WO2011001189A1

WO2011001189A1 - Apparatus and methods for maintenance and repair of vessels

Info

Publication number: WO2011001189A1
Application number: PCT/GB2010/051103
Authority: WO
Inventors: Nicholas John Ryan; Iain Beveridge Chirnside
Original assignee: Brinker Technology Limited
Priority date: 2009-07-03
Filing date: 2010-07-05
Publication date: 2011-01-06
Also published as: GB2471579A; GB0911579D0; GB201011269D0

Abstract

A method of maintaining a sealing element within a leak site in a vessel comprises the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to trap the sealing element within the leak site between the outer surface of the tube and the inner wall of the vessel. A clamp apparatus for use in the sealing of a vessel comprises a hollow, flexible, elastic tube (1), said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

Description

APPARATUS AND METHODS FOR MAINTENANCE AND REPAIR OF VESSELS

The present invention relates to apparatus for and methods of maintaining or repairing vessels and particularly to apparatus for and methods of maintaining or repairing pipes, particularly leaking, cracked, damaged, corroded or collapsing pipes and also to apparatus for and methods of maintaining the fluid flow capacity of a pipe which has suffered damage, corrosion, leakage or collapse.

Vessels such as particularly pipes and conduits are used in many industries for the transport of fluids from one location to another. For example in the water industry, potable water may be transported along a series of pipes which are laid above or below ground for many hundreds of miles from a reservoir, processing or storage facility to the mains system to emerge from a tap in a home. In the recovery and transportation of hydrocarbons, fluids may be located in a reservoir many hundreds of meters below ground or below the sea. Following recovery the fluids are then transported over many hundreds or thousands of miles to production facilities or end users.

Damage can occur to the pipes at any location and can result among other things for example from internal or external damage to the pipe or from corrosion to the pipe. This can start as a minor problem but over time can escalate to a major problem requiring upheaval such as digging up the pipe or working over a well which may be buried in generally inaccessible areas such as in remote countryside, under roads or within built up areas, offshore or subsea. Sealing devices and methods are known for addressing these problems but it is often the case that a different sealing device or method is required if the pipe is cracked than if the pipe is in danger of collapse through corrosion and therefore it would be advantageous to have a device which could be used to address a variety of different issues arising through maintenance and repair of pipes throughout their working life.

Arterial stents are known in medical applications for applying a force to the internal wall of an artery, oesophagus or other internal duct to facilitate greater flow of blood or air to improve the health of the patient.

A known self expanding stent is described in US Patent No. 4,655,771 and comprises a tubular body which is composed of a plurality of individual rigid but flexible thread elements each of which extends in a helix configuration with the centre line of the body as a common axis. Applying a force to the ends of the tube to push the ends together causes the flexible thread elements to bow outwardly and thereby increase the diameter of the tube. Applying an opposite force to the ends of the tube to pull the ends of the tube apart, causes the flexible threads to be drawn together such that the diameter of the tube is reduced.

In medical applications, the tube is fed into a small bore applicator or syringe and is introduced into the patient's body where it can be activated by applying the appropriate force to the ends of the tube to cause the centre portion of the tube to expand by the required amount to support the internal wall and keep the airway or passageway open.

In such applications the expandable tube may have an expanded diameter of between 6mm and 20mm and of a length between 100 to 200 mm. A 6 mm tube, which may have a contracted diameter of only 2mm or even smaller, is intended to be implanted into a vein with a diameter range of between 4 and 5 mm and a 20 mm tube is intended to be implanted into an aorta with a diameter range of between 15 and 18mm. Therefore it is evident that these devices must be of a generally small size in order that they can comfortably be inserted into an artery or cavity in the human body without causing damage to the surrounding tissue or discomfort to the patient.

The present applicant has recognised that properties of such an arterial stent could be adapted for apparatus used in different industries and in particular for use in mitigating the effects of a damaged or corroded pipe, particularly in relation to water pipes or hydrocarbon pipes.

The present invention therefore seeks to provide an apparatus for and methods of mitigating leaks in vessels and of maintaining or repairing leaking, damaged, corroded or collapsing vessels.

In the present application, vessels include but are not limited to pipes, tubes, ducts and conduits, both circular and non-circular, for the conveyance of fluids, such as liquids, gases, solids and mixtures thereof.

