GB2042138A - Firesafe fluid control valve - Google Patents

Abstract

A valve member 17 when positioned so as to prevent fluid flow through a passage 11 in a valve body 10 engages a ring 14 made of flexible resilient fluorocarbon synthetic resin material, the ring 14 providing a fluid- tight seal between the valve member 17 and a seat 12 on the body 10. In the event of the ring 14 failing, the valve member 17 engages a back-up ring 15 made of a high temperature, non- metallic material which is non-galling, such as graphite. The high temperature properties of the ring 15 thus enable the valve to remain fluid-tight when shut even if the flexible ring 14 is destroyed by fire. The ring 15 can be compression- formed in situ into a shape which ensures close contact with the valve member 17. In the event of the ring 15 also failing, the valve member 17 comes into contact with a metallic ring 13 from which it is normally spaced and thereby restricts the flow of fluid through the valve. This arrangement can be applied to butterfly-type valves as well as to ball-type valves. <IMAGE>

Description

SPECIFICATION Firesafe fluid control valve This invention relates to a fluid control valve, particularly though not exclusively of the butterfly or ball type, which can be made firesafe.

Conventional firesafe fluid control valves typically comprise a seat including a flexible ring with which a valve member is engageable to prevent fluid flow through the valve, the flexible ring being made of a soft material such as P.T.F.E. In the event of the flexible ring being destroyed by fire, the valve member is arranged to contact a metallic lip on the seat to maintain the valve shut. However, in order to satisfy the relevant British Standard 5146, close contact must be ensured between the valve member and the metallic lip, which poses very large manufacturing problems. These problems become more acute in larger valves, since the permissable clearance between the valve member and the metallic lip becomes less as the size of the valve is increased.In addition, where the valve is of the butterfly or ball type wherein there is angular movement of the valve member relative to the seat, problems arise due to "pick-up" or galling of the co-acting surfaces of the valve member and the metallic lip.

It is an object of the present invention to provide a fluid control valve which is capable of satisfying the requirements of the aforementioned British Standard 5146, and which obviates or mitigates the above-described problems. In this connection, references to British Standard 5146 are intended to mean BS.5146:1974 both as originally drafted and as proposed to be amended at the date of filing of this application.

Accordi,ng to the present invention, there is provided a fluid control valve comprising a body having a through passage, a valve member movable between a first position in which it permits fluid flow through the passage and a second position in which it prevents such fluid flow, a flexible ring which normally provides a seal between the body and the valve member when in its second position, and a further ring of high temperature, non-metallic material which is arranged to provide a seal between the body and the valve member in its second position in the event of failure of the flexible ring so as to prevent fluid flow through the passage.

The non-metallic ring is preferably intended to be resistant to temperatures of at least 600 C. The material of the non-metallic ring can also be inherently non-galling: for example, the non-metallic ring can be made of graphite.

Advantageously, a seat surrounds the passage in the body and incorporates a metallic mounting ring having a surface which is normally spaced from the valve member in its second position, but which is arranged to be engaged thereby in the event of failure of both the flexible ring and the non-metallic ring so as to restrict the flow of fluid through said passage. The flexible ring and/or the non-metallic ring are preferably incorporated into the seat, in which case the mounting ring advantageously has an annular recess therein into which the nonmetallic ring is compression-formed. In one particular arrangement, the mounting ring is composed of two annular parts which are axially engaged so as to retain the non-metallic ring therebetween: in this case, one of the annular parts can be interposed between the flexible ring and the non-metallic ring.

The flexible ring is preferably made of flexible resilient fluorocarbon synthetic resin material, such as P.T.F.E., and is preferably also subject to cold flow.

The valve may take the form of a butterfly valve in which the valve member is a disk mounted on the body so as to be pivotable about an axis transverse to the axis of the through passage. Desirably, the disk has a part-spherical peripheral surface which engages the flexible ring when the valve member is in its second position, and the pivot axis is offset from both the plane of the disk and the axis of the through passage, for example in the manner described in British Patent No. 1290325. In this case, the flexible ring is preferably of the type disclosed in British Patent No. 1305554.

Alternatively, the valve may take the form of a ball valve in which the valve member is a ball mounted in the body so as to be rotatable about an axis transverse to the axis of the through passage, the ball having a through bore which communicates with the through passage in the body when the valve member is in its first position. In this case, two seats are advantageously provided respectively surrounding parts of the through passage on opposite sides of the ball, each seat incorporating a flexible ring and a high-temperature, non-metallic ring.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure l is a sectional side view of a fluid control valve according to the present invention, in the form of a butterfly valve; Figure 2 is an enlarged view of part of the valve shown in Figure 1, illustrating in particular a seat thereof; Figure 3 is a similar view to Figure 2 of an alternative form of seat; and Figure 4 is a sectional side view of a fluid control valve according to the present invention, in the form of a ball valve.

