GB2304394A - Method of and apparatus for repairing a pipeline - Google Patents

Abstract

The apparatus includes a frame (1) and two pipeline clamp devices (9) mounted on the frame (1) in spaced apart relationship. The clamp devices (9) are adapted to clamp onto the pipeline (2) and the clamp devices (9) are rigidly interconnected by the frame (1). Associated cutters are used to slice the pipeline for removal of a damaged section and replacement by a spool (16) and end connectors (17) on respective carriers (13, 14). Clamps with buoyancy devices are situated on pipeline lengths either side of the frame (1) to support them during repair. The frame (1) alternatively has a pipe feeding funnel instead of a clamp for joining a layed pipe from a vessel to a cut pipe end. Two frames (1) can be used if a new length to be inserted is long.

Description

"Method of and Apparatus for Repairina a Pipeline'' The invention relates to a method of and apparatus for repairing a pipeline, and in particular, a subsea pipeline. The invention is especially useful with pipelines located in deep water.

Conventional pipeline repair systems which have been used to date require diver intervention to ensure that the pipeline is cut in the correct location and to install a repair spool piece of pipe in place of the damaged section of pipe. Even with the use of divers this operation has problems as if the pipeline is not cut in precisely the correct location, the repair spool piece of pipe will not fit in place of the damaged length of pipe as it will be either too long or too short. In addition, there is the added problem of tension in the pipeline which is released when the pipeline is cut. Hence, because of the movement of pipeline due to the release of tension when the first cut is made, the second cut may not be in the exact location in order to be able to fit the repair spool piece.

Furthermore, the use of divers to effect the repair is undesirable as there are always risks associated with the use of divers and the possibility of human error.

There is the additional problem that in certain circumstances it may not be possible to use divers because of the depths of water or because of particular local conditions.

In accordance with a first aspect of the present invention, apparatus for repairing a pipeline comprises a frame, two pipeline clamp devices mounted on the frame in spaced apart relationship, the clamp devices being adapted to clamp onto the pipeline, and the clamp devices being rigidly interconnected by the frame.

The invention has the advantage that by rigidly interconnecting the two clamp devices it is possible to rigidly interconnect the clamped portions of the pipeline via the frame. Hence, it is possible to cut the pipeline accurately between the two clamped portions.

Preferably, the apparatus also includes a pipe cutter mounted on the frame to cut the pipeline between the two clamps. Preferably, the apparatus may include two pipe cutters, one pipe cutter mounted on the frame adjacent each clamp device and between the clamp devices to cut out a section of the pipeline between the clamp devices.

Preferably, at least one of the clamp devices is movable in a direction perpendicular to the pipeline and is preferably movable substantially horizontally and substantially vertically with respect to the longitudinal axis of the pipeline.

In one example of the invention, one of the clamps may be incorporated into a guide device which is adapted to receive an end of a length of replacement pipe spool or an end of a length of pipeline from a pipeline laying vessel.

Typically, the apparatus also comprises a movable repair spool carrier which is movably mounted on the frame and is adapted to receive and hold a spool piece of pipe to fit between the cut ends of the pipeline adjacent the clamps.

Preferably, where a guide device is provided, the guide device is adapted to rotate about a substantially horizontal axis which is transverse to the longitudinal axis of the frame. Typically, the guide rotates from a position in which the axis of the guide is substantially vertical to a position in which the axis of the guide is substantially horizontal and substantially coincides with the axis of the pipeline being repaired in use. This permits an end of a pipe spool or pipeline from a pipeline lay barge or support vessel to be inserted into the guide at a substantially vertical angle and then rotated to the horizontal for connection to the cut end of the pipeline held by another clamp.

Preferably, adjacent ends of pipe spool or pipeline which are to be joined together are connected via mechanical connectors, such as a connector known as a Morgrip connector.

Preferably, the apparatus is used for repairing a subsea pipeline. However, the apparatus could equally be used for repairing other pipelines located in hazardous environments.

The apparatus may also include another frame comprising a third clamp device and a third pipe cutter. The other frame permits lengths of pipeline to be repaired which are longer than the distance between the first and second clamps.

In accordance with a second aspect of the invention, a method of supporting a portion of a pipeline on the seabed comprises attaching a buoyancy device to the portion of the pipeline to be supported and providing the buoyancy device with sufficient buoyancy so that the weight of the portion of the pipeline is at least partially supported by the buoyancy of the buoyancy device.