The present invention also seeks to provide an apparatus for use in maintenance or repair of vessels which is flexible in nature yet exerts a radial force onto the wall of the vessel.

According to one aspect of the present invention there is provided a method of sealing a leak in a vessel, the method comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to seal the leak. According to a further aspect of the present invention there is provided a method of maintaining a sealing element within a leak site in a vessel, the method comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a

contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to trap the sealing element within the leak site between the outer surface of the tube and the inner wall of the vessel.

According to a still further aspect of the present invention there is provided a method of repairing a damaged vessel comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to support the wall of the vessel against collapse.

According to a still further aspect of the present invention there is provided a method of lining a vessel comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to provide a lining along the inner wall of the vessel whilst maintaining a fluid flow path through the vessel.

Preferably the diameter of the tube is varied by axial movement of the ends of the tube relative to each other. Preferably the tube is contracted radially by applying a force on the ends of the tube to increase the length of the tube. Preferably also the tube is expanded radially towards the at rest condition by releasing the force on the ends of the tube. Preferably also, the tube can be further expanded radially, beyond the at rest condition, by applying a compressive force to the ends of the tube to thereby increase the radial force applied by the tube against the inner wall of the vessel.

Advantageously the methods of the present invention further comprise selecting a tube of a diameter at rest which is greater than the diameter of the vessel. Advantageously the expandable tube can be removed from the vessel once a permanent seal is established.

According to a further aspect of the present invention there is provided a vessel intervention apparatus comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

According to a further aspect of the present invention there is provided a pipe repair apparatus comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

According to a still further aspect of the present invention there is provided a pipe sealing element comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

According to a still further aspect of the present invention there is provided a clamp for holding a sealing element within a leak site in a vessel wall, the clamp comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression. According to a still further aspect of the present invention there is provided a pipe liner comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression. Advantageously the tube has a diameter in the at rest condition greater than 20mm. Preferably also, the tube has a length in the at rest condition greater than 200mm.

Preferably the tube comprises a body of elastomer. In some embodiments of the invention, particularly in the potable water industry the body comprises silicone or ethylene propylene diene M-class rubber (EPDM ). In other embodiments particularly in the hydrocarbon industries, the body comprises hydrocarbon resistant elastomers such as but not limited to Nitrile Butadiene Rubber (NBR), Hydro Nitrile Butadiene Rubber (HNBR), highly fluohnated polymers or perfluohnated polymers such. Preferably the body is highly elastic and has a low modulus so that the tension required to radially compress the body is not excessive. Preferably a reinforced layer is provided over or within the body of the tube. Conveniently the reinforced layer comprises a helically wound support member. Advantageously, the support member comprises a plurality of helically woven filaments. Preferably the filaments are wound around the body in different directions.

The filaments may comprise flexible plastics or metals or a combination of these materials. Preferably the filaments comprise thermoplastics and preferably flexible thermoplastics, more preferably polyethylene and more specifically MDPE or low density polythene or Nylon when the invention is used in relation to potable water vessels. Alternatively the filaments may comprise steel and preferably stainless steel when the invention is used in relation to potable water or in downhole applications in the hydrocarbon industry.

Alternatively, the support member comprises a woven stainless braiding.

In a further alternative embodiment, the support member may be cast or moulded.

In a still further embodiment, the tube is provided with a plurality of circumferential slots to form a mesh with a variable diameter. Advantageously the tube has a diameter at rest of between 6.5mm and 950 mm, more preferably between 50mm and 200 mm and a length at rest of between 2m and 25m. Embodiments of the present invention will now be described with reference to and a shown in the accompanying figures in which:-

Figure 1a is a schematic perspective view of an expandable tube according to one aspect of the present invention at rest;

Figure 1 b is a schematic perspective view of the expandable tube of Figure 1 in a contracted condition;

Figure 2 is an illustration of the relationship between the winding angle of a support member around the tube and the length of the tube at rest;

Figure 3 is a schematic perspective view of a further embodiment of the present invention with an alternative wound support to that shown in Figure 1 a;

Figure 4 is a schematic perspective view of a further embodiment of the present invention with an alternative wound support to that shown in Figure 3; Figure 5 is a schematic perspective view of a still further embodiment of the present invention with an alternative wound support to that shown in Figure 4;

Figure 6 is a schematic cross section of a part of a tube according to one aspect of the present invention in place within a pipe; Figure 7 is a schematic cross section of a part of an alternatively

configured tube in place within a pipe, and Figure 8 is a schematic perspective view of a further embodiment of the present invention with an alternative support to that shown in Figure 5.

