Mooring line

mooring line {MOORING LINE}

The present invention relates to a mooring vessel comprising synthetic fibers, said mooring vessel having a length of at least 800 meters and suitable for holding water floating systems in place.

Said mooring boats comprising synthetic fibers and having a length of more than 800 meters offer the advantages of high strength and high rigidity and are therefore already being used for marine heavy equipment purposes, for example to hold water floating systems in place. Further important advantages to be mentioned are reduced weight and corrosion-free properties.

A problem with current mooring vessels containing synthetic fibers and having a length of 800 meters or more is that the size and tonnage of water-floating systems continues to increase. Accordingly, the requirements for the design, size and mechanical properties of modern mooring vessels are becoming more and more precise. As the distance between fixed berths and water-floating systems increases, it becomes more difficult to hold large water-floating systems in place. External factors such as wind, surface waves, or water currents have a strong influence on the movement of water-floating systems. In many cases, for example in systems used for oil or natural gas production, it is very important to fix the flotation system correctly in place.

Materials commonly used when producing the synthetic fibers constituting the mooring line include polyester, nylon, polypropylene, aramid, polyethylene, and the like, each of which has advantages and disadvantages.

An example of a known mooring vessel used to anchor an oil rig or the like in place is a mooring vessel comprising polyester fibers, which provides good strength and stiffness and low creep. However, a mooring line comprising polyester fibers and having a length of 800 meters or more has a diameter of 250 mm or more, so it is very heavy and very difficult to handle. Another disadvantage is that, due to the relatively low stiffness of the polyester fibers, the water-floating system may be more likely to deviate from its original position when exposed to external factors such as wind currents or water waves.

800 Mooring lines with a length of more than a meter are also made of steel wire, but besides being very heavy, they have the disadvantage that they cannot be used in places where the water depth exceeds 2,000 meters. If the water depth exceeds 2,000 meters, the steel wire mooring line is at great risk of breaking because of its increased length, unable to withstand its own load. Moreover, these steel wire moors often require extra buoyancy, and in the event of a failure under load, heavy steel wire moors increase the risk of damaging the hardware they may come into contact with.

Polyethylene fibers of high stiffness are also used to manufacture the mooring line. A mooring line comprising polyethylene fibers has, for example, a higher strength than a mooring line comprising polyester fibers of the same diameter. It also has the advantage of being lightweight and having good handling properties. A disadvantage of mooring lines having a length of 800 meters or more and having a use for holding water floating systems in place is the higher rigidity of the polyethylene fibers and the defects of the mooring lines due to up and down motion of the water floating system due to water currents or water waves. high tension and high peak loads that can lead to

Due to the disadvantages listed above, the known mooring vessels with a length of 800 meters or more are less suitable for permanent mooring of water floating systems, if the distance between the fixed anchorage point and the water floating system is too long. .

It is an object of the present invention to provide a mooring vessel having a length of at least 800 meters, which is suitable for holding water floating systems in place, wherein the mooring vessel comprises synthetic fibers and has an improved balance in terms of size and mechanical properties. .

Surprisingly, this object is achieved by the present invention, wherein the mooring vessel comprises at least one first and second module, said at least one first and second module having synthetic fibers of different composition.

Surprisingly, the mooring vessel according to the present invention (hereafter for convenience, said mooring vessel will be referred to as a modular mooring vessel) can more accurately hold the water floating system in its original position. A further advantage is that the modular mooring line has different mechanical properties as it contains modules of different composition, thus better dampening the high peak loads occurring on the modular mooring line due to waves, wind or water currents. The mooring's modular design further facilitates the tunability of the mooring for specific applications requiring a precise balance between water-floating systems and high peak loads. A further advantage is that, due to its special modular design, the tension of the modular mooring vessel is reduced. A further advantage of the modular mooring line is, as will become apparent from the present specification, achieved by adjusting the composition of the modules to obtain the right balance of strength and size of the modular mooring line.

A line is a rope, a cord, a twine, a cable, a string, and similar structures including fibers or including fibers and staple fibers. It is understood. A mooring line is herein understood to be a line used to anchor a water floating system at a fixed anchor point.

A module is a segment of a mooring line having a characteristic composition of fibers, wherein the composition of the fibers is understood to be different from the composition of the fibers characteristic of the module(s) and the segment(s) adjacent to the segment or module.

Preferably, the module is provided with connectors at both ends, and the connector is used when connecting one end of a module to one end of another module to form the mooring line. Moreover, the connection may also be used when connecting the modular mooring line with a fixed berth and a water floating system. The connections may be, for example, different types of shackles, loops, or the like. For example, one end of one module and one end of another module are connected using the above connecting portion to obtain two modules in a series form. For example, when one end of one module and one end of two or more other modules are connected, a module in the form of a bundle can be obtained. Depending on the particular application, one skilled in the art can select a suitable combination to provide a modular mooring vessel that provides an improved balance in terms of size and mechanical properties.

