Total crane height reduction of a tub mounted crane.

Abstract

Method for reducing a total crane height and a vessel crane 1 comprising a lowering mechanism 5 for lowering a gantry 4 to achieve a total crane height reduction. The gantry 4 is collapsible from a raised position RP to a lowered position LP. The gantry has a front framework 40 and a rear framework 41. In the raised position RP, the rear framework 41 is at a base connected to a rear base mount at the crane house. In the lowered position LP, the rear framework 41 is disconnected and displaced. The lowering mechanism has a lock system 51 for disconnecting the rear framework 41 and a pivotal link framework 50 for subsequently guiding the rear framework 41 during its displacement. Fig. 4

Description

P37003NL00 / KHO Title: Total crane height reduction of a tub mounted crane. The invention relates to a tub mounted crane and a method for reducing a total crane height of a tub mounted crane. One of worlds largest crane vessels is known as the Saipem 7000. This crane vessel is configured for heavy lifting. This crane vessel has two fully revolving bow mounted cranes which are each capable of lifting 7000 tonnes. The cranes have each a substructure formed by a pedestal, a so-called tub, and a revolving superstructure provided with operating machinery. The Saipem 7000 has a semi-submersible design which allows it to partially submerge in water. By pumping water in or out of ballast tanks, the vessel can adjust its height in the water. This height adjustment capability serves to improve stability during heavy lifting operations and in case provides an ability to pass under bridges or other obstacles during transit. In particular situations, this height adjustment is not sufficient. For example, to pass through the Panama Canal or the Bosporus Strait, it is desired to further reduce the total height of the cranes of the Saipem 7000. Several similar crane structures are known from the prior art which allow a lowering of a gantry of a vessel crane. By lowering the gantry, a total crane height during travelling is reduced. EP3.825.274 in the name of Liebherr discloses an offshore crane including an A-shaped gantry formed by a pivotable front framework and a pivotable rear framework for elevating and lowering a boom. The rear framework is here called an erecting trestle. The gantry has a total height which determines a maximum height of the crane for passing an obstacle. The rear framework of the gantry is collapsible to reduce this maximum height. The rear framework of the gantry is built out of a lower framework section and an upper framework section which are interconnected by a rotaryjoint. A relative pivotal movement of the sections is operable by a retracting mechanism. By retracting the lower framework section, the framework sections pivot and the rotaryjoint moves in a direction opposite to the boom. In an erected position, the rotaryjoint is locked by a lockage which is formed by a hydraulic cylinder in order to fixate the upper and lower framework sections. _ 2 _ Another embodiment of a collapsible gantry of an offshore tub mounted crane is disclosed in WO 2020 / 204719 in the name of ltrec. In this embodiment, the gantry also has a collapsible rear framework out of two framework sections. Here, the rear framework is collapsible in a boom direction. A drawback of these collapsible gantries is that despite the presence of the lockage, the rotary joint between the sections ofthe rearframework reduces a robustness of the gantry. The rotary joint forms a weakening of the gantry and should be sufficient strengthened by the lockage. Regarding the above-mentioned prior art, it is remarked that any discussion ofdocuments, acts, materials, devices, articles or the like included in the present specification is for the purpose of providing a context for the present invention, and is not to be taken as an admission that any such matters form part of the prior art orwere common general knowledge in the field relevant to the present invention before the priority date of each claim of this application. The general object ofthe present invention is to at least partially eliminate the above mentioned drawback and / or to provide a usable alternative. More specific, it is an object of the invention to provide a reduction of a total crane height without or minimally compromising a robustness of the crane. According to the invention, this object is achieved by a vessel crane, in particular a tub mounted crane, as defined in claim 1. According to the invention, a vessel crane is provided which is suitable for transferring a hoist load to and fro a marine vessel, a barge, a jacket or another structure. The vessel crane comprises a substructure on which a superstructure is mounted. The superstructure comprises operating machinery to carry out hoisting operations. In particular, the vessel crane is a tub mounted crane for elevating and rotating a hoist load, in which the tub mounted crane comprises a substructure formed by a tub on which a superstructure is mounted. The superstructure comprises a crane house, a gantry on the crane house and a longitudinally extending boom which is at a proximal end pivotally connected to the crane house. The crane house defines a rear region of the vessel crane and a distal end of the boom defines a front region of the vessel crane. _ 3 _ The crane house is rotatably connected to the substructure to allow a rotation of the superstructure about a vertical axis. In other words, the crane house is rotatably connected to the substructure for allowing a slew motion of the superstructure relative to the substructure. The crane house comprises a boom connector for connecting the boom to the crane house. The boom connector defines a horizontal boom pivot axis. The crane house further comprises a gantry mount including a rear base mount and a front base mount for mounting a gantry. The crane house may include a cab where an operator manoeuvres the cranes controls. The superstructure comprises a boom for supporting a hoist load. The boom has a longitudinal axis which extends from a proximal end portion to a distal end portion. The distal end portion includes a head structure. The boom is pivotally connected to the crane house via the boom connector so that