Offshore crane vessel and crane

Abstract

An offshore crane vessel (1) has a hull (2) mounted crane (20) with a foldable boom (30) with boom section (40) and a jib section (50). A variable length struts stay mechanism is provided between the pivotal boom strut and the pivotal jib strut. The jib stay (45) comprises a variable length jib stay mechanism (60). The variable length stay mechanisms each have an associated drive. The foldable boom is configured to assume at least a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position, and a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on a boom rest (8).

Description

[0001] P37148PC00

[0002] OFFSHORE CRANE VESSEL AND CRANE

[0003] The present invention relates to an offshore crane vessel and to a crane configured to be mounted or mounted on an offshore crane vessel. The present invention also relates to a method for operating the crane.

[0004] In the field of handling of offshore wind turbine components "at the height of the nacelle", e.g. the nacelle itself and / or one or more components that are housed in the nacelle and / or mounted on the nacelle, e.g. a gearbox, an electric generator, the hub, and / or the rotor blades, the need exists for very tall cranes. Current designs of offshore wind turbines propose or already have the nacelle at a height of more than 100 meters above sea level, e.g. at 140 meters or more.

[0005] In a common approach, the offshore wind turbine is installed or serviced using a jack-up offshore crane vessel which is positioned close to the wind turbine location and then the jackup legs are extended and the hull of the vessel is lifted, at least in part but preferably entirely, above the sea, to provide a stabilized situation for the crane operation.

[0006] It is noted that the invention is primarily envisaged for the field of offshore wind, so for maintenance, and also for installation and / or decommission of wind turbines. However, the inventive crane and crane vessel may also be of use in other offshore applications, like oil & gas related operations, civil engineering operations, etc.

[0007] The lifting height requirement brings along the need for a very tall boom.

[0008] Some offshore cranes designed for use in the offshore wind industry have a telescopic boom in order to allow for a reduced boom length when the boom is parked on a boom rest of the vessel. For example, reference is made to WO2021123236.

[0009] Another approach is disclosed in WO2018088900. Herein an offshore crane vessel is disclosed having a foldable boom. The known offshore crane vessel comprises:

[0010] - a hull, e.g. a jack-up hull,

[0011] - a crane comprising: - a crane base which is secured to the hull,

[0012] - a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base,

[0013] - a foldable boom mounted to the revolving structure, the foldable boom comprising:

[0014] - a boom section comprising:

[0015] - a boom member, the lower end of which is pivotally mounted about a horizontal boom pivot axis to the structure,

[0016] - a boom strut, an inner end of which is pivotally mounted to an upper end of the boom, and

[0017] - a fixed length boom stay provided between the boom and the boom strut;

[0018] - a jib section comprising:

[0019] - a jib member, an inner end of which is pivotally mounted about a horizontal jib pivot axis to the upper end of the boom member, which jib member has a jib head at an outer end thereof,

[0020] - a jib strut, an inner end of which is pivotally mounted to the inner end of the jib member, and

[0021] - a fixed length jib stay provided between the jib member and the jib strut;

[0022] - a variable length struts stay mechanism provided between the boom strut and the jib strut,

[0023] - a luffing assembly comprising a luffing winch and a luffing cable extending between the structure and the boom member to determine a luffing angle of the boom member,

[0024] - a main hoist winch, a main hoist cable, and a main hoist block, wherein the main hoist cable extends from the hoist winch along the boom section and the jib section via a jib head sheave assembly on the jib head to the main hoist block,

[0025] - a boom rest.

[0026] The foldable boom of the crane in W02018088900 is configured to assume at least:

[0027] - a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,

[0028] - a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest.

[0029] The present invention aims to provide for enhanced folding of the boom, in particular in view of loads on the various parts of the boom during folding and / or in view of the efficiency of the folding routine and / or in view of reducing the total length of the crane when in the parked configuration. The present invention provides an offshore crane vessel according to claim 1.

[0030] Due to the fact that the jib stay mechanism is now also of a variable length due to the operation of the corresponding drive and that the jib strut is pivotal allowing for the pivoting thereof during folding of the crane boom, the geometry of the crane boom during folding, in particular the orientation of the struts, can be controlled and optimized, e.g. in view of the loads acting on the crane. This solution also allows for reorientation of the jib strut after the folding of the boom is completed, e.g. the jib strut being oriented in a substantially vertical upward orientation. This allows, for example, the reduce the length of the folded boom which protrudes beyond the contour of the vessel, e.g. allowing of better manoeuvring in a port

[0031] In the crane known from W02018088900 the boom strut and the jib strut each have a fixed perpendicular orientation relative to the corresponding boom member or jib member as the associated stay has a fixed length. It has been found that in the folding routine this causes the struts to become oriented relative to one another at a very large angle, with the variable length struts stay becoming relatively close to the pivot axis of the jib member. This creates undue loads. Also, as shown in figure 2a WO2018088900, this limits the folding by means of operation of the drive of the variable length struts stay, so that the jib member then still has a sizable gap with the boom member.

[0032] In an embodiment, the boom stay comprises a variable length boom stay mechanism having an associated drive, e.g. combined with a fixed length boom stay mechanism. In a more preferred embodiment, the boom stay is formed by a fixed length boom stay assembly, so has a fixed length and is devoid of a variable length boom stay mechanism. The latter embodiment is preferred in view of structural and operational complexity of the crane.

[0033] Due to the presence of the variable length struts stay mechanism and the jib stay mechanism according to the invention, possibly also the variable length boom stay mechanism, the jib strut can be favourably oriented throughout the folding routing (and also during the unfolding routine), thereby reducing loads, and in favourable embodiments, allowing for the jib member to achieve a so-called plumb line orientation along the raised boom member. In the plumb line orientation, the center of gravity of the jib member (and the main hoist block) is generally vertically below the pivot axis of the jib member.

[0034] Furthermore, in favourable embodiments, the jib strut may be oriented in a vertically upward orientation when the crane is in the folded and parked configuration, thereby limiting the total length of the crane in the parking position, e.g. thereby limiting the length of the crane the extends outside of the contour of the vessel.

[0035] In embodiments, the variable length struts stay mechanism is at one end thereof connected the boom strut and at the other end thereof to the jib strut.

[0036] In embodiments, the boom strut and the jib strut each have a length of at least 8 meters, for example 30 meters. Longer struts allow for more leverage, thereby decreasing the tension in the stay mechanisms and thereby decreasing the number of falls needed for the stay mechanisms.

[0037] The crane is configured to, with the boom in the folded, e.g. the fully folded, configuration, operate the luffing winch so as to lower the folded boom onto the boom rest in order to establish the folded and parked configuration.

[0038] In embodiments, the vessel is a jack-up vessel having a hull and jack-up legs as well as jackup mechanism configured to lift the hull out of the water. For example, the crane is an around- the-leg crane.

[0039] In embodiments, the revolving structure comprises a crane housing, e.g. configured to extend about the jack-up leg of the vessel, which is rotatable to allow for slew motion of the revolving structure relative to the crane base around the vertical slew axis, and further comprise a luffing frame structure mounted on top of the crane housing. Herein, the luffing assembly comprises left-hand and right-hand luffing cable sheave sets at a top of the luffing frame structure, and left-hand and right-hand luffing cable sheave sets on the upper end of the boom member, wherein luffing cables driven by luffing winches extend between the sheave sets, e.g. on opposite sides of the jack-up leg.

[0040] For example, the crane includes a luffing assembly as disclosed in WO2023135167.

[0041] In an embodiment, with the boom stay being formed by a fixed length boom stay assembly, the crane is configured to, e.g. a controller associated with the drives of the variable length struts stay mechanism, and the variable length jib stay mechanism is programmed to, perform a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive of the variable length struts stay mechanism so as to lengthen the struts stay mechanism, b) operating the drive of the variable length jib stay mechanism so as to lengthen the jib stay mechanism, wherein operations a), and b) are performed so as to achieve a plumb line orientation of the jib member.

[0042] In an embodiment, with the boom stay comprising a variable length boom stay mechanism having an associated drive, the crane is configured to, perform a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive of the variable length struts stay mechanism so as to lengthen the struts stay mechanism, b) operating the drive of the variable length boom stay mechanism so as to lengthen the boom stay mechanism, c) operating the drive of the variable length jib stay mechanism so as to lengthen the jib stay mechanism, wherein a), b) and c) are performed so as to achieve a plumb line orientation of the jib member.

[0043] The operations a), b), or a), b) and c), may be performed consecutively, e.g. as elucidated with reference to the appended drawings, but it is also possible to perform multiple or all these operations in timed overlap, or even all simultaneously. Herein, preferably, the operations are done so as to vary the orientation of the jib strut relative to boom strut and the jib member and thereby optimize the loads on the parts of the crane boom.

[0044] For example, the crane has a boom stop assembly, wherein a boom stop member on the revolving structure, e.g. on the luffing frame structure thereof, is configured to contact a boom stop member on the boom member. In embodiments, the raised position of the boom member during a folding routine of the boom is defined by the boom stop members contacting one another.

[0045] In an embodiment, with the boom stay being formed by a fixed length boom stay assembly, the boom strut includes an angle of between 75° and 85°, e.g. about 80°, with the boom member. In an embodiment, with the boom stay comprising a variable length boom stay mechanism having an associated drive, in the folded configuration the boom strut includes an angle of between 60° - 90° with the boom member.

[0046] In an embodiment, the jib strut is configured - when the crane boom is in the folded and parked position thereof - to be moved into an upward, e.g. a substantially vertically upward, oriented position. In practical embodiments, the upward oriented jib strut includes an angle of between 230° - 270° with the jib member. In this position the total length of the crane boom is reduced. This, e.g., allows for a reduced length of the crane boom which extends outside of the contour of the vessel.

[0047] For example, in the folded and parked configuration the jib strut and the boom strut include an angle of between 25° - 75°, e.g. between 25° - 45°.

