Method and device for cutting underwater structures

Abstract: A method of cutting underwater structures which comprises the following steps: a local underwater step including: the anchorage of cutting means (T) in the cutting area, exactly positioned to effect the desired cut, to the structure (S) to be cut; a remotely-controlled step including: the automatic activation and de-activation, from a spot at the surface, of the cutting means (T) and the automatic feed thereof in the cutting direction from a non-interference position through the structure (S), the cutting means (T) being provided with cutting tools (14) for cutting metallic and non-metallic materials such as, for example, cement, concrete, rocks, or the like; a local underwater step for recovering the cutting means (T). The invention proposes as well a device for carrying out the method.

Description: The invention relates to a method and a device for cutting underwater structures and particularly for cutting underwater structures such as, for example, ducts, pillars supporting offshore platforms, or the like and which are made mostly of steel or other metals or of mixed materials, such as steel or other metals and cement, or the like. At present, said structures are cut manually by teams of underwater workmen who operate directly on the spot with suitable tools such as, for example, thermal lances, electrodes for underwater cutting, grinders, pipe-cutters, etc. However, these operations are tiresome, expensive and involve considerable fatigue and risks for the operating personnel. The high costs of these operations are determined by the considerable duration of the cutting operations, by the necessity to engage highly-specialized operating personnel in very dangerous conditions, and by the resulting necessity to provide adequate assistance means with a corresponding number of auxiliary operators. The operating conditions become even more difficult when the structures to be cut are of the composite type such as, for example, in case of elements constituted by concentric steel pipes whose interspaces are filled with concrete or cement. In effect, in these instances, the cutting through the interspace cannot be ensured even by the most sophisticated tools, so that the intermediate layer of cement must be broken down before acting on the inner pipes. The duration of these operations may last even several days. From US-A-3 056 267 a method is known for removing from submerges sites portions of piles previously driven at their lower ends into the water bed. However the said method can only be used with piles having a free and unobstructed cap end exposed above the water line, over which the weighted cutting frame of the apparatus according to this invention may be threaded. The above constitutes a serious limitation, making the method and the apparatus according to the said prior art reference suited for use only in a limited number of practical applications. Therefore, the invention is based on the problem of providing a method and a device for cutting underwater structures, which, thanks to a construction as simple and economical as possible, permit to carry out the cutting operations with extreme ease and rapidity, minimizing the risks and costs. The invention solves said problem by a method defined in claim 1 and the device defined in claim 3. According to a preferred improvement of said method, the feed of the cutting means is effected by the upward push of water on a body of lower specific gravity, while the push for feeding the cutting means against the structure is adjusted to the optimum value by varying the upward push, i.e. the specific gravity of said body. In addition to the merely constructional advantages, the method and device according to the invention permit to achieve undoubted functional advantages. The use of specialized underwater personnel is only required, if desired, in the anchorage, recovery and check steps in the course of the work. These steps require a very limited number of underwater operators. The cutting step, however, is controlled directly from the surface. This eliminates completely the disadvantages of the presently-used systems, thus minimizing the risks of the operating personnel and reducing considerably the costs of the operations. Moreover, the cutting operations do not suffer substantially from the meteo-marine conditions and can be carried out uninterruptedly throughout the 24 hours of the day, thus increasing the productivity and reducing the costs furthermore. The cold-cutting means used by the invention permit to obtain much shorter working periods and ensure the utmost safety when working on structures in dangerous environments such as, for example, in the presence of liquid or gaseous hydrocarbons or flammable compounds. The particular construction of the device enables the execution of cutting operations at any depth even exceeding the possibility of use of underwater operators, because the anchorage, recovery and check steps may be easily effected by means of submersible units or by remotely-controlled vehicles. The invention also relates to other