Abstract: A tendon installation for anchoring a semisubmersible platform to a sea bed foundation, wherein said tendons are tensioned by the updrift of the platform. The tendons are prefabricated in dimensions adapted to the depth of the sea bed foundation, expected tension load and in order to be substantially weightless in water. The tendons are connected in groups at each of their ends at a distance corresponding to the distance between anchoring points in the foundation and the platform respectively. The groups of tendons are towed out to the anchoring site and they are positioned vertically above the foundation. The tendons are fastened to the anchoring points in the foundation. The platform is positioned above the groups of tendons and connected to these via wire ropes. The platform is ballasted down onto the tendons under guidance by said wire ropes. The upper ends of the tendons are mounted internally in the legs of the platform.

Abstract: A tether system for a semisubmersible work platform which may be based on deep water, comprising a number of pontoon elements mounted in a frame configuration, upright columns and a work deck for exploitation of oil or gas fields below the sea bottom. The system comprises a sea bed anchor template, which is provided with receptacle means for tendons, running up to connectors at the work platform. The receptacle means in the sea bed anchor template are located along a circular track on which a carrier can move. The carrier has sheave means for one or more handling line for a tendon which is provided with a running collar. The connectors for the upper ends of said tendons are located at the outside of the columns.

Abstract: A method for converting an existing semi-submersible drilling- or accommodation rig into a floating production plant having apparatus for extracting and processing oil and/or gas, or other heavy and bulky deck load. These vessels comprise at least two submerged pontoon bodies, a work deck raised to a secure level above the surface of water having personnel accommodation areas and upright support columns between the bodies and the work deck. A module is prefabricated which contains the main part of the processing apparatus. The vessel is provided with a steel structure to carry the module near the level of the work deck. Also, the vessel is provided with a displacement increasing device, substantially corresponding to the dead weight of the module and the steel structure. Further, the water line area of the vessel is increased until the necessary deck load capacity and stability is achieved.

Abstract: A node intersection between circular columns and pontoon members at a tendon-moored semisubmersible offshore platform. The pontoon members have a box shape, defined by vertical side walls, a horizontal deck and a horizontal bottom skin, joined together into a foursided frame, via the columns. The node intersection comprises vertical bulkheads within the lower ends of the columns, forming internally intersecting continuations of the vertical sidewalls.

Abstract: An ice breaker vessel and a method for increasing maneuverability and protecting the propellers against broken ice when going backwards. The ice breaker has two stern propellers and a steering rudder aligned with each propeller shaft. Each of the rudders is individually rotatably mounted on a vertical rudder stock adjacent half the cord of the rubber blade profile length, and connected to a rudder gear, so that they e.g. may converge or diverge in the direction backwards, in abutment with end stops positioned on the stern of the ice breaker vessel, when the rudders are in their respective end positions. The method comprises turning the steering rudders in opposite directions until they cooperate and for backwards converging rudder surfaces.

Abstract: An ice-breaking vessel having a spoon-shaped bow portion and an obliquely downwardly/rearwardly extending reamer at each longitudinal side is provided with second reamers located above the water line, above the rear portion of the adjacent first reamer and extending further outward than the same. A plow-shaped extension projects downwards from the plane bottom of the vessel, and has a breadth less than the breadth thereof. The rearmost part of the deck of the aft portion of the vessel has a reduced breath, so two corners are formed at each side of the deck. The bilges at the bottom plating extend to the forward of these corners, while the bilges at the plow-formed extension extend to the rearward corners.

Abstract: A tendon installation for anchoring a semisubmersible platform to a sea bed foundation, wherein said tendons are tensioned by the updrift of the platform. The tendons are prefabricated in dimensions adpated to the depth of the sea bed foundation, expected tension load and in order to be substantially weightless in water. The tendons are connected in groups at each of their ends at a distance corresponding to the distance between anchoring points in the foundation and the platform respectively. The groups of tendons are towed out to the anchoring site and they are positioned vertically above the foundation. The tendons are fastened to the anchoring points in the foundation. The platform is positioned above the groups of tendons and connected to these via wire ropes. The platform is ballasted down onto the tendons under guidance by said wire ropes. The upper ends of the tendons are mounted internally in the legs of the platform.

Abstract: A ballast arrangement includes a number of tanks and a pump connected to a sea-chest and having a discharge conduit extending to a level above the top-most tank. A distribution conduit extends to the various tanks and an overflow pipe is connected to the discharge conduit and reaches to a further level, above the first mentioned level, where also an evacuation pipe is connected. The further level will determine the static pressure which may act in any of the associated tanks. The tanks may be connected to the suction side of the pump through by-pass conduits, and a two-way valve is designed so the pump can communicate only with either the sea-chest or with the by-pass conduits.

Abstract: In order to facilitate temporary storing of oil in an underwater receptacle, for instance the pontoon of a semi-submersible vessel, the receptacle is subdivided by bulkheads into a series of tanks. A first tank is connected to a production unit by way of a conduit, or by way of a branch pipe to a delivery conduit. The tank located remotely with respect to the conduit communicates with the surrounding sea by an opening. The bulkheads are provided with upper and lower openings, respectively, and a screened passage extends between these openings. When oil is supplied to the first tank static or pump pressure will expel water through opening, and oil will fill the tanks in due order in the direction away from the first tank. When oil is withdrawn, water from the surrounding sea will flow in through opening and further on through the tanks towards the first tank.

