GB2470997A

GB2470997A - A pipe plugging system

Info

Publication number: GB2470997A
Application number: GB201008919A
Authority: GB
Inventors: Andrew Shaw
Original assignee: International Pipeline Products Ltd
Current assignee: International Pipeline Products Ltd
Priority date: 2009-06-10
Filing date: 2010-05-28
Publication date: 2010-12-15
Anticipated expiration: 2030-05-28
Also published as: GB2470997B; GB0909970D0; GB201008919D0

Abstract

A pipe plugging system comprises a plug which is actuable between a deactivated state and an activated state for selectively plugging pipe, to a kit to be assembled to form a pipe plugging system and comprising a plurality of such plugs, and to a method of plugging a pipe utilising such a plug. The pipe plugging system comprises a plug housing (12) adapted to be coupled to a pipe (14) to be plugged and which contains a plug (16) that is actuable between a deactivated state and an activated state for selectively plugging the pipe. The pipe plugging system also comprises an actuating mechanism (18) for advancing the plug from the housing and into the pipe to locate the plug within the pipe, and for retracting the plug from the pipe.

Description

PIPE PLUGGING SYSTEM AND METHOD

The present invention relates to a pipe plugging system. In particular, but not exclusively, the present invention relates to a pipe plugging system comprising a plug which is actuable between a deactivated state and an activated state for selectively plugging a pipe. The present invention also relates to a kit to be assembled to form a pipe plugging system and comprising a plurality of plugs, each of which are actuable between deactivated and activated states for selectively plugging a pipe. The present invention also relates to a method of plugging a pipe utilising a plug which is actuable between a deactivated state and an activated state.

Pipelines are utilised in many industries for the transportation of fluids. For example, in the oil and gas exploration and production industry, pipelines are used to transport well fluids (comprising oil and gas) from offshore fields to production facilities located onshore, as well as to transport well fluids and processed fluids between separate locations onshore. Pipelines are also widely used in the utilities industry to transport combustible gasses and water for both domestic and industrial uses. Complex networks of pipelines and associated pressure control equipment are required in order to safely store and transport these fluids. In particular and in the case of combustible fluids such as oil and gas, stringent safety regulations require that suitable pressure control equipment be provided in order to control and, if required, shut off the flow of fluid through a pipeline.

Typically, a number of valves are provided in a pipeline which can be selectively actuated to control flow of fluid through the pipeline. In the event that one of these valves requires to be removed for replacement and/or for maintenance activities to be conducted, this presents certain challenges as the valves provide a primary barrier to the flow of fluid along the pipeline. For example, a gas transportation network may comprise a gas storage tank with a number of pipelines extending from the storage tank to transport gas to a desired location. Each of the pipelines will include a primary flow control valve for controlling the flow of gas along the pipeline. In the event that the primary valve requires to be removed or to undergo maintenance, it is currently necessary to bleed off pressure behind the valve so that it can be removed. This requires that the gas in the storage tank be removed so that the necessary work can be carried out. This is time consuming and costly as it necessitates movement of the gas to a suitable alternative storage tank.

It is amongst the objects of embodiments of the present invention to obviate or mitigate at least one of the foregoing disadvantages.

According to a first aspect of the present invention, there is provided a pipe plugging system comprising: a plug housing adapted to be coupled to a pipe to be plugged and which contains a plug that is actuable between a deactivated state and an activated state for selectively plugging the pipe; and an actuating mechanism for advancing the plug from the housing and into the pipe to locate the plug within the pipe.

Providing a pipe plugging system comprising a plug housing containing a plug, and an actuating mechanism for advancing the plug from the housing and into the pipe, facilitates any maintenance activities which are to be carried out on the pipe. In particular, the plugging system of the present invention may provide the ability for work involving removal and/or maintenance of a valve of the pipe without requiring the pipe to be evacuated of fluid (which may typically comprise a combustible gas). This is because the plugging system may facilitate positioning of the plug within the pipe in a location where the plug seals the pipe and enables removal and/or maintenance of the valve. Following completion of the work, the plug can be removed from the pipe and the pipe re-opened.

