Project Overview
In early 2025, Shengtao Metal participated in a major offshore oil and gas infrastructure upgrade project located in Southeast Asia. The project involved the replacement and expansion of aging carbon steel piping systems on a floating offshore processing platform operating in a highly corrosive marine environment.
The offshore platform had been in operation for more than 14 years and was experiencing increasing maintenance costs caused by internal corrosion, chloride-induced pipe degradation, and operational instability within several high-pressure fluid transportation systems. The operator initiated a modernization program focused on improving operational safety, reducing maintenance shutdowns, and extending the platform’s long-term production lifespan.
Shengtao Metal was selected as the stainless steel piping supplier for multiple critical process sections, including seawater cooling systems, chemical injection pipelines, condensate transfer systems, and high-pressure utility lines. The project required high-strength corrosion-resistant stainless steel materials capable of operating continuously under offshore environmental conditions involving saltwater exposure, humidity, high pressure, vibration, and fluctuating temperatures.
The total supply scope included approximately 3,200 meters of stainless steel pipes and tubing, along with flanges, elbows, reducers, welded fittings, and customized spool assemblies. Pipe diameters ranged from DN25 to DN500, while operating pressures varied between 20 bar and 85 bar depending on the process area.
The client required all materials and fabrication procedures to comply with ASTM, ASME, NACE, and offshore oil & gas engineering specifications.
Material Selection
Material selection was one of the most important technical aspects of the project because offshore oil and gas environments create extremely aggressive corrosion conditions. Traditional carbon steel systems often experience accelerated corrosion due to seawater exposure, chemical media, and high chloride concentrations.
After detailed engineering review, Shengtao Metal recommended a combination of 316L stainless steel and duplex stainless steel 2205 depending on the operating conditions of each system.
316L stainless steel was selected for medium-pressure utility systems and condensate transfer lines because of its excellent corrosion resistance, good weldability, and stable long-term performance in humid marine environments.
For the high-pressure seawater cooling systems and chemical injection lines, duplex stainless steel 2205 was selected due to its significantly improved resistance to chloride stress corrosion cracking and pitting corrosion. Duplex 2205 also offered nearly twice the yield strength of standard austenitic stainless steel, allowing engineers to optimize wall thickness while maintaining pressure integrity.
Several sections transporting high-temperature chemical media required SCH80 duplex pipes with reinforced flange assemblies to ensure operational safety during continuous offshore production cycles.
The engineering team also prioritized material traceability and quality consistency because offshore maintenance operations are highly complex and extremely expensive. All supplied materials included complete mill test certificates, PMI verification reports, heat number traceability, and corrosion resistance documentation.
Engineering and Design Challenges
The offshore platform presented several technical and logistical challenges during both engineering and installation phases.
First, the platform remained operational during most of the upgrade process. This meant installation schedules were highly restricted and required careful coordination with production shutdown windows.
Second, offshore environments involve constant vibration and dynamic structural movement caused by waves, wind, and rotating equipment. Piping systems needed to maintain long-term stability under continuous mechanical stress conditions.
Third, several process systems operated under extremely demanding temperature and pressure conditions. The seawater cooling network continuously transported highly saline seawater at flow rates exceeding 2,500 cubic meters per hour, while chemical injection systems operated at pressures approaching 85 bar.
To address these challenges, Shengtao Metal worked closely with offshore EPC contractors and platform engineers to optimize piping layouts, support structures, and spool fabrication designs.
Advanced 3D piping models were developed to reduce installation complexity and minimize interference with existing offshore equipment. The project team also optimized pipe routing to reduce turbulence, minimize pressure losses, and improve maintenance accessibility within confined platform spaces.
Manufacturing and Fabrication Process
All piping materials were produced under strict quality control procedures to ensure full compliance with offshore engineering standards.
Pipe manufacturing followed ASTM A312 and ASTM A790 specifications depending on material grade and application requirements. Duplex stainless steel pipes underwent additional ferrite phase balance testing to ensure proper corrosion resistance performance after welding and heat treatment.
