EP0760918A1

EP0760918A1 - A lateral seal system for valves

Info

Publication number: EP0760918A1
Application number: EP95900270A
Authority: EP
Inventors: Alberto Aliani; Giorgio Bartoccioni
Original assignee: KEYSTONE VANESSA Srl
Current assignee: KEYSTONE VANESSA Srl
Priority date: 1994-05-23
Filing date: 1994-11-09
Publication date: 1997-03-12
Also published as: AU8115594A; IT1272821B; ITPR940023A1; WO1995032377A1; ITPR940023A0

Abstract

The essential feature of a new lateral seal system for a butterfly valve (1), of which the pivotable valve disc (3) carries a sealing ring (5) mounted with freedom of radial movement, positioned to interact with a conical seat (4) and secured by a flange (7), is an annular gasket (9) composed of a corrugated external portion (9'') deformable in the radial direction and fastened by one edge to the sealing ring, and an internal portion (9') clamped between and in fluid-tight contact with the disc and flange.

Description

A LATERAL SEAL SYSTEM FOR VALVES

Description

The present invention relates to a lateral seal system for valves.

Useful application may be found for such a system specifically, though not exclusively, in valves of the type employed to shut off or more generally to regulate the flow of a fluid through pipes or ducts of sizeable proportions, for example such as those utilized in chemical manufacturing plants, offshore drilling platforms, oil and gas pipelines, and so forth.

Reference is made in particular to butterfly valves in which the moving valve element takes the form of a disc that can be caused by means of an external control to rotate about its own diameter and close against a seat, generally conical, afforded by the valve housing. To ensure an effective lateral seal between the valve element and the valve seat, use is made of at least one sealing ring fitted to the disc and allowed a degree of movement in the radial direction, in such a way as to guarantee a perfect fit between the active surfaces of the ring itself and of the conical seat.

The prior art has long embraced valves of the type in question, equipped generally with one or more sealing rings assembled as a pack and graduated in progressively diminishing diameters in such a way as to adapt to the conical profile of the seat, which are accommodated in a special slot afforded by the disc and clamped together thus by a flange secured to the disc with screws.

The rings must ensure not only a lateral seal but also a frontal seal, most importantly to avoid any leakage of fluid between the first ring (breasted with the disc) and the disc, and between the last ring (breasted with the flange) and the flange. To the end of improving the frontal seal afforded by the rings, use is made conventionally of an annular element, secured to the disc and acting as a wedge on the pack of rings. If a reliable frontal sealing action is to be guaranteed, at all events, then the force with which the rings are gripped between the disc and the flange, hence the clamping force of the screws, must be sufficiently strong. In addition, the sealing rings need to be mounted to the disc with a certain radial clearance, as already intimated. In effect, the internal diameter of each ring must be greater than the corresponding diameter of the slot in which the assembled pack is housed, so as to allow small displacements in the radial direction. In the case of the first and the last ring, such displacements consist substantially in sliding movements against the disc (or the wedge element) and against the flange, respectively. The main drawback betrayed by conventional valves of the type in question is that they are unable to ensure an effective frontal seal and an effective lateral seal at one and the same time. In practice, the rings cannot be tightened between the disc and the flange beyond a given limit, since the sliding friction between the first ring and the disc and between the last ring and flange becomes excessive, to the point of impeding the radial movement of the rings and jeopardizing the lateral sealing action between valve element and valve seat. Conversely, the weaker the clamping force applied in securing the flange to the disc, the greater will be the likelihood of fluid leaking past the various parts in frontal contact with one another, in particular between the first ring and the disc and between the last ring and the flange. The object of the present invention is to overcome the drawback presented by the prior art as outlined above, by providing a constructionally simple and inexpensive system such as will ensure an efficient lateral seal between valve seat and valve element, and, at the same time, an efficient frontal seal between the active frontal surfaces of the disc and of the flange, and the relative sealing ring. One advantage of the present invention is that the system can be applied effectively and in practical manner to existing butterfly valves. The stated object is realized, with other objects and advantages besides, in a lateral seal system as disclosed and characterized in the appended claims, essential elements of which include a sealing ring fitted to a valve disc, interposed between the disc and a flange with a degree of radial clearance, and an annular gasket comprising a radially deformable portion, secured by one edge to the sealing ring, and a further portion interposed between the disc and the flange and affording a static seal. A preferred embodiment of the invention will now be described in detail, by way purely of example, with the aid of the single accompanying drawing, which shows the lateral seal system in cross section. Referring to the aforementioned drawing, 1 denotes a butterfly type shut-off valve, in its entirety, which comprises a valve housing 2 fashioned with a conical seat 4 and, interacting with the seat, a valve element consisting in a disc 3 such as can be rotated controllably about an axis coinciding with a given diameter of the disc itself. The disc 3 is rotatable between a closed position, in which it occludes the seat 4, and an open position in which it is distanced from the seat 4.