characteristics which further improve said device and which form the subject of the subclaims. The particular characteristics of the invention and the advantages resulting therefrom will become more apparent from the description of a preferred embodiment, shown by way of non-limiting example in the accompanying drawings, wherein: Figure 1 diagrammatically shows the device according to the invention in the operative position for cutting a pillar supporting an offshore platform; Figure 2 is a top plan view of the device of Figure 1, anchored to the pillar to be cut; Figures 3 to 5 are side elevational views of the device, of the two end sides transverse to the cutting direction and of the side parallel thereto, respectively. The device shown in the figures is constructed in the form of a cutting frame T of rectangular or square configuration which is anchored directly in straddling relation to the element to be cut S of any structure, for example, around a pillar of an offshore platform. In the illustrated embodiment, the cutting line is displaceable along a cutting plane parallel to one of the longer sides of the cutting frame T. In order to effect a cut through the pillar along a horizontal plane, the cutting frame T, therefore, is arranged flatwise with the cutting line lying on said plane. The actuation and feed of the motors of the cutting frame is effected thanks to control and feed units U arranged at the surface, for example, on suitable auxiliary watercraft and which are connected by umbilical cables C to said cutting frame T. The motors of the cutting frame T may be of any type, namely of electric, hydraulic, pneumatic type, or the like. The cutting frame T is formed by a quadrilateral framework two opposite sides of which constitute slide guides 2,2' orientated in the cutting direction, parallelly to each other and to the cutting plane. Each guide 2,2' comprises two guide tubes 102,102' which are perfectly aligned to each other perpendicularly to the cutting plane. The free ends of the guides 2,2' are rigidly connected to each other, at one side by a transverse member 3 connecting the two guides and stationarily secured thereto, and at the opposite side by head members 5. The stationary transverse member 3 and the head members 5 constitute simultaneously the limit stops for the guides 2,2'. The side of the framework which is opposite to the stationary transverse one 3 is constructed as an openable gate-like member. It comprises a transverse member 4 which is removably secured to the corresponding head members 5 of the guides 2,2'. As shown particularly in figure 5, this is obtained with the aid of hinge-type locking members 6 comprising two bushes 106 which are secured to the head members 5 of the guides in spaced apart relation, and a tube member 206 co-axially arranged therebetween. The hinge spindle is formed by an extractable bolt 306 provided with a radial grasping extension 406 at an end thereof, preferably at the upper end. The transverse member 3, fixedly secured to the guides 2,2', is provided intermediately with an anchorage cradle 7 which forms a V-shaped accommodation seat in the cutting direction so as to match different shapes and diameters of the element S of the structure to be cut. Associated with the anchorage cradle 7 is a means 8 for tightening the element S of the structure against it. Said means can girdle the element S of the structure on the side away from the cradle 7 and in the illustrated embodiment it is formed by a metallic cable which is passed at least twice around the portion of the element S that is away from the anchoring cradle 7 and at planes which are spaced apart and parallel to the cutting plane, preferably coincident with the respective sides of the framework, in this instance with the upper side and lower side thereof. The free ends of the cable are fixedly connected to the opposite peripheral edges of the stationary transverse member 3 at points 10 thereon which are aligned to each other perpendicularly with respect to the cutting plane and which are arranged intermediately between one of the guides 2 and the corresponding side of the anchorage cradle 7, while it is turned round to points 10' which are symmetrically opposite with respect to the central axis which is directed in the cutting direction, between the opposite guide 2' and the facing side of the anchorage cradle 7. The connection of the ends of the cable is effected with the intermediary of adjustable tension means 9 such as, for example, turnbuckles or the like. Movably mounted on the slide guides 2,2' is a cutting unit which is formed by two slides 11,11' each comprising two tubular slide members 12 which are engaged on the respective guide tubes 102,102' and are connected rigidly to each other. The sliding movement of the slide members 12 is ensured thanks to an inner lining of suitable material such as, for example, teflon or the like. Each slide 11,11' carries a turn-round pulley 13,13' which is rotatable about an axis perpendicular to the cutting plane and having mounted thereon an endless cutting cable 14, for example, of the diamond-coated beads type