This paper gives a summary of the most important offshore applications of duplex stainless steels, criteria used for their selection, requirements to materials and fabrication and existing experience gained during fabrication and operation. There is a focus on the North Sea, but world wide applications and experience are also included.

22Cr duplex and increasingly also 25Cr duplex stainless steels are today widely used in the offshore industry. The main applications are for hydrocarbon process piping systems and equipment like separators, scrubbers and pumps. Subsea the materials are used in down hole production tubing, piping and manifolds, X-mas tree components, flowlines and pipelines transporting corrosive oil and gas. Further, 25Cr duplex is now being used also for sea water service.

The selection of duplex stainless steels are based on a corrosivity evaluation covering the transported medium and also external corrosion, mechanical properties, weldability requirements and cost evaluations. Guidelines today applied in the North Sea are presented.

Generally, the experience with application of duplex materials is so far positive. However, as for all engineering materials, some manufacturing and fabrication problems and operational failures have occurred. The experience gained through this, is an important factor in the updating of recommendations for material selection, material specifications and fabrication requirements.