Patent ID: 6454897
Filing Date: 2002-09-24
Classification: B29C,B32B,F16L

Abstract:
A process for manufacturing flexible pipe, wherein the flexible pipe comprises, from inside to outside, a flexible metal tube having helical winding turns helically wound to define spaces between the helical winding turns of the flexible metal tube and the flexible metal tube is an innermost element of the flexible pipe, an internal sealing sheath around the flexible metal tube wherein the material of the internal sealing sheath exhibits plastic flow when heated, an armoring ply wound around the internal sealing sheath, and an external sealing sheath around the armoring ply;the method including moving the flexible metal tube lengthwise from upstream to downstream past an extrusion head; extruding the internal sealing sheath onto the flexible metal tube at the extrusion head; and before the extruding, heating the flexible metal tube at a location upstream of the extrusion head to an elevated temperature which is below 100Â° C. and high enough to avoid contraction cavities in the internal sheath due to differential shrinkage of the material of the internal sealing sheath caused by sudden cooling of the internal surface of the internal sealing sheath on the flexible tube during extrusion and below a temperature at which the material of the internal sealing sheath would fill, by plastic flow, at least 95% of the volume of the spaces between the helical winding turns of the flexible metal tube for preserving the flexibility of the flexible pipe; applying an armoring ply wound around the internal sealing sheath; and applying an external sealing sheath around the armoring ply.