Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Reexamination Certificate
1999-12-23
2001-07-31
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
C166S350000, C166S367000
Reexamination Certificate
active
06267537
ABSTRACT:
The invention relates to a riser bundle comprising a number of risers extending in a wave configuration from the bottom of a body of water up to a floating vessel or the like, the riser bundle along its length being provided with means giving different portions along the wave configuration different submerged weight and net buoyancy.
Risers extending between the sea bed and a vessel floating on the surface will not be able to run in a straight line because of the large vertical movements which the vessel has in waves. The risers therefore must be arranged in some geometry allowing the upper end to have large vertical and horizontal movements. During a period of 10-15 seconds the upper end, which is fastened to the vessel, will move approximately ±10 m both vertically and horizontally. In addition, the upper end of the riser during a longer time period will be able to move in the horizontal plane within a circle having a radius of about 10-20% of the ocean depth.
A typical geometry which is used to meet these requirements, is an essentially S-shaped “wave” configuration, as shown in
FIG. 1
(wherein the S-shape indeed is shown reversed). In order to cause a riser to float in this manner in the water, it is necessary to give different portions along the riser a different submerged weight and net buoyancy. Along the upper portion or ridge of the “wave” curve the riser will have a positive net buoyancy. This may be achieved in that the riser has a small weight or in that it is equipped with buoyancy bodies in this region. Common practice today is to fasten buoyancy bodies to the riser along this portion. When using several risers simultaneously, these are usually arranged separately in the water, so that each riser must be provided with respective separate buoyancy bodies. This entails that the installation of such risers will be a time-consuming and circumstantial process. In addition, the separate external buoyancy bodies entail that the risers will be subjected to larger wave forces, because of the extra volume of the buoyancy bodies.
It is an object of the invention to provide a riser bundle which is without external buoyancy bodies, so that reduced wave forces are obtained, and which has a structure enabling an economic and rational installation.
Another object of the invention is to provide a riser bundle enabling adjustment of the buoyancy/weight of the riser bundle while it is in operation.
The above-mentioned objects are achieved with a riser bundle of the introductorily stated type which, according to the invention, is characterised in that the risers are arranged around a centrally extending tube and are surrounded by a tubular outer casing, the central tube and the interspaces between the risers, between the central tube and the outer casing, along different portions of the configuration in operation are filled with materials of different density, for achieving at least one light portion of the configuration having a desired positive net buoyancy, and a heavy portion on each side of the light portion having a desired positive submerged weight.
The riser bundle according to the invention will have an approximately constant cross-section area along its whole length, and consequently no cross-sectional increasing buoyancy elements. The desired positive net buoyancy is achieved in that the weight of the riser bundle itself is low along the desired portion of the riser bundle, i.e. in the above-mentioned light portion. The remaining parts of the riser bundle, i.e. on both sides of the ridge (or a ridge) of the wave curve, in operation will have a positive submerged weight. This is achieved in that the riser bundle in operation will contain materials having a large density in said parts, i.e. in. the above-mentioned heavy portions.
REFERENCES:
patent: 3605398 (1971-09-01), Carlson et al.
patent: 4021589 (1977-05-01), Copley
patent: 4052862 (1977-10-01), Lamy
patent: 4110554 (1978-08-01), Moore et al.
patent: 4332509 (1982-06-01), Reynard et al.
patent: 4634314 (1987-01-01), Pierce
patent: 4963420 (1990-10-01), Jarrin et al.
patent: 5795102 (1998-08-01), Corbishley
patent: 169687B1 (1988-02-01), None
patent: 0200308A1 (1986-11-01), None
patent: 0424225A1 (1991-04-01), None
patent: 2297337 (1996-07-01), None
patent: 180650 (1997-10-01), None
patent: WO97/06341 (1997-02-01), None
Breivik Kare
Falch Sigurd
Semb Gunnar
Bagnell David
Banner & Witcoff , Ltd.
Den Norske Stats Oljeselskap A.S.
Lagman Frederick L.
LandOfFree
Riser bundle does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Riser bundle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Riser bundle will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484015