Shengtao Metal implemented enhanced inspection procedures throughout production, including:
Special attention was given to weld quality because offshore environments place extremely high demands on welded joints.
All spool fabrication utilized TIG and automatic orbital welding procedures qualified according to ASME Section IX standards. Heat input levels were carefully controlled during duplex welding operations to maintain proper ferrite-austenite balance and avoid reduced corrosion resistance within heat-affected zones.
Following welding completion, all internal weld surfaces underwent pickling and passivation treatment to restore chromium oxide protection layers and improve long-term corrosion resistance performance.
The internal surface roughness for critical chemical injection systems was maintained below Ra 0.8 μm to minimize particle accumulation and improve flow stability.
Offshore Installation Process
Due to limited offshore working space and restricted crane operation schedules, the installation process required extensive pre-fabrication before transportation to the platform.
More than 380 prefabricated spool sections were manufactured onshore and transported to the offshore site in staged shipments. Each spool assembly was labeled with digital traceability codes linked to inspection records, welding procedures, and installation documentation.
To reduce offshore welding workload and improve installation efficiency, engineers maximized the use of prefabricated assemblies wherever possible.
Installation crews operated under strict offshore safety procedures throughout the project. Pipe lifting operations, confined space entry procedures, and hot work activities were coordinated carefully to avoid disruption to ongoing platform production.
The platform’s high-pressure seawater system upgrade required temporary bypass systems to maintain cooling circulation during installation. Shengtao Metal coordinated closely with offshore operations personnel to ensure safe transition procedures during piping replacement activities.
Despite difficult weather conditions and limited offshore working windows, the installation phase was completed within the planned project schedule.
Testing and Commissioning
After installation completion, the entire piping system underwent comprehensive testing and commissioning procedures.
Hydrostatic pressure testing was conducted across all major process systems using pressures ranging between 1.5 and 1.8 times normal operating pressure.
The duplex seawater cooling lines were tested at pressures exceeding 120 bar over continuous six-hour testing cycles. No leakage, weld cracking, or pressure instability was detected during testing procedures.
Additional offshore validation testing included:
Several seawater circulation systems were operated continuously for 72 hours under full production flow conditions to verify long-term operational stability.
Inspection teams also conducted boroscope internal weld inspections on selected critical lines to verify weld penetration quality and absence of oxidation contamination.
All testing procedures successfully met offshore engineering acceptance criteria.
Operational Results
Approximately four months after commissioning, the offshore operator completed an operational performance review comparing the upgraded stainless steel systems with the older carbon steel infrastructure previously used on the platform.
The results showed substantial operational improvements across multiple areas.
Key performance improvements included:
The operator also reported improved production stability due to fewer unexpected maintenance interruptions affecting critical offshore systems.
One of the most significant benefits involved maintenance cost reduction. Offshore repair operations are extremely expensive due to specialized labor requirements, transportation logistics, and production downtime costs. By upgrading to corrosion-resistant stainless steel infrastructure, the operator significantly reduced long-term lifecycle maintenance expenses.
Conclusion
This offshore oil and gas piping upgrade project demonstrated the critical role of high-performance stainless steel materials within modern marine energy infrastructure. Offshore environments expose piping systems to some of the harshest operating conditions in industrial applications, requiring materials capable of maintaining long-term corrosion resistance, pressure stability, and mechanical reliability.
Through the use of 316L stainless steel, duplex stainless steel 2205, advanced fabrication technologies, and strict quality control procedures, Shengtao Metal successfully delivered a highly reliable offshore piping solution tailored to demanding operational requirements.
As offshore energy projects continue prioritizing operational safety, maintenance reduction, and infrastructure longevity, corrosion-resistant stainless steel systems are becoming increasingly important across the global oil and gas industry. Shengtao Metal continues expanding its offshore engineering support capabilities, duplex stainless steel production capacity, and project coordination expertise to meet the growing demand for high-performance industrial piping solutions worldwide.
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Simply provide your specifications such as material grade, dimensions, quantity or application, and our team will respond quickly with professional support and a competitive quotation.
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