NL2019011A - Line or line system and systems comprising such line or line system - Google Patents

Abstract

Line or line system comprising at least a main line and at least one additional line, wherein the additional line is attached at two spaced apart positions between opposite ends of the main line, such that when the additional line extends substantially straight between said two spaced apart positions, the part of the main line between said two positions is deformed such that it can be elongated substantially without stretching of the said part of the main line

Description

Octrooicentrum

Nederland

© 2019011 (21) Aanvraagnummer: 2019011 © Aanvraag ingediend: 1 juni 2017 © A OCTROOIAANVRAAG (51) Int. CL:

D07B 5/00 (2018.01)

© Aanvraag ingeschreven:	© Aanvrager(s):
7 december 2018	Rotortug Holding B.V. te Rotterdam.
© Aanvraag gepubliceerd:
10 december 2018	© Uitvinder(s):
	Xavier Blejan te Rotterdam.
	© Gemachtigde:
	ir. C.M. Jansen c.s. te Den Haag.

54) Line or line system and systems comprising such line or line system

57) Line or line system comprising at least a main line and at least one additional line, wherein the additional line is attached at two spaced apart positions between opposite ends of the main line, such that when the additional line extends substantially straight between said two spaced apart positions, the part of the main line between said two positions is deformed such that it can be elongated substantially without stretching of the said part of the main line

NL A 2019011

Deze publicatie komt overeen met de oorspronkelijk ingediende stukken.

P115004NL00

Title: Line or line system and systems comprising such line or line system

The present disclosure relates to a line system for connecting at least two objects to each other. Lines and line systems are a means of connecting two or more objects and the prior art recognizes a wide range of ropes, wires and lines constructed from a range of different materials and combination of materials such as steel wire, or synthetic materials such as polyester, polyethylene, polyamide, spectra and UHMWPE fibres and applied coatings with a range of characteristics deemed desirable for such systems.

Such line systems are used in a range different applications, including, but not limited to, rigging, hoisting, biting, mooring, anchoring, towing operations either in a marine and/or subsea environment or for example land-based activities. Such line systems dynamic behaviour can be considered as a mass-spring system. In a number of the aforementioned applications line tension can be very high in a short period due to the dynamic behaviour of the mass-spring system and initiated tensile loads in said system. These high peak loads are undesirable and therefore one or more components are often applied in line systems between lines or parts thereof to dampen out dynamic behaviour and associated peak loads. Another method can be that the main lines in a line system are constructed from fibres with higher elasticity characteristic. In this way the line system service life is extended and dynamic peak loads are avoided. A disadvantage of such more elastic fibres is that such fibres such as polyamide and polyester fibres have a lower strength characteristic and are heavier compared to UHMWPE fibre material.

A drawback to including components to dampen out dynamic behaviour and associated peak loads in a line system in a serial configuration is that it introduces additional connections and failure modes in a line system. For example when such a component, or one of the connections fail, the line system fails to connect two or more objects. A new connection must be established with a new line system.

Generally a purpose of the present disclosure is to provide an alternative line and/or line system. A purpose of the present disclosure is to 5 provide for a line and/or lines system with the ability to absorb dynamic peak loads and retaining the strength and light weight characteristics. A purpose of the present disclosure is to provide for a line and/or line system with strength and light weight characteristic associated with UHMWPE fibre materials. In particular a purpose of the present disclosure is to 10 provide a line and/or lines system with an improved abihty to absorb dynamic peak loads and subsequent peak and/or shock loads on fairleads and other points of contact within the lines system as compared to the prior art. A purpose of the present disclosure is to provide for a line and/or line system or device intended to avoid breaking of lines and limit or avoid 15 dynamic peak loads in a line system acting as a mass-spring system.

A purpose of the present disclosure is to absorb such peak loads without the use of additional connections associated with one or more components in a serial configuration and the additional failure modes associated with such configurations and connections. A purpose of the 20 present disclosure is to improve the handling characteristic of lines or line system with components in a serial configuration.

