GB2535196A

GB2535196A - System and method for lining pipes

Info

Publication number: GB2535196A
Application number: GB1502338.5A
Authority: GB
Inventors: John De Rosa Philip; Graeme Pipe Antony; Bishop Bain Stephen
Original assignee: Radius Systems Ltd
Current assignee: Radius Systems Ltd
Priority date: 2015-02-12
Filing date: 2015-02-12
Publication date: 2016-08-17
Anticipated expiration: 2035-02-12
Also published as: GB201502338D0; GB2535196B

Abstract

A system and method for lining a host pipe 1 with a liner pipe 10 is provided, in which access to the host pipe 1 is only achieved from a proximal end. The system comprises a flexible liner pipe 10 with an outside diameter less than the inside diameter of the host pipe 1, and a sealing apparatus which seals between the liner pipe and the host pipe. The sealing apparatus comprises a flexible sleeve 14 attached on the outer distal end of the liner pipe 10 to form a pressure-tight seal, which receives a filler material which causes the sleeve 14 to expand towards the inner surface of the host pipe 1. The seal also comprises a packer 17 inserted into the liner pipe which maintains the liner pipes cross-sectional shape against forces experienced during insertion of the liner pipe 10 into the host pipe 1 and during expansion of the sleeve 14 with filler material. The system further comprises a fitting 16 which provides a pressure-tight seal between the liner pipe 1 and the flexible sleeve 14, the fitting 16 including an axially-extending port through which the filler material can be introduced into the sleeve 14.

Description

SYSTEM AND METHOD FOR LINING PIPES

[0001] This invention relates to a system and method for lining tubes or pipes and for stabilising the space between the liner pipe and the host pipe, particularly but not exclusively for use in offshore petrochemical extraction facilities.

[0002] The method for stabilising the annular space between the outside diameter of a loose-fitting liner pipe and the internal diameter of an existing ("host") pipe is particularly useful where access to the annular space between the liner pipe and the host pipe is only available at one end of the liner pipe/host pipe combination.

BACKGROUND

[0003] There exist certain industrial applications (Figure 1) in which a tank-like structure (5) is used for the storage and supply of a fluid B (3). Supply of fluid B (3) out of the discharge point (4) of the tank-like structure (5) is accomplished by pumping a second fluid A (2), which has a lower specific gravity that fluid B (3), through a dipper tube (1) which is set through the side of the tank-like structure (5) and passes to close to the bottom of the tank-like structure (5). This causes the boundary between fluid A (2) and fluid B (3) to rise up the structure, thereby causing fluid B (3) to discharge at point (4). When it is necessary to replenish the stock of fluid B (3) in the tank-like structure, this is accomplished by connecting a supply of fluid B (3) at point (4), and then reversing the procedure by pumping out fluid A (2) from the tube (1).

[0004] In a particular embodiment of this, the tank-like structure (5) is the hollow steel leg supporting a facility for the extraction of crude petrochemicals from subsea reservoirs; fluid A (2) is (sea)water; fluid B (3) is diesel fuel; and dipper tube (1) is constructed from mild or carbon steel and includes at least one bend of approximately 90° at its upper end, usually of short-radius design, and potentially others located further along its length towards the lower end as required at the time of construction in order to negotiate structural features inside the hollow steel platform leg.

[0005] With the passage of time in service, the unprotected surfaces of the mild or carbon steel dipper tube (1) will be corroded as a result of prolonged exposure to seawater. If the structure is operated to beyond its design life, the dipper tube (1) may become perforated due to corrosion at positions above the boundary between fluid A (2) and fluid B (3). Owing to the pressures used to displace fluid B (3) out of the tank-like structure (5), there is a risk that fluid A (2) will be mixed into fluid B (3), thereby contaminating fluid B (3) and rendering it less or even unsuitable for its intended application.

This is a particular industrial problem where the specific application is as described above, i.e. the tank-like structure is the supporting leg of a facility for the extraction of crude petrochemicals from subsea reservoirs, fluid A (2) is seawater and fluid B (3) is diesel fuel.

In this situation, the contamination of the diesel fuel with amounts of seawater will impair the efficiency of the fuel for its intended application(s) on the facility, will cause unwanted corrosion to components of equipment fed by and handling the diesel fuel; and in extreme cases may cause the equipment to stop functioning.

[0006] One apparently simple solution illustrated in Figure 2 would be to abandon and close the dipper tube (1) with a sealing plate (8), and make a new connection (6) through the wall of the tank-like structure (5) close to its base where fluid A (2) can be injected into the reservoir of fluid in the base of the tank-like structure (5). However, in the practical embodiment described above, this would be a technically difficult, hazardous and highly expensive process, as it would involve the attachment of a flange connection to the base of the structure leg, which may be over 100 metres below sea level, by hyperbaric welding.

[0007] An alternative would be to consider the possibility of lining the existing dipper tube, so as to seal any existing perforations, and to anticipate the sealing of any further perforations of the dipper that might appear after lining.