[0048] In an embodiment, the crane is configured to perform a folding routine, wherein with the boom in raised position, first the boom is brought in an inclined position, so lowered relative to its raised position, then the variable length struts stay mechanism and variable length jib stay mechanism are used to bring the jib member in the plumb line orientation. As in the prior art WO2018088900, or as discussed herein, an auxiliary system(s) with an auxiliary line and winch may then be used to pull the jib member towards the still inclined boom member and fixated thereto. Due to the provision of two variable length stay mechanisms, contrary to WO2018088900, the jib strut of the now folded and fixated boom can be reoriented, e.g. so that the jib stay becomes parallel to the jib member before the folded jib is made to rest on the boom rest, e.g. to be reoriented in upward position once the folded boom rests on the boom rest.

[0049] As the raised position of the boom member, in practice, may be near-vertical, yet not vertical (as otherwise the boom might drop backward), there will be a relatively small gap between the boom member and the jib member in the plumb line orientation thereof. This gap can be vastly smaller than the folded configuration of figure 2a in WO2018088900. For example, the jib member then includes an angle of less than 15° with the raised boom member.

[0050] In embodiments, the crane is provided with a pull-in and fixation mechanism adapted to pull the jib member from its plump line orientation further towards the boom member in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration. In an embodiment, this pull-in and fixation mechanism comprises a pull-in winch and pull-in line, e.g. as described herein in more detail. However, in other embodiments, this pull-in and fixation mechanism may be devoid of a pull- in winch and pull-in line as the practical handling thereof is complex and time-consuming.

[0051] In embodiments, it is preferred that the jib head is embodied as a gooseneck jib head which is configured such that in a folded configuration of the boom, e.g. when the boom member is in its raised position and the jib member is in a plumb line orientation or when the boom is fully folded, the jib head reaches the boom member, preferably extends into the boom member. Herein a fixation mechanism, e.g. a pull-in and fixation mechanism, is mounted on one or both of the boom member and the gooseneck jib head.

[0052] For example, the pull-in mechanism comprises one or more actuator driven movable connector members which are arranged on the boom member and are actuable to engage on the goose neck jib head and then pull-in the jib member. For example, the actuator driven movable connector members comprise a gripper movable by a hydraulic cylinder assembly to move between an extended gripping position wherein the gooseneck is gripper and a retracted fixation position so that the jib member is pulled in and fixated. In another embodiment, the actuator driven movable connector members comprise a toothed rack on the gooseneck jib head and a motor driven pinion on the boom member, so that in the plumb line orientation the pinion meshes with the rack and the operation of the pinion drive motor causes the pull-in of the jib member.

[0053] For example, the fixation mechanism comprises one or more actuator operated fixation pins.

[0054] In embodiments, the jib head is provided with a main hoist block receiving assembly, which is configured to receive the main hoisting block during folding of the boom. For example, the receiving assembly comprises a locking arrangement configured to lock in place the received main hoisting block.

[0055] In an embodiment, the jib stay mechanism comprises the variable length jib stay mechanism as well as a fixed length jib stay assembly, wherein the variable length jib stay mechanism comprises a corresponding stay mechanism winch and a winch driven cable reeved between a first and second jib sheave set, wherein the first jib sheave set is connected to the jib strut and wherein the second jib sheave set is connected to the fixed length jib stay assembly.

[0056] In an embodiment, the vessel comprises a retention member which is configured to retain the second jib sheave set, e.g. when crane is in the folded and parked position, e.g. wherein the retention member extends from the boom rest or from the jib section or the boom member, e.g. wherein the retaining member ensures that the second jib sheave set cannot move when retained. For example, when the crane is in the folded and parked position, and wherein the jib strut is oriented substantially vertically upward, the retention member retains the second jib sheave set in a position such that the fixed length jib stay assembly is parallel to the jib section.

[0057] In an embodiment, the fixed length jib stay assembly and / or the fixed length boom stay assembly comprise multiple linked stay members, e.g. stay rods. For example, wherein the multiple stay members are pivotably connected to each other, e.g. such that the fixed length boom stay may be folded up, e.g. for transportation.

[0058] In an embodiment, the crane comprises a first auxiliary winch drive line system comprising a first auxiliary line and associated winch, the first auxiliary line departing from the revolving structure or from the boom member, and wherein the crane comprises a second auxiliary winch drive line system comprising a second auxiliary line and associated winch, the second auxiliary line departing from the outer end of the jib member. For example, the first auxiliary winch drive line system is a tugger winch system comprising a tugger line, and the second auxiliary winch drive line system is a sling hoist winch system comprising a sling hoist line. The provision of a tugger winch system and / or a sling hoist winch system is known in the art.

[0059] In the context of the folding of the crane boom, in embodiments, it is envisaged that these first and second auxiliary lines are connected to one another to form part of the pull-in and fixation mechanism. For example, these lines are first lowered to the level of a deck of the vessel, allowing for their connection. In embodiments, the method comprises:

[0060] - operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the connected auxiliary lines taught, e.g. prior to folding of the jib, and keeping the connected auxiliary lines taught during folding the jib into plump line orientation,

[0061] - operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the jib member from its plump line orientation further towards the boom member in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

[0062] In an embodiment, the one or both of the winches of the first and second auxiliary winch drive line systems are operated to provide a controlled, e.g. a constant tension in the connected auxiliary lines during the (un)folding of the crane. This provides a controlled (un)folding of the crane. In an embodiment, the boom strut is fixedly mounted to the upper end of the boom member and the boom stay is a fixed length boom stay.

[0063] In an embodiment, the boom strut is a pivotable boom strut, an inner end of which is pivotally mounted to an upper end of the boom member, wherein the boom stay comprises a variable boom stay mechanism, and wherein the variable length boom stay mechanism has an associated drive. The pivotal boom strut and variable boom stay mechanism allow for more control and optimization of the orientation of the struts, e.g. in view of the loads acting on the crane.

[0064] In an embodiment, in the folded configuration the pivotal boom strut includes an obtuse angle of between 110° - 140° with the boom member.

[0065] In an embodiment, in the folded configuration the jib strut includes an obtuse angle of between 120° - 160° with the jib member.

[0066] In an embodiment, in the folded configuration the jib strut and the boom strut include an angle of between 70° - 110°.

[0067] In an embodiment, each of the variable length struts stay mechanism, the variable length jib stay mechanism, and optionally the variable length boom stay mechanism, comprises a stay mechanism winch and a winch driven cable reeved in a multi-fall arrangement between associated sheave sets, e.g. wherein said stay mechanism winches are mounted on the revolving structure.

[0068] In an embodiment, the jib stay comprises the variable length stay mechanism as well as a fixed length stay assembly e.g. the variable length jib stay mechanism adjoining the jib strut, e.g. wherein the variable length strut stay mechanism is at one end thereof connected the boom strut and at the other end thereof to the jib strut. Optionally, the boom stay comprises the variable length stay mechanism as well as a fixed length stay assembly, e.g. the variably length stay mechanism adjoining the boom strut.

[0069] In embodiments, the boom stay and the jib stay each comprise the respective variable length stay mechanism as well as a fixed length stay assembly, e.g. the variable length boom stay mechanism and the variable length jib stay mechanism adjoining the respective boom strut and jib strut. The boom member and the jib member each have a front facing side and a back facing side, i.e. the front facing side being the side of the boom member and the jib member that face the main hoist block when the foldable boom is in the raised boom configuration.

[0070] In an embodiment, the boom strut is at its inner end mounted to the upper end of the boom member at the back facing side thereof. The pivotal jib strut is at its inner end mounted to the inner end of the jib member at the front facing side thereof.

[0071] In an embodiment, the boom strut comprises a first and second boom strut member which are each connected to the upper end of the boom member and extend from the boom member such that - when viewed in a vertical plane - the two boom strut members coincide. The first and second strut members are interconnected by multiple cross members. Similarly, the jib strut comprises a first and second jib strut member which are each connected to the lower end of the jib member and extend from the jib member such that - when viewed in a vertical plane - the two jib strut members coincide.

[0072] In an embodiment, the boom stay comprises a first and second boom stay member which extend between the boom member and respectively the first and second boom strut member. The jib stay comprises a first and second jib stay member each comprising a respective variable length jib stay mechanism. The first and second jib stay extend between the upper end of the jib member, in proximity of the jib head, and respectively the first and second jib strut member.

[0073] In an embodiment, the variable length struts stay mechanism comprises a first and second winch driven cable reeved in a multi-fall arrangement between associated sheave sets. The first and second boom strut members and the first and second jib strut members each being provided with a sheave sets, such that the first winch driven cable extends between the first boom strut member and the first jib strut member, and the second winch driven cable extends between the second boom strut member and the second jib strut member.

[0074] In an embodiment, the first and second jib strut member diverge with respect to each other from the jib member, i.e. the laterally distance between the jib strut members along the length of the jib strut members. Due to the two jib strut members diverging from one another, the attachment point of the first and second jib stay members is located laterally further away from the jib member, thereby increasing the angle between the first and second jib stay and the jib member when seen in a front facing view, e.g. looking directly at the front facing side of the boom member and the jib member. This increased lateral spacing widens the angle between the jib stays and the jib member, improving lateral stability.

[0075] In an embodiment, the first and second boom stay members are laterally spaced from one another, and the luffing cables are located laterally between the boom stay members. In an embodiment, the luffing assembly comprises a first and second luffing cable which extend between two laterally spaced apart locations on the revolving structure and two laterally spaced apart locations on the outer end of the boom member. The first and second boom stay member being arranged such that the first and second luffing cable are located laterally between the two boom stay members.

[0076] In an embodiment, the boom strut and the jib strut are each formed by a single latticed box structure. The boom stay comprises a connection member which is connected to the boom strut. The connection member provides laterally spaced apart attachment points for the first and second boom stay members such that the first and second boom stay members are laterally spaced from one another, and the luffing cables can be located laterally between the boom stay members.

[0077] In an embodiment, the boom member has a length between 70 and 90 meters and the jib member has a length between 50 and 75 meters, e.g. the boom member having a length of 85 meters and the jib member of 68 meters.