the boom is pivotal about the boom pivot axis. The proximal end portion of the boom is pivotally connected to the boom connector of the crane house. Herewith, the boom is pivotable about the boom pivot axis. The gantry, also called a luffing frame, is collapsible from a raised position to a lowered position for reducing a total crane height during transport. The gantry comprises a front framework and a rear framework. The gantry is mounted on the crane house. In the raised position, at a base, also called a lower end, the frontframework and the rearframework are connected to the crane house to respectively the front base mount and rear base mount of the gantry mount. At an upper end, the front framework and rear framework are connected to each other by a top pivot. The upper ends of the front and rear framework form an apex of the gantry. Seen in a side view, the gantry may have an upside down V-shape in which the V-legs are formed by the front framework and rear framework. Further, the superstructure comprises a boom hoist for raising and lowering the boom by pivoting the boom about a boom angle. The boom is pivotable in a vertical plane about the horizontal boom pivot axis to adjust a hoisting height of the crane. The boom hoist comprises at least one luffing winch for hauling in or paying out a luffing wire and a boom suspension which extends between the gantry apex and the head structure of the boom. The boom suspension includes a multiple fall arrangement of a rigged luffing wire. The multiple fall arrangement of luffing wire may extend about a whole length in between the gantry apex and the head structure of the boom, or about a length portion, wherein the multiple fall arrangement is connected to an extension. The extension may for example include a chain or a rod structure. _ 4 _ Further, the superstructure comprises a hoisting system for hoisting the hoist load. The hoisting system comprises at least one hoisting winch. In particular, the hoisting system comprises a hoisting winch assembly including a plurality of hoisting winches. An associated hoisting wire extends from the hoisting winch to the head structure of the boom. The hoisting winch may be provided at the proximal end portion of the boom, like in a Liebherr crane, or at the crane house. Preferably, the at least one hoisting winch is positioned inside the crane house. According to the invention an improvement is provided in that the superstructure further comprises a lowering mechanism for lowering the gantry. The lowering mechanism is arranged to move the gantry between the raised position and the lowered position. The lowering mechanism comprises a link framework and a lock system. The link framework is arranged for displacing the rear framework. At one end, the link framework is pivotally connected to the base of the rear framework of the gantry. At an opposite end, the link framework is pivotally connected to the crane house. In particular, the link framework has a first link pivot coupling the link framework to the base of the rear framework and the link framework has a second link pivot coupling the link framework to the crane house. The link framework is rotatable in a vertical plane with respect to the crane house to displace the base of the rear framework such that the gantry lowers or raises. During a displacement, the link framework provides a guidance to the base of the rear framework. Herewith, the link framework is configured to guide a displacement of the base of the rear framework when lowering the gantry to obtain a reduction of a total crane height. The lock system is arranged for locking the rear framework in position when the gantry is in the raised position. The lock system includes at least one lock member to lock or release the base of the rear framework to the rear base mount at the crane house. In a locked state, the rear framework is configured to carry out a hoisting operation. In the locked state, the base of the rear framework is locked in position relative to the crane house. In an unlocked state, the base of the rear framework is released and a displacement relative to the crane house is enabled to carry out a crane height reduction operation. In particular, in the unlocked state, the rear framework is displaceable in a direction away from the front framework to allow a lowering of the gantry. The base of the rear frameworkmay be lowered and guided by the link framework along a back side of the crane house to obtain a required total crane height reduction of for example about _ 5 _ 20m to allow a bridge passage ofa crane vessel. Beneficially, by reducing the total crane height in this manner, a crane vessel provided with the tub mounted crane and having a crane height of more than 70m, eg. about 85m crane height from a water line may be suitable to sail and pass a bridge like the Great Belt Bridge (which is in Danish called: Storebæltsbroen) which bridge has a clearance of 65 metres below the bridge. Considering the gantry, the lowering mechanism is advantageously configured to function in reducing a total crane height during travelling while not or minimally affecting a hoisting operation of the crane at a hoisting location. From a mechanical perspective, the gantry still has a same main configuration, no matter the availability of the lowering mechanism. The gantry is formed by the front and rear framework which may each be formed by a rigid body being at the base fixated to the crane house. In comparison with prior art solutions for reducing a total crane height, the rear framework may have a framework body which is formed by one rigid body. This one rigid body determines the robustness of the rear framework. The body of the rear framework is not sectioned by a structurally weakening rotaryjoint as disclosed in EP3.825.274 in the name of Liebherr. As the total crane height reduction is -seen from a structural perspective- independent from the hoisting operation, the incorporation of the lowering mechanism for lowering the gantry does not or hardly not negatively affect the robustness of the gantry during a hoisting operation. Regarding occurring forces which act on the gantry during the hoisting operation, the robustness of the gantry remains determined by the robustness of respectively the rear framework and