A wave-induced motion compensating crane for use on an offshore vessel, vessel and load transferring method

A wave-induced motion compensating crane for use on an offshore vessel, the crane comprising:

• a base structure adapted to be mounted on an offshore vessel;
• a revolving superstructure adapted to revolve about a substantially vertical revolving axis relative to the base structure;
• a boom structure mounted to the superstructure and pivotally connected at a first end thereof to pivot about a substantially horizontal boom pivot axis relative to the superstructure;
• a motion compensation device mounted to a tip end portion of the boom structure;
• a hoist winch, a hoist cable, and an object suspension device suspended from said hoist cable, wherein the hoist winch is mounted on the revolving superstructure or on the boom structure, and wherein the hoist cable extends from the hoist winch to the tip end portion of the boom structure and then along the motion compensation device to the object suspension device;
• a heave compensation device that is configured to act on the hoist cable, wherein the heave compensation device is integrated in the hoist winch and/or arranged to act on the hoist cable intermediate the hoist winch and the tip end portion of the boom structure;
• and
• a control unit,
• wherein the motion compensation device comprises:
• a pedestal member that is pivotally connected to the tip end portion of the boom structure to pivot about a substantially horizontal pedestal member pivot axis which is parallel to the substantially horizontal boom pivot axis;
• a level setting device that is arranged between the boom structure and the pedestal member and that is adapted to set the pedestal member in a levelled position;
• a slewing jib beam support member that is secured to the pedestal member to revolve about a vertical slew axis relative to said pedestal member in said levelled position thereof;
• a slew drive connected to said control unit and adapted to cause controlled slew motion of said jib beam support member about said vertical slew axis;
• a linear displaceable jib beam that is supported by said jib beam support member via one or more jib beam guides that define a linear motion path of the jib beam relative to the jib beam support member, said linear motion path extending substantially horizontal when said pedestal member is in said levelled position;
• and
• a jib beam drive connected to said control unit and adapted to cause controlled linear motion of said jib beam relative to the jib beam support member,
• wherein the jib beam carries a sheave arrangement with a front sheave at a front portion of the jib beam from which the hoist cable extends to a sheave of the object suspension device, with a rear sheave remote from said front sheave, and with a first guide sheave arranged such that said hoist cable extends from a sheave of the object suspension device via the first guide sheave to the jib beam support member and is connected thereto with a terminal end,
• wherein the jib beam support member carries a second guide sheave from which said hoist cable extends to the rear sheave on the jib beam,
• wherein the first and second guide sheaves are arranged so that the length of hoist cable between the second guide sheave on the jib beam support member and the terminal end is substantially constant independent of the linear position of the jib beam relative to the jib beam support member,
• wherein the control unit is configured to provide a wave-induced motion compensation mode wherein the slew drive of the jib beam support member and the jib beam drive of the compensation device are operated to maintain a predetermined X-Y location of the object suspension device, and
• wherein the heave compensation device is configured to compensate wave-induced Z-motion of the object suspension device.

A wave-induced motion compensating crane for use on an offshore vessel, the crane comprising:

