Method and equipment for salvaging a wreck containing an environmental hazardous material

Abstract

 A wreck (1) containing an environmental hazardous material has at least a wreck section (2; 3) that rests on a bed of a body of water and is provided with a double-walled hull (4), which has an outer wall (7); an inner wall (8); and a plurality of stiffening ribs (9); a method for salvaging the wreck (1) provides for forming a number of recesses (54, 55, 56) into the hull (4); hooking a number of hook assemblies (20) to the hull (4) at the recesses (54, 55, 56); and lifting the wreck section (2; 3) from the bed of the body of water through the hook assemblies (20).

Description

[0001] The present invention refers to a method for salvaging a wreck containing an environmental hazardous material.

[0002] In particular, the present invention refers to a method for salvaging a wreck, which comprises at least a wreck section resting on a bed of a body of water and including a double-walled hull, which has an outer wall; an inner wall; and a plurality of stiffening ribs.

[0003] A method for salvaging a wreck of a sunken vessel is known from patent GB 140,040. The method disclosed in the above-identified patent includes the steps of making holes in the outer wall of the hull; fixing a numbers of taps to the outer wall by screwing bolts into the outer wall; and raising the wreck by means of lifting lines such as cables, ropes, chains connected to the taps.

[0004] This method has proved to be safe when the outer wall has a sufficient thickness and sufficient structural strength to resists the stresses involved in the lifting step. However, the outer wall of the hull not always provides the sufficient structural strength to support the concentrated stresses determined by the bolts, in particular when the structure of the wreck is wasted by a long permanence in corrosive water such as the salty water. As a consequence, the above-identified method, in many cases, implies a high risk of collapse of the wreck during the lifting step.

[0005] It is self comprehensible that, when the wreck contains environmental hazardous material, any risk of collapse must be avoided.

[0006] The risk of collapse of the wreck is also a function of the size of the wreck. For this reason patent application WO 03/009960 teaches to saw a submarine wreck in small sections by a cable saw operated by two cranes installed on respective vessels. The cable saw is partially wound about the wreck, in particular the cable saw is in contact with the keel and the sides of the wreck. However, the sawing of the wreck and the separation of wreck sections can determine sudden displacements of the wreck sections that are sometime unstably laid on the bed. As a consequence, the environmental hazardous material can leak or loose into the surrounding and contaminate the water and the bed of the body of water.

[0007] One of the objects of the present invention consists in salvaging the wreck by reducing the risk of loosening the hazardous material onboard of the wreck.

[0008] Another object of the present invention consists in avoiding the collapse of the wreck during the lifting step.

[0009] A further object consists in avoiding or limiting to very localised and shallow areas of the bed the works for the preparation to elevation. This mitigates risks of slope soil sliding and undesired displacements of the wreck.

[0010] Another object consists in preventing a further pollution risk determined by parts falling down from wreck during lifting and hazardous material leaking from the wreck.

[0011] According to the present invention there is provided a method for salvaging a wreck containing an environmental hazardous material; the wreck comprising at least a wreck section resting on a bed of a body of water and including a double-walled hull, which has an outer wall; an inner wall; and a plurality of stiffening ribs; the method comprising the steps of forming a number of recesses into the hull; hooking a number of hook assemblies to the hull at said recesses; and lifting the wreck section from the bed of the body of water through said hook assemblies.

[0012] The method according to the present invention does not require the use of bolts, which determine concentrated stresses and calls for a time consuming work to screw them into the outer wall.

[0013] Furthermore, the method according to the present invention does not require particular work on the bed of the body of water.

[0014] The present invention further relates to equipment for salvaging a wreck containing environmental hazardous material.

[0015] According to the present invention there is realized an equipment for salvaging a wreck containing an environmental hazardous material; the wreck comprising at least a wreck section resting on a bed of a body of water and including a double-walled hull, which has an outer wall; an inner wall; and a plurality of stiffening ribs; the equipment comprising means for forming a number of recesses into the hull; means for hooking a number of hook assemblies to the hull at said recesses; and means for lifting the wreck section from the bed of the body of water through said hook assemblies.

