| 1. |
- Benoit, G., et al.
(författare)
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Bare Field Joint for Subsea Pipelines, a Possible Alternative?
- 2018
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United States; 15 April 2018 through 19 April 2018. - : National Assoc. of Corrosion Engineers International. - 9781510864405
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Konferensbidrag (refereegranskat)abstract
- In the present context of oil price down turn and enhanced competitiveness, cost saving becomes more important than ever. As part of cost reduction solutions in offshore projects, it may be envisaged to leave field joints bare on subsea pipelines instead of applying a field anticorrosion coating after welding of the joints on board the laying vessels. This approach would need to be applied to specific cases, where it would lead to reduction of cycle time and consequently laying rate improvement during offshore installation campaigns when field joint coating activities are on the critical path, like with pipeline J-laying method. Although cathodic protection is an efficient, reliable and field proven method for seawater corrosion prevention on steel exposed areas of subsea coated pipelines, a quantitative assessment of the long term behavior of the pipeline coating at the transition zone with the bare field joint is recommended in order to support such a radical change in the pipeline external corrosion protection philosophy. Therefore, a bespoke experimental setup was designed to simulate bare field joint configuration under cathodic protection over a long term exposure in seawater together with long term cathodic disbondment tests for comparative purpose. The bespoke experimental test was performed at full scale on 3LPE coated pipe section with a field joint area left bare and protected by galvanic anodes. The pipe was immersed in a vessel containing renewed seawater and half-buried in mud to reproduce actual pipelines exposure on seabed. It was heated also with an internal fluid at 65°C to simulate actual operating conditions. Long term cathodic disbondment tests were performed on 3LPE coated pipe samples with internal heating of the samples at 23°C and at 65°C. Reference samples without CP were also exposed to the same conditions. The two experimental works were conducted during 12 months. For each of the tests above, a visual assessment was performed at regular intervals together with a quantitative assessment of the disbonded area (removal and recording of disbonded coating area). With these tests, it was possible to characterize the influence, over the time (up to one year) of the temperature over the normalized cathodic disbondment test results. The effect of the cathodic protection was also evaluated. For the full scale test evaluation and characterization, comparison was made between the disbonded coating length in the mud and the seawater exposure conditions. Correlation between cathodic disbondment tests and full scale test was also drawn. In light of the results obtained so far in this study, these tests results conclude positively that the bare field joint alternative concept for subsea pipelines is possible upon certain operating temperature limitation.
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| 2. |
- Larché, Nicolas, et al.
(författare)
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Field cathodic protection study in the specific artic conditions of the Yamal gas carrier terminal
- 2018
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United States; 15 April 2018 through 19 April 2018. - : National Assoc. of Corrosion Engineers International. - 9781510864405
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Konferensbidrag (refereegranskat)abstract
- For most projects, cathodic protection (CP) design can be performed using CP standards or existing data from literature and field feed-back. It was not the case for the particular environment of the YAMAL gas carrier terminal project, planned in Sabetta (Siberia - Federation of Russia). This particular area is located between the Kara sea and a river mouth in Yamal peninsula (Artic region). It involves very different conditions in terms of salinity, temperature, liquid/ice phases, all depending on icing/deicing seasons and on the water depth. These very specific conditions can hardly be simulated at laboratory scale and required a specific corrosion and CP study with measurements on site. The global aim of this quantitative study was to collect field data to help at defining an adapted corrosion protection system for carbon steel immerged structure (e. g. berths), and to forecast the related corrosion risks. Regarding the extreme conditions of the site, the main challenge was to design adapted arrays containing corrosion and CP sensors (to be deployed on site), to get representative quantitative data. All systems have been qualified at laboratory scale before use on field site. The deployment was successful and allowed getting actual polarization curves, and local initial corrosion data. In parallel, the stability of zinc galvanic anodes has been evaluated in this resistive environment. For both corrosion and CP data, different results have been highlighted for surface and bottom waters, and for ice & liquid phases. Modelling can now be used to assess the efficiency and select the CP system (i. e. galvanic anode or impressed current)
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| 3. |
- Martien, Daffo, et al.
