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Project saves time and money for Amerada Hess


Using results obtained from their membership of a TWI Group Sponsored Project looking at the corrosion and cracking resistance of welded duplex and superduplex stainless steels in sour service, offshore development company Amerada Hess has made considerable savings on both capital investment and lead times for its latest project.

Few data exist for using duplex and stainless steel welds in environments containing hydrogen sulphide (H 2S) and materials properties limits set for parent materials may be overly conservative.

The project investigated two types of duplex (22%Cr) and two types of superduplex (25% Cr) stainless steel using a range of welding processes. In addition, some of the welds tested deliberately contained intermetallic phases. Four-point bend tests were performed in autoclaves with differing levels of H 2S, chloride and pH.

Results show that although superduplex stainless steel is more resistant to severe corrosive media than duplex, for many applications the 22%Cr duplex material is perfectly acceptable.

Following these findings, Amerada Hess substituted duplex stainless steel for superduplex. This saved them money not only by using a cheaper material but also because they were able to receive the material early, rather than wait for the superduplex to be produced. The result was that their operation came on stream earlier than anticipated.

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