[0078] In an embodiment, the crane has safe working load (SWL) of more than 1000 tonnes in the fully raised position of the boom, e.g. at a radius of between 30 and 40 meters from the slew axis, e.g. a SWL of 1300 tonnes. This allows for handling of a nacelle of an offshore wind turbine, e.g. a nacelle provided with one or more of the rotor blades (e.g. bunny ears configuration) when desired.

[0079] In an embodiment, each of the boom member and the jib member are latticed members.

[0080] In an embodiment, the boom member has inner leg portions, each having a pivot member at an inner end mounted to the revolving structure, the inner leg portions at the outer end thereof adjoining a latticed box structured part of the boom member having longitudinal chords at corners thereof with bracing members between the longitudinal chords. In an embodiment, the inner legs portions are laterally spaced apart from each other such that that they define a space between them. In a folded configuration, the jib head is configured to be, at least partially, received in the spaced defined by the inner leg portions.

[0081] In an embodiment, both the boom member and the jib member are over their length of a tapered design when seen from the front. Herein the lateral sides of the boom define a greater width near the lower end than the width at the upper end of the boom member. The lateral sides of the jib member define a greater with near the inner end than the width at the outer end of the jib member. Preferably the front side and rear side of the boom member are generally parallel to one another. Also, preferably, the front side and the rear side of the jib member are parallel to one another. Due to the tapering shape of both the boom member and the jib member and enhanced stability of these members is obtained, e.g. in view of sidelead loads on the crane, and / or in view of loads during the process of folding and unfolding.

[0082] In an embodiment, the jib head sheave assembly is configured such that - when the foldable boom is in a folded position - the main hoisting cable extends vertically downward between the jib head sheave assembly and the main hoist block. Preferably, the jib head sheave assembly is configured such that the main hoisting cable extends vertically downward between the jib head sheave assembly and the main hoist block during the entire transition between the raised boom configuration and the folded and parked configuration.

[0083] In an embodiment, the jib head sheave assembly comprises one or more catch members, e.g. catching sheaves, which are configured to support the main hoist cable during movement of the jib between the raised and folded positions, wherein the catcher element constrains the main hoist cable throughout the transition between the raised and folded positions, thereby maintaining engagement of the main hoist cable with the main hoist block. Each catcher forms a cable-engaging surface or cradle that intercepts and supports the main hoist cable as the jib rotates toward the folded position, preferably the main hoist cable is already engaged with the catch member in the raised boom configuration. As the geometry changes, the cable is guided by the catcher so that it remains captured within the sheave region and is prevented from migrating off the sheaves or deviating laterally. This ensures that the cable does not disengage from the main hoist block.

[0084] In an embodiment, the boom member and / or the jib member have a tapering configuration, i.e. having a broader lower end and a narrower upper end. Preferably, the boom member and the jib member have a continuous tapering configuration, e.g. the front and back chords of the jib member extend substantially in line with the respective front and back chords of the boom member. Preferably, the boom member and the jib member together form effectively a continuous A-frame structure when in the raised boom configuration.

[0085] In an embodiment, the boom member and the jib member each have two main front chords and two main back chords, wherein the front and back chords have a tapering configuration, i.e. the front and back main chords move towards each other along the height of the boom members.

[0086] In an embodiment, the crane is provided with a tagline system for controlling the load which is handled by the crane. For example, the tagline system comprises one or more tagline trolleys which are movable along the boom member or along the jib member, a tagline winch and a winch driven tagline, which tagline - in use of the crane - extends from the tagline trolley to the load and / or to the main hoist block. Preferably, the tagline trolleys are configured to engage and move along the front main chords of the boom member and / or jib member. For example, the boom member or the jib member, or both, are latticed members embodied as described in WO2024083833A1 , so that chords of the member form rails for a tagline trolley.

[0087] For example, the crane, e.g. the boom member or the jib member, is provided with a tagline system as disclosed in W02023006796.

[0088] An advantage of the foldable boom of great length as discussed herein, e.g. compared to a telescopic boom, lies in its stiffness. This stiffness translates into the effectiveness and accuracy that can be achieved by the tagline system.

[0089] For example, one or more tagline trolleys are mounted on the jib member and movable along the jib member, e.g. by a winch drive tagline trolley displacement wire.

[0090] The vessel may further have a deck, e.g. configured for transportation of one or more rotor blades and / or one or more nacelles, and / or one or more other components of an offshore wind turbine.

[0091] The present invention envisages the use of the crane of the vessel for handling a wind turbine component, e.g. a nacelle, a rotor blade, etc.

[0092] The present invention also relates to a method of operation of an offshore crane vessel as described herein, wherein the boom stay is formed by a fixed length boom stay assembly, wherein the method comprises performing a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive of the variable length struts stay mechanism so as to lengthen the struts stay mechanism, b) operating the drive of the variable length jib stay mechanism so as to lengthen the jib stay mechanism, wherein a), and b) are performed so as to achieve a plumb line orientation of the jib member.

[0093] The present invention also relates to a method of operation of an offshore crane vessel as described herein, wherein the boom stay comprises a variable length boom stay mechanism having an associated drive, and wherein method comprises performing a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive of the variable length struts stay mechanism so as to lengthen the struts stay mechanism, b) operating the drive of the variable length boom stay mechanism so as to lengthen the boom stay mechanism, c) operating the drive of the variable length jib stay mechanism so as to lengthen the jib stay mechanism, wherein a), b) and c) are performed so as to achieve a plumb line orientation of the jib member.

[0094] In an embodiment, the vessel is provided with an automated controller linked to the drives of the variable length stay mechanisms, e.g. a programmed controller, to perform the actions a), b), or a), b), and c), in an automated manner, e.g. on the basis of pre-programming the controller. In an embodiment, possibly, the parking of the folded boom is also performed by an automated controller.

[0095] In an embodiment, the crane is provided with a pull-in and fixation mechanism adapted and operated to pull the jib member from its plump line orientation further towards the boom member in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration. In an embodiment, the method further comprises, with the boom in said folded, e.g. said fully folded, configuration, operating the luffing winch so as to lower the folded boom onto the boom rest in order to establish the folded and parked configuration.

[0096] In an embodiment, the jib head is a gooseneck jib head which is configured such that in a folded configuration of the boom, wherein the boom member is in its raised position and the jib member is in the plumb line orientation, the jib head reaches the boom member, preferably extends into the boom member. In an embodiment, a fixation mechanism, e.g. a pull-in and fixation mechanism, is mounted on one or both of the boom member and the gooseneck jib head and is used to fixate the jib member prior to operating the luffing winch for bringing the folded boom to rest on the boom rest.

[0097] In an embodiment, the jib head is provided with a main hoist block receiving assembly, which receives the main hoisting block during folding of the boom.

[0098] In an embodiment, the receiving assembly comprises a locking arrangement configured and operated to lock in place the received main hoisting block.

[0099] In embodiment, with the jib member being fixated relative to the boom member in the fully folded configuration, the drives of the variable length jib stay mechanism and variable length strut stay mechanism are operated to reorient the jib strut, e.g. in view of the optimal orientation for the parking of the folded boom on the boom rest.

[0100] In an embodiment, the jib strut is reoriented to a substantially vertically upward oriented position, e.g. wherein the jib strut makes an angle with respect to the jib section of 220° - 270°.

[0101] In an embodiment, the jib stay mechanism comprises the variable length jib stay mechanism as well as a fixed length jib stay assembly, wherein the variable length jib stay mechanism comprises a corresponding stay mechanism winch and a winch driven cable reeved between a first and second jib sheave set, wherein the first jib sheave set is connected to the jib strut and wherein the second jib sheave set is connected to the fixed length jib stay assembly, wherein the vessel comprises a retention member which is configured to retain the second jib sheave set, wherein the second jib sheave set is retained by the retention member in a position such that the fixed length jib stay assembly is parallel to the jib member. In an embodiment, wherein the jib strut is reoriented to a substantially horizontal oriented position, wherein the jib stay is parallel to the jib member.

[0102] A second aspect of the invention relates to an offshore crane vessel comprises:

[0103] - a hull, e.g. a jack-up hull,

[0104] - a crane comprising:

[0105] - a crane base which is secured to the hull,

[0106] - a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base,

[0107] - a foldable boom mounted to the revolving structure, the foldable boom comprising:

[0108] - a boom section comprising:

[0109] - a boom member, the lower end of which is pivotally mounted about a horizontal boom pivot axis to the structure,

[0110] - a boom strut, an inner end of which mounted to an upper end of the boom, and

[0111] - a boom stay provided between the boom and the boom strut;

[0112] - a jib section comprising:

[0113] - a jib member, an inner end of which is pivotally mounted about a horizontal jib pivot axis to the upper end of the boom member, which jib member has a jib head at an outer end thereof,

[0114] - a jib strut, an inner end of which is pivotally mounted to the inner end of the jib member, and

[0115] - a jib stay provided between the jib member and the jib strut;

[0116] - a variable length struts stay mechanism provided between the boom strut and the jib strut,

[0117] - a luffing assembly comprising a luffing winch and a luffing cable extending between the structure and the boom member to determine a luffing angle of the boom member,

[0118] - a main hoist winch, a main hoist cable, and a main hoist block, wherein the main hoist cable extends from the hoist winch along the boom section and the jib section via a jib head sheave assembly on the jib head to the main hoist block,

[0119] - a boom rest, wherein the foldable boom is configured to assume at least:

[0120] - a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position, - a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, and wherein the jib head is a gooseneck jib head which is configured such that in a folded configuration of the boom, wherein the boom member is in its raised position and the jib member is in a plumb line orientation, the jib head reaches the boom member, preferably extends into the boom member.

[0121] In an embodiment, a fixation mechanism, e.g. a pull-in and fixation mechanism, is mounted on one or both of the boom member and the gooseneck jib head.

[0122] For example, the fixation mechanism comprises one or more actuator operated fixation pins.