The actuating mechanism may also be for withdrawing the plug from the pipe back into the housing. The actuating mechanism may be releasably coupled/couplable to, or releasably connected/connectable to, the plug, which may facilitate release of the actuating mechanism from the plug following location of the plug within the pipe. The actuating mechanism may control actuation of the plug between the deactivated and activated states.

Accordingly, the actuating mechanism may serve for controlling actuation of the plug from the deactivated state to the activated state (following location within the pipe), and actuation of the plug from the activated state to the deactivated state (for subsequent withdrawal of the plug from the pipe). The actuating mechanism may be for advancing the plug from the housing into the pipe and actuating the plug from the deactivated state to the activated state; and subsequently actuating the plug from the activated state to the deactivated state and withdrawing the plug from the pipe.

The actuating mechanism may comprise an insertion member which may be a rod, tubular member or the like, and the insertion member may be releasably coupled to the plug. The insertion member may be moveable relative to the housing for advancing the plug from the housing into the pipe, and may be for withdrawing the plug from the pipe back into the housing. The actuating mechanism may comprise a drive arrangement coupled to the insertion member and which may control movement of the insertion member relative to the housing. The drive arrangement may be hydraulically operated and may comprise one or more piston/cylinder device for controlling movement of the insertion member. The insertion member may be threadably coupled to the plug. This may facilitate release of the insertion member from the plug by rotation of the insertion member relative to the plug (following location of the plug within the pipe), and which may also facilitate reconnection of the insertion member to the plug (for deactivation and withdrawal of the plug from the pipe).

The housing may be adapted to be coupled to an end of the pipe, and may comprise an interface member for coupling the housing to the pipe. The interface member may be a flange shaped to cooperate with a corresponding flange on the end of the pipe. The housing may be adapted to be releasably coupled to the pipe, which may facilitate removal of the housing from the pipe following location of the plug within the pipe and actuation of the plug to the activated state. The actuating mechanism may be coupled to the housing such that the housing serves for mounting the actuating mechanism relative to the pipe.

The system may comprise one or more seals for sealing the system to, or relative to, the pipe. This may facilitate testing of a seal provided by the plug following actuation to the activated state and prior to removal of the housing from the pipe. The system may comprise a seal for sealing the housing relative to the pipe and, where the actuating mechanism comprises an insertion member, a seal for sealing the insertion member relative to the housing. The seal which seals the insertion member relative to the housing may permit/facilitate movement of the insertion member relative to the housing whilst maintaining a seal.

The plug may be radially expandable into sealing abutment with an internal surface of the pipe on actuation of the plug to the activated state. The plug may comprise at least one annular sealing device which is radially expandable into sealing abutment with the internal surface of the pipe. The plug, in particular said at least one annular sealing device, may be inflatable and may be hydraulically actuated. The actuating mechanism may comprise a hydraulic control line associated with the plug, and which may be associated with said at least one annular sealing device, for selectively actuating the plug. The hydraulic control line may be releasably coupled/couplable to the plug, which may facilitate release of the housing from the pipe following location of the plug within the pipe and actuation of the plug. The plug may comprise a valve for containing pressure applied to the plug to thereby maintain the plug in the activated state. Where the plug comprises a plurality of annular sealing devices, at least one of the sealing devices may comprise a gripping surface or gripping arrangement, and/or a portion of a surface of at least one sealing device may define a gripping surface/arrangement, for gripping the internal surface of the pipe to thereby resist movement of the plug under the applied pressure of fluid within the pipe.

The housing may be generally tubular, and may be a generally cylindrical tube. The housing may comprise a drain for draining fluid from the housing following advancement of the plug into the pipe and actuation of the plug to the activated state. The drain may comprise an outlet and a drain control valve.

The system may comprise a plurality of plugs, each of which may be independently actuable. This may facilitate location of plugs at spaced intervals along a length of the pipe which may, for example, facilitate an inspection, maintenance or test procedure to be conducted on a portion of the pipe located between a pair of plugs (such as a pressure test of the integrity of a weld located at a point along a length of the pipe between the pair of plugs).

