KR101419552B1 - Mooring line - Google Patents

Abstract

The present invention relates to a mooring line having a length of at least 800 meters and suitable for anchoring a floating system in place and comprising synthetic fibers, wherein the mooring line comprises at least a first and a second module, The modules have different compositions. The mooring line according to the invention is suitable for use in fixing the floating system in place. The water-flooded system may be a floating system on the water surface or an underwater floating system at a particular depth of water, suitable examples being float production storage and unloading vessels, column buoys, anti-submersible systems or other hydrocarbon storage and / And / or a processing system.

Description

Mooring Line {MOORING LINE}

The present invention relates to a mooring line comprising synthetic fibers, said mooring line having a length of at least 800 meters and being suitable for fixing a water floating system in place.

The mooring line containing synthetic fibers and having a length of more than 800 meters provides advantages of high strength and high stiffness and has already been used for marine heavy equipment applications, for example, to fix a floating system in place. A further significant advantage to be mentioned is reduced weight and corrosion-free properties.

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

Examples of materials generally used for producing the synthetic fiber composing the mooring line include polyester, nylon, polypropylene, aramid, and polyethylene, and these have advantages and disadvantages.

An example of a known mooring line used when fixing crude oil lures or the like in place is a mooring line that includes polyester fibers and provides good strength and stiffness and low creep. However, a mooring line containing polyester fibers and having a length of more than 800 meters has a diameter of 250 mm or more, which 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 can escape more from its original position when exposed to extraneous factors such as weathering or surface waves.

Mooring lines having a length of more than 800 meters are also made of steel wire, but in addition to being very heavy, they can not 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 can not withstand its own load due to its increased length, and the risk of breakage is great. Moreover, these steel wire mooring lines often require extra buoyancy and, in the event of failure under load, the heavyweight steel wire mooring line increases the risk of damaging the hardware that may be contacted.

Polyethylene fibers of high stiffness are also used to produce the mooring line. Mooring lines comprising polyethylene fibers have, for example, a higher strength than a mooring line containing polyester fibers with the same diameter. It is also lightweight and has the advantage of excellent handling characteristics. A disadvantage of mooring lines having a length of more than 800 meters and having the purpose of securing the floating system in place is that due to the higher stiffness of the polyethylene fibers the up and down movement of the floating system due to water or surface waves, Which can cause high tensile strength and high peak load.

Due to the above listed drawbacks, known mooring lines having a length of more than 800 meters are less suitable for permanent mooring of floating systems if the distance between the fixed anchor point and the floating system is too long .

It is an object of the present invention to provide a mooring line having a length of at least 800 meters, suitable for anchoring the floating system in place, wherein the mooring line comprises synthetic fibers and provides an improved balance of size and mechanical properties .

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

Surprisingly, the mooring line according to the present invention (hereinafter referred to as a modular mooring line for the sake of convenience) can more accurately maintain the floating system in its original position. A further advantage is that the modular mooring line has different mechanical properties as it includes modules with different compositions, thus better dampening the high peak loads that occur on the modular mooring line due to waves, wind or water currents. The modular design of mooring lines further facilitates the tunability of the mooring lines for specific applications that require a precise balance between the floating system and high peak loads. A further advantage is that due to its special modular design, the tension of the modular mooring line is reduced. A further advantage of the modular mooring lines is achieved by adjusting the composition of the modules to obtain a correct balance of strength and size of modular mooring lines, as will be apparent from the present disclosure.

A line is a similar structure that includes ropes, cords, twines, cables, strings, and fibers, or includes fibers and staple fibers. I understand. Here, mooring line is understood as a line used to anchor a floating system to a fixed anchorage point.

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

Preferably, the module is provided with a connector at both ends, which is used when connecting one end of the module to one end of another module to form the mooring line. Furthermore, the connection may also be used to connect the modular mooring line with a fixed anchor point and a floating system. The connection may be, for example, a different type of shackle, loop, or the like. For example, one end of one module and one end of another module are connected using the connection to obtain two modules in series. 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. According to a particular application, one skilled in the art can select a suitable combination to provide a modular mooring line that provides an improved balance in terms of size and mechanical properties.

