WO2016039630A1

WO2016039630A1 - Fairing for rope

Info

Publication number: WO2016039630A1
Application number: PCT/NO2015/050154
Authority: WO
Inventors: Ole Bertil GISKEØDEGÅRD
Original assignee: Offshore & Trawl Supply As
Priority date: 2014-09-12
Filing date: 2015-09-04
Publication date: 2016-03-17
Also published as: NO20141103A1

Abstract

The present invention relates to a sheath (2) for an elongated, load-bearing body (3), said sheath (2) comprising several elongated sheath elements braided together around at least a portion of the elongated body, said sheath being equipped with a protruding fairing (1). The protruding fairing (1) comprises or is coated or impregnated with a material which prevents the protruding fairing from linting.

Description

Fairing for rope

The present invention relates to a sheath comprising so-called fairing for various types of drag or towing cables, hawsers and ropes for use in maritime environments.

In this context, there are two types of two types of towing, namely directly behind the ship or horizontally from the sides of the vessel, such as e.g. during trawling or seismic shooting. Towing is particularly challenging when done horizontally.

At higher towing speeds (over approx. 4 knots), a drag cable having a circular profile experiences high fluid resistance or «drag» in the water. However, higher towing speeds are often desirable or necessary in order to avoid loss of time and/or increased cost, e.g. when operating across larger areas. High fluid resistance means on the one hand that the tensile load on the cable grows large. This entails higher strain on the equipment, increased cost of towing the equipment (in the form of increased fuel cost), and reduced security of operation. In order to provide as low fluid resistance as possible for drag cables, it is common to use so-called fairings. There are different types of fairings, such as streamlined, wing- shaped members of synthetic material attached to a rope or cable, among others. Another type would be hair-like materials attached in a rope or cable.

A potential problem when using hair-like materials is the high exposure to wear of these hairs during use. The hairs are «eaten away» during towing in a maritime environment. The hair-like material will also develop into «lint». «Lint», «linty», «linting» and the like is used herein to describe hair-like structures, ribbons etc. that become worn down, split and frayed. This is considered a disadvantage as it reduces the effect of the fairing in water and contributes to increased wear. Also, the lint may easily entangle and form bundles. The hairs, possibly also woven or braided ribbons, form loops which are then cut so that hairs or ribbons hang down from the rope. When using ribbons, these too may get frayed quickly and form lint. It takes some time before the ribbon will get linty, and this time in itself accounts for a prolonged service life. Ribbons tend to have longer durability than hairs when it comes to linting. In addition to the factors mentioned in the above, which include properties during use, wear and short service life, there are also production aspects to be addressed. Regardless of the type of fairing chosen for use, various possible variants and improvements may be decisive for the cost and complexity of production, which in turn will impact the cost for the customer. It is generally known to use multifilament fibers, monofilament fibers and micro tape to form yarn. The yarns may be laid into a strand, which in turn may be laid/braided to obtain a hawser. The hawser comprises three or more strands.

Around the hawser, a protective sheath may be braided of yarn. The braided sheath may thus be comprised of multifilament fibers, monofilament fibers and micro tape laid into yarn. Such solutions leave a certain «space» between the sheath and the hawser and inside the sheath as such. This also gives room for the intrusion of particles. During use, the hawser will thus experience a certain «drag» when being pulled horizontally.

The sheath may also be placed on top of other cores, such as cables of plastics or steel etc. NO 314459 relates to a hawser comprising a core of parallel or braided core cords and a sheath of braided-on sheath elements, (some of) the sheath elements being made of woven ribbons comprising predominantly parallel filaments connected together by transversal strings.

The object of the present invention is to remedy one or more of the above disadvantages.

According to the present invention, this is achieved by an arrangement according to independent claim 1. Further advantageous or alternative embodiments are outlined in the dependent claims.

In the following, a detailed description of an advantageous embodiment is provided with reference to the accompanying drawings, in which

Fig. 1 shows an embodiment of the present invention.

