| 摘要 |
A boat lifting crane includes an annular ring beam mounted on the barge deck of a jack-up rig about one of the vertical openings of the rig that receives one of the legs and its elevating units. The ring provides spacing away from the leg, its opening and its elevating unit so that the ring derives all of its structural integrity from the barge or hull of the jack-up unit. The ring provides upper and lower bearing surface portions. A crane gantry extends about a selected one of the legs and its adjacent elevating units of the jack-up rig, the gantry having front and rear portions. A boom pivotally mounts to the front portion of the gantry. Roller bearings and/or other friction reduction devices on the front portion of the gantry transfer load to the ring upper surface. Hook rollers and/or other friction reduction devices on the rear portion of the gantry transfer uplift load to the ring at the ring lower surface. The ring and the gantry are sized and shaped so that the gantry can rotate fully about the leg without interfering with the operation of the leg nor with the structural integrity of the jack-up units used to elevate the leg. |