the front framework which may each be integral parts and which are each at a base fixated to the crane house. Exerted forces acting on the gantry via the boom suspension are conducted via the base mounts of the front framework and the rear framework to the crane house. During a hoisting operation, the lowering mechanism, in particular the link framework has no load carrying function which beneficially allows a slim configuration of the link framework. In an embodiment of the vessel crane, the rear framework has a framework body which is formed by one rigid body. The framework body may be non-sectioned, Le. a single piece framework. The framework may be an integral part for conducting forces which beneficially provides a robust structure to carry a load in a hoisting operation. In an embodiment of the vessel crane, an assembly of the rear base mount and the base of the rear framework is formed by a pin-hole assembly. The arrangement of the pin-hole assembly _ 6 _ may be beneficial in installation of the gantry and alignment of the rear framework relative to the front framework. In an embodiment of the vessel crane, the link framework is connected to the base of the rear framework by a pin-hole configuration in which the hole is slotted. Beneficially, the slotted hole may prevent an over constrained structure. The slotted hole may overcome a possible misalignment between the link framework and the rear framework during a motion of the rear framework. In an embodiment of the vessel crane, the second link pivot of the link framework is connected to a side wall of the crane house. In particular, the second link pivot is connected to a bottom region of the crane house. Preferably, at an inner side of the side wall, the crane house has a reinforcement structure at the location of the second link pivot. In an embodiment of the vessel crane, the link framework includes a left and right link-leg. In particular, the link framework is H-shaped or may have a rectangular shape. Each link-leg is at one end pivotally connected to the base of the rear framework and at an opposite end pivotally connected to the crane house. In an embodiment of the vessel crane, the lowering mechanism comprises an end stop for supporting the link framework when being placed in the lowered position of the gantry. Preferably, the end stop is mounted to the substructure, in particular to the tub of a tub mounted crane. The end stop may be positioned on an outer wall of the substructure. Preferably, at the end stop, the outer wall is reinforced by a reinforcement structure. Alternatively, the end stop may be mounted to the crane house. The positioning of the end stop onto an outer side of the substructure is however beneficial in counteracting occurring forces without for example compromising a slew bearing of the crane house. In an embodiment of the vessel crane, the lock system comprises a lock member and a lock member actuator for actuating the lock member. In particular, the lock member is pin-shaped. The pin-shaped lock member is configured to fit into a hole at the base of the rear framework and to be received into a base mount hole, such that the lock member locks the base of the rear framework to the rear base mount. A pin-hole assembly is formed by the pin-shaped lock member and the holes of the rear base mount and the base of the rear framework. The lock member actuatormay be a hydraulic cylinder for moving the lock member actuator. Preferably, the lock member is linearly movable between a retracted position in which the lock system is in an unlocked state and an extended position in which the lock system is in a locked state. _ 7 _ In an embodiment of the vessel crane, the base ofthe rear framework may comprise a fork end portion having a first fork leg and second fork leg which each including a fork hole for receiving the lock member of the lock system. In an embodiment of the vessel crane, the lowering mechanism further comprises at least one tugger winch for tensioning the base mount of the rear framework. A pull force can be exerted by the at least one tugger winch to the rear framework to control its displacement during a gantry raising or lowering operation. The tensioning force may be exerted between the rear framework and the crane house in a direct manner or indirectly via the boom and / or the front framework. To obtain a predetermined span length of a tugger wire, the at least one tugger winch is preferably positioned near the front base mount of the front framework, e.g. within a radius of2m from the front base mount. Preferably, the at least one tugger winch is positioned at the boom connector. Theboom connector beneficially provides a robust support to the tugger winch. In an embodiment of the vessel crane, a tugger wire for tensioning the base of the rear framework may extend from the tugger winch to a tugger sheave at the boom via a tugger sheave at the front framework to the base of the rear framework. By guiding the tugger wire in such a manner, beneficially, a predetermined span length is obtained. In an embodiment of the vessel crane, at least one guide element, in particular a guide roller is positioned at a rear edge region on top of the crane house for guiding the tugger wire across the crane house when the base of the rear frame is situated behind the crane house. In an embodiment of the vessel crane, at least one guide element is positioned at a rear edge region on top of the crane house for conducting the tugger wire across the crane house. In particular, the at leastone guide element is a guide roller. The at leastone guide element allows the tugger wire to extend across the crane house and to extend downwardly behind the crane house. The at least one guide element conducts the tugger wire across the crane house when the base of the rear framework is situated behind the crane house. In an embodiment ofthe vessel crane, the lowering mechanism further comprises a control unit for lowering and raising the gantry by controlling respectively a payout and hauling in ofa boom hoist wire, also called a luffing wire. The boom hoist comprises at least one boom hoist winch, also called a luffing winch, and the control unit is operationally connected to the boom hoist for controlling a motion of the gantry. _ 8 _ In an embodiment