Pipes and tubular conduits – Combined – With end structure
Patent
1997-08-25
2000-02-01
Morris, Lesley D.
Pipes and tubular conduits
Combined
With end structure
138104, F16L 5500, B31C 500
Patent
active
060191376
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the field of flexible pipes for conveying hydrocarbons, and particularly but not exclusively to the field of flexible pipes for conveying hot hydrocarbons (typically at a temperature greater than 80.degree. C.) such as those used for raising deposit crudes from offshore wellheads to the surface, in particular to offshore oil platforms.
BACKGROUND OF THE INVENTION
A flexible pipe is constituted by a hose or a plurality of interconnected hoses, with the or each hose being fitted at its end with connection endpieces.
In conventional manner, a hose comprises from the center towards the outside: inner carcass, which is typically constituted by helically winding an interlocking section member, e.g. a steel strip, and provided at each end with an endpiece that is also known as a stop ring; therein and providing an outer surface that is substantially cylindrical and uniform, the polymer layer also being referred to as a sacrificial sublayer; sacrificial sublayer, with the purpose of the sacrificial layer being to provide the sealing barrier with a base surface that is substantially uniform; internal pressure and from traction, this armoring typically comprising crossed armoring sheets of helically wound steel wires; and
Optionally, the hose may also include, between the sealing barrier and the armoring sheets, a polymer layer referred to as an anti-creep layer that covers said sealing barrier and that serves to prevent it creeping into the gaps of the armoring sheets.
The hose must be fixed to each connection endpiece in such a manner as to ensure both continuity of the sealing of the flexible pipe, and as to ensure that traction forces due to the bottom effect are conveyed. These forces are taken up entirely by the armoring sheets in conventional manner and as described below.
It is known to provide sealing between the endpiece and the sealing barrier by means of a sealing gasket constituted by a metal bush having a substantially conical outer surface and threaded and crimped onto the sealing barrier. The metal bush also holds the sealing barrier axially in the connection endpiece, by opposing any residual axial stresses due to the method by which the hose is manufactured. The sealing barrier is clamped between the metal bush and the inner carcass, which carcass has sufficient mechanical strength to withstand crimping of the metal bush.
Unfortunately, that known technique does not provide entire satisfaction since it has been observed in some cases that sealing is lost due to a drop in the crimping exerted by the metal bush, and the Applicant attributes this to sweating out of plasticizing agents contained in the material constituting the sealing barrier.
An increase in the crimping ratio of the bush, where crimping ratio is defined as the ratio of the penetration depth of the metal bush over the combined thickness of the sealing barrier plus the sacrificial sublayer prior to crimping, does not make it possible in satisfactory manner to obtain long-lasting sealing since an excessive crimping ratio (greater than 60%) increases the risk of the sealing barrier tearing.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to remedy the above drawbacks by providing a novel assembly between a connection endpiece and a hose for conveying hydrocarbons, the hose being of the type comprising an inner carcass, a sacrificial sublayer, and a sealing barrier.
A particular object of the invention is to provide sealing in long-lasting manner between the hose and the connection endpiece.
The invention achieves this by the fact that the endpiece includes a retaining ring secured to the inner carcass, and locking means opposing axial displacement of the retaining ring in the direction for disassembling the hose from the endpiece.
The invention is based on the observation that the sweating out of plasticizing agents from the sealing barrier is not the only cause of a reduction in the clamping exerted by the metal sealing bush.
The Applicant has observed, unexpectedly, that the sac
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patent: 4143892 (1979-03-01), Murphy et al.
patent: 4275769 (1981-06-01), Cooke
patent: 4366842 (1983-01-01), Peavy et al.
patent: 4567916 (1986-02-01), Antal et al.
patent: 4895185 (1990-01-01), Champleboux et al.
patent: 5413147 (1995-05-01), Moreiras et al.
patent: 5608963 (1997-03-01), Lefere
Buon Eric
Secher Philippe
Coflexip
Huy Davis
Morris Lesley D.
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