UNS S31254 - A BLEACH PLANT SUCCESS STORY

This paper traces the development of the superaustenitic grade 254 SMO (UNS S31254) as a solution to recurrent corrosion problems within the pulp and paper industry. The composition of 20Cr 18Ni 6.1Mo 0.2N imparts a high corrosion resistance but has also presented challenges such as development of good welding practice.

Examples are given from different field tests within the industry and to extensive subsequent application to chlorine (C) and chlorine dioxide (D) stages in bleach plants. For a long period S31254 was used as a regular construction material for filter washers. Due to environmental concern the most aggressive stages have gradually been replaced with chlorine-free agents that are less harmful to stainless steel and needing less high performance material. Also superduplex steel provides economic alternatives reducing the amount of installations with S31254.