Turning now to Figures 1 a and 1 b, there is shown a tube 1 according to one aspect of the present invention adapted for use in intervention in vessels, particularly but not exclusively to intervention including inspection, maintenance or repair or leaking vessels, and particularly pipes, tubing, casing or ducting.

The tube is hollow and comprises a body 2 formed of a soft flexible elastic material such as silicone or EPDM which are particularly suited for use in the potable water industry as they do not contaminate water that they come into contact with flowing through pipes. The length of the tube may be increased by applying a force to the ends of the tube and pulling them apart. Conversely, the length of the tube may be decreased by applying an opposite force to the ends of the tube and pushing them together.

The body is reinforced with a helically wound support 4 comprising a plurality of filaments which are wound around the tube. The filaments comprise flexible plastics or metals and in particular flexible thermoplastics including but not limited to polyethylene, more specifically MDPE, LDPE or Nylon.

In this embodiment the elastic body is formed around the filaments such that the body and support of the tube is bonded together, however the filaments could also be cast into the body or over moulded by the body. The filaments and body may be combined during manufacture of the tube and the reinforcement layer may be manufactured initially and then incorporated into the flexible, elastic body. In this embodiment the body is formed around the filaments and therefore the inner surface on the tube has a ridged profile defined by the filaments of the support member. In embodiments in which the support member is formed on the outer surface of the body, the inner surface of the tube will be smooth to aid the smooth flow of the fluid within the tube.

In this embodiment each of the filaments is wound around the body with the same pitch or helix angle which in this embodiment is around 45 degrees, but the different filaments are phased around the body such that the filaments cross one another at points 5 along the length of the body. The filaments resist stretching, compression or buckling. The filaments are fused together at the crossing points 5 thereby defining a set of parallelograms between the filaments. The helical diameter of the wound filaments sets the maximum diameter that the tube will adopt in an at rest condition with no force applied to the ends of the tube as the helical support forces the tube outwards to the at rest diameter.

Fusing of the filaments together at the crossing points 5 allows the support 4 to expand and contract independently of the body and sets the angles at the corners of the parallelograms thereby defining the "at rest" condition of the support and hence the tube.

Furthermore, when the tube is placed under tension, for example by applying a pulling force to the ends of the filaments or by applying a compressive force around the tube, the helical filaments tend to straighten thereby increasing the length of the parallelograms between the filaments. As the filaments are fused together at the crossing points 5, straightening of the filaments and consequential lengthening of the parallelograms causes the parallelograms to reduce in width such that the overall length of the body increases and the overall diameter of the body decreases.

As noted above, the diameter of the helically wound support sets the at rest diameter of the tube. The pitch of the helical winding determines the relationship between the axial and radial extension/compression of the tube. For example, as illustrated in Figure 2, the at rest pitch of the helical winding this embodiment is 45 degrees, then an increase in length of 1.32 times achieves a 2 times reduction in the diameter of the tube. This means that for a relatively small axial movement of the ends of the tube in opposite directions, a substantial reduction in the diameter of the tube is achieved.

The preferred range of helix angle is between 60 and 30 degrees.

The tube has a diameter of around 6.5 mm up to around 950mm and preferably around 50mm to 200mm and has a length of around 2m to 25m.

As described above, when a force is applied to the ends of the filaments the diameter of the tube varies in response. When the ends of the filaments are pulled apart the filaments are straightened and this pulls the outer surface of the body radially inwards such that the diameter of the tube decreases. Whilst the pulling force is applied to the ends of the filaments, the straightened filaments will hold the tube in a contracted condition. Alternatively when a compressive force is applied around the body, the filaments are straightened and the length of the body increases in response to a decrease in the diameter. Upon detection of a leak in a wall of a pipe 6, for example a potable water pipe, a sealing element of a type generally known to the skilled person may be deployed into the pipe to form a barrier across the leak to prevent further seepage from the leak. For example, a solution of sealing elements such as elastomer elements described in WO06/126016 may be deployed into the pipe. Such sealing elements will be drawn to the leak by the pressure differential across the leak. Alternatively, the sealing element may be a hollow tube which is deployed into the pipe and guided to the leak site to bridge the leak in the pipe wall.

