EP3894315B1

EP3894315B1 - A shipwreck salvaging floating service base and a method of salvaging a shipwreck

Info

Publication number: EP3894315B1
Application number: EP19845623.8A
Authority: EP
Inventors: Bernt HELLESØE
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-12-14
Filing date: 2019-12-16
Publication date: 2024-09-25
Anticipated expiration: 2039-12-16
Also published as: EP3894315A1; WO2020122735A1; NO20181613A1; NO345458B1

Description

The present invention was specifically developed to retrieve submarine U-864 that sank February 9, 1945 and that is located at the seabed at 150m depth off the western coast of Norway, but can be utilized for other salvaging purposes. This specific submarine is broken in two parts and contains 65 tons of mercury. The submarine must therefore be handled with extreme care to recover all the mercury as the mercury represent a considerable threat to the environment. The submarine is located in the North Sea and the weather and wave conditions pose a considerable challenge for careful recovery.
Various solutions for careful recovery of shipwrecks are suggested in the prior art, but none of these have been considered to be sufficiently reliable and safe in the governing offshore conditions.
US 2010/0162935 discloses a catamaran lifting apparatus for lifting objects in a marine environment. The apparatus includes first and second vessels that are spaced apart during use. A first and a second frame spans between the vessels. The frames are spaced apart and connected to the vessels in a configuration that spaces the vessels apart.
EP 2 106 997 disclose a method and equipment for salvaging a wreck containing an environmental hazardous material. The wreck has a wreck section that rests on a bed of a body of water and is provided with a double-walled hull with an outer wall, an inner wall, and a plurality of stiffening ribs. A method for salvaging the wreck includes forming several recesses into the hull, hooking a number of hook assemblies to the hull at the recesses, and lifting the wreck section through the hook assemblies.
The present invention therefore provide a solution to ensure safe salvage of shipwrecks and other fragile objects from the seabed.
The present invention thus relates to a shipwreck salvaging floating service base with a service base hull. The service base comprise a moon pool, a portal crane movable above and along the moon pool, a winch assembly with at least four sway compensating and hoisting individual winches, each with a winch cable aligned and extending down from a top portion of said portal crane, and an active extendable termination head secured to each of the winch cables. The extendable termination head is sway compensating, mechanical shock alleviating, load balancing, and includes an active, powered heave compensating system. Each active extendable sway compensating termination head is adapted to be connected to attachment elements secured to a shipwreck.
The moon pool may include an open end, whereby a vessel can sail in or out of the moon pool.
An opening and closing gate may be located across the open end of the moon pool.
The opening and closing gate across the open end of the moon pool may be fixed across the open end and may increase the mechanical strength of the service base hull.
The floating service base may further comprise a dock port at an end of the floating service base, and the portal crane may be movable along rails between a position above the moon pool and a position above the dock port.
Each of the at least four winch drums of the winch assembly may be driven with a substantially gearless permanent magnet motor (61).
Each of the active termination heads may include a hydraulic cylinder and a pressure regulating overload valve forming a mechanical shock alleviating and load balancing termination head.
Each of the termination heads may be communicating through signals with its respective winch whereby each winch and respective termination head cooperate to provide sway compensation to prevent overloading each attachment element.
Bottom gates may be provided to close the moon pool at the bottom of the hull of the floating service base, whereby the moon pool and the bottom gates form a dry dock when the bottom gates are closed.
The floating service base may further include a DPS.
The floating service base may be connected to a subsea tool station with at least a milling / sawing system, a drilling system and a shipwreck attachment system.
The subsea tool station may form a part of a ROV.
Furthermore, the invention relates to a method of salvaging a shipwreck with a floating service base as described above. The method comprise the steps of: locating a floating service base above a shipwreck to be salvaged, launching a ROV and at least one tool station with at least one of an attachment elements securing system, a sawing system and a drilling system, attaching at least four attachment elements to the shipwreck with the attachment elements securing system, providing at least four mechanical shock alleviating termination heads, setting mechanical load limits for each mechanical shock alleviating termination head, lowering the at least four mechanical shock alleviating termination heads each connected to a lifting cable secured to a separate winch drum, securing one termination head to each of the attachment elements, operating each of the winches connected to the winching cables within the set mechanical load limits for each mechanical shock alleviating termination head, lifting the shipwreck while monitoring the mechanical tension exposed to each attachment element in each termination head to ensure that the mechanical load for each mechanical shock alleviating termination head is within the set mechanical load limits, and lifting the shipwreck on-board the floating service base.
The step of attaching at least four attachment elements to the shipwreck with the attachment element securing system may involve sawing through an outer structure of the shipwreck with the sawing system of the tool station, drilling a hole for each attachment element through an inner structure of the shipwreck with the drilling system of the tool station, and securing one attachment element in each of the drilled holes.
The method may further include halting the lifting of the shipwreck just above the seabed and covering the shipwreck with a cover before commencing lifting the shipwreck onto the floating service base.
The step of lifting the shipwreck on-board the floating service base may include lifting the shipwreck through a moon pool in the floating service base, closing the moon pool with bottom gates at each side of a bottom of the moon pool of the floating service base, and pumping water out of the moon pool to form a dry dock.
Each of the winch drums may be secured to a portal crane lift movable along rails, and wherein the step of lifting the shipwreck includes moving the portal crane lift with the shipwreck along the along rails into a dock port of the floating service base.
Short description of the enclosed drawings:

