GB2529908A

GB2529908A - Apparatus and method for localised surface cleaning

Info

Publication number: GB2529908A
Application number: GB1417088.0A
Authority: GB
Inventors: Quentin Lhussier; Robert Cowie
Original assignee: Proserv UK Ltd
Current assignee: Proserv UK Ltd
Priority date: 2014-08-25
Filing date: 2014-09-26
Publication date: 2016-03-09
Also published as: GB201417088D0; GB2529908A8

Abstract

An apparatus for localized cleaning of a surface, particularly a subsea surface such as a hull of a ship, riser, pipeline or the steel jacket of a platform comprises a body 4, at least one jet or nozzle 16 mounted on the body 4 for directing a high pressure stream of fluid at the surface and a securing device such as a plurality of magnets 18 is mounted on the body 4 for attaching the body 4 to the surface. The apparatus further comprises a base member (9, fig 2) extendable from and retractable within the body 4 and means for moving the base (9, fig 2) with respect to the body 4 from a first position in which the body 4 is in contact with the surface to a second position in which the body 4 is spaced from the surface such that the position of the body 4 can be finely adjusted relative to the surface before the securing device 18 is engaged with the surface to firmly hold the body 4 on the surface. The arrangement allows for fine positioning and soft landing of the apparatus.

Description

APPARATUS AND METHOD FOR LOCALISED SURFACE CLEANING

The present invention relates to an apparatus and method for localised surface cleaning, and more particularly to an apparatus for and method of cleaning a surface, such as the surface of a tubular member, a platform leg, the steel jacket of a platform, a riser, pipeline or other subsea component, the hull of a ship, or cleaning the weld seam between pipes or other tubular members. The invention may find particular application in removing marine growth, coatings, rust and scale amongst other things from the surface of these structures.

In the offshore hydrocarbons industry, oil and gas are typically recovered from a subsea reservoir with drilling and intervention work carried out from a platform above the reservoir. The recovered hydrocarbons are either transported to the surface for processing and/or transported via pipelines from the subsea wellhead to downstream storage and processing facilities.

Depending upon the water depth, the platform legs may be formed of a steel jacket comprising vertical, horizontal and diagonal sections of tubular steel members which extend from the platform directly to the seabed. Alternatively on a semisubmersible platform, the legs may terminate at a submersible hull which sits below the surface. In other cases risers or tethers may be in place between the seabed and the legs of the platform.

During the lifetime of the offshore structures, the surfaces of the elements and particularly the welds between subsequent elements must be inspected in order to verify and document the integrity of the elements and welds. Any damage or deterioration could result in failures which in turn could lead to human loss of life and environmental damage.

Subsea equipment is vulnerable to various issues which can affect their integrity.

Corrosion, biofouling, growth of marine life, on the surface of the jacket or pipe sections and particularly around the weld seams.

As part of the inspection process, the structures must be cleaned in order to remove any marine growth, rust, scale or other coatings in order to provide access to the surface of the structure and particularly the joint sections to allow a full visual and/or non-destructive testing inspection to be carried out.

In a known system a magnetic weld cleaning apparatus is deployed to the appropriate part of the structure using an ROV operated from the surface. The cleaning apparatus is placed on the surface of the structure and retained in position by powerful magnets. The apparatus is then driven around the structural members and a jetting system carried on the apparatus is operated to direct a high powered jet of fluid at the surface to remove marine growth and any rust, scale or coatings from the weld surface. The cleaned surface including welds can then be inspected either by a diver or by visual inspection systems either mounted on the cleaning apparatus or on the ROV and any issues can be reported to the operator at the surface. Once the cleaning operation is completed, the apparatus must be recovered from the surface of the structure against the magnetic force which holds the apparatus on the surface. This is typically achieved by operating the ROV to grasp the cleaning apparatus and pull the apparatus off the surface of the structure.

Whilst the known system provides cleaning of the weld seam, mounting and recovery of the apparatus to the equipment surface can lead to damage to the equipment. The magnets which hold the apparatus against the equipment surface must be strong enough to securely hold the apparatus on the surface while the apparatus is driven around the outer surface of the equipment. As the magnets are powerful, they begin to draw the apparatus towards the surface even before the apparatus is in contact with the considered outer surface. The apparatus must therefore be very carefully positioned before the magnets pull the apparatus onto the equipment surface. If the apparatus is misaligned on the surface it will have to be removed and replaced before the inspection operation can begin. This repeated placement and removal of the apparatus can lead to damage to the equipment or indeed damage to the apparatus itself.