It is known to use woven or braided ribbons protruding from the sheath of a drag cable, hawser or the like, to thereby form a fairing. As it takes the ribbon some time before it becomes frayed and forms lint, such a fairing lasts longer. The time it takes for the ribbon to become linty can be added to the regular service life of a linty fairing. Also, it has turned out that a fairing that has not yet become linty can behave as well or better than a linty fairing. Thus, it is desirable to prevent the ribbon from linting.

Fig. 1 shows an embodiment of the present invention, where woven or braided ribbons 1 protrude from the sheath 2 of a drag cable, hawser 3 or the like, each ribbon 1 being treated in such a way that linting is either completely avoided or substantially delayed. According to an embodiment of the present invention, each protruding ribbon 1 is coated with a plastic or other material forming a film or coating around each protruding ribbon 1.

Alternatively, each protruding ribbon 1 may be treated with an agent, e.g. a fully or partially curing adhesive or impregnating agent, which fully or partially penetrates each ribbon 1 and renders it non- linting. In this case, it may be desirable that the fully or partially curing adhesive or impregnating agent does not render the protruding ribbon too rigid or inflexible, since this could potentially impair the intended functionality of the fairing. Under certain circumstances, however, such rigid fairings have proven to be able to provide better streamlining properties.

According to another embodiment of the present invention, particles, elements or substances may be added to the coating, the adhesive or impregnating agent, which endow the fairing with improved or preferred streamlining properties. These may be particles, elements or substances which make the fairing smoother, or which interrupt or affect the flow characteristics around each ribbon 1 in a positive way. These may also be particles, elements or substances which give each ribbon prolonged service life or desired frictional properties. According to a possible process of production, the woven or braided ribbons 1 may be braided into the sheath 2 so that they form loops. In a subsequent step, the loops are cut so that they form protruding ribbons 1. The protruding ribbons 1 are then dipped in a tub or passed along a spraying zone, so that each protruding ribbon is coated or impregnated with the desired material. After drying and optional subsequent treatment steps, the drag cable 3 is coiled with coated or impregnated fairing ribbons 1 around a drum, and is ready for distribution/sale. Thus, the invention according to the present invention does not involve any particularly labor-intensive or complicating process steps which would require large investments or restructuring/extension of existing production systems. This results in a considerably improved and attractive product that can be sold at an acceptable extra cost for the end user.

The ribbons 1 may also be coated before they are attached to the rope or cable 3. The coating is herein described as an adhesive, an impregnating agent and/or a plastic material. Plastic material is to be understood as indicating any suitable material forming a covering or penetrating coating, the coating being flexible and ductile, having adhesive properties, being resistant to mechanical and chemical wear as well as UV radiation. The material may comprise polymeric materials, rubber materials, resins, etc. When the fairing is made up of a compact, solid ribbon, the material must have properties which render the fairing sufficiently strong and durable.

Claims

C l a i m s

Sheath (2) for an elongated, load-bearing body (3), said sheath comprising several elongated sheath elements braided together around at least a portion of the elongated body, said sheath being equipped with a protruding fairing (1),

c h a r a c t e r i z e d i n that the protruding fairing (1) comprises or is coated or impregnated with a material which prevents the protruding fairing from linting.

Sheath according to claim 1, where the protruding fairing (1) is woven, braided or sawn into ribbon such that it does become linty.

Sheath according to claim 1, where the protruding fairing (1) is coated with a plastic material.

Sheath according to claim 1, where the protruding fairing (1) is impregnated with a fully or partially curing adhesive.

Sheath according to one of the preceding claims, where the protruding fairing (1) is coated or impregnated with a material, adhesive or substance containing particles, elements or other substances which provide each ribbon with longer service life or desired frictional properties.

Sheath according to claim 1, where the protruding fairing (1) comprises a compact, solid ri

Sheath according to claim 1, where the protruding fairing (1) comprises a film of the same material as in the sheath.