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International audience; This paper discusses the effect of porosity and hydrostatic pressure on diffusion kinetics and equilibrium water uptake in a semicrystalline fluoropolymer. Water sorption experiments at atmospheric pressure and under water pressures up to 250 MPa were carried out during 18 months at 40°C on reference and poroussamples. Porosity of samples was induced due to a cavitation process occurring at the highest triaxiality area of waisted and notched specimens during tensile tests.Water uptake was found to be very sensitive to porosity, showing an increase in samples with a high void fraction. On the other hand, water content decreased with increasing pressure suggesting a compaction of the porous space in which water can be stored. Two models describing this water uptake behaviour wereconsidered. The first is a classical model which assumes that sorption occurs only by diffusion following Fick’s law. Fick’s model was found to be in agreement with the experimental results. A “Langmuir-type” sorption model was also proposed to describe water uptake in porous samples, considering a two-phase watertransport mechanism: one portion of the absorbed water diffuses through the polymer matrix and the other portion is stored in voids. This model was implemented in a user subroutine using ABAQUSTM software and simulations were confronted to experimental sorption curves showing satisfactory agreements. The potential of the Langmuir-type sorption model resides on its availability to be coupled to a poro-mechanical model, in order to improve the understanding of coupling between the mechanical behaviour and water sorptionmechanism in a porous polymer.

The EN 3665 test is used to compare the filiform corrosion of aluminium substrates pretreated with Cr6+ and coated with different powder paints. The influence of the mechanical properties (tensile test and adhesion test), the chemistry (DSC and FTIR analysis) and the physical properties (oxygen and water permeations) of the paints on filiform corrosion is measured. The corrosion promoted filaments are studied morphologically and electrochemically. Their growth seems to be due to a combination between specific mechanical properties of the paints and their adherence on the pre-treated substrates. The influence of the paint thickness is also illustrated.

The complex melting behaviour and crystallization kinetics of polyhexamethylene terephthalate (PHT) and its copolymers with isophthalic acid (PHT col) have been explored using differential scanning calorimetry (DSC) and simultaneous time resolved synchrotron radiation wide angle and small angle X-ray scattering (WAXS and SAXS). Special attention has been paid to the presence of isophthalic chain defects and to crosslinking on the rate of crystallization. Kinetic data have been tentatively analyzed using Avrami parameters for the global crystallization and the Hoffman-Lauritzen equation for the separation of the factors governing spherulite growth rate.

Abstract Flexible pipes are extensively used for oil and gas development and thus transport the corrosive fluids of the production flow. These corrosive components (water, carbon dioxide or hydrogen sulfide) do not enter in direct contact with the structural steel layers of the pipe. However, they will diffuse through the pressure sheath and may induce corrosion phenomena on the structural layers. H2S gas could thus be present in the annulus. It is then necessary to use pressure vault and armour wires made of sour service steel grades instead of sweet service steel grades. In addition to the cost impact, the choice of these sour service steel grades with often lower mechanical performances has a direct influence on the overall design of the flexible pipe as they will result in structures with higher weight. Such a weight increase can be a disadvantage, for example in the case of ultra deep water applications. To prevent H2S from reaching the annulus of the pipe, a new thermoplastic material was developed. Components in the sheath material react with H2S and prevent it from diffusing and reaching the annulus. The use of this new ‘Anti-H2S’ layer will ensure a H2S free environment in the flexible pipe annulus. Considering that the steel layers will not be exposed to H2S, no degradation linked to the presence of H2S needs to be taken into account in the choice of the structural steel layers constitutive of the annulus. Consequently, the use of high steel grades layers with reduced thickness will be possible, reducing the cost and the weight of the flexible pipe. In addition, the ‘Anti-H2S’ layer makes it possible to propose flexible pipes for applications with high H2S contents, for which no solution could be proposed otherwise.

Due to H2 S pressure build-up in annulus, the use of sour service steel grades is required in some cases. For ultra deep water fields where the flexible pipe top tension is critical, high weight of the structural steel layers combined with lower mechanical properties (about 950MPa) of the sour grade materials is a disadvantage. The generic flexible pipe design avoids any direct contact between the bore environment (production fluids, injection fluids, etc) and the steel layers of the flexible pipe. However, diffusion of active components such as water, carbon dioxide, hydrogen sulfide, etc, through the thermoplastic sheaths could lead to corrosion exposure of metallic layers between the thermoplastic sheaths. In order to reduce the weight of the flexible pipe structure to reduce riser top tension, high strength grade steel layers (>1200MPa) can be used with reduced thickness, considering that the steel layers will not be exposed to H2 S coming from the bore fluid. This is now achievable even when H2 S is present in the bore by use of a new reactive polymer layer, which will ensure a H2 S free environment in the flexible pipe annulus. The new “Anti-H2 S” layer will chemically react with the H2 S, leading to a complete absence of H2 S exposure to steel layers during the service life of the pipe. In addition, the “Anti-H2 S” layer makes it possible to propose flexible pipes for applications with high H2 S content for which no acceptable solution would otherwise be found. This paper will present the theoretical background supporting the new Anti-H2 S layer concept, along with the qualification works carried out both at laboratory scale and on full flexible pipe structures. It will also focus on the design/calculation methodology applicable to this new sheath. Introduction of the “Anti-H2 S” layer results in that: - Flexible pipes can now be proposed for applications with high H2 S contents; - Sweet service high strength steel grades can be used in flexible pipe annulus even with the presence of H2 S into the bore of the pipe; - The weight of the flexible pipe is reduced.Copyright © 2011 by ASME

Placement of lipid residues in sanitary landfills are now prohibited by French legislation. The lipid residues used in this work were collected from a wastewater plant and restaurant traps. Aerobic degradation of these mixtures by a mixed population originated from an activated sludge was studied. First, the lipid matter underwent a saponification reaction, which solubilized partially and emulsified the substrate. An activated sludge was acclimated to saponified grease carbon source in a sequencing batch culture mode. Microbial activity was evaluated by the on line measurement of the CO2 production rate in the exit gas. At a feed concentration of 2 gHEM/1, the substrate degradation rate was measured as high as 1.6 gHEM/1 /h, the COD and HEM removals were 75% and 90%, respectively. Finally the average biomass yield was 0.3 gMLSS/gHEM.