For this purpose the present disclosure embodies a line system in which one or more stretcher components are provided in a hne or line system in an alternative configuration. In embodiments at least one 25 stretcher component is provided in a line or line system connected in a parallel stretcher configuration with a longitudinal direction of a line or lines connected with such component. In embodiments at least a or at least one stretcher line is spliced into a main load-bearing line creating a line sub-system in one part of a line system or a line. In embodiments a parallel 30 configuration can be arranged such that initial loading is absorbed by at least one stretcher line and subsequent loading is absorbed by a main load bearing line. The elasticity-curve for the sub lines system can be arranged such that Dynamic Amplification of apphed loads is prevented. With lower dynamic amphfication factors compared to the prior art design loads can be subsequently lowered accordingly.

Fig. 1A-D are a schematic view of line systems, to illustrate the possible components of a line system and their respective positions;

Fig. 2A - D are embodiments of a line or line system according to the disclosure;

Fig. 3A - B illustrate a serial and parallel line system configurations respectively.

Fig. 4A - C illustrate how a load F develops over time subject to the specific arrangement and configuration of a line system; and

Fig. 5A - C illustrate an embodiment of the present disclosure.

In this description exemplary embodiments of the present disclosure are shown, by way of example only. These should by no means be considered as limiting the scope of the present disclosure. The drawings are schematic only. In these drawings the same or similar reference signs shall be used for the same or similar parts or features.

In this description a line should be understood as a single line or a series of lines intertwined or otherwise connected in a substantially side by side configuration such that they have a substantially parallel longitudinal direction substantially parallel to or coinciding with a longitudinal direction of the line. In this description a line system includes, but is not limited to, a minimum of two lines and/or ropes, possibly guided by one or more sheaves, fairleads, or other guiding apparatus and connected to one or more objects. A line can also be a cable, rope, wire or combinations thereof, and can be made of any suitable material, unless specified otherwise.

In this description practicable has to be understood to mean at least but not limited to the ability to pull a line or line system or at least part thereof according to the present disclosure along guiding apparatus or fairleads and the ability to be handled by human power, preferably by a single person. In the present disclosure practicable can also be understood to mean a significantly lower weight compared to existing art serial configurations stretcher line systems.

In this description a spring constant k is defined as per Hooke’s Law providing a key characteristic of lines within a line system with different strand and fibre arrangements and (mixed) fibre materials providing different /«-value properties to individual lines. Within the scope of the present disclosure lines are considered theoretically as if they can substantially only absorb tensile loads, as per Hooke’s law, but can be compressed to a limited degree due to the strand arrangement in a line.

UHMWPE fibres are very popular in a range of rigging, lifting, hoisting and towage applications due to their high strength and light weight 15 characteristics and associated practicable handling characteristic. In some applications a drawback of UHMWPE fibres is the high /«-value property compared to other fibre materials. For example /«-values for polyamide lines can be about 20% of /«-value properties compared to lines of UHMWPE fibre construction with equal minimum breaking load (MBL).

Line system are subject to dynamic behaviour wherein the line system and objects attached thereto act as a spring-mass system with associated properties. For example lifting and hoisting applications are subject to dynamic wind loads, rigging applications are subject to loads by acceleration of the rigged objects and towage applications to imposed loads by a tugboat or towing vehicle where dynamic behaviour is to be expected. Dynamic loads can also result due to inertia of an object connected to a line or for example resistance, for example in water and/or air and/or wheels acting on an object to be moved by such line or line system. High /«-values for known UHMWPE fibre based ropes result in significant dynamic amplification of loads F in the line system and connections to other objects.

Said dynamic amplification of loads F is mitigated in the present day art by including additional lines with different /«-values in a serial configuration in the line system mixing and matching line properties to create suitable line system properties. An advantage to this configuration is that effective /«-values are lowered overall, but at the same time additional connections and associated failure modes are added to the line system. Furthermore the lower /«-value lines are not as practicable at same MBL as the high /«-value UHMWPE fibre lines.

