Silent removal in an occupied offshore living quarters
Continuous 24/7 operations without crew disruption
The Troll A platform is one of the largest and most technically complex offshore structures in the world, located in the Norwegian offshore sector and operated by Statoil ASA. Standing in approximately 303 metres of water, Troll A is a concrete gravity-based structure that plays a central role in Norwegian gas production. Like all offshore platforms of its age, Troll A requires ongoing maintenance and periodic modification works to extend its operational life and meet current safety and regulatory standards.
In 2009-2010, a major modification project was undertaken on the platform’s living quarters module. Before a new living quarters module could be installed, the existing structural walls needed to be prepared for cutting and welding. This required the full removal of all coating systems present on those walls, including the interior paint layers and, critically, the exterior intumescent fireproofing coating applied as part of the platform’s passive fire protection system.
The fireproofing material in question was Chartek, a leading epoxy intumescent coating widely used in the offshore industry for its ability to protect structural steel from the effects of hydrocarbon fires. The Chartek had been applied to a thickness of 20mm over a carbon mesh reinforcement on steel substrates ranging from 12 to 16mm in thickness. Removing this material completely and efficiently, in an occupied living quarters environment where noise and vibration could not be tolerated around the clock, was the central challenge facing the maintenance contractor Norisol AS and their project management team.
Removing Chartek intumescent fireproofing from an offshore platform presents a formidable set of technical and environmental challenges. Chartek is specifically engineered to adhere tenaciously to steel substrates and to resist mechanical and thermal damage, properties that make it extremely effective as a passive fire protection system but equally difficult to remove when structural modifications are required.
The Chartek on the Troll A living quarters walls had been applied at 20mm thickness over a carbon mesh reinforcement layer, making it one of the most substantial and well-bonded coating removal challenges possible in an offshore setting. The steel substrate beneath ranged from 12 to 16mm in thickness, and the requirement was complete removal to bare steel across the full surface area to enable safe and clean cutting and welding of the structural steelwork as part of the new module installation.
The conventional approach to removing Chartek and similar intumescent coatings involves chiselling and grinding, both of which generate significant noise and vibration. On the Troll A platform, the work was being carried out directly on the living quarters module, where crew members on both day and night shifts were sleeping in adjacent cabins around the clock. Noise restrictions limited chiselling activity to a maximum of just 6 hours per day, making progress extremely slow and the overall programme duration far longer than the project schedule could accommodate. The project team needed a method that could achieve the same quality of removal without the noise and vibration, allowing work to continue uninterrupted across all available working hours.`
Norisol AS and Norspray AS deployed a single RPR-1650 unit fitted with a 3:1 handheld transformer and the required lengths of cabling to reach all areas of the treatment surface. Both flat and angle induction heads were used to address the varied surface profiles of the walls, including areas adjacent to structural frames where standard flat heads could not easily access.
The removal process was carried out in two stages. First, the Chartek coating was pre-cut into manageable tile-sized sections using a standard grinder, with the cuts marked up on the surface to ensure consistent sizing and efficient handling. The handheld RPR induction unit was then applied to each section, generating localised heat within the Chartek layer and thermally disbonding it from the steel substrate and carbon mesh reinforcement beneath. Once disbonded, the Chartek tiles separated cleanly from the wall surface and could be broken off and removed from site with minimal effort.
The RPR process produced no noise and no significant vibration during operation, allowing the team to work continuously across all shifts without any restriction on working hours. Rather than being limited to 6 hours per day under the chiselling regime, operators were able to work 24 hours a day, 7 days a week throughout the project. The removal rate achieved was approximately 1 to 2m² per hour, worked in small sections to maintain control and quality across the varied surface conditions.
The result was complete removal of all coating to bare steel across the full treatment area, with the surface left in a condition fully suitable for the cutting and welding operations required for the new module installation. The elimination of noise and vibration from the work process also had a direct positive impact on the welfare and rest quality of the platform’s crew throughout the duration of the project.