According to a second aspect of the present invention, there is provided a kit to be assembled to form a pipe plugging system, the kit comprising: a plug housing; and a plurality of plugs, each plug having at least one dimension which is different to a corresponding dimension of at least one other plug; wherein the plug housing is adapted to be coupled to a pipe to be plugged and to contain a selected one of the plurality of plugs, which plug is actuable between a deactivated state and an activated state for selectively plugging the pipe; and wherein the kit comprises an actuating mechanism for advancing the selected plug from the housing and into the pipe to locate the plug within the pipe.

The kit of the second aspect of the present invention may provide a pipe plugging system in which a common housing and actuating mechanism may be utilised with a plurality of different plugs. This may facilitate use of the system with a plurality of different pipes, in particular, with pipes having respective different internal diameters, external diameters and/or wall thicknesses. The at least one dimension of each plug which is different to a corresponding dimension of at least one other plug may be an external diameter, and which may be an external diameter in one or both of deactivated and activated states of the plug.

Further features of the housing, the plug(s) and the actuating mechanism of the pipe plugging system of the kit of the second aspect of the present invention are defined above with respect to the first aspect of the invention.

According to a third aspect of the present invention, there is provided a method of plugging a pipe, the method comprising the steps of: coupling a plug housing of a pipe plugging system to a pipe to be plugged; advancing a plug contained within the housing from the housing and into the pipe using an actuating mechanism of the system, to thereby locate the plug within the pipe; and actuating the plug from a deactivated state to an activated state to plug the pipe.

The method may comprise the further step of conducting a desired maintenance procedure on the pipe, which step may follow actuation of the plug to the activated state. The method may therefore be a method of conducting a maintenance procedure on a pipe comprising plugging the pipe following the method of the third aspect of the present invention.

Following location of the plug within the pipe and actuation of the plug to the activated state, the method may comprise the step of actuating the plug from the activated state back to the deactivated state. The method may comprise withdrawing the plug from the pipe following actuation back to the deactivated state, and may comprise withdrawing the plug back into the housing.

The method may comprise releasably coupling the actuating mechanism to the plug and, following location of the plug within the pipe and actuation of the plug to the activated state, releasing the actuating mechanism from the plug. Following release, the actuating mechanism may be removed from the pipe. The method may comprise releasing the housing from the pipe following location of the plug within the pipe and actuation of the plug to the activated state. The method may comprise conducting suitable testing including pressure testing to ensure secure location of the plug within the pipe prior to release of the actuating mechanism and/or the housing.

The plug may be hydraulically actuated and thus may be actuated to the activated state by application of fluid pressure. The method may comprise maintaining the plug in the activated state, which may be achieved by containing the applied fluid pressure such as through a valve or valve arrangement of the plug. This may facilitate release of the housing from the pipe and/or the actuating mechanism from the plug.

The method may comprise coupling the plug housing to an end of the pipe, and may comprise coupling the housing to a valve assembly provided on or as part of the pipe. In this fashion, following location of the plug within the pipe and activation of the plug, the valve may be removed and/or maintenance may be conducted on the valve in situ.

The method may comprise advancing the plug into the pipe and locating the plug within the pipe at a position where the plug is spaced along a length of the pipe from the end thereof. The method may comprise isolating a portion of the length of the pipe from fluid contained within the pipe, which may therefore provide for pressure isolation of said portion of the pipe. The portion of the pipe may be that portion which, following location of the plug within the pipe and actuation of the plug, is located between the end of the pipe and an end of the plug. The end of the plug may be an end which is, in use, proximal to the end of the pipe. The method may comprise advancing the plug along the pipe to a position beyond a valve or valve assembly of the pipe, such that the valve is located between the end of the pipe and an end of the plug. This may facilitate maintenance work to be carried out on the valve and/or replacement of the valve.

The method may comprise locating a plurality of independently actuable plugs at spaced intervals along a length of the pipe. This may, for example, facilitate an inspection, maintenance or test procedure to be conducted on a portion of the pipe located between a pair of plugs (such as a pressure test of the integrity of a weld located at a point along a length of the pipe between the pair of plugs).