[0008] There are many commercially-available technologies for lining pipes of the sizes in question (i.e. 75mm bore and greater). These include spray lining with structural resins; inserting a new pipe having a smaller outside diameter than the internal diameter of the existing target ("host") pipe, and either leaving a residual annulus or reverting the liner pipe to give a close fit with the internal diameter of the existing target ("host") pipe; or by inserting a soft liner tube, impregnated with an uncured resin into the existing target ("host") pipe, and then expanding the soft liner into intimate contact with the host pipe and causing it to cure and harden in situ (Cured-In-Place Pipe (CIPP) liners). In general, these commercially-available lining technologies require access to both ends of the section of existing host pipe to be lined, in particular so that the existing host pipeline can be cleaned internally to receive the proposed lining solution. Whilst this can be arranged in many practical onshore applications, this would not be feasible in the particular industrial embodiment described above, as it would require the evacuation of the contents of the platform support leg, which in turn would jeopardise the stability of the platform.

[0009] Certain CIPP lining technologies have been adapted so that these can be inserted from one end only of the section of existing host pipe requiring to be lined. However, these would not be of use in the particular industrial embodiment described above, owing to the significant pressures that would be required to displace the fluid present in the dipper tube in order to deploy the soft liner by the method of liner inversion conventionally used for such single-end access situations; the impairment of the curing processes involved in hardening the resin as a result of contact with the fluids in the dipper tube; the potential solvation of the resin and/or the membranes used to contain it within the soft liner tube during the liner insertion/deployment stage; and importantly the thermal conduction ("heat sink") effect generated by the large volumes of cold fluids present in the platform leg, which would render uncertain the quality of resin cure that could be achieved. In addition, this method would require the robotic cutting of the lower end of the lining in order to reopen the dipper tube, which would be technically challenging at such a depth under the mixture of fluids present.

[0010] It is an object of the present invention to provide improved solutions for lining a host pipe which can be only accessed from one end.

BRIEF SUMMARY OF THE DISCLOSURE

[0011] In accordance with a first aspect of the present invention there is provided a system for lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end thereof, the system comprising: a flexible liner pipe having a proximal end and a distal end and whose outside diameter is less than the inside diameter of the host pipe; a sealing apparatus for sealing an outside surface of the liner pipe with respect to an inner surface of the host pipe, wherein the sealing apparatus comprises: a flexible sleeve attachable at a distal end thereof to form a pressure-tight seal on the outside surface of the liner pipe and capable of receiving a filler material which causes the sleeve to expand towards the inner surface of the host pipe; a packer insertable into the liner pipe and capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material, and a fitting capable of effecting a pressure-tight seal between the liner pipe and the flexible sleeve at a proximal end of the flexible sleeve.

[0012] Preferably, the filler material is a curable grout, for example a thermosetting resin such as epoxy resin, polyurethane or polyurea.

[0013] The fitting may include an axially-extending port through which the filler material can be introduced into the sleeve and, preferably a second axially-extending port through which air can be vented and/or egress of filler material can be monitored or observed.

[0014] In an embodiment, the fitting includes a third axially-extending port to which a pressure gauge can be attached in order to monitor the pressure inside the sleeve.

[0015] Preferably, the flexible sleeve is generally cylindrical in its expanded configuration and may have an external diameter substantially equal to the internal diameter of the host Pipe.

[0016] In an embodiment, the flexible sleeve is attached at its distal end thereof to the outside surface of the liner pipe by means of fusion welding, adhesive bonding and/or mechanical strapping.

[0017] The flexible sleeve may comprise a flexible PVC sheet, preferably reinforced with polyester fibre.

[0018] Preferably the fitting is generally toroidal in shape.

[0019] In a preferred form, the liner pipe is a flexible corrugated pipe.

[0020] In an embodiment, the distal end of the liner pipe includes one or more slots extending axially from the distal end which allow the diameter of the distal end of the liner pipe to be reduced by compression. Preferably, the slots are generally triangular, forming compressible tongues at the distal end of the liner pipe.

[0021] In an embodiment, one or more radial holes are provided in the liner pipe at or near the distal end thereof, allowing fluid communication with the interior of the liner pipe.

[0022] The system may further comprise a flexible strip of low friction material which can be placed intermediate the host pipe and liner pipe to facilitate pushing of the liner pipe into the host pipe. Preferably, the flexible strip includes a flange at its proximal end which can be removeably attached to the proximal end of the host pipe. Further preferably, the flexible strip is sufficiently long to extend from the proximal end of the host pipe and past a first bend in the host pipe.

[0023] In an embodiment, the packer is generally cylindrical and contains a filler which is stiff in the radial direction and sufficiently flexible in the axial direction to conform to the shape of the liner pipe in which it is located. Preferably, the packer comprises a length of flexible, axially-and circumferentially-reinforced high pressure hose. The filler may be a solid fine grade particulate material, for example sand.

[0024] In an embodiment, the outside diameter of the packer is substantially equal to the inside diameter of the liner pipe. Alternatively, the outside diameter of the packer is less than the inside diameter of the liner pipe and the space therebetween is filled with a sheath of flexible material.

[0025] According to a second aspect of the invention there is provided a method of lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end using a system as claimed in any of the preceding paragraphs.

