Extensive investigations have been carried out by TWI into the fatigue behaviour of welded C-Mn steel catenary risers (SCRs) over the last decade resulting in guidance rules for fatigue design. In the case of corrosive and sour products, knowledge of the performance of welded joints in both C-Mn steel and corrosion resistant alloy (CRA) in such environments is needed. This is particularly important in the development of high pressure, high temperature (HP/HT)deepwater and mildly sour fields. However, there is little information concerning fatigue performance of C-Mn steel or CRA in sour conditions.
TWI is running a major Joint Industry Project to develop fatigue test data for a range of materials in a variety of corrosive environments. The project is currently supported by fourteen major operators, fabricators and material suppliers from eight countries and has a total budget of US$1.4M.
The project is scheduled for completion by mid 2005 when preliminary guidelines on the fatigue design of C-Mn steels and corrosion resistant SCR girth welds in mildly sour conditions will be produced.
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