Replacement of Structural Support on a Brownfield FPSO Using Cold Work: A Case Study on Bonga FPSO's Pipe Support Replacement
Authors: Abajuo Chuka , Nwamaghinna Nnamdi , Osinjolu Tunde , Court Jean-Philippe , Matteoli Franck , Paillusseau Christophe 
Published: April 2024

The scope of this paper is to discuss the successful replacement of badly corroded pipe support on the Bonga using an innovative cold work technique. The objective of this project was to safely replace corroded pipe supports on top of the crude oil cargo tank without a facility shutdown.

The approach employed in delivering the project involved a systematic process, where a thorough assessment of the corroded pipe support was conducted. The structural engineering team reviewed the replacement pipe supports design for assurance and fit for purpose to carry the load. Pre-fabrication of the replacement pipe support was completed onshore, ensuring precise measurements and adherence to safety standards. An innovative and non-intrusive fastening technique was utilized to securely install the new supports without the need for hot work or welding. This process-controlled technique involves the vacuum-assisted application of an adhesive system to create a durable bond between the deck plating and C-Claw®, a non-intrusive and heavy-duty fastener made of 316L grade stainless steel; the prefabricated support structures are then secured to the fastener stud via washers and nuts. The badly corroded support is cut-off using a cold cutting tool. The installation was completed within the designated timeframe with no disruption to production operations. All the equipment used were intrinsically safe and rated for zone 1 use.

This repair campaign of corroded pipe supports using cold work technique on the Bonga FPSO (Floating, Production, Storage, and Offloading) was completed successfully. The pre-fabrication process allowed for meticulous planning and ensured accurate fitting during installation. Thirty-three pipe supports were replaced in a 10-day timeframe, demonstrating the efficiency of the approach. Observation of the installed support over a period showed excellent performance with respect to load bearing, high durability, and corrosion resistance.

The overall value proposition can be summarized as follows:

Debottleneck shutdown operations: structural repair can now be performed during live production on top of crude oil tank. Zero deferment Reliability & durability: technology class certified for marine environments. Operational flexibility: fast and reliable installation process with no disruption to production operations.

This paper presents valuable insights and additional information for practicing engineers involved in FPSO maintenance, asset life extension and structural replacement. It showcases the effectiveness of a credible alternative to welding in addressing the challenges of corroded structural replacement on brownfield FPSOs. It goes without saying that the advantages include zero downtime, improved safety, and integrity assurance. The methodology, procedures, and results presented in this paper can serve as a practical reference for engineers seeking innovative solutions for structural replacement in offshore facilities.