[0026] According to a third aspect of the invention there is provided a method of lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end, the method comprising the steps of: providing a flexible liner pipe having a proximal end and a distal end and whose outside diameter is less than the inside diameter of the host pipe; inserting the distal end of the liner pipe into the proximal end of the host pipe and urging the liner pipe partially into the host pipe; attaching a distal end of a flexible sleeve to an outside surface of the liner pipe so as to form a pressure-tight seal on the outside surface of the liner pipe; inserting a packer into the liner pipe which is capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during further insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material continuing to urge the liner pipe, now with flexible sleeve attached, into the host pipe, until the distal end of the liner pipe reaches a desired position with respect to the distal end of the host pipe; attaching a fitting capable of effecting a pressure-tight seal between the liner pipe and the flexible sleeve at the proximal end of the flexible [0027] Preferably, the method comprises an initial step of attaching a flexible strip of low friction material to the proximal end of the host pipe, the strip being intermediate the host pipe and liner pipe to facilitate pushing of the liner pipe into the host pipe.

[0028] Preferably, the host pipe includes at least one bend and the distal end of said flexible liner pipe is urged past said bend during said insertion step. In a preferred form, the step of continuing to urge the liner pipe ends when the flexible sleeve is in the region of the bend in the host pipe.

[0029] In an embodiment, the packer is capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during further insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material, particularly in the region of the bend in the host pipe.

[0030] If the outside diameter of the packer is less than the inside diameter of the liner pipe, the space therebetween may be filled with a sheath of flexible material.

[0031] Preferably, the packer is capable of maintaining the cross sectional shape of the liner pipe by resisting the forces experienced by the liner pipe as it is urged into and through the first bend on the host pipe; and subsequently the radially-inward forces during the step of inserting a filler material into the sleeve.

[0032] Preferably the method further comprises the step of cutting the proximal end of the packer and withdrawing the filler, for example by vacuum removal, and then removing the packer from the liner pipe. The method may further comprise the step of holding the sheath so that it does not move axially with respect to the liner pipe and then gripping and withdrawing the packer from the liner pipe.

[0033] In an embodiment, the method further comprises the step of waiting for the filler material to cure after inserting the filler material. The step of sealing said port may be performed by the cured filler material.

[0034] In an embodiment, the method further comprises the step of, after the filler is cured, removing the fitting and a proximal portion of the sleeve and filler and attaching a long-term pressure-tight fitting to the liner pipe and, optionally, the host pipe.

[0035] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: [0037] Figure 1 (PRIOR ART) is a schematic cross-sectional view of a hollow leg of an oil platform showing the displacement of a fluid B by a fluid A; [0038] Figure 2 shows a possible method of replacing the dipper tube, not part of the claimed invention; [0039] Figure 3 shows a possible method of lining the dipper tube with a flexible liner tube; [0040] Figure 4A shows a flexible solid wall pipe suitable for use as the flexible liner tube; [0041] Figure 4B shows a flexible corrugated wall pipe suitable for use as the flexible liner tube; [0042] Figure 5 shows apparatus for lining the dipper tube including a flexible sleeve and a reinforced hose packer; [0043] Figure 6 is a perspective view of the distal end of an embodiment of the liner tube; [0044] Figure 7 is an end view and cross sectional view of a toroidal fitting; [0045] Figure 8 is a schematic representation of a flexible low friction strip in place on the proximal end of the liner tube; [0046] Figure 9 shows the dipper tube being lined with the flexible liner tube, with the low friction strip and cylindrical packer in place and with the flexible sleeve in a deflated condition; [0047] Figure 10 shows the dipper tube being lined with the flexible liner tube, with the low friction strip having been removed, the cylindrical packer in place and with the flexible sleeve in an inflated condition filled with grout and with the toroidal fitting in place; and [0048] Figure 11 shows the dipper tube of Figure 10 with the toroidal fitting in place

DETAILED DESCRIPTION

[0049] A possible solution for lining a host pipe (in this case dipper tube (1)) which can only be accessed from one end is shown in Figure 3. This involves the insertion of a flexible liner pipe (in this case a length of flexible tube (10)) into opening (9) of the dipper tube (1) and pushing the flexible tube (10) into the dipper tube until its leading or distal end reaches the required depth to remain permanently within the volume of fluid A (2) at the base of the tank-like structure (5). The flexible tube (10) might be provided in discrete lengths which can be securely jointed together into a continuous string with pressure tight joints, or could be in the form of a single continuous length. The flexible tube (10) may be produced from a wide range of material options and in a wide variety of forms according to the required application. Pipes made of thermoplastic materials are particularly well suited for this application, and in particular polyolefins, such as polyethylene.

[0050] Referring to the arrangement shown in Figure 3, it can be seen that the flexible tube (10) has to be urged into place from one end only because access to the dipper tube (1) is only possible from its proximal end at opening (9). Ensuring that the flexible tube (10) turns the bend (11) is particularly difficult. If this is not done properly, the flexible tube may become wedged in the bend (11), or even be accidentally pushed through the wall of the bend (11) which may be corroded or otherwise already damaged.

