GB2310907A

GB2310907A - In situ repair of fluid carrying pipes

Info

Publication number: GB2310907A
Application number: GB9704382A
Authority: GB
Inventors: Trevor Stafford; Michael David Wild
Original assignee: MW Polymer Products Ltd; British Gas PLC
Current assignee: MW Polymer Products Ltd; British Gas PLC
Priority date: 1996-03-09
Filing date: 1997-03-03
Publication date: 1997-09-10
Anticipated expiration: 2017-03-03
Also published as: GB9704382D0; GB2310907B; GB9605061D0

Description

In Situ Repair of Fluid-Carrying Pipes The present invention concerns a method and apparatus for the repair of fluid-carrying pipes in situ, and relates in particular although not exclusively to the emergency repair of low pressure gas pipes.

Accidental damage to low pressure gas mains and pipes can be caused in various ways, for example by digging and excavation equipment. There is a need for effective means of making an emergency, so called "live repair" of the pipe in such circumstances. Typically, such repair systems provide an adequate temporary repair, but necessitate the making of a subsequent more permanent repair when the relevant area has been made safe.

The present invention seeks to provide an improved method and apparatus for in situ repair of pipes.

According to one aspect of this invention there is provided a method for repairing a damaged pipe carrying a fluid, comprising applying to the damaged area of the pipe a first repair means to prevent leakage of fluid from the pipe and thereafter applying a second repair means over the first repair means. The method is suitable for permanently sealing a damaged pipe carrying a fluid without stemming the flow or reducing the pressure of the fluid carried by the pipe. The second repair means has, in this embodiment, the effect that it increases the life of the repair.

The method may further include cleaning and/or otherwise preparing the immediate surroundings of the pipe after applying the first repair means and prior to applying the second repair means. In the preferred embodiments, the method has the advantage that the first repair means can be applied without total excavation of the pipe.

In a first embodiment, the first repair means preferably comprises an adhesive sealing pad to adhere to the pipe. Preferably the pad comprises a supporting element, an elastomeric material and an adhesive surface. The supporting element may be of woven matting, preferably a glass fibre matting.

The elastomeric material may comprise a polyurethane. The pad may be further secured to the pipe by secondary securing means, which are, preferably in the form of staples.

In the first embodiment the first repair means further includes a tape for wrapping around the pipe. The tape may comprise a natural or a synthetic rubber, such as a nitrile rubber, preferably selected or adapted to have resistance to substances liable to be found in the environment of the repair.

In a second embodiment, the first repair means comprises a tape for wrapping around the pipe and the method includes applying the tape directly to said damaged area of the pipe. The tape may comprise a natural or a synthetic rubber, such as a nitrile rubber, preferably selected or adapted to have resistance to substances liable to be found in the environment of the repair.

In this embodiment, the tape wrapping is applied to said damaged area under tension. This creates an equal and opposite force over the damaged area to seal the damaged area against leakage of fluid therefrom.

The second repair means preferably comprises an outer containment for said damaged area. There may also be provided a primer for application to the pipe outer surface prior to applying the containment.

The outer containment may comprise a resin filled sleeve or muff.

Alternatively, the outer containment may comprise a muffless encapsulation system, which preferably comprises a curable synthetic resin and a covering film. The curing reaction is in the preferred embodiments, exothermic. This exothermic reaction causes the tape material to shrink, thereby increasing the tension thereof and enhancing the sealing of the tape material against the leak.

According to another aspect of this invention there is provided apparatus for repairing a damaged pipe, comprising a first repair means to be applied to the damaged area of the pipe, and a second repair means to be applied over the first repair means.

In a first embodiment, the first repair means comprises an adhesive sealing pad to adhere to the pipe. Preferably, the pad comprises a supporting element, an elastomeric material and an adhesive surface. The supporting element may be a woven matting, preferably a glass fibre matting. The elastomeric material may comprise a polyurethane. Secondary securing means may be provided further to secure the pad to the pipe. The secondary securing means are preferably in the form of staples.

In the first embodiment, the first repair means further includes a tape for wrapping around the pipe over the sealing pad.

In a second embodiment, the first repair means comprises a tape for application directly around the damaged area of the pipe. The tape may comprise a natural or a synthetic rubber, such as a nitrile rubber, preferably selected or adapted to have resistance to the substances likely to be found in the environment of the repair.

The outer containment may comprise a resin filled sleeve or muff.

