FPSO Triton: UP treatment of Side Shell Longitudinal
Ultrasonic Peening as a Sustainable Life Extension Solution for FPSO Triton
As the offshore energy sector undergoes a fundamental transformation driven by the global energy transition, there is a growing imperative to optimize the use of existing infrastructure. Extending the operational life of floating production systems such as FPSOs is not only economically prudent, but also critical for achieving lower lifecycle emissions, reducing resource consumption, and supporting a more environmentally responsible approach to energy production.
In alignment with these principles, a recent structural integrity assessment of FPSO Triton revealed critical fatigue concerns in several Water Ballast Tanks (WBTs). Finite Element Analysis (FEA) identified substandard fatigue lives for welded joints located:
- At the side shell longitudinal in the way of web frames, and
- At the side shell longitudinal in the way of transverse bulkheads.
The estimated fatigue lives for these details were 15 and 7 years, respectively—well below the 20-year design target for the vessel’s structural service life.
To address these concerns, and avoid invasive structural reinforcement or early decommissioning, it was decided to implement Ultrasonic Peening (UP) treatment on a total of six WBTs.
Why Ultrasonic Peening?
Ultrasonic Peening is a mechanically-based surface enhancement technique that induces beneficial compressive residual stresses at the weld toe, effectively retarding crack initiation and growth. Compared to traditional repair methods, UP offers several compelling advantages, particularly in the context of aging offshore assets:
- ✅ Life Extension: Increases fatigue life by a factor of 4 under high stress ranges and up to 10 times under lower stress conditions.
- ✅ Environmentally Sound: No material removal, no waste generation, and no chemical treatments required.
- ✅ Efficient Onsite Application: Performed with portable tools, minimizing downtime and eliminating the need for hot work or large-scale structural modifications.
- ✅ Validated and Recognized: Life extension performance supported by internal fatigue testing, SN design curves, and international standards such as the IIW Recommendations and DNV-RP-C203.
Environmental and Strategic Benefits
The decision to extend the life of these critical welded joints through Ultrasonic Peening is not only a technical solution, but a strategic one—contributing directly to sustainability and lifecycle optimization goals. The environmental benefits are significant:
- 🌱 Reduced Steel Use: Avoiding structural replacements lowers the demand for new materials, reducing embedded carbon emissions.
- 🌊 Minimized Offshore Interventions: Reduces vessel time, manpower exposure, and fuel use associated with major repairs or reinforcements.
- ♻️ Extended Operational Life: Delaying decommissioning or replacement maximizes the return on the energy and resources already invested in the FPSO.
Importantly, the effectiveness of UP assumes that the targeted welds do not contain active fatigue cracks at the time of treatment. Proper inspection and blast cleaning prior to application are essential to ensure the full benefit of the process. When applied to crack-free details, UP can restore or exceed the original fatigue resistance of the welded joint.
Conclusion
The application of Ultrasonic Peening on FPSO Triton exemplifies a forward-thinking, environmentally conscious approach to offshore asset management. In an era where extending the utility of existing energy infrastructure is both a business imperative and an environmental necessity, such solutions provide a clear pathway toward safer, longer-lasting, and more sustainable operations.
At LETS Global and MTL (Technical Limits), we are proud to deliver qualified fatigue life extension solutions that align with industry needs and global sustainability targets.
🔗 Learn more about our fatigue life extension services at:
www.technical-limits.com
www.lets-global.com
