DUPLEX stainless steel is commonly used for offshore pipeline applications. DUPLEX combines the advantages of ferritic and austenitic steel: corrosion resistance, high strength and toughness; therefore making it ideal for use on riser sections exposed to wave loads and bending. DUPLEX pipe is relatively expensive and usually only used for the riser, whereas the rest of the pipeline consists of conventional carbon steel. This mixture of pipeline materials combined with the special magnetic properties of DUPLEX create a challenging environment for inline inspection tools utilizing Magnetic Flux Leakage (MFL) technology.
ROSEN inspected a TOTAL pipeline with a DUPLEX riser in 2008, and then came together in 2009 to investigate the results of the MFL inspection. This paper is discussing the results of this investigation based on pull tests in a 12’’ DUPLEX test pipe with artificial metal loss features.