A tube 1 is selected and loaded into an applicator. The tube is selected to be of a diameter such that at rest the tube has a greater diameter than the diameter of the pipe in question.

The applicator is a cylindrical body with a plunger at one end. The applicator is selected to be of a diameter which is smaller than the diameter of the tube at rest and so holds the tube in a contracted, lengthened condition.

The applicator is introduced into the pipe, preferably through a hydrant upstream of the detected leak, and the tube is fed along the pipe within the applicator to the required location. The tube is then forced from the applicator into the pipe such as for example by actuating a piston within the applicator to push the tube from the applicator. As the tube enters the pipe, the release of the compressive force around the tube causes the filaments to spring back to their at rest position drawing the body of the tube along with them. As the at rest diameter of the tube 1 is selected to be greater than that of the pipe into which the tube is deployed, the tube will expand against the inner wall of the pipe 6 with sufficient force to hold the tubel in position over the sealing element at the leak site and prevent the tube from being washed down the pipe and away from the leak site. The tube may also be selected to provide resistance to reverse flow due to pressure of the water table.

Additionally, drag forces on the leading edge which would tend to push a non-radially expanding tube along a pipe, act to further increase the radial force on the tube and thus retain the tube in the desired location. The tube 1 may remain in position within the pipe 6 to provide a

permanent repair of the pipe. Alternatively, the tube may be used as a temporary measure whilst a permanent repair of the pipe is made. In this case, once the permanent repair is in place, the tube may be removed from the pipe by applying a force to the ends of the filaments and pulling on the ends of the filaments to radially contract the helical support 4 as described above and thus force the elastic body 2 to radially contract such that the tube can be pulled out of the pipe.

In embodiments where the sealing element is held in place by the pressure differential across the leak site, permanent repair of the leak will mean that when the tube is removed, the sealing element can pass along the pipe where it can, for example, be recovered from a hydrant further downstream. In an alternative arrangement, the applicator may be formed as a sheath which covers the tube and retains the tube in a radially contracted condition. Once the tube is inserted into the pipe to be repaired, and is transported to the desired position, the sheath can be withdrawn. As the radially compressive force of the sheath is removed, the tube springs back towards the at rest position in which the surface of the tube is pressed against the inner wall of the pipe.

In a further alternative arrangement, the applicator may be in the form of two ends, joined by an incompressible but flexible member running within the tube such that the ends maintain axial tension on the tube to keep it radially contracted until the ends are released allowing the tube to spring back towards the at rest position. The member may also be a hollow tube allowing for control cables, wires or hydraulics to actuate the release mechanism.

In a simpler arrangement, the tube is drawn into the vessel, either pushed in by a flexible rod from downstream or pulled in by a wire or chord from upstream. In both cases the only attachment to the tube is to the front end of the tube, where the front is defined by the direction of travel. When dragged in this manner, the tube radially contracts as a response to frictional contact with the vessel wall thus reducing the fhctional force, in this manner the tube self-regulates its expansion until such time as the tube is released when it springs back to the at rest position, locking it in the desired position.

Modifications may be made to the tube and particularly to the helically wound support 5 and examples of modified tubes are shown in figures 3 to 7. In figure 3, the support is provided by a single filament helically wound onto the body in a single direction. This provides a simple, cost effective and flexible tube which will have the greatest capacity for expansion.

The embodiment shown in figure 4 provides a first filament wound helically in a first direction and a second filament overlying the first, wound in a second direction, preferably opposition to the first. Figure 5 shows an embodiment in which the various filaments are wound in different directions and woven together such that at some of the crossing points the first filaments overlies the second and at others the second thread overlies the first. This embodiment provides for greater structural support to the tube and also facilitates moulding of the body over the support.

With a woven support the 'at rest' position is substantially created by the elastic sheet being bonded to the support with only a small fraction of the resistance to movement being created by the torsion and bending of the support. The bonding of the elastic sheet prevents the crossover point 5 of the filaments from moving but it allows the filaments to hinge. Fusing them changes the hinge to a fixed joint.

In a further, non-illustrated embodiment, the woven support 5 may be provided in the form of a woven stainless braiding which is set into the body of the tube to provide greater structural strength to provide a flexible self setting straddle.

