Offshore drilling or production vessel with single length mooring line of high strength polyolefin fibers

Patent metadata

Field	Value
Publication number	US-9902466-B2
Application number	US-201314433445-A
Country	US
Kind code	B2
Filing date	Oct 9, 2013
Priority date	Oct 11, 2012
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

The invention relates to an offshore drilling or production vessel comprising a platform and a mooring system attached thereto, said mooring system comprising: i.) a support frame with a winch-drum mounted thereon; ii.) a mooring line for mooring said platform to the ocean floor, said mooring line comprising a first portion and a second portion; wherein said first portion is hauled on and paid off by said winch-drum; wherein said second portion is anchored to the ocean floor; characterized in that the mooring line is a single length mooring line comprising high strength polyolefin fibers; wherein the first portion of the mooring line has a first mass (M1) of polyolefin fibers per unit length and the second portion of the mooring line has a second mass (M2) of polyolefin fibers per unit length; wherein the ratio M1/M2 is greater than 1 and wherein said first portion extends continuously into said second portion through a tapered portion of the mooring line.

First claim

The invention claimed is:

1. An offshore drilling or production vessel comprising:
a platform; and
a mooring system attached to the platform, wherein the mooring system comprises:
(i) a support frame with a winch-drum mounted thereon;
(ii) a single length mooring line comprising high strength polyolefin fibers for mooring the platform to the ocean floor, the mooring line comprising a first portion which is hauled on and paid off by the winch-drum and a second portion which is anchored to the ocean floor, wherein
the first portion extends continuously into the second portion through a tapered portion of the mooring line; and wherein
the first portion of the mooring line has a first mass (M1) of polyolefin fibers per unit length and a specific strength (S1) and the second portion of the mooring line has a second mass (M2) of polyolefin fibers per unit length and a specific strength (S2), wherein the ratio M1/M2 is greater than 1 and the ratio S1/S2 is between 0.50 and 0.98.

2. The vessel of claim 1 , wherein, said first portion substantially extends at most 1 meter from the winch-drum.

3. The vessel of claim 1 , wherein said second portion substantially extends from at least 100 meters below the waterline.

4. The vessel of claim 1 , wherein the ratio M1/M2 is between 1.3 and 3.0.

5. The vessel of claim 1 , wherein the first portion of the mooring line has a specific strength of at least 1.3 kN/(g/m).

6. The vessel of claim 1 , wherein the second portion of the mooring line has a specific strength of at least 1.5 kN/(g/m).

7. The vessel of claim 1 , wherein the polyolefin fibers are fibers manufactured from homopolymers or copolymers of polypropylene or polyethylene.

8. The vessel of claim 1 , wherein the polyolefin fibers are ultrahigh molecular weight polyethylene (UHMWPE) fibers.

9. The vessel of claim 1 , wherein the polyolefin fibers have a tensile strength of at least 0.5 GPa.

10. The vessel of claim 1 wherein the polyolefin fibers have deniers in the range of from 0.5 to 20.

11. The vessel of claim 1 , wherein the polyolefin fibers are creep-optimized UHMWPE fibers obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational stress (ES), and a ratio

(

O
⁢

⁢

B
/
1000

⁢

⁢
C

E
⁢

⁢
S

)

between the number of olefinic branches per thousand carbon atoms (OB/1000C) and the elongational stress (ES) of at least 0.2, wherein said UHMWPE fibers when subjected to a load of 600 MPa at a temperature of 70° C., have a creep lifetime of at least 90 hours, preferably of at least 100 hours.

12. The vessel of claim 1 , wherein the winch-drum has a width to create helical windings, such that in a coiled state the winch-drum comprises several layers of the first portion of the mooring line, wherein the spacing between the windings of the rope is at least 0.5 times a diameter of the first portion of the mooring line.

13. A single length mooring line comprising high strength polyolefin fibers, wherein
the said single length mooring line includes a first portion and a second portion, the first portion extending continuously into the second portion through a tapered portion of the mooring line; and wherein
the first portion of the mooring line has a first mass (M1) of polyolefin fibers per unit length and a specific strength (S1) and the second portion of the mooring line has a second mass (M2) of polyolefin fibers per unit length and a specific strength (S2), wherein the ratio M1/M2 is greater than 1 and the ratio S1/S2 is between 0.5 and 0.98.

Assignees

• Dsm Ip Assets Bv

Inventors

• Vlasblom Martin Pieter
• Boesten Jorn
• Bosman Rigobert

Classifications

• E02D27/10

  Deep foundations · CPC title

• B63B35/4413

  Floating drilling platforms, e.g. carrying water-oil separating devices · CPC title

• B63B21/50 Primary

  Anchoring arrangements {or methods} for special vessels, e.g. for floating drilling platforms or dredgers · CPC title

• B63B75/00

  Building or assembling floating offshore structures, e.g. semi-submersible platforms, SPAR platforms or wind turbine platforms · CPC title

• D07B1/02

  Ropes built-up from fibrous or filamentary material, e.g. of vegetable origin, of animal origin, regenerated cellulose, plastics · CPC title