Fig. 1a, 1b, 1c, are schematic representations of a shipwreck salvaged according to an embodiment of the invention;
Fig. 2 is a schematic representation of an attachment element and a termination head;
Fig. 3 is a schematic representation of a ROV;
Figs. 4a-4c show a floating service base from the side, the front and partly from above respectively; and
Fig. 5 is a schematic representation of a winch assembly partly in cross section.

Fig. 1a is a schematic representation of a shipwreck 1 in the form of a submarine to be retrieved and salvaged from a seabed. The shipwreck 1 includes a load / cargo 2, an inner pressure hull 3 and an outer hull 4. Outer hull openings 9 are cut out of the outer hull 4 to gain access to strong attachment points on the pressure hull 3. Five attachment elements 7 are located in line with each other and are adapted to be secured to five active termination heads 6 forming mechanical shock alleviating, load balancing and sway compensating elements suspended in five lifting cables 5. The five attachment elements 7 are secured along a centre line in a longitudinal direction of the shipwreck.
A spacer bar 8 maintains the distance between the five lifting cables 5 and simplifies the connecting operation of the five attachment elements 7 and the five active, energized, mechanical shock alleviating, termination heads 6. The spacer bar 8 includes five lifting cable gripping assemblies 52. Each of the five lifting cable gripping assemblies 52 includes a cable gripping element and an actuator for the cable gripping element. The cable gripping assemblies grips or releases each lifting cable form the spacer bar 8 upon signals from a floating service base. One or several of the lifting cables can include mechanical stopping elements providing outer limits for the movement of the spacer bar in relation to the lifting cables 5.
Fig. 1a shows a half submarine as shipwrecks 1 on occasions are incomplete. The load 2 influences the balance of the shipwreck and is also essential to recover. One or several reference transponders 23 with fixed locations in relation to the shipwreck 1 provide signals to locate the termination heads 6.
In addition to what is shown on fig.1a, fig. 1 b shows a packed cover or tarpaulin 50 that can be used to be packed around the shipwreck 1 to cover the shipwreck 1 to reduce loss, and control pollution from the shipwreck. The cover can also be a reinforced cover that can be used to carry parts of, or all the load of the weight of the shipwreck, and the cover can be attached to the termination heads 6 to allow the mechanical load to be transferred from the lifting cables to the cover. In the embodiment on fig. 1b, the cover is attached and packed along the length of the spacer bar 8. One way of packing the cover includes rolling the cover 50 around a boom and unrolling the cover when it is needed. An ROV can pull the cover 50 around the shipwreck and attach the cover to the opposite side of the spacer bar 8. The end portions can include elements allowing the ends to be sealed.
In Fig. 1c the cover 50 of Fig. 1b is surrounding and covering the shipwreck. The covered shipwreck 51 can then be lifted to the surface.
In the event the cover is used to reduce pollution or there is a risk that valuable objects will be washed out of the shipwreck, the cover must be as sealed as possible, and the water inside the cover must then be brought to the surface, be pumped out, and be safely disposed of or checked.
In the event the cover only is used to carry mechanical loads, the water inside the covered shipwreck 51 can be allowed to run out of the shipwreck and the cover when the shipwreck is lifted onto a floating service base. The five lifting cable gripping assemblies 52 can be in a gripping mode to hold the spacer bar 8 in place.
Fig 2 is a schematic representation of an attachment element 7 and a termination head 6.
The attachment element 7 is fixed to the inner pressure hull 3 with threads cut into the hull. Alternatively, the attachment element 7 can be welded to the hull or may include expanding locking dogs that can expand inside the hull. The hull may have to be reinforced around the attachments for instance by welding a reinforcement plate onto the hull 3 to increase the material thickness at the attachment point. The attachment element 7 includes a locking geometry, mating with a latching mechanism 10 on a dynamic portion 20 of the termination head 6.
The latching mechanism 10 may include an automatic locking and releasing assembly with an ROV operated override and may include a separate, externally accessible release element 28 to allow the latching mechanism 10 to be locked or released by an ROV or a diver. A casing of the latching mechanism 10 may include an external mechanical handling body 27 to allow an ROV or a diver to grip and handle the casing.