In a still further non-illustrated embodiment, the flexible body of the tube may be modified by forming circumferential slots in the body and then expanding the body circumferentially while heating to form a mesh. The expanded mesh is then allowed to cool and adopt an at rest shape. This embodiment finds particular application where the cross sectional shape of the support or mesh is rectangular.

Figure 6 shows a partial cross section through a pipe wall 6 and the wound support where the individual threads of the support are generally circular in cross section. The cross sectional shape of the threads adds to the strength of the tube and a change in cross section shape can be used to provide additional outward thrust.

Figure 7 shows a partial cross section through a pipe wall 6 and the wound support where the threads of the support are generally rectangular in cross section. This embodiment exerts additional force onto the pipe wall whilst promoting the expansion or contraction of the tube.

In the embodiments described above the tube of the present invention is utilised to seal a leak in the wall of a pipe cased for example by a hole, crack of split appearing in the wall of the pipe without requiring the introduction of a separate sealing element and this method may be used for sealing both simple and complex leaks and defects in pipes. The tube both as described and as deployed above may address the problem of retaining a sealing element such as for example described in WO 06/126016 in position within a leak site in the wall of a pipe, particularly where the sealing element is held in the leak site by pressure from fluid flowing in the pipe. In cases where the pipe must be drained before inspection, maintenance or repair can be carried out, the present invention provides a means of retaining the sealing element in position within the leak site. In other words, whilst fluid pressure is available within the pipe the sealing element is trapped between the outer surface of the tube and the leak site. When fluid pressure is removed, the tube prevents the sealing element from falling out of the leak site and the pipe may be drained. After fluid flow to the pipe is re-established, the tube may be removed and the pressure of fluid flowing in the pipe will once more retain the sealing element in position within the leak site. This allows the tubes of the present invention to be reused in a number of maintenance operations. Whilst the above described embodiment relates to retaining a sealing element in position within the pipe, it is envisaged that in some

embodiments the tube may be deployed without firstly deploying a sealing element. In these cases, the tube itself can provide a sealing element across a leak site in a pipe.

In a further method of the present invention, a tube as described in relation to the embodiments above may be used to form a bridge between two disjointed pipes or tubulars. In this embodiment, a tube is selected having an at rest diameter which is greater than that of each of the pipes. The tube is inserted in a radially contracted condition between the two pipe ends and the tension or radial compression on the tube is released to allow the tube to spring back to the at rest condition. The tubes of the present invention are particularly suited to bridging two pipes of dissimilar diameter or having an offset as the tube will spring towards the rest position and apply a force against the inner wall of each of the pipes. As the tube is flexible, different parts of the tube may conform to the inner diameter of different pipes such that any offset between the two pipes does not affect the integrity of the seal of the tube against the inner wall of either pipe.

The tubes may be utilised in creating a permanent seal across an open ball valve such that the tube passes through the aperture in the ball valve or indeed through any full bore or near full bore valve. This allows the apparatus of the present invention to be used in repairing faulty valves such as gate valves or sandwich valves.

The apparatus of the present invention may also be used as a support in well bores and particularly in wellbores where a portion of the wellbore is open or unsupported in that there is no casing liner in some part of the well bore.

The apparatus may also be used in sealing off a branch of a junction in a pipe such as for example in sealing off one branch of a T or Y junction or two branches of an X junction.

In a further alternative embodiment of the tube shown in Figure 8, the support 5 may be cast or moulded in a single piece to provide fused joints along the length of the support which will determine the helix angle and allow the support to be used without an internal elastic body and such an embodiment may be particularly suited to a method of retaining a sealing element within the leak site as described above. Alternatively the tubes of the present invention find particular application in relation to supporting a crumbling or disintegrating pipe. In this

embodiment, the tube is deployed into the pipe and serves as an internal support to the pipe to prevent further crumbling or disintegration of the pipe. The tubes may also be particularly useful in supporting a pipe, casing or tubing used in the production or transportation of hydrocarbons from subsidence.

In all of the methods of the invention the structural integrity of the pipe is preserved or in some cases re-established which can greatly extend the useful life of the pipe and also provide for a cost effective and attractive alternative means of repairing or relining old, damaged or worn pipes.

