Abstract: Stainless steel, including duplex stainless steel and super duplex stainless steel, brings significant economic benefits to the offshore oil and gas industry. Compared with other materials, it is lighter, stronger, more resistant to corrosion, and lower life cycle cost.
Offshore projects are extremely important to the production and processing of hydrocarbons worldwide. In some of the most extreme environments, offshore extraction accounts for nearly 30 percent of global crude oil production. However, the saline-alkali marine environment requires offshore platforms to have high safety and life standards. The infrastructure for marine and offshore applications is often susceptible to a large amount of air and water-borne salt. Ordinary carbon steel structures are often subject to erosion, requiring Carry out regular maintenance and maintenance.
Stainless steel, on the other hand, is a solid guarantee of robust material choice for heavy offshore installations. The metal’s inherent corrosion properties provide infrastructure with a high strength-to-weight ratio, even in marine and coastal environmental conditions. Stainless steel also ensures a long design life and impressive resistance to extreme pressure and high temperatures. Remarkably, by using stainless steel, the expected service life of offshore structures can be increased by almost five times compared to its competitors.
Life cycle cost
In addition to a longer service life, due to the increasing emphasis on lowest life cycle cost (LCC) in building and construction, stainless steel is more qualified for offshore applications. This concept underscores the strong need to develop new types of infrastructure that are highly durable and do not require extensive maintenance or repair.
Weight reduction is also a major driving force behind the installation of offshore structures. The reduced weight means the structure is less expensive to build, while allowing for the addition of drill pipe and production equipment for oil and gas production and exploration.
Types of steel used in offshore installations
SS316L stainless steel is the main austenitic stainless steel grade used in offshore installations, it can enhance the strength at high temperature, and also protect the structure from the attack of severe acid environment. Austenitic stainless steel grades containing 6% molybdenum are usually used in environments that are permanently soaked in seawater. However, duplex stainless steels have widely replaced austenitic grades due to fluctuating global nickel prices over the past few years. Duplex stainless steels offer an excellent combination of mechanical properties and resistance to stress corrosion cracking, making them ideal for offshore applications. UNS S32205 stainless steel is the most commonly used duplex stainless steel for offshore installations.
Although duplex stainless steels are outstanding in heavy-duty offshore installations, the new generation of super duplex stainless steels is comparable to austenitic stainless steels in seawater corrosion resistance. In addition, the mechanical properties of these steel grades are significantly improved compared to duplex steels. These super duplex steels are characterized by higher contents of Nitrogen, Nitrogen, Ni, and Nickel, which contribute to their resistance to pitting and crevice corrosion. Example UNS S32750 and UNS S32760 steel grades for underwater components of more aggressive offshore installations.
Although duplex stainless steels are outstanding in offshore heavy installations, the new generation super duplex stainless steels are comparable to austenitic stainless steels in seawater corrosion resistance. In addition, the mechanical properties of these steel grades are significantly improved compared to duplex steels. These super duplex steels feature higher nitrogen, chromium, molybdenum, and nickel contents, which contribute to their resistance to pitting and crevice corrosion. Such as UNS S32750 and UNS S32760, which are used for underwater components of more aggressive offshore installations.
While we note that stainless steel is a better substitute for carbon steel, the key is to understand that selecting the best stainless steel grade for a particular need is critical to the cost-effectiveness and durability of offshore installations. As the largest stainless steel producer in China, Baowu Steel Group has a dedicated research and development institution, focusing on the production of high-end steel grades, and occupies a major share in the consumption of all similar products in China
Applications of stainless steel at sea
Subsea components: pipes and grilles for oil transfer, sewage and drainage, risers for oil transfer platforms, heat exchangers for ships and coastal power plants, equipment installed on the hull.
Platform structural components: pumps, winches, storage tanks, process vessels, blast doors, umbilicals, steel bars, cable trays, stairs, treads, walkways, gas coolers, gravity separators, etc.
Ship deck components, such as ship deck eyelets, anchor cable brackets, shackles, etc.
Coast (on land) Handrails, ladders, lampposts, etc.