Reference is made herein to a pipe plugging system, to a kit to be assembled to form a pipe plugging system, and to a method of plugging a pipe. It will be understood that the pipe may be of a type found in a wide range of different industries including the oil and gas exploration and production industry and the utilities industry, and in particular may be a pipe of a type suitable for transporting fluids such as oil, gas, water and/or mixtures thereof. The pipe may be a pipeline comprising a number of pipe sections coupled together end to end (for example by welding or mechanically using flanges) and/or a continuous length of pipe such as may be supplied on a reel. The plugging system/method may be applied to pipes of materials including metals and metal alloys, plastics materials, composite materials and/or of cement based materials such as concrete.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a pipe plugging system in accordance with an embodiment of the present invention, parts of the pipe plugging system shown in cross-section, the pipe plugging system shown connected to a pipe to be plugged prior to location of a plug of the system within the pipe; Figure 2 is a cross-sectional side view of part of the pipe plugging system shown in Figure I taken in the direction A-A of Figure 1; and Figure 3 is an end view of the pipe plugging system shown in Figure 1.

Turning firstly to Figure 1, there is shown a pipe plugging system in accordance with an embodiment of the present invention, the pipe plugging system indicated generally by reference numeral 10. The system 10 generally comprises a plug housing 12 which is adapted to be coupled to a pipe 14 which is to be plugged, and which contains a plug 16.

The plug 16 is actuable between a deactivated state and an activated state for selectively plugging the pipe 14, and is shown in Figure 1 in the deactivated state. The system 10 also comprises an actuating mechanism, indicated generally by reference numeral 18, which serves for advancing the plug 16 from the housing 12 and into the pipe 14, to locate the plug within the pipe. The system 10 is also shown in Figure 2, which is a cross-sectional side view of part of the plugging system, taken in the direction of the arrows A-A of Figure 1, and in the end view (viewing in the direction of the arrow B in Figure 1) of Figure 3. Tn Figures 2 and 3, the pipe 14 has been removed, for ease of illustration.

As noted above, the plug 16 is located within the pipe 14 using the actuating mechanism 18. The plug 16 is then actuated from the deactivated state to the activated state and, following appropriate testing to ensure that the plug 16 is securely located within the pipe 14 (and thus plugging the pipe and containing the fluid within the pipe), the actuating mechanism 18 is released from the plug 16 and retracted. The housing 12 is then released from the pipe 14, and a maintenance or other procedure may be carried out.

In the illustrated example, a valve indicated generally by reference numeral 20 is to be released from the pipe 14 and replaced. Following location of the plug 16 in the pipe 14, the valve 20 may be released and a replacement valve (not shown) connected to the pipe.

The plug housing 12 is then reconnected to the pipe 14, the actuating mechanism 18 advanced into the pipe 14 and reconnected to the plug 16, and the plug is then actuated back to the deactivated state and withdrawn from the pipe 14. The new valve can then be closed, the plug housing 12 released from the pipe 14, and normal operations may then resume.

The pipe plugging system 10 and its method of operation will now be described in more detail.

The pipe 14 is of a conventional type, and may be a pipeline of the type utilised in the oil and gas exploration and production industry. The pipe may be utilised for transporting well fluids from an offshore well to a land based production facility, or indeed for transporting well fluids or processed oil and/or gas overland or to some other location. The pipe 14 may equally be a pipeline for use in the utilities industry such as for the transportation of gas or water for domestic or commercial use. It will be understood that the pipe 14 will typically be made up of a series of pipe sections which are coupled together end-to-end, or much larger lengths of pipe which are supplied in reeled form.

Suitable materials for the pipe 14 include metals/metal alloys, plastics, composite materials and cement based materials such as concrete.

The pipe 14 will typically carry a number of valves such as the valve 20 at spaced locations along the length of the pipe. In the illustrated example, the valve 20 is a primary valve controlling flow of fluid along the pipe 14. In the event of routine maintenance requiring to be conducted on the valve 20, or indeed replacement in the event of a mechanical or other failure, it is necessary either to remove the valve 20 or to carry out maintenance procedures in situ. The pipe plugging system 10 of the present invention facilitates such procedures, as will now be described.