The dynamic portion 20 includes a flexible or articulated inclination element 11 or misalignment joint allowing the termination head 6 to articulate up to 12,5° by side pull in relation to the hull 3. The dynamic portion 20 is movable in relation to a main body 21.
The termination head 6 includes a load cell 16 monitoring the mechanical load transferred from the cable or umbilical 5 and to the dynamic portion 20. Furthermore the termination head 6 includes a sensor 15 monitoring the position of the dynamic portion 20 in relation to the main body 21. A position sensor 14 monitors a position of the termination head 7 in relation to the other termination heads 6 and in relation to the shipwreck. One or several position reference transponders (ref 23 on fig. 1) may be installed on the shipwreck to communicate with the position sensor 14 of each termination head 6 for accurate manoeuvring of the termination heads 6. The termination head 6 includes motion and inclination sensors 17 for control of the dynamic element 20. The termination head 6 includes an active, powered heave compensating system 18 powering motion of the dynamic element 20. The active, powered heave compensating system 18 may be hydraulic, the dynamic element 20 may include a double acting piston 13, and the main body 21 may then constitute a hydraulic cylinder. The double acting piston 13 can be held in an intermediate resting position, for instance 1/3 of a total stroke from the top by a spring 27.
The powered heave compensating system 18 can furthermore include an electrohydraulic power unit (EHPU) 26 connected to piping to operate the double acting piston 13 in the hydraulic cylinder. The EHPU, the hydraulic cylinder with the double acting hydraulic piston 13 form a hydraulic circuit that also includes a pressure compensated hydraulic fluid chamber 25 to accommodate variations in volume of the hydraulic circuit.
The termination head 6 includes an overload safety relief valve 24 and tension pressure sensors.
The load cell 16 is a pressure sensor monitoring the pressure inside the hydraulic cylinder. The attachment element 7 includes a bore 12 to provide access into the hull 3. The bore 12 may be used for filling the hull with air/gas to increase the buoyancy of the hull or may be used to insert monitoring equipment such as cameras, water sampling or water contamination measuring equipment into the hull. The dynamic element 20 and the cable 5 may include a passage 22 for air/gas or for conveying monitoring equipment. The cable is designed as an umbilical 5 that may include signalling cables and power cables to convey signals to topside controls and topside lifting system on a floating service base. The termination heads 6 include an automatic safety system with a manual override function, and the termination heads 6 may communicate with the topside service base through the cables or through a separate cable system (not shown).
Fig. 3 is a schematic representation of a ROV 30 with a propulsion system 31, a navigation system 32, a shipwreck attachment system 33, a tool station with a milling / sawing system 34 a drilling and machining / threading system 35, a welding system 36 and a vision system 37. The ROV may be attached through an umbilical 38 to a floating service base directly or through a separate station at the seabed.
The navigation system 32 may communicate with the reference transponder (ref no 23 on fig. 1) to facilitate accurate positioning of the ROV in relation to the shipwreck.
The propulsion system 31 allows accurate positioning of the ROV based on input from the navigation system 32 and manual input based on information from the vision system 37.
The shipwreck attachment system 33 allows accurate positioning of the tool station in relation to the shipwreck during machining and can be based om fixed magnets, electromagnetism, mechanical fasteners penetrating into a structure of the shipwreck, clamps etc.
The milling/sawing system 36 (subsea milling centre, SSMC) allows a tool station of the ROV to saw through the outer hull to find solid attachment points on the inner hull. In the event the shipwreck not is a vessel with a strong inner hull, then the milling/sawing system 36 can be used to mill / saw through the outer structure to find strong structures inside the outer hull. The mill / sawing system 36 may include traditional mills, circular sawing blades or a diamond wire saw.
The drilling system 35 includes a drill to drill through the shipwreck or the inner hull to provide holes for the attachment elements. The drilling system 35 may also include tools to provide threads in the inner hull to secure the attachment elements.
The welding system 36 may be used to reinforce the inner hull or the shipwreck in the area around the attachment elements to provide secure fixing points for the attachment elements.
