Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Patent
1993-03-24
1995-01-10
Corbin, David H.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
405158, 4051681, F16L 116
Patent
active
053801296
DESCRIPTION:
BRIEF SUMMARY
Method for laying tubular conduits
The invention relates to a method for laying a pipeline formed of joined rigid and flexible tubular conduits.
Rigid tubular conduits have the advantage of a relatively low linear cost. They have the disadvantage of being difficult to put into use. In particular, laying them is a long and costly operation. The laying of rigid tubular conduits is carried out using a floating support, in particular barges having low maneuverability. These barges only rarely comprise devices for dynamic positioning. They are therefore forbidden to enter certain areas comprising platforms for drilling or for developing oilfields. A method for laying such rigid tubular conduits is described for example in GB-A-1204715.
Flexible tubular conduits have a higher cost per meter. However, they are extremely quick to put into use. The applicant uses boats having dynamic positioning in order to lay them. These ships do not usually allow rigid tubular conduits to be handled.
The method according to the present invention uses the respective advantages of each type of conduit. The joining of flexible conduits and of rigid tubular conduits may be justified by the presence of an existing network of rigid tubular conduits or by the performance of which the devices for laying flexible conduits are capable.
According to the present invention, it is advantageous to use the equipment for laying rigid tubular conduits and in particular the barges for laying rigid tubular conduits, in order to lay a short length of flexible tubular conduit joined by one end to the terminal end of the rigid tubular conduit. The length of flexible tubular conduit is greater than the depth of the water. Thus, once the end of the rigid tubular conduit rests on the bottom of the water, the second end of the flexible tubular conduit is still available on the barge for laying the rigid tubular conduit. This end is, for example for a subsequent resumption of the laying, transhipped on board a second floating support such as a ship for laying flexible tubular conduits or abandoned on the bottom. The ship for laying flexible tubular conduits continues the laying of the flexible tubular conduit. It allows a quick and safe laying and in particular allows congested sites to be approached, in so far as it is, advantageously, equipped with a device for dynamic positioning.
In one variant of the method according to the present invention, devices which are compact and of low cost are used for carrying out the laying of the flexible tubular conduit from the barge for laying the rigid tubular conduits. Such an item of equipment comprises two pincers the opening and closing of which may be controlled; one pincer is fixed, one pincer is mobile. Such an item of equipment has the advantage of not cluttering the barge which is mainly intended for the laying of rigid tubular conduits. It has the disadvantage of being slow. However, in so far as it is only used to lay short length of the flexible tubular conduit, this device only slightly slows down the operations of laying the tubular conduits. However, it is of course understood that the use of the conventional tensioning means for laying flexible tubular conduits, for example of the type comprising a multi-caterpillar-tracked linear winch, is not beyond the scope of the present invention.
At the end of the laying of the rigid tubular conduit it is necessary to comply with the maximum mechanical stresses which such a conduit can withstand. For example, fixing means are attached to the end of the rigid tubular conduit. These fixing means comprise for example a flange. The fixing means enable the end of the rigid tubular conduit to be solidly fixed with the holding means intended to prevent the rigid tubular conduit from being subjected to bending of too small a radius of curvature. Steel cables for example are used.
The rigid tubular conduit is advantageously inclined for example at an angle between 10.degree. and 30.degree., typically 20.degree., at the end of the barge. A supporting device in the form o
REFERENCES:
patent: 4065822 (1978-01-01), Wilbourn
patent: 4573425 (1986-03-01), Pomonik et al.
Coutarel Alain
Espinasse Philippe
Maloberti Rene
Coflexip
Corbin David H.
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