GB2324132A

GB2324132A - Outer and inner pipe construction with end insert

Info

Publication number: GB2324132A
Application number: GB9726731A
Authority: GB
Inventors: Stewart Mcpherson
Original assignee: Fusion Group PLC
Current assignee: Fusion Group PLC
Priority date: 1996-12-27
Filing date: 1997-12-19
Publication date: 1998-10-14
Also published as: GB9627004D0; GB9726731D0

Abstract

The pipe comprises an outer host pipe 1, e.g of plastics, an inner guest pipe 3, each of a material to provide a particular required attribute, and a pipe insert 5 of a material weld-compatible with the material of the outer host pipe, the pipe insert being inserted in the end of the inner guest pipe and having an outermost flange 8 to overlie the outer edge of the inner guest pipe. The flange can extend to an outer wall 9 locatable in an outer end recess 10 in the host pipe 1. Two such pipes 1,2 with inserts 5,6 are joined by an electro-fusion coupling sleeve 11.

Description

PIPES This invention relates to pipes, and is particularly concerned with pipes needing an attribute not readily available from a single material.

It is the case that hitherto, pipes have been formed of a material suited to a particular primary purpose, but which can have an inherent disadvantage that has to be accepted and tolerated if the pipes are put to an alternative usage. Thus, for example, in the supply of hazardous fluids, such as petrol, plastics pipes as are widely employed in the gas and water industries, cannot be used in all circumstances because, as is the case with many polymers, they are permeable and allow gases and liquids to pass through them. Permeation through the wall of a pipe should not be considered as the pipework leaking, since the rate at which such permeation takes place is very slow and dependent on factors such as thickness, temperature etc.

Whilst it is true that the rate of permeation is very slow, in some applications it is considered unacceptable. In such applications there is a requirement to minimise or even eliminate such permeation.

In addition to those applications where it is necessary to control the permeation from the inside to the outside of the pipework, such as in the transportation of fuels e.g. petrol, there are also applications where it is necessary to control the permeation from the outside to the inside, such as water supply pipes passing through sites that contain undesirable leachates that would be harmful to water supplies or similar liquids being transported.

In an attempt to provide the total elimination of permeation from inside the pipe to the outside, and from outside the pipe to the inside, metal pipes have been employed and the difficulties of rusting and necessary employment of threaded joints between pipes that cannot be guaranteed to be leakproof, have had to be tolerated.

There are other areas for which plastics pipes would be ideal but for the fact that they have an inherent flexibility and other factors such as roundness are poor that would need to be significantly improved.

It has already been proposed such as in for example UK Patent Application 9605703.9 to combine the attributes of two different materials each to serve its own particular purpose by having an outer or host pipe of one material and an inner or guest pipe of a different material.

Thus for example conventional plastics pipes have notable advantages. They are rustproof, and able to resist mechanical and frost damage. They are relatively easy to secure together in fluid- tight manner by mechanical joints, and particularly by electrofusion and butt-fusion techniques. Ideal to the supply of, for example, petrol, would be an aluminium alloy pipe, lighweight and strong, and immune to attack and permeation by petrol. Consequently, an,i in accordance with the proposals of the prior application, a pipe length can be formed by a host pipe of conventional plastics material and a guest pipe of aluminium alloy, thereby achieving the advantages of both materials in one pipe.

Such a construction still leaves the potential difficulty of having the inner guest pipe of one length not directly secured to the inner guest pipe of an adjacent length. The securing of the ollter host pipes together whilst being totally leak proof can only be said to minimise considerably but not eliminate totally permeation outwardly of or inwardly of the pipes at the location ofajoint.

It is the object of the present invention to improve still further the outer host and inner guest pipe construction of the prior Patent Application mentioned above.

According to the present invention a pipe comprises an outer host pipe, an inner guest pipe, each of a material to provide a particular required attribute, and a pipe insert of a material weld-compatible with the material of the outer host pipe, the pipe insert being inserted in the end of the inner guest pipe and having an outermost flange to overlie the outer edge of the inner guest pipe. Preferably, at least one sealing ring is provided to provide an effective seal between the outer periphery of the pipe insert and the inner wall of the guest pipe. As an alternative to the provision of sealing rings, a layer of adhesive may be provided between the outer periphery of the pipe insert and the inner wall of the guest pipe. Equally, the outer periphery of the pipe insert may be a close sliding and sealing fit against the inner wall of the guest pipe.

To provide an effective contact as between the pipe insert and the outer host pipe, the flange overlying the exposed edge of the inner host pipe can be extended to provide a final wall lying parallel to and spaced from the outer wall of the guest pipe, to provide a recess into which is fitted the end of the host pipe.

Thus, by having the pipe insert weld-compatible with the outer host pipe and by having the insert in sealing engagement with the inner wall of the inner guest pipe, the abutting ends of lengths of outer host pipes can be welded by a technique suited to the material, with the simultaneous welding of the then abutting outer faces of the adjacent pipe inserts.