[0051] In industrial applications it is often desirable to minimise any reduction in the flow capacity that was originally available from the dipper tube (1). It is therefore preferred to use a flexible tube (10) of maximum diameter possible whilst still being able to be urged into place by pushing past the bend (11) in the dipper tube. Owing to the demands of the facility construction design, and for compactness, it is often the case that the bend (11) will have a small radius, for example 1.5 times the diameter of the dipper tube (1). This in turn presents practical challenges in being able to maximise the diameter of the flexible tube (10) whilst still being able to insert the flexible tube (10) into the dipper tube (1) at the insertion point (9) and negotiate the bend (11) without strut/buckling collapse of the section of pipe (12) projecting from the insertion point occurring.

[0052] Flexible tube construction options that could be used for this application include, but are not limited to, solid wall flexible pipe (Figure 4A) and corrugated wall pipe (Figure 4B). In both cases judicious choice is required to select an appropriate combination of flexible liner pipe diameter and liner pipe wall thickness that can be inserted through opening (9) into the dipper tube (1) and negotiate the bend (11) without creating an unacceptable degree of permanent distortion to the inserted flexible tube (10) over its length. Owing to the potential friction and binding between the flexible tube (10) and the dipper tube (1), particularly at the bend (11) on insertion, this will require that the outside diameter of the flexible tube (10) to be inserted to be substantially smaller than the internal diameter of the dipper tube (1).

[0053] Given this necessary configuration, the annular space that will remain between the inserted flexible tube (10) and the existing dipper tube (1) will present a potential threat to the structural stability of the inserted flexible tube (10). In operation, the hydrodynamic forces generated by the flows of fluids through the inserted flexible tube (10) will result in mechanical perturbations of the inserted tube (10) which will cause it to displace, potentially violently within the confines of the dipper tube (1), with the risk of damage and perforation of the flexible tube at points along its length. Alternatively, rapid changes in the velocity of fluid A (3) flow (e.g. as a result of pump shut-down, particularly when associated with operation of non-return valves in the pipe line) may result in the flexible liner tube (10) experiencing subatmospheric internal pressure excursions (i.e. full/ partial vacuum conditions) along its length, which then may result in inward buckling collapse of the flexible tube, thereby impeding flow, and, if suffered repeatedly, potential fatigue failure of the flexible tube (10) itself. This is of special concern at the bend (11), where the complex and unpredictable axial and cross sectional geometry of the flexible tube (10) through the bend after insertion would confound any meaningful attempts to predict the critical pressure differential required to cause buckling collapse of the flexible tube (10) by conventional engineering design formulae.

[0054] In conventional pipe lining practice, these risks are commonly mitigated by injecting a flowing material (typically, some form of grout that will cure to form a solid mass) into the residual annular space between the host pipe (here, the dipper tube (1)) and an inserted, loose-fitting liner pipe (here, the flexible tube (10)).

[0055] The grout may be formulated from a wide range of materials, including both cementitious products and organic resin materials. The choice of grout material will be governed by the proposed application, and this will be selected to ensure compatibility with both the existing host pipe and the inserted liner pipe, and also to avoid unacceptable impact on the environment surrounding the lined pipeline.

[0056] Once cured, the annulus grout prevents lateral movement of the inserted liner pipe inside the host pipe. In addition, the stiff mass of material filling the annular space between the host pipe and the liner pipe significantly increases the resistance of the inserted liner pipe to buckling collapse that might be caused by the generation of a pressure differential across the liner pipe wall.

[0057] In conventional pipe lining practice, the annular space between the existing host pipe and the inserted liner pipe is sealed at each of the two extremities of the lined pipe section, and the grout material is injected through ports fitted through the wall of the host pipe, and is allowed to fill the annular space until excess material is vented through other open ports also provided in the wall of the host pipe.

[0058] However, in the arrangement described above and illustrated in Figure 3, the conventional approach for grout injection cannot be used, owing to the open annulus at the distal end (13) of the flexible tube (10) which cannot be accessed for the reasons described previously.

[0059] Described herein are components and a method that can successfully be used to grout the annular space between the flexible tube (10) and the dipper tube (1) where access is only possible via one end at the single point of access (9) which is at the proximal end of the dipper tube (1).

[0060] In overview (Figure 5), a cylindrical sleeve (14) of thin, flexible, extensible and strong material that is capable of resisting an internal pressure when sealed at its ends, and having an external diameter equal to or marginally smaller than the internal diameter of the existing host pipe (dipper tube, (1)), of an appropriate length is slid over the flexible tube (10). The leading or distal end of the cylindrical sleeve for insertion (15) is then gathered together and suitably secured onto the outside diameter of the flexible tube at an appropriate position along the length of the flexible tube (10) to form a pressure-tight seal with the flexible tube (10) that will enable the flexible sleeve (14) to be inflated into contact with the bore of the existing host pipe (in this case, the dipper tube (1)) from the end remote from this seal, once this combination of flexible tube (10) and flexible sleeve (14) has been inserted into the host pipe (in this case, the dipper tube (1)).

[0061] In the embodiment described above, a flexible material is required for the sleeve (14) so that it can be gathered up lengthwise between the insertion point (9) and the pushing means (not shown) that is used to urge the flexible pipe(10)/flexible sleeve (14) assembly into the insertion point towards, and around, the bend (11), so as to reduce the risk of strut collapse (Euler buckling) of the free length of flexible tube between the bend (11) and the pushing means, which would otherwise prevent insertion of the flexible tube (10)/ flexible sleeve (14) combination into the existing host pipe (in this case, the dipper tube (1)).