A water-floating system is understood as any system that is moored to a berth by a mooring vessel. The water-floating system may be a system that floats above the surface of the water or an underwater-float system at a specific depth of water, suitable examples being floating production storage and unloading vessels, columnar buoys, semi-submersible systems or other hydrocarbon storage and / or processing systems and the like.

In the modular mooring boat according to the invention, the synthetic fibers constituting the module are fibers obtained from all kinds of materials suitable for producing synthetic fibers, for example propylene, polyester, polypropylene or copolymers of polyester, nylon, , aramid, polyolefin, and the like, and combinations thereof.

The synthetic fibers constituting the module are obtained by twisting synthetic filaments together. Preferably, the synthetic fiber consists of at least 100 synthetic filaments, more preferably at least 200 synthetic filaments, even more preferably at least 300 synthetic filaments. Synthetic filaments may have widely varying linear densities or titres, preferably the titre of the synthetic filaments is from 0.2 to 50 dtex per fiber, more preferably from 0.3 to 20 dtex and most preferably from 0.4 to 10 dtex. am.

Also, the synthetic fibers are preferably twisted to form a yarn, which yarn is preferably made of at least 10 synthetic fibers, more preferably at least 20 synthetic fibers, even more preferably at least 50 synthetic fibers. is composed The yarns are preferably further twisted to form strands, each strand preferably consisting of at least 10 yarns, more preferably at least 20 yarns, most preferably at least 50 yarns. A module may be obtained by laying, plaiting or braiding of the strands, or a combination thereof. A person skilled in the art can select the desired final structure and size-related structure type for the module, either based on his own knowledge or with the aid of some calculations or experimentation. Suitable examples include hollow braided or laid modules, solid braided or solid laid modules, twisted braided modules, plain braided or laid laid modules, and the like. The module structure is not limited to the module configuration mentioned above, and any other module configuration can be used successfully in accordance with the present invention.

The fibers comprising the module and/or the module are further coated with a lubricating coating applied thereon, thereby reducing wear and internal friction to prevent galling and fretting, thereby extending the life of the module and removing foreign matter. Inflow into the module can be prevented. The module may further contain a particle filter used as a barrier to prevent the entry of abrasive particles and at the same time allow the environment, ie air or water, to circulate inside the module.

Examples of preferred embodiments of the modular mooring vessel according to the invention are presented below, which realize the advantages obtained by using the module of the invention. It is to be understood that the preferred embodiments are not limited to those set forth below, and those skilled in the art will readily ascertain further embodiments and advantages according to the invention which will become apparent from the following detailed description in conjunction with the claims. .

In a preferred embodiment, the modular mooring vessel according to the invention is suitable for use for securing in place a water floating system, wherein said module has a length of at least 100 meters, more preferably at least 200 meters, even more preferably is at least 300 meters, even more preferably at least 500 meters and most preferably at least 700 meters.

Preferably, all modules of the modular mooring boat according to the invention comprise synthetic fibers, more preferably all modules consist of synthetic fibres.

In a more preferred embodiment, the modular mooring boat according to the invention comprises at least first and second modules, said first module comprising polyester fibers.

In another more preferred embodiment, the modular mooring vessel according to the invention comprises at least first and second modules, said second module comprising high-performance polyolefin fibers as second fibers.

In another more preferred embodiment, the modular mooring boat according to the invention comprises at least first and second modules, said first module comprising at least 51% by weight of first fibers, said second module comprising at least 51% by weight of said second module The above high-performance polyolefin fiber is included as the second fiber.

The first fibers in the first module may be fibers obtained from all kinds of materials suitable for fiber production, such as propylene, polyester, polypropylene or copolymers of polyester, nylon, etc. and combinations thereof. Preferably, the first module comprises at least 60% by weight of first fibers, more preferably at least 75% by weight of first fibers, and most preferably at least 95% by weight of first fibers. Next to the first fiber, the first module may also include high performance polyolefin fibers.

The second fiber in the second module according to the invention is a high-performance polyolefin fiber. Preferably, the second module comprises as second fibers at least 60% by weight high performance polyolefin fibers, more preferably at least 75% by weight high performance polyolefin fibers, and most preferably at least 95% by weight high performance polyolefin fibers. After high performance polyolefin fibers, the second module may also include other types of fibers.