Additionally, the presence of the tube in the pipe does not inhibit or affect normal fluid flow within the pipe and therefore the capacity of the pipe is not adversely affected. In fact, the tube may provide protection to the inner walls of the pipe in preventing the build up of deposits on the wall of the pipe from particles carried in the fluid flow. Furthermore, the tube may also prove useful in protecting against encrustation on or around the inner wall of the pipe. This is particularly important where a leak, crack or split has formed in the pipe wall as the tube may assist in preventing an escalation of the damage to the pipe. In some cases the tube may become a permanent fixture in the pipe as there is no restriction to fluid flow through the tube. Therefore, the tube forms an integral part of the passageway through the original pipe. It will of course be apparent to the person skilled in the art that the methods of the present invention may be used on pipes of varying diameters. The at rest dimensions of the tubes may be selected to suit a varying range of pipe sizes such that the number of different tubes required for a varying range of pipes is reduced.

The methods of the present invention also provide for a cost effective solution to the problem of relining a pipe, and particularly a pipe which has a number of regions of different diameters or areas which deviate from the horizontal or vertical and particularly pipe joints, elbows or bends in the pipes.

It will be apparent to the skilled person that a pipe could be relined by introducing a tube at an appropriate point and feeding the tube through the pipe in a contracted state and then releasing the tube to allow the tube to expand against the inner wall of the pipe thereby avoiding any disruptive work such as digging up roads or pavements to gain access to areas of the pipe which require maintenance or repair.

It will also be appreciated that the flexible and elastic nature of the tubes allows the tubes of the present invention to be employed in addressing leaks and effecting maintenance or repair of pipe joints, elbows or bends in pipes and discontinuities due for example to subsidence of the pipe. The tubes are particularly adapted for deployment through water hydrants which generally comprise a 2.5 inch valve and can travel around 90 degree bends in the valve before being introduced into the water main.

It will also be understood by the skilled person that the detailed description of deployment of the tube in relation to the first embodiment may equally be applied to any of the embodiments as described herein.

Modifications and improvements may be made to any of the foregoing examples within the scope of the invention. For example, where a tool such as an applicator is utilised to deploy the tube within the pipe as described above, the tool may comprise means to locate the tube at the required location within the pipe, adjacent the leak. For example, the tool may comprise one or more hydrophones, sonar or camera positioning systems such that the progress of the tool along the pipe towards the leak can be closely monitored to ensure that the tube is deployed from the tool most efficiently and at the optimum location.

In a further modification of any of the above described embodiments, the body of the tube may comprise or be formed of a swellable elastomer material such that swelling of the body, for example upon contact with water or hydrocarbons such as oil or gas, aids the self setting action of the tube within the pipe. Suitable elastomers include water swelling rubber such as cross-linked polyvinyl alcohol, crosslinked polyacrylate, crosslinked starch-acrylate copolymer or a water swellable urethane resin or a hydrophilic group containing rubber. Alternatively the tube may comprise or be formed of a cross linked polymer which increases in volume when exposed to an activating agent such a solvent swelling elastomers, Alternatively, a coating may be provided on the outer surface of the tube, the coating comprising a swellable elastomer as described above to aid sealing between the outer surface of the tube and the inner surface of the pipe.

As an alternative to a swellable elastomer, the tube may be provided with a soft compliant coating with a very low modulus such as a highly flexible silicone rubber or polyurethane polymer with hardness of less than 10 Shore A.

In a further modification, the coating may comprise a semi-cured elastomer or polymer which seals against the inner wall of the pipe and sets the tube in place within the pipe. Suitable materials include a hydrophobic thixotropic polyurethane or a thixotropic epoxy resin.

In a further modification the thickness of the tube may vary over the length of the tube. For example, it is envisaged that the ends of the tube may be thicker than the remaining body of the tube. In this modified embodiment, the tube may be deployed into a pipe in the radially contracted condition as described above. At the required location in the pipe, the tension or radial compression on the tube is released such that the tube springs back to the at rest condition and applies a force against the inner wall of the pipe. By careful selection of the diameter of the tube and the helix angle of the support, the thickened ends of the tube may form a seal against the inner wall of the pipe whilst an annulus is established between the inner wall of the pipe and the outer surface of the remainder of the tube. A sealing material such as a semi-cured polymer or elastomer, for example an epoxy resin system or a polyurethane is pumped into the annulus and allowed to set. Once the sealing material has set, the tube may be removed from the pipe as described above by restoring a tension or radial compression on the tube to cause the tube to return to the radially contracted condition. With the tube removed from the pipe, the sealing material forms a permanent seal around the inner surface of the pipe. In a further modification, the tube may be as described above but instead of being hollow, the tube may be solid or the ends of the tube may be closed to form a surface against which fluid flowing in the pipe can apply a force. In this modification, fluid flowing in the pipe will flow against the surface at the end of the tube and push against the tube which will tend to force the tube towards the at rest condition in which the tube expands radially to fill the pipe and lock the tube in place. The tube may be removed from the pipe for example by applying a pulling force on either end of the tube such that the body of the tube is stretched thereby causing radial compression of the tube as previously described. In this