Referring first to Figures 1 and 2, the butterfly valve shown therein comprises a body 10 having a through passage 11, and a seat 12 which is secured to one axial end of the body 10 and which surrounds the passage 11. The seat 12 is composed of a metallic ring 13 which supports two further rings 14 and 15. The ring 14 is made of flexible resilient fluorocarbon synthetic resin material (such as P.T.F.E.) which is subject to cold flow, for a purpose which will be explained later. In the particular embodiment illustrated, the flexible ring 14 is of the type described in British Patent No. 1305554.The ring 15 is made of a high-temperature, non-metallic material which is non-galling; examples of such a material are "GRAFOIL" (Registered Trade Mark), a form of graphite marketed by Union Carbide Corporation and "GRAFTITE", a form of graphite marketed by Crane Packing Ltd. The non-metallic ring 15 is received in an annular recess 16 in the mounting ring 13 which has undercut surfaces providing protection against the ring 15 being blow out by the pressure of the fluid flowing through the passage 11, the ring 15 being compression-formed within the recess 16.

A valve member in the form of a disk 17 having a part-spherical peripheral surface 18 is mounted in the body 10 so as to be pivotable about an axis 19 perpendicular to the axis of the passage 11, the disk 17 being pivotable between a first position (shown in broken lines in Figure 1) in which it permits fluid flow through the passage 11 and a second position (shown in fuli lines in Figure 1 ).in which the surface 18 engages the flexible ring 14 so as to prevent such fluid flow. In its second position, the disk 17 is also in light contact with the non-metallic ring 15. The pivot axis 19 is offset from both the plane of the disk 17 and the axis of the passage 11, and the centre of the part-spherical surface 18 lies on the axis of the passage 11 when the disk 17 is in its second position.

This arrangement causes the surface 18 to lift away from the flexible ring 14 when the disk 17 is pivoted out of its second position, so that the valve does not rely on an interference fit between these parts to achieve fluid-tight closing.

Because the flexible ring 14 is subject to cold flow, engagement thereof by the disk 17 effectively coldforms the ring 14to a required shape, sufficient resilience remaining to urge the co-acting surfaces of the ring 14 and the disk 17 into close contact. Such cold-forming of the ring 14 is assisted by its shape, and reference is directed to the aforementioned British Patent No. 130554 for a further explanation of this.

In the event of the flexible ring 14 being destroyed by fire or otherwise failing, the disk 17 when in its second position will engage closely the non-metallic ring 15 so as effectively to prevent fluid flow through the passage 11; more particularly, the leakage rate of the non-metallic ring is sufficiently low to satisfy British Standard 5146. In the event that the nonmetallic ring 15 also fails, for example due to mechanical damage, the disk 17 when in its second position will engage a surface 20 (see Figure 2) on the metallic mounting ring 13 which is normally spaced from the disk 17, thereby restricting the flow of fluid through the passage 11.

In order to prevent the escape of fluid to atmosphere, an annular seal 20a is provided between the body 10 and the metallic ring 13 so as to surround the passage 11. The seal 20a is made of graphite or graphite-based material and is compression formed into a suitably shaped recess in the metallic ring 13.

The valve described above is designed for fluid flowtherethrough only in the direction of arrow 21 in Figure 2, since fluid flow in the opposite direction would tend to dislodge the non-metallic ring 15 from the mounting ring 13 in the event that the flexible ring 14 fails. Figure 3 illustrates a modification of the valve in which bi-directional fluid flow is permitted.

In this modification, the metallic mounting ring 13 is composed of two annular parts 22 and 23 which are axially engaged and which retain the non-metallic ring 15 therebetween, one of the annular parts 23 being interposed between the ring 15 and the flexible ring 14. The part 23 is also disposed between the part 22 and the body 10 so that the non-metallic ring 15 is still retained between the parts 22 and 23 if the flexible ring 14 fails. The non-metallic ring 15 is compression-formed in a recess 24 in the annular part 22 using a die whose configuration matches that of the annular part 23.

Referring now to Figure 4, the ball valve shown therein comprises a metallic body 30 formed from two parts 31 and 32 which are secured together by bolts 33. The body 30 has a through passage 34 formed therein which passes through a valve chamber 35 in which a valve member in form of a ball 36 having a through bore 37 is housed. The ball 36 can be rotated by means of an operating member 38 about an axis 39 perpendicular to the axis of the passage 34 between a first position in which the bore 37 communicates with the passage 34 so as to permit fluid flow through the valve (as indicated in broken lines), and a second position in which the bore 37 does not communicate with the passage 34 (as indicated in full lines), thereby preventing fluid flow through the valve.