The plug housing 12 is shaped for connection to the pipe 14, and comprises a generally cylindrical tubular body 22 which carries a pipe mating flange 24 at one end thereof. The S flange 24 serves for connecting the housing 12 to a corresponding flange 26 of the valve 20 using suitable nut and bolt assemblies (not shown). It will be understood that the valve 20 may be any one of a number of different types of valves including ball valves, gate valves and butterfly valves, the associated valve gear (not shown) located within a main body 28 of the valve 20.

The plug 16 is dimensioned such that, in the deactivated state, an annular space 30 is provided between the plug and an internal surface 32 of the body 22. In this way, when in the deactivated state, the plug 16 may pass freely along an internal bore 34 of the body 22.

The plug housing 12 includes a further flange 36 connected to an opposite end of the body 22 from the flange 24, and which serves for connecting the housing 12 to the actuating mechanism 18. To this end, the actuating mechanism 18 includes a housing mating flange 38, which is connected to the further flange 36 of the housing via a number nut and bolt assemblies, two of which are shown and given the reference numeral 40. As will be described in more detail below, the housing mating flange 38 seals the housing 12 and provides a passage for hydraulic control lines 42 and 44 which serve for actuating the plug 16.

The actuating mechanism 18 also comprises a pair of piston/cylinder devices, indicated generally by reference numeral 46, which serve for advancing the plug 16 into the pipe 14 and for withdrawing the plug. Each piston/cylinder device 46 comprises a cylinder 48 connected to the flange 36, and a piston 50. Movement of the pistons 50 within the cylinder 48 is controlled in a conventional fashion via a hydraulic pump (not shown) connected to the cylinders via control lines 52 and 54. The actuating mechanism 18 also comprises an insertion member in the form of a rod 54, which is threadably coupled to the plug 16. Each piston 50 is secured to a cross-beam 56, and the insertion rod 54 is also secured to the beam 56 using a lock nut 58. In this fashion, when the pistons 50 are actuated and translated relative to the cylinders 48, the pistons carry the cross-beam 56, and thus the insertion rod 54. Accordingly, actuation of the pistons 50 translates the plug 16 within the housing 12, and thus advances the plug into the pipe 14 or withdraws the plug from the pipe.

The plug 16 is of a type commercially available from the present applicant, such as the NP inflatable tyre plug or the HP pipe plug. The plug 16 includes a pair of inflatable tyres 60, 62 whose actuation is controlled by the actuating mechanism 18. The hydraulic control line 42 extends between an inflation pump (not shown) and the tyre 60, whilst the control line 44 extends between the pump and the tyre 62. Following location of the plug 16 -Il-within the pipe 14, valve assemblies 68 and 70 associated with the respective control lines 42 and 44 are operated to inflate the tyres 60 and 62. It will be understood that sufficient play is provided in the control lines 42 and 44 to permit advancement of the plug 16 into the pipe 14 whilst maintaining hydraulic connection. In a conventional fashion, seals (not shown) are provided at the interfaces between the valve flange 26 and the pipe mating flange 24, and between the further flange 36 and the housing mating flange 38. This provides for pressure integrity within the housing 12. Additionally, suitable 0-ring seals 72 are provided in the housing mating flange 38 for sealing relative to the insertion rod 54.

Operation of the pipe plugging system 10 is generally as follows. The system 10 is brought into the vicinity of the valve 20 which is to be replaced. The valve 20 is, at this stage, closed thereby shutting-off flow of fluid along the pipe 14 and containing pressurised fluid within the pipe. The system 10 is supported using hoisting equipment (not shown) connected to lifting eyes 74 on the housing body 22, and the flange 24 is then introduced to the valve flange 26 and secured using the nut and bolt assemblies, which are torqued-up as required to ensure correct sealing.