In an alternative embodiment, the tool station and the ROV are separate units, and the ROV can then be used to navigate the tool station to the right position on the shipwreck.
Figs. 4a-4c show a floating service base 40 or floating marine base (UFMB) / barge /vessel with min 12.000 tonnage dead weight with dry dock 44 in one end from the side, from the front and partly from above respectively. The dry dock 44 has closable bottom gates 45 in the bottom. A dock port 41 with a dock port hangar is located at the end opposite the dry dock 44. The dock port 41 and the dry dock 44 enables the floating dock port to salvage several units, as a unit can be unloaded in the dock port 41 before a new unit is salvaged.
Fig. 4a and 4b show a salvage marine portal crane lift 42 equipped with railway car bogies 47 running on rails 48 over the dry dock 44 and can be locked down with heavy duty hydraulic rams. The 1000 ton salvage marine lift 40 is equipped with a winch assembly 43 with five integrated winch drums with internal PM (Permanent Magnet) motors. Each drum contains an integrated composite lift cable 5 with air supply, fibre optic, signal cables and power. The individual drums are heave & tension compensated with a built-in safety and measuring cylinder (SAM-C) at the lower end. Each SAM-C and topside drum are interconnected through common software, forming the total overall control system which is capable of "laptop operation & control". The termination heads 6 communicate with the floating service base through the integrated composite lift cable 5, and the individual drums operating the individual cables 5 can be adjusted based on parameters supplied by the individual termination heads.
Azimuth thrusters 50 form a part of a DPS (dynamic positioning system). The shipwreck 1 is suspended in the individual cables 5 and the termination heads 6 until the portal crane 42 moves the shipwreck 1 along the rails 48 into the dock port 42 and unloads the shipwreck 1. A ballasting system maintains the balance of the floating service base 40.
The distance between the salvage marine portal crane lift 42 and the shipwreck 1 is sufficient to allow room for the termination heads 6.
The closable, hinged bottom gates 45 allow the shipwreck to be winched through the hull of the floating service base 40 before the bottom gates 45 are closed and the water left inside the dry dock 44 is pumped out. A moon pool is defined in the floating service base 40 when the hinged bottom gates 45 are open.
The railway car bogies 47 include railway wheels and are adapted to the rails or tracks 48 allowing the salvage marine portal crane lift 42 to run between the dry dock 44 and the enclosed dock port 41. The railway wheels can be powered to move the salvage marine portal crane lift 42. Winches may alternatively pull the salvage marine portal crane lift 42 along the rails 48. The rails 48 can be designed to prevent the railway car bogies 47 from derailing in severe weather conditions.
Fig. 4c shows the moon pool part of the floating service base 40 partly from above. The salvage marine portal crane lift running on rails or tracks 48 and the enclosed dock part 41 are omitted. The moon pool 49 is formed in the floating service base 40 when the bottom gates 45 are open and a front gate 39 actuated by actuating and locking elements 29 is closed. The moon pool 49 can be opened at one end by opening the front gate 39 to allow vessels to sail in and out of the moon pool 49. Water can be pumped out of the moon pool 49 when the gates are closed. At least the front gate 29 can be thoroughly secured to the front of the moon pool, thus increasing the strength of the floating service vessel 40 in the moon pool area. A dedicated reinforcement barge (not shown) can be sailed through the front gate 39 and into the moon pool 49. The barge can then be fixed rigidly to the floating service base 40 for further strength.
Fig. 5 is a schematic representation of the winch assembly 43 partly in cross section and in further detail. The winch assembly 43 includes an upper suspension beam 60 holding six winch support units 67. The winch support units 67 are suspended in a longitudinal beam 60. The slip ring and bearing units 67 support five winch drums 62 with winch cable 5 guiding grooves. Each winch drum 62 is driven by an individual electric permanent magnet motor 61 inside each winch drum 62. A drive shaft 64 from each permanent magnet motor 61 is fixed to an inner driving bulkhead 64 in each winch drum 62. A bearing and slip ring unit 68 inside each of the six winch support units 67 allows the cables 5 to include ducts for hydraulic fluids, for air or gas, signal lines and power lines. A holding portion 63 holds each winch support unit 67 to the longitudinal beam. The winch cable is typically only wound in one layer around the winch drum to reduce the risk of cable jamming and to facilitate the sway compensating motion of the winch drums.

