Zero grit waste in a confined chemical vessel
Effective removal where grit blasting was not an option
The Shell Nederland Chemie project at Moerdijk in the Netherlands involved the full interior coating removal of Cation Water Vessel V-402B, a 6.4 metre high vessel with a 3.5 metre diameter located within an active chemical processing facility. The work was carried out between 19 and 30 October 2016 by RPR operators from Bilfinger Salamis UK, under the supervision of RPR Technologies, and in coordination with Bilfinger Brabant Mobiel and Shell Nederland Chemie site management.
This was the first time RPR heat induction technology had been trialled at a Shell Nederland Chemie facility, and the project presented a unique set of circumstances that required careful planning and close collaboration between all parties before work could commence. Navigating Shell’s strict electrical safety protocols, confined space entry permits, and site access requirements was a significant undertaking in itself, but once cleared, the RPR Induction Disbonder proved highly effective on what turned out to be a far more complex coating system than initially anticipated.
The vessel originally appeared to have a 300 micron glass flake interior coating. Upon entry and inspection, the actual coating was found to be approximately 10 times thicker than specified, comprising multiple layers of ebonite, glass flake, adhesive, and soft rubber across different sections of the vessel. This discovery extended the project from a planned one-week duration to two weeks, but the RPR Induction Disbonder handled all coating types successfully, delivering a result that satisfied Shell Nederland Chemie’s requirements and prompted the client to pursue a standardised working procedure for this type of application going forward.
The interior of Cation Water Vessel V-402B presented one of the most complex coating removal scenarios possible for a confined space application. The vessel contained multiple distinct coating systems across different zones, each with its own characteristics and removal behaviour. The tank shell carried a two-layer coating of approximately 2.5 to 3mm of ebonite topped with 0.5mm of glass flake. The lower dome featured a soft rubber coating of approximately 6mm glued directly to the steel substrate. Most challenging of all, the interface zone between the shell and the lower dome had a four-layer coating totalling approximately 12mm in thickness, comprising ebonite, two layers of unknown intermediate materials, and a final soft rubber layer.
The initial brief described a simple 300 micron glass flake coating. The actual coating was roughly 10 times thicker and significantly more varied, meaning the original one-week project scope had to be extended once the true condition of the interior was assessed on-site.
Grit blasting was completely ruled out by Bilfinger Brabant Mobiel as a viable option for this vessel. Working inside a confined chemical vessel, generating 90,000 to 150,000 kilograms of spent grit as waste, with the associated dust, containment challenges, and disposal costs, was not a practical or acceptable approach for Shell or their contractors. A method was needed that could handle unusually thick and varied coating types in a confined space, produce minimal waste, and meet Shell’s stringent safety and environmental standards within an active chemical processing facility.
The RPR GreenTank Induction Disbonder was deployed inside Vessel V-402B using a complete self-contained system setup, including the induction disbonder unit, water deposit, diesel generator, and water cooler mounted on a trailer outside the vessel. Additional utilities including an exhaust fan and isolation transformer were used to maintain safe atmospheric and electrical conditions inside the confined space throughout the operation.
Two RPR operators from Bilfinger Salamis UK worked inside the vessel under the direct supervision of RPR Technologies supervisors, working methodically through each zone of the vessel interior. The induction process thermally debonded each coating layer from the steel substrate, releasing it as solid flakes that could be scraped and collected without generating dust, airborne particles, or the need for any abrasive media whatsoever.
Despite the considerable challenges posed by the unexpectedly thick and multi-layered coating system, as well as the numerous obstructions present in the bottom of the vessel that restricted access and movement, the RPR Induction Disbonder achieved an ideal removal rate of approximately 3m² per hour and a real-world rate of 1.5m² per hour inclusive of evacuation of removed material. The entire interior coating was successfully removed across all zones, with only a sweep blast subsequently required to achieve the specified surface cleanliness and profile for the new coating application.
The total grit consumption for the project was zero kilograms, compared to the 90,000 to 150,000 kilograms that would have been required using traditional sandblasting or UHP methods. Energy consumption for the full scope of work was approximately 525kWh. The result was rated as very satisfactory by Shell Nederland Chemie, and the client subsequently expressed the intention to establish a standardised working procedure for RPR induction coating removal on future vessel projects at the facility.`
