GB2172370A - Lining pipelines - Google Patents

Abstract

A member for lining the internal wall of a pipeline 12 comprises a flexible strip 1 of, for example polyethylene, which is adapted to be folded lengthways to form a tube 10 with a surface overlap. The strip 1 has on one surface a tooth 4 which engages with an aperture 6 on the other surface 9 when the overlap is formed so that the tube wall can be closed after the tube 10 has been inserted into the pipeline 12 to be lined. <IMAGE>

Description

SPECIFICATION Lining the internal wall of a pipeline The present invention relates to lining the internal wall of a pipeline particularly though not exclusively a pipeline which transports a fluid such as gas, oil, water or sewage in order to seal any existing or potential leaks in the wall of the pipeline.

Fluid transporting pipelines such as cast iron gas mains are prone to develop leaks at joints and in the pipeline wall itself at any cracks and fissures caused by mechanical damage and corrosion.

A number of techniques exist for arresting or preventing such leaks. One such technique involves sealing the leak with a sealant injected into the site of the leak. Where the pipeline is accessible, i.e. above ground, such leaks are relatively easy to seal by direct external injection of the sealant into the joint or leaking part. However, where the pipeline is buried as is the case with most gas mains, the leak must either be sealed by injecting the sealant from a point within the bore of the main (so called "internal sealing") after gaining access to a convenient end of the pipeline or access must be gained to the outer wall of the main by excavation so that the sealant can be injected externally (so called "external sealing").

Internal sealing can be a slow and time-consuming procedure owing to the need to accurately identify the site of the or each leak before it is sealed. In addition costly equipment is necessary to carry out the repair properly using this technique and the technique is really only justified on cost grounds where there are several leaks to be sealed at one time in a length of main.

External sealing can also be time consuming and expensive due to the need to accurately identify the site of the or each leak and then to excavate, possibly at several places, to gain access to the site of the leak or teaks.

Another technique for stopping or at least obviating such leaks is simply to replace the offending leaking main or a main which is in danger of leaking with a new main by a procedure which involves inserting the new main into one end of the old main and pushing, or at any rate moving, the new main into the leaking main until it is completely occupied by the new main. The new main is then connected to the adjoining sections of the old main and takes over from the leaking main which is, in effect, redundant.

Invariably the old main is broken out and removed.

While this technique involves considerably less preparatory work than the leak sealing techniques described above it has a number of drawbacks. By necessity, in order to effect insertion, the external diameter of the replacement main is required to be somewhat smaller than the internal diameter of the leaking main. Furthermore since the replacement main is to operate as a fluid transporting main in its own right it must be strong enough to resist stress from ground movement and this factor imposes a requirement that the wall thickness of the main be substantial particularly where the main is of a synthetic resin material such as polyethylene. Consequently as a result of these requirements the internal diameter of the replacement main will be considerably smaller than the internal diameter of the leaking main.

In the case where the leaking main is transporting gas at a pressure at or near to the maximum allowable for the dimensions of the main, this reduction in main bore diameter may either lead to an undesirable reduction in gas flow rate or alternatively any reduction in gas flow rate may be so unacceptable that replacement by this technique cannot be considered.

It is therefore an object of the present invention to provide means for effecting a seal of any existing or potential leaks in the wall of a pipeline without the disadvantages of the techniques described above.

According therefore to one aspect of the present invention we provide a member for lining the internal wall of a pipeline, the member comprising a flexible elongate strip adapted to be folded lengthways to form a tube with a surface overlap for insertion into the pipeline through an open end thereof, the strip surfaces which are to engage at the overlap being adapted to adhere or be fastened together so that the wall of the tube can be closed once the strip in inside the pipe.

According to another aspect of the present invention we provide a method for lining the internal wall of a pipeline, the method comprising folding a flexible elongate strip lengthways to form a tube with a surface overlap, inserting the tube so formed through an open end of the pipeline, moving the tube along the pipeline until the tube occupies the desired length of the pipeline and allowing or causing the surfaces of the strip in the overlap to adhere or be fastened together to close the wall of the tube.

The tubular lining so formed by the member inside the pipeline provides an effective seal of any actual or potential leaks at pipeline joints or at cracks or other fissures in the wall of the pipeline. The member can be arranged so that it is a very close fit with the internal wall of the pipeline and the thickness of the tube so formed can be very much less than that of a replacement main of polyethylene or similar type material since the tube is merely serving as a lining for the internal wall of the pipeline and not as a replacement main.

As a consequence the reduction in the internal bore diameter of the pipeline due to the presence of the lining can be minimal so that there is very little reduction in the rate of fluid flow through the pipeline. In addition the technique obviates the need to break out the old main as is required in the main replacement technique previously described.

In one embodiment of the invention the strip surfaces which are to engage at the overlap have elements which are adapted to be fastened together to close the wall of the tube.

These elements may comprise respectively, a male portion which is formed on one surface of the strip and a female portion which is formed on the other surface of the strip and to which the male portion may be fastened. In this case the elements may be integral with the strip and preferably they form continuous bands along the length of the strip.