This aspect of the invention has the advantage that the weight of the portion of the pipeline is not supported on the seabed, for example by a jacking mechanism so that method can be used to support pipelines where the seabed is too soft to use the jack mechanism.

In accordance with a third aspect of the invention, a method of repairing a pipeline comprises providing a frame comprising two clamp devices mounted on the frame in spaced apart relationship, two pipe cutters mounted on the frame, one pipe cutter located adjacent each clamp device and located between the clamp devices to cut a pipeline held by the clamp devices, and a repair spool piece holder movably mounted on the frame to hold a repair pipe spool; placing the frame adjacent to the pipeline so that the section of the pipeline to be repaired is located between the clamps, bringing one of the clamp devices into engagement with the pipeline to clamp the pipeline on one side of the portion to be replaced, operating the pipe cutter adjacent to the first clamp to cut the pipe, bringing the second clamp device into engagement with the pipeline on the other side of the section of pipe to be replaced and operating the second pipe cutter to cut the pipeline adjacent to the second clamp device; moving the repair spool piece holder into position between the two cut ends of the pipeline and connecting the spool piece between the cut ends to replace the damaged section and repair the pipeline.

Examples of a method of and apparatus for repairing a pipeline in accordance with the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a repair frame being used to repair a short section of damaged pipe; Fig. 2 is a schematic view of a repair system in use utilising the repair frame shown in Fig. 1; Fig. 3 is a perspective view of a pipeline repair system being used to carry out a repair during laying of the pipeline and using a first modified version of the repair frame shown in Fig. 1; Fig. 4 shows re-initiation of pipelaying for the repair procedure shown in Fig. 3; and Fig. 5 shows an in service repair of a spool section of pipeline using the first modified version of the repair frame and a second modified version of the repair frame shown in Fig. 1.

Fig. 1 is a perspective view of a repair frame 1 being used to repair local damage in a pipeline 2. Repair frame 1 comprises two longitudinal support members 3 and two transverse support members 4 coupling the longitudinal members 3 together. Extending upwardly from each end of each longitudinal member 3, is an upright member 5. Each pair of upright members 5, on the same end of opposite longitudinal members 3, has a pipe claw module 6 movably mounted on them. The pipe claw modules 6 comprise a transverse member 7 located between the upright members 5 by means of slides 8 at each end of the transverse member 7. Movably mounted on the transverse member 7 is a clamp mounting 10 which supports a clamp 9.Hydraulic pistons 11 are provided to move the clamp mounting 10 and the clamp 9 along the transverse member 7 and hydraulic pistons 12 are provided to move the transverse member 7 up and down the upright members 5.

Mounted between the transverse members 4 is a spool and connector carrier 13 which can be moved transversely on the transverse members 4. The spool and connector carrier 13 includes two connector holders 14 and a spool holder 15. In use, the carrier 13 supports a repair spool piece of pipe 16 and two connectors 17, which are held on the carrier by the connector holders 14 and the spool holder 15. The two connectors 17 are typically mechanical/hydraulic connectors such as Morgrip connectors.

Also mounted on the repair frame 1 are two pipe cutters (not shown) which cut the pipe adjacent each clamp 9 prior to ends 18, 19 of the pipeline tube being raised by the pipe claw modules 6 to the position shown in Fig. 1.

Fig. 2 shows the general system for use of the repair frame 1 shown in Fig. 1. The general system includes four buoyancy modules 20 which are used to support the pipeline 2 on either side of the repair frame 1 and are attached to the pipeline by pipe clamps 28. A tool carrier 21 includes a dredging unit 22 and is used to transport the buoyancy modules 20 and pipe clamps 28 to the seabed. In addition, the tool carrier 21 also transports transponders 23 to the seabed for distribution by a remotely operated vehicle (ROV) 26.

The remotely operated vehicle (ROV) is operated remotely from a support vessel (not shown) in a conventional manner. The ROV engages with the ROV control panel 30 on the repair frame 1 to control operation of the pipe claw modules 6, pistons 11, 12, movement of the repair spool and connector carrier 13 and the pipe cutters. In addition, the ROV is also used to operate the Morgrip connectors 17 and the buoyancy modules 20 via control lines 24 which connect the buoyancy modules to the ROV control panel 30.

