GB2093146A - Improvements in sealing a leak in a pipe or pipeline carrying fluid under pressure - Google Patents

Abstract

A leak in a pipe or pipeline carrying a fluid, such as natural gas, under pressure is sealed by securing a vent pipe 3 to a pipe at the point where fluid is leaking and a sleeve 13, formed in a first wrapping of a flexible sheet material forms a sheath for the pipe 3. The sleeve 13 is sealed to the pipe 3 by means of a clip 25 after and wrapping 1 is circumferentially wrapped around to form an inner enclosure into which leaked gas issues. A sleeve 14, formed in a second wrapping 2 of flexible sheet material, also sheaths the pipe 3 and is sealed thereto by a clip 26 after which the wrapping 2 is circumferentially wrapped around the main 34 to overlap the wrapping 1 and form an outer enclosure therewith, and a cold curing resin is introduced into the outer enclosure through a further sleeve or funnel 15 in the outer wrapping 2 and the resin is allowed to harden, after which extension pipe and flame trap are removed and the vent pipe 3 is sealed with a plug 21. <IMAGE>

Description

SPECIFICATION Improvements in sealing a leak in a pipe or pipe-line carrying fluid under pressure The present invention relates to an improved method for sealing a leak in a pipe or pipeline carrying a fluid, particularly a combustible gas such as natural gas, under pressure.

One well known method of repairing or sealing a leak in a pipe or pipeline carrying fluid, such as a combustible gas under pressure, is the so called "Encapress" system. In this system, a metal muff, of say steel, is secured around that area of the pipe from which fluid is leaking so as to form an annular enclosure for the leak. A sealant material.

such as a hardenable fluid resin, is then introduced through an orifice into the muff enclosure and is allbwed to harden to seal the leak.

There are however a number of disadvantages with this system. Firstly, metal muffs are costly and may require to be individually tailored to the job with consequent time penalties. Secondly, it is difficult to ensure that the muff forms a leak tight seal with the pipe or pipeline and therefore failures can occur. Thirdly, the sealant requires to be pumped or forced under high pressure into the muff. Fourthly, the muff is difficult to fit in confined spaces, requires a large amount of ground adjacent to the leak to be excavated and cannot be fitted if other services, such as water mains and electricity cables, run close to the leak to be worked on.

UK Patent Specification No. 1546073 describes another method and means for repairing or sealing a leak in a pipe or pipeline carrying fluid such as a combustible gas under pressure. This method involves wrapping around the pipe or pipeline a flexible wrapping of a plastics film and an integral vent member having a vent passage.

The wrapping initially has three compartments or envelopes which are separated from each other by removable clips and the largest compartment contains a resin absorbent material, such as fibrous felt, and houses the vent member. A second compartment adjacent to the largest compartment contains a resin and a third compartment adjacent to the second compartment contains a hardener for the resin.

Before the wrapping is applied to the pipe or pipeline the clips separating the second and third compartments are removed to allow the hardener and the resin to be mixed intimately. Next the clips separating the second and largest compartments are removed and the resin/hardener mixture is allowed to enter the largest compartment and the wrapping is manipulated to cause the mixture to become fully absorbed by the felt absorbent.

The outer layers of the wrapping are then slit to expose the resin absorbed felt and this is then wrapped around the pipe or pipeline. A further layer of plastics film may then be applied to the pipe line, and before the resin has cured so that the plastics film bonds to the resin. The vent pipe is sealed with a plug after the resin has cured.

While this method is cheaper and more versatile than the Encapress system, it has the disadvantage that as the wrapping contains felt, resin and hardener it is relatively heavy and the operator frequently finds it difficult and arduous to manipulate the wrapping to an extent sufficient to ensure a thorough mix of the resin and hardener and thorough absorption of the mix into the felt. In addition, when the resin-absorbed felt is removed from the wrapper it is tacky and unpleasant to handle apart from exuding a rather unpleasant organic odour.

In order to overcome the above disadvantages, the wrapping can be applied to the pipe or pipeline before the resin and hardener are mixed and absorbed into the felt. However, there is then great difficulty in ensuring a thorough mix of the resin and hardener and even greater difficulties in ensuring that the mix is absorbed into the felt since it is difficult to manipulate the wrapping once in situ on the pipe or pipeline. There is also a danger that the manipulation of the wrapping in situ will cause the fluid to leak from the wrapping after the resin has cured. It is therefore an object of the present invention to -seek to overcome the above disadvantages of the known leak repair systems.