In general terms an integrated stretcher configuration according to the description enables an advanced line system configuration with improved response to dynamic loads and lower dynamic amplification factors in the line system. More specifically the integrated configuration according to the description is of a practicable execution and eliminates dynamic amplification during load initiations.

In a line or line system according to the present disclosure a main line or line system can be provided, having a longitudinal direction when positioned in a substantially straight line between opposite ends thereof. Furthermore preferably at least one additional line or line system is provided having a longitudinal direction substantially parallel to the longitudinal direction of the main line or line system when positioned in a substantially straight line between opposite ends of the additional line or line system. The ends of the additional line or line system are fixedly connected to two separate positions of the main line or line system in between the ends of the main line or line system, such that when the main line is tensioned in the longitudinal direction by a pulling force in the main line or line system two different phases can be recognized. In a first phase, in which the tensile force is between about 0 and Fi, the tensile force between the end points of the additional line or line system is primarily absorbed by stretch of the additional line or line system, without substantial rise of tension in the main line or line system part extending alongside the additional line or line system between said end points of the additional line or line system. In a second phase, in which the tensile force exceeds Fl, the tensile force will at least be absorbed in part by the main line or line system, and will increasingly be absorbed by the main line or line system when the tensile force in the line or line system in total is increased further.

In a line or line system according to the present disclosure a main line or line system can be provided, having a longitudinal direction when positioned in a substantially straight line between opposite ends thereof. Furthermore preferably at least one additional line or line system is provided having a longitudinal direction substantially parallel to the longitudinal direction of the main line or line system when positioned in a substantially straight line between opposite ends of the additional line or line system. The ends of the additional line or line system are fixedly connected to two separate positions of the main line or line system in between the ends of the main line or line system. The main line or line system can have a /«-value higher, preferably significantly higher than the /«-value of the additional line or line system. Part of the main line or line system extending along the additional line or line system between the opposite ends thereof may have fibres or strands positioned such that the additional line or line system can be elastically stretched in a longitudinal direction over a first distance without significant increase of tensile load in the fibres or strands of the said part of the main line or line system.

In embodiments the part of the main line or line system bridging the additional line or line system may in an initial state, i.e. a state in which the 25 additional line or line system is not stretched, may for example be slightly compressed. The fibres or strands in said part may for example be more undulating than in the further main line or line system when in a straight line, such that said part can be extended in length over a first length by at least partly straightening of the fibres or strands in said part. In embodiments the said part of the main line or line system may, with the additional line or line system in said initial state, be ruffled or may extend in a non-straight line along the additional line or line system positioned in a straight hne, such that when stretching the additional line or line system over a first length, the said part can be straightened first.

When in such line or line system the additional line or line system has been stretched over said first length the part of the main line or hne system extending between said opposite ends of the additional line or line system may be brought into a position in which it will be able to transfer tensile loads in the main line or line system directly, wherein the /«-value of the complete line or line system will substantially be defined by the /«-value of the main line or line system. The additional line or line system will only stretch further at the same rate as the part of the main line or line system bridging the said additional line or line system stretches, which stretch will basically be defined by elastic deformation of the fibres or strands of said main line or line system. Such elastic deformation and hence stretching will be significantly less than elastic deformation of the additional line or line system would be if subject to the same tensile load by itself.

In the description of the drawings references to lengths, loads and tension are for the sake of convenience considered when the line or lines extend in a substantially straight configuration between ends 20, 21 thereof.