modification, the tube provides a self setting pipe plug in which pressure of the fluid flowing in the pipe can be used to set the plug, thereby isolating pressure in one portion of the pipe from another. The diameter of the tube relative to the diameter of the pipe may be selected depending upon the pressure applied by fluids flowing in the pipe such that an increase in pressure above a certain level causes the plug to be set thereby

preventing damage occurring to the pipe downstream

As described above in relation to the specific embodiment, the inner surface of the tube may be smooth or may have a profile formed by the support member around which the tube is formed. In a further

modification the inner surface of the tubes of the present invention may be provided with an anchor profile within the pipe from which further equipment such as plugs, balls or the like could be hung. This feature would be particularly useful in a downhole environment as at present anchor points are only placed at specific points within downhole tubing or pipe and this would enable an anchor point to be placed at will at any point along the pipe or tubing.

It is envisaged that the methods of the present invention will find particular application in the water industry and the oil and gas industry and most particularly in distribution of fresh water and particularly potable water. The methods of the present invention are particularly adapted for addressing leakage, damage, maintenance or repair of trunk mains and distribution pipes.

The methods of the present invention are also particularly adapted for use in addressing these issues in relation to waste water pipes, both domestic and industrial, where the pipes have either a small or large bore. The elastic nature of the tubes allows for a relatively small range of tube sizes to be provided to service a relatively large range of pipe sizes.

The methods of the present invention may equally find application in maintenance or repair of irrigation or drainage pipes. It is envisaged that the above described apparatus and methods may also be adapted for use in the oil and gas industries such as for example in providing an apparatus for and method of lining a flexible pipe.

The apparatus and methods of the present invention may be used in the maintenance or repair of downhole tubulars to provide expandable sealing of cracks, or holes, replacing straddles or as flexible sand screens. The apparatus and methods of the present invention may be used to replace straddles within downhole tubulars such that a tube as described above may be run into the tubular in a radially compressed condition and then released at the required location by release of the compressive force on the tube. The tube would then spring radially outwards and exert a force against the wall of the tubular with sufficient force to retain the tube in position and to seal perforations in the wellbore in the region covered by the tube. Such an application would avoid the need for a complex straddle with sealing devices at either end which require careful selection of components to ensure an effective seal is made between the straddle and the tubular. Such straddles have a very limited amount of expansion and so are limited in their use to near to full bore applications. Such a tube acting as a straddle replacement may comprise or incorporate a swellable material as described above. The material may be selected such that swelling occurs when the material comes into contact with water. Suitable materials include cross-linked polyvinyl alcohol, crosslinked polyacrylate, croslinked starch-acrylate copolymer or a water swellable urethane resin or a hydrophilic group containing rubber, or a cross linked polymer which increases in volume when exposed to an activating agent such a solvent swelling elastomers. In this case, the tube does not impede flow of fluids from the perforations in the well whilst hydrocarbons are flowing into the well but as soon as the flow incorporates a sufficient percentage of water, the coating swells and thereby acts to radially expand the tube to seal off the perforations against further fluid flow.

This may be particularly useful in sealing a watered out lateral on a multilateral well such that as the water level within the lateral rises, the coating of the tube swells to seal and/or isolate a particular branch of the multilateral well.

Upon reduction of the water percentage of the fluid flowing in the well, the coating may return to the rest position and the tube may be contracted radially such that the tube can be removed from the well for re-use. The apparatus and methods of the present invention may also be used in process industries in relation to sealing or lining of pipes or conduits. It will be appreciated by the person skilled in the art that the apparatus of the present invention may be deployed into a pipe or vessel to the required location and then remotely activated to cause the tube to move from the radially contracted condition to the radially expanded condition. This provides for greater flexibility of use of the apparatus in remote locations and harsh environments.