According therefore to one aspect of the present invention, there is provided a method for sealing a leak in a pipe or pipeline, the method comprising forming with flexible material wrapped circumferentially around the pipe or pipeline an inner enclosure into which fluid leaked from the pipe or pipeline issues and an outer enclosure overlapping the inner enclosure, venting to atmosphere fluid leaked into the inner enclosure -without allowing the fluid to enter the outer enclosure, introducing into the outer enclosure a hardenable fluid encapsulant material from a source external of the enclosures, allowing or causing the encapsulant material to harden and sealing off the vent.

Preferably the leaked fluid is vented by way of but without entering the outer enclosure.

Suitably the enclosures are formed by sequentially wrapping around the pipe or pipeline two distinct wrappings of flexible material.

Conveniently the fluid is vented to atmosphere by way of a vent duct extending through orifices in the wrappings the duct being sealingly engaged with the orifices in the wrappings.

Preferably the duct is attached to the outer wall of the pipe or pipeline.

Suitably the orifices are formed by flexible sleeves with which the wrappings are provided and which receive and are sealingly engaged with the duct.

Conveniently the sleeve of at least the outer wrapping is releasably engaged with the duct.

Preferably sufficient encapsulant material is introduced into the outer enclosure to cause the outer wrapping to become taut.

Suitably after the duct has been sealed, the sleeve of the outer wrapping is released from the duct and further encapsulant material is introduced into the sleeve to enclose the duct and the material is allowed or caused to harden.

Conveniently the outer layer has an orifice for the introduction of the encapsulant material, the orifice being formed by a flexible funnel.

Preferably where the fluid is inflammable, and before the duct is sealed, the duct is fitted with a flame trap which is removed before the duct is sealed.

Suitably the flexible material is non-resin absorbent.

Conveniently the material is woven nylon having a plastics coating.

Preferably the coating is polyethylene.

Suitably the encapsulant material is a resin.

Conveniently the resin is a cold curing resin.

According to another aspect of the present inve-ntion, there is provided an assembly for sealing a leak in a pipe or pipeline carrying fluid under pressure according to the method defined above, the assembly including two wrappings of a flexible material for wrapping circumferentially around the pipe or pipeline so as to form an inner enclosure into which fluid leaked from the pipe or pipeline issues and an outer enclosure overlapping the inner enclosure, a vent duct for attachment to the pipe or pipeline and for sealing engagement with orifices in the wrappings through which, in use, the duct extends to enable fluid leaked into the inner enclosure to be vented to atmosphere only by way of the duct, means for sealingly engaging the duct with the orifices in the wrappings, an inlet in the wrapping which is to form the outer enclosure for the introduction into the outer enclosure of a hardenable fluid encapsulant material and means for sealing the duct after the encapsulant material has been allowed or caused to harden.

Preferably the means for sealing the duct with the orifices includes flexible sleeves with which the wrappings are provided and which form the orifices and are adapted to receive the duct.

Suitably the inlet in the wrapping which is to form the outer enclosure is in the form of a flexible funnel.

Conveniently the means for sealing the duct is a plug.

Preferably a removable flame trap is provided for fitting to the duct during the period when fluid is issuing from the duct.

Suitably the flexible material is non-resin absorbent.

Conveniently the material is woven nylon having a plastics coating.

Preferably the coating is polyethylene.

An embodiment of the invention will now be particularly described with reference to the accompanying drawings in which:~ Figure 1 is a perspective view of the component parts in the pipe or pipeline leak repair assembly or kit, Figure 2 is a side view of a pipe joint from which fluid is leaking and of the vent duct attached in position on the pipe, Figure 3 is a side view of the joint now enclosed by a circumferential inner wrapping of a flexible material, Figure 4 is a side view of the joint showing an outer circumferential wrapping of a flexible material overlapping the inner wrapping, the vent duct now being fitted with an extension pipe and flame trap, Figure 5 is a side view of the wrapping shown in Figure 4 after the outer enclosure formed by the outer wrapping has been filled with a hardenable fluid encapsulant material which has been allowed to harden and the vent duct has been sealed after removal of the extension pipe and flame trap and, Figure 6 is a side view of the outer wrapping with the duct sleeve being filled with further encapsulant material so that the duct is enclosed by the encapsulant.