and capable contemporarily both of cutting metallic materials and other materials such as cement, concrete, stone, or the like. Advantageously, the turn-round pulleys 13,13' are arranged in an outwardly-protruding position, both laterally and vertically beyond the corresponding sides of the slides 11, 11'. This permits to cut easily flush with the supporting bottom, for example, a vertical pillar such as that shown in the drawings with no need, unlike what has been effected heretofore, to dig a trench around the base of the pillar to permit the personnel to work. Specifically, the two turn-round pulleys 13,13' are mounted on shelves 111,111' of the slides 11,11', protruding outwards from the outer sides thereof. One of the two turn-round pulleys 13' is mounted stationarily and is associated with an actuating motor M. The other turn-round pulley 13 is mounted so as to be displaceable crosswise to the cutting direction towards and away from the powered pulley 13', so as to allow the cutting cable 14 to be mounted and made taut, said pulley 13 being associated with removable means 113 to lock it in position. Preferably, the displaceable turn-round pulley 13 has also associated therewith means for its predetermined positioning in an approaching position and in one or more tensioning positions of the cutting cable 14. In this example, the turn-round pulley 13 is rotatably mounted on a supporting plate 213. The plate 213 is secured to the shelf 111 by means of through-bolts 113 engaged in slots 211 in the shelf 111. Moreover, the plate 213 and bracket 111 have each two rows of at least two holes 311,313 therethrough in registry with each other and receiving a removable locking pin 15. This permit to effect with great rapidity the operations of mounting and tensioning the cutting cable 14. On the head member outer side facing towards the structural element S to be cut, each slide 11 is connected to a traction cable 16. The traction cable 16 extends exteriorly along the respective guides 2,2' and is turned round parallelly to the rear side of the stationary transverse member 3 by means of an idle turn-round pulley 17 which is rotatably mounted about an axis perpendicular to the cutting plane on a rear bracket 103 of the transverse member 3. Provided intermediately of the rear side of the transverse member 3 is a further shelf 203 mounting two additional turn-round pulleys 18 for directing the respective traction cable 16 in a vertical direction upwards. The turn-round pulleys 18 are comparatively close to each other and, preferably, they are mounted on a common bracket 19 which can oscillate about a horizontal axis parallel to the transverse member 3. The vertically turned round and near branches of the traction cable 16 are connected at their ends to a variable-buoyancy body 20, such as an inflatable balloon. By varying the amount of air or gas fed into the balloon, the buoyancy push thereon can be varied, thus obtaining the possibility of adjusting very simply the thrust of the cutting cable 14 against the element S to be cut in accordance with the power of the cutting unit and the type of materials constituting the structure. In addition, the arrangement of the vertically turn-round pulleys 18 on a common oscillatable bracket 19 permits the execution of cuts along planes of any inclination with respect to the horizontal plane, including the vertical direction. The application of the device to a structural element S to be cut is extremely rapid and simple. The cutting frame is straddled on the element S to be cut by removing the transverse removable member 4 and the cutting cable 14. After effecting the anchorage in the cradle 7 by the tightening means 8, the cutting cable 14 and removable transverse member 4 are mounted. Finally, the pre-established required amount of air or gas is fed into the balloon 20. From the above, it becomes apparent that said operations can be carried out easily and quickly by a reduced number of workers. At this stage, the underwater local operations have been completed, and the cutting stage may be controlled safely and with great ease from the surface. The only actuating motor to be fed adequately is, in effect, the one which is associated with the powered turn-round pulley 13' and is suitably connected to the control and feed means A at the surface. In the illustrated example, the pillars of the structure are formed by concentric steel tubes which are separated by an interspace which is filled with either cement or concrete. Upon activation of the device, the cable 14 of diamond-coated beads is displaced transversely against and through the pillar S with a constant and suitably calibrated force and it cuts indifferently and with no problems both the metallic and the concrete portions without requiring any interruptions for using either manually or automatically other types of tools. Of course, the invention is not limited to the embodiments just described and shown, but broad changes and modifications, especially of constructional nature, may be made thereto without departing from the basic principle disclosed above and claimed below.