The floating system is understood to be a predetermined system anchored at berth by mooring line. The water-flooded system may be a floating system on the water surface or an underwater floating system at a particular depth of water, suitable examples being float production storage and unloading vessels, column buoys, anti-submersible systems or other hydrocarbon storage and / And / or a processing system.

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

The synthetic fibers constituting the module are obtained by twisting together the synthetic filaments. Preferably, the synthetic fibers comprise at least 100 synthetic filaments, more preferably at least 200 synthetic filaments, even more preferably at least 300 synthetic filaments. Synthetic filaments can have a widely varying linear density or titre, and preferably the reverse of the synthetic filaments is 0.2 to 50 dtex per fiber, more preferably 0.3 to 20 dtex and most preferably 0.4 to 10 dtex to be.

Also, the synthetic fibers are preferably twisted to form yarns, which preferably comprise at least 10 synthetic fibers, more preferably at least 20 synthetic fibers, even more preferably at least 50 synthetic fibers . The yarns are preferably further twisted to form strands, wherein each strand preferably consists of at least ten yarns, more preferably at least twenty yarns, and most preferably at least fifty yarns. The module can be obtained by laying, plaiting or braiding of the strands or a combination thereof. Skilled artisans may choose a structure type that is related to the desired final structure and size based on their knowledge or with the aid of some calculations or experiments. Suitable examples include hollow braided or laid modules, solid or solid type raidal modules, twisted type braid modules, plain braids or plain raid modules, and the like. The module structure is not limited to the above-mentioned module structure, and any other module structure can be used successfully according to the present invention.

The fibers comprising the module and / or the module may be further coated with a lubricating coating applied thereon to reduce wear and internal friction to prevent galling and fretting, thereby prolonging the life of the module, It is possible to prevent the inflow into the module. The module may further include a particle filter used as a barrier to prevent ingress of abrasive particles and at the same time allow the environment, i.e. air or water to circulate within the module.

Embodiments of a preferred embodiment of a modular mooring line according to the present invention, which implements the advantages gained by using the module of the present invention, are presented below. It is to be understood that the preferred embodiments are not limited to those set forth hereinbelow and those skilled in the art will readily ascertain additional embodiments and advantages in accordance with the invention that will become apparent from the following detailed description, .

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

Preferably, all of the modules of the modular mooring line according to the present invention comprise synthetic fibers, more preferably all modules are composed of synthetic fibers.

In a more preferred embodiment, the modular mooring line according to the invention comprises at least a first and a second module, wherein the first module comprises polyester fibers.

In another more preferred embodiment, the modular mooring line according to the invention comprises at least a first and a second module, wherein the second module comprises a high performance polyolefin fiber as a second fiber.

In another more preferred embodiment, the modular mooring line according to the invention comprises at least a first and a second module, wherein the first module comprises at least 51% by weight of first fibers and the second module comprises at least 51% Or more of the high-performance polyolefin fibers as the second fibers.

The first fiber in the first module may be a fiber obtained from any kind of material suitable for fiber production, such as a copolymer of propylene, polyester, polypropylene or polyester, nylon, and the like, and combinations thereof. Preferably, the first module comprises at least 60% by weight of the first fibers, more preferably at least 75% by weight of the first fibers, most preferably at least 95% by weight of the first fibers. Following the first fiber, the first module may also comprise 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 at least 60% by weight of high performance polyolefin fibers, more preferably at least 75% by weight of high performance polyolefin fibers, most preferably at least 95% by weight of high performance polyolefin fibers as second fibers. High performance polyolefin fibers Next, the second module may also comprise other types of fibers.

Preferably, the free end of the second module comprising the high performance polyolefin fibers is connected to an anchor which will provide an anchoring point at the seabed. Thus, a free end of the module comprising the first fiber is preferably provided with a connection suitable for anchoring the modular mooring line to the floating system. The connection between the free end of the modular mooring line according to the present invention and the anchor which will provide the anchoring point at the bottom of the flooded system and the bottom of the sea is achieved by a steel wire rope or steel chain with a predetermined length, ≪ / RTI > Once installed, the steel rope or chain may be provided with a modular mooring line according to the present invention and an anchoring point in a flooded system or submarine in order to prevent any actual damage that may be induced to the module by friction, mishandling, To prevent direct contact between the electrodes.

