GB2153944A

GB2153944A - Pipe seal

Info

Publication number: GB2153944A
Application number: GB08502773A
Authority: GB
Inventors: John Robert George Clark; Peter Selwyn James
Original assignee: ALH Systems Ltd
Current assignee: ALH Systems Ltd
Priority date: 1984-02-10
Filing date: 1985-02-04
Publication date: 1985-08-29
Also published as: GB8502773D0; GB8403596D0; GB2153944B

Abstract

To increase the flexibility of an encapsulation of a pipe joint at least one discrete depression 8 is formed in its outer surface during its in situ moulding. The depression occupies a substantial portion of the volume of the mass. For this purpose the muff used as an encapsulation mould has at least one ridge on its inner surface. <IMAGE>

Description

SPECIFICATION Pipe seal The present invention relates to a method of sealing the join(s) between two or more pipes, and to a seal produced by such a method.

When two pipes are joined, the join must be made gas- and/or airtight as appropriate, to prevent leakage at the joint. When assembling a pipe-line it is relatively easy to provide a seal of e.g. cement, but if this seal has failed, it is harder to repair the join in situ. One way of achieving an in situ repair is to apply a seal to the outside of the pipes covering the join. Fig. 1 of the accompanying drawings shows one known way of forming such a seal. The pipes 1 and 2 to be joined are fitted one into the other and a flexible mould or "muff" 3 is fitted round the pipes adjacent their join. the muff 3 is secured to the pipes 1 and 2 by strapping 4. Then, a sealant material, such as a two-part polyurethane, is poured via a filling spout (not shown) into the muff 3 to fill the space 5 between the muff 3 and the pipes 1 and 2.It is desirable that the sealant is put under a slight overpressure to ensure that it forms a good seal. The two-part polyurethane solidifies within the muff, thereby sealing the join between the pipes. Once the sealant has solidified, the muff 3 is removed and the seal is completed.

There is, however, a problem with such a seal. Relative movement of the pipes, particularly bending strains at the join, place considerable stress on the seal and it may happen that the sealant material becomes detached from one or other of the pipes, thereby destroying the seal.

The present invention seeks to overcome this problem. It consists of forming a seal which is more flexible than a standard seal, because it has a depression in it. This depression is formed by a projection on the inside of the muff.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a known means for forming a pipe seal, and has already been described; Figure 2 shows a means for forming a pipe seal according to the present invention; and Figure 3 shows a pipe seal formed by the present invention.

Referring to Fig. 2, the method of forming a pipe seal according to the present invention is generally similar to that of the prior art. A flexible mould or muff 3 is placed over two pipes 1 and 2 and secured to the pipes by strapping 4. A rigid muff may be used but this is more difficult to fit to the pipes. In the present invention, however, the muff 3 has a filling strip 6 on its inner surface. The filling strip may be an extruded polyethylene strip attached to the inner surface of the muff by adhesive, stapling or sewing or, as shown, may be formed integrally with the muff itself.

It is desirable that the filling strip 6 has a nonstick skin to permit it to be removed easily from the seal, once formed.

Then the space 5 within the muff 3 is filled with sealant material used in the prior art method. The slight over-pressure within the space 5 ensures that the muff 3 and hence the filling strip 6 is forced away from the pipes 1 and 2 so that there is a sealant layer between the filling strip 6 and the pipes 1 and 2. In this example the strip 6 occupies about 30% of the volume between the muff and the pipes and extends about 1/2 of the distance from the muff to the pipe.

Once the sealant material has solidified, the muff 3, together with its filling strip 6 is removed from the pipes 1 and 2 and the resultant seal 7 is shown in Fig. 3. It consists of a ring of sealant material around the pipes, at their join, the ring having a generally triangular cross-section but with a distinct, discrete depression or cut-out 8, which was formed by the strip 6, in its outer surface.

This cut-out 8, which is annular, increases the flexibility of the seal 7 so that the seal 7 may more readily accommodate bending movements between the pipes.

Although described in connection with sealing of pipes which fit one within the other, the present invention is also applicable to e.g.

the sealing of pipes attached to each other by a flange.

The strip may be of any suitable cross section as well as the generally semi-circular one shown. It and correspondingly the depression formed by it-may occupy any desired percentage of the designed volume within the muff. The aim, to increase flexibility in the joint in view of the nature of the material used, is achieved by making the depression substantial, indeed as large as is possible without significant loss of strength. Examples of the percentage of volume occupied are 25 to 75% or more preferably 30 to 50%. That is to say, the depression may have a volume which is 1:3 to 3:1, more preferably 3:7 (say 1:2) to 1:1%, as a ratio to the volume of the mass in the finished joint. The strip may project from the muff towards the pipe by e.g.

10% to 60% of the distance between the two at the relevant position, more preferably between 25 and 40%, when the muff is positioned for use.

Claims

1. An encapsulated pipe joint comprising an encapsulating mass moulded in situ over a leak path of the joint and having an inner surface contacting the pipes and an outer surface having at least one discrete depression moulded therein whereby to increase the toler ance of the mass to bending of the joint.

2. An encapsulated pipe joint as claimed in claim 1 wherein at least one depression has a volume which is between 1:2 and 1:1 as a ratio to the volume of the mass.

3. An encapsulated pipe joint as claimed in claim 2 wherein the at least one depression extends for between 25 and 40% of the thickness of the mass to the outer surface thereof.

4. An encapsulated pipe joint comprising two pipes with a leak path between them, an encapsulating mass of elastomeric material moulded in situ to contact an outer surface of both said pipes and extend across the said leak path, said mass having an outer surface spaced by a thickness of the mass from the outer surface of the pipes, said mass demon strating greater flexibility than an unmodified mass by virtue of the modification of the said outer surface by the formation therein of at least one distinct discrete depression during the said in situ moulding of the mass.

5. A method of moulding an encapsulated pipe joint as claimed in claim 4 wherein a moulding muff is secured across the pipe joint to enclose a volume between itself and the surfaces of the pipes, the said muff having on its inner surface at least one distinct discrete ridge projecting towards the pipe surface but spaced therefrom, an elastomeric material is introduced into the said volume to form the encapsulating mass, and the muff is removed to leave the encapsulating mass in situ with the said at least one depression on its outer surface.

6. A method according to claim 5 wherein the muff has a strip attached to it to form the said ridge.