Hydraulic and earth engineering – Marine structure or fabrication thereof – Structure protection
Patent
1996-10-10
1998-09-22
Graysay, Tamara L.
Hydraulic and earth engineering
Marine structure or fabrication thereof
Structure protection
405204, 166356, E21B 33037
Patent
active
058105158
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a protective means for a device which is installed on the sea bed, and which has an upper section which projects up therefrom, wherein the protective means is arranged to be lowered from a vessel down to the device, and comprises a central section and elongated elements which are linked with the central section and arranged to extend away from it and slantingly down to the sea bed when the protective means is protecting the device.
Within the field of oil production at sea, it is known that devices can be installed on the sea bed, e.g. wellhead Christmas trees, manifolds, etc. The upper section of such a device can be located 5-6 meters above the sea bed, and pipes can extend from the device down to the sea bed and continue away from it.
Such devices can be affected and damaged by objects which are towed by ships, e.g. objects which are used in connection with oil production, but also objects which are not used in this connection, such as trawl bags and the like.
For protection of a device of this type on the sea bed it is disclosed, e.g. in GB 2 226 352 and EP 0 411 967 that there can be provided outside the device a separate framework substantially in the form of a truncated pyramid, and which has an upper central section, e.g. in the form of the upper, small end surface of the truncated pyramid, and elongated elements which can extend along, e.g., the lateral edges of the pyramid down to a lower framework section in the form of the large end surface of the pyramid, the framework's elements hereby covering and protecting the device inside. When, e.g., a trawl bag is towed and comes into contact with such a frame, the trawl will merely slide over it without the risk of becoming entangled in protruding components of the device. Damage to both the device and the trawl are thereby prevented.
An auxiliary craft is used to mount the framework. The framework takes up a great deal of space on board the vessel, and since the large lower end surface of the framework is larger than the moon pool with which such ships are provided, and through which other equipment such as diving bells etc. can be lowered, the framework has to be lowered along the outside of the ship, which is a cumbersome process.
In EP 0 139 438 it is further disclosed that elongated elements of a protective means can be linked with a carrier part of the protective means, thus enabling the elements to be tilted from a position in which they extend approximately vertically, to a position in which they extend slantingly downwards and away from the upper section of the carrier part. This entire structure is so large that it has to be assembled below the device whereby the structure is lowered to the sea bed. Since the known protective means are intended to be secured to the sea bed by means of piles, but otherwise are self-supporting, they are large and heavy.
The object of the invention is to provide a means of the type mentioned in the introduction which is not encumbered by the above-mentioned disadvantages.
The invention will now be described in more detail with reference to the drawing which schematically illustrates two embodiments of a structure according to the invention.
FIG. 1 is a perspective view of a first embodiment of a means according to the invention, this structure being suspended in a hoisting line above a device which is permanently installed on the sea bed.
FIG. 2 is a perspective view of the structure illustrated in FIG. 1, with some of its legs pivoted into a position, wherein they project into the sea bed.
FIG. 3 is a section along the line III-III in FIG. 2
FIG. 4 is a perspective view of a second embodiment of the structure according to the invention.
As illustrated in FIG. 1 there projects up from the sea bed a pipe 1 which is permanently connected to the sea bed 11. To the upper end of the pipe there is attached a manifold 2, from which pipelines 3 extend substantially radially. Closest to the manifold 2 each pipe has a first pipeline section 4 which extends substantially horizontally in relation t
REFERENCES:
patent: 4273472 (1981-06-01), Piazza et al.
patent: 4519727 (1985-05-01), Mitchell et al.
patent: 4558973 (1985-12-01), Blandford
patent: 5176471 (1993-01-01), Frafjord et al.
Fredriksen Kaj Hugo
Inderberg Olav
Graysay Tamara L.
Kongsberg Offshore a.s
Lagman Frederick L.
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