The strip surfaces which are to engage at the overlap may be formed on strip portions whose thickness tapers towards adjacent strip edges. With this arrangement the tube wall thickness at the overlap can be held at the same value as the thickness of the remainder of the tube wall.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure l is an end view of a typical member in accordance with the present invention, Figure 2 is a perspective view of the member from above one end, the member being shown in the process of being folded into a tube, Figure 3 is a view from one end showing the member folded into the form of a partially coiled tube before insertion into a length of pipeline such as a gas main, Figure 4 is a view from one end showing the member in position after insertion into the main but before the tube wall is closed and, Figure 5 is a view from one end showing the main lined with the member now in the form of a closed tube.

Referring to the drawings, the member comprises an elongate strip 1 of a flexible material which may be any suitable synthetic resin material such as polyethylene, the strip being formed by extrusion.

A tapering portion 2 of the strip 1 ajdacentto the left hand edge 3 as seen in Figures 1 and 2 is formed with a tooth 4 on the lowermost surface 5 which in fact forms the taper. This tooth 4 is arranged to form a snap4ittype engagement with a corresponding aperture 6formed in another tapering portion 7 of the strip 1, this portion 7 being located adjacent to the right hand edge 8 of the strip 1 as seen in Figures 1 and 2. The aperture 6 is located in the strip uppermost surface 9 which forms the tapered portion 7. The tooth 4 and the aperture 6 extend as continuous elongate bands along the entire length of the strip 1.

In use of the member, the strip 1 is first of all folded lengthways into the form of a partially coiled tube 10 with a surface overlap as shown in Figure 3, the surfaces including the tooth 4 and the aperture 6 being opposite each other. Initially the tube 10 so formed should have a diameter less than that which it will eventually have when it has formed the closed wall tube 11 shown in Figure 5 so that the tube 10 can be inserted into the main 12. The strip 1 may be coiled around a tubular mandrel (not shown) of suitable diameter to form the initial tubular structure 10 shown in Figure 3.

Initial steps (involving any necessary excavation) will have already been taken to expose a convenient open end of the main 12 into which the tube 10 is to be inserted.

The mandrel and the coiled strip 1 are then moved together into the main 12 untilthestrip 1 occupies the desired length of main 12 to be lined. The strip 1 is then allowed to uncoil to the position shown in Figure 4 and finally it is manipulated so that the tooth 4 engages as a snap-fit in the aperture 6to form a lining comprising the closed wall tube 11 shown in Figure 5. Because of the tapering thickness of the engaging portions 2 and 7 the tube II so formed has a constant wall thickness.

It wili be appreciated thatthe strip 1 can be dimensioned and the tooth 4 and aperture 6 can be so positioned on the strip 1 relative to each other that the tubular lining II so formed is a very close fit with the internal wall of the main 12.

After the lining II has been formed the mandrel is withdrawn, the open end of the main 12 is reconnected to its respective adjacent main and the hole formed by the excavation is filled in.

Claims (15)

1. A member for lining the internal wall of a pipeline, the member comprising a flexible elongate strip adapted to be folded lengthways to form a tube with a surface overlap for insertion into the pipeline through an open end thereof, the strip surfaces which are to engage at the overlap being adapted to adhere or be fastened together so that the wall of the tube can be closed once the strip is inside the pipe.

2. A member as claimed in claim 1 in which the strip surfaces which are to engage at the overlap have elements which are adapted to be fastened together to close the wall of the tube.

3. A member as claimed in claim 2 in which the elements comprise respectively, a male portion which is formed on one surface of the strip and a female portion which is formed on the other surface of the strip and to which the male portion may be fastened.

4. A member as claimed in claim 2 or claim 3 in which the elements are integral with the strip.

5. A member as claimed in any of claims 2 to 4 in which the elements form continuous bands along the length of the strip.

6. A member as claimed in any of claims 1 to Sin which the strip surfaces which are to engage at the overlap are formed on strip portions whose thickness tapers towards adjacent strip edges.

7. A member substantially as hereinbefore described with reference to the accompanying drawings.

8. A method for lining the internal wall of a pipeline, the method comprising folding a flexible elongate strip lengthways to form a tube with a surface overlap, inserting the tube so formed through an open end of the pipeline, moving the tube along the pipe or pipeline until the tube occupies the desired length of the pipeline and allowing or causing the surfaces of the strip in the overlap to adhere or be fastened together to close the wall of the tube.

9. A method as claimed in claim 8 in which the strip surfaces engaging at the overlap are fastened together by means of elements with which the surfaces are provided.

10. A method as claimed in claim 9 in which the elements comprise a male portion which is formed on one surface of the strip and a female portion which is formed on the other surface of the strip and to which the male portion is fastened.

11. A method as claimed in claim 9 or claim 10 in which the elements are integral with the strip.

12. A method as claimed in any of claims 9 to 11 in which the elements form continuous bands along the length of the strip.

13. A method as claimed in any of claims 8 to 12 in which the strip surfaces engaging at the overlap are formed on strip portions whose thickness tapers towards adjacent strip edges.

14. A method substantially as hereinbefore described with reference to the accompanying drawings.

15. A pipeline lined with the member claimed in any of claims 1 to 7.