GB2299315A

GB2299315A - A Docking Chamber Device.

Info

Publication number: GB2299315A
Application number: GB9605139A
Authority: GB
Inventors: Arne Tonnessen
Original assignee: RASMUSSEN MANAGEMENT AS
Current assignee: RASMUSSEN MANAGEMENT AS
Priority date: 1995-03-30
Filing date: 1996-03-11
Publication date: 1996-10-02
Also published as: NO951226L; NO951226D0; NO308837B1; GB9605139D0

Abstract

A vessel docking chamber 2 for a buoy 3 comprises an encircling wall area for force transferring contact with a part of the outer surface of the buoy designed as a radially deformable annular area 8. In this way, one avoids the reaction force between the buoy and the docking chamber from being taken up as concentrated loads. With this structure, the reaction force between the buoy and the annular area will be distributed evenly over a large area (half the periphery of the chamber) and be transferred from the annular area to the bottom structure of the vessel evenly without any need for extra stuctural elements. The surrounding structure can be made very simple because the forces in the main will be transferred as shearing force from the annular area to the bottom structure of the vessel.

Description

A DOCKING CHAMBER~DEUICE The invention relates to a docking chamber device in a vessel for a buoy, said docking chamber comprising an encircling wall area for force transferring contact with a part of the outer surface of the buoy.

It is prior art to have a riser in the sea connected to a submerged buoy anchored to the seabed, and when a vessel has been manoeuvred into position above the buoy, to raise the buoy into a chamber in the vessel. The buoy is connected to the chamber and the riser is connected to a line system aboard the vessel. The chamber may be designed as a rotating member, a so-called turret in a vertical shaft in the vessel, but solutions are also known wherein the buoy is bipartite, thus having an outer part which can be coupled to the vessel, whilst the inner part is capable of rotating relative to the outer part. As a rule, the chamber is placed at a level on board the vessel such that it is entirely submerged. Measures are known which make it possible to carry out the hook-up of the buoy and of the riser in dry chambers.

The vessel is thus moored by means of the buoy anchored to the seabed, and the mooring force will therefore necessarily be transferred from the buoy to the vessel.

The present invention relates to improvements in connection with the said transfer of force. In today's practical embodiments the force transferring encircling wall area of the docking chamber is connected to the bottom structure of the vessel by means of bracing structural members, so that the reaction force between the buoy and the chamber is taken up as concentrated loads which are conducted into the bottom structure of the vessel by means of these bracing structural members. One of the specific objects of the invention is to make possible a more favourable and flexible adjustment between the buoy and the chamber, with favourable transfer of force in such a way that the radial load from the buoy will not pass directly into the bottom structure of the vessel, but will be taken up as an annular force having an even course over a large area.

According to the invention, a device is therefore proposed as mentioned by way of introduction, characterised in that the encircling wall area is designed as a radially deformable annular area.

Use of a radially deformable annular area of this kind in the chamber allows for the even transfer of the reaction force between the buoy and the annular area and further transfer of force from the annular area to the bottom structure of the vessel. The annular area will be able to adapt in a flexible manner to the buoy because there are no radial connections which hinder such deformation. Use of a flexible annular area means that the force between the buoy and the annular area will be distributed with an even course over half of the periphery thereof.

It is especially advantageous if the annular area according to the invention is formed by a ring member which is only fixed to the surrounding vessel structure along the two annular ends thereof.

The flexible attachment obtained in this manner results in the radial load from the buoy not passing directly down to the bottom structure of the ship, but being taken up as annular force which is redistributed as shearing force along the connection between the ring member and the bottom structure of the vessel.

According to the invention, it is of advantage if the annular area comprises a distinct and defined contact/force transferring belt.

It is of particular advantage if the annular area can be provided adjacent to the bottom plate of the vessel. The annular area can to advantage be a part of an annular body structure which comprises the inner and outer bottom of the vessel.

The invention will now be described in more detail with reference to the drawings, wherein: Fig. 1 is a pure schematic illustration of a buoy loading system where the invention is used; Fig. 2 shows a section of the interesting area of interaction between the buoy and the chamber according to the invention; Figs. 3x b, c show the principles of force absorption and distribution to the bottom plate of the vessel; Fig. 4 shows an isometric outline of the docking chamber in the vessel, and shows also how the horizontal component of the resultant mooring force is taken up along the annular area according to the invention; Figs. 5a,bc show examples of how the cross-section of the ring member can be designed in order to obtain the desired radial flexibility.

