Tool carrier and method for carrying tools for cutting elongated structures.

The present invention concerns a tool carrier for carrying particularly cutting tools for cutting elongated structures, such as jacket legs or gravity based structures, cooling towers for power plants etc. typically of reinforced concrete. Furthermore the invention concerns a method for cutting such a structure, in particularly for decommissioning purposes. The method can also be used on other structures where remote operation is a requirement. Other fields of use may include nuclear power stations, hydro electric power stations, bridges and buildings. When offshore oilfields are being depleted or offshore platforms of some reason are taken out of service, the companies running the installations are obliged to remove or maintain at least parts of the installation. Such decommissioning and removal poses several challenges. One of the challenges is to be able to lift and remove sections. As many installations includes a topside with a Main Support Frame or MSF fixed to gravity based includes structures GBS or jacket legs. In many cases, these legs must be cut before the MSF can be lifted. Legs of this kind are often of steel reinforced concrete. It is essential not to cut into the steel reinforcements as that will jeopardize the integrity of the leg with possible leg failure and fatal consequences. Clearly it would be an advantage if such cutting can be controlled from a remote location to reduce the risk for the operating personnel.

Automated cutting devices for remotely controlled cutting can for instance be found in WO 00/78491. The publication shows pipeline cutting at the seabed with a driven diamond wire on a u-shaped sub frame. Another remotely controlled unit for use in connection with work on structures can be found in WO 99/10232. The publication shows a structure that can be opened and closed around a pylon. The structure includes a carriage with wheels or drive means to engage the pylon to enable the carriage to be moved along the pylon. The structure is a pylon servicing apparatus that can be used for surface treatment of the pylon, and is particularly intended for use in an underwater environment. The unit can be moved up and down the pylon and is adapted to carry surface treatment equipment.

WO 99/43921 describes a method and device in particular a frame for removal of topsides from a substructure. The publication shows a structure that is fixed to jacket legs, and cutting of the legs.

Accordingly there is a need for an apparatus and a method for remote controlled work on large structures in particular for cutting purposes. The tool carrier and the working platform is particularly developed to ensure safety for personnel and equipment, and to achieve accuracy of the cutting operation. The tool carrier is designed for operation of all kinds of suitable cutting methods. The tool carrier may be designed to operate both submerged and in air. The tool carrier can be designer to operate at depths of 150m and more.

It should be possible to operate the tool carrier with a high degree of remote control and operation.

Industrial rope access techniques may be used during assembly and disassembly. Required personnel may access the tool carrier by means of wire between the tool carrier and an operations vessel.

It is essential that the tool carrier can be positioned and controlled with high accuracy. The tool carrier can be modular and can be assembled as needed for a variety of uses and can be adapted according to the size and design of the object to be cut. The tool is particularly adapted to be able to carry a saw unit that can be used very close to overhead structures such as offshore platform legs immediately below a main support frame. This means that the saw should be placed at an extreme end of the carrier. With these structures it can be of great importance to be able to cut in a zone between the upper part of the leg and the main support frame where the leg does not include steel reinforcements. This can be a zone with a height of approximately 15 cm, so positioning and accuracy is vital.

There are no dimensional limitations, including limitations in height. The tool carrier of the invention may include equipment for measurements in all directions, weight control, positioning systems and systems for remote control and monitoring.

This is achieved with an apparatus and a method according to the independent claims of the application, claiming a tool carrier for carrying tools for working on elongated structures. The carrier is particularly suited for cutting

purposes, but it may also be used for drilling into the structure, surface preparation, various kinds of machining and any other processes requiring access to an elongated structure.

The tool carrier includes a frame like structure with at least two parts and a central opening, adapted to surround the elongated structure to be worked on. The at least two parts of the frame can be released from each other sufficiently to open the frame and allow the elongate structure to be placed in the opening of the frame, and to lock the parts of the frame when the elongated structure is placed in the opening of the frame. At least two winches are placed on the frame, for lifting, lowering or holding the tool carrier in relation to the elongated structure. The number of winces may be adapted to particular needs. One winch may also pull several wires. Holding elements are connected to the frame and are adapted to be pressed between the elongated structure and the frame to hold the frame in a fixed position on the elongated structure. The holding elements may include rollers or wheels adapted to roll on the elongated structure when the tool carrier is moved up and down on the elongated structure or only pads to hold the structure.

The rolling elements may include propulsion means for rotating the rolling elements. The rolling elements may include locking means, for locking the rolling elements in a fixed position.

