WO2009136811A1

WO2009136811A1 - Sealing gasket with protection device

Info

Publication number: WO2009136811A1
Application number: PCT/RU2009/000118
Authority: WO
Inventors: Alexandr Pavlovich Epishov; Igor Petrovich Kleptsov
Original assignee: Alexandr Pavlovich Epishov; Igor Petrovich Kleptsov
Priority date: 2008-03-07
Filing date: 2009-03-10
Publication date: 2009-11-12
Also published as: RU2371620C1; DE212009000035U1

Abstract

Claimed is a sealing gasket (1) for sealing a flange connection (2), the sealing gasket (1) comprising an annular sealing member (6) which comprises a core ring (13) and two flexible sealing rings (14) concentrically arranged on each side of the core ring (13). The diameter of the flexible sealing rings (14) is smaller than the diameter of the core ring (13), so that the core ring (13) has an outwardly projecting edge. The sealing gasket (1) additionally comprises a protection device (7) with a circumferential cavity (12) facing the central axis of the protection device (7), wherein the protection device (7) is adapted to be mounted on the periphery of the core ring (13) with the projecting edge of the core ring (13) inserted into the circumferential cavity (12) of the protection device (7), and wherein the maximum thickness of the protection device is less than the thickness of the annular sealing member. In operation, the flexible sealing ring is deformed until the surface of the flexible sealing ring is flush with the outer surface of the protection device.

Description

SEALING GASKET WITH PROTECTION DEVICE

Area of Invention

The invention relates to sealing means and may be used for sealing flange connections in industrial pipelines, particularly, in chemical, oil and gas applications, as well as in thermal and nuclear power systems. However, the invention is not reduced to pipelines and can be used in any means having a flange connection, e.g. a valve, pump, compressor, engine, etc.

Background of Invention

Disruption of sealing gaskets in flange connections is considered to be one of the most frequently observed failures in pipelines. Crushing as a result of excessive squeezing is the most frequently observed reason of the disruption of sealing gaskets. Squeezing of sealing gaskets can be substantially enhanced by displacement of the flange faces in case of changing configuration of the flange connection under excessive pressure of the working medium, mechanical forces applied to pipelines, etc. Therefore, protection of a sealing gasket from excessive squeezing is important to prevent disruption and, eventually, a failure in the flange connection. These problems become even more serious where connections of large diameter (over Im) pipes are involved.

A sealing gasket for sealing flange connections disclosed in US 6367803 Bl of 04.09.2002 is regarded as the most close to the claimed invention. The sealing gasket is intended to be damped between two pipework connection flanges. The gasket includes a sealing ring comprising a rigid metal annular part with which a number of radiating metal lugs capable of being folded along the contour of a support flange are integrally connected. The sealing ring also comprises two flexible sealing rings concentrically arranged on each side of the rigid metal annular part, wherein the diameter of the flexible sealing rings is smaller than the diameter of the rigid metal annular part, so that the core ring has an outwardly projecting edge. The sealing gasket is adapted to be mounted between the flanges of different dimensions, the metal lugs are longer than the corresponding transverse dimension of the largest flanges in which the gasket can be mounted. However, the sealing gasket of this type does not comprise any devices for protection against excessive compression and therefore it may be crushed by the flanges as a result of excessive squeezing.

Summary of Invention The object of invention is to provide a sealing gasket protected against excessive squeezing resulting from compression of the flange faces.

According to the invention, this object is achieved by providing a sealing gasket for sealing a flange connection, the sealing gasket comprising an annular sealing member which comprises a core ring and two flexible sealing rings concentrically arranged on each side of the core ring, wherein the diameter of the flexible sealing rings is smaller than the diameter of the core ring, so that the core ring has an outwardly projecting edge. The sealing gasket further comprises a protection device formed as a ring, the protection device having a circumferential cavity facing the central axis of the protection device, wherein the protection device is adapted to be mounted on the periphery of the core ring with the projecting edge of the core ring inserted into the circumferential cavity of the protection device, and wherein the maximum thickness of the protection device is less than the thickness of the annular sealing member. Thus, flange faces may compress a sealing gasket of the invention until they reach the surface of the protection device. Further compression and crushing of the sealing gasket is prevented. The annular sealing member can be coated with a coating of porous polytetrafluoroethylene, and each flexible sealing ring can be a corrugated band of expanded graphite wrapped by a coating tape of porous polytetrafluoroethylene.