Removing the apparatus by applying a pulling force by the ROV can also lead to damage to the ROV as the pulling power of the ROV must be sufficient to overcome the strong magnetic force of the magnets. It is an object of the present invention to provide a cleaning apparatus and a cleaning method which overcome or at least mitigates the above problems associated with the known cleaning systems.

According to one aspect of the present invention there is provided an apparatus for localised cleaning of a surface, the apparatus comprising a body, at least one jet or nozzle mounted on the body for directing a high pressure stream of fluid at the surface and a securing device mounted on the body for attaching the body to the surface, and further comprising a base member extendible from and retractable within the body and means for moving the base member with respect to the body from a first position in which the body is in contact with the surface to a second position in which the body is spaced from the surface such that the position of the body can be finely adjusted relative to the surface before the securing device is engaged with the surface to firmly hold the body on the surface.

Advantageously the securing device comprises a plurality of magnets.

Preferably the magnets are moveable mounted on the body.

Preferably the plurality of magnets are mounted in an array around the body.

Preferably the apparatus is adapted for mounting against the outer surface of a tubular member, such as a casing, pipe or riser.

Advantageously the apparatus is adapted for localised cleaning of a weld seam on a tubular member.

Conveniently the apparatus further comprises means for driving the body across the surface to be cleaned.

Advantageously the apparatus comprises a cleaning head within which the jet or nozzle(s) is/are mounted.

Advantageously the apparatus comprises a plurality of nozzles.

More preferably, the cleaning head is movably mounted on the frame to allow the head to oscillate over the weld seam.

Advantageously the cleaning fluid is water.

Preferably a cylinder is provided for moving the base member relative to the body between the extended and the retracted positions.

More preferably the cylinder is a hydraulic cylinder which is preferably mounted on the body of the apparatus.

Preferably the base member is a landing skid which can be carried, deployed or otherwise manipulated by an ROV to position the apparatus on the surface to be cleaned.

Advantageously visual inspection means may be mounted on the body for providing information to the operator.

Preferably the visual inspection means is a camera.

Advantageously the camera is remotely controlled such that an operator on the surface can activate the camera.

Advantageously the apparatus is neutrally buoyant in sea water.

Preferably a buoyancy material may be mounted to the body and more preferably the buoyancy material may comprise a foam.

Preferably also the apparatus further comprises a frame which surrounds the body of the apparatus to facilitate connection to an ROy.

According to a second aspect of the present invention there is provided a method of localised cleaning of a surface using the apparatus of the first aspect of the invention, the method comprising the steps of, extending the base member from the body of the apparatus, deploying the apparatus to a surface to be cleaned, landing the apparatus on the surface, adjusting the position of the apparatus to position the cleaning head above the required location before retracting the base member into the body of the apparatus to bring the securing device of the apparatus into contact with the surface to firmly hold the body in the required position and driving the cleaning apparatus across the surface while activating the cleaning apparatus to clean the surface.

Advantageously the method further includes the step of recovering the apparatus from the surface by extending the base member from the body of the apparatus against the surface to release the body and overcome the attractive force between the securing device and the surface.

Embodiments of the present invention will now be described with reference to the accompanying figures in which: Figure 1 is a schematic perspective view of an apparatus according to one aspect of the present invention; Figure 2 is a side view of the cleaning apparatus of Figure 1 with the frame removed for clarity and the landing platform extended; Figure 3 is a schematic view of the underside of the cleaning head of the apparatus of Figure 1; Figure 4 is a part exploded view of the drive mechanism for one side of the cleaning apparatus of Figure 1; Figure 5 is a detailed view of a magnet arrangement of the cleaning apparatus of Figure 1, and Figure 6 is a schematic view of a plurality of magnets of Figure 5 in the cleaning apparatus of Figure 1.

Turning now to the figures, Figure 1 shows a schematic view of a cleaning apparatus 1 according to one aspect of the present invention. The apparatus comprises a frame 2 upon which the components of the apparatus are mounted.

The frame has a handle 3 or other graspable component which allows the frame to be carried or manipulated by an ROy.