of the vessel crane, the boom hoist for raising and lowering the boom comprises at least one boom hoist winch, also called a luffing winch, wherein the at least one luffing winch is situated inside a -seen from above- outer contour of the crane house. The at least one luffing winch may be positioned on top of the crane house on an crane house deck. In an embodiment of the vessel crane, the hoisting system for hoisting a hoist load comprises at least one hoisting winch being situated inside a -seen from above- outer contour of the crane house. The at leastone hoisting winch may be positioned on top ofthe crane house. Preferably, the crane house includes an inner compartment, also called a winch compartment, for housing the at least one hoisting winch inside the crane house. Preferably, the winch compartment is provided at a top region of the crane house. In an embodiment of the vessel crane, the at least one luffing winch of the boom hoist and the at least one hoisting winch of the hoisting system may be positioned in the winch compartment. The winch compartment may comprise a winch carry frame. The winch carry frame may include a platform for supporting at least one winch. Further, winch carry frame may include a plurality of connectors at an outer circumference to connect the winch carry frame to an inner side of the substructure, in particular to an inner side wall of a tub. Further, the invention relates to a crane vessel comprising at least one vessel crane, in particular at least one tub mounted crane, according to the invention. Further, the invention relates to a method for reducing a total crane height by lowering a gantry of a crane, wherein use is made of a vessel crane according to the invention. The method comprises a step of unlocking a rear base mount to release a base of a rear framework from a crane house and providing a displacement ofthe base ofthe rearframework in a direction away from the front framework while guiding the displacement by a link framework of a lowering mechanism. In an embodiment of the method, a tub mounted crane according to the invention is used. The tub mounted crane has a lowering mechanism for lowering a gantry. The lowering mechanism includes a lock system for locking a base of a rear framework of the gantry to the crane house during a hoisting operation and a link framework which is pivotally coupled to a base of the rear framework for guiding a movement of the base of the rear framework during a crane height reducing operation. In a step of the method, the base of the rear framework is displaced and guided by the link framework by paying out a luffing wire from at least one luffing winch. _ g _ In an embodiment of the method, during a displacement of the base of the rear framework, the base of the rear framework is guided by the link framework until the link framework abuts against an end stop. In an embodiment of the method, during its displacement, the base of the rear framework is tensioned by a tugger wire. A pulling force may be applied to maintain the base of the rear framework in position to allow the lock system to be unlocked. In the unlocked state of the lock system, the base of the rear framework can be displaced. To displace the base of the rear framework, the tension of the tugger wire is reduced. The tension reduction allows the base of the rear framework and the link framework to start moving. Thus, a method for reducing a total crane height and a vessel crane comprising a lowering mechanism for lowering a gantry to achieve a total crane height reduction is provided. The gantry is collapsible from a raised position RP to a lowered position LP. The gantry has a front framework and a rear framework. In the raised position RP, the rear framework is at a base connected to a rear base mount at the crane house. In the lowered position LP, the rear framework is disconnected and displaced. The lowering mechanism has a lock system for disconnecting the rear framework and a pivotal link framework for subsequently guiding the rear framework during its displacement. The invention will be explained in more detail with reference to the appended drawings. The drawingsshow a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which: Fig. 1 shows a side view of a tub mounted crane which has a tub which is mounted to a hull of a vessel, a superstructure having an upstanding gantry on top of a slewable crane house and an extending boom supported by a boom rest; Fig. 2 shows an enlarged view of the gantry of the tub mounted crane which is provided with a lowering mechanism for raising and lowering the gantry to obtain a total crane height reduction; Fig. 3 and 4 show a backwards tilting of a front framework of the gantry, wherein a base of a rear framework is lowered along a back side of the crane house and guided by a link _ 10 _ framework of the lowering mechanism until the link framework abuts against an end stop at the tub; Fig. 5 shows an enlarged view of the crane house which is provided with a boom connector defining a horizontal boom pivot axis, a front base mount for mounting the front framework and a rear base mount for mounting the rear framework to the crane house, wherein a tugger winch is provided for tensioning the base ofthe rear framework in case of an operation ofthe lowering mechanism; Fig. 6 shows an enlarged view of the base of the rear framework being positioned in a seat forming the rear base mount and wherein the base of the rear framework is connected to a link framework of the lowering mechanism; Fig. 7 shows a side view of Fig. 6 in which the base of the rear framework has a fork end provided with a fork end hole in alignment with upstanding plates with plate holes for receiving a pin to fasten the base of the rear framework by a pin-hole assembly; Fig. 8 is an enlarged view of Fig. 6 in which the link framework is not shown; Fig. 9 shows a head structure on a distal portion of the boom including a jib provided with an auxiliary load suspension device and a whip line. In Figs. 1-9, a vessel crane, in particular a tub mounted crane, is shown in an embodiment according to the invention and denoted overall by reference numeral 1. Identical reference signs are used in the drawings to indicate identical or functionally similar components. The tub mounted