Alternatively, the outer containment may comprise a muffless, encapsulation system, which preferably comprises a curable synthetic resin and a covering film.

The invention will be further described for the purposes of illustration only with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic perspective view of a part of a damaged gas pipe; Fig. 2 is a diagrammatic perspective view of a sealing pad; Fig. 3 is a perspective view showing stapling of the sealing pad on the pipe; Fig. 4 is a sectional view on line X-X of Fig. 3; Fig. 5 is a perspective view showing application of tape to the repair; and Fig. 6 is a sectional view on line X-X of Fig. 5.

Fig. 7 is a diagrammatic perspective view of a hole in a pipe undergoing repair by another embodiment.

Fig. 8 is a sectional view on line X-X of Fig. 7.

Referring to Fig. 1, there is shown a damaged part of pipe 10 forming part of a low pressure gas supply system. The pipe 10 in the present example is formed from polyethylene, although the method and materials described herein may also be used for the repair of metallic or cementitious pipes. The damaged area of the pipe 10 includes a hole 12 through the wall of the pipe, which is approximately 40 mm in diameter. Surrounding the hole 12 is an area of scarring and pipe distortion 14 comprising areas in which the outer wall of the pipe 10 has been respectively raised and lowered with respect to its initial position. Damage of this type is typical of that caused by penetration of the pipe by a tooth of a digging or excavation apparatus.

It will be appreciated that the primary requirement is to stop leakage of gas through the hole 12 as soon as possible, and that any method of materials used for this purpose must be safe in live gas conditions.

In a first embodiment a primary seal is provided by the application of a self-adhesive sealing pad 15, an example of which is shown in Fig. 2. The pad 15 comprises a woven matting layer 16 formed from a glass fibre, embedded within an elastomeric polyurethane backing layer 18. One surface 19 of the pad 15 is an adhesive surface. The adhesive surface comprises a portion of the backing layer having a relatively high proportion of uncured plasticiser, in this case achieved by reducing the amount of isocyanate in the mixture. This surface layer is sticky and remains pliable i.e. does not cure further, thus enabling resealing to take place should the pipe move after application of the pad.

To prevent leakage of gas from the pipe 10, an appropriate size of sealing pad 15 is applied as soon as possible over the hole 12 and scar damage 14, with the adhesive layer 19 being applied directly to the polyethylene pipe 10. The material of the pad 15 can be easily cut to the required size. The adhesive surface permits a seal to be achieved regardless of dust or dirt on the surface of the pipe. However, the sealing pad is further secured in place against the outward pressure of gas within the pipe by the application of non-sparking staples 20, for example bronze staples, as shown in Figs. 3 and 4. The staples are applied by means of a stapling device 22 of any suitable kind and which is known in the art.

A secondary seal is next applied over the sealing pad 15, in the form of a binding of a nitrile rubber tape 24. A suitable tape is of thickness 0.1 mm or greater, and 50 mm wide. The nitrile material is of a type which shrinks on heating, for reasons which will be described hereinafter.

Once the escape of gas from the hole 12 has been reduced, any necessary excavation of the ground surrounding the relevant area of pipe may be carried out to enable or facilitate completion of the repair. The temporary repair formed by the pad can if necessary be left for some hours or days, until further work can conveniently be carried out. However, the present invention particularly seeks to provide a means by which the described repair can effectively be upgraded to a more permanent repair.

To complete the repair, the affected area of the pipe 10 is provided with an outer containment. In the case of a repair at an awkwardly-shaped site, there is preferably used a muffless encapsulation system, such as that known as POLYFORM manufactured by M W Polymer Products Limited. The system comprises a curable polymeric resin which is applied in a layer over the relevant area, together with a film which is applied over the resin coating. Alternatively, in the case of, for example, a straight pipe, then the containment may comprise a muff or sleeve which is used to seal and surround the damaged area, and is subsequently filled with a liquid polymeric or synthetic resin material together with a suitable curing agent. The sleeve may be formed from polythene and is attached to the pipe by straps. A suitable resin system comprises polyurethane with isocyanate as the curing agent.

The curing of the encapsulating resin is an exothermic process which causes a temperature rise to approximately 800C. This heats the nitrile tape, causing it to shrink and thereby increase pressure on the mastic pad, compressing it around the damaged area 14 of the pipe 10 as shown in Fig. 6.

This outer containment completes the repair and restores the strength of the pipe.