[0016] Further technical features and advantages of the invention will be disclosed by the following detailed description of a non-limiting embodiment with reference to the enclosed drawings, wherein:

• Figure 1 is a elevation view, with part removed for clarity, of equipment for salvaging a wreck in accordance to the method of the present invention;
• Figures from 2 to 4 are front elevation views, with part removed for clarity and part in cross-section, of some operating steps of the method of the present invention;
• Figure 5 is a side elevation view, in enlarged scale of a portion, of the wreck;
• Figures 6 and 7 are front elevation views, with part removed for clarity and part in cross-section, of some operating steps of the method of the present invention;
• Figures 8 and 9 are side elevation views, with part removed for clarity, of some operating steps of the method of the present invention;
• Figure 10 is a front view, with part removed for clarity and part in cross-section, of an operating step of the method of the present invention;
• Figure 11 and 12 are side elevation views, with part removed for clarity, of further operating steps of the method of the present invention; and
• Figure 13 is a front elevation view, with part removed for clarity and parts in cross-section, of an operating step of the present invention.

THE WRECK

[0017] In figure 1 with reference numeral 1 is indicated a wreck resting on a bed of a body of water, in particular on a sandy seabed. In the present embodiment the wreck 1 comprises two wreck sections 2 and 3 extending along respective axis A1 and A2. In particular, the body of water is the sea and reference SL indicates the sea level.

[0018] Each one of the wreck sections 2 and 3 comprises a hull 4 comprising, in turn, a keel 5, and two sides 6. The hull 4 is double-walled and comprises an outer wall 7, an inner wall 8; and a plurality of ring-shaped stiffening ribs 9.

[0019] Stiffening ribs 9 are evenly distributed about and along axis A1 respectively A2 and are arranged transversely to axis A1 respectively A2.

[0020] The wreck sections 2 and 3 contain an environmental hazardous material that could contaminate the water and the bed of the body of water.

[0021] Even though the subject matter of the present invention is not limited to a particular type of wreck, it finds a convenient application for salvaging wreck of sunken vessels, in particular submarines. It is rather frequent to discover wrecks of sunken submarines that for several reasons risk of contaminating the water. For example, a wreck belonging to the German submarine U-864 sunken on 9 February 1945, on its way from Germany via Norway to Japan with a cargo of war material was recently discovered by the Norwegian Coastal Ward. According to historical documents, U-864 was carrying about 65 tonnes of metallic (liquid) mercury, stored in steel containers. The wreck of the U-864 was found on 150 meters depth approx 2 nautical miles west of the island Fedje in Hordaland, Norway and was broken into two main wreck sections as a result of a torpedo hit.

EQUIPMENT

[0022] With reference to figure 1, the equipment for implementing the method for salvaging the wreck 1 comprises a vessel fleet 10; lifting equipment 11; an antipollution bag 12; and a number of operational apparatuses.

THE VESSEL FLEET

[0023] The vessel fleet 10 comprises a crane vessel 13; a floating dock barge 14; and a dredged sediments disposal barge 15. The vessel fleet 10 may additional includes support vessel equipped with crane and not shown in the enclosed figures.

[0024] The crane vessel 13 is a large vessel, for example the SAIPEM 7000 or CASTORO 8 of company Saipem S.p.A., and has the purposes of lifting the wreck 1 by means of the lifting assembly 11 and remotely controlling the operational apparatuses. In particular, the crane vessel is provided a high tonnage crane 16.

[0025] The floating dock barge 14 is a semisubmersible barge comprising a dock 17 for housing the wreck 1 without the need of pulling the wreck 1 out from the body water, and a crane 18.

[0026] The dredged soil disposal barge 15 is an ordinary disposal barge for disposing sediments dredged from the bed.

THE LIFTING EQUIPMENT

[0027] With reference to figure 1, the lifting equipment 11 is operated mainly by crane 16 and its lifting line, preferably a cable, a chain or a rope, and comprises a spreader beam 19 having substantially the length of the wreck sections 2 and 3 to be lifted; a number of hook assemblies 20 (figure 8); and a number of slings 21.

[0028] The spreader beam 19 comprises a pipe 22 provided with two end plates 23, each supporting two opposite sheaves 24 as better shown in figure 10 (only two sheaves 24 out of four are shown).

[0029] With reference to figure 6 and 7, each hook assembly 20 comprises a hook 25, a buoyancy block 26, and a flexible elongated element, such as a cable or a rope or a chain, connecting the hook 25 to the buoyancy block 26. The hook 25 is foldable and comprises two expandable clamps 27 and 28.