Preferably, the free end of the second module comprising high performance polyolefin fibers is connected to an anchor which will provide an anchoring point at the seabed. Accordingly, the free end of the module comprising the first fiber is preferably provided with a connection suitable for anchoring the modular mooring vessel to the water-floating system. The connection of the free end of the modular mooring vessel according to the invention to the water-floating system and the anchor which provides the anchorage on the seabed is a steel wire rope or steel chain having a predetermined length, preferably not more than 100 meters. can be achieved using Once installed, the steel ropes or chains are used with the modular mooring vessel and water floating system according to the present invention to prevent actual damage that can be induced to the module by friction, mishandling, etc. used to prevent direct contact with

Another preferred embodiment is the modular mooring boat according to the invention comprising at least first and second modules, said first module comprising at least 51% by weight polyester fibers and said second module comprising at least 51% by weight of polyester fibers A high performance polyolefin fiber is included as the second fiber.

Suitable polyolefins that can be used to make the high performance polyolefin fibers include, for example, polyethylene homopolymers, polypropylene homopolymers, polyethylene copolymers and polypropylene copolymers, and the like, and combinations thereof. The most preferred high-performance polyolefin fibers are preferably ultra-high molecular weight polyethylene (UHMWPE) fibers.

This embodiment of the modular mooring vessel according to the present invention combines the durability and low creep specific to polyester fiber with the light weight and high strength specific to UHMWPE polyethylene fiber, greatly reducing the total weight and volume of the modular mooring vessel. and improve handling properties. It has been found that the weight and volume of the modular mooring vessel according to the present invention is significantly reduced when compared to a conventional polyester mooring vessel. A further advantage is that the breaking length in water of the modular mooring vessel is significantly increased. Because of their light weight, the modular mooring vessel has improved handling and increased safety for personnel involved in the installation and maintenance of the modular mooring vessel, as well as the risk of damage to hardware that may come into contact with the modular mooring vessel. This was reduced. In addition, the modular mooring line according to the present invention exhibits enhanced tension, torsional and flexural fatigue.

The presence of a module comprising polyester fibers having a lower stiffness than UHMWPE fibers has the advantage that the effect of heave properties on rigs and the like is efficiently detuned. Therefore, the presence of a module comprising polyester fibers provides good cushioning to the modular mooring line, helping to reduce the peak load generated by the modular line.

In addition, the modular mooring line provides an excellent combination of stiffness, elongation at break and energy absorption. A further advantage is that the presence of modules comprising UHMWPE fibers helps to more accurately hold the water-floating system in place and also after prolonged periods of use.

Therefore, when said modular mooring line is used in accordance with the invention, good anchorage in the modular mooring line, good controllability of the movement of the water floating system, and minimization of the total tension are achieved. The modular mooring line is particularly suitable for use in holding water floating systems in place in areas with frequent storms or where water currents are extremely strong. An example of such a location is the Gulf of Mexico, where hurricanes, strong winds and strong currents occur constantly, so good anchorage of drilling vessels and the like is very important.

Preferred polyesters that can be used to make the polyester fibers are linear terephthalate polyesters, i.e. glycols containing from 2 to 20 carbon atoms and preferably at least 75%, more preferably at least 90% terephthalic acid. It is a polyester of residual dicarboxylic acid component containing The residual dicarboxylic acid may be any suitable carboxylic acid, such as sebacic acid, adipic acid, isophthalic acid, sulfonyl-4,4'-dibenzoic acid, 2,8-dibenzofuran-dicarboxylic acid or 2,6-naphthalene dicarboxylic acid. can be The glycols may contain more than two carbon atoms in the chain, such as diethylene glycol butylene glycol, decamethylene glycol and bis-(1,4-hydroxymethyl)cyclohexane. There is this. The most preferred linear terephthalate polyester is poly(ethylene terephthalate).

Preferably the polyester fibers have a tensile strength of at least 0.6 GPa, more preferably at least 0.7 GPa, and most preferably at least 0.8 GPa. The elongation at break of the polyester fibers is preferably 3% or more, more preferably 10% or more and most preferably 16% or more. The polyester fiber preferably has a titer of 50 dtex or less, more preferably 110 dtex or less, and most preferably 220 dtex or less.

The UHMWPE fibers are preferably produced according to a gel spinning process. Gel spinning of UHMWPE is known to the person skilled in the art and is described in EP 0205960 A, EP 0213208 A1, US 4413110, GB 2042414 A, EP 0200547 B1, EP 0472114 B1, WO 01/73173 A1 and Advanced Fiber Spinning Technology, Ed. T. Nakajima, Woodhead Publ. Ltd (1994), ISBN 1-855-73182-7, and references cited therein. Gel spinning comprises spinning one or more fibers from a solution of ultra-high molecular weight polyethylene in a spinning solvent; cooling the obtained fibers to form gel fibers; at least partially removing spinning solvent from the gel fibers; drawing the fiber in one or more drawing steps before, during or after removal of the spinning solvent. Suitable spinning solvents include, for example, paraffin, mineral oil, kerosene or decalin. The spinning solvent may be removed by evaporation, extraction, or a combination of evaporation and extraction routes. The cross-sectional shape of the fiber can be selected by selection of the spinning aperture shape.

