Buoys – rafts – and aquatic devices – Buoyancy providing attachment for pipe – log – or line
Reexamination Certificate
1999-08-13
2001-08-07
Morano, S. Joseph (Department: 3617)
Buoys, rafts, and aquatic devices
Buoyancy providing attachment for pipe, log, or line
C405S211000, C405S212000
Reexamination Certificate
active
06270387
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a buoyancy device and in particular to a buoyancy device adapted to be clamped around at least one longitudinal element, heavier than water, and designed to be mounted below water.
DESCRIPTION OF THE RELATED ART
Many different examples of buoyancy devices that are adapted to be clamped around oil or gas conduits leading to or from the sea bed, and to be mounted to electrical cables or similar elements previously known.
As examples of previously known technique in this field the following publications may be referred to.
In U.S. Pat. No. 3,729,756 a divided, shell-shaped flotation collar adapted to be clamped around a riser tube with associated additional tubes is disclosed. The flotation collar as a whole comprises an outer flotation member comprising a semicircular shell of fibre glass, and a central clamping means which may be separated and fastened around the longitudinal element by means of bolts, which element is to be affected by the desired buoyancy. The outer flotation members are fastened to V-straps which again are welded to the outer side of the clamping halves.
U.S. Pat. No. 4,477,207 also refers to a buoyancy assembly for mounting on a riser or a similar type including certain additional pipelines. Also, in this citation the buoyancy assembly is dividable in sections manufactured by fastening of these sections is a clamping device comprising a centrally arranged band with protruding flanges, which band should first of all be fastened around the riser. An outer belt or strap is arranged along the perimeter, tightly around the sections, retaining the same.
U.S. Pat. No. 4,176,986 refers to a plurality of buoyancy cans provided with valves. These cans are filled up by compressed gas and thereby rapidly transfer buoyancy to a riser around which the cans are clamped. These cans have the shape of hollow containers divided in two parts.
U.S. Pat. No. 3,957,112 refers to a buoyancy means in which a lot of stiff-walled tubes having a small diameter are arranged around the outer wall of a marine riser by special fastening means.
U.S. Pat. No. 4,422,801 refers to a buoyancy system for large underwater risers, where the system comprises a plurality of hollow canisters arranged after each other in a row. Air may be pumped into the canisters which are interconnected along the riser so that air filled into the lower canister successively may dill the canisters arranged higher up. This system comprising a series of interconnected canisters, is also divided in more sections around the riser.
U.S. Pat. No. 3,705,432 refers to a flotation assembly including semi-annular flotation collars, similar to those mentioned in U.S. Pat. No. 3,729,756. However, the clamping device is rather complicated and comprises a lot of minor, individual elements.
German DAS 15 06 724 refers to a pipe-shaped buoyancy device to be clamped around a riser. The buoyancy device is divided in two substantially identical halves, and is provided with outer clamping straps
14
. The feature protected in this publication is the design of the interface between the two halves in a sort of tongue and groove joint.
All the earlier known buoyancy members have to be exactly associated to a riser having a specific diameter. To have buoyancy members adapted for use together with different risers available, a large quantity of such buoyancy members designed for risers of different dimensions one's must be at disposal.
A accordingly, there is a need for buoyancy members which may be used for risers within a certain range of different diameters.
The earlier known buoyancy means are in addition assembled from many different and individual parts. When such prior art buoyancy devices are to be mounted to a riser, great care must be shown that none of the separate parts will go lost. Accordingly the mounting of the prior art buoyancy devices is difficult and time consuming, especially when the operation takes place below water.
Therefore there is a need for buoyancy devices which, even when assembled form many parts, have such a design that each single buoyancy device before mounting consists of one single continuous and integrated unit which is not easily or unintentionally separated in different parts.
A further disadvantage of previously known buoyancy devices is that they relatively easily may be moved along the riser, especially if the diameter of the same varies longitudinally. Accordingly it is also an object of the present invention to provide buoyancy devices which, when clamped around a riser or a similar longitudinal element, exert a considerable pressure under prestress conditions towards the outer wall of the riser, preferably in such a manner that this force may be adjusted during the mountion operation so that the clamping is secure even if the diameter of the riser varies a certain amount along its length.
Finally it should be mentioned that there is a need for cost-effective buoyancy devices which both are inexpensive during manufacturing ad they comprise a few parts which are simple to produce and also as they rapidly may be mounted to the riser at a desired location even if the diameter of the riser varies and ever when the complete riser or parts of the same is (are) situated below water. It should be pointed out that the mounting expenditures may be very high due to required mounting equipment, use of divers and possibly also use of rigs on the mounting site. All reductions in the mounting time for such buoyancy devices accordingly are of great importance both economically and of security reasons.
SUMMARY OF THE INVENTION
One object of the present invention, is to provide buoyancy members which may be used for risers within a certain range of different diameters.
A further object of the present invention is to provide buoyancy devices which, even when assembled from many parts, have such a design that each single buoyancy device before mounting consists of one single continuous and integrated unit which not easily and unintentionally may be separated in different parts.
Finally it should be mentioned that one object of the present invention is to provide cost-effective buoyancy devices which both are inexpensive during manufacturing as they comprise a few parts which are simple to produce and also as they rapidly may be mounted to the riser at a desired location even if the diameter of the riser varies and even when the complete riser or parts of the same is (are) situated below water. A buoyancy device adapted to be clamped around at least one longitudinal element, comprising at least one clamping portion for holding the at least one longitudinal element in said buoyancy device, said at least one clamping portion comprising at least one radial extension, said at least one radial extension comprising an inner clamping end and an outer fastening end at least one buoyancy portion for holding the at least one clamping portion; and at least one peripheral tensional element for slidably fastening onto the outer fastening end of the at least one radial extension, where tension in said at least one peripheral tensional element provides force for clamping the inner clamping end of the at least one radial extension onto the at least one longitudinal element.
All objects and advantages mentioned above are met by using buoyancy devices as defined in the claims below.
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ABB Off-Shore Technology AS
Cohen & Pontani, Lieberman & Pavane
Morano S. Joseph
Olson Lars A.
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