Hoisting crane for use on an offshore vessel and method of operation

A multi configurations crane system comprising:

• a base structure configured to be mounted on a vessel;
• a superstructure mounted to the base structure, and being provided with:
• a top cable guide at a top thereof;
• and
• a boom connection member defining a horizontal pivot axis;
• a boom having a longitudinal axis, wherein the boom has an inner end connected to the left-hand connector and right-hand connector of the boom connection member, so that the boom can be pivoted up and down about the horizontal pivot axis which is perpendicular to the longitudinal axis of a boom;
• a boom head structure provided at a tip end of the boom;
• a luffing device for pivoting the boom up and down, and comprising a luffing winch and a variable length luffing system, the variable length luffing system extending from the luffing winch via the top cable guide to the boom head structure;
• and
• a hoisting device for hoisting a load, and comprising a hoisting winch and an associated hoisting cable, the hoisting cable extending from the hoisting winch to a main hoist cable guide on the boom head structure,
• wherein the multi configurations crane system comprises at least the following components for assembling the boom:
• a proximal portion configured to be connected to the boom connection member;
• a distal portion comprising the boom head structure to which the variable length luffing system and the hoisting cable extend, wherein the distal portion has a first cross-sectional size in a cross-section perpendicular to a longitudinal axis of the distal portion;
• and
• an intermediate portion, wherein the intermediate portion has a second cross-sectional size in a cross-section perpendicular to a longitudinal axis of the intermediate portion which is smaller than said first cross-sectional size of said distal portion,
• wherein the multi configurations crane system has at least a first configuration and a second configuration, wherein:
• in the first configuration, the intermediate portion is connected to the proximal portion, wherein the distal portion and the intermediate portion are arranged such that their respective longitudinal axes are parallel, wherein an extension mechanism is provided, said extension mechanism being configured to allow the distal portion to be slid relative to the intermediate portion in a longitudinal direction of the boom from a retracted configuration to an extended configuration and vice versa, wherein a locking mechanism is provided for locking the distal portion relative to the intermediate portion in the retracted configuration and in the extended configuration, and wherein in the retracted configuration the intermediate portion is arranged substantially within the distal portion, and
• in the second configuration, the distal portion is connected to the proximal portion, wherein the boom is assembled without the intermediate portion.