Abstract

Flexible pipe polymer pressure sheath is made either of polyolefin materials, polyamides or polyvinylidene fluoride. Each of these three polymer families is characterized by its own advantages and limitations. Polyolefins, particularly polyethylene (PE) and crosslinked polyethylene (XLPE), and polyamides have demonstrated their excellent behavior for containment layer in flexible pipe applications because of a good combination of properties. However the use of polyolefins materials is limited in pressure as they are subjected to blistering and the use of Polyamides is limited in temperature as they are subjected to hydrolysis. When these two polymer families cannot be used because of high pressure and/or high temperature, high grade (and considerably higher cost) Polyvinylidene Fluoride (PVDF) is considered.

For several years, Technip has been dedicated to the development and qualification of a new robust and cost-effective polymer material for flexible pipe pressure sheath. Its domain of temperature and pressure combines the high temperature of current crosslinked polyolefin materials and the high pressure of polyamides. One of the characteristics of this new material is its intrinsic long term stability towards hydrolysis and chemical aggression.

A full qualification program was carried out for this new polymer material. This program includes full polymer characterizations according to API17J [11], industrial extrusion qualification on production lines, mid-scale tests to qualify in temperature the sealing mechanism in the end-fittings and full-scale tests to validate the behavior of this new material during manufacturing, installation phases and during service life.

This new polymer material offers a real step change in the design of flexible pipes for the transport of oil, gas, water and mixtures thereof.

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