The tool carrier 21 is lowered from the surface and the support vessel via a cable 25 to a location on the seabed where buoyancy modules 20 and transponders 23 may be transported to their correct positions by the ROV 26 which is operated remotely from the surface via an umbilical 27.

In use, when a damaged section of pipeline is known to exist the pipeline is first surveyed using a survey vessel and/or ROV to locate damage in the pipeline 2.

The location suitable for repair is established by use of an ROV and pipe detector. After the area to be repaired is located, the tool carrier 21 with the buoyancy modules 20, the transponders 23 and the dredge unit 22 is lowered to the seabed. The transponders are then installed at appropriate locations on the seabed by use of the ROV 26 and the transponder network is calibrated.

Using the pipe detector on the ROV, the first cut position on the pipeline is established. From this position, the location of the first buoyancy module 20 is established and the dredging unit 22 on the tool carrier is used to excavate the burial material from above the pipeline in the vicinity of the first location for the buoyancy module 20. One of the pipe clamp tools 28 is then installed onto the pipe 2 at the first location.

The repair frame 1 is prepared on the support vessel for installation and installed as close as possible to the repair location using a surface based lift wire and the transponder array to aid location. A hold back wire is then established between the pipe clamp 28 which has been installed on the pipeline 2 and the repair frame 1 and the repair frame is then installed in the correct position by use of the hold back wire, which gives the correct distance from the pipe clamp to the repair frame 1 in order for the pipeline repair to be affected, and use of the ROV 26 and lift wire.

The ROV 26 is then docked on the ROV control panel 30 on the repair frame 1 to activate functions of the repair frame 1. If necessary, this includes anchoring the repair frame 1 to the seabed. This may be accomplished by the use of suction pads (not shown) located on the underside of the repair frame 1. After the ROV 26 has been docked on to the ROV control panel 30, control of the repair frame 1 can be affected from the surface via the umbilical 27 and the ROV 26 is used primarily as a connector and is effectively transparent to control signals from the support vessel to the repair frame 1.

Next the pipe claw modules 6 are lowered to excavate burial material from above the pipeline and then activated to clamp around the pipeline 2 at each end of the repair frame 1. The pipe cutter located adjacent, for example, the left hand clamp module 6 is activated first to make the first cut through the pipeline 2 and after the first cut has been made the other pipe cutter adjacent to the right hand claw module 6 is activated to effect a second cut through the pipeline. During cutting of the pipeline, the repair frame 1 is located on top of the pipeline 2. If the pipeline 2 has tension in it, the grip of the pipe claw module at the right hand end can be relaxed between the first and the second cut to help avoid too much tension being applied to the pipe claw module 6.If the right hand pipe claw module 6 grip is relaxed it is re-clamped around the pipeline 2 before performing the second cut. After the first and second cuts have been made, the pipe claw modules 6 retain the clamps 9 activated to ensure that there is no relative movement between the cut ends 18, 19.

After the first and second cuts have been made, pipe clamps 28 are installed at desired locations on either side of the repair frame using the ROV and dredging tool 22 as required to gain access to the pipeline 2.

The buoyancy modules 20 are then located on each of the pipe clamps 28 and activated to support the pipeline 2 on either side of the repair frame 1. Control cables 24 from the buoyancy modules are connected to the control panel on the repair frame 1. The ROV then redocks onto the control panel 30 and the pipeline 2 is lifted to the desired height using central control of the buoyancy modules and by lifting the clamps 9 by lifting the pipe claw modules 6 on the transverse members 5 to the position shown in Figs. 1 and 2. The connector and spool carrier 13 is then moved into position between the cut ends 18, 19 and the connectors 17 are activated to couple together the ends of the repair spool piece 16 to the cut ends 18, 19 of the pipeline 2 and the couplings are tested as per standard procedure.Free span corrections can then be carried out at either end of the repair frame as required, before recovering the ROV 26, pipe clamps 28, buoyancy modules 20, transponders 23 and the tool carrier 21 to the support vessel. The repair frame 1 is retained in position for support of the couplings 17 and also provides the possibility of future intervention if necessary.

Fig. 3 and Fig. 4 show how a first modified version of repair frame la may be used to effect repair of a pipeline 2a during pipe laying from a pipe lay vessel 35. In this situation, a section of the pipeline 2a has been laid by the lay vessel 35. Damage to the pipeline 2a has occurred during laying which has resulted in stoppage of the laying procedure. The damaged section 36 is indicated in phantom in Fig. 3.