The holding means may include actuators, adapted to press the holding means between the frame and the elongated structure to be worked on.

The tool carrier may include a tool platform, adapted to be placed on the frame, for rising or lowering the tool in relation to the frame.

Furthermore the invention includes a method for cutting substantially vertical or inclined structures with a tool carrier carrying cutting means. Vertical or substantially vertical in this regard means structures with a vertical component sufficient to allow the winches and wires to lift and lower the tool carrier. In practise this means that a considerable inclination can be accepted. The method includes the steps of opening a frame, and moves the frame around the elongated structure to be cut. The frame is then closed around the elongated structure to be cut. The tool carrier is lifted with winch means on the tool carrier, along the elongated

structure to be cut with wires secured above the place the elongated structure is to be cut, until the tool carrier is placed in the vicinity of the place the elongated structure is to be cut. The tool carrier is then held in place by actuating actuator means, pressing holding the holding means attached to the tool carrier towards the elongated structure to hold the tool carrier in a fixed position in relation to the elongated structure. The cutting means are then actuated for cutting the elongated structure until the cut has been made. The holding elements are then released from the elongated structure, and the tool carrier is lowered with the winches along the elongated structure. Finally the frame is opened and the tool carrier is removed from the elongated structure.

The tool carrier may include an extendable tool platform placed on the tool carrier, and the method may further include moving the tool carrier to a location below the place the structure is to be cut, rising the tool carrying platform up to the location where the elongated structure is to be cut and cutting the elongated structure with cutting means placed on the extendable platform.

Short description of the figures: Fig. 1 shows an embodiment of the invention in use; Fig. 2 is a perspective view of a detail of the invention shown on fig. 1 ; Fig. 3 shows a part of the invention according to the embodiment on fig. 2;

Fig. 4 is a perspective view of the previously shown embodiment of the invention, this assembled;

Fig. 5 shows the embodiment of the invention shown on the other figures, in use; Fig. 6 shows a detail of the invention, this assembled;

Fig. 7 shows the previously shown embodiment of the invention from below, in use;

Fig. 8 shows the embodiment of the invention from above, before it is used; and Fig. 9 shows the embodiment of the invention placed around a jacket leg.

Detailed description of an embodiment of the invention with reference to the enclosed figures:

Fig. 1 shows a tool carrier 3 according to the invention placed on a structure 1 such as a gravity based structure or leg for an offshore installation with a main support frame (MSF) 2 placed on the gravity based structure. The tool carrier 3 is connected to a supply of energy, control inputs and signals through an umbilical cord 6. The umbilical cord 6 may be connected to a station for instance on a supply ship. Alternatively, the cord 6 may only be used to supply energy, and the control may be performed by radio communication. The vessel may be a Multi Support Vessel (MSV) or a Crane Barge (CB).

Winches 5 close to each corner of the tool carrier 3 include wires secured to the main support frame 2, or anywhere else above the tool carrier 3 to enable the tool carrier to lift it self to a predetermined position on the jacket leg or structure 1. Holding elements 4 attached to the tool carrier 3 holds the tool carrier 3 in a fixed position, alone or in combination with the winch system and wires, and the holding elements 4 may include driving elements helping the tool carrier 3 to move up and down, and locking elements, to hold the tool carrier 3 in a predetermined position with a sufficient accuracy to allow the tool on the tool carrier 3 to carry out work within required tolerances. The holding elements 4 are also used to guide the carrier 3 along the structure 1.

The holding elements 4 may include rollers made of rubber or any other suitable material, preferably with high friction and shock absorbing properties. The securing system, securing the rollers to the frame of the tool carrier 3, may also include shock absorbers or any resilient elements resistant to impact between the unit and the structure 1 the carrier 3 is to be used in connection with. The figure shows four holding elements for guiding and holding the tool carrier 3, but the number of holding elements 4 may be any suitable number for instance two, three, five or more, to accommodate different needs.

The tool carrier 3 is shown with a substantially square frame, but the shape is only restricted by the structure the carrier is intended to be used in connection with. The frame of the carrier may well be round, rectangular, oval, triangular etc. as long as the opening in the middle is suitable.

Fig. 2 shows a detail of the tool carrier shown on fig. 1 , but where the tool carrier 3 is placed at sea level around the structure 1. The winches 5 placed

closed to each corner of the tool carrier are clearly shown. Furthermore, fig. 2 shows a tool 7, shown as a wire cutting device with for instance a diamond wire.

