Flexible pipe with internal gasproof undulating metal tube

Details Flexible pipe with internal gasproof undulating metal tube Flexible pipe with internal gasproof undulating metal tube

1998-08-04

1999-12-28

Kashnikow, Andres

Pipes and tubular conduits

Flexible

Spirally wound material

138135, 138134, F16L 1116, F16L 108, F16L 1120

Patent

active

060067888

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a long flexible pipe having an impermeable internal metal tube and more particularly to a flexible pipe including an internal corrugated metal tube which is, in particular, gas-impermeable.
The present invention also relates to a flexible pipe for transporting fluids at high pressure such as, for example, that used during operations for extracting crude oil from a subsea deposit. Such a pipe must, in particular, withstand the various forces to which it is subjected such as, for example, the internal and/or external pressures developed in and on the said flexible pipe, and must have a degree of flexibility along its longitudinal axis so that it can bend without risk of rupturing.
Under extreme service conditions such as, for example, in Arctic regions where very difficult climatic conditions prevail or else for transporting liquefied natural gas, it has been proposed to use either rigid steel pipes or flexible pipes which include an internal corrugated metal tube, as described in FR-A-2,458,022.
Other structures are also described in WO 96/17198 or GB-A-1,486,445.
The flexible pipe described in FR-A-2,458,022 comprises, from the inside to the outside: profiled wires, the winding pitch of which is in the opposite direction to the pitch of the corrugations of the said internal corrugated tube, this metal casing providing the bursting strength and called a pressure vault; and to the end cap effect due to the internal pressure of the pipe; and
In a variant, it is proposed to use as pressure vault a winding of a round wire which is housed in the troughs of the corrugations of the internal corrugated tube.
However, such a pipe has many drawbacks both with regard to the structure and from the behavior standpoint.
In order to reinforce the internal corrugated tube, it is internally lined with an overlapping flat and welded spiralled metal tape or with a smooth tape, the space between the corrugations of the internal tube and the tape being optionally filled with a filling material. Consequently, this is a substantially more rigid structure which must be wound onto a large-diameter drum and which is fragile during the unwinding and winding operations in manufacture. When the corrugated tube is not reinforced with the aforementioned tape, then any momentary elongation of the pipe, as occurs when it is under tension, may generate a permanent elongation of the internal tube sometimes leading to rupture. Finally, whatever the recommended pressure vault, there is a risk of ovalizing the internal tube.
Whatever the circumstances, the flexible pipe of the prior art is unable to withstand the very high external pressures which develop at great depths, of the order of several thousands of meters, and/or the very high internal pressures developed in the pipe during exploitation operations.
The object of the present invention is to remedy the aforementioned drawbacks and to provide a flexible pipe which not only is capable of withstanding pressures of several hundred bar exerted on the outside and/or on the inside of the pipe, but also of being able to be used at high temperatures and in an acid medium, i.e. capable of high performance in a corrosive medium, and of being suited for what those skilled in the art call "SOUR SERVICE".
The subject of the present invention is a flexible pipe of the type comprising, from the inside to the outside, an internal corrugated metal tube, a pressure vault obtained by winding at least one shaped wire around the said internal tube, a polymeric sleeve around the said pressure vault, at least one armoring ply for resistance to tensile loads and an impermeable external sleeve, the pressure vault having a helical corrugated inner surface comprising at least concave and rounded parts and convex rounded parts, the outer surface of the internal metal tube bearing in its concave rounded part on a convex part of the inner surface of the pressure vault and in its convex rounded part on a concave part of the inner surface of the pressure vau

REFERENCES:
patent: 2720221 (1955-10-01), Neilson
patent: 4344462 (1982-08-01), Aubert et al.
patent: 5813439 (1998-09-01), Herrero et al.
patent: 5934335 (1999-08-01), Hardy

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