Superduplex stainless steel has been used in the cast and wrought forms in seawater systems since 1986. Since that time the alloy has been very successful in cast form for both pumps and valves. The wrought product has been used for piping, fittings, flanges, filter vessels, fasteners, mounting brackets etc. under a range of conditions including the North Sea and the Arabian Gulf. During its use in firewater and seawater cooling systems there has been a small number of failures. These are mostly associated with welds and examination of these failures coupled with laboratory tests has enabled the safe-use limits for this alloy to be established in terms of chlorination and temperature. New developments to extend these limits further are described.
Keywords: Stainless steel, welds, seawater, chlorination, service experience.