The Operation itself:

Provide the operation tools (vessels and equipment); cut out requires top sections of outer casing in preparation for access to main hull; produce fixed lifting point to main sub hull; Install 1" lances for introducing air underneath hull; hook up lifting lances (wire with 200ton quick connect) to the fixed lifting points on main pressure hull; start the procedure for lifting; as soon as hull has cleared bottom with 2m, stop and install heavy duty canvas; continue lifting operation under ROV HD camera surveillance and control systems; slowly recover sub throughout splash zone permitting slow ample draining of seawater from hull; after throughout visual inspection, lift sub to top position; extensive inspection; raise sub into hanger hanging from marine salvage lift.
Secure sub for transport lowering it onto soft pillows; repeat operation for sub half #02, but support it on soft pillows inside the closed dock of the floating marine base (UFMB); the UFMB is now sailing to deep water marine base at; The UFMB is mooring and connecting to dock; connecting UFMB rail system to the dock rail system; the UFMB can now travel onto and over the dock with submarine part #02 hanging in the marine lift; lowering of sub half #02 onto soft pillow structure; removal of cargo (mercury in keel and possibly explosives).

Claims

A shipwreck salvaging floating service base (40) with a service base hull comprising:
a moon pool (49);

a portal crane (42) movable above and along the moon pool (49);

a winch assembly with at least four sway compensating and hoisting individual winches, each with a winch cable (5), aligned and extending down from a top portion of said portal crane (42); and

