Patent ID: 6966344

Claim:
An underwater flexible pipe for limiting lateral buckling of tensile armor plies of the pipe, wherein, from outside the pipe inward the pipe comprises: an external sheath; a first upper retention layer; an upper, radially outward tensile armor ply wound in a long pitch helix, and the first retention layer being wound around the upper tensile armor ply; at least one second lower retention layer; at least one lower, radially inward tensile armor ply in a long pitch helix wherein a respective at least one second retention layer is wound around each of the lower tensile armor plies; and an internal sheath inward of the at least one lower tensile armor ply; wherein the first upper retention layer and the second lower retention layer have respective stiffnesses K 1 and K 2 selected so that the retention layers limit the swelling of the tensile armor plies underlying the retention layers and wherein the first retention layer stiffness K 1 differs from the second retention layer stiffness K 2 .