[0030] In accordance with the present invention, the lifting equipment includes height lifting assemblies 20.

[0031] The hook 25 is made in high strength steel and comprises two articulated portions to let the hook 25 to be folded and reduce its overall size. Preferably, the two portions are articulated trough a universal joint or a two swivel joint.

[0032] Clamps 27 and 28 are forced apart one from the other by mechanical or hydraulic springs so as to selectively allow them expanding from a rest position when the springs are released.

[0033] With reference to figure 1, each sling 21 is wound to a respective sheave 24 and has two free ends suitable to be connected to two respective hook assemblies 20, in particular to two flexible elongated elements of the hook assemblies 20.

[0034] The spreader beam 19 is then connected to the lifting line of the crane 16 of the crane vessel 13 by four line sections, such as chain, cable, or ropes for joining the crane lifting line to the opposite ends of plates 23.

[0035] The spreader beam 19 is used to elevate each wreck section 3, 4. Each sling 21 is connected to the two adjacent hook assemblies 20 on the same side 4 spreading equally the load on them.

[0036] The spreader beam 19 is launched by the crane 16 with the four slings 21.

THE ANTIPOLLUTION BAG

[0037] With reference to figure 1, the antipollution bag 12 avoids or mitigates the risk of loosing debris during the wreck 1 lifting. The antipollution bag 12 comprises a sheet 29, preferably a sheet of thick geotextile reinforced with steel wire mesh; a tubular sealed frame 30, preferably of steel having a rectangular shape (50 m x 10 m); and clump chains 31. The peripheral edges of the sheet 29 are joined to the tubular sealed frame 30 and the clump chains 31 are attached to sheet 29 underneath the sheet 29 so as to confer to the sheet 29 a pocket configuration when the antipollution bag 12 is deployed into the body of water.

[0038] The tubular sealed frame 30 provides a positive buoyant pull of about 200kN to the antipollution bag 12 so that the antipollution bag 12 needs to be deployed on the seabed by clump weights 32 connected to the tubular sealed frame 30 by cables.

THE OPERATIONAL APPARATUSES

[0039] With reference to figure 1, the operational apparatuses include a pair remotely operated vehicle (ROV) 33; an abrasive water jetting machine (AWJM) 34; a pneumatic dredger 35; a hook installation tool (HIT) 36 (figure 6); and an interface skid (IS) 37 (figure 6).

[0040] The operational apparatuses includes also additional apparatuses and tools of know type and not shown in the enclosed figure. Such additional apparatuses are ordinarily used in underwater operations and includes among others a positioning system. The lifting points along the wreck 1 shall be identified with an indicative accuracy of about 0.2-0.5 m; this value ensures for a safe handling. To achieve the above accuracy in the positioning of tools the position system is based on an underwater LBL array. In alternative, a ROV positioning equipment may be used.

[0041] Further additional apparatuses and tools include grinders, cable cutters, saw disc cutters, brushes and hydraulic scissors; all the above mentioned tools are hydraulically powered through the ROV hot stab (not shown) and deployed in a basket (not shown).

[0042] Further auxiliary equipment includes ROV manipulator camera mounted on a bracket that can be easily handled by the ROV 33. This allows performing visual inspection far forward the ROV 33.

THE REMOTELY OPERATED VEHICLE

[0043] With reference to figure 3, the ROV 33 is an underwater vehicle for example like the model Innovator of the company Saipem S.p.A.. The ROV 33 comprises a frame 38, an engine (not shown), and plurality of thrusters (not shown) to control the position of the vehicle into the body of water. The ROV 33 is tethered to the crane vessel 13 (figure 1) that controls the position and the operations of the ROV 33. The frame 38 of the ROV is fitted with a multi-functions grabber (not shown) and a multi-functions manipulator 40. The ROV 33 can be equipped with a plurality of tools and is provided with a male hot stab, and hoses bundle (both not shown), to power the tools with electric current and pressurized fluids. The ROV 33 further includes a camera (not shown), to provide a visual inspection of the underwater scenario.

THE ABRASIVE WATER JETTING MACHINE

[0044] With reference to figure 1, the abrasive water jetting machine 34 comprises an onboard station 41 arranged on the crane vessel 13; an abrasive water jetting tool 42; a buoyancy block 43; and a ballast chain 44 in order to allow having the tool 42 neutrally buoyant in water by adjusting the ballast chain 44. In this way, the ROV 33 can precisely guide the tool 42 on the target points.