an active extendable termination head (6) secured to each of the winch cables (5), wherein each active extendable termination head (6) is adapted to be connected to attachment elements (7) secured to a shipwreck (1).
The floating service base (40) of claim 1, wherein the moon pool (49) includes an open end, whereby a vessel can sail in or out of the moon pool (49).
The floating service base (40) of claim 2, further including an opening and closing gate (39) across the open end of the moon pool (49).
The floating service base (40) of claim 3, wherein the opening and closing gate (39) across the open end of the moon pool (49) is fixed at across the open end and increases the mechanical strength of the service base hull.
The floating service base (40) of one of the preceding claims, further comprising a dock port (41) at an end of the floating service base (40), and wherein the portal crane (42) is movable along rails (48) between a position above the moon pool (49) and a position above the dock port (41).
The floating service base (40) of one of the preceding claims, wherein each of at least four winch drums (62) of the winch assembly (43) is driven with a substantially gearless permanent magnet motor (61).
The floating service base (40) of one of the preceding claims, wherein each of the active extendable termination heads (6) include a hydraulic cylinder and a pressure regulating overload valve (24) forming a mechanical shock alleviating and load balancing termination head.
The floating service base (40) of one of the preceding claims, wherein each of the active extendable termination heads (6) is in communication with its respective winch whereby each winch and respective active extendable termination head (6) cooperate to provide sway compensation to prevent overloading each attachment element (7).
The floating service base (40) of any of the preceding claims, wherein bottom gates (45) are provided to close the moon pool (49) at the bottom of the hull of the floating service base (40), whereby the moon pool (49) and the bottom gates (45) form a dry dock (44) when the bottom gates (45) are closed.
The floating service base (40) of any of the preceding claims, further including a DPS.
The floating service base (40) of any of the preceding claims connected to a subsea tool station with at least a milling / sawing system (34), a drilling system (35) and a shipwreck attachment system (33).
The floating service base (40) of claim 11, wherein the subsea tool station forms a part of a ROV (30).
A method of salvaging a shipwreck (1) with a floating service base (40) of one of the preceding claims, comprising the steps of:
locating a floating service base (40) above a shipwreck (1) to be salvaged;

launching a ROV and at least one tool station with at least one of an attachment elements securing system, a sawing system (34) and a drilling system (35);

attaching at least four attachment elements (7) to the shipwreck (1) with the attachment elements securing system;

providing at least four active extendable termination heads (6);

setting mechanical load limits for each termination head (6);

lowering the at least four mechanical active extendable termination heads (6), each connected to a lifting cable (5) secured to a discrete winch;

securing one active extendable termination head (6) to each of the attachment elements (7);

operating each of the winches connected to the winching cables within the set mechanical load limits for each active extendable termination head (6);

lifting the shipwreck while monitoring the mechanical tension exposed to each attachment element in each active extendable termination head to ensure that the mechanical load for each active extendable termination head (6) is within the set mechanical load limits; and

lifting the shipwreck (1) on-board the floating service base (40).
The method of claim 13, wherein the step of attaching at least four attachment elements (7) to the shipwreck with the attachment element securing system involves sawing through an outer structure of the shipwreck (1) with the sawing system (34) of the tool station;
drilling a hole for each attachment element (7) through an inner structure of the shipwreck (1) with the drilling system (35) of the tool station; and

securing one attachment element (7) in each of the drilled holes.
The method of claim 13 or 14, further including halting the lifting of the shipwreck (1) just above the seabed and covering the shipwreck (1) with a cover (50) before commencing lifting the shipwreck (1) onto the floating service base (40).
The method of claim 13, 14 or 15, wherein the step of lifting the shipwreck (1) on-board the floating service base (40) includes lifting the shipwreck (1) through a moon pool in the floating service base (40);
closing the moon pool (49) with bottom gates (45) at each side of a bottom of the moon pool (49) of the floating service base (40); and

pumping water out of the moon pool (49) to form a dry dock (44).
The method of claim of one of the preceding claims 13-16, wherein each of the winches are secured to a portal crane lift (42) movable along rails (48), and wherein the step of lifting the shipwreck (1) on-board the floating service base (40) includes moving the portal crane lift (42) with the shipwreck (1) along the along rails (48) into a dock port (41) of the floating service base (40).