It is believed that a tape having the following characteristics would be suitable in the above described embodiment.

Preferred nominal hardness 60 IRHD Mechanical strength Tensile in accordance with BS 903: Part Al min 10 MN/m2 Elongation at break in accordance with BS 903: Part A26 min 350% Compression in accordance with BS 903: Part A6 max 8% at 23 deg C Compression in accordance with BS 903: Part A6 max 25% at -5 deg C Stress relaxation in accordance with BS 903: Part A6 max 6% at 23 deg C Tensile strength reduction max 10% Elongation reduction (maximum of original elongation) 30% Hardness change max 5 IRHD Liquid immersion in 70/30 iso-octane and toluene at 23 deg C for 7 days Permitted volume increase max 30% Hardness change max 15 IRHD Tensile strength min 5 MN/m2 Elongation min 175% A desorption will be carried out on specimens immersed in the above mixture for 7 days then dried in air at 70 deg C. The following values will be permitted Volume loss max 12% Hardness change There is thus described a method and materials which enable the making of an emergency, live gas repair, which repair can then be converted to a more permanent repair simply by further treatment. The method is appropriate for a wide range of pipe sizes, can be used in all weather conditions, requires no specialist skills, uses simple equipment and presents minimal health or safety risks.

In the second embodiment shown, in Figs. 7 and 8 the tape 24, which is the same as the tape 24 in Figs. 1 to 6, is wrapped around a hole 12 in a damaged pipe 10, without the use of a 15 as described above, i.e. the tape 24 is applied directly over the hole 12 and wrapped around the pipe 10, as shown in Figs. 7 and 8.

The tape 24 which has elastic properties is applied to, and wrapped around, the pipe 10 under tension, as shown by the arrows 10 in Fig. 8. The tension force T is balanced in the tape by an equal and opposite force across the hole 12 in the direction of the arrows F in Fig. 8. This force F is due to the elastic properties of the tape 24.

The force F thus provides a force having a component which is directed inwardly of the pipe which creates a seal against the leakage of gas in the pipe.

It is expected that using the nitrile tape described above is a long term seal can be achieved which could perhaps be in the region of fifty years.

After the tape has been applied the affected area of the pipe 10 can be provided with an outer containment. This can be in the form of the encapsulation system, or the muff or sleeve as described above, using the polymeric or synthetic resin material in the same manners as described above.

The curing of the resin is, as before, exothermic and this causes the tape to shrink, increasing its tension.

It will be appreciated that modifications may be made within the scope of the invention. The method is described particularly with reference to low pressure polyethylene gas pipes, but it will be appreciated that the method is also appropriate to metallic or cementitious gas pipes, or other fluid piping systems. The sealing pad may be constructed in a different manner and from different materials to those described, provided that it can provide short term adhesion to the material of the pipe surface, and resist an appropriate compressive load. The pad should also have an elastic consistency, resisting stress relaxation and shrinkage, and resist attack by diluents and solvents which may be found in the environment for which the repair is intended.

Preferably, the pad is such that it may be cut an appropriate size.

Alternative additional attachment means may be used other than staples.

The secondary seal may comprise an appropriate type of tape or bandage.

Other containment methods and systems may be used than those described.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method for repairing a damaged pipe carrying a fluid, comprising applying to the damaged area of the pipe a first repair means to prevent leakage of fluid from the pipe and thereafter applying a second repair means over the first repair means.

2. A method according to Claim 1 including cleaning and/or otherwise preparing the immediate surroundings of the damaged area of the pipe after applying the first repair means and prior to applying the second repair means.

3. A method according to Claim 1 or 2 wherein the first repair means comprises an adhesive sealing pad to adhere to the pipe, the pad comprising a supporting element, an elastomeric material and an adhesive surface.

4. A method according to Claim 3 wherein the supporting element comprises a woven matting, and the elastomeric material comprises a polyurethane.

5. A method according to Claim 3 or 4 wherein the pad is further secured to the pipe by secondary securing means.

6. A method according to Claim 5 wherein the secondary securing means are in the form of staples.

7. A method according to Claim 3,4,5 or 6 wherein the first repair means further includes a tape for wrapping around the pipe.

8. A method according to Claim 7 wherein the tape is in the form of a natural or a synthetic rubber, selected or adapted to have resistance to substances liable to be found in the environment of the repair.

9. A method according to Claim 1 or 2 wherein the first repair means comprises a tape for wrapping around the pipe and the method includes applying the tape directly to said damaged area of the pipe.