The valve 20 is then partially opened and the pressure upstream and downstream of the plug 16 monitored until equilibrium is achieved. Once the pressure has stabilised, the valve 20 is fully opened. The hydraulic pump controlling the pistons 50 is then operated, controlled through hydraulic circuits 78 and 80, to supply fluid to the cylinders 48 through the lines 54 and to bleed fluid from the cylinders through the lines 52. This translates the insertion rod 54 and advances the plug 16 out of the body 22 and into the pipe 14. The plug 16 is advanced by continued application of fluid pressure until such time as a stop 76 on the rod 54 comes in to contact with the housing mating flange 38. The plug 16 has then been located further down the pipe 14 from the valve 20. During insertion of the plug 16, the plug control lines 42 and 44 are shut off using the valve assemblies 68 and 70, to maintain the plug in the deactivated state. The hydraulic circuits 78 and 80 on the control lines 52 and 54 are then isolated to maintain the plug 16 in position within the pipe 14.

The hydraulic control line 42 is then energised to inflate the tyre 60 and isolated, and the line 44 then energised to inflate the tyre 62 and also isolated. The tyre inflation pressure is monitored for subsequent fluctuation. If required, these steps are repeated to apply further inflation pressure to the tyres. A drain plug 82 on the body 22 is then removed, and a valve 84 operated to drain fluid from the internal bore 34. The pressure upstream of the plug 16 is then checked for stability, indicating that the plug 16 is securely located within the pipe 14 and holding back the pressurised fluid in the pipe. As a further check, the hydraulic circuit 78 is operated to release the pistons 50 and, in the event of any movement of the plug 16 being detected (causing a corresponding movement of the pistons), further pressure can be applied to the tyres 60 and 62.

The lock nut 58 is then released and the insertion rod 54 rotated anti-clockwise until it disengages from the plug 16. The rod 54 is then partially retracted (manually or controlled by hydraulic circuits 78, 80) and the plug housing 12 may then be safely released from the valve 20 to provide access to the valve for maintenance/removal. It will be understood, that if desired, the housing 12 carrying the valve 20 may be released from a terminal pipe section 86 for subsequent replacement. It will also be understood that, during valve replacement, the tyre hydraulic control lines 42 and 44 must be fitted through the replacement valve and that care must be taken not to damage these control lines during this procedure.

Following maintenance on the valve 20, or replacement of the valve, the plug 16 may be removed from the pipe 14 for subsequent reopening of flow through the pipe. To achieve this, the above steps are performed in reverse. In more detail however, the procedure is as follows.

The plugging system 10 is positioned so that the housing 12 is near to the valve flange 26 and the tyre hydraulic inflation lines 42 and 44 reconnected. The flanges 24, 26 are then mated and secured using the nut and bolt assemblies. The insertion rod 54 is (typically manually) reconnected to the plug 16 and secured by the locknut 58. The drain plug 82 is then reconnected. The tyres 60 and 62 are then deflated to return the plug 16 to the deactivated state. The hydraulic energising circuits 78, 80 are then operated to supply fluid through hydraulic line 52 and bleed fluid from line 54, thereby translating the pistons 50 back towards the Figure 1 position. This withdraws the plug 16 from the pipe 14 and back into the body 22 of the plug housing 12. The valve 20 is then closed, fluid drained from the body 22 in the fashion described above and the system 10 released from the valve.

The pipe plugging system 10 may be provided in kit forn, and the kit may comprise a plurality of plugs such as the plug 16, each plug having at least one dimension which is different to a corresponding dimension of at least one other plug. Thus a kit may be provided in which a common housing and actuating mechanism may be utilised with a plurality of different plugs. This may facilitate use of the system 10 with a plurality of different pipes such as the pipe 14, in particular, with pipes having respective different internal diameters, external diameters and/or wall thicknesses. The at least one dimension of each plug which is different to a corresponding dimension of at least one other plug may be an external diameter, and may be an external diameter of the plug in one or both of deactivated and activated states of the plug.

Various modifications may be made to be foregoing without departing from the spirit and scope of the present invention.

For example, the system may comprise a plurality of plugs, each of which may be independently actuable. This may facilitate location of plugs at spaced intervals along a length of the pipe which may, for example, facilitate an inspection, maintenance or test procedure to be conducted on a portion of the pipe located between a pair of plugs (such as a pressure test of the integrity of a weld located at a point along a length of the pipe between the pair of plugs).