[0045] With reference to figure 2, the abrasive water jetting tool 42 comprises a frame 45; a number of electromagnets 46 mounted on the frame for securing the tool to the outer wall 7; a nozzle 47 mounted on the frame 45 with three degree of freedom: the nozzle 47 can be remotely moved in a circle and can be adjusted both the circle radius and the depth. The position of the nozzle 47 is controlled through the ROV 33, which is stabbed on the abrasive water jetting tool 42.

[0046] The abrasive water jetting tool 42 is also provided with sensors and a camera, not shown, arranged on the nozzle 47.

[0047] With reference to figure 1, the onboard station 41 includes substantially a pumping station for delivering the pressurised abrasive water to the abrasive water jetting tool 42 through a dedicated umbilical 48. The umbilical 48 is fitted with an electric cable to power and carry signals to sensors and the camera, not shown, and mounted on the abrasive water jetting tool 42.

THE PNEUMATIC DREDGER

[0048] With reference to figure 1, the pneumatic dredger 35 is, for example, of the type known under the commercial name of PNEUMA ® of the company Pneuma S.r.l. Via di Varlungo 59A - 50136 Firenze - Italy. The pneumatic dredger 35 comprises a compressor 49 arranged on the disposal barge 15; a container 50 arranged at approximately at 70 m depth; and a suction hose 51 connected to the container 50. The pneumatic dredger 35 makes use of the difference of pressure between the container 50 and the seabed to fill the container 60. The compressor 49 pumps air into the container 50 for pushing the sediment up on the disposal barge 15. A valve system, not shown, governs the connection between the suction hose 51 and the container 50 and conduits connecting the compressor 49 and the disposal barge 15 to the container 50. The pneumatic dredger 35 allows dredging sediments at very high density and it is suitable for environmental dredging where low turbidity and low spreading of contaminants are required.

[0049] The container 50 can be connected to more than one suction hose 51. In addition, the final dredging solid concentration is defined by the minimum suctions dredging speed required to drag the soil eventually contaminated by heavy metals. The dredging suction hose 51 is designed to be manoeuvred by using the ROV 33 (figure 10) and includes a large mesh (not shown) on the intake (not shown) to prevent any clogging of the suction hose 51.

THE HOOK INSTALLATION TOOL

[0050] With reference to figure 6, the hook installation tool 36 is operated by the remotely operated vehicle 33 and has the function of hooking the hook assemblies 20 to the hull 4. The hook installation tool 36 is connected to the ROV 33 by means of the interface skid 37.

[0051] The ROV 33 needs to be fitted with an interface skid 37 to allow the mechanical connection to the hook installation tool 36. The interface skid 37 is attached underneath the ROV 33 and is fitted with a docking probe, not shown, to mate with the hook installation tool 36.

[0052] The hook installation tool 36 comprises a clamp operating tool 52; a buoyancy block retainer 53, and a camera (not shown).

THE MAIN OPERATIONAL STEPS OF THE SALVAGING METHOD

[0053] The main operational steps of the salvaging method includes the ordinary preparatory steps like the inspections; structural studies based on the cross checks between the information retrieved from inspections and the design data in many cases still available; FEM analyses; and laboratories analyses of samples of the structure of the wreck 1.

[0054] The current method is based on the principle of lifting separately each wreck section 2, 3 by anchoring the lifting equipment 11 at given lifting points along the structure of one of the wreck sections 2, 3 and lifting the wreck section 2, 3 as shown with reference to figure 10.

[0055] The following description will make specific reference to the salvaging of wreck section 2.

[0056] The intervention procedure makes use of the equipment disclosed in the present descriptions and comprises the following main steps:

• Determine the locations of the lifting points along the hull 4 of the wreck section 2 (figure 1);
• Prepare/clean lifting point locations from debris and soil to have enough room to access to the hull 4.
• Forming a number of recesses into the hull 4 at the lifting points (figures 2 - 5);
• Install the a hook assembly 20 at each recess (figures 6-8);
• Install on the bed the antipollution bag 12 in close proximity of the wreck section 2 to be lifted (figure 1);
• Lift the wreck section 2 off the bed (figure 9 and 10);
• Insert the wreck section 2 in the bag (figure 11);
• Lift the wreck section 2 and the antipollution bag 12 (figure 13) wrapped about the wreck section 2 just below the sea level (operations done by the crane vessel 13 and the dock barge 14 simultaneously).
• Transfer the wreck section 2 together with the antipollution bag 12 in the dock 17 of floating dock barge 14 (operations done by the crane vessel 13 and an eventual crane barge, not shown, and the floating dock barge 14 simultaneously).

