WO1995025916A1

WO1995025916A1 - Pressure-retention gasket

Info

Publication number: WO1995025916A1
Application number: PCT/GB1995/000637
Authority: WO
Inventors: David Vatcher; Iain Laird
Original assignee: Raychem Limited
Priority date: 1994-03-24
Filing date: 1995-03-22
Publication date: 1995-09-28
Also published as: AU1954895A; GB9405808D0

Abstract

Use of a wire mesh carrying gel material as a pressure-retention gasket, for example between the connecting flanges of pressurised pipes. The relatively soft gel is unexpectedly retained in position against the applied pressure.

Description

PRESSURE-RETENTION GASKET

This invention relates to a pressure -retention gasket for compression between two surfaces, for example the coupling flanges of pressurised piping, to prevent passage of pressurised fluid (gas or liquid) therebetween.

Pressure-retention gaskets are usually made from solid sheet materials, but it has unexpectedly been found, according to the present invention, that pressure-retention can be achieved by providing a gasket comprising a foraminated layer of relatively crush- resistant material carrying gel material, the foraminated layer being sufficiently crush-resistant to retain the gel material in at least some its foramina when compressed between two pressure-retention surfaces in use and the gel material being present in sufficient quantity to seal substantially all the residual space in the gasketted region between the said two surfaces.

This pressure-retention gasket has the advantage that it can compensate for slight irregularities in the gasket-compressing surfaces, for example irregularities caused by corrosion of the coupling flange surfaces of pressurised pipes and may resist further corrosion of the surfaces. The use of the present gasket for such pressure-retention applications thus avoids or defers expensive re¬ dressing of the irregular surfaces to regain a good pressure-retaining seal. Surprisingly, the gel is not simply displaced by the retained fluid pressure acting along leak paths which will tend to exist within and/or alongside the foraminated layer.

The foraminated layer may for example be a woven or non- woven or porous sheet. The crush-resistant material of the foraminated layer may be selected according to the pressure to be applied during compression of the gasket in use. Polymeric materials may be suitable in some applications, but for pressurised pipe flanges it may be preferable to use metal, for example a knitted or woven metal mesh or other foraminated metal sheet, possibly of perforated or stamped or non-woven-fibrous construction.

The gel material, preferably comprising an organic polymer, is characterised by having greater cohesive strength than adhesive strength and a cone penetration value from 50, preferably 100, to about 400, preferably 350, (10^{" l} mm) as measured by ASTM D-937- 77, and an ultimate elongation of at least 100%, preferably at least 200%, as determined by ASTM D-412. Highly liquid -extended polymers may be useful as the gel, as may other material satisfying the above criteria or satisfying the test requirements indicated in published international patent application WO88/00603, the disclosure of which is incorporated herein by reference.

Preferred gel materials and gaskets using them are described for E.M.I, shielding and environmental sealing purposes in EP-A- 0275171, the disclosure of which is incorporated herein by reference. It is surprising that such electrical shielding gaskets, which are designed only to resist accidental environmental contamination, e.g. by liquid splashed on the shielded equipment, can be used for pressure-retention, e.g. in high pressure pipe systems, according to the present invention. The present invention accordingly includes the novel use of a gasket as hereinbefore described or as described in EP- A-0275171 as a pressure-retention gasket. The invention also includes a method of providing a pressure-retention seal between two surfaces wherein a gasket as hereinbefore described or as described in EP-A-0275171 is compressed between the said two surfaces to a degree enabling the resulting seal to retain the pressure in question.

By providing electrical continuity across the pipe joints, the electrically conductive gaskets may achieve the additional advantage of reducing the number of earthing straps required for a given pipe system. The pressure to be retained by the pressure -retention gasket of this invention will often be higher than the surrounding ambient pressure, as for example in the aforementioned pressurised pipe systems, but may also be less than the ambient pressure, as for example in vacuum or low-pressure apparatus. In either sense, the pressure differential to be retained will preferably be at least 0.25 atmospheres, more preferably at least 0.5, 0.75, or 1.0 atmospheres, and may be higher up to several, or even tens of atmospheres, or more depending on suitable gasket materials according to the invention being available.

Embodiments of the gasket and the use and method according to the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figures la, lb and lc show a gasket of the present invention wherein the foraminated layer is contained within the gel material, and Figure 2 shows the gasket installed between two surfaces.

Referring to the drawings , Figures la and lb show a fabric which is woven from wires 1. As shown in Figure lc, the woven metal fabric containing wires 1 is encapsulated in the cured gel 2. In Figure 2 the gasket of Figure lc is installed and compressed between surfaces 3. Due to the compression, metal wires 1 contact the surfaces 3 at points 5 and the gel has been compressed and expanded into areas 4. As can be seen in Figure Id, the gel environmentally seals between surfaces 3 and encapsulates and environmentally protects the woven metal fabric formed from wires 1.

Claims

CLAIMS:

1. A pressure-retention gasket comprising a foraminated layer of relatively crush-resistant material carrying gel material, the foraminated layer being sufficiently crush-resistant to retain the gel material in at least some of its foramina when compressed between two pressure-retention surfaces in use, and the gel material being present in sufficient quantity to seal substantially all the residual space in the gasketted region between the said two surfaces.

2. A gasket according to claim 1, wherein the foraminated layer is made of metal, preferably a metal mesh.

3. A gasket according to claim 1 or 2, wherein the gel material has greater cohesive strength than adhesive strength, a cone penetration value of from 50, preferably 100, to 400, preferably 350, (10^{_ 1} mm) as measured by ASTM D-937-77, and an ultimate elongation of at least 100%, preferably at least 200%, as measured by ASTM D-412.

4. A gasket according to any of claims 1 to 3 as described in EP-A- 0275171.

5. A gasket according to any preceding claim which in use provides electrical continuity between the two pressure -retention surfaces.

6. A gasket according to any preceding claim in use under compression between two pressure-retention surfaces.

7. A method of providing a pressure-retention seal between two surfaces wherein a gasket according to any of claims 1 to 5 is compressed between the said two surfaces to a degree enabling the resulting seal to retain the pressure in question.

8. The use of an electrical gasket as described and claimed in EP- A-0275171 as a pressure-retention gasket.