Claims

CLAIMS1. A pipe plugging system comprising: a plug housing adapted to be coupled to a pipe to be plugged and which contains a plug that is actuable between a deactivated state and an activated state for selectively plugging the pipe; and an actuating mechanism for advancing the plug from the housing and into the pipe to locate the plug within the pipe.
2. A system as claimed in claim 1, in which the actuating mechanism is also for withdrawing the plug from the pipe back into the housing.
3. A system as claimed in either of claims 1 or 2, wherein the actuating mechanism is releasably couplable to the plug, to facilitate release of the actuating mechanism from the plug following location of the plug within the pipe.
4. A system as claimed in any preceding claim, wherein the actuating mechanism comprises an insertion member releasably coupled to the plug, the insertion member being moveable relative to the housing for advancing the plug from the housing into the pipe and for withdrawing the plug from the pipe back into the housing.
5. A system as claimed in claim 4, wherein the actuating mechanism comprises a drive arrangement coupled to the insertion member and which controls movement of the insertion member relative to the housing.
6. A system as claimed in any preceding claim, wherein the housing comprises an interface member for releasably coupling the housing to the pipe.
7. A system as claimed in any preceding claim, wherein the plug comprises at least one inflatable annular sealing device which is radially expandable into sealing abutment with an internal surface of the pipe on actuation of the plug to the activated state, and wherein the actuating mechanism comprises a fluid control line associated with said at least one annular sealing device for selectively actuating the plug, the control line releasably couplable to the plug to facilitate release of the housing from the pipe following location of the plug within the pipe and actuation of the plug.
8. A system as claimed in any preceding claim, comprising a plurality of plugs, each of which is independently actuable.
9. A kit to be assembled to form a pipe plugging system, the kit comprising: a plug housing; and a plurality of plugs, each plug having at least one dimension which is different to a corresponding dimension of at least one other plug; wherein the plug housing is adapted to be coupled to a pipe to be plugged and to contain a selected one of the plurality of plugs, which plug is actuable between a deactivated state and an activated state for selectively plugging the pipe; and wherein the kit comprises an actuating mechanism for advancing the selected plug from the housing and into the pipe to locate the plug within the pipe.
10. A kit as claimed in claim 9, wherein the at least one dimension of each plug which is different to a corresponding dimension of at least one other plug is an external diameter.
11. A method of plugging a pipe, the method comprising the steps of: coupling a plug housing of a pipe plugging system to a pipe to be plugged; advancing a plug contained within the housing from the housing and into the pipe using an actuating mechanism of the system, to thereby locate the plug within the pipe; and actuating the plug from a deactivated state to an activated state to plug the pipe.
12. A method as claimed in claim 11, comprising the further step of actuating the plug from the activated state back to the deactivated state and subsequently withdrawing the plug from the pipe back into the housing.
13. A method as claimed in either of claims 11 or 12, comprising releasably coupling the actuating mechanism to the plug and, following location of the plug within the pipe and actuation of the plug to the activated state, releasing the actuating mechanism from the plug, removing the actuating mechanism from the pipe and then releasing the housing from the pipe.
14. A method as claimed in claim 13, comprising re-coupling the housing to the pipe, reinserting the actuating mechanism into the pipe and re-coupling the actuating mechanism to the plug, actuating the plug from the activated state back to the deactivated state and removing the plug from the pipe.
15. A method as claimed in any one of claims 11 to 14, comprising actuating the plug to the activated state by application of fluid pressure, maintaining the plug in the activated state by containing the applied fluid pressure using a valve, and then releasing the housing from the pipe.
16. A method as claimed in any one of claims 11 to 15, comprising coupling the plug housing to an end of the pipe and, following location of the plug within the pipe and activation of the plug, removing a valve assembly on the pipe and/or conducting maintenance on the valve assembly.
17. A method as claimed in any one of claims 11 to 16, comprising advancing the plug along the pipe to a position beyond a valve assembly of the pipe, such that the valve assembly is located between the end of the pipe and an end of the plug.
18. A method as claimed in any one of claims 11 to 17, comprising locating a plurality of independently actuable plugs at spaced intervals along a length of the pipe.