In the context of the present invention, ultra-high molar mass polyethylene (UHMWPE) is understood to be a polyethylene having an intrinsic viscosity (IV) of at least 5 dl/g. IV is PTC using decalin as solvent for UHMWPE at a temperature of 135° C., dissolution time of 16 hours, antioxidant DBPC in an amount of 2 g/L solution, and extrapolating the viscosities at different concentrations to zero concentration. -179 (Hercules, Inc., revised April 29, 1982) was measured according to the method. UHMWPE having an IV of preferably from 8 to 40 dl/g, more preferably from 10 to 30 dl/g, even more preferably from 12 to 28 dl/g and most preferably from 15 to 25 dl/g is particularly Suitable.

Preferably, the UHMWPE is a linear polyethylene having less than one branched and branched chain per 100 carbon atoms, preferably less than one branched per 300 carbon atoms, the branches usually containing at least 10 carbon atoms. . The linear polyethylene may further contain up to 5 mole % of one or more comonomers, such as alkenes such as propylene, butene, pentene, 4-methylpentene or octene.

In a preferred embodiment, the UHMWPE contains a certain amount of relatively small groups such as C1-C4 alkyl groups as side chains. It has been found that fibers from UHMWPE containing certain of these groups show reduced creep. If the side chains are too long, or if the amount of side chains is too large, their presence will adversely affect the processing and draw properties in the processing of UHMWPE fibers in particular. For this reason, UHMWPE preferably contains a methyl or ethyl group or a combination thereof as a side chain, and more preferably contains only a methyl group as a side chain. The amount of side chains is preferably at least 0.3 per 1000 carbon atoms, more preferably at least 0.5 per 1000 carbon atoms and most preferably at least 1 per 1000 carbon atoms. The amount of side chains is preferably no more than 20 per 1000 carbon atoms, more preferably no more than 10 per 1000 carbon atoms.

UHMWPE may be of a single polymer grade, but may also be a mixture of two or more different UHMWPE grades. UHMWPE grades are understood to be UHMWPEs having a specific IV or molar mass distribution and having a specific number of side chains with a specific configuration.

The UHMWPE polymer may further contain customary amounts, generally less than 5% by weight, of customary additives such as antioxidants, heat stabilizers, colorants, nucleating agents, flow promoters, catalyst residues, and the like, and also other polymers, preferably preferably contain polyolefin-based polymers such as other polyethylenes, polypropylenes or copolymers thereof (including rubbery copolymers such as EPDM, EPR, etc.).

UHMWPE fibers can have a wide range of filament linear densities or titers. Preferably the titer of the UHMWPE filaments is from 0.2 to 20 dtex per fiber, more preferably from 0.3 to 10 dtex and most preferably from 0.4 to 5 dtex.

Preferably, the tensile strength of the UHMWPE fibers is at least 1.5 GPa, more preferably at least 2.0 GPa, and most preferably at least 3.0 GPa. Tensile strength was measured on multi-fibers as described in ASTM D885M using a fiber nominal gauge length of 500 mm, crosshead speed of 50%/min and an Instron 2714 clamp, type Fiber Grip D5618C. do.

Preferably the stiffness of the UHMWPE fibers is at least 35 GPa, more preferably at least 50 GPa, even more preferably at least 70 GPa, even more preferably at least 100 GPa, and most preferably at least 140 GPa. In a preferred embodiment, the stiffness of the UHMWPE fibers is between 110 GPa and 135 GPa.

The length of the first module comprising polyester fibers is preferably less than or equal to 2000 meters, more preferably less than or equal to 1500 meters, even more preferably less than or equal to 1000 meters, even more preferably less than or equal to 500 meters, even more preferably preferably 350 meters or less, most preferably 200 meters or less. The ratio between the length of the module comprising polyester fibers and the length of the module comprising UHMWPE fibers is preferably 90% or less, more preferably 60% or less and most preferably 30% or less.

The advantage of adjusting the above ratio is that, depending on where the modular mooring line is used, the module comprising UHMWPE fibers is located at a water depth where the water temperature is preferably less than 15°. This ensures using modules comprising the UHMWPE at water depths where the water temperature helps preserve the mechanical properties of the UHMWPE fibers.