The cleaning apparatus comprises a body 4 mounted within the frame. In the preferred embodiment the body is formed of a plurality of spaced parallel plates 5 mounted between a series of spaced structural rods or bars 6 which extend across the apparatus. The plates have apertures 7 through which the rods pass in order to retain the plates in the required spaced array. A buoyancy foam (not shown) may be provided between adjacent plates of the body to reduce the weight of the body and assist in placement and manoeuvring of the body. The application of the foam ensures that the body is neutrally buoyant in water.

The apparatus is carried on a landing skid 8. The landing skid comprises a base 9 formed of tubular members 10 which form a platform that can be extended from or retracted into the under surface of the body 4. A hydraulic ram 11 is mounted on the body and operable for moving the platform between the extended and retracted positions. The skid also comprises a pair of upstanding tubular members 12 which extend through the body 4 and act to keep the skid level as it extends from and retracts into the frame. In Figure 1, the skid is shown in the extended position in which it projects from the underside of the body.

The frame 2 is provided around the body to allow the apparatus to be carried by and otherwise manipulated by an ROy. The handle 3 is preferably on an upper surface of the frame to allow the ROV to pick up and position the apparatus for use as described below.

In the preferred embodiment, the underside 13 of the body is curved to allow the apparatus to follow the curved outer surface of a pipe but other embodiments are envisaged in which the underside of the frame is linear to follow a flat surface.

A cleaning head 14 is mounted on one end of the body. Preferably the cleaning head is mounted on a leading end 15 (in use) of the body. The cleaning head comprises a conventional module with a plurality of nozzles 16 through which a high pressure jet of water or other cleaning fluids can be forced. The cleaning head may be provided with means (not shown) for adjusting the position of the head with respect to the body of the apparatus. Furthermore, the cleaning head may be mounted to the body of the apparatus in such a manner as to allow oscillation of the cleaning head with respect to the body. A dedicated motor and associated gearbox (not shown) may be provided for the cleaning head.

An additional nozzle arrangement is mounted on a bar 17 on the body of the apparatus and directs high pressure water to the landing skid 8 as will be described below. Alternatively or additionally a further nozzle arrangement may be mounted on a bar on the skid.

A plurality of magnets 18 are mounted, preferably in an array, on the other end of the body 19 remote from the cleaning head. Preferably the magnets are mounted on a trailing end (in use) of the body. Each magnet is mounted between a pair of adjacent plates 5 of the body. The magnets function as a securing or gripping device to securely hold the body 4 in position on a surface to be cleaned. Each magnet is independently mounted within a housing 20 on the frame. A spring 21 is provided on the housing and biases the magnet away from the underside of the body whilst allowing the magnet to move back towards the body against the spring bias in response to localised variations in the surface being cleaned. In some embodiments the magnets may extend out of the underside of the body and be retracted within the underside of the body. The housing 21 protects the magnet and in the preferred embodiment, each magnet exerts a 116kg force.

The body 4 is provided with wheels 22, preferably one at each corner of the body.

Drive means 23, are mounted on the body for driving the wheels to move the body over a surface upon which it is placed. A separate drive means is provided for each pair of wheels on each side of the body and independent drive can be delivered to each wheel. This allows the direction of the body to be finely controlled by controlling the drive applied to each side of the body independently.

The drive means 23, 23' comprises a hydraulic motor 24 on each side of the body which is connected through a coupling 25 to a gearbox 26. A cog 27 is fixed to each wheel and a first chain 28 extends around the cog of the rear wheel and an output shaft (not shown) of the gearbox, and a second chain 29 extends around the cog of the forward wheel and the output shaft of the gearbox. A chain tensioner 30 may be provided for adjusting the tension in each of the chains as required.

An umbilical (not shown) provides power from the surface to the apparatus.

The apparatus further comprises a valve arrangement 31 which may be linked to the landing skid and allows fluid to be switched from the pre-cleaning bars 17 to the cleaning head 14 and allows the operator to switch from pre-cleaning the surface on which the apparatus is landed to direct localised cleaning of the surface once the apparatus is secured in the operating position.

The use of the apparatus in a cleaning operation will now be described. The cleaning apparatus 1 is prepared on the surface and the hydraulic cylinder 11 is operated to extend the platform 9 of the landing skid 8 from the underside of the body 4. The apparatus is then transported by a diver or ROV to the required subsea location at which the cleaning operation is to be carried out. This may be cleaning of a circumferential weld seam between successive pipes of a pipeline for example or successive steel members as part of a platform jacket.