Also indicated is a sealing ring 5, fitted to the disc 3, which affords an active sealing surface 6 of conical profile designed to engage the conical seat 4 when the disc 3 is in the closed position. The ring 5 is accommodated by a slot 8 created in the disc 3 especially for the purpose, and secured thus by means of a flange 7 offered frontally to the disc and fastened with screws 13. The ring 5 presents an internal diameter greater than the corresponding diameter of the slot 8, and thus possesses a certain freedom of movement in the radial direction.

12 denotes an annular element of graphite or other comparable material, seated in a relative groove afforded by the disc 3. According to the invention, the valve 1 is equipped further with an annular gasket 9 comprising two portions: an internal portion 9' interposed between the disc 3 and the flange 7, which affords a static seal, and an external portion 9" accommodated in an annular recess 14 afforded by the sealing ring 5, of which the outermost edge is also secured to the ring itself. More exactly, the external portion 9" comprises a convolute section capable of deforming in the radial direction,- and welded or riveted or bolted directly to the ring 5.

The internal portion 9' consists substantially in a flat annular element of sheet metal, which affords holes to accept the screws 13 securing the flange 7 to the disc 3, whilst the external portion 9", also annular and fashioned from sheet metal, presents a corrugated profile. The two portions 9' and 9" are embodied in a single piece. The valve 1 also comprises a first seal element 10 interposed between the internal portion 9' of the annular gasket 9 and the flange 7, and a second seal element 11 interposed similarly between the internal portion 9' of the annular gasket 9 and the disc 3. These same seal elements 10 and 11 also afford holes through which to insert the securing screws 13. It will be observed that these further elements function as static seals, inasmuch as the sealing action is brought about between parts not in relative motion (disc 3 and internal portion 9'; internal portion 9' and flange 7) .

The sealing ring 5 is capable of sliding movement between the disc 3 and the flange 7 practically without friction, or in any event without being compressed between the two components, given that it is not the function pf the ring 5 to perform a

'frontal' sealing action; instead, this function is entrusted entirely to the seal elements 10 and 11. With the system in operation, the closing movement of the valve 1 will bring the active surface 6 of the sealing ring 5 into faultless mating contact with the corresponding surface of the conical valve seat 4. The precision of the mutual contact between these two same surfaces is assured by the capacity of the ring 5 to deform in the radial direction. Accordingly, the 'lateral' seal is assured.

The 'frontal' seal is assured, as aforementioned, by the annular gasket 9 and the seal elements 10 and 11. This eliminates the need to provide what must inevitably be a dynamic seal, as in valves of conventional embodiment, either between the bottom frontal surface of the ring 5 and the corresponding surface of the slot 8 or, in like manner, between the upper frontal surface of the ring 5 and the corresponding surface of the flange 7. The frontal sealing capacity of the valve depends upon the force with which the flange 7 is secured to the disc 3. This force is not limited by the need to accommodate radial movement, as would be the case in prior art solutions, since the sealing ring 5 is not pinched between the disc 3 and the flange 7. Rather, it is the internal portion 9' of the annular gasket 9 that is restrained by the two components, as the drawing clearly indicates. The sealing system disclosed can be incorporated advantageously into a conventional butterfly valve without any substantial modification of the valve itself. Indeed it will be sufficient to discard the traditional seals, generally assembled as a pack between the disc and flange, and replace them with the ring 5, the annular gasket 9 and the two seal elements 10 and 11.

In practical application, the invention might be carried into effect other than exactly as described and illustrated: for example, the annular gasket 9 might present an external portion 9" of different geometry while retaining its ability to deform in the radial direction, a variation in detail that could be adopted without straying from the bounds of protection afforded by the appended claims.

Claims

1) A lateral seal system for valves of the type comprising: -a valve housing (2) ;

-a valve element embodied as a disc (3) capable of movement controllably between a closed position, in which it occludes a seat (4) afforded by the valve housing (2) , and an open position in which it is distanced from the seat (4), -

-a sealing ring (5) , exhibiting an active sealing surface (6) of profile matched to the seat (4) , accommodated with freedom of movement: in the radial direction internally of a slot (8) afforded by the disc (3) and secured thus by means of a flange (7) ; characterized:

-in that it comprises an annular gasket (9) composed of an internal portion (9'), interposed between and in fluid-tight association with the disc (3) and the flange (7) , and an external portion (9") secured peripherally to and in fluid- tight association with the sealing ring (5) ; and, -in that the external portion (9") is at least partially deformable in the radial direction.

2) A valve as in claim 1, wherein the external portion

(9") of the annular gasket (9) is corrugated in the radial direction.

3) A valve as in claim 1, further comprising a first seal element (10) and a second seal element (11) interposed respectively between the flange (7) and the internal portion (9') of the the annular gasket (9) and between the internal portion (9') of the the annular gasket (9) and the disc (3) .

4) A valve as in claim 1, wherein the external portion

(9") of the annular gasket (9) is accommodated by an annular recess (14) afforded by the sealing ring (5) .