GB2229047A

GB2229047A - Conducive PTFE/graphite gasket

Info

Publication number: GB2229047A
Application number: GB8902038A
Authority: GB
Inventors: Peter Allcock; Richard Mark Walker
Original assignee: CHEMICAL REACTOR SERVICES Ltd
Current assignee: CHEMICAL REACTOR SERVICES Ltd
Priority date: 1989-01-31
Filing date: 1989-01-31
Publication date: 1990-09-12
Anticipated expiration: 2009-01-31
Also published as: GB8902038D0; GB2229047B

Abstract

A PTFE envelope earthing gasket is provided which has an insert 21 comprising graphite. In a preferred embodiment, the gasket 14 comprises an envelope 20 of polytetrafluoroethylene which defines a cavity therein. Within the cavity there is located an insert 21 which consists of semi-rigid laminated graphite material 22 with a thin nickel reinforcement layer 23 and a corrugated steel ring strengthener 24. An earthing tag 15 may be connected to the steel ring 24. The invention reduces static electricity problems in pipework and vessels. <IMAGE>

Description

EARTHING GASKETS This invention relates to earthing gaskets and is particularly, although not exclusively concerned with conductive polytetrafluoroethylene envelope earthing gaskets.

Process industries have long been troubled with the problem of the generation of static electricity in pipe work and vessels, often with devastating results from the ignition of flammable fluids by a spark.

It is known to use conductive gaskets in the flanges of vessels and pipe work, which gaskets are electrically connected to earth, to prevent any charge from building up in the flange. These conductive gaskets comprise a polytetrafluoroethylene envelope containing an insert of conductive compressed asbestos which acts as the conductor.

It is an object of the invention to provide a conductive gasket which exhibits lower electrical resistance than the prior gaskets and which is therefore more efficient at discharging static electricity.

Accordingly, the present invention provides a conductive PTFE envelope earthing gasket which has an insert comprising graphite.

Preferably the graphite is reinforced.

Preferably the insert comprises nickel-reinforced graphite.

The gasket may be of uniform thickness.

Alternatively the cross-section of the gasket may taper inwardly towards its inner radius. There may be an earthing tag. The earthing tag may extend radially outwardly from the gasket.

The earthing tag may be electrically connected to the gasket.

The insert material may comprise a single layer.

The insert material may comprise two layers with a strengthener sandwiched therebetween.

The earthing tag may be electrically connected to the strengthener.

The strengthener may comprise a corrugated steel ring.

Preferably, the gasket may comprise an envelope of polytetrafluoreoetheylene which defines a cavity in which is located the insert, which insert consists of semi-rigid laminated graphite material with a thin nickel reinforcement layer and a corrugated steel ring to act as a strengthener.

Specific embodiments of the invention will now be described by way of example and with reference to the following drawings in which : Figure 1 is a section through a joint in some piping incorpoaring a first embodiment of gasket according to the invention; Figure 2 is a cross section through the first embodiment of gasket; and Figures 3 and 4 are more detailed cross-sections through additional embodiments of gasket according to the invention.

More specifically and with reference to Figure 1, the flanges 10 of pipe sections 11 are bolted together by four bolts 12. The pipe sections 11 and flanges 10 are lined with glass 13, or other non-conductive lining material and between the flanges 10 is located an annular conductive gasket 14 (shown in greater detail in Figure 2).

A stainless steel earthing tag 15 extends radially outwardly from the annular gasket 14 and is connected, via a conducting wire 16 to a suitable earth location 17. Charge accumulating on the flange(s) or walls of the pipe section(s) will be conducted away through the earthing tag and the conducting wire to earth.

Referring to Figures 2 and 3, the gasket 14 comprises an envelope 20 of polytetrafluoroethylene which defines a cavity therein as shown. In Figure 3 in the cavity defined by the PTFE envelope 20 is located the Insert 21 which consists of semi-rigid laminated graphite material 22 with thin nickel reinforcement layer (0.0005 ins.) 23, and a corrugated steel ring strengthener 24. Also shown is the earthing tag 15 connected to the steel ring 24. There is a layer of the reinforced material 22 on each side of the ring 24.

Figure 4 shows an alternative configuration for the structure of the gasket in which the thickness of the gasket tapers inwardly towards its inner radius, the layers of insert material meeting at the region of the inner radius.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A conductive PTFE envelope earthing gasket which has an Insert comprising graphite.

2. A gasket as claimed In Claim 1, in which the graphite is reinforced.

3. A gasket as claimed in Claim 2, in which the insert comprises nickel-reinforced graphite.

4. A gasket as claimed in any one of the preceding Claims, of uniform thickness.

5. A gasket as claimed in any one of Claims 1 to 3, in which the cross section of the gasket tapers inwardly towards its inner radius.

6. A gasket as claimed In any one of the preceding Claims, having an earthing point.

7. A gasket as claimed In Claim 6, In which the earthing point comprises a tag.

8. A gasket as claimed in Claim 7, in which the tag Is electrically connected to the gasket.

9. A gasket as claimed In any one of the preceding Claims, In which the insert comprises a single layer.

10. A gasket as claimed in any one of Claims 1 to 8, in which the insert comprises two layers with a strengthener sandwiched therebetween.

11. A gasket as claimed In Claim 10, when dependent on Claim 8, In which the earthing tag is electrically connected to the strengthener.

12. A gasket as claimed In Claim 10 or Claim 11, In which the strengthener comprises a corrugated steel ring.

13. A conductive earthing gasket comprising an envelope of polytetraf luoroethylene which defines a cavity In which Is located an Insert, which Inserts consists of semi-rigid laminated graphite material with a thin nickel reinforcement layer and a corrugated steel ring to act as a strengthener.

14. A gasket constructed and arranged substantially as herein described, with reference to Figures 1 and 2, or Figure 3, or Figure 4 of the accompanying drawings.