(författare)
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Corrosion of pure iron and hydrogen permeation in the presence of H2S with O2 contamination
- 2018
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United States; 15 April 2018 through 19 April 2018. - : National Assoc. of Corrosion Engineers International. - 9781510864405
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Konferensbidrag (refereegranskat)abstract
- This paper examines the influence of traces of oxygen on corrosion and hydrogen charging of steel in an H2S containing environment. It is well known that H2S promotes hydrogen entry into steels, that may result in many types of steel failures such as Hydrogen Induced Cracking (HIC), Sulfide Stress Cracking (SSC), and Stress-Oriented Hydrogen Induced Cracking (SOHIC). Since it is a huge concern for oil and gas industries, standard test methods have been developed and published as NACE technical methods (e.g. NACE TM0284 and NACE TM0177). Though it is recognized that oxygen pollution should be avoided during H2S cracking tests, there is still a lack of experimental data to illustrate the potential impacts of a small oxygen pollution. The aim of the present study is to check if oxygen traces can modify the mechanisms of corrosion and hydrogen charging of steel in H2S containing medium. Experiments consisted of hydrogen permeation measurements through a thin pure iron membrane. They were performed at free potential circuit in order to ensure more realistic environmental conditions. The corrosion rate was also evaluated and test solutions analyzed.
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| 4. |
- Ruel, F., et al.
(författare)
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Influence of temperature and pH on SCC assisted by H 2 S susceptibility of 22 %Cr duplex
- 2018
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United States. - : National Assoc. of Corrosion Engineers International. - 9781510864405
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Konferensbidrag (refereegranskat)abstract
- Depending on environmental conditions UNS (1) S32205 duplex stainless steel may suffer from Stress Corrosion Cracking (SCC) assisted by H 2 S initiated by local corrosion processes that involve the selective dissolution of the ferritic phase or the austenitic phase. The intent of this paper is first to study the evolution of the susceptibility of SCC assisted by H 2 S according temperature and pH. In a second phase, links are highlighted between the differences of cracking resistance and localized corrosion morphologies. Results show that the temperature of highest susceptibility to SCC assisted by H 2 S depends on the pH of the environment, moving from 80 °C at low pH (2.8 - 3.5) to temperature between 50 - 20 °C at higher pH (4.5 - 6.0). The maximum of cracking susceptibility seems to correlate with selective corrosion of ferrite coupled with transgranular cracks of the austenite.
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| 5. |
- Thierry, Dominique, et al.
(författare)
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A new crevice assembly adapted for tube geometries to test crevice corrosion in seawater
- 2018
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Ingår i: NACE - International Corrosion Conference Series Volume 2018-April, 2018Corrosion Conference and Expo 2018; Phoenix; United State s. - : National Assoc. of Corrosion Engineers International. - 9781510864405
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Konferensbidrag (refereegranskat)abstract
- Crevice corrosion resistance is one of the main criteria for the selection of a given stainless steel grade for seawater applications. Crevice corrosion resistance can be evaluated using different techniques that are described in standards and in the literature. However, the proposed assemblies are often restricted to plate geometry specimens. Some crevice assemblies for tube geometry have been proposed and used during the last ten years, but they showed a large dispersion of the results due to the difficulty to control crevice geometries on curved surfaces. From this background, an optimized crevice assembly was proposed to allow a better control of the reproducibility of crevice corrosion tests on stainless steel tubes. Finite element modelling and laboratory testing have shown that the new proposed design provides a better control of gasket pressure and consequently a better reproducibility than previous existing assemblies. The proposed assembly can be adapted and used for fit-for-purpose testing (e. g. evaluation of different gasket materials, different gasket pressures, etc.).
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