[0062] The leading or distal end of the flexible sleeve (15) can be secured and sealed pressure-tight to the outside diameter of the flexible tube (10) by any suitable means, including but not limited to fusion welding, adhesive bonding, mechanical strapping, either singly or in combination of any of these options, together with the incorporation of suitable sealant materials, as appropriate. The principal requirement for the completed joint/seal is that it will be able to withstand the sliding friction forces that it will experience as the flexible tube (10)/flexible sleeve (14) combination is inserted into the existing host pipe (in this case, the dipper tube (1)), and particularly as it negotiates the bend (11), or as a result of contact with any significant internal projections present in the bore of the existing host pipe that could not be fully removed prior to liner insertion, without displacement and/or detachment and/or leakage on subsequent pressurisation with grout.

[0063] A further requirement is to ensure that the cross section of the inserted flexible tube (10) around the bend (11) is maintained as circular as possible and is stabilised and supported against collapse or distortion whilst grout is injected into the annular space between the flexible tube (10) and the inflatable flexible sleeve (14). Technology which might be considered applicable for this situation can be found in the field of domestic plumbing applications, where long, flexible, spring-like tools are inserted into copper tube to maintain its cross section and profile, principally to avoid generating transverse geometric defects ("kinks"), as it is manipulated into a curve of the desired radius. Owing to the smooth bore of the copper tube and the facility to reduce temporarily the diameter of the spring-like tool by twisting, it is possible to extract the tool to leave the bore of the curved copper tube clear, with no significant reduction of flow capacity.

[0064] Whilst such tools are practical for preventing the kinking of the small diameter copper tubing typically used for plumbing, such technology would not scale up to the larger sizes of flexible tube that would be required for the particular embodiment described above. A novel solution has been developed for the latter application in which a packer, for example a length of flexible, axially-and circumferentially-reinforced high pressure hose (17), slightly longer in length than the distance from the position of the leading end (15) of the inflatable flexible sleeve (14) to the position on the flexible tube (10) where the liner end termination will ultimately be fitted, is sealed at one end (18) and then is packed with a suitably fine grade of a solid particulate material (19) (such as sand, although other particulate materials may be equally effective), and then sealed at the second end (20), so as effectively to produce a cylindrical packer which is highly stiff in the radial direction, but adequately conformable in the axial direction. The reinforced high pressure hose (17) may be replaced with a packer of any type, shape or configuration so long as it is capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material [0065] The reinforced high pressure hose (17) used for the packer may be selected so that its outside diameter is equal to the original internal diameter of the flexible tube (10) to be used to line the existing host pipe (in this case the dipper tube (1)). An alternative and convenient solution has been to use a standard size of reinforced high pressure hose with an outside diameter somewhat smaller than the original internal diameter of the flexible tube (10), and to surround the particulate filled and compacted hose packer with a tubelike sheath of flexible material of a thickness appropriate to fill the annular space between the outside diameter of the filled packer and the internal diameter of the flexible pipe (10).

The tube-like sheath of flexible material may be cut helically or in any other appropriate configuration to enable it better to negotiate the bend (11) as one with the packer, so as to maintain the cross section shape of the packer, and thereby the cross section of the inserted flexible liner pipe (10) through the bend (11). In the case of the close-fitting packer, after the flexible tube (10) has been inserted into the host pipe (in this case the dipper tube (1)) and has been grouted in place, the packer can be retrieved by cutting open the end (20) projecting from the insertion point (9) and extracting the particulate material (19) e.g. by vacuum, to allow the reinforced high pressure hose (17) to be collapsed and withdrawn to leave the bore of the inserted flexible tube (1) clear. In the alternative case, the helically-(or other) cut tube of flexible material wrapped around the particulate-filled packer may be gripped by the pushing means which, when operated in reverse, can be used to extract the packer still filled with the particulate material (19).

[0066] It is desirable to facilitate the first negotiation of the pipeline bend (11) by the leading or distal end of the flexible tube (10) as it is inserted and pushed through the entry point (9). Two complementary solutions have been developed and successfully deployed to accomplish this.

[0067] One possibility is that, prior to insertion, sections having a nominally isosceles triangular shape are cut from each side of the leading or distal end of the flexible tube (10) to leave two tongues (21, 22) of material of increased flexibility in the axial direction of the flexible tube (10), one (21) at the crown of the flexible pipe (10) as it is inserted, and the second (22) at the invert, as illustrated in Figure 6. These flexible tongues of material are more readily deflected from the axis of insertion of the flexible pipe (10) from the insertion point (9) towards the bend (11), around the bend (11) and down towards the lower end (13) of the host pipe (in this case the dipper tube (1)), as the leading or distal end of the flexible tube (10) engages with the inner surface of the extrados of bend (11), thereby facilitating negotiation of bend (11) by the subsequent length of uncut flexible tube (10) as further lengths of the flexible tube are urged from the insertion point (9) and towards the bend (11).

