A first permissible operating range of the self-elevating vessel is determined based on a first structural analysis of the self-elevating vessel under a first set of conditions. A structural utilization ratio of the self-elevating vessel is determined based on a second structural analysis of the self-elevating vessel under first and second sets of conditions. Safety of lowering the self-elevating vessel from an elevated state to a first hull draft level is determined when the structural utilization ratio is less than a predetermined value. Safety of lowering the self-elevating vessel from the first hull draft level to a second hull draft level is indicated when positional displacement data obtained while the vessel is at the first hull draft level indicates that the positional displacement of the self-elevating vessel while at the first hull draft level is within the first permissible operating range.

A jack-up platform is described having a horizontal working deck that may be jacked up out of the water by moving its legs to a position wherein they take support on an underwater bottom. The jack-up platform further comprises a mooring system for mooring a floating vessel at a mooring side of the jack-up platform. The mooring system comprises an elongated support means for supporting a hull part of the floating vessel, and guiding means connected to the hull of the jack-up platform at the mooring side. The guiding means are able to rigidly hold the elongated support means in a support position, in which the elongated support means is within reach of the hull part of the floating vessel to be supported when the hull is jacked out of the water and the jack-up platform rests on its legs. A method for mooring a floating vessel using the jack-up platform is also described.

A control system retracts lifting devices to a stored reset height during a reset operation to raise support feet off of a base surface. The control device raises a load to a stored moving height above the base surface during a moving operation. The control system automatically repeats the reset and moving operations using the stored reset and stored moving heights. The control device may receive an adjustment signal identifying anew height of the support feet or load bearing frame above the base surface and uses the new height during subsequent reset or moving operations. The control device may default to a minimum reset height or a minimum moving height when the new height would cause the support feet or load bearing frame to drag on the base surface.

A control system retracts lifting devices to a stored reset height during a reset operation to raise support feet off of a base surface. The control device raises a load to a stored moving height above the base surface during a moving operation. The control system automatically repeats the reset and moving operations using the stored reset and stored moving heights. The control device may receive an adjustment signal identifying anew height of the support feet or load bearing frame above the base surface and uses the new height during subsequent reset or moving operations. The control device may default to a minimum reset height or a minimum moving height when the new height would cause the support feet or load bearing frame to drag on the base surface.

A truss-like hydraulic lifting apparatus with plugs including a pile reinforcing frame, a truss structure extending through and mounted within the pile reinforcing frame and a first number of uniformly disposed support legs, each having a support leg inserting hole. A first number of power source devices each has a plug corresponding to the support leg inserting hole. A detachable mechanism is provided for detachably fixing each of the power source devices to the pile reinforcing frame. The detachable mechanism includes a base plate laterally fixed relative to the pile reinforcing frame and having an opening through which the support leg vertically passes and forms a protective cap above the power source device. The lateral dimension of the protective cap is larger than the lateral dimension of the power source device.

A marine vessel and a method of operation of such a marine vessel include a crane with a boom including a main boom section and a jib section and a variable length stay mechanism. The lattice boom is movable from a hoisting position into a parking position by a routine including operating the variable length stay mechanism allowing the jib section to fold towards the main boom section. The crane is provided with a fixation device adapted to establish fixation of the jib section relative to the main boom section in a folded position. A boom rest is mounted on the hull. The routine further includes operating the luffing assembly to position the jib member of the folded jib section, fixated to the main boom section, in the parking position onto the boom rest.

A marine vessel and a method of operation of such a marine vessel include a crane with a boom including a main boom section and a jib section and a variable length stay mechanism. The lattice boom is movable from a hoisting position into a parking position by a routine including operating the variable length stay mechanism allowing the jib section to fold towards the main boom section. The crane is provided with a fixation device adapted to establish fixation of the jib section relative to the main boom section in a folded position. A boom rest is mounted on the hull. The routine further includes operating the luffing assembly to position the jib member of the folded jib section, fixated to the main boom section, in the parking position onto the boom rest.

A method of elevating the deck area of a marine platform (e.g., oil and gas well drilling or production platform) utilizes a specially configured sleeve support to support the platform legs so that they can be cut. Once cut, rams or jacks elevate the platform above the cuts. The sleeve support is then connected (e.g., welded) to the platform leg and becomes part of the structural support for the platform. In one embodiment, two sleeves are employed. In another embodiment, the jacks or rams elevate in two stages including a first stage wherein one sleeve elevates and the other sleeve does not elevate and a second stage wherein both sleeves elevate together.

A method of elevating the deck area of a marine platform (e.g., oil and gas well drilling or production platform) utilizes a specially configured sleeve support to support the platform legs so that they can be cut. Once cut, rams or jacks elevate the platform above the cuts. The sleeve support is then connected (e.g., welded) to the platform leg and becomes part of the structural support for the platform. In one embodiment, two sleeves are employed. In another embodiment, the jacks or rams elevate in two stages including a first stage wherein one sleeve elevates and the other sleeve does not elevate and a second stage wherein both sleeves elevate together.

The offshore jack-up has a hull and a plurality of moveable legs engageable with the seafloor. The offshore jack-up is arranged to move the legs with respect to the hull to position the hull out of the water. The method comprises moving at least a portion of a vessel underneath the hull of the offshore jack-up or within a cut-out of the hull when the hull is positioned out of the water and the legs engage the seafloor. A stabilizing mechanism mounted on the jack-up is engaged against the vessel. The stabilizing mechanism is pushed down on the vessel to increase the buoyant force acting on the vessel.