Referring to Figure 1 the basic items of the assembly are a first or inner wrapping 1 of flexible material adapted to be wrapped circumferentially around that area of the pipe which is leaking so as to form an inner enclosure, a second or outer wrapping 2 of flexible material adapted to be wrapped circumferentially around and overlap the first wrapping 1 and form an outer enclosure and a vent duct 3 for attachment to the pipe to enable fluid leaked into the inner enclosure formed by the first wrapping to be vented to atmosphere.

Each of the wrappings 1 and 2 is a sheet of woven nylon coated on both sides with a polyethylene film. The outer wrapping 2 is wider than the inner wrapping 1 so as to be capable of overlapping the wrapping 1 when the wrappings 1 and 2 are in position on the pipe.

Each of the wrappings 1 and 2 comprises a sheet which is provided along its two lengthwise edges with open-ended pockets 4. The pockets 4 are formed from folded-back edges 5 of the wrappings 1 and 2 and, in use, each receive one of the four belts 6 which enable the wrappings to be secured circumferentially around the pipe. Each wrapping 1 and 2 is also provided with two strips 7 of foam plastics extending along the edges of the wrappings 1 and 2 parallel to the pockets 4.

These strips 7 enable the wrappings 1 and 2 to form a fluid-tight seal with the outer surface of the pipe when the wrappings 1 and 2 are wrapped around the pipe and the belts 6 are tightened to secure the wrappings 1 and 2 in position on the pipe.

One end 8 of each wrapping 1 and 2 is provided with a zip 9 and a zip track 10 which cooperates with a mating zip track 11 on the other end 12 of the wrappings 1 and 2 to enable these ends to be zipped together after the wrapping has been applied to the pipe.

Wrapping 1 is provided with an orifice (not shown) formed by a sleeve or funnel 1 3 of the same material as the wrapping 1 and stitched thereto. Wrapping 2 is provided with two orifices (not shown) formed by two sleeves or funnels 1 4 and 15 of the same material as the wrapping 2 and stitched thereto. The length of the sleeves 14 and 1 5 in wrapping 2 is considerably greater than that of the sleeve 13 of wrapping 1.

The vent duct 3 comprises a steel pipe 16 welded at a lower end 17 to an arcuate steel bracket 1 8 whose curvature is similar to that of the fluid-carrying pipe in the area in which the vent pipe 16 is to be fitted. The vent pipe 16 is provided with an upper end 19 which is externally threaded to receive an internally threaded socket 20 which is screwed onto the pipe 16. A cylindrical steel plug 21 is suitably threaded to screw into the socket 20 so as to seal the pipe.

The lower end 1 7 of the pipe 1 6 is provided with a V-shaped notch 22 which forms with the bracket 18 an aperture through which fluid leaked from the pipe carrying the fluid under pressure can pass into the vent pipe 16 and be vented to atmosphere as will be described subsequently. The bracket 18 is provided with a pair of slots 19 adjacent either of its ends 20, each slot 19 extending some distance inwardly from one edge 21 of the bracket 18. These slots 19 accommodate, as shown, a flexible steel strap 22 which is used to secure the vent pipe 16 to the fluid carrying pipe in the vicinity of the leak as will be described subsequently.

Each of the belts 6 is either steel, woven fabric or plastics and is provided with a number of catches 23 which receive the free end 24 of each belt 6 and maintain the belt 6 tightened in position around the fluid carrying pipe. These belts 6 are each threaded through one of the pockets 4 via their free ends 24 after the wrappings 1 and 2 have been wrapped around the pipe and their ends zipped together.

A pair of hose clips 25 and 26 is also provided with the assembly. Clip 25 is used to sealingly engage the sleeve 13 of wrapping 1 with the wall of the vent pipe 16 and clip 26 is used to sealingly engage the sleeve 14 in wrapping 2 with the wall of the vent pipe 16 when sleeves 13 and 14 are suitably located around the vent pipe 16. Sleeves 14 and 1 5 are provided with a strip of foamed plastic formed as a ring 27 on the sleeves and these enhance the seal between the sleeve and the vent pipe 16 when the clip 26 is tightened on the ring 27. It is not essential however that the clip 26 be applied to the ring 27 for an adequate seal between the sleeve and the vent pipe 16 to be obtained.

