GB2280939A

GB2280939A - Gas pipe end fitting

Info

Publication number: GB2280939A
Application number: GB9416091A
Authority: GB
Inventors: Graham Oxtoby
Original assignee: KONTITE UK Ltd
Current assignee: KONTITE UK Ltd
Priority date: 1993-08-12
Filing date: 1994-08-09
Publication date: 1995-02-15
Also published as: GB9416091D0; GB9316734D0

Abstract

An end fitting for a gas pipe in which a plastic pipe is inserted into an existing metal pipe 1 comprises an adaptor 3 for receiving an end of the inner plastic pipe. An annular compression cone 5, provided with teeth 5a on its inner surface, locates over the plastic pipe. The compression cone 5 is compressed by a bell-shape securing ring 7 which at one end is screwed onto the adaptor 3. The other end of the securing ring 7 receives a coupling 13 is screwed onto the outer pipe 1. An insulating annular element 11 is provided between the coupling 13 and the securing ring 7 to electrically insulate the second pipe 2 from the securing ring 7. <IMAGE>

Description

Pine Joints and Fittings This invention relates to pipe joints and to fittings useful in connecting sections of pipe together.

More specifically this invention is concerned with a fitting useful in the conversion of existing metal gas service pipes to plastic pipes and wherein an electrical insulation break is provided.

In one method of replacement of metal gas service pipes a plastic pipe is inserted into an existing metal pipe bore in a generally coaxial manner with the end being terminated in a compression joint on the plastic pipe, a threaded coupling being used to connect with the outer metal pipe. This invention seeks to provide an improved construction for such a fitting.

In accordance with this invention, there is provided a pipe end fitting and coupling comprising a pipe end adaptor including a bore at one end adapted to receive a first (plastic) pipe, a securing means threadably engaging the adaptor and operatively associated with a compression cone for sealingly securing the said first pipe in the bore, the securing means having an end to sealingly receive one end of a coupling, the other end of the coupling sealingly engaging a second outer (metal) pipe coaxial with the first inner pipe and wherein the second pipe is electrically insulated from the securing means.

In a preferred embodiment the coupling is mounted within a bell-mouth end of the securing means using an electrically insulating compound, preferably a compound which is cast in situ.

This invention also provides a method for conversion of an existing metal gas service supply pipe to a plastic service supply pipe by insertion of the plastic pipe inside the metal pipe which method is characterised by the use of a pipe end fitting and coupling comprising a pipe end adaptor including a bore at one end adapted to receive the first (plastic) pipe, a securing means threadably engaging the adaptor and operatively associated with a compression cone for sealingly securing the said first pipe in the bore, the securing means having an end to sealingly receive one end of a coupling, the other end of the coupling sealingly engaging the second outer (metal) pipe coaxial with the first inner pipe and wherein the second pipe is electrically insulated from the securing means.

In a further aspect of this invention there is provided a replacement service head coupling adaptor for gas mains wherein the adaptor body comprises two metallic components with an electrical insulation joint therebetween.

In a preferred embodiment there is provided a pipe end fitting and coupling wherein the adaptor has a through bore with a shouldered abutment for an end of the plastic pipe, an annular.compression cone located over the pipe with a tapered outer surface cooperating with a tapered entrance surface to the bore, an inner surface of the cone adjacent the pipe having teeth, the securing means having an annular shoulder to abut the rear of the cone to drive the teeth into the plastic pipe by virtue of the cooperating taper surfaces as the securing means is screwed on to the adaptor, the end of the securing means developing in a bell-mouth and threadably or fixedly engaging the one end of the coupling with an interposed electrically insulating annular element, the other end of the coupling including a threading or coupling to receive an end of the metal pipe.

Preferably an annular cavity is provided between the one end of the coupling and the securing means, the cavity being filled with a rigid electrically insulating compound forming an integral mechanical connection between the coupling and securing means.

In an embodiment the one end of the coupling includes formations, such as screw threading, on an outer surface which form an interlock with the electrically insulating compound.

Advantageously an inner peripheral surface of the end of the adaptor includes formations, such as screw threading, to form an interlock with the electrically insulating compound.

Further features and advantages of this invention will now be described by way of an example and a modification thereof shown in the accompanying drawings.

In the drawings: Figure 1 shows a longitudinal cross section through a pipe end adaptor coupling, and Figure 2 shows a detailed view of a modification.