[0057] In further details, the selection of the lifting points depends on the size of the wreck 2. in general, the lifting points are selected along the hull 4 and, preferably along each side 6. In accordance with the preferred embodiment of the present invention, each side 6 has a number of lifting points equal to the number of lifting points of the of the opposite side 6.

[0058] Preferably, the lifting points are evenly distributed along each side 6, and the lifting points are in an even number along each side 6. According to the present embodiment the lifting points are eight for each wreck section 2 (four lifting points for each side 6).

[0059] With reference to figures 2 and 4, the recesses are formed into the hull 4 by means of the abrasive water jetting machine 34. In accordance to the present invention and with reference to figure 5, each recess is formed by a first opening 54 into the outer wall 7; a second opening 55 into the inner wall 8; and a slit 56 along the outer wall 8.

[0060] The first and a second opening 54 and 55 are substantially aligned and the first opening 54 is larger than the second opening 55. Preferably, the first opening is a circular opening having a diameter of 400 m. The slit 56 is directed upwardly and extends from the first opening 54 above the first opening 54.

[0061] In use and with reference to figure 1, the abrasive water jetting tool 42 is operated by a ROV 33 and positioned in a given lifting point.

[0062] At the target depth, the ballast chain 44 is adjusted to make the abrasive water jetting tool 42 neutral, then, the ROV 33 grabs and guides the abrasive water jetting tool 42 on the target. With reference to figure 2, electromagnets 46 are then energised to secure it to the outer wall 8 of the wreck section 2.

[0063] Then the abrasive water jetting tool 42 is operated by feeding pressured water from the remote station 41 (figure 1) and controlling the nozzle 47 position by using the ROV 33. The tool 42 cuts the outer wall 7 along a circle (400 mm diameter) just in between two adjacent stiffening ribs 9 (figure 5) and along a number of vertical and horizontal cuts (not shown) within the circle. As the opening 54 on the outer wall 7 is cut, the electromagnets 46 are first de-energised, and, then, the tool 42 is recovered. With reference to figure 3, the ROV 33 with the aid of the auxiliary tools, not shown, tears up and cuts patches and removes all steel works between the outer wall 7 and the inner wall 8 to expose the inner wall 8.

[0064] With reference to figure 4, the abrasive water jetting tool 42 is launched again, as before is installed on the lifting point location, and is operated by the ROV 33 to cut the inner wall 8 along a circle and a number of vertical and horizontal cuts (not shown) within the circle. Once the second opening 55 is cut the abrasive water jetting tool 42 is recovered. ROV 33 inspects the second opening 55 by using the ROV manipulator camera and eventually inserts the manipulator 40 into the second openings 55 to clean it. The above sequence is repeated for the remaining seven lifting points. Further on, the nozzle 47 of the abrasive water jetting tool 42 is guided along a rectilinear path in order to cut a slit 56 into the outer wall 7 so as to complete the recess and determine the configuration show in figure 5. As an alternative, other ordinary cutting tools (not shown) can be used by the manipulator 40 to cut slit 56.

[0065] Two hook assemblies 20 are deployed on the bed by the crane vessel 13 together with a hook deployment frame not shown in the enclosed figures. With reference to figure 6, the ROV 33 docks on a hook assembly 20 and moves to install the hook assembly 20 in one of the recesses.

[0066] In particular, the insertion of the hook assembly 20 into a recess is assisted by a camera, not shown so as to arrange clamp 27 about an edge of the inner wall 8 at the opening 55. When clamps 27 and 28 are arranged on a target position the clamp operating tool 52, which is remotely controlled through ROV 33, releases the clamps 27 and 28 that are spaced apart and expand against opposite edges of the opening 55 in the inner wall 8 (figure 7). The ROV 33 provides also for operating the buoyancy block retainer 53 so as to release the buoyancy block 26.