Furthermore, the holding elements 4 are shown as drums shaped to accommodate the shape of the structure 1. The tool carrier 3 may include tanks that can be ballasted, to control the buoyancy of the tool carrier. The tool 7 can move along rails along the frame of the tool carrier, to enable the tool 7 to cut through the entire structure 1 to be cut. The holding elements may as previously mentioned include rolls that can be driven by suitable driving means, such as hydraulic motors, electric motors etc. Furthermore, the holding elements 4 may include suitable breaking means well known within the area for holding the drums and accordingly the tool carrier 3 in a fixed position in relation to the structure 1. The holding elements 4 may include telescopic elements or any other suitable elements to enable adjustments of the holding element towards the structure 1. Elements such as hydraulic cylinders (not shown) drive screws, rack and pinion mechanisms etc. may be used to control and adjust the position of the holding elements 4. Furthermore, these elements may be used to press the holding elements 4 towards the structure 1 with a suitable force.

Fig. 3 shows how the tool carrier 3 may be divided into in two units to enable the tool carrier 3 to be placed around the structure 1 to be cut. Fig. 3 shows the umbilical cord 6, two winches 5, and the holding elements 4 with rollers. The rollers of the holding elements may be substituted by pads or cushions that can slide along the structure 1. A combination of rollers and pads may also be used.

Fig. 4 shows the tool carrier 3 divided into two parts to enable the tool carrier 3 to be placed around the structure 1. The figure clearly shows how the tool carrier 3 can be deballasted and can float for assembly while afloat. The two parts can be assembled with a bolted connection, or with any other suitable connecting means. Deballasting means on the tool carrier 3 also enables to use the tool carrier 3 sub sea, and sub sea assembly of the two parts may in some cases also be favourable, in particular in harsh whether conditions. The tool carrier 3 may also be submerged when it not is in use to protect it from harsh weather conditions.

The two parts of the tool carrier 3 may be brought towards each other with suitable support vessels, with cables pulled between the two parts, or in any other suitable way.

Fig. 5 shows the tool carrier 3 in place on a structure 1 to be cut. The structure 1 is a jacket leg, and a main support frame 2 is placed on the jacket leg. The umbilical 6 is shown between the tool carrier 3 and a buoy 8. The umbilical cord 6 extends all the way to a supply ship 9 that provides energy and control input to the tool carrier 3.

Fig. 6 shows a part of the tool carrier 3 where the winches 5 and the holding elements 4 are more clearly shown. Furthermore, a tool 7 is carried by the tool carrier 3. The tool 7 is shown as a wire saw that can move along rails 9 on the tool carrier 3. The holding elements 4 may as previously mentioned be movable in and out in relation to the frame of the carrier 3. They may also be pivotable up and down for easy adjustment and may include resilient and shock absorbing elements in addition to censors and other equipment for monitoring positions, forces etc.

Fig. 7 clearly shows how the holding elements 4 of the tool carrier 3 with drums or rolling elements holds the tool carrier 3 in a fixed and adjustable position in relation to the structure 1. Furthermore, the umbilical 6 is clearly shown.

Fig. 7 also shows how driving and the locking elements on the rollers, in connection with actuators on the frames 11 holding the rollers can be used to impose a force between the holding elements 4 and the structure 1 , and how the holding elements can be used to adjust and hold the position of the tool carrier. The frames 8 may be extended in and out and in some embodiments up and down. One of the wires 10 from the winches is shown attached to the main support frame 2.

Fig. 8 is a further view of the invention where the tool carrier 3 is shown with four winches 5 with cables 10 extending up to a place above the structure 1 to be cut. The wires 10 may for instance be secured in a main support frame 2. Fig. 8 shows how the tool carrier 3 floats on the sea before it is raised into position with the winches 5 pulling in the cables 10. The rolling elements on the holding elements 4 control the motion of the tool carrier 3 along the structure 1. Propulsion on the rollers of the holding elements 4 may be used to facilitate this.

As previously mentioned, the tool carrier 3 may be ballasted to a submerged position. Fig. 8 furthermore shows a buoy 8 for connection of the umbilical cord.

Finally, fig. 9 corresponds to the other figures, and highlights the use of wires 10 extending from the winches 5 to raise an lower the tool 3 controlled by the holding elements 4 on its path along the structure 1.