In general a hne or hne system according to the present disclosure can comprise at least a main line and an additional line. The main line can have a length larger than the additional line, such that the additional line can be attached at two spaced apart positions between opposite ends of the main line, such that when the additional hne extends straight between said positions, the part of the main line between said two positions is deformed such that it can be elongated substantially without stretching of the said part of the main line. Then additional line can be more elastic than the main line. This should in this context at least be understood as meaning that when the said part of the main line and the additional line are separately brought under the same tensile load in their longitudinal direction, the additional line will elongate further than the main line part. Hence when the main and additional line as described are subjected to a tensile load in the longitudinal direction first the additional line will stretch, elongating the said part of the main line without significantly stretching the main line. When increasing the tensile load after a while the additional line will have stretched such that the said part of the main line will be elongated maximally without stretching. If from that point on the tensile load is increased even further, both the additional line and at least said part of the main line will stretch. Since they are connected at said points, their stretching will then be substantially identical. The additional line will hence in the first phase, that is during elongation of the said part of the main line without stretching have a dampening effect on peak loads. Whereas when the said part is part of an integral main line any undesired breaking of the additional line or loss of connection between the main line and the additional line will not mean a loss of connection between objects connected by the main line.

In this context deformed with regard to the said part of the main line should be understood at least as meaning that it can be elongated in a substantially longitudinal direction towards a substantially straight position in a form and orientation similar to the further parts of the main line without stretching, and may include but is not limited to one of extending in a curved or undulating direction, compressed, having strands and/or fibres in an intertwined position wherein the strands and/or fibres are more curved than in a non-deformed position, ruffled or any such deformation from a position and orientation the part would have if maximally elongated and straight without being stretched.

Figure 1A - D schematically shows a number of different line systems 1 viewed from the side, with a number of possible lines 2 and line connections 3. A line connection 3 is defined hereinafter as connecting the end-piece of a line 2 to another part of the line system 1. Said line system can include physical contact points 4 that fairlead a line 2 to an object O, establishing a connection 5 between the line system 1 and object 0 capable of sustaining significant tensile forces 6. Herein a contact point is to be understood as also including a line contact or relatively small area of contact.

Fig. 1A shows two examples of a line system comprising two lines 2 connected by a line connection 3, for example engaging loops 2A, 2B, hooks, rings or the like, or a splicing. Opposite ends 20, 21 of the line system 1 can 10 be connected to or provided with connectors for connection to different objects, for example for but not limited to towing, hoisting, mooring.

In fig. IB a line 2 is shown, having one end 20 connected to an object O at a connection 5, wherein the line 2 extends through a guide element 4, for example a fair lead. This can for example be part of a mooring or towing 15 system. A second end 21 of the line or line system 1 can be provided with a connector (not shown) for connecting to a further object O, such as for example a vessel, towing boat or the like.

In fig. 1C an embodiment is shown of at least part of a hoisting system 101, wherein a line 2 is led over a guide element 4, such as a guide 20 at the end of a crane arm. A winch 7 can be provide for pulling the line 2 and hence lowering or lifting an object O, for example a load L connected to an end 20 of the line 1 or line system 1 by a line connection 3 at 2C.

In fig. ID an embodiment is shown of at least part of a towing system 102. This comprises a tug boat V with a winch 7 from which a line 2 or line 25 system 1 comprising lines 2 extends, via a guide element 4, such as a fair lead, to an object O to be towed. This can for example be a vessel, platform or the like. An end 20 of the tow line 2 or line system 1 comprising such line 2 is connected to the object O at line connection 5. In fig. ID two towing lines 2 are shown in the line system 1, interconnected by a line connection 3.

However, in embodiments only a single line 2 or multiple lines 2 can be used.

In towing systems 102 a line system 1 can include a winch 7 or tensioner device 7. Historically with winches, the towing cable length can 5 be adapted to the desired length and distance only. Render and recovery towing winches are able to apply and/or maintain a constant pulling force on a towing cable connection 5 at a first end 20, in case object O and the line system base, that is the position where the opposite end 21 of the towing line 2 or line system 1 is connected, for example a tow boat 101 on which the 10 winch 7 is mounted, move relative to each other due to for example heavy seas or winds. Said winches are also known as render & recovery, rend & receive, constant tension winches, umbilical winches or escort winches depending on the application, either term being interchangeable with the other for purposes of the present disclosure.