[0068] To allow for the possible partial or complete obstruction of the fluid passageway of the flexible tube (1) by the distortion and or collapse of the tongues of material (21) and/or (22) under adverse insertion conditions, holes (23) of an appropriate number and size may be drilled through the flexible tube (10) near the leading or distal end at an appropriate distance back from the tongues of material (21) and (22) to provide a flow cross section of suitable area.

[0069] Alternatively or in addition, prior to insertion of the flexible tube (10), a strip of strong, flexible, low surface friction material (27) that is of sufficient length to extend from the insertion point (9), around the bend (11) and for a further distance along the host pipe (in this case the dipper tube (1)) towards its lower end (13), is fully inserted into the host pipe, and the trailing end secured to the inlet of the insertion point (9) at the crown. This is shown in Figure 8. As the flexible pipe (10) is inserted at the insertion point (9) and urged towards the pipe bend (11), the strip of flexible material (27) is positioned and secured so that it rides up over the crown of the flexible pipe (10) as it progresses towards the bend (11), and the forms a sliding surface between the inner surface of the extrados of the bend (11) and the flexible tube (10) as the flexible tube (10) negotiates the bend (11). The low friction strip (27) may be removed after the flexible tube (10) has negotiated the bend; alternatively, it can be left in place after suitable trimming to fit the liner pipe end termination.

[0070] A variety of materials may be used for the flexible, low surface friction strip (27) including nylon, PTFE and the like. As an alternative, multiple narrow strips of strong, flexible, low-friction material may be used instead of a single strip.

[0071] The insertion process then proceeds as follows.

[0072] The flexible strip (27) is positioned and secured at the mouth of the insertion point (9). The leading or distal end of the flexible tube is prepared to create the tongues of material (21) and (22), and the holes (23) are drilled. The leading or distal end of the prepared flexible tube (10) is then entered into the insertion point (9) and then urged towards and around the bend (11), using appropriate mechanical means. Once the flexible tube has been inserted to an appropriate point, the insertion process is halted. The flexible sleeve (14) is fitted over the flexible tube (10) and its leading or distal end is secured by the appropriate means (15) at a position along the length of the remaining flexible tube (10) outside the insertion point such that, when the leading or distal end of the flexible tube (10) reaches its desired position in the host pipe (in this case the dipper tube(1)), the point at which the flexible sleeve (14) is attached to the flexible tube (10) will be positioned at a desired point between the bend (11) and the lower end of the host pipe (13). At this stage, the cylindrical packer (17) is inserted into the flexible tube (10) so that its leading or distal end projects an appropriate distance beyond the leading or distal end/attachment point of the flexible sleeve (15).

[0073] The flexible sleeve (14) is then gathered up as close as possible to the point of attachment (15) to the flexible tube (10), so as to permit the pushing means to urge the flexible tube (10) into the insertion point (9) whilst minimising the free length of flexible tube (10) between these two points, to minimise the risk of the flexible tube suffering strut collapse failure. As the flexible tube (10)/flexible sleeve (14)/cylindrical packer (17) combination is urged forward, a convenient length of the previously-gathered flexible sleeve (14) is smoothed into a close-fitting profile around the flexible tube (10) and secured temporarily in place by appropriate means to ensure that the external profile of the flexible tube (10)/flexible sleeve (14) combination is as smooth and compact as possible as it enters the host pipe (in this case, the dipper tube (1)), and subsequently negotiates the bend (11). This process is repeated iteratively until the leading or distal end of the flexible tube (10) arrives at the desired position near or at the lower or distal end of the host pipe (in this case, the dipper tube (1))(13), whereupon the insertion process is halted.

[0074] The pushing means is then disconnected from the flexible tube (10), and the cylindrical packer (17) is withdrawn from the flexible tube (10). The flexible tube (10)/ flexible sleeve (14) combination is cut transversely at a convenient distance beyond the mouth of the insertion point (9). The temporary securing means holding the flexible sleeve (14) to the flexible tube (10) are then released so that the mouth of the flexible sleeve (14) can be deployed to its full circumference. A toroidal fitting (16), engineered to fit snugly over and form a pressure-tight seal onto the external surface of the flexible tube (10), and to fit snugly inside and form a pressure-tight seal onto the inner surface of the flexible sleeve (14) is then fitted over the free end of the flexible tube (10) and inside the flexible sleeve (14). The toroidal fitting (16) incorporates at least three axial ports (24) of suitable diameter disposed typically orthogonally around its circumference. These will normally be disposed so that one of the ports can be positioned over the crown of the flexible tube: this sealable port will act as a vent during grout injection, with the other two disposed at the springings of the flexible pipe (10) i.e. at the line of maximum horizontal dimension. One of the axial ports (24) is used as the port for injecting the grout material, and the remaining one is used to monitor the pressure inside the flexible sleeve (14) during the grouting operation. Alternatively, one of the ports may be disposed at the invert of the flexible tube (10) .i.e. at the lowest point on the line of maximum vertical dimension, to act as the point for grout injection, depending on the specific characteristics of the grout to be used.