When the tool carrier is to be used, it may be disassembled, as shown on figure 4 into two parts. The two parts can be launched separately, or the tool carrier may be launched as one unit and may then be disassembled. The two parts can be floated around the structure 1 , and can be brought towards each other by suitable vessels, cables etc. as previously mentioned. The two parts are then assembled with bolts or with any other suitable means such that the tool carrier forms one unit surrounding the structure 1. The wires 10 may then, as for instance shown on fig. 8, be secured to a structure above the place where the tool carrier is to be put in service. This may for instance be to a main sport frame 2. The winches 5 may then be used to pull the tool carrier 3 along the structure 1 while the position of the tool carrier is controlled by the holding elements 4 and is monitored with cameras and other monitoring equipment. The winches can pull the tool carrier 3 along the structure 1 until the tool carrier 3 is in its desired position as for instance shown on fig. 1. The rollers on the holding elements 4 may then be locked in position, holding the tool carrier 3 in a fixed position, with or without the aid of the cables 10 from the winches 5. The tool 7, for instance as shown on fig. 6, may then be put into service, and the tool 7 may move along the rails 9 shown on fig. 6, cutting through the structure 1. Cameras and other monitoring equipment may be used for monitoring and control purposes.

When the structure has been cut, and the tool carrier 3 with tools 7 has performed its task, the holding elements 4 may be released, and the winches 5 can lower the tool carrier 3 by the wires 10 for removal.

The figure shows how to do this on a seabed, but the unit may well be used on land installations, but in this situation, units enabling the carrier to be moved on land such as wheels may be included instead of the ballasting system.

The holding and supporting elements 4 should be designed to withstand shocks.

The ballasting of the tool carrier enables to tool carrier to be submerged such that the tool carrier can be parked and can be away from waves and other difficult conditions. This also enables the tool carrier 3 to be removed such that support vessels and other equipment more easily can gain access to the structure 1 or jacket leg. The tool carrier 3 can for instance be designed to be able to be operated submerged down to 150 meters or more. In the case where the tool carrier can be ballasted and deballasted, the tool carrier must of course include suitable equipment for this purpose, well known within the area.

The tool and the various parts of the tool carrier, including the winches and the holding elements should be remotely controllable, such that the tool carrier can be used with a minimum of manual work.

The tool 7 may alternatively be placed on a particular tool platform with an adjustable height in relation to the tool carrier 3 such that the tool can be more accurately positioned in relation to the structure 1 to be cut, and to enable the tool 7 to more easily gain access to the cutting zone, in particular cutting zones close to other structures.

The tool 7 is as mentioned shown as a wire cutter, but the tool may of course also be used with other suitable tools such as equipment for abrasive cutting, water cutting etc. The tool carrier can also be used to other tasks such as surface treatment, grit blasting, service and control, but this is not considered to be the most relevant field of operation for the unit.

Due to the considerable requirement for the position of a cut, the positioning of the tool carrier is of great importance. The unit may of course include control systems and sensors, measuring the position of the carrier 3 in relation to the structure 1 , the angels of the carrier, motion of the carrier etc.

The unit 3 is particularly adapted to be used in connection with cylindrical structures, but it may well be used for other structures with for instance square or oval cross section. The structure 1 may well also be tapered, conical, convex or concave, as the holding elements are adjustable. The rolling elements may be shaped to accommodate the shape of the structure 1.

The holding elements may include actuators for actuating the holding elements and may include hydraulic or pneumatic cylinders. The holding elements 4 may include rolling elements typically made of substantially cylindrical elements with a rubber surface, typical driven by hydraulic motors. The tool carrier 3 or frame may typically have four sides, with four corners, and a winch 5 will typically be placed at each corner. Wires 10 or elongated members of any kind such as ropes or chains from the winches 5 are attached somewhere above the place to be cut.

The tool 7, the tool carrier 3 is to carry, is typically a saw with a diamond wire, or a nozzle for abrasive cutting.

The tool carrier 3 and the tool 7 are adapted to be remotely controlled as normally the environment in question is considered dangerous.

The rolling elements 4 to be pressed against the structure 1 to be cut can be locked in position by any locking means such as ordinary friction brakes or mechanical stopping pawls to hold the tool carrier 3 in a fixed position in relation to the structure 1 to be cut.

The tool carrier 3 will typically include electronics to measure position, inclination, motion etc. to control the holding elements 4 and the winches 5 accordingly. A tool platform (not shown) may be located on the tool carrier to be able to raise and lower the tool to be carried for accurate positioning, to be able to make cuts that not are in the same plane, and to gain better access at cutting positions close to other structures.