[0123] For example, the crane comprises a first auxiliary winch drive line system comprising a first auxiliary line and an associated winch, the first auxiliary line departing from the revolving structure or from the boom member, and the crane comprises a second auxiliary winch drive line system comprising a second auxiliary line and an associated winch, the second auxiliary line departing from the outer end of the jib member, wherein the first and second auxiliary lines are connectable to one another to form part of a pull-in and fixation mechanism which is adapted to pull the jib member from a plump line orientation thereof further towards the boom member in the raised position thereof into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

[0124] For example, the first auxiliary winch drive line system is a tugger winch system comprising a tugger line and the second auxiliary winch drive line system is a sling hoist winch system comprising a sling hoist line.

[0125] The second aspect also relates to a method of operating the crane of the offshore vessel, wherein when the boom member is in its raised position and the jib member is in a plumb line orientation, the jib head reaches the boom member, preferably extends into the boom member.

[0126] A third aspect of the invention relates to an offshore crane vessel comprises:

[0127] - a hull, e.g. a jack-up hull,

[0128] - a crane comprising: - a crane base which is secured to the hull,

[0129] - a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base,

[0130] - a foldable boom mounted to the revolving structure, the foldable boom comprising:

[0131] - a boom section comprising:

[0132] - a boom member, the lower end of which is pivotally mounted about a horizontal boom pivot axis to the structure,

[0133] - a boom strut, an inner end of which is mounted to an upper end of the boom, and

[0134] - a boom stay provided between the boom and the boom strut;

[0135] - a jib section comprising:

[0136] - a jib member, an inner end of which is pivotally mounted about a horizontal jib pivot axis to the upper end of the boom member, which jib member has a jib head at an outer end thereof,

[0137] - a jib strut, an inner end of which is pivotally mounted to the inner end of the jib member, and

[0138] - a jib stay provided between the jib member and the jib strut;

[0139] - a variable length struts stay mechanism provided between the boom strut and the jib strut,

[0140] - a luffing assembly comprising a luffing winch and a luffing cable extending between the structure and the boom member to determine a luffing angle of the boom member,

[0141] - a main hoist winch, a main hoist cable, and a main hoist block, wherein the main hoist cable extends from the hoist winch along the boom section and the jib section via a jib head sheave assembly on the jib head to the main hoist block, a boom rest, wherein the foldable boom is configured to assume at least:

[0142] - a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,

[0143] - a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, and wherein the jib head is provided with a main hoist block receiving assembly, which is configured to receive the main hoisting block during folding of the boom, e.g. wherein the receiving assembly comprises a locking arrangement configured to lock in place the received main hoisting block.

[0144] A fourth aspect of the invention relates to an offshore crane vessel comprises: - a hull, e.g. a jack-up hull,

[0145] - a crane comprising:

[0146] - a crane base which is secured to the hull,

[0147] - a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base,

[0148] - a foldable boom mounted to the revolving structure, the foldable boom comprising:

[0149] - a boom section comprising:

[0150] - a boom member, the lower end of which is pivotally mounted about a horizontal boom pivot axis to the structure,

[0151] - a boom strut, an inner end of which is mounted to an upper end of the boom, and

[0152] - a boom stay provided between the boom and the boom strut;

[0153] - a jib section comprising:

[0154] - a jib member, an inner end of which is pivotally mounted about a horizontal jib pivot axis to the upper end of the boom member, which jib member has a jib head at an outer end thereof,

[0155] - a jib strut, an inner end of which is pivotally mounted to the inner end of the jib member, and

[0156] - a jib stay provided between the jib member and the jib strut;

[0157] - a variable length struts stay mechanism provided between the boom strut and the jib strut,

[0158] - a luffing assembly comprising a luffing winch and a luffing cable extending between the structure and the boom member to determine a luffing angle of the boom member,

[0159] - a main hoist winch, a main hoist cable, and a main hoist block, wherein the main hoist cable extends from the hoist winch along the boom section and the jib section via a jib head sheave assembly on the jib head to the main hoist block,

[0160] - a boom rest, wherein the foldable boom is configured to assume at least:

[0161] - a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,

[0162] - a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, and wherein the crane comprises a first auxiliary winch drive line system comprising a first auxiliary line and associated winch, the first auxiliary line departing from the revolving structure or from the boom member, and wherein the crane comprises a second auxiliary winch drive line system comprising a second auxiliary line and associated winch, the second auxiliary line departing from the outer end of the jib member, wherein, preferably, the first and second auxiliary lines are connectable to one another to form part of a pull-in and fixation mechanism.

[0163] The fourth aspect of the invention also relates to a method for operation of the offshore crane vessel, wherein prior to folding of the boom:

[0164] - the winches of the first and second auxiliary winch drive line systems are operated so that the first and second auxiliary lines are with an end thereof at the level of a deck of the vessel,

[0165] - the ends of the auxiliary lines are connected, and wherein the method further comprises:

[0166] - operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the connected auxiliary lines taught, e.g. prior to folding of the jib, and keeping the connected auxiliary lines taught during folding the jib into plump line orientation,

[0167] - operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the jib member from its plump line orientation further towards the boom member in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

[0168] In an embodiment, the one or both of the winches of the first and second auxiliary winch drive line systems are operated to provide a controlled, e.g. a constant, tension in the connected auxiliary lines during the (un)folding of the crane. This provides a controlled (un)folding of the crane.

[0169] A fifth aspect of the invention relates to an offshore crane vessel comprises:

[0170] - a hull, e.g. a jack-up hull,

[0171] - a crane comprising:

[0172] - a crane base which is secured to the hull,

[0173] - a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base,

[0174] - a foldable boom mounted to the revolving structure, the foldable boom comprising: - a boom section comprising:

[0175] - a boom member, the lower end of which is pivotally mounted about a horizontal boom pivot axis to the structure,

[0176] - a boom strut, an inner end of which is mounted to an upper end of the boom, and

[0177] - a boom stay provided between the boom and the boom strut;

[0178] - a jib section comprising:

[0179] - a jib member, an inner end of which is pivotally mounted about a horizontal jib pivot axis to the upper end of the boom member, which jib member has a jib head at an outer end thereof,

[0180] - a jib strut, an inner end of which is pivotally mounted to the inner end of the jib member, and

[0181] - a jib stay provided between the jib member and the jib strut;

[0182] - a variable length struts stay mechanism provided between the boom strut and the jib strut,

[0183] - a luffing assembly comprising a luffing winch and a luffing cable extending between the structure and the boom member to determine a luffing angle of the boom member,

[0184] - a main hoist winch, a main hoist cable, and a main hoist block, wherein the main hoist cable extends from the hoist winch along the boom section and the jib section via a jib head sheave assembly on the jib head to the main hoist block,

[0185] - a boom rest, wherein the foldable boom is configured to assume at least:

[0186] - a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,

[0187] - a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, and wherein the jib strut is configured - when the crane boom is in the folded and parked position thereof, e.g. substantially horizontally resting on the boom rest - to be moved into an upward oriented position, e.g. a substantially vertically upward oriented position.

[0188] The fifth aspect of the invention also relates to a method of operating the crane of the offshore vessel.

[0189] In an embodiment, with boom member in its raised position and with the jib member being fixated relative to the boom member in a fully folded configuration, the jib strut is first reoriented in upward direction, substantially in line with the boom member, followed by operating the luffing winch(es) to bring the folded boom in the folded and parked configuration wherein jib member and jib strut are substantially horizontal, and then the jib strut is reoriented to an upward oriented position, e.g. a substantially vertically upward oriented position.

[0190] It will be appreciated that the vessel according to the second and / or third aspect and / or fourth aspect and / or fifth aspect of the invention may further comprise one or more technical features discussed herein in the context of the first aspect of the invention, e.g. as in the claimset, e.g. as in one or more of the subclaims.

[0191] The present invention also relates to an offshore crane as described herein, e.g. according to one or more of the first, second, third, fourth, and / or fifth aspect, the crane comprising a crane base which is secured or configured to be secured to a hull of an offshore crane vessel, a revolving structure which is supported by the crane base and rotatable about a slew axis relative to the crane base, and a foldable boom.

[0192] The present invention also relates to a foldable boom for an offshore crane as discussed herein, e.g. in view of retrofitting an existing offshore crane with the inventive foldable boom.

[0193] The present invention also relates to a method for retrofitting an existing offshore crane, e.g. onboard of an offshore crane vessel, e.g. a jack-up vessel, with a foldable boom as discussed herein.

[0194] The invention will now be described with reference to the drawings. In the drawings:

[0195] - Fig. 1 shows a first example of a jack-up offshore crane vessel according to the invention with the boom thereof in raised position,

[0196] - Fig. 2 shows the lowering of the ends of the first and second auxiliary lines onto the deck and their connection being made,

[0197] - Figs. 3 - 6 illustrate a folding routine wherein the boom of the crane of figure 1 is folded,

[0198] - Fig. 7 illustrates reorienting the jib strut after the folding and parking of the boom has been completed,

[0199] - Fig. 8 shows a second example of a jack-up offshore crane vessel according to the invention with the boom thereof in raised position,

[0200] - Figs. 9 - 12 illustrate a folding routine wherein the boom of the crane of figure 8 is folded,

[0201] - Fig. 13 illustrates reorienting the struts after the folding of the boom has been completed, - Fig. 14 shows the vessel of figure 8 in transit mode with the boom in folded and parked configuration resting on the boom rest of the vessel,

[0202] - Fig. 15 shows on a larger scale the boom in folded and parked configuration resting on the boom rest of the vessel,

[0203] - Fig. 16 shows the vessel of figure 8 in transit mode from above, with a nacelle and one or more rotor blades loaded on the deck of the vessel,

[0204] - Fig. 17 shows an embodiment of the crane of figure 8 with the boom in raised position,

[0205] - Fig. 18 shows on a larger scale a portion of the boom member, jib member, boom strut, jib strut, and stays of the crane of figure 17,

[0206] - Figs. 19-20 show the crane according to the invention being used to instal a wind turbine blade to a nacelle,

[0207] - Figs. 21a-e show the different steps of the folding routine of a crane according to the invention,

[0208] - Fig. 22 shows a detailed view of the boom and jib strut of the crane shown in Figs. 21a-e,

[0209] - Fig. 23 shows a detailed view of the jib head of the crane shown in Figs. 21a-2e,

[0210] - Fig. 24 shows a detailed view of the jib head shown in Fig. 23 being received between the leg portions of the boom member,

[0211] - Fig. 25 shows an isometric view of an example of a jack-up offshore crane according to the invention in the folded and parked position.