crane 1 is provided on board of a crane vessel 100. The tub mounted crane 1 has a pedestal, also called a tub 10, which is mounted to a hull 101 of the crane vessel. The crane vessel is configured for heavy lifting, e.g. more than 1500Mtons, in particular more than 5000Mtons. Based on a proven track record in delivering high capacity offshore cranes over the last decades, nowadays Huisman offers a range of Tub Mounted Cranes with lifting capacities up to 12,000mt. The tub mounted crane 1 is suitable to be used for transferring materials to and fro a quay, a marine vessel, a barge, a jacket, or another structure by elevating and rotating. The shown crane vessel 100 has a semi-submersible design which allows it to partially submerge in water. By pumping water in or out of ballast tanks, the crane vessel 100 can adjust its height in the water. This height adjustment capability serve to improve stability during heavy lifting operations. _ 11 _ In an other embodiment, the crane vessel 100 may be a jack-up vessel. Such a jack-up vessel comprises a hull 101 with openings in the hull, wherein the openings extend vertically through the hull 101 to receive a respective jack-up leg. For each leg, a leg driving device may be provided to allow to move the corresponding leg up and down relative to the hull in a vertical direction to allow the hull to be lifted out of a water body. The legs are retracted for sailing with the vessel. The top mounted crane 1 comprises a substructure formed by the tub 10 onto which a rotatable superstructure 11 is mounted. The superstructure is rotable about a vertical axis 01. The superstructure 11 comprises operating machinery to carry out hoisting operations. The superstructure 11 comprises a crane house 2, a gantry 4 on top of the crane house and a boom 3 being pivotable about a horizontal boom pivot axis 03 at a proximal boom end portion 301. In particular, in such a heavy lifting crane vessel 100, the boom pivot axis 03 is positioned at a height level of at least 20m, in particular about 30m above a deck level DL. The boom may have a boom length of at least 80m. As shown in Fig. 5, the boom 3 ofthe crane 1 has a latticed structure. The boom comprises an A-frame with two boom legs that are connected at one end to the crane house 2 so as to be pivotal about the boom pivot axis 03 of a boom connector 22. The latticed boom legs may adjoin another in a box structure. The crane house 2 is rotatably connected to the tub 10 to allow a rotation of the superstructure 11 about a -practically seen- vertical axis 01. The crane house 2 is rotatably connected to the tub 10 for allowing a slew motion of the revolving superstructure 11 relative to the substructure. The crane house comprises a boom connector 22 which defines the horizontal boom pivot axis 03. The crane house 2 may include a cab where an operator manoeuvres the cranes controls. The crane comprises a boom hoist 30, which may also be called a luffing assembly. The boom hoist is arranged to set an angular orientation of the boom 3 relative to the crane house 2. The boom hoist 30 is configured to raise and lower the boom by pivoting the boom 3 about a boom angle about the boom pivot axis 03 defined by the boom connector 22. The boom hoist 30 comprises at least one boom hoist winch, also called a luffing winch 31. The luffing winch 31 is arranged to wind and unwind a luffing wire 32. The at least one luffing winch 31 is positioned at the crane house. Preferably, the at least one luffing winch 31 is positioned at the rear region at an upper region of the crane house 2. The luffing wire 32 is reeved along the gantry and _ 12 _ extends in a multiple fall arrangements between a gantry apex and a distal end portion of the boom. The superstructure 11 comprises a hoisting system 7 for hoisting a hoist load by a load suspension device 8. Here, the load suspension device 8 includes a main load suspension device 81 provided with a main hoisting wire 810, a multi sheave main block and a hook. Further, the load suspension device 8 includes an auxiliary load suspension device 82 and a whip line 83, also called a fast line. The auxiliary load suspension device 82 and the whip line 83 are connected to a jib 38 provided at a head structure 302 of the boom 3. The hoisting system 7 comprises at least one hoisting winch 70. The at least one hoisting winch 70 is positioned at the crane house 2. Here, a hoisting winch assembly 71 is provided including a plurality of hoisting winches 70. The hoisting winch assembly 71 is situated at the upper region of the crane house 2. Hoisting wires 701 extend from the hoisting winch assembly 71 to the head structure 302 of the boom, which is also shown in Fig. 11. In Fig. 1, the gantry is shown in a raised position RP. As shown in Fig. 2-4, the gantry 4 is collapsible from the raised position RP to a lowered position LP for reducing a total crane height during travelling of the vessel. The gantry 4 comprises a front framework 40 and a rear framework 41 which are each mounted on top ofthe crane house 2. The front framework 40 is positioned at a front region on top ofthe crane house 2. In the raised position RP, at their bases, the front framework 40 and the rear framework 41 are each connected to the crane house 2 by respectively a front and rear base mount 400, 410. The bases are connected by a pin-hole assembly. The front base mount 400 of the front framework 40 includes a base pivot 040 which defines a front pivot axis 040. The base pivot allows the front framework 40 to tilt in a vertical plane. The base pivot 040 allows a pivotal movement of the front framework 40 relative to the crane house 2. Here, the base pivot 040 of the front framework is positioned above the boom pivot axis 03 of the boom connector 22. Here, the front base mount is integral with the boom connector 22. The base of the rearframework is connected to the crane house 2 by the rear base mount 410. The rear base mount 41 0 is positioned at a rear region on top ofthe crane house 2. In particular, the rear base mount 410 is provided at the crane house deck 23. _ 13 _ The rear base mount 401 of the rear framework is here formed a pin-hole assembly, see Fig. 6 and 7. The base of the rear framework has a through hole for receiving a pin. The pin-hole assembly has a