GB2220453A

GB2220453A - Pipe distribution system

Info

Publication number: GB2220453A
Application number: GB8814064A
Authority: GB
Inventors: E Lindsey Meadows; H E Andersen
Original assignee: HOULDER OFFSHORE ENGINEERING; NORTH SEA TERMINALS Ltd
Current assignee: HOULDER OFFSHORE ENGINEERING; NORTH SEA TERMINALS Ltd
Priority date: 1988-06-14
Filing date: 1988-06-14
Publication date: 1990-01-10
Anticipated expiration: 2008-06-14
Also published as: GB8814064D0; GB2220453B

Abstract

In a vessel mooring system, a mooring line has at least one portion which is a single rigid member, secured at its lower end at a table to a plurality of cables fanning out over the sea bed to anchoring points. The vessel is formed with a vertical hollow shaft, lined with a turret, which contains a second rigid member, connected to the top of the first rigid member by a swivel joint. Pipes leading to the vessel for example from oil sources on the sea bed enter the vessel through the second rigid member. The pipes are connected to separate conduits which extend axially of the turret which is stationary. The conduits are arranged in a line extending transversely to the turret axis. Each conduit has its own swivel joint. The outlets from the conduits are arranged at progressively higher levels along said line. With this arrangement, the connections on the vessel to the outlets can accommodate a near complete rotation of the vessel relative to the turret. <IMAGE>

Description

PIPE D ISTRIBUTION SYSTEM Vessels moored in the open sea should be able to move about their mooring position in order to align themselves with prevailing winds - this is known as weathervaning. In order that the vessel can change its alignment by rotation about this single portion, it has been proposed that the mooring line should have at least one portion which is single.

In one known mooring system, the single portion is a rigid member, secured at its lower end at a table to a plurality, such as eight, of cables fanning out over the sea bed to anchoring points. The vessel is formed with a vertical hollow shaft, lined with a turret, which contains a second rigid member, connected to the top of the first rigid member by a swivel joint. Pipes leading to the vessel for example from oil sources on the sea bed enter the vessel through the second rigid member. The turret remains stationary relative to the sea bed when the vessel rotates, and so some form of swivel connection must be provided between the pipes in the turret and the processing plant on the vessel.In one known arrangement, the pipes are connected to annular coaxial chambers in multiple swivel joint, but this is a very complex piece of equipment, and if anything goes wrong with it, flow in all pipes must be stopped.

According to the present invention, the pipes are connected to separate conduits which extend axially of the turret. The conduits are arranged in a line extending transversely to the turret axis. Each conduit has its own swivel joint. The outlets from the conduits are arranged at progressively higher levels along said line. With this arrangment, the connections on the vessel to the outlets can accommodate a near complete rotation of the vessel relative to the turret. When the limit is exceeded, the affected flow can be directed to another conduit, the connection broken and remade on the other side of the line of conduits, and the flow realigned. No interruption of the flow thus taking place.

An example of the invention will now be described with reference to accompanying drawings, in which Figure 1 is a vertical cross section through the turret of a vessel, and Figure 2 is a plan of the turret of Figure í.

The vessel 11 has a turret 12 mounted in a vertical hollow shaft 13 extending through the whole height of the hull. The turret is rotatable about the axis of the shaft and has radial bearings 14 at the top and bottom of its body and a vertical bearing 15 on an upper flange 16 which retains the turret and transfers the vertical loads, from both the mooring system and the pipes, to the vessel. In this embodiment the turret 12 is about 10 metres in diameter, to accommodate the mooring chain 17 and the desired number of pipes 18.

The turret is formed with a plurality of vertical passages which have flared lower ends to accommodate the change in direction of the member extending therefrom; one passage 21 is for a mooring chain which is secured in position at the top of the turret. The turret is formed with a locker 22 adjacent the passage 21 for storage of surplus chain. The lower end of the mooring chain is secured to a chain table, from which cables extend to a plurality of anchoring points on the sea bed. The other passages 23, of which only one is shown in Figure 1, contain the pipes 18 from the oil sources. The position of the turret remains independent of the direction in which the ship lies, the motorised turret being turned in the hull as the hull turns relative to the sea bed. The mooring chain and the pipes do not therefore twist or come into contact at any time.Because the pipes pass to processing stations on the hull of the vessel, some means has to be provided on the hull to prevent twisting of the pipes as the turret rotates relative to the hull.

Each pipe, or each group of up to three pipes, passes through a quick connect and disconnect (QCDC) joint 24 at the top of passge 23, and from there each pipe is connected through a manifold to a respective vertical conduit 32, the conduits 32 being supported on a mounting platform 29 in a line across a diameter of the turret. Each conduit 32 has a swivel joint 25 and a 90 degree bend 26 above the swivel joint, the outlets of the conduits being located on progressively higher levels so that they do interfere with adjacent outlets as they swivel.

Each outlet of the conduit is connected by a flexible conduit lying in a tray 28 on a level with its outlet, the tray having enough width to allow the flexible conduit to move across the width of the turret and to store enough slack flexible conduit to accommodate the change in distance from the tray to the outlet as the outlet moves with the rotation of the turret.

As can be seen from Figure 2, the individual QCDC units 24 are arranged mainly coaxially of the turret on a common circle, with one unit 24a arranged near the centre of the turret.

They are all spaced from the mooring chain passage by a minimum of 4m, the turret diameter being lOm.

When the turret 12 rotates sufficiently that a flexble conduit 27 starts to foul a vertical conduit of another flow channel, flow is diverted from that flexible conduit by closing a valve in the manifold, and then the flexible conduit 27 is disconnected from its outlet, is moved to the other side of the vertical conduit 32 it was fouling and is reconnected. A crane 31 is provided on the deck of the vessel to assist this transfer of flexible conduit 27. In this way fluid flow is stopped in only one flow channel at a time, and the total flow can be accommodated in all other flow channels while the reconnection is being made.

Claims

CLAYS:

1. A pipe connection system for a sea vessel comprising a turret for stationary mounting in the vessel a plurality of separate conduits extending vertically through the turret and arranged side by side in a horizontal line, a swivel front within each conduit, the upper outlets of the conduits being progressively higher along the line.

2. A pipe connection system substantially as herein described with reference to the accompanying drawings.