Another preferred embodiment is a modular mooring according to the invention comprising at least a first and a second module, wherein the first module comprises at least 51% by weight of polyester fibers and the second module comprises at least 51% And a high performance polyolefin fiber as a 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 ultra high molecular weight polyethylene (UHMWPE) fibers.

This embodiment of the modular mooring line according to the present invention combines durability specific to polyester fibers and light weight and high strength specific to low creep and UHMWPE polyethylene fibers to significantly reduce the total weight and volume of the modular mooring line And improves handling properties. It has been found that the weight and volume of the modular mooring line according to the present invention is considerably reduced in comparison with conventional polyester mooring lines. A further advantage is that the underwater rupture length of the modular mooring line is significantly increased. Because of the lightweight nature, the modular mooring has improved handling and increased safety for personnel involved in the installation and management of the modular mooring line, as well as the risk of damage to the hardware that may come into contact with the modular mooring line . The modular mooring line according to the invention also exhibits enhanced tension, torsion and flexural fatigue.

The presence of a module comprising polyester fibers with lower stiffness than UHMWPE fibers has the advantage that the effect of heave properties on the drill string etc. is efficiently detuned. Therefore, the presence of a module comprising polyester fibers helps provide a good buffering capability to the modular mooring line to reduce the peak load generated in the modular line.

In addition, the modular mooring line provides a good combination of stiffness, elongation at break and energy absorbency. A further advantage is that the presence of the module containing the UHMWPE fibers helps to keep the floating system more accurately in its original position and also after a long period of use.

Therefore, when the modular mooring line is used in accordance with the present invention, excellent fastness in the modular mooring line, excellent controllability of the movement of the floating system, and minimization of the total tension are achieved. The modular mooring line is particularly suited for use in locating floating systems in places where storms are frequent or where water currents are extremely strong. Examples of such places include the Gulf of Mexico, where hurricanes, strong winds, and strong water currents are constantly generated.

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 greater than 75%, more preferably greater than 90% terephthalic acid Lt; RTI ID = 0.0 > dicarboxylic < / RTI > acid component. 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- Lt; / RTI > 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 . 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 fiber is preferably 3% or more, more preferably 10% or more, and most preferably 16% or more. The reversal of the polyester fiber is preferably 50 dtex or less, more preferably 110 dtex or less, and most preferably 220 dtex or less.

UHMWPE fibers are preferably prepared according to a gel spinning process. Gel emulsions of UHMWPE are known to those skilled in the art and are 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. The gel spinning can be carried out by spinning one or more fibers from a solution of ultrahigh molecular weight polyethylene in a spinning solvent; Cooling the resulting fibers to form gel fibers; At least partially removing the spinning solvent from the gel fiber; And withdrawing the fibers in one or more drawing steps before, during or after the removal of the spinning solvent. Suitable spinning solvents include, for example, paraffin, mineral oil, kerosene or decalin. The spinning solvent may be removed by a combination of evaporation, extraction or evaporation and extraction routes. The cross-sectional shape of the fibers can be selected by selection of a radiation aperture shape.

In the context of the present invention, ultra-high molar mass polyethylene (UHMWPE) is understood to be polyethylene having an intrinsic viscosity (IV) of at least 5 dl / g. IV used decalin as a solvent for UHMWPE at a temperature of 135 캜, using an antioxidant DBPC in an amount of 2 g / l solution for 16 hours of dissolution time, extrapolating viscosities at different concentrations to 0 concentration, -179 (Hercules Inc., Revised April 29, 1982). UHMWPE having an IV of preferably 8 to 40 dl / g, more preferably 10 to 30 dl / g, even more preferably 12 to 28 dl / g, most preferably 15 to 25 dl / g, Suitable.