The ROV manoeuvres the apparatus I into position above the weld seam between the two pipes for example and moves the apparatus towards the weld seam until the platform 9 of the landing skid 8 contacts the outer surface of the pipes surrounding the weld seam. With the landing skid in the extended position, the underside of the body 4 is spaced from the outer surface of the pipe, and importantly, the magnets 18 mounted between the plates 5 of the body are held at a position spaced from the surface of the pipe even though they are biased away from the underside of the body. In this position the cleaning apparatus is not fixed in position on the pipe and the attractive force between the magnets and the pipe surface cannot pull the body 4 any further towards the pipe due to the extended landing skid 8.

Therefore, if the position of the apparatus 1 needs to be adjusted before the cleaning operation begins, the ROV can simple lift the apparatus clear of the surface as the magnets 18 are not engaged with the surface and thus fine adjustment of the position of the apparatus can be very simply achieved. Thus the landing skid 8 provides a soft land component to the apparatus I which allows for fine positioning of the apparatus on the surface.

The pre jetting means 17 are then activated in order to force fluid against the surface of the pipe to prepare the landing surface for the apparatus. This ensures a clean surface upon which the apparatus 1 can be landed to avoid problems for example in landing the apparatus on an uneven or fouled surface which could compromise the ability of the apparatus to ride securely over the surface of the pipe.

Once the apparatus is in the required position and the landing site has been prepared, the hydraulic cylinder 11 is activated in order to retract the landing skid 8 into the underside of the body 4, thereby lowering the body towards the surface to be cleaned. As the body is lowered, the magnets 18 draw the body into contact with the surface and securely hold the body against the surface.

The drive means 23, 23' can then be operated to drive the apparatus over the surface following the desired path whilst the cleaning head 14 is activated to facilitate cleaning of the surface. The cleaning head can be oscillated over the surface to assist with the cleaning operation and to widen the range of the cleaning apparatus without compromising the surface finish. The cleaning head can be adjusted in order to change the stand-off of the cleaning head from the surface of the pipe.

As the apparatus 1 rides over the surface that has just been cleaned, the magnets 18 retain a very strong hold on the surface despite the retro jet forces from the high pressure jet of fluid being forced against the surface from the nozzles of the cleaning head 14 and this ensure that the apparatus does not deviate from the desired cleaning path.

As the apparatus is driven over the surface, the spring loaded magnets 18 can react to any localised variation in the surface such as irregularities in the surface or localised marine growth, and follow the surface profile whilst maintaining the body securely in contact with the surface.

The apparatus can be used to provide surface cleaning on different diameters of pipes or tubular members, platform legs, platform jackets or risers as the magnets securely hold the apparatus on the surface and independently move within their respective body plates against the individual mounting springs 21, thereby avoiding the need to provide a number of differently sized cleaning apparatuses for cleaning a range of pipes of differing diameters. Furthermore, as the magnets 18 are independently mounted on the body 4, and preferably independently moveable, they can be independently replaced which provides for simple and cost effective maintenance of the apparatus between cleaning operations.

During the cleaning operation localised marine growth, coatings, rust, scale and flakes of metal can all be removed from the surface being cleaned. The apparatus I then drives forward over the surface which has just been cleaned which ensures that the apparatus is always securely held on the surface.

As each side of the apparatus is provided with an independent drive train 23, 23', the movement of the apparatus over the surface can be very finely controlled and the apparatus can be directed to move on a straight path by driving each side of the apparatus at the same speed. Alternatively, one side of the apparatus can be driven at a slower speed than the other which will cause the apparatus to turn over the surface being cleaned. Therefore the apparatus can be very finely controlled to driver over a surface whilst avoiding any structural features on the surface. The speed of operation of the apparatus can be controlled by an operator from the surface.

The cleaned surface can be visually inspected via a camera mounted on the frame.

After the cleaning operation is complete, the cleaning jets of the cleaning head 14 are deactivated and the hydraulic cylinder 11 is activated in order to extend the landing skid from the underside of the body. As the landing skid 8 is extended out of the underside of the body 4, the body is pushed off the surface which pulls the magnets 18 out of contact with the cleaned surface. This provides a secure system for removing the cleaning apparatus which mitigates against damage either to the cleaned surface or to the cleaning apparatus.

The ROV can then be driven to move the cleaning apparatus to a new location on the pipe, for example the next successive weld seam, where the apparatus can be deployed onto the surface as described above.