Obviously a line connection can also be established by a single line, for example by connecting a line 2 as shown in fig. ID, extending from the winch 7, directly to an object O, such as a vessel to be towed, without a further line 2 and line connection 3.

Lines or line systems hereafter discussed can be used for example but 20 not limited to as or in a line or line system as disclosed in fig. 1.

Fig. 2A - C schematically show a line system 1 comprising a main line 2i having opposite ends 20, 21 and a longitudinal main direction L_m between said ends 20, 21. An additional line 22 having opposite ends 22, 23 has a longitudinal length L_a which is significantly smaller that the length L_m. The 25 ends 22, 23 of the additional line 22 are fixedly connected to the main line 2 j at positions 25, 26 between the ends 20, 21 thereof, such that a part 24 of the main line 2j bridges the additional line 22.

As can be seen in fig. 2A, when the line system 1 is not loaded, the additional line 22 is in a straight, non stretched configuration, having the length L_a. In this position the said part 24 has an overall length L_pi too, which is less than the length L_p of said part 24 would be when not connected to main line 2i and in a relaxed state, i.e. not stretched or compressed. In fig. 2A the said part 24 is shown in exaggerated undulating position, the overall length L_m defined as the distance in a straight line between the connections 25, 26.

In fig. 2B the line system 1 is shown in a loaded position by a pulling force F in longitudinal direction of the line system 1, stretched over a first length AL_m, which is substantially equal to the length AL_a over which the additional line 22 is stretched. In this position the overall length L_pi of the part 24 is substantially equal to the length L_p of the part in substantially relaxed, non-stretched and non-compressed state, as discussed. In this position the said part 24 and the additional line 22 are both substantially straight having parallel longitudinal directions L - L.

As schematically shown in fig. 2C, when the load F is increased further from the position as shown in fig IB, the main line 2i will substantially bear tensile load F, wherein the line system 1 will be stretched to a length L_m + AL_m2. The stretching will occur over substantially the entire length L of the line system 1, wherein the part 24 will also stretch slightly, stretching the additional line 22 as well slightly further over a length AL_a2, which will be significantly smaller than AL_a.

Obviously, when the load F is a dynamic load, initially a change in the load F will more easily be absorbed by stretching of the additional line 22, having a lower /«-value, than by stretching of the main line 2 i thus dampening the effects of such changing loads F.

In fig. 2D in partial sectional view in a plane parallel to a longitudinal axis L - L, a relevant part of a line system 1 is shown, in an alternative embodiment, in which an additional line 22 is integrated into a main line 21, for example spliced into it, as for example also shown in fig. 4. The main line 2i extends with part 24 like a mantel around the internal additional line 22, wherein the mantel forming part 24 is slightly ruffled and/or compressed, such that it can be straightened substantially without the necessity of elastically deforming, especially substantially without elastically stretching it. Hence during a first phase the line system 1 can be elongated basically by stretching the additional line 2a without significantly stretching the main line 21. Passed the first phase, that is at further increasing a force F, the main line 2i will stretch as well, taking a major part of the tensile force.

In a line or system according to the disclosure the additional line or the combination between the additional line and the part of the main line 10 extending along it can also be referred to as a stretcher.

Figure 3A illustrates a serial configuration of a line system 1 or additional system thereof with defining /«-values /«i, /«2 and /«3 and lengths Zi, /2 and Z3 of lines 21, 2^ and 2;j respectively in said line system 1 wherein the configuration of line lengths and k-values define the line system’s response to dynamic loads F and/or imposed movements. Figure 3B illustrates a parallel configuration of another line system 1 or part thereof according to the description with defining /«-values Z«i and /«2 and lengths Zi and Z2 of lines 2 i and 22 respectively in said line system 1.

