Eskom Medupi Power Station – Corrosion Protection of 6 off Stainless Steel Flue Cans
Project Title: Medupi Power Station Build: 6 X 800mw Coal-Fired Steam Turbines 4th Largest Coal Fired Power Station in the World
Scope of Work: Corrosion Protection of 6 off Stainless Steel Flue Cans
Corrocoat SA (Pty) Ltd - Contractor
• Eskom required a high temperature coating resistant to chlorides and flue gas, applied to stainless steel at a temps up to 250° C.
• The elevated temperature profile required that the coating temperature resistance offer protection at 137° C & 180° C during potential short term temperature excursions.
• Corrothane XT material, rated for protection up to 260° C gas temperatures continuously with excursions to 300° C.
• The Polyglass VE material, rated for protection up to 170° C continuous gas temperatures and short excursions to 200° C.
• Abrasive grit blast cleaning was the preferred method of surface preparation although the cans were 200m above ground level.
• Corrothane XT lining was used for the internal top 2 metres following removal of the top two rows of borosilicate bricks inside the flue cans and abrasive blast cleaned using Aluminium Oxide (to ensure zero contamination of the Stainless Steel substrate).
• Corrothane XT & XTHA was applied using 71:1 Wiwa Airless pumps at a minimum DFT of 700 microns, allowed to cure and then flash blast cleaned to offer a mechanical key for the re-installation of the borosilicate bricks & Pennguard adhesive on completion.
• In addition, Corrothane XT would be applied to the top three rings of the flue cans externally, for higher temperature protection.
• The balance of the external surfaces of the flue cans were abrasive blast cleaned with platinum slag and coated with Polyglass VE & stripe coated with Polyglass VEHA to a minimum DFT of 600 microns with an average DFT of 750 microns.
• Corrocoat has offered a 20-year Warranty for this project work.
• The project was managed using Project Labour Agreement (PLA) & Site Specific Agreement (SSA) between Unions & Contractors
• Our staff compliment consisted of a management team of 5 plus a site crew of 30 people including 16 core crew & 14 local labour.
• Total contract value of circa ZAR 21 Million.
• Working 200 metres up required careful forward planning: constant supply of drinking water for crew for fatigue mitigation, ablution facilities, ensuring availability of materials, small tools & equipment at the work face.
• Conveying of all materials and equipment to the top of the stacks, including water for degreasing & decontamination purposes.
• Approximately 700 linear metres of sharp edges to grind and radius to the 316L Stainless Steel substrate.
• Approximately 1300 linear metres of Hand-Application stripe coating required.
• High ambient conditions posed a challenge in terms of gelling of airless spray pumps, guns & material lines.
• Minimum of 20 minutes to reach the top of the stack using the Torga Elevator, or 1 hour each way by foot!
• Mandatory safety requirements included entry & exit medicals, general & site specific inductions, working at heights training, working with hazardous chemicals & grinding training for every crew member, including management, core crew & local labour.
• Arduous Health, Safety & Environmental adherence required, including: Safety Files, DSTI, Toolbox Talks, Compliance Inspections.
• Adherence to all QA/QC requirements, continuous QC surveillance & daily inspections, DFT & HV Spark, QCP docs & data books.
• HSE, HR/IR & QA/QC Audits undertaken by the Client monthly, with a minimum 95% compliance requirement to be maintained.
• The 20 Year Warranty requirement dictated that every single operation undertaken was checked and double-checked for conformity and documented in intricate detail, to protect both the Client as well as Corrocoat.
• Specialised safety equipment was required, including heat resistant overalls, double-cartridge respirators, double lanyard safety body harnesses (to be worn at all times, even when working on the scaffolding), goggles, gloves, safety boots etc, even at 40° C!
• Difficulty of working in such a restricted space, owing to the volume of scaffolding required for access purposes.