| Spotlight
pumped storage process. In addition, wicket gates, stay vanes, spiral casing and draft tubes are also key challenge areas found in pumped storage hydro plants. If maintenance issues in these key hydropower
problem areas are not rectified, this can ultimately lead to reduced efficiency and therefore, profit-loss. Indeed, in extreme cases this can even lead to asset failures and therefore unplanned shutdowns, whereby the lengthy process of decommissioning and replacing key equipment would ensue. If it gets to this stage, not only would this seriously limit the hydro plant’s ability to serve its primary function, but this would also seriously undermine the environmental benefits of pumped hydro storage. One repair method that is commonly employed to
address these hydropower challenge areas is welding. A traditional technique, welding is often the go-to repair solution for engineers worldwide. However, it is not without its limitations. Welding requires extensive hot work, which in
turn presents significant safety risks. All flammable substances must be cleared and the area made safe for welding to take place. In many cases, this can interrupt essential operations. In addition, replacing a damaged asset with the same material will only lead to the same problems reoccurring in the future. A solution should be sought that not only repairs the damaged assets, but also actively improves and protects them for the long term, all while avoiding the need for hot work.
Polymeric repair solutions and
protective coatings Pumped storage asset owners and engineers are employing cold-curing polymeric systems as alternative repair and protection solutions. In order to provide erosion and corrosion protection, two-part epoxy coatings can be deployed to improve the efficiency of different types of fluid handling equipment such as turbine runners. These types of coatings improve pump efficiency by using hydrophobic technology to repel process fluids
and reduce turbulent flow. In fact, efficiency increases of up to 7% have been recorded on new equipment and up to 20% on refurbished equipment. When compared to polished stainless steel, it was found that Belzona’s epoxy coating, Belzona 1341 (Supermentalglide), was 15 times smoother. For areas that are particularly subjected to high
levels of cavitation, such as Kaplan turbine blades, abrasion and cavitation resistant elastomers can be deployed. These two-part polyurethane resins offer an outstanding level of protection against cavitation at ultra-high velocities (up to 115 knots with no damage). Due to their erosion-resistant properties, ceramic filled coatings provide effective protection of critical equipment, such as spiral casings. These systems facilitate a fast application process, as they can be easily applied by either brush or spray. Bearings, shafts, valves, wicket gates and stay vanes can all be repaired and rebuilt with paste grade systems. This includes two-part repair composites that are specially designed for metal repair and resurfacing based on solvent-free epoxy resins reinforced with silicon steel alloys. These systems can all be applied and cured at room
temperature, thus bypassing the need for hot work and the drawbacks this can incur.
Invest in technology As pumped storage hydro currently represents the
overwhelming majority of on-grid electricity storage, it is imperative that asset owners invest in the appropriate technology that goes beyond simply ‘maintaining’ asset integrity, but actively ‘improves’ the equipment as well. By implementing a rigorous repair, protection and
improvement strategy, key assets can be given a new lease of life. This is thanks to the efficiency enhancing and long-term erosion and corrosion resistant properties of polymeric materials. Ultimately, these repair and protection systems support a greener future for the planet; with pumped hydropower storage being a key energy storage solution for helping industries and countries to meet net zero carbon emission targets by 2050, if not before. ●
Above: Penstock coated to prevent corrosion
Top Left: Combination of polymeric systems on wicket gates
Top middle: Efficiency improved on Francis turbine runner
Top right: Shaft contour built up with series of polymeric systems
Bottom left: Rebuilding of original profile on turbine cover
Bottom middle: Level surface achieved
Bottom right: Application of repair and protection system completed
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