The repair frame la is identical to the repair frame 1 shown in Figs. 1 and 2 with the exception that the right hand pipe claw module 6 is replaced with a pipe initiation module 37 which has the clamp 9 and clamp mounting 10 replaced with a guide funnel 38. The guide funnel 38 is pivotable on the transverse member 7 and the funnel guide 38 incorporates hydraulic rams (not shown).

In use, the damaged section 36 of the pipeline 2a is located and a position suitable for the first cut to remove the damaged section from the pipeline 2a is located using the ROV 26 and pipe detector, as described above for the repair system shown in Figs. 1 and 2. The tool carrier 21 is then deployed to the seabed and location of the first cut is determined by the ROV 26. The ROV 26 then locates a suitable location for the pipe clamp 28 which is installed by the ROV 26 on the pipeline 2a. The repair frame la is then prepared on the support vessel and lowered into the vicinity of the cut to be made on the pipeline 2a.

The repair frame la is moved to the exact location by using a hold back wire between pipe clamp 28 and repair frame la and using the lift wire of the repair frame la and the ROV 26.

The ROV 26 is then docked with the control panel 30 and functions on the repair frame la are activated in a similar manner to that described for the repair frame la in Figs. 1 and 2. If necessary, the repair frame is anchored by activating the suction pads on the underside of the repair frame la and the clamp module 6 is lowered and clamp 9 used to excavate any material away from the pipeline 2a and grip the pipeline 2a prior to the cutter mechanism adjacent to the pipe claw module 6 being activated to cut the pipeline 2a to remove the damaged section 36.

The pipe clamps 28 and buoyancy modules 20 are then installed as described above for Figs. 1 and 2 and control cables 24 connected to the control panel 30 and the pipeline is lifted to the desired height using the central control from the control panel 30 of the buoyancy modules and by raising pipe claw module 6 and clamp 9 on the repair frame la.

Next, as shown in Fig. 4, the lay barge 35 starts producing pipeline 2b and moves into position for vertical stabbing of the pipeline 2b into the guide funnel 38. The ROV 26 is used to establish a small size pull-in wire 39 to guide pipe initiation head 40 into funnel 38. The ROV 26 then docks with the control panel 30 on the repair frame la and activates power to operate a pulling winch to guide the pipe initiation head 40 into and through the funnel 38. After this has been done, the hydraulic rams in the funnel 38 are activated to hold the pipeline 2b in position and the pipe initiation head 40 may be removed. The pipe lay vessel 35 can then continue laying pipeline 2b.As the pipeline 2b is laid and the vessel 35 moves away from the location above the repair frame la, the funnel 38 gradually rotates from the vertical position to a horizontal position, shown in Fig. 4 in which the pipeline 2b lies along the seabed 50. Because the pipeline 2b must be laid air filled, the pipe laying of the pipeline 2b must be completed before the support vessel 35 can return to the repair frame la and complete the final tie-in using the spool piece 16 and connector 17 on the repair frame la. This can only occur after the pipe laying operation has been completed and the pipeline 2b and 2a has been flooded from the shore end.

In a further possible scenario, it is possible that the pipeline may be damaged over a length such that a short spool piece repair, as described above and shown in Figs. 1 and 2, is not possible and a longer pipe spool repair piece is required. An example of how the apparatus can be used in this situation is shown in Fig. 5, in which the repair frame la used in Figs. 3 and 4 with a pipe claw module 6 at one end and a pipe initiation module 37 at the other end is used with a second repair frame lb having a pipe claw module 6 at one end and a pipe receptacle module 41 at the other end. In this case, two Morgrip connectors 17 and a short repair spool piece 16 is located on repair frame la and a single Morgrip connector 17 is located on repair frame lb.

In use, the pipeline 2 is surveyed and the damaged section located as described above and suitable cut positions on both sides of the damaged length of pipeline are established.

At the left hand end of the damaged section, the tool carrier 21 is installed on the seabed and an array of transponders 23 is installed and calibrated as described above. The first cut position at the left hand end is established and a pipe clamp 28 is installed on pipeline section 2a as previously described. The repair frame la also installed as previously described. Pipe claw module 6 on repair frame la is then lowered to excavate and grip around the pipeline section 2a and the pipe cutter adjacent pipe claw module 6 is activated to cut through the pipe section 2a. Pipe clamps 28 and buoyancy modules 20 are then installed on the pipe section 2a as previously described.

