Pipes and tubular conduits – Flexible – Spirally wound material
Patent
1997-09-29
1999-08-10
Brinson, Patrick
Pipes and tubular conduits
Flexible
Spirally wound material
138134, 138135, 138129, F16L 1116, F16L 1108
Patent
active
059343354
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns flexible tubular pipes which generally include, from the interior towards the exterior: comprising a helically wound profiled member with the turns clipped together, for example a clipped tape or a clipped T-section or U-section wire; pressure resisting member made from a close pitch helically wound T-section, Z-section or U-section wire with turns clipped together, and so-called traction reinforcement layers, each traction layer being made by helically winding wires with a lay angle less than 55.degree.. In another variant, the set of reinforcements comprises layers with lay angles of 55.degree. or with the lay angles complementary from one layer to another, for example a layer at 50.degree. associated with a layer at 60.degree.; the set of reinforcements resists the hoop stress and the axial component of the internal pressure and the axial load due to the weight of the suspended pipe and exterior effects;
The pipe may further comprise one or more intermediate polymeric sheaths and/or helically wound plastics material layers.
One such flexible tubular pipe is shown in FIG. 1 and described in patents FR-A-2 619 193 "Flexible Stable 4 Nappes", FR-A-2 654 795 "Onde Interne" and in "Recommended Practice for Flexible Pipe-API Recommended Practice 17B (RP17B) First Edition Jun. 1, 1988".
Because of the structure of the internal flexible metal tube, there are interstices between the winding turns that allow said internal metal tube to flex.
Many solutions have been proposed for the industrial manufacture of the internal impervious sheath. There is a trend towards the use of a polymeric material that has a low permeability to liquids and to gases, which resists the high temperatures of the fluid conveyed and which is easy to work industrially, in particular by extrusion.
The polymeric materials that have these properties are certain semi-crystalline polymers. From these, we have selected those which should be resistant to live crude with no blistering or swelling.
Certain grades of polyamide II are routinely used (products sold by ELF Atochem under the trade name RILSAN), but although this material gives excellent results it cannot be used in many cases in the most severe applications because of its limited resistance to high temperatures and its sensitivity to the presence of water. Certain grades of poly(vinylidene fluoride) (PVDF) are used for the most demanding applications. However, and going against what has previously been thought, it has been found that PVDF is not resistant to blistering above a temperature in the order of 130.degree. to 150.degree.. Furthermore, like other semi-crystalline polymers exhibiting relatively great shrinkage on solidification, PVDF can be subject to the risk of incipient fractures in the area of the interstice between two consecutive turns of the internal metal tube.
Consideration is now being given to the use of flexible tubular pipes for submarine petroleum production installations subject to even more severe conditions, in particular temperatures above 130.degree. C., possibly exceeding 150.degree. C. and even reaching at least 180.degree. C. There is at present no satisfactory solution for such conditions.
U.S. Pat. No. 4,402,346 proposes to make the internal impervious sheath from fluroplastics materials including TEFZEL, TEFLON FEP and TEFLON PFA. It has been found that some grades of PTFE (TEFZEL from DUPONT) and of FEP (TEFLON FEP from DUPONT) can be used for the impervious sheaths of flexible tubular pipes, in particular because of their good extrudability and their resistance to high temperatures. However, it has become apparent that their resistance to blistering is insufficient at the very high temperatures with which the invention is concerned. Moreover, on the basis of the properties of PFA as they were then understood, it was logical to consider its use in the presence of petroleum at high temperatures. However, there is no mention in the above document of blistering or of the behaviour of PFA vis a vis live crude at high temperat
REFERENCES:
patent: 3687169 (1972-08-01), Reynard
patent: 4402346 (1983-09-01), Cheetham et al.
"Recommended Practice for Flexible Pipe", American Petroleum Institute, Jun. 1, 1988, pp. 1-37.
Brinson Patrick
Coflexip SA
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