondary annular sealing portions and is arranged to seal between the valve member and the housing when the valve member is in its closed position, the valve member being pivotally mounted by means of two axially aligned shaft portions of the valve of which one is rotatably mounted in the housing for actuation of the valve, and the valve comprising also connecting means arranged to transmit rotation of said one shaft portion to the valve member but arranged to permit a radial movement of the valve member relative to said one shaft portion, and firedestructible locating means which prevents said radial movement and comprises a first firedestructible sleeve locating said one shaft portion in a bore in the valve member and a second firedestructible sleeve locating the other shaft portion in a bore in the housing, whereby in the event of fire destroying said primary sealing portion and said locating means the valve member in its closed position would become free to move radially relative to said one shaft portion along the passageway into sealing engagement with said secondary sealing portion of the seal assembly.

The connecting means may comprise a tongue and groove connection arranged to permit said radial movement; in one preferred construction the tongue and groove connection is between adjacent end portions of the two shaft portions, the tongue being provided on said one shaft portion and the groove being provided in said other shaft portion.

There is described and claimed in patent application No. 48625/78, from which the present application is divided, a rotary valve comprising a housing portion defining a passageway, a valve member pivotally mounted for movement between a closed position, in which it would prevent flow of fluid along the passageway, and an open position in which it would not prevent flow of fluid along the passageway, and an annular seal assembly arranged to seal against flow in either direction along the passageway between the valve member and the housing portion when the valve member is in its closed position, said seal assembly comprising first and second annular sealing portions and a ring member positioned between said sealing portions, the ring member being secured independently of said sealing portions so that in the event of loss of the sealing portions the ring member would remain securely held in position.

There now follows a detailed description, to be read with reference to the accompanying drawings, of two embodiments of the invention which are described by way of example.

In the drawings: Figure 1 is a cross-sectional partial view of a butterfly valve for cryogenic use with the valve disk shown in the closed position; Figure 2 is a view in a direction generally along the passageway, showing the mounting of the valve disk; and Figure 3 is a view similar to Figure 2 diagrammatically showing the mounting of the valve disk of the second embodiment.

The valve shown in Figures 1 and 2 comprises a housing 1 defining a passageway through which fluid is to pass. Only part of the housing 1 is shown in the drawings. A valve member 2 in the form of a circular valve disk 3 is pivotally mounted within the housing for movement between a closed position, in which it prevents the flow of fluid along the passageway, and an open position in which the flow of fluid is allowed. The circular periphery 4 of the disk 3 is displaced (axially of the periphery) from the pivotal axis X of the disk and is defined by an annular portion of the surface of a sphere which has its centre on the axis X. The housing 1 is formed with an annular recess in which is clamped an annular seal assembly 6.The seal assembly 6 comprises primary sealing portions provided by first and second aiinular sealing members 7 and 8 of polychlorotrifluoroethylene (P.C.T.F.E.), first and second resilient annular metal bands 9 and 10, and a secondary, back-up, sealing portion provided by a fireproof, rigid metal, support ring 1 1; as shown in Figure 1, the ring 11 is sandwiched between the two sealing members 7, 8, and the sealing members are in turn sandwiched between the two metal bands 9, 10, so that each sealing member is sandwiched between the ring 11 and one of the metal bands.

The annular seal assembly 6 is mounted on the housing 1 to seal between the periphery 4 of the valve disk and a wall of the passageway when the disk is in its closed position, the assembly being arranged to seal against flow along the passageway in either direction.

The seal assembly 6 is clamped in the recess in the housing by a clamping ring 1 8 which is retained in place by a series of circumferentially spaced clamping screws (not shown) which threadedly pass through holes 19 formed in a castellated ring 20 of which the castellations 21 are received behind radially inwardly directed castellations 22 on the housing. The clamping screws urge the clamping ring 1 8 to the left (in Figure 1).

A peripheral portion 25 of the support ring extends radially outwardly beyond the two sealing members 7, 8, and is clamped independently of the two sealing members between the clamping ring 1 8 and the housing.

The materials of the valve, and in particular the disk 3 and the support ring 11, are selected to ensure that the gap between the ring 11 and the periphery 4 of the disk 3 is maintained substantially constant over the intended range of working temperatures.

The sealing members 7, 8, being of P.C.T.F.E.

material, are of a relatively fire-destructible material as compared with the metal housing 1 and ring 1 The disk 3 is located for pivotal movement by fire-destructible locating means comprising members of P.T.F.E.

(polytetrafluoroethylene) material, so that in the event of a fire that destroyed the locating members the valve disk would become free to move a short distance axially along the passageway to seat against a face 1 7 of the support ring 11. Since the peripheral portion 25 of the support ring remains firmly clamped even when the sealing members 7, 8 are destroyed, the ring would remain securely held in position and the valve would still be effective substantially to prevent fluid flow. Fluid cannot readily pass around the peripheral portion 25.