Two seats 40 are disposed in the valve chamber 35 and respectively surround parts of the passage 34 on opposite sides of the bail 36. Each seat 40 incorporates a ring 41 made of flexible resilient fluorocarbon synthetic resin material, such as P.T.F.E., which is sealingly engaged with the external surface of the ball 36, and a ring 42 made of a high-temperature, non-galling, non-metallic materials which is lightly contacted by the ball 36. As in the embodiments of Figures 1 to 3, each non-metallic ring 42 is made of graphite-based material. Each ring 42 is received in a respective annular recess 43 in the body 30 which is so shaped as to protect the ring from blowing out under the pressure of the fluid flowing through the valve. Adjacent each recess 43, the body 30 is shaped so as to form an annular lip 44 which is spaced from the external surface of the ball 36.

In the event of failure of the flexible ring 41 of either seat 40, the ball 36 will closely engage the respective non-metallic ring 42 thereby maintaining effective fluid-tight closure of the valve. In the event of the non-metallic ring 41 failing also, the ball 36 will engage the respective lip 44 so as to restrict the flow of fluid through the valve.

In all of the above-described embodiments, the high temperature properties of the non-metallic rings 14, 52 enable the valve to remain effectively fluid-tight when shut even if the flexible rings 14,41 are destroyed by fire. Moreover, since the nonmetallic rings 15,42 can be compression-formed, it is comparatively simple to make them in a shape which will ensure close contact with the valve member so as to maintain fluid-tight closing of the valve. Furthermore, even if the valve is subsequently damaged causing failure of the non-metallic rings 15,42 the mounting ring 13 in Figures 1 to 3 and the lips 44 in Figure 4 still maintain the valve in a low leakage condition. Thus, the valves are able to satisfy the requirements of British Standard 5146.

Because the valve has a high temperature capability in a non-oxidising environment, it is particularly suited for use in the field of petrochemicals.

Claims (18)

1. Afluid control valve comprising,a body having a through passage, a valve member movable between a first position in which it permits fluid flow through the passage and a second position in which it prevents such fluid flow, a flexible ring which normally provides a seal between the body and the valve member when in its second position, and a further ring of high-temperature, non-metallic material which is arranged to provide a seal between the body and the valve member in the event of failure of the flexible ring so as to prevent fluid flow through the passage.

2. Afluid control valve as claimed in Claim 1, wherein the non-metallic ring is resistant to temper atures of at eat 600'C.

3. Afluid control valve as claimed in Claim 1 or Claim 2, wherein the material of the non-metallic ring is inherently non-galling.

4. A fluid control valve as claimed in Claim 3, wherein the non-metallic ring is made of graphite.

5. Afluid control valve as claimed in any preceding claim, wherein a seat surrounds the passage in the body and incorporates a metallic mounting ring having a surface which is normally spaced from the valve member in its second position, but which is arranged to be engaged thereby in the event of failure of both the flexible ring and the non-metallic ring so as effectively to prevent fluid flow through said passage.

6. Afluid control valve as claimed in Claim 5, wherein the flexible ring and/or the non-metallic ring are incorporated into the seat.

7. Afluid control valve as claimed in Claim 6, wherein the mounting ring has an annular recess therein into which the non-metallic ring is compression-formed.

8. Afluid control valve as claimed in Claim 7, wherein the recess has undercut surfaces which serve to retain the non-metallic ring therein.

9. A fluid control valve as claimed in Claim 7 or 8, wherein the mounting ring is composed of two annular parts which are axially engaged so as to retain the non-metallic ring therebetween.

10. A fluid control valve as claimed in Claim 9, wherein one of the annular parts is interposed between the flexible ring and the non-metallic ring.

11. Afluid control valve as claimed in any preceding Claim, wherein the flexible ring is made of flexible resilient fluorocarbon synethetic resin material.

12. Afluid control valve as claimed in Claim 11, wherein the flexible ring is made of P.T.F.E.

13. Afluid control valve as claimed in Claim 11 or Claim 12, wherein the flexible ring is also subject to cold flow.

14. Afluid control valve as claimed in any preceding Claim, wherein the valve member is a disk mounted on the body so as to be pivotable about an axis transverse to the axis of the through passage.

15. Afluid control valve as claimed in Claim 14, wherein the disk has a part-spherical peripheral surface which engages the flexible ring when the valve member is in its second position, and the pivot axis is offset from both the plane of the disk and the axis of the through passage.

16. Afluid control valve as claimed in any one of Claims 1 to 13, wherein the valve member is a ball mounted in the body so as to be rotatable about an axis transverse to the axis of the through passage, the ball having a through bore which communicates with the through passage in the body when the valve member is in its first position.

17. Afluid control valve as claim in Claim 16, wherein two seats are provided respectively surrounding parts of the through passage on opposite sides of the ball, each seat incorporating a flexible ring and a high-temperature, non-metallic ring.

18. Afluid control valve substantially as hereinbefore described with reference to Figures 1 and 2, or Figures 1 and 2 as modified by Figure 3, or Figure 4 of the accompanying drawings.