seat 411, also called a base rest, at the crane house 2 for receiving the base of the rear framework. The seat has a seat hole 413 for receiving the pin to fixate the base of the rear framework to the seat. Here, the seat 411 has at least one upstanding plate 412. Each plate 412 has a plate hole 413 for receiving the pin. The seat 411 is here formed by a left and right upstanding plate 412 which are each fixated to the crane house. Each plate 412 has a seat portion for supporting the base of the rear frame work. The base of the rear framework has a plate shaped end provided with a through hole. Here, the base of the rear framework has a fork end 414 including a left and right fork leg which are each provided with a fork end hole 415. In the pin-hole assembly, the fork end holes 415 are in alignment with the left and right upstanding plate holes 413. At an upper end, the front framework and rear framework 40, 41 are connected to each other by a top pivot 42 at a gantry apex 43. Herewith, seen in a side view, the gantry has an upside down V-shape in which the V-legs are formed by the front framework 40 and rear framework 41. As shown in detail in Fig. 2, the superstructure ofthe tub mounted crane 1 further comprises a lowering mechanism 5 for lowering the gantry 4. The lowering mechanism 5 includes a link framework 50 and a lock system 51, see also Fig. 6, 7 and 8. The link framework 50 is arranged for displacing the rear framework 41 in downwards and upwards direction to respectively lower and raise the gantry. At one end, the link framework 50 is pivotally connected by a first link pivot 051 to the base of the rear framework of the gantry for displacing the base of the rearframework. At an opposite end, the link framework 50 is pivotally connected by a second link pivot 052 to the crane house 2. During a displacement, the link framework 50 provides a guidance to the base of the rear framework. By displacing the base of the rear framework, the gantry 4 can be lowered to reduce a total crane height. Seen from aside -in the side views of Fig. 2, 3 and 6- , the link framework 50 has an upside down L-shape. The link top 501 is provided with a first link pivot 051 at an end of a short leg of the L-shape. Here, as shown in Fig. 6, the first link pivot 051 is formed by a pin-hole coupling _ 14 _ in which the hole has an oblong shape. The link base 501 is provided with a second link pivot 052 at an end of a long leg of the L-shape. The second link pivot 052 connects the link base 50 to the crane house 2. The second link pivot 052 has a horizontal pivot axis which allows the link framework 50 to rotate in a vertical plane with respect to the crane house 2. The lock system 51 is arranged for locking the rear framework 41 in position when the gantry is in the raised position RP. The lock system 51 includes at least one lock member 510 to lock or release the base of the rear framework 41, see also Fig. 7 and 8. In a locked state, the gantry 4 is fixed to the crane house 2. The fixation by the lock system 51 provides a solid and rigid connection ofthe gantry 4 to the crane house 2 which is required for hoisting operations. In an unlocked state, the rear framework 41 of the gantry is displaceable which allows a lowering of the gantry 4. As shown in Fig. 3 and 4, the base of the rear framework is guided by the link framework 50 along a back side of the crane house. When lowering the base of the rear framework, the link framework 50 pivots about an angle of until about 180° along a back side of the crane house. In Fig. 3, an initial displacement of the base of the rearframework41 to an intermediate position 41 at a back of the crane house is shown. In Fig. 4, a further lowering of the base of the rear framework is shown , wherein the link framework 50 finally abuts against the substructure, which is here the tub of the tub mounted crane. Initially, in the raised position RP of the gantry, the link framework 50 is in an upright position. During lowering, the link framework 50 rotates in a direction away from the crane house 2 (backwards) as indicated by the references 42, 42 and 42". The link framework 50 rotates until the link top 501 abuts against an end stop 52. The end stop 52 is mounted at an outer side of a tub wall of the tub 10 for stopping the link framework 50. The tub wall may be provided with a reinforcement structure. After lowering the gantry 4, the link framework 50 has rotated about an angle of about 180°. As shown in Fig. 3 and 4 by the lowering ofthe gantry apex, a total crane height reduction is obtained. By using the link framework 50 for collapsing the gantry 4 of such a heavy lift crane 1 which might have a gantry height of for example about 90m from a water line WL, the gantry apex 43 can even be lowered about a distance of at least 20m. ln particular, the gantry apex 43 can be lowered until a total crane height of at most 65m above a waterline to allow a crane vessel 100 to pass large bridges like the Great Belt Bridge of Denmark. _ 15 _ Fig. 5 shows an enlarged view of the crane house 2 including a tugger winch 53 for tensioning the base of the rear framework by a tugger wire 530 during an operation of the lowering mechanism. Fig. 6 shows an enlarged view of the base portion of the rear framework 41 being positioned in the seat 411 on top of the crane house 2, wherein the tugger wire 530 is fastened to the base of the rear framework. As shown in Fig. 4, a guide element for guiding the tugger wire is positioned at the crane house deck 23. The guide element is a guide roller 531. The guide roller is positioned at a rear edge region on top of the crane house for conducting the tugger wire across the crane house when the base of the rear framework is situated behind the crane house. In a method for lowering a base of a rear framework, the tugger winch 53 is operated to exert a pull force when carrying out a displacement of the base of the rear framework 41 relative to the crane house 2. The tugger winch 53 is positioned at a front region of the crane house 2. The tugger winch 53 is positioned at the base of the front framework 40. A tugger wire 530 extends from the tugger winch 53 to the base of the rear framework 41. As shown in Fig. 6, an end of the tugger wire 530 is connected to the base of the rear framework 