Fig. 1 illustrates the forepart of a vessel 1, wherein a conical docking chamber 2 is formed for a corresponding conically shaped buoy 3. The buoy 3 is anchored to the seabed 5 by means of mooring lines 6,7. One or more risers 4 extend from the seabed 5 up to the buoy 3.

The vessel 1 is anchored to the seabed 5 by means of the buoy 3 and the mooring cables 6,7 thereof, and the mooring force is thus transferred from the buoy 3 to the vessel 1.

Fig. 2 shows a section of the buoy positioned in the docking chamber 2 in the vessel 1.

The docking chamber 2 is designed at it lower part having a radially deformable annular area 8. This annular area is formed by a ring member 9 which forms a distinct and defined contact/force transferring belt relative to the buoy 3.

The ring member 9 at the two annular ends 10,11 thereof is welded into the surrounding vessel structure. In the embodiment illustrated in Fig. 2, the annular area or ring member 9 is a component of an annular body structure 12 which comprises the inner bottom 13 and the outer bottom 14 of the vessel. There are no reinforcements for the annular area 8 in the body structure.

In the illustrated exemplary embodiment, the buoy 3 is designed to be secured in the docking chamber 2, the mooring cables 6,7 and the riser 4 being connected to the buoy 3 by means of swivel connectors 15.

The annular area 8 is deformable radially and the reaction force between the buoy and the annular area and also the transfer of force from the ring member to the bottom structure of the vessel will therefore have an even course. The structure is such that the annular area can adapt flexibly to the buoy because there are no radial connections which prevent such a deformation. A flexible ring means that the force between the buoy and the ring or annular area is distributed with an even course over half of the periphery thereof. This is illustrated in Fig. 3b. Fig. 3a shows a section of the docking chamber with the new annular area 8, and in Fig. 3b the course of force over one quarter of the periphery is shown.

As illustrated in Fig. 3c, the radial load from the buoy will not pass directly to the bottom structure of the vessel, but will be taken up as an annular force which is redistributed as shearing force as indicated by the arrows, along the connection between the ring member and the bottom structure 11. S indicates the shearing force distribution for the ring-bottom plate.

By means of the invention, one avoids the reaction force between the buoy and the chamber being taken up as concentrated loads which must be conducted into the bottom structure using a more complex structure because the docking chamber or to be more precise the annular area thereof in the known embodiments has structural members connected directly to the loaded part of the annular area Fig. 4 is an isometric outline of the conical docking chamber in the vessel. In Fig. 4 it is shown how the horizontal component of the resultant mooring force F is taken up along theannulararea8.

Figs. 5 a,b, c illustrate different cross-sectional forms of the ring member 9.

The essence of the invention is that there is a radially deformable annular area. How this is provided in practice may vary. The specific design is determined by factors such as function requirements and production methods.

Claims

CLAIMS:

1. A docking chamber device in a vessel for a buoy, said docking chamber comprising a ring member for force transferring contact with a part of an outer surface of the buoy, wherein the ring member is only fixed in the hull of the vessel along an upper end which is radially flexible and a lower end which is radially constrained, said ring member along said lower end having a short radially flexible wall region.

2. A device as disclosed in claim 1, wherein the annular area comprises a distinctive and defined contact/force transferring belt.

3. A device as disclosed in one of the preceding claims, wherein the ring member is positioned adjacent to a bottom plate of the vessel.

4. A device as disclosed in one of the preceding claims, wherein the ring member forms a part of an annular body structure comprising an annular or polygonal wall structure, an inner bottom and an outer bottom of the vessel.

5. In, or for use in, a vessel, a docking chamber device for a buoy, which docking chamber includes a radially deformable annular area engageable with the buoy.

6. A docking chamber device for a buoy substantially as hereinbefore described with reference to Figure 2 or Figure 2 as modified by Figure 5a, b or c.

7. A vessel having a docking chamber device as claimed in any one of the preceding claims.