The use of the present invention has been described above in relation to subsea pipeline comprising a plurality of pipe sections welded end to end, or legs and jackets of a platform, but it will of course be appreciated that the present invention will also find application in relation to cleaning of the external surface of other subsea structures such as subsea risers for example, both in terms of the external surface of the riser and also circumferential welds between connected riser sections, and also non-tubular structures such as the hull of a vessel, semisubmersible structure, storage tanks or offshore platforms where the apparatus of the present invention can be located on the surface to be cleaned and operated to drive across the surface following the contours of the surface to provide an effective cleaning solution for such structures.

Furthermore, while the present invention has been described in terms of cleaning of a surface, it will be understood that by changing the composition of the fluid forced through the nozzles in the cleaning head, the apparatus could also be used in other operations such as for example severance operations. By adding sand or some other rough particulate material to the fluid flow, the jetting fluid could also be used to cut through a surface such as a pipe or other structure.

The securing device is described in the embodiments above as comprising a plurality of magnets which hold the apparatus securely in position on the surface to be worked on. It is envisaged that the magnets could be replaced with components such as a vacuum generating device to create suction between the apparatus and the surface or alternative suctions generating devices.

Claims

CLAIMS1. An apparatus for localised cleaning of a surface, the apparatus comprising a body, at least one jet or nozzle mounted on the body for directing a high pressure stream of fluid at the surface and a securing device mounted on the body for attaching the body to the surface, and further comprising a base member extendible from and retractable within the body and means for moving the platform with respect to the body from a first position in which the body is in contact with the surface to a second position in which the body is spaced from the surface such that the position of the body can be finely adjusted relative to the surface before the securing device is engaged with the surface to firmly hold the body on the surface.
2. An apparatus according to claim 1, wherein the securing device comprises a plurality of magnets.
3. An apparatus according to claim 2, wherein the magnets are moveable mounted on the body.
4. An apparatus according to claim 3, wherein the plurality of magnets are mounted in an array around the body.
5. An apparatus according to any of the preceding claims, wherein the apparatus is adapted for mounting against the outer surface of a tubular member, such as a casing, pipe or riser.
6. An apparatus according to claim 4, wherein the apparatus is adapted for localised cleaning of a weld seam on a tubular member.
7. An apparatus according to any of the preceding claims, wherein the apparatus further comprises means for driving the body across the surface to be cleaned.
8. An apparatus according to claim 7, wherein independent driving means are provided on each side of the body for driving each side of the body independently from the other.
9. An apparatus according to any of the preceding claims, wherein the apparatus comprises a cleaning head within which the jet or nozzle(s) is/are mounted.
10. An apparatus according to claim 9, wherein the cleaning head is movably mounted on the frame to allow the head to oscillate over the weld seam.
11. An apparatus according to any of the preceding claims, wherein the cleaning fluid is water.
12. An apparatus according to any of the preceding claims, wherein a cylinder is provided for moving the base member relative to the body between the extended and the retracted positions.
13. An apparatus according to claim 11, wherein the cylinder is a hydraulic cylinder mounted on the body of the apparatus.
14. An apparatus according to any of the preceding claims, wherein the base member is a landing skid.
15. An apparatus according to any of the preceding claims, visual inspection means may be mounted on the body for providing information to the operator.
16. An apparatus according to claim 15, wherein the visual inspection means is a camera.
17. An apparatus according to claim 16, wherein the camera is remotely controlled such that an operator on the surface can activate the camera.
18. An apparatus according to any of the preceding claims, wherein the apparatus is neutrally buoyant in sea water.
19. An apparatus according to claim 18, wherein a buoyancy material is be mounted to the body.
20. An apparatus according to claim 19, wherein the buoyancy material comprises a foam.
21. An apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
22. A method of localised cleaning of a subsea surface comprising the steps of, extending the base member of an apparatus according to any of claims 1-20 from the body of the apparatus, deploying the apparatus to a surface to be cleaned, landing the apparatus on the surface, adjusting the position of the apparatus to position the cleaning head above the required location before retracting the base member into the body of the apparatus to bring the securing device of the apparatus into contact with the surface to firmly hold the body in the required position and driving the cleaning apparatus across the surface while activating the cleaning apparatus to clean the surface.
23. A method according to claim 22, further including the step of recovering the apparatus from the surface by extending the base member from the body of the apparatus against the surface to release the body and overcome the attractive force between the securing device and the surface.
24. A method of localised cleaning of a subsea surface substantially as hereinbefore described.