Preferably, the sealing gasket of the present invention further comprises a radial holder for installation the sealing member, wherein the holder is connected with the protection device and protrudes beyond the flanges of the flange connection when the sealing gasket is installed. The user can take the holder with his hand to conveniently install the gasket.

The protection device can be separable at least into two parts. At least one part of the protection device can be a ring connected with another part at its side.

The two parts of the protection device can be symmetrical. An identification means can be applied to the holder. The identification means can identify operational conditions such as sealing medium, temperature, pressure etc. of the sealing gasket.

One part of the protection device can comprise a circumferential segment and at least one additional fastening member for fastening the annular sealing member in the protection device.

The additional fastening member for fastening the annular sealing member in the protection device can be a circumferential segment profiled to match the protection device and removably secured on the protection device. The additional fastening member for fastening the annular sealing member in the protection device can comprise at least one holding member fixedly mounted on one of the parts of the protection device.

The additional fastening member for fastening the annular sealing member in the protection device can comprise a circumferential segment profiled to match the corresponding part of the protection device, wherein the circumferential segment is slidably mounted on the holding member and adapted to be fixed on the protection device.

The additional fastening member for fastening the annular sealing member in the protection device comprises at least one holding member fixedly mounted on one of the parts of the protection device.

The periphery of the core ring provides accurate positioning of the annular sealing member in the protection device. Coating of the sealing member of the sealing gasket made of porous polytetrafluoroethylene protects it before corrosion.

Description of Drawings

Embodiments of the invention are described below in detail with reference to the attached drawings, in which: fig. 1 is a sectional view of a flange connection with a sealing gasket according to an embodiment of the invention; fig. 2 is a side view of sealing gasket according to an embodiment of the invention; fig. 3 is a partial section taken along line A-A of Fig. 2 with one-layer coating of the annular sealing member; fig. 4 is a partial section taken along line A-A of Fig. 2 with two-layer coating of the annular sealing member; fig. 5 is an inclined perspective view of first embodiment of the flexible sealing ring made of corrugated band; fig. 6 is an inclined perspective view of second embodiment of the flexible sealing ring made of corrugated band; fig. 7 is a sectional view of the sealing gasket according to another embodiment of the invention; fig. 8 is a sectional view of the sealing gasket according to still another embodiment of the invention; fig. 9 is a partial side view of the sealing gasket with the identification means on the holder; fig. 10 is a side view of the sealing gasket according to another embodiment of the invention; fig. 11 is a side view of the sealing gasket according to still another embodiment of the invention ; fig. 12 is a side view of the sealing gasket according to still another embodiment of the invention.

Description of Preferred Embodiment The sealing gasket 1 for sealing a flange connection 2 according to the invention is positioned between two flanges 3 and 4 of the flange connection 2 pressed together by flange fasteners 5 (see fig. 1). The flange fasteners 5 may be bolts or stud bolts. Also, captive bolts hinged in one of the flanges of the flange connection 2 can be used.

The sealing gasket 1 comprises an annular sealing member 6, and a protection device in the form of a protection ring 7 preferably made of metal. The sealing gasket 1 may also comprise a radial holder 8 for facilitating proper installation of the gasket 1. The user can take the holder 8 with his hand to conveniently install the gasket. The protection ring 7 is formed by two parts 9 connected with each other in any suitable manner by their sides 10 to produce a cavity 12 facing the central axis of the protection ring 7 and bounded by the inner surfaces 11 of the parts 9 (see fig.3). In this embodiment, parts 9 are symmetrical. One of the symmetrical parts 9 may be fixedly connected with the holder 8.