41. The tugger wire 530 extends along a tugger wire path which is determined by several tugger wire sheaves 531. In the illustrated embodiment, a tugger wire sheave 531 is connected to the boom 3 and another tugger wire sheave 531 is connected to the front framework 40, such that the tuggerwire path extends from the tuggerwinch 53 via the boom 3 and the frontframework40 to the base ofthe rearframework 41. It is remarked that another tugger wire path is also conceivable. Fig. 6, 7 and 8 further show the locksystem 51 which is arranged for locking the rear framework 41 in position when the gantry 4 is in the raised position RP. The lock system 51 includes at least one lock member 510 to look the base of the rear framework 41. The at least one lock member 51 fixates the base of the rear framework 41 to the crane house 2. The lock member 510 is formed by a pin which is receivable in the through hole at the base of the rear framework 41. The lock system 51 comprises a lock member actuator 511 for driving the lock member 510 into or out of the through hole for respectively locking or unlocking the base of the rearframework 41. Here, the lock member actuator 511 is a hydraulic actuator. The hydraulic actuator may be self-sustained and being provided with a pump unit and a battery for incidentally actuating the lock member 510. _ 16 _ Fig. 9 shows a head structure 302 ofthe boom 3 in further detail. The head structure includes a jib 38. The head structure 302 is arranged to carry a main load suspension device 81 which is connected by a main hoisting wire 810 and provided with a multi-sheave main block and hook, an auxiliary load suspension device 82 and a whip line, also called a fast line 83. Although the present invention has been described in detail, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as hereinafter claimed. It is intended that all such changes and modifications be encompassed within the scope of the present disclosure and claims. Further, it is remarked that any feature of the system according to the invention which is described in the embodiments and / or mentioned in the dependent claims is in itself considered patentable without any dependency to another presented feature. In particular, any measure presented in a dependent claim is also considered patentable without dependency of the independent claim. Reference signs list: TMC tub mounted crane 12 crane subassembly DL deck level 120 assembly table WL water line 121 table frame 122 crane house support RP raised position LP lowered position 2 crane house 21 circumferential wall H hoist position (of sheave) 211 lower end GT gantry tilt position (of sheave) 22 boom connector 23 crane house deck GS ground surface 212 upper end 25 middle section 1 tub mounted crane 26 lower section 01 vertical axis 27 upper section 100 crane vessel 28 inner space 101 hull 281 carrier mount 102 vessel deck 10 tub; pedestal; substructure 3 boom 11 superstructure 03 boom pivot axis _ 17 _ 301 proximal boom end portion 530 tugger wire 302 distal boom end portion; head structure 531 guide roller; tugger wire sheave 30 boom hoist; luffing assembly 31 boom hoist winch; luffing winch 6 boom suspension 32 luffing wire 60 multiple fall arrangement (6boom suspension) 61 gantry sheave block 610 gantry sheave frame 38 jib 611 complimentary connector member 39 boom rest 62 boom sheave block 620 boom sheave frame 4 gantry; luffing frame; A-frame 621 complimentary connector member 40 front framework 63 detachable sheave block 400 front base mount 630 sheave frame 040 base pivot 631 connector member 41 rear framework 632 second connector member 410 rear base mount 64 auxiliary block 411 seat 65 positioning member 412 upstanding plate 66 transfer winch 413 seat hole; plate hole 660 transfer wire 414 fork end 69: extension (not shown) 415 fork end hole 42 top pivot 7 hoisting system 43 gantry apex 70 hoisting winch 31, 70 lufng winch, hoisting winch 5 lowering mechanism 701 hoisting wire 50 link framework 71 winch carrier 501 link top 710 carrier body 051 first link pivot 711 platform 502 link base 712 winch seat 052 second link pivot 781 complementary carrier mount 51 lock system 8 load suspension device 510 lock member 81 main load suspension device 511 lock member actuator 810 main hoisting wire 811 multi sheave main block (and hook) 52 end stop 82 auxiliary load suspension device 53 tugger winch 83 whip line; fast line CONCLUSION | ES 1. Ship crane (1), in particular a tub crane (TMC; 1) for transferring a lifting load to or from a seagoing vessel, an inland vessel, a jacket or another structure, where the ship crane (1) includes a substructure (10) on which a superstructure (11) including operating machinery is mounted, where the superstructure (11) comprises: - a crane housing (2) that is rotatably connected to the substructure (10), in particular a tub (10), to allow a swiveling movement of the superstructure (11) relative to the substructure (10) to allow a vertical axis (01), where the crane house (2) a boom connector (22) includes a horizontal boom pivot axis (03) for connecting a boom to the crane housing (2) and a gantry attachment with a for located and rear base attachment point (400 and 410, respectively) for the attaching a gantry (4) to the crane housing (2) - a boom (3) for carrying a lifting load, where the boom has a |prong axis which extends from a proximal end section (301) to a distal end section with a head construction (302), where the boom (3) is hinged to the crane housing (2) via the boom connector (22) so that the boom (3) pivots around the boom pivot axis (03); - a gantry (4) attached to the crane housing (2), where the gantry (4) is foldable from a upright position (RP) to a lowered position (LP) to the total height of the crane to reduce while sailing, whereby the gantry (4) a forward frame (40) and a rear frame (41) includes each in the upright position (RP) of the gantry (4) with a base connected to the crane house (2) with the one in front respectively base attachment point (400) and the rear base attachment point (410) and where the gantry (4) has a gantry top (43) in which the front frame (40) and the rear frame frame (41) are connected to each other by means of a top hinge (42); - a boom hoisting device (30) for lifting and lowering the boom (3) by