A new design concept has been introduced for cathodic protection of offshore pipelines with high strength stainless steel materials such as Supermartensitic Stainless Steels (SMSS) and enhanced coating systems such as multilayer Polypropylene combined corrosion protection and thermal insulation coatings. The objectives of the concept are to reduce the susceptibility for Hydrogen Induced Stress Cracking (HISC) and coating damages. Conditions for the pipeline material, which can cause Hydrogen Induced Stress Cracking (HISC) have been studied and this has motivated the use of the new design concept. The study has been concerned with materials testing, CP-design parameters, CP installation and pipeline attachments, pipeline design, coating quality and direct electrical heating systems for hydrate control. The study has shown that the most critical factors for HISC are pipeline conditions with high stress and strain, especially stress concentrations, potential levels more negative than -0.80 V vs. Ag/AgCl electrode, low operating temperatures, coating failures and deep waters (high hydrostatic pressure). The paper will give a detailed overview of the new concept with regard to: selection of protection potentials for different pipeline materials, selection of design current density requirements, use of anodes with reduced driving potentials, use of subsea isolating joints, CP design principles, Installation methods, compatibility with the direct electrical heating systems for hydrate control. Basis for the design has been the new ISO draft Standard 15889-2 on pipeline cathodic protection for offshore pipelines. Several of the new design parameters have been challenged and the new concept gives a significantly increased distance between anodes.
A new concept for cathodic protection of offshore pipelines to reduce hydrogen induced stress cracking (HISC) in high strength stainless steel materials
Ein neues Konzept für den kathodischen Schutz von Offshore-Pipelines zur Verringerung von wasserstoffinduzierten Spannungsbrüchen (HISC) in hochfestem rostfreiem Stahl
2003
12 Seiten, 6 Bilder, 2 Quellen
Aufsatz (Konferenz)
Englisch
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