The annular sealing member 6 comprises a core ring 13 (preferably metal) and two flexible sealing rings 14 concentrically arranged on each side of the core ring 13, wherein the diameter of the flexible sealing rings 14 is smaller than the diameter of the core ring 13, therefore, the periphery 15 of the core ring 13 protrudes beyond the flexible sealing rings 14. The periphery 15 may be inserted in the cavity 12 of the protection ring 7. The annular sealing member 6 is coated with a coating 16 of porous polytetrafluoroethylene. The expanded graphite is well deformed material with stable characteristics. Deformation of the flexible sealing rings 14 made of expanded graphite may reach 10% the thickness of the annular sealing member 6. However, excessive deformation of the flexible sealing rings 14 may cause their disruption. In operation, the annular sealing member 6 is stuck between the faces of the flanges

3 and 4 in the flange connection 2. In operation, flanges 3 and 4 may apply excessive force to the flexible sealing ring 14. The flexible sealing ring 14 is deformable until the surface of the flexible sealing ring 14 becomes flush with the outer surface of the protection ring 7. Therefore, further compression along with disruption of the sealing gasket is prevented.

Wrapping of the annular sealing member 6 by a coating of porous polytetrafluoroethylene, further protects the ring against disruption and. The coating of the annular sealing member may be a one-layer coating (see fig. 3) made of polytetrafluoroethylene having a porosity 50 to 60% or a two-layer coating (see fig. 4), comprising an inner layer 17 of polytetrafluoroethylene having a porosity 30 to 40%, and outer layer 18 of polytetrafluoroethylene having a porosity 50 to 60%. Each layer of the coating is formed by wrapping the annular sealing member 6 by a coating tape made of porous polytetrafluoroethylene with overlapping and tensioning.

The one-layer coating of the annular sealing member made of polytetrafluoroethylene having a porosity 50 to 60 % may be wrapped with the coils of the coating tape overlapped with each other and, therefore, provides reinforcement of the annular sealing member. However, the coating with such porosity does not prevent the sealing ring from interaction with environment.

The one-layer coating of the annular sealing member made of polytetrafluoroethylene with porosity 30 to 40 % prevents the sealing ring from interaction with environment. However, the overlapped coils of the coating tape with such porosity being cannot adhere to each other.

The two-layers coating made of polytetrafluoroethylene with porosity 30 to 60 % prevent the annular sealing member 6 from interaction with environment, i.e. protect the ring from corrosion. The two-layers coating wherein the coils of the coating tape are overlapped with each other provides reinforcement of the gasket.

The exact number of the tape coils in each coating layer depends on how aggressive is the medium and on its parameters such as pressure and temperature. The more aggressive the medium is, and the higher the parameters are, the more tape layers shall be made. However, tests have shown that increasing the number of the layers over a certain limit does not lead to better isolation. In order to avoid swelling of the coating tape, each layer of the tape shall be wrapped with tensioning. Advantageously, the thickness of the coating tape made of porous polytetrafluoroethylene may be 0.25 mm or less.

Advantageously, the density of expanded graphite in the flexible sealing rings can be 1.2 to 1.8 g/cm³. When the density of expanded graphite is 1.8 g/cm³, deformation of the flexible sealing rings 14 reaches its maximum of 10% thickness of the flexible sealing ring. When the density of expanded graphite is less than 1.2 g/cm³ wrapping by the coating tape is difficult because the graphite is too weak. Further, the deformation of such flexible sealing ring 14 may not be enough to provide suitable sealing of flange connection 2 when the temperature is rapidly changing.

The flexible sealing ring 14 may be formed as corrugated band 20 of expanded graphite wrapped by the coating tape of porous polytetrafluoroethylene 19 (see fig. 5) with further pressing of the flexible sealing ring to produce the annular sealing member 6 with corresponding thickness. The coating tape is made of porous polytetrafluoroethylene with porosity 50 - 60% and thickness not more than 0.045 mm. In another embodiment, the flexible sealing gasket 14 comprises a ribbon reinforcing member 21 disposed between two corrugated bands 20 made of expanded graphite (see fig. 6). The ribbon reinforcing member 21 may be made of organic material, such as aramid, polyethylene, polypropylene and nylon, or inorganic material such as glass fibre or fabric with ceramic fiber, quartz fiber or carbon fiber, or may be made of metal foil, particularly, of stainless steel. The ribbon reinforcing member provides increased durability of the sealing gasket and does not change its flexibility which depends on the porosity of the expanded graphite.