Finally the assembly includes two pairs of rods 28 (only one pair shown in Figure 1), each pair of rods 28 being used to roll up each of the sleeves 14 and 1 5, after the enclosure formed by the second wrapping 2 has been filled with encapsulant material, so as to cause any excess encapsulant material remaining in the sleeves to be squeezed into the enclosure. Each rod 28 comprises two portions 29 and 30 which are bent at right angles to each other and each rod 28 has one portion 30 provided with an eye 31 through which, in use, the free end 32 of the portion 29 of the other rod 28 is inserted.

First, however, the mouth of sleeve 14 or sleeve 1 5 is folded flat and the free end 32 of one rod 28 is inserted into the eye 31 of the adjacent rod 28 while the free end 32 of this latter rod 28 is similarly inserted into the eye 31 of the first rod 28 so as to form a loop into which the flattened mouth of the sleeve can be inserted. Manual rotation of the loop about its diameter will thereby cause the sleeve to be rolled up.

In use of the assembly to seal a leak in a pipe carrying fluid such as a gas main, the area of the main, the vent pipe 16, socket 20 and plug 21 over which the wrappings are to be applied are all first grit blasted so as to clean them. Thus referring to Figure 2, the joint 33 which has a leak and an area of the main 34 on either side of the joint 33 are grit blasted as well as the vent pipe 16, socket 20 and plug 21. The vent pipe 16 is then attached to the main 34 as shown with the vent aperture 35 formed between the lower end of the vent pipe 16 and the bracket 18 as close as possible to a point at which fluid is leaking from the main 34. To attach the vent pipe 16 to the main 34, the strap 22 shown in Figure 1 is removed from the bracket 18 and the bracket 18 is then positioned on the main 34 as shown in Figure 2.The strap 22 is then bent around the main 34 and its ends are inserted into the slots 19 in the bracket 1 8 so that the vent pipe 1 6 is held securely in position on the main 34. The plug 21 on the vent pipe 16 is then removed.

Next, the sleeve 13 of the first wrapping 1 is fitted over the vent pipe 16 as shown in Figure 3 and the wrapping 1 is wrapped circumferentially around the joint 33 and the ends of the wrapping 1 are then zipped together. The ends of two belts are then inserted into the pockets 4 of the wrapping 1 and are then inserted into the catches 23, following which the belts 6 are tightened so as to form gas tight seals with the main 34 on either side of the joint 33. The hose clip 25 is then tightened around the sleeve 13 so that the sleeve 13 forms a gas tight seal with the vent pipe 16 and the wrapping 1 thus forms a first or inner enclosure into which gas leaked from the joint issues and leaves the enclosure only by way of the aperture 35 in the vent pipe 16.

Next the sleeve 14 of the second wrapping is fitted over the vent pipe 16 as shown in Figure 4 and the wrapping 2 is wrapped circumferentially around the first wrapping 1 so that this wrapping is completely enclosed by the second wrapping 2 and the ends of the wrapping 2 are then zipped together.

The ends of the two remaining belts are inserted into the pockets of the wrapping 2, are then inserted into the catches 23 and the belts 6 are tightened so as to form gas tight seals with the main 34 on either side of the edges of the first wrapping 1. Sleeve 14 which is of identical length to sleeve 15 is of a length considerably greater than the length of the vent pipe 16 projecting from the first enclosure and would, if allowed, completely envelope the upper end of the vent pipe 16. It is therefore rolled down as shown in Figure 4 so that the upper end of the vent pipe 16 projects freely outwardly from the sleeve 14. The hose clip 26 is tightened around the rolled down portion of the sleeve 14 so that the sleeve 14 forms a gas tight seal with the vent pipe 16.The second wrapping 2 thus now forms around the first wrapping 1 a second or outer enclosure and gas leaked from the joint into the inner enclosure is vented to atmosphere solely by way of the vent pipe 16 and without entering the outer enclosure.