[0067] The flexible elongated element connecting the buoyancy block 26 and the hook 25 has the tendency to assume a vertical configuration. The ROV 33 provides for inserting each flexible elongated element into a respective slit 56. The operation is repeated for the insertion of the remaining hook assemblies 20 into the remaining seven recesses. Once all the hook assemblies 20 are hooked to the hull 4 of wreck section 2, two ROVs 33 are coupled to the suction nozzles of respective suction hoses 51 of the pneumatic dredger 35 for cleaning a target area for landing the antipollution bag 12.

[0068] The antipollution bag 12 is positioned by crane 16 with the sheet 29 in a folded configuration. When the clump weights 32 rest on the bed the antipollution bag 12 is released from the crane 16, the sheet 29 is unfolded, and the clump chain 31 arranged underneath the sheet 29 draws the sheet 29 so as to let the sheet 29 to assume a pocket configuration. The next step consists in positioning the spreader beam 19 by means of crane 16 over the wreck section 2 and joining each lifting assembly 20 to a free end of a sling 21. Preferably, two adjacent hook assemblies 20 hooked on the same side 6 of the hull 4 are joined to the two opposite ends of a same sling 21. When all hook assemblies 20 are joined to the spreader beam 19 by means of the four slings 21, the wreck section 2 can be lifted as shown in figure 9. During the lifting the ROVs 33 operate the suction hose 51 so as to suck the soil in proximity of the wreck section 2, as shown in figure 10, in order to ease the lifting and avoid a possible contamination determined by an eventual leakage of the hazardous material.

[0069] With reference to figure 11, the wreck section 2 is lifted and positioned over the antipollution bag 12 and, thus, is inserted into the antipollution bag 12. The two ROVs 33 are fitted with the wire cutters, not shown, so as to cut cables connecting clump weights 32 to the tubular sealed frame 30, which is provided with a positive buoyancy pull. As a consequence of the positive buoyancy pull of the antipollution bag 12, the sheet 29 wraps about the keel 5 and the sides 6 of hull 4. The wreck section 2 is lifted below the sea level, and the antipollution bag 12 follows the wreck 2; the lifting is assisted by two ROVs 33. Finally the wreck section 2 and the antipollution bag 12 are moved into the dock 17 of the floating dock barge 14 in a configuration not shown in the enclosed drawing.

[0070] The same operations performed for wreck section 2 are repeated for the wreck section 3.

[0071] It is intended that many modification can be implemented in the present invention without departing form the scope on the invention defined by the following claims.

Claims

1. Method for salvaging a wreck containing an environmental hazardous material; the wreck (1) comprising at least a wreck section (2; 3) resting on a bed of a body of water and including a double-walled hull (4), which has an outer wall (7); an inner wall (8); and a plurality of stiffening ribs (9); the method comprising the steps of forming a number of recesses (54, 55, 56) into the hull (4); hooking a number of hook assemblies (20) to the hull (4) at said recesses (54, 55, 56); and lifting the wreck section (2; 3) from the bed of the body of water through said hook assemblies (20).

2. Method for salvaging a wreck according to claim 1, wherein the hull (4) comprises a keel (5) and two sides (6); the method being characterised by forming said recesses (54; 55; 56) along both sides (6); preferably the number of recesses (54; 55; 56) along one side (6) is equal to the number of recesses (54; 55; 56) along the other side (6) and, more particularly, the number of recesses (54; 55; 56) along each side (6) is an even number.

3. Method for salvaging a wreck according to claim 1 or 2, characterized in that the step of forming the number of recesses (54, 55, 56) includes for each recess (54, 55, 56) cutting a first openings (54) into the outer wall (7), and cutting a second opening (55) into the inner wall (8); said hook assemblies (20) being hooked to the inner wall (8); wherein each first opening (54) is aligned to a second opening (55); preferably, the first opening (54) is larger than said second opening (55).

4. Method for salvaging a wreck according to claim 3, characterised in that the step of forming the number of recesses (54, 55, 56) further includes for each recess (54, 55, 56) cutting a slit (56) into the outer wall (7); said slit (56) extending upwardly from said first opening (54).

5. Method for salvaging a wreck according to claim 4, characterised in that each hook assembly (20) comprises a hook (25); a buoyancy block (26); and a flexible elongated element linking the hook (25) to the buoyancy block (26); the method including the step of inserting the hook (25) into the first and the second openings (54, 55) and the flexible elongated element into the respective slit (56).

