GB2460912A

GB2460912A - An annular gasket

Info

Publication number: GB2460912A
Application number: GB0902430A
Authority: GB
Inventors: Brian Rex; Andrew Benson
Original assignee: Crane Ltd
Current assignee: Crane Ltd
Priority date: 2008-06-19
Filing date: 2009-02-13
Publication date: 2009-12-23
Anticipated expiration: 2029-02-13
Also published as: GB2460912B; GB0902430D0

Abstract

An annular gasket has a sealing surface 21. A series of parallel, substantially equally spaced annular ribs 22a, 22b extend annularly across the sealing surface 21. A second series of ribs 23 cross the ribs 22a, 22b to produce a waffle pattern. The ribs define a plurality of square perimeters which seal against a target pipe surface (not shown) and Isolate deep score marks, cracks or crevices from each other thereby preventing the spread of leaks by tracking. As can be seen from the cut edge, the ribs have a substantially arcuate or domed cross section 24. The gasket has a substantially L shaped cross section.

Description

NOVEL GASKET

The present invention relates to a novel gasket design with application in a variety of applications for example but not limited to; the sealing of flange adaptors, pipe couplings or repair clamps in service mains for water gas or other fluid supplies.

Couplings, flange adapters and other mechanical fittings of various designs are known for use in the connection of pipes of same or different materials and diameters, or to connect pipes to flanged products such as valves, bends tees or other such flanged pipe work.

A typical coupling might comprise a centre sleeve with its ends formed to receive an annular gasket which in turn is abutted to an end ring. The gasket is energised by compression provided by.fastener means which generally draw the end ring and sleeve together against the gasket.

In one conventional design, the fastener means comprises a plurality of nut and bolt assemblies axially aligned and spaced around the circumference of the end ring. The nut and bolt assemblies are typically received through lugs designed to receive the assemblies.

Various fastener arrangements are known, for example fasteners may extend over the entire length of a coupling. In other popular arrangements, the bolts may connect between the end ring and a lug extending radially from an end of the sleeve.

In all fastener arrangements, gaskets are included to provide a seal between the outer circumferential surface of the pipe and the end of the sleeve of the coupling.

Gaskets come in a wide range of cross sections and sizes for example but without limitation; a wedge, trapezoid, square, rectangle, round, L shape or U shape cross section. They can be of solid construction, hollowed or reinforced internally or externally with more rigid materials to the material of the main gasket body such as metal or plastic.

Known gaskets typically comprise of an elastomeric or polymeric material having a hardness which is less than that of the predominant material used in the coupling and also is less than the hardness of the material of the target pipe.

Common gaskets are provided from a synthetic rubber having a hardness in the range 50 IRHD to 80 IRHD.

These relatively soft compounds assist sealing on uneven pipe surfaces (for example, cracked or creviced due to corrosion) by flowing into crevices. These soft compounds are less well suited in couplings used to U..

seal a wide range of pipe diameters within the same coupling. In these applications, a softer compound flows easily into any gap between the *..

* pipes and the inner wall of the coupling which has the effect of *.* dramatically reducing the sealing capacity of the gasket. Because of this, harder compounds (typically in the region of 80 IRHD) are used and *:*. employed to resist unwanted extrusion of the gasket between the inner wall of the coupling and the outer circumferential surface of the pipe.

However, whilst the harder compounds obviate the unwanted extrusion problem, they have reduced effectiveness in sealing on heavily corroded (uneven) pipe surfaces. To compensate for this, couplings have been designed to provide for increased gasket loading by means of fasteners. A consequence of this is that additional material is required in the coupling components to resist the larger loads placed on the fasteners.

It is also known to introduce a plurality of small annular ribs around the surface which defines the sealing bore of an annular gasket. This serves to increase gasket pressure on a pipe locally but where pipes had deep score marks, cracks or crevices in multiple positions radially and axially, content from the pipe could escape from one defect and track via the annular grooves between the ribs to another (and another, and so on..). Where one or more of these defects traverse a rib of the gasket, eventually * external leakage of content can result.

