This application is a national stage application, filed under 35 U.S.C. § 371, of International Patent Application No. PCT/NO2018/050306, filed Dec. 7, 2018, which claims priority to Norwegian Patent Application No. 20171967, filed Dec. 8, 2017, both of which are incorporated by reference herein in their entirety.
The invention concerns a mooring system as set out by the preamble of claim 1.
There is a need for a mooring system suited for shallow waters which is simpler and easier to install than the present systems, while at the same time fulfills operational requirements.
In shallow waters, e.g. down to less than 20 metres, and where wind and waves are relatively benign and directional, the well-known turret option is too elaborate and unnecessary. Typical data may be:
A mooring system that keeps the vessel (e.g. a Floating Storage and Regasification Unit; FSRU) orientated with a fixed heading towards the dominating wave direction, and maintained on heading by stern holdback lines, is considered adequate. However, the mooring system must allow a cargo vessel, e.g. an LNG carrier (LNGC) to be moored alongside the FSRU during LNGC loading operations. A problem with known catenary mooring systems is that the mooring lines tend to interfere with large vessels (such as an LNGC) that intend to moor alongside the FSRU.
The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.
It is thus provided a mooring system, comprising a pair of first mooring elements configured at first ends for connection to a floating vessel; a pair of second mooring elements configured at first ends for connection to a seabed below a water surface; characterized by a restrictor member connected between said pair of first mooring lines' second ends.
In one embodiment, the restrictor member is connected between said pair of second mooring elements' second ends. The restrictor member may be an inelastic member and the pairs of first and second mooring elements are connected to the restrictor member at opposite ends of the restrictor member. The restrictor member has a length dimension between said ends that is less than or equal to the width of the vessel to which the mooring system is connected, whereby the a pair of first mooring lines are pulled together and will not interfere with other vessels moored alongside said vessel. The restrictor member may be a stiff member, such as a steel rod, pipe or bar, or one or more chains or ropes.
A mooring system may comprise a floating vessel, a mooring system according to the invention connected to the bow portion of the floating vessel; and a mooring system according to the invention connected to the stern portion of the floating vessel.
The invented mooring system, referred to as a Restricted Catenary Mooring (RCM) system is particularly suited for shallow water application in benign areas with directional waves (swell). The RCM system is an effective mooring system which together with holdback mooring lines act as a spread mooring system.
The invented mooring system contributes to holding the mooring lines together and away from side-by-side moored LNGC.
The invented mooring system shall not be limited to use on an FSRU, but may be used on other vessels, such as FPSO and FSO vessels, and other ships.
These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached schematic drawings, wherein:
The following description will use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, “upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.
In the illustrated embodiment, the ship 1 is moored via a bow mooring system 3 and a stern (hold-back) mooring system 4. The bow mooring system 3 and the stern mooring system 4 may in principle be similar (and thus generally be referred to as a “mooring system”).
The bow mooring system 3 comprises in the illustrated embodiment two upper mooring elements 31a, 31b. Each of the upper mooring elements is at one end connected to the ship's 1 bow portion in a manner which is well known in the art (e.g. to winches on the ship's deck). The upper mooring elements 31a, 31b may comprise wires, ropes, lines, chains, or any other flexible mooring element known in the art. In the embodiment illustrated in
Each upper mooring element 31a, 31b is at its other end connected to generally opposite ends of an elongate element 34 which in the following will be referred to as a mooring restrictor. Also connected to (and generally at opposite ends of) the mooring restrictor 34, are two lower mooring elements 35a, 35b. These lower mooring elements are connected between the mooring restrictor 34 and respective seabed anchors (not shown) and extend in a catenary fashion in the body of water. The mooring elements 35a, 35b may comprise wires, ropes, lines, chains, or any other flexible mooring element known in the art.
In the illustrated embodiment, each lower mooring element 35a, 35b comprises a first section 32a, 32b that may comprise synthetic fibre ropes (e.g. polyester) and a second section 33a, 33b that comprises chains and extend to the seabed anchors.
The stern mooring system 4 comprises in the illustrated embodiment two upper mooring elements 41a, 41b. Each of the upper mooring elements is at one end connected to the ship's 1 stern portion in a manner which is well known in the art (e.g. to winches on the ship's deck). The upper mooring elements 41a, 41b may comprise wires, ropes, lines, chains, or any other flexible mooring element known in the art. In the embodiment illustrated in
Each upper mooring element 41a, 41b is at its other end connected to generally opposite ends of an elongate element 44 which in the following will be referred to as a mooring restrictor. Also connected to (and generally at opposite ends of) the mooring restrictor 44, are two lower mooring elements 45a, 45b. These lower mooring elements are connected between the mooring restrictor 44 and respective seabed anchors (not shown) and extend in a catenary fashion in the body of water. The mooring elements 45a, 45b may comprise wires, ropes, lines, chains, or any other flexible mooring element known in the art.
In the illustrated embodiment, each lower mooring element 45a, 45b comprises a first section 42a, 42b that may comprise synthetic fibre ropes (e.g. polyester) and a second section 43a, 43b that comprises chains and extend to the seabed anchors.
The mooring restrictors 34, 44 may be made from a reinforced pipe structure with a pad eye structure at each end. The mooring lines are attached with H-links.
Referring to
Number | Date | Country | Kind |
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20171967 | Dec 2017 | NO | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NO2018/050306 | 12/7/2018 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2019/112444 | 6/13/2019 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5884576 | Wajnikonis | Mar 1999 | A |
6125560 | Beaumont | Oct 2000 | A |
6216628 | Poldervaart | Apr 2001 | B1 |
6435124 | Williams | Aug 2002 | B1 |
7516713 | Franta | Apr 2009 | B1 |
20080006196 | Poldervaart | Jan 2008 | A1 |
20200039610 | Liu | Feb 2020 | A1 |
20200361569 | Bech | Nov 2020 | A1 |
Number | Date | Country |
---|---|---|
1595045 | Aug 1981 | GB |
1595045 | Aug 1981 | GB |
2015041916 | Mar 2015 | WO |
WO-2015-212100 | Mar 2015 | WO |
Entry |
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PCT/NO2018/050306, International Search Report and Written Opinion, dated Feb. 28, 2019, 8 pages. |
NO20171967, Norwegian Search Report, dated Jun. 11, 2018, 2 pages. |
Number | Date | Country | |
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20200361569 A1 | Nov 2020 | US |