Referring to Figure 1 of the drawings, a gas pipe fitting is shown which is to be used for so-called live or dead service insertion wherein an existing copper or steel gas service pipe 1 has located therein as a replacement a polyethylene gas pipe 2 which extends from the main service branch to a consumer in, for example, a domestic property.

A pipe end adaptor 3 is provided which has a bore with a counter bore 4 into which the end of the plastic pipe 2 may be located. The pipe 2 is secured by a compression cone 5 having teeth 5a and which is forced in an axial direction by an annular abutment 6 on a securing means 7 which threadably engages the end 8 of the adaptor 3. The securing means 7 has a bell-mouthed end 10 which serves for the reception of an insulation material 11 in turn supporting one end 12 of a coupling 13. The other end 14 of the coupling 13 has a threaded bore 15 which engages the threaded end 16 of the existing metal pipe 1.

The insulating material 11 may be provided between two metal parts of the construction other than a bellmouth 10 which is adapted to receive the end 12 of the coupling 13.

The plastic pipe 2 will be supported by an insert tube 17 in the zone of the compression fitting 5. A port 18 may be provided in the coupling 13 for the purpose of injecting a sealant compound into the coaxial space between the pipes 1 and 2.

The insulating material 11 will be selected to have good electrical insulation properties whilst having sufficient mechanical strength to meet the requirements of adequately supporting the coupling 13 within the securing means 7.

The insulating material 11 may be injected and formed in situ in which case the metal components are provided with appropriate formations to give adequate strength to the connection and avoid separation or alternatively the insulant 11 may be cast into the end 10 and provided with suitable threading for connection with the coupling 13.

Figure 2 shows a modified construction wherein the end 14 of the coupling 13 has a compression nut 19 with a compression cone 20 which serves to secure the pipe 1.

Claims

1. A pipe end fitting and coupling comprising a pipe end adaptor including a bore at one end adapted to receive a first (plastic) pipe, a securing means threadably engaging the adaptor and operatively associated with a compression cone for sealingly securing the said first pipe in the bore, the securing means having an end to sealingly receive one end of a coupling, the other end of the coupling sealingly engaging a second outer (metal) pipe coaxial with the first inner pipe and wherein the second pipe is electrically insulated from the securing means.

2. In a method for conversion of an existing metal gas supply pipe to a plastic pipe by insertion of the plastic pipe inside the metal pipe the use of a pipe end fitting and coupling comprising a pipe end adaptor including a bore at one end adapted to receive a first (plastic) pipe, a securing means threadably engaging the adaptor and operatively associated with a compression cone for sealingly securing the said first pipe in the bore, the securing means having an end to sealingly receive one end of a coupling, the other end of the coupling sealingly engaging a second outer (metal) pipe coaxial with the first inner pipe and wherein the second pipe is electrically insulated from the securing means.

3. A pipe end fitting in accordance with Claim 1 or as used in the method of Claim 2, wherein the coupling is mounted within a bell-mouth end of the securing means using an electrically insulating compound, preferably a compound which is cast in situ.

4. A pipe end fitting and coupling as set forth in any preceding claim, wherein the adaptor has a through bore with a shouldered abutment for an end of the plastic pipe, an annular compression cone located over the pipe with a tapered outer surface cooperating with a tapered entrance surface to the bore, an inner surface of the cone adjacent the pipe having teeth, the securing means having an annular shoulder to abut the rear of the cone to drive the teeth into the plastic pipe by virtue of the cooperating taper surfaces as the securing means is screwed on to the adaptor, the end of the securing means developing in a bell-mouth and threadably or fixedly engaging the one end of the coupling with an interposed electrically insulating annular element, the other end of the coupling including a threading or coupling to receive an end of the metal pipe.

5. A pipe end fitting in accordance with any preceding claim, wherein an annular cavity is provided between the one end of the coupling and the securing means, the cavity being filled with a rigid electrically insulating compound forming an integral mechanical connection between the coupling and securing means.

6. A pipe fitting in accordance with Claim 5, wherein the one end of the coupling includes formations, such as screw threading, on an outer surface which form an interlock with the electrically insulating compound.

7. A pipe fitting in accordance with Claim 5 or 6, wherein an inner peripheral surface of the end of the adaptor includes formations, such as screw threading, to form an interlock with the electrically insulating compound.

8. A pipe fitting or coupling constructed substantially as herein described and as exemplified with reference to the drawings.

9. A method for conversion of an existing metal gas supply pipe to a plastic pipe substantially as described herein and exemplified with reference to the drawings.