Conventional plastics pipes that have notable advantages by being rustproof and able to resist mechanical and frost damage can serve ideally as the outer host pipe, and when the same plastics material can be used for the pipe insert. To suit the nature of, for example, fluids to be supplied, a guest pipe could be selected from any one of a number of relatively rigid materials of themselves difficult to connect, such as, for example, rigid plastics, glass, concrete, or ceramic materials. Such materials can also be selected when the elimination of ovality or control ol the polymer memory is a necessity but where ease of connection, resilience, and resistance to rusting or corrosion, are a requirement. Here again, the rigidity of the guest pipe would provide an improvement of circularity, and the plastics of the host pipe ensures that the other required attributes can be achieved and are present. The relatively simple act of introducing an insert into the guest pipe to overlap the end of the guest and host pipes enables the employmenl of conventional welding techniques for plastics pipes i.e., electroflision or butt-fusion to provide an effective joint as between the adjacent lengths of outer host pipes and simultaneously between the respective inserts in the adjacent pipe lengths.

Particularly when the connecting technique is by electroftision it is preferred to provide an inner flange central of the electrofusion sleeve not only to provide a centre against which each pipe length can abut, but also to provide additional plastics material at the junction between the exposed ends of the pipe inserts of the pipe lengths for the greater certainty of providing an effective weld as between the outer host pipes and the inserts.

One example of pipe and pipe joint in accordance with the invention is shown in the accompanying drawing which is a sectional side elevation of the adjacent ends of lengths of pipe fitted in an electrofusion sleeve prior to welding having taken place.

In the drawing, the ends of two host pipes 1, 2 of polyolefine are shown within which are respective guest pipes 3, 4. Close fitting inserts 5, 6 are inserted into a respective guest pipe 3, 4, the inserts being of the same material as that of the host pipes. To seal the inserts 5, 6 to the respective guest pipe 3, 4, elastomeric seals or bO' rings 7 are provided.

The outermost end of each insert 5, 6 is in the form of a flange 8 to overlie the exposed edge ofthe respective guest and host pipes, the flanges continuing in a respective annular wall 9 lying parallel to the insert and into which the respective host and guest pipes are fitted, the host pipe having a recess 10 to receive the annular wall and whereby the outer wall is in continuavion of the outer face of the host pipe.

The assemblies of host and guest pipes and inserts are inserted into each end oF an electrofusion sleeve 11 and into contact with a internal generally central annular flange 12, not only to centralise the assemblies within the sleeve 11, but also to provide additional plastics material at the position ofthejoint. With power supplied to the terminals 13 of the electrofusion sleeve 11, the heating coils 14, 15 cause the melting ofthe interface between the inner face oi the electrofusion sleeve and the outer face of the host pipe, there being the simultaneous melting of the flanges 8 and annular walls 9 of each insert and the simultaneously melting of the internal flange 12 to provide a most effective seal not only between the adjacent ends of the host pipes, but also between the adjacent inserts and between the inserts and the host pipes.

Claims

1. A pipe comprising an outer host pipe, an inner guest pipe, each of a material to provide a particular required attribute, and a pipe insert of a material weld-compatible with the material of the outer host pipe, the pipe insert being inserted in the end of the inner guest pipe and having an outermost flange to overlie the outer edge of the inner guest pipe.

2. A pipe as in Claim 1, wherein at least one sealing ring is provided to provide an effective seal between the outer periphery of the pipe insert and the inner wall of the guest pipe.

3. A pipe as in Claim 1 wherein an adhesive is provided between the outer periphery of the pipe insert and the inner wall of the guest pipe.

4. A pipe as in Claim 1 wherein the outer periphery of the pipe insert is a close sliding fil. on the innerwall of the guest pipe to provide sealing engagement therebetween.

5. A pipe as in any of Claims 1 to 4, wherein to provide an effective contact as between the pipe insert and the outer host pipe, the flange overlying the exposed edge of the inner host pipe is extended to provide a final wall lying parallel to and spaced from the outer wall of the guest pipe, to provide a recess into which is fitted the end of the host pipe.

6. A pipe as in any of Claims 1 to 5, wherein the outer host pipe is of conventional plastics material.

7. A pipe as in any of Claims 1 to 6, wherein the pipe insert is of the same material as the outer host pipe.

8. A pipe as in any of Claims 1 to 7, wherein the guest pipe is of a relatively rigid material.

9. A pipe as in Claim 8, wherein the relatively rigid material is selected from rigid plastics, glass, concrete, or ceramic materials.

10. A pipe as in any of Claims 1 to 9, wherein the pipe insert is an electrofusion coupling sleeve.

11. A pipe substantially as herein before described with reference to the accompanying drawing(s).