the boom (3) to to pivot a boom angle, whereby the boom hoisting device (30) has at least one luff winch (31) includes for hauling in or paying out a luff wire (32) and a boom suspension (6) which extends between the gantry top (43) and the head structure (302) of the boom, where the boom suspension (6) includes a multiple lifting device of a windward wire (32); - a hoisting system (7) for hoisting a load, where the hoisting system (7) at least a hoisting winch (70) includes a corresponding hoisting wire (701) extending from the hoisting winch (70) to the boom head structure (302) (3), with the characteristic that the upper structure (11) further includes a lowering mechanism (5) for lowering the gantry (4), which includes the lowering mechanism (5) - a coupling frame (50) for moving the rear frame (41), where the coupling frame (50) is hinged at one end to the base of the rear frame (41) by means of a first connecting hinge (051) and hinged at an opposite end connected to the crane housing (2) by a second connecting hinge (052), and - a locking system (51) to the base of the rear frame (41) to the to lock the rear base attachment point(410) when the gantry (4) is in the upright position (RP) and for unlocking the base of the back frame (41) located at the rear base attachment point (410) to a to enable displacement of the rear frame (41), whereby the locking system (51) includes at least one locking device (510) to the base to lock the rear frame (41) to or make it of the rear base attachment point (410) to allow a displacement of the rear located frame (41) to allow lowering of the gantry (4). 2. Ship crane (1) according to claim 1, where the rear frame (41) a has a frame body that is formed by a rigid body. 3. Ship crane (1) according to claim 1 or 2, where an assembly of the aft base attachment point (410) and the base of the rear frame (41) are formed by a mortise and tenon assembly. 4. Ship crane (1) according to one of the previous conclusions, where the coupling frame (50) is connected to the base of the rear frame (41) by means of a pin-hole arrangement in which the hole is a s|ob hole. 5. Ship crane (1) according to one of the preceding conclusions, where the second connecting hinge (052) of the coupling frame (50) with a side wall of the crane housing is connected, in particular in a lower area of ​​the crane housing (2). 6. Ship crane (1) according to one of the previous conclusions, where the coupling frame (50) has a left and a right connecting bone, each of which is hinged at one end connected to the base of the rear frame (41) and to an opposite one the ends are connected to the valve housing (2). 7. Ship crane (1) according to conclusion 6, where the coupling frame (50) has an H-shape. 8. Ship crane (1) according to one of the preceding conclusions, where the down|lower mechanism (5) includes an end stop for supporting the coupling frame (50) in the lowered position (LP) of the gantry (4). 9. Ship crane (1) according to claim 8, where the end stop is on the substructure (10) mounted, in particular on a reinforced outer wall of the substructure (10). 10. Ship crane (1) according to one of the preceding conclusions, where the locking system (51) includes a pin-shaped locking device (510) and a locking- organ actuator (511) for operating the locking mechanism (510). 11. Ship crane (1) according to one of the preceding conclusions, where the lowering mechanism (5) furthermore includes at least one tugger winch (53) for tensioning Moving the base of the rear frame (41) relative to the crane housing (2). 12. Ship crane (1) according to claim 11, where the at least one tugger winch (53) near the The base attachment point (400) of the frame (40) located in front is placed in the especially at the boom connector (22). 13. Ship crane (1) according to claim 12, where a tugger wire (530) extends from the at least one tugger winch (53) to a tugger sheave (531) on the boom (3) and where the tugger wire (530) returns via a tugger disc (531) on the frame (40) in front to the base of the rear frame (41). 14. Ship crane (1) according to one of the claims 11-13, where at least one ge|eidingse|lement, in particular a ge|eidingsro||er (531), in a rear section The edge area on top of the crane house (2) is positioned for guiding the tugger wire (530) along the crane housing (2) when the base of the rear frame (41) is behind the crane house (2) is located. 15. Ship crane (1) according to one of the preceding conclusions, where the lowering mechanism (5) furthermore includes a control unit for lowering the gantry (4) by issuing a windward thread of at least one windward (31). 16. Ship crane (1) according to one of the preceding conclusions, where the hoisting system (7) includes at least one hoisting winch (70) and / or where the boom hoisting device (30) includes at least one windward lier (31) encloses which within an outer contour, viewed from above, of the crane house is located. 17. Ship crane (1) according to claim 16, where the at least one hoisting winch (70) and / or the ten at least one windlass (31) has been placed on top of the crane house (2). 18. Ship crane (1) according to claim 16, where the at least one hoisting winch (70) and / or the ten at least one winding winch (31) is placed in a winch compartment inside the crane house (2). 19. Vessel with a crane (100) comprising at least one ship crane (1), in particular at least one tubular valve (TMC; 1) according to one of the preceding claims. 20. Method for reducing the total height of a crane using a gantry (4) to lower from a ship crane (1), using a ship crane (1) according to one of the conclusions 1-18, where the method includes a step with: - unlocking a rear base attachment point (410) to a base of a to detach the rear frame (41) from a crane housing (2); - moving a base of the rear frame (41) in a direction away from the front frame (40) while a displacement is guided by a coupling frame (50). 21. Method according to conclusion 20, whereby during the relocation thereof, the basis of the rear frame (41) is guided by the coupling frame (50) until the coupling frame (50) lies against an end stop. 22. Method in accordance with claim 20 or 21, whereby during the relocation thereof, the basis the rear frame (41) is tensioned by a tugger wire (530).

Images