[0212] The figures 1 - 16 show a jack-up offshore crane vessel 1 having a hull 2 and jack-up legs 3, here four jack-up legs, two at the bow and two at the stern. Other arrangements of the jack-up legs are also envisaged.

[0213] The hull 2 can be lifted out of the water by lowering the legs 3 onto the seabed 5 and then operating jack-up mechanisms (known in the art) so that the hull 2 is above the water level, indicated with w in figure 1. This stabilizes the hull 2.

[0214] The vessel 1 preferably has its own propulsion, e.g. using thrusters as shown.

[0215] The vessel 1 has an around-the-leg crane 20 which will be discussed in great detail below.

[0216] In figures 1 - 7 a first example of the crane 20 is shown, in figures 8 - 16 a second example of the crane is shown. The differences in construction and operation, as well as optional features, are discussed below in more detail.

[0217] The vessel 1 has a boom rest 8 for the foldable boom 30 of the crane 20. In this example, at the bow, the vessel 1 has a superstructure 9 with a bridge and crew quarters as well as a helideck.

[0218] The vessel has, aft of the superstructure 9, a deck 6 on which, for example, wind turbine components can be loaded.

[0219] The crane 20 comprises:

[0220] - a crane base 21 which is secured to the hull,

[0221] - a revolving structure 22 which is supported by the crane base 21 and rotatable about a slew axis 23 relative to the crane base,

[0222] - the foldable boom 30 mounted to the revolving structure 22.

[0223] The crane base 21 here is configured to extend about a leg 3 of the vessel. In other example, the crane base is secured to the hull remote from a jack-up leg 3. In other example, the vessel does not have any jack-up legs, e.g. the vessel being a monohull vessel or a semisubmersible vessel.

[0224] In embodiments, the crane base 21 extends significantly above the deck 6 of the hull 2, e.g. more than 10 meters, e.g. about 25 meters, with the revolving structure 22 being mounted on top of the crane base 21.

[0225] In embodiments, as shown, the boom rest 8 is mounted at the bow of the vessel 1 , e.g. protruding forward of the hull 2 as the folded boom 30 also extends forward of the hull 2 in the folded and parked configuration, e.g. with jib strut 54 being generally horizontal and extending in forward direction. The folded boom 30 rests with the jib member 51 thereof on the boom rest 8. The boom member 41 is parallel to the jib member 51 , and both are generally horizontal.

[0226] It is shown, as preferred, that the parked folded boom 30 is at significant height above the deck 6, e.g. more than 10 meters, e.g. more than 20 meters, e.g. allowing for storage of wind turbine components, like rotor blade(s) 200 and / or nacelle(s) 210 on deck.

[0227] It is illustrated that the revolving structure 22 comprises a crane housing 24, here configured to extend about the jack-up leg 3 of the vessel, which is rotatable to allow for slew motion of the revolving structure relative to the crane base 21 around the vertical slew axis. The structure 22 further comprises a luffing frame structure 25 mounted on top of the crane housing 24.

[0228] As shown in the figures, the foldable boom 30 comprises a boom section 40 comprising:

[0229] - a boom member 41 having a length of at least 40 meters, the lower end of which is pivotally mounted about a horizontal boom pivot axis 42 to the revolving structure 22,

[0230] - a boom strut 44, an inner end of which is mounted to an upper end of the boom member 41 , and

[0231] - a boom stay 45 provided between the boom member 41 and the boom strut 44.

[0232] The foldable boom 30 also comprises a jib section 50 comprising:

[0233] - a jib member 51 having a length of at least 30 meters, here of about 68 meters, an inner end of which is pivotally mounted about a horizontal jib pivot axis 52 to the upper end of the boom member 41 , which jib member has a jib head 53 at an outer end thereof,

[0234] - a pivotal jib strut 54, an inner end of which is pivotally mounted to the inner end of the jib member 51 , and

[0235] - a jib stay 55 provided between the jib member 51 and the jib strut 54.

[0236] The foldable boom 30 further has a variable length struts stay mechanism 60 provided between the boom strut 44 and the jib strut 54.

[0237] The crane 20 further comprises a luffing assembly with one or more luffing winches 100 and one or more luffing cables 101 extending between the revolving structure 22, here the luffing frame structure 25 thereof, and the boom member 41 to determine a luffing angle of the boom member 41.

[0238] It is illustrated that the luffing assembly comprises left-hand and right-hand luffing cable sheave sets at a top of the luffing frame structure 25, and left-hand and right-hand luffing cable sheave sets on the upper end of the boom member, wherein luffing cables 101 driven by luffing winches 100 extend between the sheave sets, here on opposite sides of the jack-up leg 3. The winches 100 are mounted on the revolving structure 22.

[0239] The crane 20 further comprises a main hoist winch 70, a main hoist cable 71, and a main hoist block 72, wherein the main hoist cable extends from the hoist winch along the boom section 40 and the jib section 50 via a jib head sheave assembly 73 on the jib head 53 to the main hoist block 72. In the depicted embodiment of figure 1 , the hook of the main hoist block is 175 meters above deck level of the vessel 1.

[0240] In an embodiment, the crane 20 further comprises a tugger system with one or two tugger lines 111 and corresponding tugger winches. The tugger lines 111 depart form the boom member 41, but could also depart from the revolving structure 22.

[0241] The crane 20 comprises a sling hoist system comprising one or more sling hoist lines 110 and corresponding sling host winches. The one or more sling hoist lines 110 depart from the upper end of the jib section 51 , e.g. the gooseneck 53.

[0242] The tugger line(s) 111 and the sling hoist line(s) 100 are to be connected to each other in a preferred operational method which is explained herein.

[0243] The foldable boom 20 is configured to assume at least:

[0244] - a raised boom configuration, see figure 1 and 8, wherein the boom is extended as both the boom member 41 and the jib member 51 are in a raised position,

[0245] - a folded and parked configuration, see figure 7 and 14, wherein the boom 30 is folded as the jib member 51 is folded along the boom member 41 , and wherein the folded boom is parked on the boom rest 8.

[0246] As shown in the figures 1 - 7, the boom stay 45 is formed by a fixed length boom stay assembly 49. So its length cannot be varied, contrary to the second example shown in the figures 8 - 18.

[0247] As will be explained in more detail, the jib stay 55 comprises a variable length jib stay mechanism 56.

[0248] The variable length struts stay mechanism 60 and the variable length jib stay mechanism 56 each have an associated drive. It is illustrated that each of the variable length struts stay mechanism 60 and the variable length jib stay mechanism 56 comprises a stay mechanism winch 62, 57 and a winch driven cable 63, 58 reeved in a multi-fall arrangement between associated sheave sets. The stay mechanism winches 62, 57 are mounted on the revolving structure.

[0249] The variable length jib stay mechanism 56 comprises a corresponding stay mechanism winch and a winch driven cable reeved between a first and second jib sheave set 56a, 56b, wherein the first jib sheave set 56a is connected to the jib strut 54 and wherein the second jib sheave set 56b is connected to the fixed length jib stay assembly 59.

[0250] It is illustrated that the jib stay 55 comprises the variable length stay mechanism 56 as well as a fixed length stay assembly 59. Herein, the variable length jib stay mechanism 56 adjoins the jib strut.

[0251] It is illustrated that the variable length struts stay mechanism 60 is at one end thereof connected the pivotal boom strut 44 and at the other end thereof to the pivotal jib strut 54.

[0252] It is illustrated that the boom strut 44 and the jib strut 54 each have a length of at least 8 meters, here about 10 meters or more, here about 30 meters for the jib strut.

[0253] It is illustrated that the crane has a boom stop assembly, wherein a boom stop member 121 on the revolving structure, e.g. on the luffing frame structure thereof, is configured to contact a boom stop member 122 on the boom member 41. The raised position of the boom member 41 during a folding routine of the boom 30 is defined by the boom stop members 121 , 122 contacting one another.

[0254] As follows from the figures 1 - 7, in an embodiment, the crane is configured to, e.g. a controller associated with the winch drives of the variable length jib stay mechanism 56 and the variable length struts stay mechanism 60 is programmed to, perform a folding routing wherein the boom is brought from the raised boom configuration, see figure 1 , into a folded configuration, see figure 7.

[0255] The figures 1 - 7 illustrate an embodiment of the folding routine comprising, starting from the raised boom configuration and with the boom member 41 being maintained in its raised position by the luffing assembly 22.

[0256] Figure 2 shows that the sling winches and tugger winches have been operated to lower the sling hoist line(s) 110 and the tugger line(s) 111 respectively, such that the ends thereof are at the deck 6 of the vessel 1. The ends are then connected to each other such that the sling line(s) 110 and the tugger line(s) 111 form an interconnected line extending from the boom member 41 to the upper end of the jib section 51. By operating the sling and / or tugger winches the interconnected line may provide a controlled tension on the jib section 51 while (un)folding, thereby allowing for a more controlled (un)folding procedure. The crane 20 may be slewed about the slew axis to change the deck location at which the sling line(s) 110 and the tugger line(s) 111 are connected to each other.

[0257] The drive 62 of the variable length struts stay mechanism 60 is then operated to lengthen the struts stay mechanism 60, as shown in Figure 3. The jib member 51 is pivoted downward with respect to the boom member 41 around pivot axis 52. The interconnected lines 110, 111 are pulled taught and can later be used to pull the upper end of the jib member 51 towards the boom member 41 into the fully folded configuration.

[0258] The drive 57 of the variable length jib stay mechanism 56 is then operated so as to lengthen the jib stay mechanism 55, as shown in Figure 4. This causes the jib member 51 to pivot with respect to the boom member 41 and with respect to the jib stay 54, so as to achieve a plumb line orientation of the jib member 51. The jib stay 54, preferably, does not move with respect to the boom member 41 in this step.