• a base structure adapted to be mounted on an offshore vessel;
• a revolving superstructure adapted to revolve about a substantially vertical revolving axis relative to the base structure;
• a boom structure mounted to the superstructure and pivotally connected at a first end thereof to pivot about a substantially horizontal boom pivot axis relative to the superstructure;
• a motion compensation device mounted to a tip end portion of the boom structure;
• a hoist winch, a hoist cable, and an object suspension device suspended from said hoist cable, wherein the hoist winch is mounted on the revolving superstructure or on the boom structure, and wherein the hoist cable extends from the hoist winch to the tip end portion of the boom structure and then along the motion compensation device to the object suspension device;
• and
• a control unit,
• wherein the motion compensation device comprises:
• a pedestal member that is pivotally connected to the tip end portion of the boom structure to pivot about a substantially horizontal pedestal member pivot axis which is parallel to the substantially horizontal boom pivot axis;
• a level setting device that is arranged between the boom structure and the pedestal member and that is adapted to set the pedestal member in a levelled position;
• a slewing jib beam support member that is secured to the pedestal member to revolve about a vertical slew axis relative to said pedestal member in said levelled position thereof;
• a slew drive connected to said control unit and adapted to cause controlled slew motion of said jib beam support member about said vertical slew axis;
• a linear displaceable jib beam that is supported by said jib beam support member via one or more jib beam guides that define a linear motion path of the jib beam relative to the jib beam support member, said linear motion path extending substantially horizontal when said pedestal member is in said levelled position;
• and
• a jib beam drive connected to said control unit and adapted to cause controlled linear motion of said jib beam relative to the jib beam support member,
• wherein the jib beam carries a sheave arrangement with a front sheave at a front portion of the jib beam from which the hoist cable extends to a sheave of the object suspension device, with a rear sheave remote from said front sheave, and with a first guide sheave arranged such that said hoist cable extends from a sheave of the object suspension device via the first guide sheave to the jib beam support member and is connected thereto with a terminal end,
• wherein the jib beam support member carries a second guide sheave from which said hoist cable extends to the rear sheave on the jib beam,
• wherein the first and second guide sheaves are arranged so that the length of hoist cable between the second guide sheave on the jib beam support member and the terminal end is substantially constant independent of the linear position of the jib beam relative to the jib beam support member, and
• wherein the control unit is configured to provide a wave-induced motion compensation mode wherein the slew drive of the jib beam support member and the jib beam drive of the compensation device are operated to maintain a predetermined X-Y location of the object suspension device.

A wave-induced motion compensating crane for use on an offshore vessel, the crane comprising:

• a base structure adapted to be mounted on an offshore vessel;
• a revolving superstructure adapted to revolve about a substantially vertical revolving axis relative to the base structure;
• a boom structure mounted to the superstructure and pivotally connected at a first end thereof to pivot about a substantially horizontal boom pivot axis relative to the superstructure;
• a motion compensation device mounted to a tip end portion of the boom structure;
• a hoist winch, a hoist cable and an object suspension device suspended from said hoist cable, wherein the hoist winch is mounted on the revolving superstructure or on the boom structure, and wherein the hoist cable extends from the hoist winch to the tip end portion of the boom structure and then along the motion compensation device to the object suspension device;
• a heave compensation device that is configured to act on the hoist cable, wherein the heave compensation device is integrated in the hoist winch and/or arranged to act on the hoist cable intermediate the hoist winch and the tip end portion of the boom structure;
• and
• a control unit,
• wherein the motion compensation device comprises:
• a pedestal member that is pivotally connected to the tip end portion of the boom structure to pivot about a substantially horizontal pedestal member pivot axis which is parallel to the substantially horizontal boom pivot axis;
• a level setting device that is arranged between the boom structure and the pedestal member and that is adapted to set the pedestal member in a levelled position;
• a jib beam support member that is secured to the pedestal member;
• a linear displaceable jib beam that is supported by said jib beam support member via one or more jib beam guides that define a linear motion path of the jib beam relative to the jib beam support member, said linear motion path extending substantially horizontal when said pedestal member is in said levelled position;
• and
• a jib beam drive connected to said control unit and adapted to cause controlled linear motion of said jib beam relative to the jib beam support member,
• wherein the jib beam carries a sheave arrangement with a front sheave at a front portion of the jib beam from which the hoist cable extends to a sheave of the object suspension device, with a rear sheave remote from said front sheave, and with a first guide sheave arranged such that said hoist cable extends from a sheave of the object suspension device via the first guide sheave to the jib beam support member and is connected thereto with a terminal end,
• wherein the jib beam support member carries a second guide sheave from which said hoist cable extends to the rear sheave on the jib beam,
• wherein the first and second guide sheaves are arranged so that a length of hoist cable between the second guide sheave on the jib beam support member and the terminal end is substantially constant independent of the linear position of the jib beam relative to the jib beam support member,
• wherein the control unit is configured to provide a wave-induced motion compensation mode wherein the jib beam drive of the compensation device is operated to maintain a predetermined location of the object suspension device in a direction parallel to the linear motion path, and
• wherein the heave compensation device is configured to compensate wave-induced Z-motion of the object suspension device.