With recent improvements in "sniffers" used by the gas industry to detect minor traces of gas leaks (at previously undetected levels of 3Oppm and less), it has come to light that conventional gaskets occasionally do not provide adequate sealing on all defective pipe surfaces.

The present invention seeks to provide a gasket which is suited both to sealing pipe joints between pipes of significantly different outside diameters and to sealing damaged pipes with multiple deep score marks, "I. cracks or crevices in their outer circumferential surface.

* In accordance with the present invention, there is provided an annular gasket having a sealing surface designated for sealing against an uneven pipe surface or pipe joint the sealing surface being provided with a raised pattern of geometric shape perimeters.

The gasket may have any known cross section.

The raised pattern may, for example, comprise one or more of the following shapes; squares, circles, diamonds, rectangle, polygon or other geometric shape which describes an enclosed area. The shapes may be of substantially equal size or a plurality of sizes. The pattern may be random or repeating.

In use the shape perimeters compress against and seal an underlying pipe surface and at least partly invade deep score marks, cracks or crevices. As the perimeters each define an enclosed area and are spaced apart across the pipe surface, the opportunity for leakage to track between shapes and from one end of the gasket to another is considerably reduced compared to ribbed gaskets. Pipe surface defects are contained locally within shape perimeters and prevented from permeating or spreading to other defects.

The raised shape perimeter walls can be minor or substantial in height but desirably they have a height of at least 1.5mm and a width to height ratio of at least 1:1. The raised shape perimeter walls may be of square cross section or buttress, triangular, domed or other shape. Other possible shapes include, without limitation; polygonal and acme thread form.

Optionally, more than one cross section may be used on a given sealing surface, for example but without limitation, in a waffled configuration circumferentially extending walls may take a buttress or acme thread from, whilst axially extending walls are of square, triangular, domed or : other geometrical shape. Various combinations of wall cross section can be envisaged and selected to best suit manufacturing requirements and/or end use.

It will be appreciated that the greater the height of the wall, the greater ** the sealing ability of the seal on damaged pipe surface. S. S * S S * S.

The inventors have found that in demonstrations gaskets in accordance with the invention create a substantially better seal than prior art gaskets used for the same application. A standard prior art gasket was compared with a gasket in accordance with the present invention on knurled and grooved test pipe as specified by the UK gas industry (GIS LC8 part 4).

This surface topography is intended to represent corroded pipe surfaces on iron or steel mains and can also be used to represent typical pipe scoring experienced on plastic pipe.

The prior art gasket experienced substantial leakage at less than 0.1 bar, the novel gasket achieved a leak tight seal at 7 bar.

A further advantage of the novel gasket design is that it permits fabrication of the gasket from harder compounds reducing the occurrence of unwanted extrusion between pipe and coupling whilst providing much improved sealing on defective pipe surfaces compared to prior art gaskets.

Previously filed UK patent application number 0811263.3 from which this application claims priority describes one embodiment of coupling in which a gasket in accordance with the invention can conveniently be used, though the gasket has potential application in a wide range of couplings, clamping devices and adapters.

Preferably the sealing surface of the gasket comprises natural rubber or synthetic rubber. Suitable synthetic rubbers include EPDM or Nitrile in a * *** hardness range of from about 5OIRHD to about 80 IRHD. *S*.

S ****

* Desirably, the sealing surface has a hardness in the range from 7OIRHD to IRHD. *.*. **S.

*:*. The invention will now be described with reference to the following Figures in which: Figure 1 illustrates a ribbed sealing surface of a gasket as known in the

prior art.

Figure 2 illustrates a first embodiment of a gasket in accordance with the present invention.

Figure 3 illustrates a second embodiment of a gasket in accordance with the present invention Figure 4 illustrates a third embodiment of a gasket in accordance with the present invention Figure 1 shows a section of a prior art annular gasket viewed from its sealing side. The gasket is trapezoidal in cross section. As can be seen, the gasket has an inner, annular sealing surface 1 along which are provided a series of parallel, substantially equally spaced ribs 2a, 2b, 2c.

