The Role of Stainless Steel in Offshore Applications

Stainless steel, including duplex stainless steel and super duplex stainless steel, bring significant economic benefits to the offshore oil and gas industry. Compared to other materials, it has a lighter weight, greater strength, stronger corrosion resistance, and lower life cycle cost. In this article, we will detail the role of stainless steel in offshore applications.

The Role of Stainless Steel in Offshore Applications：

For global production and processing of hydrocarbons, offshore projects are extremely important. In some of the most extreme environments, offshore crude oil accounts for nearly 30% of global crude oil production. However, the saline ocean environment requires offshore platforms to have high safety and longevity standards. Marine and offshore infrastructure are often exposed to the effects of high levels of air and water-borne salts, and ordinary carbon steel structures are often corroded and require regular maintenance and upkeep.

On the other hand, stainless steel is a reliable choice for the robust materials used in heavy offshore facilities. The inherent corrosion resistance of the metal provides a high strength-to-weight ratio for infrastructure, even under marine and coastal environmental conditions. Stainless steel also ensures a longer design lifespan, as well as impressive resistance to extreme pressure and high temperatures. Notably, by using stainless steel, the expected service life of offshore structures can be nearly five times longer than its competitors.

Life Cycle Cost：

In addition to a longer lifespan, stainless steel is more qualified for offshore applications due to the increasing emphasis on the lowest life cycle cost (LCC) in construction and construction. This concept emphasizes the strong demand for the development of new infrastructure that is highly durable and requires minimal maintenance or repair.

Reducing weight is also a major driver for installing offshore structures. Reduced weight means lower construction costs for the structure, while allowing for increased drilling and production equipment for oil and gas production and exploration.

Steel Grades Used in Offshore Facilities：

SS316L is the main austenitic stainless steel grade used in offshore facilities, which can enhance strength at high temperatures and protect structures from corrosion in severe acidic environments. Austenitic steels with 6% molybdenum are typically used in environments permanently immersed in seawater. However, due to global nickel price fluctuations in the past few years, duplex stainless steel has widely replaced austenitic steel grades. Duplex stainless steel combines excellent mechanical properties with resistance to stress corrosion cracking, making it an ideal choice for offshore applications. UNS S32205 steel is the most commonly used duplex stainless steel grade for offshore facilities.

Although duplex stainless steel performs well in offshore heavy-duty facilities, the new generation of super duplex stainless steels can rival austenitic stainless steel in corrosion resistance to seawater. Additionally, these grades offer significantly improved mechanical properties compared to duplex steel. These super duplex steels feature higher contents of nitrogen, chromium, molybdenum, and nickel, which help improve their resistance to pitting and crevice corrosion. For example, UNS S32750 and UNS S32760 grades are used for underwater components of offshore facilities with more aggressive corrosion conditions.

While it is noted that stainless steel can better replace carbon steel, it is crucial to understand that selecting the optimal stainless steel grade for specific needs is essential for cost-effectiveness and durability of offshore facilities.

The Role of Stainless Steel in Offshore Applications：

Underwater components: pipelines and gratings for oil transfer, wastewater discharge and water drainage, the outlet of oil transfer platforms, heat exchangers on ships and coastal power plants, equipment installed on ship hulls.

Platform structural components: pumps, winches, storage tanks, process containers, explosion-proof doors, umbilical cables, reinforcing steel, cable trays, stairs, walkways, gas coolers, gravity separators, etc.

Ship deck components such as deck holes on ships, anchor support brackets, hook rings, etc.

Coastal (land-based) handrails, ladders, lampposts, etc.

The Department of Metallurgy and Materials Science at the University of Manchester/UMSIT conducted a study entitled “The Development of Stainless Steel Applications in Offshore Pipeline Systems”. The results indicate that using super duplex stainless steel in offshore project spray systems can reduce weight and installation size compared to 90/10 copper-nickel (Cu-Ni) alloys. Spray systems require minimum spray nozzle pressure and water flow. Compared to 90/10 Cu-Ni systems, super duplex stainless steel systems use less piping to control water velocity. Therefore, the dry weight of super duplex stainless steel spray systems can be reduced by approximately 15%.

In addition, the study found that due to the higher strength of super duplex stainless steel, the required piping for installation is reduced by approximately 38%, which also means that if super duplex stainless steel is developed for applications such as sprinklers and fire sprinkler systems, further weight reduction of approximately 20% can be achieved.

Therefore, compared to 90/10 Cu-Ni alloys, the weight and piping requirements of a standard super duplex stainless steel spray system are effectively reduced, essentially serving as an alternative solution that improves efficiency and reduces costs. The research results indicate that the effective cost reduction of using super duplex stainless steel piping materials for standard spray system development will be close to half of that achieved by using 90/10 Cu-Ni alloys.

Conclusion

Thank you for reading our article and we hope it can help you to have a better understanding of the role of stainless steel in offshore applications. If you want to learn more about stainless steel, we’d advise you to visit Sino Stainless Steel for more information.

As a leading supplier of stainless steel products across the world, Sino Stainless Steel provides customers with high-quality stainless steel products such as stainless steel strips, stainless steel coils, stainless steel plates, stainless steel sheets, stainless steel bars, and stainless steel tubes at a very competitive price.