In a variety of water types, floating platforms and ships are moored by means of mooring systems. Anchors, mooring lines, and connectors are all components of the mooring system. Anchors are connected to floating structures by mooring lines. Floating production systems “Mobilis” and mobile offshore drilling units will be our focus.
Mooreing lines can be made with synthetic fiber rope, wire, and chain or a combination of these materials. Mooring systems are constructed with materials determined by environmental factors, like wind, waves, and currents.
Chains are used for permanent moorings below 100 meters depth, while steel wire rope works best in deep water, above 300 meters, since it is lighter and more elastic than chain. Synthetic rope is the heaviest of all ropes. In ultra-deep-water, it is necessary to use all chains, all chains and wire ropes (conventional mooring lines), all chain and synthetic fiber ropes (greater than 2,000 m), and each combination of chain, wire rope and synthetic fiber rope
Considerations
A mooring system is not complete without anchors. Anchors must be installed by knowing how deep you dig and what the soil properties are. A mooring line is used to anchor an anchor to the seafloor. A vertical anchor can be either drag embedded, suction embedded, or vertically loaded.
Drag embedment anchors (DEA) are the most commonly used anchors in the Gulf of Mexico for mooring floating MODUs. An anchor is dragged across the seafloor until it reaches the required depth. It penetrates the seabed using soil resistance in order to hold the anchor firmly in place. These anchors are usually used when moorings are horizontally installed. Vertical forces are bad for these anchors.
Suction piles are commonly used as foundations and moorings for deepwater development projects all over the world. Tube piles are driven into the seabed using a pump that pumps them into the seabed. During the process of suckout, the piles are driven even deeper into the seabed. In sand, clay, and mud soils, suction piles are insufficient because of water seeping through gravel during installation and making suction difficult. In place, the pile is firmly anchored into the soil due to the friction between it and the soil. It is possible to apply vertical or horizontal force to the pile.
It can be said that anchors used for vertical loads are very similar to anchors used for drags in the sense that they are similarly installed. Nevertheless, the anchor can support both horizontal and vertical loads. A taut leg mooring system uses a mooring line that is at an angle to the seabed.
Mooring System
It is possible to classify mooring systems into six types. Systems of positioning are diverse and include catenary, taut leg, semitaut leg, spread, single point, and dynamic.
Shallow water mooring is commonly done with catenary mooring systems. Despite its free-hanging nature, it is named for the way in which its configuration changes based on vessel motion. At the bottom of the ocean, mooring lines lie horizontally; consequently, they must be longer than the depth of the water. The longer the lines, the more weight they can carry. When the water depth increases, the line’s weight decreases. Synthetic rope is used to compensate. Utilizing conventional catenary systems becomes less expensive as the water depth increases.
Polyester rope and tout leg systems, which are pre-tensioned to tautness, are typical with polyester rope. In the case of ropes (suction piles or vertically loaded anchors), when the ropes meet the anchors, they approach at a steep angle (at a 30-45 degree angle on the seabed). A drifting platform is stretched horizontally by wind and current. It then confronts this opposing force. A semi-taut system is composed of taut lines integrated with catenary lines. Deep-water applications are best suited to such systems.
Anchors on the seafloor are connected via mooring lines to the bow or stern of a ship via a spread-mooring system. The vessel is on a fixed heading due to marine conditions and weather conditions. In order to continue on its fixed course, the anchors are arranged symmetrically. An interconnected spread of moorings prevents a boat from weathervanging, which means that it moves in response to wind, waves, and currents. In any depth of water and on any vessel, an evenly spread pattern or a group of equally spread spread moorings can be used.
A mooring mobilis system connects all lines to one point. Whenever weathervane tankers are connected, the manifolds underwater can rotate 360 degrees. Among the components of the system are buoys, moorings, anchors, as well as tools for transferring products.
The dynamic positioning process does not usemooring lines. Propellers and thrusters are controlled by an electronic system rather than a crew. A DP system provides additional redundancy on top of other mooring systems.