Claims: A method of cutting underwater structures by a remotely-controlled step comprising the automatic actuation from the surface of cutting means and the automatic feeding in the cutting direction along the cutting plane, from the non-interference position with the structures towards and through it, the execution of the cut and automatic stoppage of the feed and actuation of the cutting means, characterised by : a local underwater step comprising firstly the positioning and anchorage to the structure (S) to be cut, in the cutting area thereof, of the cutting means comprising a cutting frame (T) carrying, mounted thereon, a displaceable cutting unit utilizing a closed loop endless diamond cable (11, 11', 12, 13, 13', 14, M) disposed so as to avoid interfering with the structure (S) during the said anchorage whereby the structure (S) is located completely outside of the closed loop cable (14), orientated with the cutting line thereof coinciding with the desired cutting plane and finally moving the cutting unit (11, 11', 12, 13, 13', M) towards the structure (S) to effect the cutting thereof; and a final local underwater step similar to the first step, consisting of the recovery of said cutting means. A method according to claim 1, characterized in that the feed movement of the cutting means (T) is activated by the upward push of water on a body (20) of lower specific gravity, while the thrust for feeding the cutting means (T) against the structure (S) is adjusted to the optimum value by varying the upward push, i.e. the specific gravity of said body (20). A device for implementing the method, according to claims 1 or 2 comprising a powered cutting unit (11, 11', 12, 13, 13', 14, M) displaceable in the cutting direction parallelly to the cutting plane on a cutting frame (T), so as to move the cutting unit (14), from an initial position of non-interference with the structure (S) to a final position wherein said cutting unit (14) have moved to the opposite side of the structure (S) to be cut by passing therethrough along the pre-established cutting plane, characterized in that it comprises: an underwater cutting frame (T) with releasable means (7,8) for positioning and anchorage to the structure (S) to be cut according to the pre-established cutting plane; a cutting unit comprising a closed loop endless diamond cable (11, 11', 12, 13, 13', 14, M) mounted on said cutting frame (T) and movable from a position in which the cable (14) is located completely outside of the structure (S), to an operating position in which the said cutting tools are moved along the cutting plane against and through the structure (S); an underwater adjustable unit (20) for displacing in the cutting direction said cutting unit which is supported by the underwater cutting frame (T); remote actuation and control means (A,C) for the cutting unit (11, 11', 12, 12', 13, 13', M, 14) and possibly for the traction unit (20), arranged at the surface. A device according to one or more of the preceding claims, characterized in that the cutting frame (T) comprises an anchorage cradle (7) which is open towards the inner side of the cutting frame (T) and having associated therewith removable means (8) for locking the structure (S) against the anchorage cradle (7); a pair of slide guides (2,2') provided with limit stops (3,5) at their ends, said guides (2,2') being directed in the cutting direction, parallelly to each other and parallelly to the cutting plane and being spaced from each other transversely to the cutting direction, and from the respective side of the anchorage cradle (7), and each of said guides (2,2') slidably carries a slide (11,11') for a respective turn-round pulley (13,13') being rotatable about an axis perpendicular to the cutting plane and extending substantially on said cutting plane, and at least one of said turn-round pulleys (13') being powered (M), while the cutting cable (14) which is of endless configuration, is mounted on both turn-round pulleys (13,13'). A device according to claim 4, characterized in that the cutting frame (T) is constructed as a rectangular framework and the anchorage cradle (7) is arranged interiorly thereof, in the region at one end of the guides (2,2'), centrally therebetween, and is open towards the opposite ends of the guides (2,2') which may be connected to each other by a removable gate-like transverse member (4), for example, by means of hinges (6) having an extractable hinge spindle (306), so that the cutting frame (T) can