Session: 02-12-01 Reliability Based Maintenance and Inspection Planning

Submission Number: 156601

Experiences With Duplex Stainless Steels in Offshore Grating Systems 

Structures located in challenging marine environments play a vital role in a number of sectors, including offshore wind and oil and gas exploration. These environments include seawater, the air above the seawater that contains chlorides from sea spray, and onshore coastal regions. Generally, offshore structures are expected to have a long life, because access for inspection and maintenance is limited.

Corrosion is one of the major issues that marine structures face as they are exposed to a chloride-rich environment, wet-dry cycles, high humidity, and microbiological attacks. Material selection, together with the methods used to protect against corrosion, play an important role in determining the reliability, maintenance needs and lifetime of marine structures. Duplex stainless steels have been used in marine environments for a long time. Compared to conventional austenitic stainless steels, duplex materials offer a high strength in the solution annealed condition. This allows the design of lighter structures based on thinner gauges.

Grating systems are often found on offshore installations, from oil and gas rigs to offshore wind farms. These can be cost-effectively constructed in duplex alloys. Forta EDX 2304, Forta DX 2205 and Forta LDX 2101 have been successfully installed in seaside environments, where their strength and improved corrosion allowances permit thinner sections and weight savings. Improved localized corrosion resistance in chlorides, meaning increased pit and crevice corrosion resistance, suggests that service life can be greatly improved, and maintenance needs are diminished.

The objective of this paper is to share past experiences with duplex gratings in offshore structures and describe the rationale behind the selection of this class of materials.

Presenting Author: Rodrigo Signorelli Outokumpu

Presenting Author Biography: Rodrigo Signorelli has degree in materials engineering and over 15 years of experience in technical marketing of stainless steels, particularly duplex and high strength stainless steels as well as corrosion.Currently Rodrigo is part of the technical value creation team of Outokumpu focusing on the Marine & Energy sector globally, with special focus on applications such as Oil & Gas, Chemical Process Industries. He is based in São Paulo, Brazil.