The flexible sealing ring 14 may comprise a plurality of rings 22 with reinforcing members 23 disposed between the adjacent rings 22 (see fig.8). Each ring 22 can be formed of wrapped expanded graphite as described above for the flexible sealing ring 14. The reinforcing members 23 may comprise plain ring or perforated ring or may be made of a net. The reinforcing members 23 may be made of organic material, inorganic material or metal foil as noted above. The sealing gasket may comprise identification means 24 located on the holder 8 which identify operational conditions (sealing medium, temperature, pressure etc.) of the sealing gasket (see fig.9).

In a further embodiment of the sealing gasket, one of the parts 9 of the protection ring 7 comprises a circumferential segment 25 and at least one additional fastening member for fastening the annular sealing member 6 in the protection ring 7 (see fig. 10). The additional fastening member for fastening the annular sealing member 6 in the protection ring 7 may be a circumferential segment 26 profiled to match the corresponding part 9 of the protection ring 7 and removably secured on the protection ring 7 by means of tabs 27. Further, the additional fastening member for fastening the annular sealing member 6 in the protection ring 7 nay be a circumferential segment 28 profiled to match the corresponding part 9 of the protection ring 7, wherein the circumferential segment 28 is slidably mounted on the holder 8 and may be fixed on the protection ring 7 by means of tabs 30 (see fig. 11). Further, the additional fastening member for fastening the annular sealing member 6 in the protection ring 7 may comprise at least one holding member 31 fixedly mounted on one of the parts 9 of the protection ring 7 (see fig.12). Due to separable construction of the protection ring 7 (as shown on fig. 10-12) the annular sealing member 6 may be replaced with a new one or removed for repair of a damaged section by means of wrapping the section by the tape of porous polytetrafluoroethylene. Therefore, the protection ring 7 may be reused.

The sealing gasket with stationary mounted annular sealing member may be used in harmful conditions, such as chemical industry or nuclear power systems, where repair time shall be minimized and any failures of the sealing gasket shall be eliminated.

Claims

Claims:

1. A sealing gasket for sealing a flange connection, the sealing gasket comprising an annular sealing member which comprises a core ring and two flexible sealing rings concentrically arranged on each side of the core ring, wherein the diameter of the flexible sealing rings is smaller than the diameter of the core ring, so that the core ring has an outwardly projecting edge, characterized in that the sealing gasket further comprises a protection device formed as a ring, the protection device having a circumferential cavity facing the central axis of the protection device, wherein the protection device is adapted to be mounted on the periphery of the core ring with the projecting edge of the core ring inserted into the circumferential cavity of the protection device, and wherein the maximum thickness in the axial of the protection device is less than the thickness of the annular sealing member.

2. A sealing gasket as claimed in claim 1, wherein the annular sealing member is coated with a coating of porous polytetrafluoroethylene, and each flexible sealing ring is a corrugated band of expanded graphite wrapped by a coating tape of porous polytetrafluoroethylene.

3. A sealing gasket as claimed in claim 1, comprising a radial holder for installation of the sealing gasket, wherein the holder is connected with the protection device and protrudes beyond the flanges of the flange connection when the sealing gasket is installed.

4. A sealing gasket as claimed in claim 1, wherein the protection device is separable at least into two parts.

5. A sealing gasket as claimed in claim 4, wherein at least one part of the protection device is a ring connected with another part at its side.

6. A sealing gasket as claimed in claim 5, wherein the two parts of the protection device are symmetrical.

7. A sealing gasket as claimed in claim 3, characterized in that, it comprises an identification means applied to the holder.

8. A sealing gasket as claimed in claim 4, wherein one part of the protection device comprises a circumferential segment and at least one additional fastening member for fastening the annular sealing member in the protection device.

9. A sealing gasket as claimed in claim 8, wherein the additional fastening member for fastening the annular sealing member in the protection device is a circumferential segment profiled to match the protection device and removably secured on the protection device.

10. A sealing gasket as claimed in claim 9, wherein the additional fastening member for fastening the annular sealing member in the protection device comprises at least one holding member fixedly mounted on one of the symmetrical rings of the protection device.

11. A sealing gasket as claimed in claim 10, wherein the additional fastening member for fastening the annular sealing member in the protection device comprises a circumferential segment profiled as the symmetrical rings of the protection device, wherein the circumferential segment is slidably mounted on the holding member and adapted to be fixed on the protection device.