be opened for anchorage straddling the structure (S) to be cut. A device according to claims 4 or 5, characterized in that one turn-round pulley (13') for the cutting cable (14) is stationarily fixed on the associated slide (11') and is actuated by a motor (M) also carried by the slide (11'), while the other turn-round pulley (13) is mounted on the other slide (11) so as to be freely rotatable and displaceable from a position nearer to the powered turn-round pulley (13') to a position farther therefrom wherein the cutting cable (14) is tensioned, removable means (113) being provided to lock the displaceable turn-round pulley (13) in position. A device according to claim 6, characterized in that the displaceable turn-round pulley (13) is further associated with means for pre-established positioning, which may be locked temporarily (111,213,311,312,15) in the nearer position and in the cable-tensioning position. A device according to claim 7, characterized in that the displaceable pulley (13) is mounted on a plate (213) which is so restrained as to be slidable transversely to the cutting direction and lockable in position on a shelf (111) which is solidary with the slide (11), while the means which may be locked temporarily for pre-established positioning consist of coinciding rows of hole (312,311) in the slidable plate (213) and in the shelf (111) and of a temporarily locking pin (15) insertable into said holes (312,311). A device according to one more of the preceding claims, characterized in that the turn-round pulleys (13,13') protrude outwards from the cutting frame (T) so that the cutting plane is disposed exteriorly with respect to the facing parallel cutting frame (T). A device according to one or more of the preceding claims, characterized in that the traction unit comprises a variable-buoyancy hollow body (20), for example an inflatable balloon, which is connected via a cable (16) to each slide (11,11'), said cables (16) being exterior to the cutting frame (T), while the end portions thereof which are associated with the slides (11) are directed parallelly to the guides (2,2') and the end portions which are connected to the body (20) are diverted by means of turn-round pulleys (17,18) towards each other to a perfectly central point with respect to the two guides (2,2') and parallelly in a vertical direction upwards, the vertically-diverting pulleys (18) being mounted on a common bracket (19) which is secured exteriorly to the cutting frame (T) so as to be pivotable through an angle of at least 90° about a horizontal axis and in a central position between the two guides (2,2'), so that the cutting frame (T) can assume any inclined position between the horizontal and the vertical orientation of the cutting plane. A device according to one or more of the preceding claims, characterized in that the anchorage cradle (7) is secured to the transverse side (3) of the frame (T) that is opposite to the transverse side (4) constructed as an openable gate-like member, and said cradle is formed with a recess which tapers, for example in V-shape, in the cutting direction, while the tightening means (8) comprises one or more cables embracing the structure (S) on the side away from the anchorage cradle (7). A device according to claim 11, characterized in that the cables (8) extend within the cutting frame (T) that are parallel to the cutting plane and they are removably secured at their ends to the traverse side (3) which is associated with the anchorage cradle (7) and is opposite to the openable side (4), at intermediate points (10,10') between the anchorage cradle (7) and the respective guide (2,2'), said points being located symmetrically with the respect to the central axis of said cutting frame (T), there being provided tensioning means (9) which may be actuated manually or, for example, hydraulically or pneumatically. A device according to one or more of the preceding claims, characterized in that the sides of the cutting frame (T) that are orientated in the cutting direction are constituted by said guides (2,2'), while the sides that are transverse to the cutting direction are constituted by the transverse side in the form of a like-gate member (4) and by the opposite transverse side (3) associated with the anchorage cradle (7).

Inventors: MATTEUCCI FRANCESCO, MATTEUCCI, FRANCESCO
Applicants: MATTEUCCI FRANCESCO, MATTEUCCI, FRANCESCO
Application year: 1992
Main classification: B63C11
IPC codes: B28D1, B23D57, B63C11, E02D9, B23D53