[0259] The figures 3 - 4 suggest that the actions are performed in succession. It is also possible to perform multiple or all of these actions in timed overlap, or even all simultaneously. Herein, preferably, these actions are done so as to vary the orientation of the strut 55 relative to the jib member 51 and thereby optimize the loads on the parts of the crane boom during the folding. Of course, the unfolding of the boom 30 may be done in reverse.

[0260] It is illustrated in figures 1 - 7 that the boom strut 44 includes a fixed angle of between 75° - 85° with the boom member 41 , e.g. about 80°.

[0261] It is illustrated in Figure 4 that, in the folded configuration, the pivotal jib strut includes an obtuse angle of between 150° - 180° with the jib member.

[0262] It is illustrated in Figure 4 that, in the folded configuration, the jib strut 54 and the boom strut 44 include an angle of between 70° - 110°.

[0263] It is illustrated that the raised position of the boom member 41 may be near-vertical, yet not vertical (as otherwise the boom member 41 might drop backward).

[0264] Figure 4 shows that there will be a relatively small gap between the raised boom member 41 and the jib member 51 in the plumb line orientation thereof. For example, the jib member includes an angle of less than 15° with the raised boom member, e.g. less than 10°, e.g. just a few degrees. This gap can be vastly smaller than the folded configuration of figure 2a in WO2018088900 due to the inventive arrangement of variable length stay mechanisms and pivotal struts.

[0265] In order to pull the jib member 51 from its plump line orientation of figure 4 further towards the boom member 41 in its raised position into a fully folded configuration of Figure 5, the crane is provided with a pull-in and fixation mechanism 80. This mechanism 80 is adapted to pull the jib member 51 from its plump line orientation further towards the boom member 41 in its raised position into the fully folded configuration and to establish fixation of the jib member 51 relative to the boom member 41 in said fully folded configuration.

[0266] In embodiments, the interconnected sling hoist line(s) 110 and the tugger line(s) 111 are used as pull-in and fixation mechanism 80.

[0267] By operating the luffing assembly 22, with the boom in the fully folded and fixated configuration, the folded boom 30 is lowered onto the boom rest 8 of the vessel, e.g. into a horizontal position, as shown in Figure 6 in order to establish the folded and parked configuration of the boom 30, e.g. in the course of bringing the vessel in transit mode.

[0268] It is illustrated that the jib head is a gooseneck jib head 53, which is configured such that in a folded configuration of the boom 30, wherein the boom member 41 is in its raised position and the jib member 51 is in the plumb line orientation, the jib head 53 reaches the boom member 41. As preferred and illustrated, in this position, the gooseneck jib head 53 extends into the structure of the boom member 41.

[0269] A fixation mechanism can be mounted on one or both of the boom member 41 and the gooseneck jib head 53.

[0270] For example, the fixation mechanism 80 comprises one or more actuator operated fixation pins which fixated the jib head 53 relative to the boom member 41.

[0271] It is illustrated that the gooseneck jib head 53 is provided with a main hoist block receiving assembly 90, e.g. a cradle, which is configured to receive the main hoisting block 72 during folding of the boom 30. As preferred, the receiving assembly comprises a locking arrangement 91 configured to lock in place the received main hoisting block 72.

[0272] The vessel comprises a retention member 112 which retains the second jib sheave set 56b, when crane is in the folded and parked position. The retention member 112 extends from the jib section. The retaining member 112 ensures that the second jib sheave set 56b cannot move when retained.

[0273] As shown in Figure 6, the drive 62 of the variable length struts stay mechanism 60 is operated in to shorten the struts stay mechanism 60, thereby pivoting the jib stay 54 from a substantially horizontal orientation shown in Figure 5 to a substantially vertically upward orientation. In this vertically upward orientation of the jib stay 54 the total length of the folded boom is shortened and the length of the crane that extends out of the contour of the vessel 1 is shortened. During this pivoting of the jib stay 54, the second jib sheave set 56b is retained in the same position by the retaining member 112, thereby ensuring that the fixed length jib stay assembly 59 remains parallel to the jib section 51.

[0274] Figures 8 - 18 show a second example of the crane 20.

[0275] In this embodiment, the boom strut 44 is a pivotable boom strut 44, an inner end of which is pivotally mounted to the upper end of the boom member 41. The boom stay 45 comprises a variable length boom stay mechanism 46 and, as preferred, also a fixed length boom stay mechanism 46. The variable length boom stay mechanism has an associated drive 47. By comprising a pivotable boom strut 44 and a variable length boom stay mechanism 60, the geometry of the struts can be optimized.

[0276] The crane 20 of figures 8 - 18 is configured to, e.g. a controller associated with the winch drives of the variable length boom stay mechanism 46, the variable length struts stay mechanism 60, and the variable length jib stay mechanism 56 is programmed to, perform a folding routine wherein the boom 30 is brought from the raised boom configuration, see figure 8, into a folded configuration, see figure 12.

[0277] The figures 8 - 14 illustrate that the folding routine comprising, starting from the raised boom configuration and with the boom member 41 being maintained in its raised position by the luffing assembly: a) operating the winch drive of the variable length struts stay mechanism 60 so as to lengthen the struts stay mechanism 46, see figure 9, b) operating the winch drive of the variable length boom stay mechanism 46 so as to lengthen the boom stay mechanism, see figure 10, c) operating the winch drive of the variable length jib stay mechanism 56 so as to lengthen the jib stay mechanism, see figure 11 , wherein the actions a), b), and c) are performed so as to achieve a plumb line orientation of the jib member 51 , see figure 11.

[0278] The figures 8 - 14 suggest that the actions a), b), and c) are performed in succession. It is also possible to perform multiple or all of these actions in timed overlap, or even all simultaneously. Herein, preferably, these actions are done so as to vary the orientation of the struts 45, 55 relative to the respective boom member 41 and jib member 51 and thereby optimize the loads on the parts of the crane boom during the folding. Of course, the unfolding of the boom 30 may be done in reverse.

[0279] It is illustrated in Figure 11 that, in the folded configuration, the boom strut includes an obtuse angle of between 110° - 140° with the boom member.

[0280] It is illustrated in Figure 11 that, in the folded configuration, the jib strut includes an obtuse angle of between 120° - 160° with the jib member.

[0281] It is illustrated in Figure 11 that, in the folded configuration, the jib strut 54 and the boom strut 44 include an angle of between 70° - 110°.

[0282] In order to pull the jib member 51 from its plump line orientation of figure 11 further towards the boom member 41 in its raised position into a fully folded configuration of figure 11 , the crane is provided with a pull-in and fixation mechanism 80. This mechanism 80 is adapted to pull the jib member 51 from its plump line orientation further towards the boom member 41 in its raised position into the fully folded configuration and to establish fixation of the jib member 51 relative to the boom member 41 in said fully folded configuration.

[0283] The Figure 12 shows that once the jib member 51 is fixated relative to the boom member 41 in the fully folded configuration, the drives of the variable length stay mechanism can be operated to reorient one or both of the struts 45, 55, e.g. in view of the optimal orientation for the parking of the folded boom 30 on the boom rest 8, e.g. the jib strut 54 being reoriented so that the jib stay 54 becomes parallel to the jib member 51 as shown in figure 6, 7, and 8.

[0284] By operating the luffing assembly, with the boom in the fully folded and fixated configuration, the folded boom 30 is lowered onto the boom rest 8 of the vessel in order to establish the folded and parked configuration of the boom 30, e.g. in the course of bringing the vessel in transit mode. It is illustrated in Figure 11 that the jib head is a gooseneck jib head 53, which is configured such that in a folded configuration of the boom 30, wherein the boom member 41 is in its raised position and the jib member 51 is in the plumb line orientation, the jib head 53 reaches the boom member 41. As preferred and illustrated, in this position, the gooseneck jib head 53 extends into the structure of the boom member 41. A fixation mechanism, e.g. a pull-in and fixation mechanism 80, is mounted on one or both of the boom member 41 and the gooseneck jib head 53.

[0285] For example, the fixation mechanism 80 comprises one or more actuator operated fixation pins which fixated the jib head 53 relative to the boom member 41.

[0286] It is illustrated that the gooseneck jib head 53 is provided with a main hoist block receiving assembly 90, e.g. a cradle, which is configured to receive the main hoisting block 72 during folding of the boom 30. As preferred, the receiving assembly comprises a locking arrangement 91 configured to lock in place the received main hoisting block 72.

[0287] Figures 19 and 20 show the crane 20 being used to install a wind turbine blade 200 to a nacelle 210 mounted on top of a wind turbine mast 220, wherein the crane 20 is in the unfolded configuration. The wind turbine blade 200 is hoisted by the main hoist cable 71.

[0288] The crane 20 is provided with a tagline system for controlling the load 200 which is handled by the crane. The tagline system comprises one or more tagline trolleys 130 which are movable along the jib member 51, a tagline winch and a winch driven tagline 131 , which tagline 131 - in use of the crane - extends from the tagline trolley 130 to the load 200. The tugger lines 111 extend from a lower end of the boom section to the load 200 and is further used to control the load.

[0289] In use, the boom member 41 and the jib member 51 each have a front facing side and a back facing side. The front facing side being the side of the boom member 41 and the jib member 51 that face the main hoist block 72 when the foldable boom is in the raised boom configuration.

[0290] In an embodiment shown in Figures 21a - 22, the boom strut 44 comprises two boom strut members 44a, 44b which are each connected to the upper end of the boom member 41 at the back facing side thereof. When seen in the vertical plane, such as is shown in Figure 1, the two boom strut members 44a, 44b coincide. The two boom strut members 44a, 44b are interconnected to each other by multiple boom strut cross members 44c. Likewise, the jib strut 54 comprises a first and second jib strut member 54a, 54b which are each connected to the inner end of the jib member 51 at the front facing side thereof. The two jib strut members 54a, 54b extend such that - when seen in the vertical plane - the two jib strut members 54a, 54b coincide. The two jib strut member 54a, 54b are interconnected to each other by multiple jib strut cross members 54c.

