Power Engineering International

Unorthodox problem, traditional solution

How tried-and-tested repair materials were used to fix a problem with the cooling water system of a nuclear power plant, writes Marina Silva

Composite repairs and wrap systems are not necessarily a hot topic anymore, with many standards, procedures and case studies available on the subject.

However, every so often we still come across a story of a simple wrap being used as an ingredient for an unorthodox, well-engineered repair solution.

One such solution involved a nuclear power station in France, where the operators identified a problem at the bottom of a sump pit of their cooling water system.

The 200mm ID suction pipe protruding from a concrete wall was experiencing severe corrosion. An externally-applied repair was not feasible as corrosion extended well beyond the area encapsulated in concrete.

To make matters worse, the flange connecting the pipe to the drain pump was also badly corroded.

Belzona's distributor in western France, Alliatech, came up with a unique solution which would solve the problem and prevent any further corrosion for the long term.

A cut and weld technique would have caused needless downtime and the extent of metal degradation called for more than a protective lining.

For minimum downtime and fast return to service, a repair had to be completed from the inside of the pipe. A durable 500mm long 'composite insert' was created using the Belzona SuperWrap II system and a plastic former.

The procedure followed some of the steps taken for a regular pipe wrap: Wetting out the reinforcement sheet with resin; Applying the sheet onto the former with 50 per cent overlap; and consolidating the wrap using the release film provided. The composite insert was created complete with a new flange, 70mm wide and 10mm thick. Once the sleeve was cured and former removed, it was sanded with holes drilled to match those of the original flange.

The next step was to bond the insert into the pipe. After grit blasting, Belzona 1161, a surface-tolerant paste-grade material, was used as an adhesive between the sleeve and the pipe, at a maximum thickness of 10mm.

Finally, to ensure lasting erosion-corrosion protection, Belzona 1321 (Ceramic S-Metal), a 100 per cent solids ceramic protective coating was applied on the inside, outside and around the pipe to prevent any issues from reoccurring.

It is amazing how many problems can be solved with tried-and-tested repair materials, particularly these days, when there is a focus on restoring rather than replacing, reducing downtime to a minimum and optimising operating efficiency.

Solutions that can adapt to the everchanging challenges are the future of industrial maintenance.

Marina Silva is Marketing Supervisor at Belzona Polymerics. Belzona designs and manufactures polymer repair composites and industrial protective coatings for the repair, protection and improvement of machinery, equipment, buildings and structures. www.belzona.com

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