[0075] Various methods may be used for effecting pressure-tight seals between the toroidal fitting (16) and the flexible tube (10) and flexible sleeve (14). In a particular embodiment of the toroidal fitting (16), hemispherical grooves (25) are machined circumferentially into both the internal and external diameters of the fitting. These are dimensioned suitably to accept circumferential compressible sealing elements (26) such as elastomeric 0-ring gaskets. Other known arrangements may also be used to effect these pressure-tight seals.

[0076] Once the toroidal fitting (16) has been secured in position and a pressure-tight seal has been effected to both the flexible tube (10) and the flexible sleeve (14), the temporary means for securing the flexible sleeve (14) to the flexible tube (10) can be released over the full length of the flexible sleeve (14) projecting outside the insertion point (9) into the host pipe (in this case, the dipper tube (1)). A pressure-tight connection from a grout injection means is made to an appropriate port (24), a suitable pressure gauge is connected to another suitable port (24), and finally a valve or similar component suitable for venting air from the flexible sleeve (14) during grouting, and also to act as witness point for the completion of filling of the flexible sleeve (14) with grout, signified by the discharge of grout, is fitted to a suitable one of the remaining ports.

[0077] A suitable fluid grout material is then injected into the flexible sleeve (14) via one of the ports (24) until the material can be seen discharging from the venting port (24). The venting port is then closed and further grout is injected whilst monitoring the grout pressure in the flexible sleeve by means of the pressure gauge connected to the third port. The pressure in the flexible sleeve is allowed to rise to a predetermined value governed by the pressure capability of the flexible sleeve (14), and of the end sealing arrangements at (15) and (16). The aim of this pressurisation is to remotely break the temporary strapping/ bands that secure the inaccessible length of flexible sleeve (14) inside the host pipe (in this case, the dipper tube (1)). As these bands burst, the pressure in the flexible sleeve (14) will decrease, which will be evidenced on the monitoring pressure gauge. The venting port is then re-opened and a further volume of grout is injected until material is witnessed discharging from the venting port, whereupon the venting port is again sealed and the flexible sleeve is again pressurised. This process is repeated iteratively until the flexible sleeve has fully expanded into close contact with the inside diameter of the host pipe (1) adjacent. The grout material is then allowed to cure.

[0078] Various alternatives may be considered for the grout material, and the choice will be governed by the particular application. In general the grout material needs to be fluid; be pressurisable; be able to stabilise/ set/ cure without significant shrinkage to form a stiff mass which fills the annular space between the host pipe (in this case, the dipper tube (1)) and the flexible tube (10); and to be stable in the environment to which it will be exposed in service. Suitable materials for this application include thermosetting resins, such as epoxy resins, polyurethanes and polyureas. Other suitable materials may equally be used.

[0079] Once the grout material has set to the required consistency, an appropriate length of the flexible sleeve (14) and the grout contained therein can be cut away from the section of flexible tube (10) projecting outside the insertion point (9). A suitable permanent pressure-tight connection can then be made to the flexible tube (10), and if required, also to the host pipe (in this case, the dipper tube (1) at the insertion point (9) using known methods. In Figure 11 the fitting 16 is left in place, its ports having been sealed by the cured grout. Alternatively, the fitting 16 could be removed and replaced with another longterm pressure-tight fitting.