[0291] The boom stay 45 comprises a first and second boom stay member 45a, 45b which extend between the boom member 41, at the lower end thereof, and respectively the first and second boom strut member 44a, 44b. The jib stay 55 comprises a first and second jib stay member, each comprising a respective variable length jib stay mechanism 56a, 56b and a fixed length jib stay 59a, 59b, which extend between the jib member and respectively the first and second jib strut member 54a, 54b.

[0292] The variable length struts stay mechanism 60 comprises a first and second winch driven cable 60a, 60b reeved in a multi-fall arrangement between associated sheave sets 61a, 61b. The first and second boom strut members 44a, 44b and the first and second jib strut members 54a, 54b each being provided with a sheave sets 61a, 61b, such that the first winch driven cable 60a extends between the first boom strut member 44a and the first jib strut member 54a, and the second winch driven cable extends between the second boom strut member 44b and the second jib strut member 45b.

[0293] The first and second jib strut member 54a, 54b diverge with respect to each other from the jib member 51 such that the lateral distance between the jib strut members along the length of the jib strut members increased. The attachment point of the variable length first and second jib stay members 56a, 56b is located laterally further away from the jib member 51, thereby increasing the angle between the first and second jib stay members and the jib member 51 when seen in a front facing view, e.g. looking directly at the front facing side of the boom member and the jib member.

[0294] The boom member 41 and the jib member 51 have a continuous tapering configuration, e.g. the front and back chords of the jib member extend substantially in line with the respective front and back chords of the boom member.

[0295] The first and second boom stay members 45a, 45b are laterally spaced from one another, and the luffing cables 101a, 101b are located laterally between the boom stay members 45a, 45b. The luffing assembly comprises a first and second luffing cable 100a, 100b extending from laterally spaced apart locations from the luffing frame structure 25, as can be seen in Figure 21 , to two laterally spaced apart locations on the outer end of the boom member 51. Both the first and second luffing cable 100a, 100b are located laterally between the two laterally spaced apart boom stay members 45a, 45b.

[0296] The crane shown in Figures 21a-22 comprises a fixed length boom stay 44. The crane is shown in different stages of the transition between the raised boom configuration, shown in Fig 21a to the folded and parked configuration. As can be seen in the Figures 21a-e, the main hoist cable 71 vertically extends downward from the jib head sheave assembly 53 to the hoist main block 72 during the entire folding procedure. In the folded and parked configuration as shown in Figure 21e, the main block 72 extends vertically downward from the jib head sheave assembly 53, such that the block 72 may be stored on the deck of the vessel.

[0297] As the foldable boom transitions from the raised operating configuration shown in Fig. 21a to the fully folded and parked configuration shown in Fig. 21e, the jib head rotates from an upright orientation to an inverted orientation, as illustrated in Fig. 21c. Throughout this rotational movement, the main hoist cable 71 and the hoist block 72 maintain a substantially vertical downward orientation. Consequently, while the jib head 53 rotates, the main hoist cable 71 and block 72 pivot relative to the jib head 53 itself, remaining suspended in a vertical line and thus rotating only in relation to the changing orientation of the jib head 53. To maintain this vertical alignment and ensure continuous engagement of the hoist block 73, the jib head sheave assembly 73 is provided with two catch sheaves 74, as shown in Figure 23, configured to support and constrain the main hoist cable 71 during the entire movement of the jib between the raised and folded positions. Each catcher 74 comprises a cable-engaging surface or cradle that engages and supports the cable as the jib rotates, preferably holding the cable already in the raised configuration as shown in Figure 23. As the geometry changes, the catchers 74 guides the main hoist cable 71 remains properly engaged with the hoist block 73 at all times.

[0298] As can be seen in Figure 24, the boom member 41 has inner leg portions 41 a, 41 b which are at the inner end thereof pivotally mounted to the revolving structure 21. The inner leg portions 24a, 41b at the outer end thereof adjoining a latticed box structured part of the boom member having longitudinal chords at corners thereof with bracing members between the longitudinal chords. The inner leg portions 41a, 41b are laterally spaced apart from each other, thereby defining a space between them. In the folded configuration, shown in Figure 21c and in a more detailed view in Figure 24 the jib head 53 is received in the space between the inner leg portions 41a, b.

[0299] In a different embodiment of the crane as shown clearly in Figures 17 and Figure 25, the boom strut 44 and the jib strut 54 are each formed by a single latticed box structures 44, 54. the luffing cables 101 extending between the revolving structure 22 and the outer end of the boom member 41. The boom stay 45 comprises a connection member 45c which is connected to the boom strut. The connection member 45c provides laterally spaced apart attachment points for the first and second boom stay members 45a, 45b such that the first and second boom stay members are laterally spaced from one another, and the luffing cables 101 can be located laterally between the boom stay members 45a, 45b.

[0300] As can be seen in figure 17, it is preferred that both the boom member 41 and the jib member 54 are over their length of a tapered design when seen from the front. Herein the lateral sides of the boom member 41 define a greater width near the lower end than the width at the upper end of the boom member. The lateral sides of the jib member 54 define a greater with near the inner end than the width at the outer end of the jib member. It is shown here, as preferred, that the front side and rear side of the boom member 41 are generally parallel to one another. Also, preferably, the front side and the rear side of the jib member 54 are parallel to one another. Due to the tapering shape of both the boom member and the jib member and enhanced stability of these members is obtained, e.g. in view of sidelead loads on the crane, and / or in view of loads during the process of folding and unfolding.

Claims

- 36 -C L A I M S1. Offshore crane vessel (1) comprising:- a hull (2);- a crane (20) comprising:- a crane base (21) which is secured to the hull,- a revolving structure (22) which is supported by the crane base and rotatable about a slew axis relative to the crane base,- a foldable boom (30) mounted to the revolving structure, the foldable boom comprising:- a boom section (40) comprising:- a boom member (41) having a length of at least 40 meters, the lower end of which is pivotally mounted about a horizontal boom pivot axis (42) to the revolving structure (22),- a boom strut (44), an inner end of which is mounted to an upper end of the boom member, and- a boom stay (45) provided between the boom member and the boom strut;- a jib section (50) comprising:- a jib member (51) having a length of at least 30 meters, an inner end of which is pivotally mounted about a horizontal jib pivot axis (52) to the upper end of the boom member, which jib member has a jib head (53) at an outer end thereof,- a pivotal jib strut (54), an inner end of which is pivotally mounted to the inner end of the jib member or to the upper end of the boom member, and- a jib stay (55) provided between the jib member and the jib strut;- a variable length struts stay mechanism (60) provided between the boom strut and the jib strut,- a luffing assembly comprising a luffing winch (100) and a luffing cable (101) extending between the revolving structure (22) and the boom member (41) to determine a luffing angle of the boom member,- a main hoist winch (70), a main hoist cable (71), and a main hoist block (72), wherein the main hoist cable extends from the main hoist winch along the boom section (40) and the- 37 - jib section (50) via a jib head sheave assembly (73) on the jib head (53) to the main hoist block,- a boom rest (8), wherein the foldable boom (30) is configured to assume at least:- a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,- a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, wherein the jib stay (55) comprises a variable length jib stay mechanism (56), and wherein the variable length struts stay mechanism (60) and the variable length jib stay mechanism (56) each have an associated drive (62, 57).

2. Offshore crane vessel according to claim 1, wherein the boom stay is formed by a fixed length boom stay assembly (49), or wherein the boom stay comprises a variable length boom stay mechanism (46) having an associated drive (47).

3. Offshore crane vessel according to claim 1 or 2, wherein the boom strut (44) and the jib strut (54) each have a length of at least 8 meters, e.g. at least 16 meters, for example the jib strut has a length of 30 meters and the jib of 70 meters.

4. Offshore crane vessel according to any one or more of claims 1 - 3, wherein the boom stay is formed by a fixed length boom stay assembly (49), and wherein the crane (20) is configured to perform a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member (41) being maintained in its raised position: a) operating the drive (62) of the variable length struts stay mechanism (60) so as to lengthen the struts stay mechanism, b) operating the drive (57) of the variable length jib stay mechanism (56) so as to lengthen the jib stay mechanism, wherein a), and b) are performed so as to achieve a plumb line orientation of the jib member5. Offshore crane vessel according to any one or more of claims 1 - 3, wherein the boom stay comprises a variable length boom stay mechanism (46) having an associated drive (47), and wherein the crane (20) is configured to perform a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member (41) being maintained in its raised position: a) operating the drive (62) of the variable length struts stay mechanism (60) so as to lengthen the struts stay mechanism, b) operating the drive (47) of the variable length boom stay mechanism (46) so as to lengthen the boom stay mechanism, c) operating the drive (57) of the variable length jib stay mechanism (56) so as to lengthen the jib stay mechanism, wherein a), b) and c) are performed so as to achieve a plumb line orientation of the jib member (51).

6. Offshore crane vessel according to any one or more of claims 1 - 5, wherein the crane is provided with a pull-in and fixation mechanism (80; 110,111) adapted to pull the jib member (51) from a plump line orientation thereof further towards the boom member (41) in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

7. Offshore crane vessel according to any one or more of claims 1 - 6, wherein the crane is configured to, with the boom (30) in said folded, e.g. said fully folded, configuration, operate the luffing winch (100) so as to lower the folded boom onto the boom rest (8) in order to establish the folded and parked configuration.

8. Offshore crane vessel according to any one or more of claims 1 - 7, wherein the jib head is a gooseneck jib head (53) which is configured such that in a folded configuration of the boom, wherein the boom member is in its raised position and the jib member is in a plumb line orientation thereof, the jib head (53) reaches the boom member (41), preferably extends into the boom member.

9. Offshore crane vessel according to claim 8, wherein a fixation mechanism (80), e.g. a pull-in and fixation mechanism, is mounted on one or both of the boom member and the gooseneck jib head, e.g. wherein the fixation mechanism (80) comprises one or more actuator operated fixation members, e.g. pins.