The support vessel then re-locates to install repair frame lb at the other end of the damaged section and the operations for repair frame la are repeated with repair frame lb to cut the damaged section from the pipe section 2d. A repair spool section of pipe 42 is then guided into the guide funnel 38 in a similar operation as that described above in relation to Figs.

3 and 4. The spool 42 is then laid down into receptacle module 41 on repair frame lb and tie-in of the repair spool piece 42 to pipe sections 2a and 2d is accomplished by use of the Morgrip connector 17 on repair frame lb and the short spool piece 16 and the two Morgrip connectors on repair frame la. Free span corrections around the repair frames la and lb are then completed and the transponders 23, pipe clamps 28 and buoyancy modules 20 recovered to the tool carrier 21 which is then recovered to the surface and the ROV 26 is also recovered to the surface. Repair frames la and 1b are left on the seabed for support of the couplings 17 and also provide the possibility for future intervention if necessary.

The invention has the advantage that by providing a frame which connects the clamps which are used to clamp on to the pipeline, the precise position of the cuts through the pipeline is known which enables accurate repair using a spool piece and has the advantage that repair can be carried out without requiring diver intervention.

Improvements and modifications can be incorporated without departing from the scope of the invention.

Claims (13)

1. Apparatus for repairing a pipeline comprising a frame, two pipeline clamp devices mounted on the frame in spaced apart relationship, the clamp devices being adapted to clamp on to the pipeline, and the clamp devices being rigidly interconnected by the frame.

2. Apparatus according claim 1, the apparatus further comprising a pipe cutter mounted on the frame to cut a pipeline between the two clamp devices when the pipeline is clamped by the clamp devices.

3. Apparatus according to claim 2, the apparatus further comprising a second pipe cutter, each pipe cutter being mounted on the frame adjacent each clamp device and between the clamp devices to cut out a section of a pipeline between the clamp devices when the pipeline is clamped by the clamp devices.

4. Apparatus according to any of the preceding claims, wherein the clamp devices are each movable in substantially parallel planes with respect to the frame.

5. Apparatus according to claim 4, wherein the substantially parallel planes are substantially vertical.

6. Apparatus according to any of the preceding claims, wherein one of the clamp devices comprises a guide device which is adapted to receive an end of a length of replacement pipe spool or an end of a length of pipeline from a pipeline laying vessel.

7. Apparatus according to claim 6, wherein the guide device is adapted to rotate about a substantially horizontal axis which is transverse to the longitudinal axis of the frame.

8. Apparatus according to claim 7, wherein the horizontal axis is substantially perpendicular to the longitudinal axis of the frame.

9. Apparatus according to any of the preceding claims, wherein the apparatus further comprises a movable repair pipe spool carrier which is movably mounted on the frame and is adapted to receive and hold the spool piece of pipe to fit between cut ends of a pipeline held by the clamps.

10. A method of repairing a pipeline comprising providing a frame comprising two clamp devices mounted on the frame in spaced apart relationship, two pipe cutters mounted on the frame, one pipe cutter located adjacent each clamp device and located between the clamp devices to cut a pipeline held by the clamp devices, and a repair spool piece holder movably mounted on the frame to hold a repair pipe spool; placing the frame adjacent to the pipeline so that the section of the pipeline to be repaired is located between the clamps, bringing one of the clamp devices into engagement with the pipeline to clamp the pipeline on one side of the portion to be replaced, operating the pipe cutter adjacent to the first clamp to cut the pipe, bringing the second clamp device into engagement with the pipeline on the other side of the section of pipe to be replaced and operating the second pipe cutter to cut the pipeline adjacent to the second clamp device; moving the repair spool piece holder into position between the two cut ends of the pipeline and connecting the spool piece between the cut ends to replace the damaged section and repair the pipeline.

11. A method of supporting a portion of a pipeline on the seabed comprising attaching a buoyancy device to the portion of the pipeline to be supported and providing the buoyancy device with sufficient buoyancy so that the weight of the portion of the pipeline is at least partially supported by the buoyancy of the buoyancy device.

12. Apparatus for repairing a pipeline substantially as hereinbefore described with reference to the accompanying drawings.

13. A method of repairing a pipeline substantially as hereinbefore described with reference to the accompanying drawings.