[0080] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0081] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0082] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. System for lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end thereof, the system comprising: a flexible liner pipe having a proximal end and a distal end and whose outside diameter is less than the inside diameter of the host pipe; a sealing apparatus for sealing an outside surface of the liner pipe with respect to an inner surface of the host pipe, wherein the sealing apparatus comprises: a flexible sleeve attachable at a distal end thereof to form a pressure-tight seal on the outside surface of the liner pipe and capable of receiving a filler material which causes the sleeve to expand towards the inner surface of the host pipe; a packer insertable into the liner pipe and capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material, and a fitting capable of effecting a pressure-tight seal between the liner pipe and the flexible sleeve at a proximal end of the flexible sleeve.
2. System as claimed in claim 1 wherein the filler material is a curable grout, for example a thermosetting resin such as epoxy resin, polyurethane or polyurea.
3. System as claimed in claim 1 or claim 2 wherein the fitting includes an axially-extending port through which the filler material can be introduced into the sleeve and, preferably a second axially-extending port through which air can be vented and/or egress of filler material can be monitored or observed.
4. System as claimed in any of the preceding claims wherein the fitting includes a third axially-extending port to which a pressure gauge can be attached in order to monitor the pressure inside the sleeve.
5. System as claimed in any of the preceding claims wherein the flexible sleeve is generally cylindrical in its expanded configuration.
6. System as claimed in any of the preceding claims wherein the flexible sleeve in its expanded configuration has an external diameter substantially equal to the internal diameter of the host pipe.
7. System as claimed in any of the preceding claims wherein the flexible sleeve is attached at its distal end thereof to the outside surface of the liner pipe by means of fusion welding, adhesive bonding and/or mechanical strapping.
8. System as claimed in any of the preceding claims wherein the flexible sleeve comprises a flexible PVC sheet, preferably reinforced with polyester fibre.
9. System as claimed in any of the preceding claims wherein the fitting is generally toroidal in shape.
10. System as claimed in any of the preceding claims wherein the liner pipe is a flexible corrugated pipe.
11. System as claimed in any of the preceding claims wherein the distal end of the liner pipe includes one or more slots extending axially from the distal end which allow the diameter of the distal end of the liner pipe to be reduced by compression.
12. System as claimed in claim 11 wherein the slots are generally triangular, forming compressible tongues at the distal end of the liner pipe.
13. System as claimed in any of the preceding claims wherein one or more radial holes are provided in the liner pipe at or near the distal end thereof, allowing fluid communication with the interior of the liner pipe.
14. System as claimed in any of the preceding claims further comprising a flexible strip of low friction material which can be placed intermediate the host pipe and liner pipe to facilitate pushing of the liner pipe into the host pipe.
15. System as claimed in claim 14 wherein the flexible strip includes a flange at its proximal end which can be removeably attached to the proximal end of the host pipe.
16. System as claimed in claim 14 or claim 15 wherein the flexible strip is sufficiently long to extend from the proximal end of the host pipe and past a first bend in the host pipe.
17. System as claimed in any of the preceding claims wherein the packer is generally cylindrical and contains a filler which is stiff in the radial direction and sufficiently flexible in the axial direction to conform to the shape of the liner pipe in which it is located.
18. System as claimed in claim 17 wherein the packer comprises a length of flexible, axially-and circumferentially-reinforced high pressure hose.
19. System as claimed in claim 17 or claim 18 wherein the filler is a solid fine grade particulate material, for example sand.
20. System as claimed in any of claims 17-19 wherein the outside diameter of the packer is substantially equal to the inside diameter of the liner pipe.
21. System as claimed in any of claims 17-19 wherein the outside diameter of the packer is less than the inside diameter of the liner pipe and the space therebetween is filled with a sheath of flexible material.
22. System for lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end thereof, substantially as described herein with reference to and as illustrated in any appropriate combination of Figures 4-11.
23. Method of lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end using a system as claimed in any of the preceding claims.
24. Method of lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end, the method comprising the steps of: providing a flexible liner pipe having a proximal end and a distal end and whose outside diameter is less than the inside diameter of the host pipe; inserting the distal end of the liner pipe into the proximal end of the host pipe and urging the liner pipe partially into the host pipe; attaching a distal end of a flexible sleeve to an outside surface of the liner pipe so as to form a pressure-tight seal on the outside surface of the liner pipe; inserting a packer into the liner pipe which is capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during further insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material continuing to urge the liner pipe, now with flexible sleeve attached, into the host pipe, until the distal end of the liner pipe reaches a desired position with respect to the distal end of the host pipe; attaching a fitting capable of effecting a pressure-tight seal between the liner pipe and the flexible sleeve at the proximal end of the flexible sleeve; inserting a filler material into the sleeve through an axially-extending port in the fitting, which causes the sleeve to expand towards the inner surface of the host pipe; and sealing said port.
25. Method as claimed in claim 24 comprising an initial step of attaching a flexible strip of low friction material to the proximal end of the host pipe, the strip being intermediate the host pipe and liner pipe to facilitate pushing of the liner pipe into the host pipe.
26. Method as claimed in claim 24 or claim 25 wherein the host pipe includes at least one bend and the distal end of said flexible liner pipe is urged past said bend during said insertion step.
27. Method as claimed in claim 26 wherein the step of continuing to urge the liner pipe ends when the flexible sleeve is in the region of the bend in the host pipe.
28. Method as claimed in claim 26 or 27 wherein the packer is capable of maintaining the cross-sectional shape of the liner pipe against forces experienced during further insertion of the liner pipe into the host pipe and during expansion of the sleeve with filler material, particularly in the region of the bend in the host pipe.
29. Method as claimed in claim 28 wherein, if the outside diameter of the packer is less than the inside diameter of the liner pipe, the space therebetween is filled with a sheath of flexible material.
30. Method as claimed in claim 28 or claim 29 wherein the packer is capable of maintaining the cross sectional shape of the liner pipe by resisting the forces experienced by the liner pipe as it is urged into and through the first bend on the host pipe; and subsequently the radially-inward forces during the step of inserting a filler material into the sleeve.Method as claimed in any of claims 28-30 further comprising the step of cutting the proximal end of the packer and withdrawing the filler, for example by vacuum removal, and then removing the packer from the liner pipe.
31. Method as claimed in claim 29 or claim 31 when dependent on claim 29 further comprising the step of holding the sheath so that it does not move axially with respect to the liner pipe and then gripping and withdrawing the packer from the liner pipe.
32. Method as claimed in any of claims 24-32 further comprising the step of waiting for the filler material to cure after inserting the filler material.
33. Method as claimed in claim 33 wherein the step of sealing said port is performed by the cured filler material.
34. Method as claimed in claim 33 or claim 34 further comprising the step of, after the filler is cured, removing the fitting and a proximal portion of the sleeve and filler and attaching a long-term pressure-tight fitting to the liner pipe and, optionally, the host pipe.
35. Method of lining a host pipe with a liner pipe, in which access to the host pipe is only achieved from a proximal end, substantially as described herein with reference to any appropriate combination of Figures 3-11.