As shown in Figure 2, a fire-destructible sleeve 30 of the locating means radially locates a first shaft 32 in a closed bore in the housing 1 for rotation about the pivot axis X. The disk is mounted on the shaft 32 and secured to the shaft, by two dowel pins 34, for rotation with the shaft for movement between its open and closed positions. A second fire-destructible sleeve 36 of the locating means helps to maintain the first shaft in axial alignment with a second shaft 38 located in a bore in the valve member and rotatably mounted in the housing on the opposite side of the passageway from the first shaft 32. The second shaft 38 is mounted in the housing 1 , for rotation about the pivot axis, by means of a bearing sleeve 40; the sleeve 40 may be, for example, of sintered bronze impregnated with P.T.F.E..The second shaft 38 is a valve actuating shaft by which, in use of the valve, the disk can be moved between its open and closed positions. The shaft 38 extends out of the housing for actuation of the valve, and sealing means, comprising the sleeve 40, seals between the shaft 38 and the housing to prevent the escape there-between of fluid from the passageway. The first and second shafts are connected for rotation together by connecting means in the form of a keyed connection 42. The connection 42 comprises a tongue 44 on an end portion of the second shaft 38 which is engaged in a groove 46 in the adjacent end portion of the first shaft 32 for sliding movement therein; thus the connecting means would allow a radial relative movement between the shafts but for the locating sleeves 30 and 36 which prevent such movement.

The disk 3 is mounted on the second shaft 38 and is radially located on the shaft 38 by the sleeve 36, the keyed connection 42 being adjacent the centre of the disk 3, as seen in Figure 2. The sleeve 36 extends around the end portions of the first and second shafts adjacent the keyed connection, as seen in Figure 2. The sleeves 30 and 36 together locate the valve member radially of the second shaft 38.

The sleeves 30 and 36 are both of firedestructible materials selected so that they would be destroyed in a fire which destroyed the primary sealing members 7, 8. Upon destruction of the sleeves 30 and 36 the keyed connection 42 wounds permit the shaft 32, with the disk 3, to be moved, by the fluid pressure in the passageway, radially of the shaft 38 and the pivot axis X, so that the disk (in its closed position) would be moved axially of the passageway into engagement with the support ring 11. In this way a seal would be achieved in the event of a fire which destroyed the sealing members 7, 8. The bearing sleeve 40 maintains a seal between the second shaft 38 and the housing, and there should not be any substantial loss of fluid from the passageway in the event of a fire.

The second embodiment (Figure 3) is a butterfly valve constructed substantially as the first embodiment except with regard to the mounting of the valve member. In Figure 3 parts of the valve corresponding to those of the valve of Figures 1 and 2 have been given corresponding reference numerals. In the second embodiment the single shaft 32 of the first embodiment has been replaced by two axially spaced-apart shaft portions 32a and 32b which are secured to the valve disk 3 by dowel pins 34a and 34b respectively. This arrangement is preferable to that of Figure 3 for very large valves where difficulties can arise with long shafts.

Although in the two embodiments described above the sealing members are of a P.C.T.F.E.

material, the invention is not so limited and may find application where sealing members of other materials (for example, P.T.F.E.) are used. The support ring can be of any material that is suitable for its role, but for a fire-safe valve should be of a material which is sufficiently fireproof to withstand any expected fire intensity. The locating means can be of any material which is similarly fire-destructible as compared with the material of the sealing members, so that the destruction of each occurs substantially simultaneously in the event of a fire.

Claims

1. A butterfly valve comprising a housing defining a passageway, a valve member in the form of a disk pivotally mounted in the housing for movement between a closed position, in which it would prevent a flow of fluid along the passageway, and an open position in which it would allow a flow of fluid along the passageway, and an annular seal assembly which comprises primary and secondary annular sealing portions and is arranged to seal between the valve member and the housing when the valve member is in its closed position, the valve member being pivotally mounted by means of two axially aligned shaft portions of the valve of which one is rotatably mounted in the housing for actuation of the valve, and the valve comprising also connecting means arranged to transmit rotation of said one shaft portion to the valve member but arranged to permit a radial movement of the valve member relative to said one shaft portion, and firedestructible locating means which prevents said radial movement and comprises a first firedestructible sleeve locating said one shaft portion in a bore in the valve member and a second firedestructible sleeve locating the other shaft portion in a bore in the housing, whereby in the event of fire destroying said primary sealing portion and said locating means the valve member in its closed position would become free to move radially relative to said one shaft portion along the passageway into sealing engagement with said secondary sealing portion of the seal assembly.

2. A valve according to claim 1 in which said connecting means comprises a tongue and groove connection arranged to permit said radial movement.

3. A valve according to claim 2 in which said tongue and groove connection is between adjacent end portions of said shaft portions.

4. A butterfly valve constructed and arranged substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

5. A butterfly valve constructed and arranged substantially as hereinbefore described with reference to Figures 1 and 3 of the accompanying drawings.

New claims or amendments to claims filed on 11 Sept.1981 Superseded claim 1 New or amended claims:

1. A butterfly valve comprising a housing defining a passageway, a valve member in the form of a disk pivotally mounted in the housing for movement between a closed position, in which it would prevent a flow of fluid along the passageway, and an open position in which it would allow a flow of fluid along the passageway, and an annular seal assembly which comprises primary and secondary annular sealing portions and is arranged to seal between the valve member and the housing when the valve member is in its closed position, the valve member being pivotally mounted by means of two axially aligned shaft portions of the valve of which one is rotatably mounted in the housing for actuation of the valve, and the valve comprising also connecting means arranged to transmit rotation of said one shaft portion to the valve member but arranged to permit a radial movement of the valve member relative te said one shaft portion in a direction along the passageway when the valve member is in its closed position, and fire-destructible locating means which prevents said radial movement and comprises a first fire-destructible sleeve locating said one shaft portion in a bore in the valve member and a second fire-destructible sleeve locating the other shaft portion in a bore in the housing, whereby in the event of fire destroying said primary sealing portion and said locating means the valve member in its closed position would become free to move along the passageway into sealing engagement with said secondary sealing portion of the seal assembly.