Figure 4A illustrates how dynamic loads F develop over time subject to the characteristics of line system 1 as illustrated in figure 3A. A high dynamic amplification F_milx as illustrated in figure 4A has a negative impact on the mean time to failure of a line system 1 and connections to other objects Oi and O2 as well as an adverse effect on said objects and their respective structure. Figure 4B illustrates the envisioned dynamic loads F development over time with favourable characteristics of a line system 1 as illustrated in figure 3B. Fig 4C illustrates how the Reaction force F develops as a function of elongation δ for an additional line system in a parallel configuration. Furthermore fig 4C illustrates how the present disclosure can be arranged such that the envisioned dynamic load response as per fig 4B can be achieved by adjusting the pre-compression of line 2i and length of line 2s and selecting the advantageous characteristics for lines 2i and 2'2.

In an example, which should not be considered limiting, the mainline 2i can for example be a Dyneema line, for example 44 mm in diameter for example type SK78, 12 strand plaited. The MBL of such line can for example be 1559 KN with 2% elasticity (MBL = Minimal Breaking Load). In an example, which should not be considered limiting, the additional line 2y can for example be a polyester based line, for example polyester parallel strand, for example 80 mm in diameter. Such line can have a reduced strand size at an MBL of about 1135 KN, with 10% elasticity, starting from an MBL of 2270 KN. It can have an effective stretch length of about 5 meter.

Figure 5A illustrates in side view a part of an embodiment of the present disclosure with a parallel configuration of fines 2i and 2s with associated properties illustrated in figure 3B and wherein line 22 is connected to line 2 i on two ends 22, 23 by means of two splices 8_a and 8b forming connections 25, 26. Within the scope of the description splices 8_a and 8b can be for example [x] type splices, but can also be other types of splices. In this embodiment of the present disclosure line 2iis precompressed to a limited degree to secure a smooth transition between load distribution within the line system 1 when a load F is applied to same as illustrated in figure 4B. In embodiments of the present disclosure the fibres and/or strands of lines 2i and/or 22 can be coated with a high friction coating to increase the strength of splices 8_a and/or 8b and/or a reduced length of the splice or splices..

Figure 5B schematically illustrates a cross-sectional view of an embodiment of a line system according to the present disclosure along the line 5B-5B in fig. 5A, with a main load bearing line 2i and stretcher line 22 arranged therein. Fig. 5C schematically illustrates a cross-sectional view of an embodiment of a line system according to the present disclosure along the line 5C-5C in fig. 5A, with a main load bearing line 2i and stretcher line

2₂ arranged therein. In fig. 5 the strands 27, 28 are only schematically and partly shown, representing a known structure of lines such as ropes and wires with twisted, intertwined strands of fibre material, wherein splices 8a, 8b are also only schematically indicated. Line splices of different types are well known in the art.

In embodiments the at least one main line 2i can be made using a plastics material, for example a high strength plastics material such as for example but not limited to UHMWPE fibre. In embodiments the at least one additional hne 2₂ can be made using a plastics material, for example a less 10 high strength and/or more elastic plastics material such as for example but not limited to polyester or nylon (PA) material. In embodiments the main line can be made using intertwined strands of fibre material such as UHMWPE and the at least one additional hne can be made of a further plastics material or combination of materials, for example also comprising 15 intertwined strands of plastics material, such as but not limited to PA or polyester. The ends 22, 23 of the additional line 2? or stretcher may be spliced in between strands 27 of the main line 2i. For example as shown in fig. 5 by splicing strands 28 of the additional line 2a in between strands 27 of the main line 2i. Strands 27 and/or 28 may be coated, for example at least at the positions where they are spliced, for example with a coating 29 increasing friction between the strands 27 and 28. Preferably the lines 2 are made such that during longitudinal loading of the line in a direction of elongation, strands of at least the main line 2i will be pulled together, thereby tightening the splicing. Coatings like for example polyurethane coatings can inhibit specific characteristics to a fibre material such as reducing, or, enlarging friction and/or improving resistance to for example UV fight.

