Underwater mooring rope

Abstract

The present invention relates to a mooring rope for use in subsea mooring, or a substantially synthetic rope thereof, said synthetic rope including a rope core and a layered shell arranged around the rope core, said the shell having a braided outer shell layer. The shell includes sub-surface buoyancy elements, suitable for use in a subsea environment, extending in radial direction between the rope core and the outer shell.

Claims

1. A subsea mooring rope, comprising: a substantially synthetic rope comprising a rope core and a layered shell arranged around the rope core, said layered shell having a braided outer shell layer, wherein the layered shell comprises sub-surface buoyancy elements extending radially between the rope core and the outer shell layer over a height, wherein the buoyancy elements are made of foam material with a hydraulic crush point greater than 30 bar, wherein the space formed between successive buoyancy elements is filled with air or water.

2. The subsea mooring rope according to claim 1, wherein the buoyancy elements are made of foam material with a compressive strength greater than 310 kPa, a tensile strength greater than 520 kPa, and a shear strength greater than 280 kPa.

3. The subsea mooring rope according to claim 2, wherein the distance between longitudinally consecutive buoyancy elements is greater than a quarter of the height.

4. The subsea mooring rope according to claim 1, wherein the buoyancy elements are made of foam material with a density greater than 180 kg/m.sup.3.

5. The subsea mooring rope according to claim 1, wherein the buoyancy elements are positioned longitudinally spaced apart and wherein the distance between longitudinally consecutive buoyancy elements is smaller than twice the height.

6. The subsea mooring rope according to claim 1, wherein the buoyancy elements are arranged tangentially spaced apart and wherein the distance between tangentially consecutive buoyancy elements is greater than a quarter of the height.

7. The subsea mooring rope according to claim 1, wherein the rope core comprises at least one subrope, wherein an inner shell layer is braided around the at least one subrope.

8. The subsea mooring rope according to claim 7, wherein the rope core further comprises a first filter cover made of filter material provided between the at least one subrope and the inner shell layer.

9. The subsea mooring rope according to claim 1, wherein the shell layer further comprises an element sheet extending between the rope core and the buoyancy elements for connecting and supporting the buoyancy elements; and/or comprises a second filter cover made of filter material extending between the buoyancy elements and the outer shell layer.

10. The subsea mooring rope according to claim 1, wherein the mooring rope is substantially cylindrical shaped over at least 75% of its length; and/or wherein the substantially synthetic rope is substantially cylindrical shaped.

11. The subsea mooring rope according to claim 1, wherein the substantially synthetic rope extends longitudinally over at least 10% of a length of the mooring rope.

12. A method for manufacturing the subsea mooring rope according to claim 1, comprising the steps of forming a substantially synthetic rope (1) by: a) providing a rope core; b) providing an elongated sheet, made of a fabric or a textile, having sub-surface buoyancy elements arranged spaced apart in the longitudinal direction of the elongated sheet; and c) winding the elongated sheath around the rope core to form a rope assembly; d) braiding an outer shell layer (26) around the rope assembly.

13. The subsea mooring rope according to claim 1, wherein the space between the rope core and the outer shell layer consists of spaced apart buoyancy elements of a single type of foam material with a hydraulic crush point greater than 30 bar.

14. A substantially synthetic rope, comprising a rope core and a layered shell arranged around the rope core, said layered shell having a braided outer shell layer, wherein the layered shell comprises sub-surface buoyancy elements extending radially between the rope core and the outer shell layer over a height, and wherein the buoyancy elements are made of foam material with a hydraulic crush point greater than 30 bar, wherein the space formed between successive buoyancy elements is filled with air or water.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. They are intended exclusively for illustrative purposes and not to restrict the inventive concept, which is defined by the appended claims.

(2) FIG. 1 shows in a cut-away view a simplified representation of a synthetic rope, for use in a mooring rope, according to an embodiment of the invention;

(3) FIG. 2 shows a cross-section through the mooring rope shown in FIG. 1.

(4) Other alternatives and equivalent embodiments of the present invention are conceivable within the idea of the invention, as will be clear to the person skilled in the art. The scope of the invention is limited only by the appended claims.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.

(6) Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein.

(7) Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

(8) Furthermore, the various embodiments, although referred to as “preferred” are to be construed as exemplary manners in which the invention may be implemented rather than as limiting the scope of the invention.

(9) The term “comprising”, used in the claims, should not be interpreted as being restricted to the elements or steps listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising A and B” should not be limited to devices consisting only of components A and B, rather with respect to the present invention, the only enumerated components of the device are A and B, and further the claim should be interpreted as including equivalents of those components.

(10) In a preferred embodiment of a mooring rope according to the present invention, a synthetic rope 1, as shown in FIG. 1, is provided with a loop or eye on at least one end. Such eyes are known from the prior art and are not described further here.

(11) The synthetic rope 1 which forms part of this preferred embodiment comprises in a radial direction R, as shown in FIG. 2, a rope core 10, a shell 20 with an inner shell layer 21, an intermediate shell layer 22 and an outer shell layer 26.

(12) The rope core 10 is made up of at least one subrope 11 which is wound in a first filter cover 12 consisting of a 6-fold layer of a filter material. The at least one rope 11 can be designed as a 3, 4 or 6-strand twisted rope or as 8 or 12-strand braided rope, or double braided rope. In a specific embodiment, the rope core 10 can be composed of a bundle of subropes 11 which are wound in the first filter lining 12. These subropes can each be formed as 3, 4 or 6-strand twisted ropes or as 8 or 12-strand braided ropes. This rope core 10 defines a longitudinal direction L, the radial direction R and a tangential direction T of the synthetic rope. Several strands are braided around the rope core 10 to form a continuously seamless inner shell layer 20. The inner rope structure, i.e. the rope core 10 and the inner shell layer 21, are wound in an intermediate shell layer 22 constructed from a sheeth 23 with floating elements 24 and a second filter cover 25 consisting of a single or multiple layer of a filter material. Several strands are braided around the intermediate shell layer 22 to form a continuously seamless outer shell layer 26. Preferably, this synthetic rope 1 is made from polyester, but it can equally well be made from another synthetic or from a combination of different synthetics.

(13) The filter covers 12, 25 prevent sand grains or other abrasive particles larger than 5 μm from falling between the strands, even when the rope 1 lies at a great depth on the bottom of the sea. Water can pass through the filter coating so that this filter coating does not crack under the influence of hydrostatic pressure. The filter material can be, for example, a non-woven fabric or a geo-textile, or other suitable material insofar as it has the appropriate permeability and filter effect.

(14) The filter covers 12, 25 consisting of a multiple layer of a filter material can be formed by one strip of overlapping wound filter material or by a plurality of strips of themselves little to non-overlapping wound filter material, the windings of the plurality of strips being shifted in the longitudinal direction. The strips can for instance be wound helically. The floating elements 24 are suitable for underwater purposes. These underwater floating elements must withstand very high water pressure, and consequently have a high compressive strength, so that they prevent distortion in underwater application. In underwater application, the buoyancy elements 24 provide buoyancy.

(15) Preferably, the floating elements 24 are made of a foam material with a closed cell structure and a hydraulic compressive strength, hydraulic crush point, greater than 30 bar.