10. Offshore crane vessel according to any one or more of claims 1 - 9, wherein the jib stay mechanism comprises the variable length jib stay mechanism (60) as well as a fixed length jib stay assembly (59), wherein the variable length jib stay mechanism comprises a corresponding stay mechanism winch and a winch driven cable reeved between a first jib sheave set and a second jib sheave set, wherein the first jib sheave set is connected to the jib strut and wherein the second jib sheave set is connected to the fixed length jib stay assembly (59).

11. Offshore crane vessel according to claim 10, wherein the vessel comprises a retention member (112) which is configured to retain the second jib sheave set (56b) when crane boom is in the folded and parked position, e.g. wherein the retention member extends from the boom rest (8) or from the jib member or the boom member.

12. Offshore crane vessel according to any one or more of claims 1 - 11 , wherein the jib strut (54) is configured - when the boom is in the folded and parked position thereof - to be moved into an upward oriented position, e.g. a substantially vertically upward oriented position.

13. Offshore crane vessel according to any one or more of claims 1 - 12, wherein the crane comprises a first auxiliary winch drive line system comprising a first auxiliary line (111) and an associated winch, the first auxiliary line departing from the revolving structure or from the boom member (41), and wherein the crane comprises a second auxiliary winch drive line system comprising a second auxiliary line (110) and an associated winch, the second auxiliary line departing from the outer end of the jib member (51),14. Offshore crane vessel according to claim 13, wherein the first and second auxiliary lines (110,111) are connectable to one another to form part of a pull-in and fixation mechanism (80) which is adapted to pull the jib member (51) from a plump line orientation thereof further towards the boom member (41) in the raised position thereof into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

15. Offshore crane vessel according to claim 13 or 14, wherein the first auxiliary winch drive line system is a tugger winch system comprising a tugger line (111), and wherein the second auxiliary winch drive line system is a sling hoist winch system comprising a sling hoist line (110).

16. Offshore crane vessel according to any one or more of claims 1 - 15 , wherein each of the variable length struts stay mechanism, the variable length jib stay mechanism, and optionally the variable length boom stay mechanism, comprises a stay mechanism winch (47, 62, 57) and a winch driven cable reeved in a multi-fall arrangement between associated sheave sets, e.g. wherein said stay mechanism winches are mounted on the revolving structure.

17. Offshore crane vessel according to any one or more of claims 1 - 16, wherein the jib stay comprises the variable length stay mechanism (60,56) as well as a fixed length stay assembly (59), e.g. the variable length jib stay mechanism adjoining the jib strut, e.g. wherein the variable length struts stay mechanism is at one end thereof connected the boom strut and at the other end thereof to the jib strut, and optionally, wherein the boom stay is formed by a fixed length stay assembly (49), or wherein the boom stay comprises a variable length boom stay mechanism (46) as well as a fixed length stay assembly (49), e.g. the variably length boom stay mechanism adjoining the boom strut.

18. Offshore crane vessel according to any one or more of claims 1 - 17, wherein both the boom member (41) and the jib member (54) are over their length of a tapered design when seen from the front, wherein lateral sides of the boom member (41) define a greater width near the lower end than the width at the upper end of the boom member, and wherein lateral sides of the jib member (54) define a greater with near the inner end than the width at the outer end of the jib member.

19. Method of operation of the crane of an offshore crane vessel according to one or more of claims 1 - 18, wherein the boom stay is formed by a fixed length boom stay assembly (49), wherein the method comprises performing a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive of the variable length struts stay mechanism so as to lengthen the struts stay mechanism, b) operating the drive of the variable length jib stay mechanism so as to lengthen the jib stay mechanism, wherein a), and b) are performed so as to achieve a plumb line orientation of the jib member.

20. Method of operation of the crane of an offshore crane vessel according to one or more of claims 1 - 18, wherein the boom stay comprises a variable length boom stay mechanism- 41 -(46) having an associated drive (47), and wherein method comprises performing a folding routine wherein the boom is brought from the raised boom configuration into a folded configuration, the folding routine comprising, starting from the raised boom configuration and with the boom member being maintained in its raised position: a) operating the drive (62) of the variable length struts stay mechanism (60) so as to lengthen the struts stay mechanism, b) operating the drive (47) of the variable length boom stay mechanism (46) so as to lengthen the boom stay mechanism, c) operating the drive (57) of the variable length jib stay mechanism (56) so as to lengthen the jib stay mechanism, wherein a), b) and c) are performed so as to achieve a plumb line orientation of the jib member (51).

21. Method according to claim 19 or 20, wherein the crane is provided with a pull-in and fixation mechanism (80:110,111) which is adapted and operated to pull the jib member from a plump line orientation thereof further towards the boom member which is in the raised position thereof into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

22. Method according to any one of claims 19 - 21 , wherein the method further comprises, with the boom in said folded, e.g. said fully folded, configuration, operating the luffing winch(es) (100) so as to lower the folded boom onto the boom rest (8) in order to establish the folded and parked configuration.

23. Method according to any one of claims 19 - 22, wherein, with the jib member (51) being fixated relative to the boom member (41) in the fully folded configuration, e.g. with the folded boom in the folded and parked configuration, the drives of the variable length jib stay mechanism and of variable length strut stay mechanism are operated to reorient the jib strut (54).

24. Method according to claim 23, wherein, with boom member in its raised position and with the jib member (51) being fixated relative to the boom member (41) in the fully folded configuration, the jib strut (54) is first reoriented in upward direction, substantially in line with the boom member, followed by operating the luffing winch(es) (100) to bring the folded boom in the folded and parked configuration wherein jib member and jib strut are substantially horizontal, and then the jib strut (54) is reoriented to an upward oriented position, e.g. a substantially vertically upward oriented position.- 42 -25. Method according to claim 24, wherein the jib stay mechanism comprises the variable length jib stay mechanism (60) as well as a fixed length jib stay assembly (59), wherein the variable length jib stay mechanism comprises a corresponding stay mechanism winch and a winch driven cable reeved between a first jib sheave set and second jib sheave set, wherein the first jib sheave set is connected to the jib strut and wherein the second jib sheave set is connected to the fixed length jib stay assembly (59), wherein the vessel comprises a retention member (112) which is configured to retain the second jib sheave set, wherein the second jib sheave set is retained by the retention member in a position such that the fixed length jib stay assembly (59) is parallel to the jib member (51).

26. Method according to any one of claims 19 - 25, wherein the jib head is a gooseneck jib head (53) which is configured such that in a folded configuration of the boom, wherein the boom member is in its raised position and the jib member is in the plumb line orientation, the jib head reaches the boom member, preferably extends into the boom member, and wherein a fixation mechanism (80; 110, 111 ), e.g. a pull-in and fixation mechanism, is mounted on one or both of the boom member and the gooseneck jib head and is used to fixate the jib member prior to operating the luffing winch(es) for bringing the folded boom to rest on the boom rest.

27. Method according to any one of claims 19 - 26, wherein the crane comprises a first auxiliary winch drive line system comprising a first auxiliary line and associated winch, the first auxiliary line departing from the revolving structure or from the boom member, and wherein the crane comprises a second auxiliary winch drive line system comprising a second auxiliary line and associated winch, the second auxiliary line departing from the outer end of the jib member, wherein the first and second auxiliary lines are connectable to one another to form part of a pull-in and fixation mechanism, wherein the method comprises, prior to performing step a) of claim 19 or step a) of claim 20:- operating the winches of the first and second auxiliary winch drive line systems so that the first and second auxiliary lines are with an end thereof at the level of a deck of the vessel,- connecting the ends of the auxiliary lines, and wherein the method comprises:- operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the connected auxiliary lines taught, e.g. prior to folding of the jib, and keeping the connected auxiliary lines taught during folding the jib into plump line orientation,- operating one or both of the winches of the first and second auxiliary winch drive line systems to pull the jib member from its plump line orientation further towards the boom- 43 - member in its raised position into a fully folded configuration and to establish fixation of the jib member relative to the boom member in said fully folded configuration.

28. An offshore crane comprising:- a crane base (21) which is secured to the hull,- a revolving structure (22) which is supported by the crane base and rotatable about a slew axis relative to the crane base,- a foldable boom (30) mounted to the revolving structure, the foldable boom comprising:- a boom section (40) comprising:- a boom member (41) having a length of at least 40 meters, the lower end of which is pivotally mounted about a horizontal boom pivot axis (42) to the revolving structure (22),- a boom strut (44), an inner end of which is mounted to an upper end of the boom member, and- a boom stay (45) provided between the boom member and the boom strut;- a jib section (50) comprising:- a jib member (51) having a length of at least 30 meters, an inner end of which is pivotally mounted about a horizontal jib pivot axis (52) to the upper end of the boom member, which jib member has a jib head (53) at an outer end thereof,- a pivotal jib strut (54), an inner end of which is pivotally mounted to the inner end of the jib member or to the upper end of the boom member, and- a jib stay (55) provided between the jib member and the jib strut;- a variable length struts stay mechanism (60) provided between the boom strut and the jib strut,- a luffing assembly comprising a luffing winch (100) and a luffing cable (101) extending between the revolving structure (22) and the boom member (41) to determine a luffing angle of the boom member,- a main hoist winch (70), a main hoist cable (71), and a main hoist block (72), wherein the main hoist cable extends from the main hoist winch along the boom section (40) and the jib section (50) via a jib head sheave assembly (73) on the jib head (53) to the main hoist block,- a boom rest (8), wherein the foldable boom (30) is configured to assume at least:- a raised boom configuration, wherein the boom is extended as both the boom member and the jib member are in a raised position,- a folded and parked configuration, wherein the boom is folded as the jib member is folded along the boom member, and wherein the folded boom is parked on the boom rest, wherein the jib stay (55) comprises a variable length jib stay mechanism (56), and wherein the variable length struts stay mechanism (60) and the variable length jib stay mechanism (56) each have an associated drive (62, 57).

Images