As a safety precaution, if the gas is combustible, an extension pipe 36 with an externally threaded end is screwed into the socket 20 on the vent pipe 16 and a funnel shaped flame trap 37 having an internally threaded lower collar 38 is screwed onto the upper end of the extension pipe 36 which is externally threaded for this purpose.

While not shown in the figures, for added safety the extension pipe 36 is preferably of sufficient length so that any gas issuing from the vent pipe 16 can be discharged to atmosphere via the flame trap 37 at a position well away from the point where the operator is working. The extension pipe 36 can therefore be several feet in length if so required.

In the next stage, a hardenable fluid encapsulant material is poured into the outer enclosure formed by the second wrapping 2 using the free sleeve 15 as a funnel in a manner similar to that illustrated schematically in Figure 6 for sleeve 14. The encapsulant material is a cold curing resin in fluid form and incorporating a hardener and may be held in a suitable receptacle such as the can 39 shown in Figure 6. Pouring is continued until it appears that the enclosure formed by the outer wrapping 2 is full or at least until no more can be introduced into the enclosure and excess resin is present in the sleeve 15. The rods 28 shown in Figure 1 are then assembled into the loop as previously described and shown at 40 in Figure 6.The sleeve 15 is then folded flat and inserted into the loop 40 which is then rotated about its diameter to cause the sleeve 1 5 to roll up the loop in the manner shown in Figures 5 and 6 so as to squeeze the excess resin in the sleeve 15 into the enclosure formed by the wrapping 2.

The enclosure should now be completely full with resin and, if it is, the wrapping 2 should appear to be bulging with resin and become taut as shown in Figure 5 which also shows the sleeve 15 after it has been rolled up on the loop 40.

The resin is then allowed to harden and after the operator is satisfied that this has in fact occurred, the extension pipe 36 with the associated flame trap 37 is unscrewed from the socket 20 and the plug 21 is then screwed into the socket 20 to seal off the vent pipe 3 from atmosphere as shown in Figure 5. Next the hose clip 26 is removed from the sleeve 14 and this is extended to form a funnel which encloses the upper end of the vent pipe 3 as shown schematically in Figure 6. Further resin is then poured into the sleeve 14 until the vent pipe 3 and its plug 21 are completely encapsulated by the resin. Sleeve 14 is folded flat and inserted into the loop 40 of the other pair of rods 28 as shown in Figure 6.The sleeve 14 is then rolled up by the loop 40 in a manner similar to that previously described to squeeze the resin into the enclosure, the resin then being left to harden so as to complete the sealing of the leak.

The present invention displays advantages over the conventional metal muff system for repairing leaks in fluid carrying pipes chiefly because the wrappings in the present system are light and flexible. This enables the present system to be used in the repair of pipes having a wide variety of diameters, irregular cross-sectional shapes and incorporating special fittings. In contrast however each metal muff may have to be individually tailored to the pipe to be repaired. In addition, the flexibility of the wrappings enables them to achieve a much better leak tight seal with the pipe than is possible with the metal muff system.

Furthermore, the flexibility of the wrappings in the present system enables them to be used in confined situations where access is restricted by adjacent plant or obstruction and with less associated excavation of the surrounding ground adjacent to the leak than is necessary with metal muffs and in situations close to other services.

Finally, unlike the metal muff system, it is not necessary to force or pump the encapsulant material into the enclosure formed by the muff in counter-flow against escaping fluid as is the case with the metal muff system. Instead the material may merely be poured into the enclosure formed by the wrappings. Finally the cost of the components in the present system can be much less than the cost of a metal muff.

The present invention also displays several advantages over the envelope leak repair system.

Since this envelope is heavy and bulky it is difficult to handle and manipulate in order to ensure an intimate mix of the resin and hardener and, in any case, it is quite difficult to ensure that these components do mix intimately within an envelope.

Instead, with the present invention, since the resin and hardener are retained separately from the wrappings, they can be mixed intimately and at leisure within any suitable receptacle. In addition, with care, the operator can avoid all contact with the resin when this is being poured into the enclosure whereas such contact is unavoidable if the wrapping comprises a resin-absorbed felt material. Since, the wrappings in the present invention are relatively light they can be applied to the pipe or main relatively easily and leaks can be repaired very much more quickly than is possible either with the envelope leak repair system or especially with the metal muff system.