Figure 2 shows a first embodiment of the invention. Again the gasket is annular and is shown in a section viewed from the sealing side. As can be seen, the gasket has an annular sealing surface 21. A series of parallel, substantially equally spaced annular ribs 22a, 22b extend annularly across the sealing surface 21. A second series of ribs 23 cross the ribs 22a 22b S...

: to produce a waffle pattern. The ribs define a plurality of square perimeters which seal against a target pipe surface (not shown) and isolate deep score marks, cracks or crevices from each other thereby preventing the spread of leaks by tracking. As can be seen from the cut edge, the ribs have a substantially arcuate or domed cross section 24. The gasket has a substantially L shaped cross section. * *. * S.

Figure 3 shows an alternative embodiment of the invention. As can be seen, the gasket has an annular sealing surface 31. A series of parallel, substantially equally spaced annular ribs 32a, 32b extend annularly across the sealing surface 31. A second series of ribs 33 cross the ribs 32a, 32b to produce a waffle pattern. The ribs define a plurality of elongate rectangle perimeters which seal against a target pipe surface (not shown) and isolate deep score marks, cracks or crevices from each other thereby preventing the spread of leaks by tracking. As can be seen from the cut edge, the ribs have a substantially trapezoidal or buttress cross section 34. The gasket has a substantially trapezoidal shaped cross section 35.

Figure 4 illustrates the gasket as described in Figure 5 of previously filed UK patent application number 0811263.3 from which this patent application claims priority. The figure shows a section of a gasket 4 in accordance with the invention. As can be seen the annular gasket has a substantially L shaped cross section. Moulded into the sealing surface are a plurality of circumferentially arranged ribs 41a, 41b, 41c and a plurality of axially extending ribs 42 crossing the circumferentially arranged ribs.

The crossed ribs define a plurality of pockets 43 which assist in sealing in leaks on deeply pitted or corroded pipe. An annular recess 44 on the reverse side of the sealing surface receives a gripping or support ring (not shown). The ribs 41a, 41b, 41c can be seen to have a substantially square cross section. * * * ** * *as. * S **. S...

I S...

S 5*5 S. *5 S

S S S S.

Claims

SCLAIMS1. An annular gasket having a sealing surface designated for sealing against an uneven pipe surface or pipe joint the sealing surface being provided with a raised pattern of geometric shape perimeters.
2. A gasket as claimed in claim 1 wherein the raised pattern comprises shapes selected from; squares, circles, diamonds, rectangle, polygon or other geometric shape which describes an enclosed area.
3. A gasket as claimed in claim 2 wherein the shapes are of substantially equal size.
4. A gasket as claimed in any preceding claim wherein the raised pattern is repeating. S...
5. A gasket as claimed in claim 4 wherein the shapes are quadrilateral and form a waffled surface. S...
6. A gasket as claimed in any preceding claim wherein the raised shape perimeter walls have a height of at least 1.5mm and a width to height ratio of at least 1:1.
7. A gasket as claimed in any preceding claim wherein the raised shape perimeter walls have a cross section selected from; square, buttress, trapezoidal, triangular, domed, polygonal and acme thread form.
8. A gasket as claimed in any preceding claim wherein more than one cross section of wall is employed on the sealing surface.
9. A gasket as claimed in any of claims 5 to 8 wherein circumferentially extending walls may take a buttress or acme thread from and axially extending walls are of square, triangular, domed or other geometrical shape.
10. A gasket as claimed in any preceding claim wherein the sealing surface of the gasket comprises natural or synthetic rubber.
11. A gasket as claimed in claim 10 wherein the material of the sealing surface is selected from include EPDM and Nitrile and has a hardness in a hardness in the range of from about 5OIRHD to about IRHD.
12. A gasket as claimed in any preceding claim wherein the material of the sealing surface has hardness in the range from 7OIRHD to 80 IRHD. * * * ** S S... * S *5..* *5*I I..S S. IS S. S S * S S S.