Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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14 NOVEMBER 2018 W W W.MATERIALSPERFORMANCE.COM Composite Insert Bonded into Corroded Pipe at Nuclear Power Site A hybrid composite insert sys- tem was recently used as a solution to solve corrosion issues at a nuclear power sta- tion in France, where operators had iden- tif ied a problem at the bottom of a sump pit of their cooling water system. According to Belzona, an industrial protective coatings and composites spe- cialist and manufacturer of the system used on this project, the 200-mm inside diameter (ID) suction pipe protruding from the concrete wall at the power plant was experiencing severe internal corrosion. In this case, an externally applied repair was not feasible, as the corrosion extended well beyond the area encapsu- lated in concrete. The f lange connecting the carbon steel pipe to the drain pump was also badly corroded. Nearby composite solutions provider A lliatech (Orvault, France), which dis- tributes the manufacturer's products in western France and has carried out numerous pump and heat exchanger repairs for this nuclear power station, vis- ited the site in search of the optimal solu- tion for corrosion resistance. "A cut and weld technique would not have been possible without removing the concrete, which would have caused a lengthy and needless downtime," says Frederic Harlé, managing director of A lliatech. "The extent of metal degrada- tion called for more than a protective lin- ing. The system could not be applied externally on the pipework, as it was housed within the concrete foundations. For minimum downtime and fast return to service, a repair had to be completed from the inside of the pipe." For the job, a 500-mm long composite insert was created using the Belzona SuperWrap II † system and a plastic for- mer. The chemical-resistant wrap system is comprised of a f luid-grade resin sys- tem, a hybrid reinforcement sheet based on f iberglass and carbon f iber, as well as release f ilm to consolidate the wrap. The repair system was engineered for pipe wrap and patch repairs, as an alter- native to replacing defective metallic sub- strates, while providing superior strength and corrosion and chemical resistance. It can be designed and applied in accor- dance with the ISO 24817 1 and ASME PCC-2 2 standards and withstands operat- ing temperatures up to 150 °C (302 °F). "This system's excellent adhesion to metallic substrates, coupled with supe- rior strength [high Young's modulus] and the thermal expansion coeff icient similar to that of steel, make it ideal for restoring asset integrity," says Jérémie Maillard, engineering and business manager at Belzona. "Ty pically, we apply this pipe wrap on the outside of the pipes," Maillard adds. "In this case, it was a complex 'wrap' com- plete with a f lange, which was applied on the inside! To ensure all the layers of the reinforcement sheet and resin were com- pressed, a plastic former was used." The installation procedure for the internal system followed many of the steps taken for a regular external pipe wrap. The maintenance crew f irst wetted out the reinforcement sheet with resin, then applied the sheet onto the former, consolidating it using the release f ilm. The composite insert was created complete with a new f lange, 70-mm wide and 10-mm thick, to replace the original corroded f lange. Once the sleeve cured overnight and the plastic former was removed, it was sanded with holes drilled to match those of the original f lange. The inside of the insert was also coated with a A diagram of the planned composite insert system. Image courtesy of Belzona. A corrosion problem was identified at the bottom of a sump pit in the cooling water system at a French nuclear power station. Photo courtesy of Belzona. Extensive damage of the pipework and concrete was found within the pump drain. Photo courtesy of Belzona. † Trade name. MATERIAL MATTERS

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