Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Patent
1994-07-26
1996-03-26
Schoeppel, Roger J.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
405191, 166338, 166343, 166347, F16L 112
Patent
active
055015492
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a tool for the remote-controlled pulling, aligning and connecting of a subsea conduit to a subsea installation, said tool comprising a framework, a pulling wire having a pulling head which can be releasably attached to the end of the subsea conduit and aligning means which bring the ends of the conduit which are to be connected in line with one another.
The tool is designed for the remote-controlled fitting of a subsea conduit to an oil well, subsea production plant, or similar sea-floor installation. The conduit may consist of a single pipe, a plurality of pipes surrounded by a common sheath, or a plurality of individual pipes which end up in a common end piece. Usually an elevator and thread connection is used between the end of the conduit and the continuation thereof in the sea-floor installation, but this type of connection must not be considered as a limitation.
A previously known assembly procedure for laying a subsea conduit on the sea bed is as follows:
One end of the conduit is placed at a suitable distance from and in the correct orientation relative to the sea- floor installation. A pulling wire has at one end a pulling head which is attached to the end of the subsea conduit. The end of the subsea conduit and the sealing surfaces thereof and the system for the connection can moreover be protected by a sheath. The wire is brought to the installation vessel and is fed through the pulling tool which is on board the vessel. The tool is then lowered to the sea bed and is locked on to the sea-floor installation. In order to guide the tool during the running down and retrival operation, wires are extended between guide posts on the sea-floor installation and the installation vessel. The subsea conduit is pulled by means of the pulling wire by a winch which can be positioned on the vessel. In deep waters and when the conduits are long or of large dimensions, the resilience or elasticity in a long pulling wire may cause problems. In such cases, the winch can be placed on the tool, or, in order to save time, the winch on the vessel can be used until the forces become too great, and thereafter the last step of the pulling is carried out by a stronger but slower winch on the tool.
If the conduit consists of several interconnections, it must be oriented. This takes place in that the conduit is pulled through a funnel having a double slot which forces the conduit to turn around the axis of the funnel until the conduit is oriented correctly. The conduit must also be straigthened so that the angle between itself and the continuation thereof on the sea-floor installation is within the tolerance levels of the connection. In the case of small conduits, the pulling head can be placed eccentric relative to the centre line of the conduit, and thus the conduit can be pulled forward until it is in the correct position relative to the flange to which it is to be connected. Furthermore, the funnel and the pulling head can be designed with a limited clearing and sufficient length to force the conduit into the correct angle. The connection can be tightened whilst the conduit is held by the pulling wire, thereby carrying out the pulling and the connecting by the use of one tool only.
The forces and torques which occur during pulling and aligning increase greatly, however, as the diameter of the conduit increases. In the case-of conduits of large dimensions, an eccentric positioning of the pulling head will subject the structures to further forces and torques and result in unrealistically rough dimensions of the materials used in the pulling head and the tool.
Also in the case of flexible conduits, an eccentric positioning of the pulling head will cause great problems because the conduit will bend.
It would be possible to achieve a symmetric pull by using two pulling wires. This principle has been used for pulling flexible risers to floating platforms, but the use of two pulling wires has been considered too complicated for use on subsea installations.
In the case of conduits of large dimens
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Bakke Jens
Breda Joren
Caspersen Sverre
Kvaerner Energy A.S
Schoeppel Roger J.
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