Abstract: A watertight compartment at a floating production plant handing crude oil and/or gas has at least one remotely releasable two-part connecting piece for a riser conduit between the sea floor and the plant. The compartment includes a sealing collar mounted in the bottom plating of the plant. The collar provides a sealing with respect to an upper half of the connection piece in relation to the compartment, as well as with a lower half of the connection piece, which is surrounded by water.

Abstract: A hydrostatic coupling device for rapidly releasing a first object immersed in water from another object resting on the sea bed. The device comprises a seal mounted in a groove in the first object, which in use will be pressed against the other object. The groove is formed as a closed loop delimiting a space at the surface of the first object facing the other object. The seal is formed as a membrane mounted along its sides and dividing the groove into an outer part, open to the ambient water, and an inner part, which via a pipe can be connected to a reservoir above the water surface. This reservoir maintains a liquid column pressure in the inner part, being a certain amount higher than the ambient water pressure. A pumping device removes water from the space delimited by the seal and both objects.

Abstract: In order to reduce the risk of an offshore vessel capsizing in the event of a collision resulting in damage to its columns, a strengthening member is arranged in front of at least one of the columns, between the work platform of the vessel and the supporting hull. The strengthening member comprises a watertight box structure rigidly connected to the platform, and a tubular, also displacing part, extending between the box structure and the hull. The box structure has considerable volume and is situated so high that it will not be damaged in the event of a collision.

Abstract: In an arrangement including remotely releasable couplings for riser conduits between the sea floor and a floating plant processing crude oil and/or gas, the couplings are located in at least one chamber below the water line of the plant. This chamber is closed towards the atmosphere and provided with at least one downwardly directed opening communicating with the surrounding water. Structure is provided for governing the air pressure in the chamber, which is accessible through an air lock.

Abstract: In order to improve the working conditions for the staff on drilling rigs, the work area for handling of pipes and tubes is arranged on a main deck covered by a drill deck, which has openings closable by hatch cover panels. The derrick is enclosed in a cover, from which tunnels extend out over the drill deck and comprises lifting means for handling of pipes and tubes between the decks. The tunnels are connected to the cover of the derrick by way of raised enclosures permitting the swinging of pipes from a horizontal position in the tunnel to a vertical position in the derrick, and vice versa. There is a door, at least at one of the enclosures permitting handling of especially long objects, and basically the handling of pipes and tubes can be performed within areas fully protected from the weather.

Abstract: The mounting of a thruster propeller unit in the bottom plating of a vessel is facilitated by the use of lifting lines, operable from within the vessel. Each line is made to pass a lock chamber adjacent to an opening in the bottom plating, outside the opening where the thruster propeller is to be fitted. The lock chamber includes a first, rigid tubular member, which is formed as the housing for a slide valve, as well as a second tubular member, which is resilient at least in the transverse direction. The two tubular members define a passage being substantially wider than the diameter of the lifting line. The second tubular member is at its top provided with a sealing sleeve which fits around the line. The locking chamber is connected to a source of compressed air, which makes it possible to maintain a pressure within the chamber balancing the pressure of the surrounding water.

Abstract: The location of azimuth thruster propellers at the parallel hulls of semisubmersible offshore vessels, is arranged so the water jet from a propeller at one hull, which is occasionally directed towards the adjacent hull will pass mainly below last-mentioned hull. When thruster propellers are arranged in pairs the bottoms of the hulls will preferably be inclined upwardly/outwardly within the portion around a thruster propeller located outside of a longitudinal middle plane through the hull. In order to facilitate the docking of the vessel, the bottom plating in the fore and aft bodies of the hulls, where the thruster propellers are mounted, should be raised sufficient to prevent the propellers projecting below the base lines of the hulls.

Abstract: In order to stay the columns in an offshore vessel of the type having two parallel pontoons and an operating platform carried thereby, also with respect to forces tending to displace the pontoons longitudinally in relation to each other, the columns located in the same transverse plane are interconnected by two transverse braces arranged in cruciform close to each other, but lacking direct connection.

Abstract: A semi-submersible offshore platform comprises an operating deck carried by four cylindrical columns supported by a pontoon structure comprising four-sided boxes formed into a square ring. Each pontoon box is subdivided into two compartments by a longitudinal centerline bulkhead, the compartments being further subdivided into tanks by transverse bulkheads. Tanks outside the centerline bulkheads are used for ballast water, and tanks inside the centerline bulkheads are used to store the oil produced.

Abstract: In order to make possible a "self-docking" of a floating dock, the dock is divided into a middle pontoon and two end pontoons, which are interconnectable in alternative positions in the vertical direction, so either the middle pontoon, or the end pontoons may be lifted out of the water. The pontoons are held together by bolts, which are accessible from cofferdam-like spaces, formed when two pontoons are fitted together, and which may be maintained watertight. Male and female coupling members are furthermore provided to secure the pontoons in their two operative positions. During a disconnecting and connecting operation the pontoons are guided by rigid link arms, chains or the like.

Abstract: In order to simplify the construction and to reduce the resistance to flow, and to provide a high amount of inertia in relation to all essential axes, an offshore vessel comprises two parallel under-water bodies, four columns mounted symmetrically thereupon, and a multi-deck box-like structure interconnecting the upper ends of the columns. This structure will increase the strength of the vessel so only one horizontal, transverse stay is required between each pair of columns. Below each column there is a 360.degree.-turnable shrouded propeller, which together can hold the vessel stationary, with a vertical line of symmetry in a desired position, for instance above a borehole. The box structure is outwardly completely closed at the bottom and sideplating, and will, in case of need, retain the vessel floating.