Claims

1. A method of maintaining a sealing element within a leak site in a vessel, the method comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to trap the sealing element within the leak site between the outer surface of the tube and the inner wall of the vessel.

2. A method of sealing a leak in a vessel, the method comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to seal the leak.

3. A method of repairing a damaged vessel comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to support the wall of the vessel against collapse.

4. A method of lining a vessel comprising the steps of introducing a radially compressible hollow elastic tube, held under axial tension or radial compression into the vessel, the tube being radially compressed from an at rest condition to a contracted condition, the method further including the step of releasing the tension or compressive force on the tube such that the tube expands radially from the contracted towards the at rest condition against the wall of the vessel to provide a lining along the inner wall of the vessel whilst maintaining a fluid flow path through the vessel.

5. A method according to any of claims 1 -4, wherein the diameter of the tube is varied by axial movement of the ends of the tube relative to each other.

6. A method according to claim 5, wherein the tube is contracted

radially by applying a force on the ends of the tube to increase the length of the tube.

7. A method according to claim 6, wherein the tube is expanded

radially towards the at rest condition by releasing the force on the ends of the tube.

8. A method according to claim 7, wherein the tube is further

expanded radially, beyond the at rest condition by applying a compressive force to the ends of the tube to thereby increase the radial force applied by the tube against the inner wall of the vessel.

9. A method according to any of claims 1 -8, wherein the tube is selected to be of a diameter at rest which is greater than the diameter of the vessel.

10. A method according to any of claims 1 -9 including the step of

removing the tube from the vessel once a permanent seal is established.

11. A clamp apparatus for holding a sealing element within a leak site in a vessel wall comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

12. A sealing element apparatus comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

13. A pipe liner apparatus comprising a hollow, flexible, elastic tube, said tube being radially compressible from an at rest condition to a contracted condition when held under axial tension or radial compression.

14. An apparatus according to any of claims 11 -13, wherein the tube has a diameter at rest of between 6.5mm and 950 mm.

15. An apparatus according to claim 14, wherein the diameter at rest is between 50mm and 200 mm.

16. An apparatus according to any of claims 11 -13, wherein the tube has a diameter in the at rest condition greater than 20mm.

17. An apparatus according to any of claims 11 -16, wherein the tube has a length in the at rest condition greater than 200mm.

18. An apparatus according to any of claims 11 -16, wherein the tube has a length at rest of between 2m and 25m

19. An apparatus according to any of claims 11 -18, wherein the tube comprises a body of elastomer.

20. An apparatus according to claim 19, wherein the body comprises silicone or ethylene propylene diene M-class rubber (EPDM ).

21. An apparatus according to any of claim 19, wherein the body

comprises hydrocarbon resistant elastomers.

22. An apparatus according to claim 21 , wherein the body comprises Nitrile Butadiene Rubber (NBR), Hydro Nitrile Butadiene Rubber

(HNBR), highly fluorinated polymers or perfluohnated polymers.

23. An apparatus according to any of claims 11 -22, wherein the body is highly elastic and has a low modulus.

24. An apparatus according to any of claims 11 -23, wherein a

reinforced layer is provided over or within the body of the tube.

25. An apparatus according to claim 24, wherein the reinforced layer comprises a helically wound support member.

26. An apparatus according to claim 25, wherein the support member comprises one or more helically woven filaments.

27. An apparatus according to claim 26, wherein the support member comprises a plurality of filaments wound around the body in different directions.

28. An apparatus according to claim 26 or 27, wherein the filament(s) comprise flexible plastics or metals or a combination of these materials.

29. An apparatus according to claim 28, wherein the filament(s)

comprise thermoplastics.

30. An apparatus according to claim 29, wherein the filament(s)

comprise polyethylene, MDPE or low density polythene or Nylon

31. An apparatus according to claim 28, wherein the filament(s)

comprise steel.

32. An apparatus according to any of claims 11 -24, wherein the support member comprises a woven stainless braiding.

33. An apparatus according to any of claims 11 -24, wherein the support member is cast or moulded.

34. An apparatus according to any of claims 11 -24, wherein the tube is provided with a plurality of circumferential slots to form a mesh with a variable diameter.

35. A vessel intervention apparatus substantially as hereinbefore described with reference to and as shown in any of Figures 1-8 of the accompanying drawings.