Technical Presentations at the April 2013 Meeting

1.1         Keynote:  ‘Copper Alloys in Marine Environment: Corrosion, Fouling, and Mechanical Behavior’, Andrew Drach, Dept of Mechanical Engineering, University of New Hampshire, USA   (Co-authors: Igor Tsukrov, Department of Mechanical Engineering, University of New Hampshire; Uwe Hofmann, Jochen Aufrecht & Adolf Grohbauer, Wieland-Werke AG, Ulm, Germany)

The utilization of copper alloy components in the systems deployed in marine environment presents potential improvements due to reduced maintenance costs, prolonged service life and increased reliability. However, integration of these materials faces technological challenges which will be discussed in this presentation, including characterization of material performance in seawater environment.

The focus of this talk will be on the investigation of corrosion, biofouling and mechanical behavior of copper alloys through field trials in the North Atlantic and lab testing in artificial seawater. Nine alloys and two reference materials (pure copper and mild steel) in a plate form were deployed for one year in the Portsmouth Harbor, USA (North Atlantic Ocean). Material loss rates were quantified by measuring the difference in weight between the virgin specimens and the cleaned specimens after recovery. Localized corrosion damage was characterized by analyzing the cross-sectional micrographs and SEMs of corrosion layers. Biofouling resistance was evaluated by measuring the biomass accumulated on the surface. The results of this study were compared to the accelerated lab testing in artificial seawater. Changes in mechanical properties due to the seawater exposure were quantified by performing standard uniaxial tension tests. Fatigue and wear resistance were investigated through lab testing in artificial seawater in specially designed test rigs. 

It was observed that corrosion rates of most of the tested alloys are similar to those of pure copper, and all alloys with the exception of one showed excellent resistance to biofouling. Some degradation of tensile strength was observed in all alloys, but for most of them it was not substantial. 

[This work was supported by the International Copper Association, Ltd. Wieland-Werke (Germany) is gratefully acknowledged for supplying the test specimens and collaboration in research]

 

1.2     ‘Nickel Alloys in Subsea and Downhole O&G Applications’, Steve McCoy, Special Metals PCC Energy Group  

The presentation gave an overview of the PCC Energy Group combining the manufacturing plants of Special Metals, Wyman Gordon, RathGibson and KLAD for a range of stainless steel, nickel alloy, clad pipe, tube, welding, long and flat products.  The various stainless steels and solid solution nickel alloys used in the Oil & Gas industry were compared in terms of mechanical properties and the compositions shown alongside their calculated PREN values for stainless steel 316L up to the very highly alloyed Ni-Cr-Mo material INCONEL alloy 686.  The ASTM G48 6% FeCl3 critical crevice temperature was correlated and shown that a value of greater than 35C gave a high resistance to localised corrosion in natural seawater.  

The age-hardenable nickel alloy bar materials have also become widely used in downhole oil and gas drilling and completion tools due to their excellent sour corrosion resistance, high mechanical strength and toughness.  The history of the development of the nickel alloys was discussed from the development of a modified INCONEL alloy 718 in the 1970’s through to the new generation of NACE MR0175/ ISO 15156:3 approved high strength material in INCOLOY alloy 945 for HP/HT wells.  [smccoy@specialmetals.com]

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1.3   ‘The SOHIC Story, A 30 Year Project’, Chris Fowler, Exova 

The 30-year story of Stress Orientated Hydrogen Induced Cracking is nearing its final chapter.  This presentation looked at the history of SOHIC, OTI 95 635, some case histories, the “NEW” Plate test method and the Final Chapter:  

  • Validate Test Method – on-going 
  • Produce written procedure – Complete
  • Consider Joint Industry Project to study the SOHIC mechanism now that a true test method is available:  Variables to consider:-
    • HARDNESS
    • Microstructure
    • Chemistry
    • Weld and HAZ properties
    • Level of Hydrogen charging

3.1    'Reflections on 25 Years of Corrosion Management in Oil & Gas Production', Steve Paterson, Shell UK Ltd

Steve Paterson, Head of Materials, Corrosion and Inspection at Shell UK, gave a presentation about his reflections on 25 years of corrosion management in oil and gas production.  He spoke about the importance of corrosion management post-Piper Alpha and highlighted some of the fundamental changes that have occurred with corrosion management systems since 1988.  He illustrated this with examples of significant changes that have occurred in Shell especially over the last 10 years, and provided an explanation of the active corrosion management framework that is currently in place.  He also explained the many improvements that have occurred in corrosion and sand erosion modeling.  He covered improvements in corrosion inhibition and gave examples of failures of corrosion resistant alloys that have been increasingly used in place of carbon steel. Lastly he discussed future challenges and focused on life extension of ageing assets, skill shortage of materials and corrosion engineers, and increasing societal demands post-Macondo. 

3.2    ‘Varanus Island Incident: A Technical Review of Lessons Learned, with Applications to European Gas and Oil Pipeline Operators’, Brian Wyatt, Corrosion Control

The Varanus Island Incident offshore Western Australia was initiated by external corrosion of an export gas line in a tidal foreshore location.  Fire ensued.  A parallel line failed almost immediately due to the fire.  Other pipeline failures followed, and damage was suffered by the adjacent terminal.  The direct cost of damage was estimated at A$60 Million followed by A$3 Billion loss to the Western Australian economy due to loss of gas supply. 

The technical lessons learned in the published Government of Western Australia Incident Investigation Report do have, in many ways, relevance to European, including North Sea, practice for oil and gas pipelines at land/sea interfaces.  These lessons include specific requirements for monitoring the performance of coating and CP systems on foreshores, particularly in tidal sand backfills, the need for greater rigour than is common in respect of criteria for protection and the assessment of how these criteria are met, the need for competent Certificated personnel to be responsible for both data collection and data interpretation and the requirement that Management properly respond to reports of deficient coating and cathodic protection systems in a timely manner.

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