Floating production, storage and offloading vessels (FPSOs) are exposed to a marine environment and are subject to saltwater corrosion as a result. Repairing their corroded structural parts can be costly and time-consuming, as traditional hot repair work involves numerous risks and major constraints, including and up to halting production. The innovative cold repair technique ensures FPSO integrity in a minimum amount of time, safely and without interrupting production. Deployed in a world first on the FPSO Girassol in Angola, this breakthrough technology enhances our leadership in deep offshore operations.
An Innovation for the Oil Industry
Based on the use of bonded composite reinforcements, this solution combines three technologies: vacuum-assisted resin injection, structural adhesion and assembly of high-performance metallic and composite materials.
Total selected a product developed by French start-up Cold Pad that comprises two layers: a top reinforcing plate made of a super duplex stainless steel and a layer made of composite material that ensures the load transfer between the hull and the steel plating. The prefabricated part is bonded to the FPSO’s surface using a vacuum-assisted injection process that allows the resin to be spread evenly without any need to control atmospheric conditions. A peripheral fluorosilicone seal encapsulates the resin to protect it from seawater and hydrocarbons during the reinforcement’s useful life.
Studies conducted by Cold Pad and Bureau Veritas since 2010 have demonstrated the effectiveness and durability of cold repair on floating vessels in harsh environments and made it possible to qualify the technology. Cold repair is used in other industries, such aviation, but had not been applied until now in an industrial process for hull repair at sea.
A World First In Angola
In 2008, an inspection found 19 corroded areas covering a total of 250 square meters on the FPSO Girassol’s deck plates. This threat to the vessel’s structural and mechanical integrity was what led to the innovative cold repair solution, since no conventional method could provide a suitable response. The corroded surface was too large for buttering to be reliable, and replacing the damaged parts would have required shutting operations down completely to reduce the risks to the integrity of the deck and hull. This would have meant a production loss of 110,000 barrels per day, for 60 days.
Our teams therefore decided to innovate by preparing the FPSO Girassol’s hull for cold repair. Structural bonding of the first reinforcements prefabricated specially for the project by Cold Pad (subcontracted to Hutchinson) was carried out in October 2018, in just 28 days, coming in on time and on budget. Although the remaining work will not be performed until the end of the year, the project’s overall budget will remain below €10 million.
An Attractive Solution
This simple, reproducible technique could be used to repair all flat corroded areas on a floating unit in cases where hot work would lead to considerable production losses and safety risks. The solution is safe and simple, and offers a number of advantages:
- Repairs can be performed during operation, without interrupting production or lowering the availability rate.
- Mechanical reinforcement of the corroded area is optimal. There is no risk of weakening the structure during repair. Cold hull repair extends an FPSO’s lifetime and preserves its integrity.
- Less work is required, since implementing this technology involves only handling and bonding. On site, the work can be performed by a small team with limited equipment. The repair cost is therefore lower than with standard methods.
- The solution improves safety by reducing the risk of accident, fire and explosion, as well as damage to paint, insulation or electronic equipment associated with hot repairs.
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