GB1582468A - Mooring arrangement for a floating body - Google Patents

Description

(54) A MOORING ARRANGEMENT FOR A FLOATING BODY (71) I, JENS M. SLOTNAES, a Noiwegian Subject, of 2350 Nes, Hedmark, Norway, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the, following statement: The present invention relates to a mooring arrangement for a floating body, which may be in the form of a floating harbour installation of horse shoe shape, or a floating quay installation which may be made in a particular shape or may be a re-constructed tank vessel. In all cases the floating body may be equipped to carry out a wide range of operations during recovery of oil or gas from the bottom of the sea in which it is desired to moor the floating body.Such operations may exclude exploration of the sea bottom, drilling, pumping, storing or shipment of oil or gas, during which it is desired that the floating body be subjected as little as possible to the effects of wind, weather, waves and/or currents.

For the purpose of achieving this result, a series of structures have been suggested, in which the characterising features have resided in the shape of the floating body proper, or the arrangement of the mooring means. Thus, previously known floating bodies have been shaped approximately like a horse shoe having a mooring means arranged in the portion interconnecting the two legs of the horse shoe. Reference is particularly made to the vessel shown and described in U.S.

patent specification No. 2.699.321, according to which a horse shoe shaped vessel is moored by means of a vertical column which is passed through a well in the bow portion of the vessel and secured to the sea bottom, the connection between the column and the vessel being such that the vessel can automatically head into the wind, so that the water is always calm inside the horse shoe.

Here the column is secured to the sea bottom and guy cables are arranged between points on the column and anchor members spaced from the column axis. Such an arrangement ensures that the vessel will head into the wind, but as the column is secured to the sea bottom, the total installation is rigid, with considerable consequential stresses being set up. Also, the stay arrangement requires long lengths of chains or wires extending in all directions from the column, thereby occupying a great area of the sea bottom.

The present invention consists in an arrangement for the mooring of a floating body, comprising a column which passes through a vertical passage in the floating body and is held relatively to the water bottom at its lower end through a universal joint, and at least one wire stay which is connected to the lower end of the column, which extends outwardly and away from the column, and is connected to the floating body at a point which is at a substantial horizontal distance from the axis of the column.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figures 1 and 2 illustrate, in plan and side views, respectively, one embodiment of mooring arrangement according to the invention, applied to a vessel of ordinary design, and Figures 3 and 4 illustrate how a mooring arrangement may be applied to a floating "harbour" of V or U design.

In all figures, the same numerals are used in respect of parts which correspond to each other, in order to simplify the description.

In the drawings, a sea bottom 1 supports a bottom member 2 which is placed thereon at a suitable location, the member 2 being made in a suitable manner for use with the floating body to be moored. Thus, the member 2 may be in the form of individual storage tanks. As shown, the member may be made with a central space 3 which may be adapted to accommodate equipment-for exploration of or drilling in the sea bottom.

The space 3 is closed on top and the cover 5 is formed as a thrust bearing for the lower end of a column 4 and, possibly, adapted for the passage of conduits (not shown), which are passed upwardly through the column 4, as well as equipment, for example, for drilling and/or production. For the purpose of supporting the column 4, the lower end of the column has a part-spherical surface 6 from which extends a central gudgeon 7 which passes through the cover 5, the latter being formed with a corresponding part-spherical bearing surface. The cover 5 and, possibly, the gudgeon 7 is made of an elastic material, so that the column 4 may adopt an angular position relative to a vertical line through the center of the spherical bearing. This arrangement thus provides a universal joint between the column and the sea bottom, via the bottom member 2.

For the purpose of obtaining the required bearing pressure between the lower and of the column and the bottom member 2 and, possibly, adjustment of such pressure, the column may be divided into sections of fluid tight floors or bulkheads (not shown) so that a plurality of individual tanks are obtained, which may be filled with ballast liquid according to requirement, at the same time as the bottom member underneath the spherical bearing may be made hollow, and so that the pressure in such hollow may be adjustable by means of suitable conduits passed through the column from suitable pressure sources in the floating body. The sectionising of the column may also be utilised to provide the column with a certain buoyancy when the floating body is to be moved from one location to another.

In figures 1 and 2 of the drawings, a floating body 8 is shown in the form of an ordinary tank vessel which, in its forwards part is provided with a vertical passage or well 9 adapted to receive the column 4 by the use of suitable bearing means 10 permitting both vertical sliding movements and rotational movements of the column 4 and the body 8 relative to each other. The construction of such means are not shown and described in detail, as such means are already well known per se. In the drawings, the passage 9 is shown as being located within the floating body 8. Alternatively, the arrangement may be made so that the passage is located in a structure extending forwardly from the body 8, as, for example, in the arrangement shown in the U.S. patent specification No. 3.335.690.

The floating body 8 is provided with a propeller -1-1, a rudder 12 and bow thruster 13, for possible assistance in maintaining a weathervane position of the body relative to the vertical axis of the column 4.