10. A method according to Claim 9 wherein the tape comprises a natural or a synthetic rubber, selected or adapted to have resistance to substances liable to be found in the environment of the repair.

11. A method according to any of Claims 7 to 10 wherein the tape comprises nitrile rubber.

12. A method according to Claims 9,10 or 11 wherein the tape wrapping is applied to said damaged area under tension.

13. A method according to any preceding Claim wherein the second repair means comprises an outer containment for said damaged area.

14. A method according to Claim 13 further including applying a primer to the pipe outer surface prior to applying the containment.

15. A method according to Claim 13 or 14 wherein the outer containment comprises a resin filled sleeve or muff.

16. A method according to Claim 13 or 14 wherein the outer containment comprises an encapsulation system, which comprises a curable synthetic resin and a covering film.

17. A method for repairing a damaged pipe carrying a fluid, comprising applying directly to the damaged area of the pipe repair means in the form of a tape, wherein the application of the tape is by wrapping the tape around the pipe.

18. A method according to Claim 17 wherein the tape comprises a natural or a synthetic rubber selected or adapted to have resistance to substances liable to be found in the environment of the repair.

19. A method according to Claim 17 or 18 wherein the tape wrapping is applied under tension.

20. A method according to any of Claims 17 to 19 comprising applying second repair means to the damaged area of the pipe.

21. A method according to Claim 20 wherein the second repair means comprises an outer containment for said damaged area.

22. A method according to Claim 20 or 21 further including applying a primer to the pipe outer surface prior to applying the outer containment.

23. A method according to Claim 20 or 21 wherein the outer containment comprises a encapsulation system, which comprises a curable synthetic resin and a covering film.

24. Apparatus for repairing a damaged pipe, comprising a first repair means to be applied to the damaged area of the pipe, and a second repair means to be applied over the first repair means.

25. Apparatus according to Claim 24 wherein the first repair means comprises an adhesive sealing pad to adhere to the pipe, the pad comprising a supporting element, an elastomeric material and an adhesive surface.

26. Apparatus according to Claim 25 wherein the supporting element is a woven matting, and the elastomeric material comprises a polyurethane.

27. Apparatus according to Claim 25 or 26 wherein secondary securing means are provided further to secure the pad to the pipe.

28. Apparatus according to Claim 27 wherein the secondary securing means are in the form of staples.

29. Apparatus according to any of Claims 24 to 28 wherein the first repair means further includes a tape for wrapping around the pipe over the sealing pad.

30. Apparatus according to Claim 24 wherein the first repair means comprises a tape for application directly around the damaged area of the pipe.

31. Apparatus according to Claim 29 or 30 wherein the tape comprises a natural or a synthetic rubber selected or adapted to have resistance to the substances likely to be found in the environment of the repair.

32. Apparatus according to Claim 29,30 or 31 wherein the tape comprises a nitrile rubber.

33. Apparatus according to any of Claims 24 to 32 wherein the second repair means comprises an outer containment for said damaged area.

34. Apparatus according to Claim 33 including a primer for application to the pipe outer surface prior to applying the containment.

35. Apparatus according to Claim 33 or 34 wherein the outer containment comprises a resin filled sleeve or muff.

36. Apparatus according to Claim 33 or 34 wherein the outer containment comprises an encapsulation system which comprises a curable synthetic resin and a covering film.

37. Apparatus for repairing a damaged pipe carrying a fluid, comprising pipe repair means in the form of a tape to be wrapped around the pipe.

38. Apparatus according to Claim 37 wherein the tape comprises a natural or synthetic rubber selected or adapted to have resistance to substances liable to be found in the environment of the repair.

39. Apparatus according to Claim 37 or 38 wherein the tape comprises a nitrile rubber.

40. Apparatus according to Claim 37,38 or 39 including second repair means to be applied to the damaged area of the pipe.

41. Apparatus according to Claim 40 wherein the second repair means comprises an outer containment for said damaged area.

42. Apparatus according to Claim 41 further including a primer to be applied to the pipe outer surface prior to applying the containment.

43. Apparatus according to Claim 40 or 41 wherein the outer containment comprises an encapsulation system, which comprises a curable synthetic resin and a covering film.

44. A method substantially as herein described with reference to the accompanying drawings.

45. Apparatus substantially as herein described with reference to the accompanying drawings.

46. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.