The invention is by no means limited to the embodiments, materials and uses as discussed by way of examples. Many variations are 30 possible within the scope of the present disclosure, with regards to the claims. For example combinations of embodiments or parts thereof as discussed and shown are also considered to have been disclosed herein.

Moreover, a line or line system of the present disclosure can comprise one or more main lines and one or more additional lines. If more than one additional line is used, such additional lines can be provided parallel to each other, at or in the same part 24 of a main line, or they can be positioned spaced apart in a longitudinal direction of the line, and can have the same or different Λ-values. The lengths of the main line or lines can in embodiments be limited to about the length of the additional line or lines.

Claims (20)

Conclusions A line or line system comprising at least one main line and at least one additional line, the additional line being attached to two spaced positions between opposite ends of the main line such that when the additional line extends substantially straight between the two remote positions, the part of the main between said two positions is deformed such that it can be extended substantially without stretching said part of the main line. The line or line system of claim 1, wherein the at least one additional line has a first k value and the main line has a second value, the first k value being lower than the second k value. A line or line system according to claim 1 or 2, wherein the additional line comprises strands of fiber-based material, wherein the additional line has opposite ends inserted into the main line at said two remote positions. A line or line system according to any of claims 1 or 2, wherein the additional line has opposite longitudinal ends connected to the main line at said two remote positions by connecting elements. A line or line system according to any one of claims 1 to 4, wherein the additional line is substantially surrounded by the main line. The line or line system of any one of claims 1 to 5, wherein said portion of the main line extends around the at least one additional line as a casing. A line or line system according to any one of the preceding claims, wherein the main line comprises a plastic material and is preferably made from plastic material, in particular a UHMWPE fiber line. A line or line system according to any one of claims 1 to 7, wherein the additional line comprises a plastic material and is preferably made from plastic material, in particular polyester, polyamide or nylon. A line or line system according to any one of the preceding claims, wherein the main line comprises entangled strands of material, preferably high-strength plastic material, such as UHMWPE fiber material, and has the additional line ends inserted into the main line between strands thereof. A line or line system according to any one of the preceding claims, wherein the at least one main line has a length that is longer than the length of the at least one additional line, at least in the unloaded state. The line or line system of any one of claims 1 to 9, wherein the main line and the additional line have substantially the same length, wherein opposite ends of the main line are provided with coupling elements for coupling the main line between two objects. A line or line system according to any one of the preceding claims, wherein the line or line system forms a tow line for towing vessels or is a part thereof. A line or line system according to any one of the preceding claims, wherein the main line extends integrally along the additional line, an integral connection being formed between opposite ends of the additional line. A line or line system according to any one of the preceding claims, wherein at least two additional lines are provided, which preferably extend substantially parallel to each other. A line or line system according to any one of the preceding claims, wherein at least one of the main line and the additional line comprises strands of fibers that are entangled, preferably both the main line and the additional line comprises strands of fibers that are entangled. The line or line system of claim 15, wherein at least some of the strands are at least partially coated, in particular with a friction-enhancing coating. A towing system comprising at least one line or line system according to any one of the preceding claims. The towing system of claim 17, further comprising a tugboat, the main line having a first end connected to the tugboat, and a second end comprising a coupling element for coupling to an object to be towed. 19. Hoisting system comprising a line or line system as claimed in any of the claims 1-16. A method of forming a line or line system, wherein in a main line comprising entangled strands or formed substantially therethrough, at least one additional line is inserted between strands of the main line, the additional line extending over a length of the main line between strands of the main line, wherein an additional line is used with a k value lower than the k value of the main line. 1/5 2 ₂ 23 4/5 5/5 Title: Line or line system and systems including such line or line system