Claims (26)

1. A method for sealing a leak in a pipe or pipeline carrying fluid under pressure, the method comprising forming with flexible material wrapped circumferentially around the pipe or pipeline an inner enclosure into which fluid leaked from the pipe or pipeline issues and an outer enclosure overlapping the inner enclosure, venting to atmosphere fluid leaked into the inner enclosure without allowing the fluid to enter the outer enclosure, introducing into the outer enclosure a hardenable fluid encapsulant material from a source external of the enclosures, allowing or causing the encapsulant material to harden and sealing off the vent.

2. A method as claimed in claim 1 in which the leaked fluid is vented by way of but without entering the outer enclosure.

3. A method as claimed in claim 1 or claim 2 in which the enclosures are formed by sequentially wrapping around the pipe or pipeline two distinct wrappings of flexible material.

4. A method as claimed in claim 3 in which the fluid is vented to atmosphere by way of a vent duct extending through orifices in the wrappings, the duct being sealingly engaged with the orifices in the wrappings.

5. A method as claimed in claim 4 in which the duct is attached to the outer wall of the pipe or pipeline.

6. A method as claimed in claim 4 or claim 5 in which the orifices are formed by flexible sleeves with which the wrappings are provided and which receive and are sealingly engaged with the duct.

7. A method as claimed in claim 6 in which the sleeve of at least the outer wrapping is releasably engaged with the duct.

8. A method as claimed in any of the preceding claims in which sufficient encapsulant material is introduced into the outer enclosure to cause the outer wrapping to become taut.

9. A method as claimed in either of claims 7 or 8 in which after the duct has been sealed the sleeve of the outer wrapping is released from the duct and further encapsulant material is introduced into the sleeve to enclose the duct and the material is allowed or caused to harden.

10. A method as claimed in any of the claims 3 to 9 in which the outer wrapping has an orifice for the introduction of the encapsulant material into the outer enclosure, the orifice being formed by a flexible funnel.

11. A method as claimed in any of claims 4 to 10 in which, where the fluid is inflammable, and before the duct is sealed, the duct is fitted with a flame trap which is removed before the duct is sealed.

12. A method as claimed in any of the preceding claims in which the flexible material is non-resin absorbent.

13. A method as claimed in claim 12 in which the material is woven nylon having a plastics coating.

14. A method as claimed in claim 11 in which the coating is polyethylene.

1 5. A method as claimed in any of the preceding claims in which the encapsulant material is a resin.

16. A method as claimed in claim 13 in which the resin is a cold curing resin.

17. An assembly for sealing a leak in a pipe or pipeline carrying fluid under pressure by the method according to claim 1, the assembly including two wrappings of a flexible material for wrapping circumferentially around the pipe or pipeline so as to form an inner enclosure into which fluid leaked from the pipe or pipeline issues and an outer enclosure overlapping the inner enclosure, a vent duct for attachment to the pipe or pipeline and for sealing engagement with orifices in the wrappings through which, in use, the duct extends to enable fluid leaked into the inner enclosure to be vented to atmosphere only by way of the duct, means for sealingly engaging the duct with the orifices in the wrappings, an inlet in the wrapping which is to form the outer enclosure for the introduction into the outer enclosure of a hardenable fluid encapsulant material and means for sealing the duct after the encapsulant material has been allowed or caused to harden.

18. An assembly as claimed in claim 17 in which the means for sealing the duct with the orifices includes flexible sleeves with which the wrappings are provided and which form the orifices and are adapted to receive the duct.

19. An assembly as claimed in claim 17 or claim 18 in which the inlet in the wrapping which is to form the outer enclosure is in the form of a flexible funnel.

20. An assembly as claimed in any of claims 17 to 19 in which the means for sealing the duct is a plug.

21. An assembly as claimed in any of claims 17 to 20 in which a removable flame trap is provided for fitting to the duct during the period when fluid is issuing from the duct.

22. An assembly as claimed in any of the claims 17 to 21 in which the flexible material is non-resin absorbent.

23. An assembly as claimed in claim 22 in which the material is woven nylon having a plastics coating.

24. An assembly as claimed in claim 23 in which the coating is polyethylene.

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

26. An assembly substantially as hereinbefore described with reference to the accompanying drawings.