Marine crane and offshore vessel

A marine slewing pedestal crane comprising:

• a stationary pedestal, the stationary pedestal being adapted to be mounted to a vessel;
• a crane housing, the crane housing being mounted to the stationary pedestal and being adapted to slew relative to the stationary pedestal about a vertical slew axis;
• a boom, the boom comprising an inner end connected pivotally about a horizontal boom pivot axis to the crane housing, allowing an up-and-down luffing movement of the boom, and having opposite thereof a forked outer end between which a jib axle extends defining a horizontal jib pivot axis;
• a boom luffing assembly for luffing the boom up and down, the boom luffing assembly comprising a boom luffing winch, mounted on the crane housing, and an associated boom luffing wire, the boom luffing wire extending between the boom luffing winch and the boom;
• a jib, wherein the jib comprises:
• a jib base, wherein the jib base is pivotally connected to the jib axle to allow a pivotal movement of the jib with respect to the boom, and wherein the jib base comprises a jib arm axle that extends perpendicular to the jib axle;
• and
• a jib arm, wherein the jib arm has a base end and an outer end, the base end being pivotally connected to the jib base via a jib arm pivot axis;
• a hoisting assembly for lifting and lowering a load, the hoisting assembly comprising:
• a hoisting winch and an associated hoisting wire;
• and
• a load suspension device,
• wherein the hoisting wire extends from the hoisting winch via a suspension point at an outer end portion of the jib arm to the load suspension device, and the hoist winch allows to vary the length of the hoisting wire and thus to lower and lift the load suspension device;
• a jib positioning assembly, wherein the jib positioning assembly is adapted to support and position the jib with respect to the boom and to actuate the movement of the jib, the jib positioning assembly comprising:
• a jib winch, mounted to the crane housing, and an associated jib tensioner, the jib tensioner extending between the jib winch and the jib arm, wherein the jib tensioner comprises a jib tensioner wire associated with the jib winch and at least a first jib tensioner member;
• and
• a jib tensioner spacer structure, the spacer structure comprising a first, second and third lever arm for supporting the jib tensioner at a first, second and third support point respectively,
• wherein the lever arms are each fixed to the jib base and each extend radially outward from the jib axle such that the support points are spaced in a radial direction and are located at different angular positions relative to the jib axle, and
• wherein the first jib tensioner member extends between the outer end portion of the jib arm and the first support point, and wherein the first jib tensioner member comprises a tensioner member pivot axis or is pivotably connected to the first support point via a tensioner member pivot axis, the tensioner member pivot axis being parallel to the jib arm pivot axis;
• and
• a jib arm positioning assembly, wherein the jib arm positioning assembly is adapted to position the jib arm with respect to the jib base and to actuate the movement of the jib arm, the jib arm positioning assembly comprising:
• one or more jib arm pivot cylinders, the one or more jib arm pivot cylinders being connected with one end to the jib base and an opposite end to the jib arm, for controlling the movement of the jib arm about the jib arm pivot axis;
• and
• a jib arm control system, comprising one or more sensors for monitoring a load connected to the load suspension device, and/or a potential load, and/or a supply vessel supporting a potential load, and/or crane information, and, based on the information of the one or more sensors, actuate the one or more jib arm pivot cylinders to pivot the jib arm relative to the jib base, and make the suspension point follow a load or a potential load in at least one direction, and
• wherein the jib tensioner wire is guided via a heave compensation cylinder for providing the jib with heave compensation and/or the jib winch is provided with a jib winch control system configured for providing the jib with heave compensation.