From the foot of the column 4, wires 14 and 15 are shown which, respectively, extend to points 16 and 17, horizontally spaced from each other on board the body 8. The points 16 and 17 are positioned at a substantial horizontal distance from the axis of the column 4, so that the wires 14, 15 form a large included angle with the axis. The connection between the column foot and the wires 14 and 15 is such that rotational movements of the body about the axis of the column do not influence the location of the securing points of the wires, such for example by securing the wires through a ring member which may perform a rotational movement about the column.Thus, by means of the wires 14 and 15, the column 4 and the body 8 proper, a number of triangular connections are established between the body 8 and the bottom member 2, with the result that the strains in the bearing means 10 due to wind and/or current and/or variations in the level of the body 8 relative to the column 4, are very small. As the body is swinging freely about the axis of the column, it is always adjusting itself so that the resultant of the wind and current forces will act from the bow in the fore-and-aft direction, and tend to cause the body to sag in the aft direction, so that the wires 14, 15 are tightened and counteract such sagging, thereby forcing the body in the forward direction so that the column maintains its substantially vertical position.

Thus, through the co-operation between the bearing means 10 between the column 4 and the floating body 8; the wire stays 14, 15 which extend so that they form respective angles with a vertical plane through the fore and aft line of the floating body; and the spherical universal joint at the column foot, a dynamic elastic connection is obtained between the floating body 8 and the sea bottom 1, so that the floating body may always head wind and current and stay relatively calm in waves.The floating body may adjust itself along the length of the column according to its own buoyancy, and the spherical joint between the column foot and the sea bottom will permit the floating body always to adopt a horizontal position, without subjecting the connection between the floating body and the column to such mechanical strains which might lead to wedge effects or damages, as a result of the system of triangular connections provided by the spherical joint, the bearing means 10 and the oblique wire stays 14, 15. In this arrangement, the forces to which the floating body is subjected in the water are transferred to the secured bottom member 2 through the wire stays, so that the column does not need any ordinary staying, but nevertheless maintains a substantially vertical position.

The arrangement shown in Figs. 3 and 4 is, in principle, the same as that shown in Figs.

1 and 2, the floating body being however in the form of a V-shaped harbour 20 having a bow portion 2-1 which receives the well 9 and having two legs 22 and 23 which between them form a harbour basin 24 adapted to receive vessels which will be well protected between the legs 22 and 23 when the body 20 is swinging about the vertical axis of the column 4. Also the body 20 is provided with at least one bow thruster 13, and with two obliquely directed aft propellers 25 and 26.

The points 16 and 17 are here located at the aft ends of the legs 22 and 23 so that the distance between them, when seen from above is greater than in the arrangement shown in Figs. 1 and 2, with the result that the sideways staying effect of the wires 14 and 15 is increased.

The above described embodiments of mooring arrangement are not unduly space consuming and incorporate a simple elastic connection between the column and the floating body.

The bodies 8 and 20 may, in the ordinary manner, be provided with storage tanks for oil and/or gas, and accommodations for crew and stores, and the column 4 may be extended upwardly by a tower for use in drilling operations.

WHAT I CLAIM IS: 1. An arrangement for the mooring of a floating body, comprising a column which passes through a vertical passage in the floating body and is held relatively to the water bottom at its lower end through a universal joint, and at least one wire stay which is connected to the lower end of the column, which extends outwardly and away from the column, and which is connected to the floating body at a point which is at a substantial horizontal distance from the axis of the column.

2. An arrangement as claimed in claim 1, including at least one pair of wire stays, the individual stays of a pair of stays being connected to the floating body at points which are spaced horizontally from each other.

3. An arrangement for mooring a floating body, constructed substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

4. An arrangement for mooring a floating body, constructed substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. column 4. Also the body 20 is provided with at least one bow thruster 13, and with two obliquely directed aft propellers 25 and 26. The points 16 and 17 are here located at the aft ends of the legs 22 and 23 so that the distance between them, when seen from above is greater than in the arrangement shown in Figs. 1 and 2, with the result that the sideways staying effect of the wires 14 and 15 is increased. The above described embodiments of mooring arrangement are not unduly space consuming and incorporate a simple elastic connection between the column and the floating body. The bodies 8 and 20 may, in the ordinary manner, be provided with storage tanks for oil and/or gas, and accommodations for crew and stores, and the column 4 may be extended upwardly by a tower for use in drilling operations. WHAT I CLAIM IS:

1. An arrangement for the mooring of a floating body, comprising a column which passes through a vertical passage in the floating body and is held relatively to the water bottom at its lower end through a universal joint, and at least one wire stay which is connected to the lower end of the column, which extends outwardly and away from the column, and which is connected to the floating body at a point which is at a substantial horizontal distance from the axis of the column.

2. An arrangement as claimed in claim 1, including at least one pair of wire stays, the individual stays of a pair of stays being connected to the floating body at points which are spaced horizontally from each other.

3. An arrangement for mooring a floating body, constructed substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

4. An arrangement for mooring a floating body, constructed substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.