Preferably, the UHMWPE has linear branched polyethylene having less than one branch chain and side chain per 100 carbon atoms, preferably less than one branch per 300 carbon atoms, and the branch is usually linear polyethylene containing at least 10 carbon atoms . The linear polyethylene may additionally contain up to 5 mol% of an alkene such as one or more comonomers 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 such groups have reduced creep properties. If the side chains are too long, or if the amount of side chains is too large, their presence will negatively affect the properties of the process and especially the drawability in the processing of UHMWPE fibers. 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 one per 1000 carbon atoms. The amount of side chain is preferably not more than 20 per 1000 carbon atoms, more preferably not more than 10 per 1000 carbon atoms.

The UHMWPE may be a homopolymer grade, but may also be a mixture of two or more different UHMWPE grades. A UHMWPE grade is understood to be a UHMWPE having a specific IV or molar mass distribution and having a specific number of side chains having a particular configuration.

The UHMWPE polymer may additionally contain conventional 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, For example, other polyethylenes, polypropylenes or copolymers thereof (including rubbery copolymers such as EPDM, EPR, etc.).

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

Preferably, the tensile strength of 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-fiber as described in ASTM D885M using a fiber nominal gage length of 500 mm, a crosshead speed of 50% / min and an Instron 2714 clamp, type Fiber Grip D5618C do.

Preferably, the stiffness of 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, most preferably at least 140 GPa. In a preferred embodiment, the stiffness of the UHMWPE fiber is 110 GPa to 135 GPa.

The length of the first module comprising polyester fibers is preferably less than 2000 meters, more preferably less than 1500 meters, even more preferably less than 1000 meters, even more preferably less than 500 meters, even more preferably Is less than 350 meters, and most preferably less than 200 meters. The ratio between the length of the module comprising polyester fibers and the length of the module comprising UHMWPE fibers is preferably not more than 90%, more preferably not more than 60%, most preferably not more than 30%.

The advantage of adjusting the ratio is that the module comprising UHMWPE fibers, depending on where the modular mooring line is used, is located at a water depth of preferably less than 15 °. This ensures that the water temperature uses the module containing the UHMWPE at the water depth to help preserve the mechanical properties of the UHMWPE fiber.

Claims (16)

A mooring line having a length of at least 800 meters and connected to an anchoring point fixed at one end and connected to a water floating system at one end, The mooring line comprising at least a first module and a second module, wherein at least the first module and the second module have a different composition of synthetic fibers, Wherein the first module is provided with a connection for anchoring the mooring line to the floating system, Wherein the second module is provided with a connection portion for connecting the mooring line to the anchor point, Wherein the first module and the second module are provided with connection portions for connecting one end of one module and one end of another module, Characterized in that the second module comprises at least 51% of high performance polyolefin fibers which are ultra high molecular weight polyethylene (UHMWPE) fibers as second fibers. The method according to claim 1, Characterized in that said first or second module has a length of at least 100 meters. The method according to claim 1, Characterized in that the first module comprises polyester fibers. The method according to claim 1, Characterized in that said first module comprises at least 51% by weight of first fibers. 5. The method of claim 4, Characterized in that said first module comprises at least 60% by weight of first fibers. 6. The method of claim 5, Characterized in that said first module comprises at least 95% by weight of first fibers. The method according to claim 1, Characterized in that said second module comprises at least 60% by weight of UHMWPE fiber as a second fiber. 8. The method of claim 7, Characterized in that said second module comprises at least 95% by weight of UHMWPE fiber as a second fiber. 5. The method of claim 4, Characterized in that said first module comprises at least 51% by weight of polyester fibers. The method of claim 3, Characterized in that the polyester fibers have a tensile strength of at least 0.6 GPa and a break elongation of at least 3%. The method according to claim 1, Characterized in that the UHMWPE fiber has a tensile strength of 1.5 GPa or more and a stiffness of 35 GPa or more. The method of claim 3, Characterized in that the length of the first module comprising polyester fibers is 2000 meters or less. 13. The method according to any one of claims 1 to 12, Characterized in that the ratio between the length of the module comprising polyester fibers and the length of the module comprising UHMWPE fibers is 90% or less. delete delete delete