In recent years there have been a number of high profile failures of duplex stainless steel components, which have been attributed to Hydrogen Induced Stress Cracking (HISC). In all instances the combination of susceptible material/microstructure, the presence of hydrogen, and sufficiently high strains, have resulted in failures with significant environmental and cost impli-cations. In all cases the source of hydrogen has been from the cathodic protection (CP) system. These failures and subsequent failure laboratory work have demonstrated that base materials, in particular heavy forgings, and welds are susceptible to this type of failure. One of the failures occurred in an A/S Norske Shell operated field in the Norwegian Sea. The findings from the failure, along with the failures suffered by other Operators and on-going research work, have been reviewed to determine a strategy for reducing the risk of HISC in duplex stainless steels for subsea applications. One key learning from our failure, which has had a major influence on this strategy, was the conclusion that standard inspection techniques and procedures were not always adequate to detect very fine cracks in base materials and lack of fusion defects in welds. This paper summarises the main factors influencing HISC and also the current strategy adopted by Shell U.K. Limited. It includes discussion of novel approaches adopted to reduce hydrogen entry into welds, through the use of nickel alloy weld caps, and enhanced inspection requirements to ensure defect free materials. Recent experience with the DNV RP F112: Design of Duplex Stainless Steel Subsea Equipment Exposed to Cathodic Protection, Draft Issue April 2006, is also covered.
Reducing risk of hydrogen induced stress cracking (HISC) in duplex stainless steel for subsea applications
Verminderung des Risikos für Wasserstoffversprödung des nichtrostenden Duplex-Stahls in Meerwasser
2007
12 Seiten, 4 Bilder, 2 Tabellen, 8 Quellen
Aufsatz (Konferenz)
Englisch
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