6. Method for salvaging a wreck according to claim 5, characterised in that said hook (25) comprises two articulated portions; preferably said articulated portions are articulated by a universal joint or two swivel joints.

7. Method for salvaging a wreck according to claim 5 or 6, characterised by clamping said hook (25) to the inner wall (8) at said second opening (55); said hook (25) comprising two opposite expandable clamps (27, 28).

8. Method for salvaging a wreck according to any one of the foregoing claims, characterised by joining each hook assemblies (20) to a spreader beam (19) by means of slings (21); preferably each sling (21) is wound about a sheave (24) supported by the spreader beam (19) and is joined at its opposite ends to two adjacent hook assemblies (20).

9. Method for salvaging a wreck according to any one of the foregoing claims, characterised by installing an antipollution bag (12) in a pocket shaped configuration onto the bed of the body of water in proximity of the wreck section (2; 3); lifting the wreck section (2; 3) and introducing the wreck section (2; 3) into the antipollution bag (12); the antipollution bag (12) being so sized so as to contain the wreck section (2; 3).

10. Method for salvaging a wreck according to claim 9, characterised by lifting the wreck section (2; 3) together with the antipollution bag (12) so as to confine into the antipollution bag (12) any material loosened or detached from the wreck sections (2; 3).

11. Method for salvaging a wreck according to claim 10, characterised in that the antipollution bag (12) comprises a sheet (29) joined to a tubular sealed frame (30) providing a positive buoyancy pull.

12. Method for salvaging a wreck according to anyone of the foregoing claims, characterised by cutting the outer wall (7) and inner wall (8) by an abrasive water jetting tool (42) operated by a remotely operated vehicle (33).

13. Equipment for salvaging a wreck containing an environmental hazardous material; the wreck (1) comprising at least a wreck section (2; 3) resting on a bed of a body of water and including a double-walled hull (4), which has an outer wall (7); an inner wall (8); and a plurality of stiffening ribs (9); the equipment comprising means for forming a number of recesses (54, 55, 56) into the hull (4); means for hooking a number of hook assemblies (20) to the hull (4) at said recesses (54, 55, 56); and means for lifting the wreck section (2; 3) from the bed of the body of water through said hook assemblies (20).

14. Equipment for salvaging a wreck according to claim 13, characterized in that means for forming a number of recesses (54, 55, 56) comprises an abrasive water jetting machine (34) comprising an abrasive water jetting tool (42) operated by a remotely operated vehicle (33) for cutting said recesses (54, 55, 56) into the hull (4); each recess (54, 55, 56) comprising a first openings (54) into the outer wall (7), a second opening (55) into the inner wall (8), and a slit (56) into the outer wall (7); said slit (56) extending upwardly from said first opening (54); each first opening (54) is aligned to a second opening (55); preferably, the first opening (54) is larger than said second opening (55).

15. Equipment for salvaging a wreck according to claim 14, characterised in that each hook assembly (20) comprises a hook (25) having two opposite expandable clamps (27, 28); a buoyancy block (26); and a flexible elongated element linking the hook (25) to the buoyancy block (26); said means for hooking comprising a hook installation tool (36) having a clamp operating tool (52) and buoyancy block retainer (53).

16. Equipment for salvaging a wreck according to claim 5, characterised in that said hook (25) comprises two articulated portions trough an articulation; said articulation comprising a universal joint or two swivel joints.

17. Equipment for salvaging a wreck according to any one of the claims from 13 to 16, characterised by comprising a lifting equipment (11) including said hook assemblies (20); a spreader beam (19); and a number of slings (21), wherein each sling (21) is wound about a sheave (24) supported by the spreader beam (19) and is joined at its opposite end to two adjacent hook assemblies (20).

18. Equipment according to any one of the claims from 13 to 17, characterised by comprising an antipollution bag (12) suitable to be installed in a pocket shaped configuration onto the bed of the body of water in proximity of the wreck section (2; 3) and so sized so as to contain the wreck section (2; 3).

19. Equipment for salvaging a wreck according to claim 18, characterised in that the antipollution bag (12) comprises a sheet material (29) joined to a tubular sealed frame (30) providing a positive buoyant pull.

Drawing