If the lifetime of a repaired part can be increased over that of a new part, plant performance and availability can also be improved, leading to significant energy savings and carbon generation.
For many years energy demand has been strongly growing and will continue. The installation of new plant capacity can take years so there is an enormous pressure on power plants to improve operational output, efficiency and availability. Further, there is the constant requirement to reduce operating costs and the environmental impact of achieving these targets. The maintenance department can play a critical role by selecting longer-lasting key components to extend outage intervals and also reduce unplanned down-time and inventory.
Component repair rather than replacement produces immediate costs savings and also reduces the use of materials, energy and transport in producing these new components.
After years of research, field tests and involvement of power plant engineers, many innovative products have been developed to support the maintenance departments in their daily fight against wear and corrosion. From welding and brazing through to thermal spraying and wear protection parts, many solutions have been developed to extend the life of critical power plant components (by as much as five times). A selection of these wear resistant technologies and their related applications are highlighted.
Wear resistant plate solutions
Weld overlay wear plates are becoming popular for the protection of large surfaces against wear in coal/alternative fuel and ash handling. However, their usefulness in a power plant can be restricted in some applications by the minimum plate thickness, surface roughness, lack of abrasion and erosion resistance. One of the most comprehensive and successful ranges of plate products are called CastoDur Diamond Plate (CDP) which include specific plates and alloys to resist abrasion, erosion, impact and corrosion.
The latest development are the unique CDP Powder wear plates. The use of super hard Tungsten Carbides particles offer high abrasion and erosion resistance in combination with light weight, minimal thickness (as low as 3mm) and smooth surface. A new variation which uses a Stainless Steel base metal allows these plates to provide optimal wear resistance in aggressive corrosion environments. Typical applications include fans, cyclones, chutes, liners, etc.
Nano structural engineering
The world's first NanoAlloy formulation was developed to provide outstanding abrasion and erosion resistance using an innovative nano structural engineering approach to alloy development based on a low cost ferrous base. This science was translated into a welding wire which could be used with normal welding equipment in the power plant but producing a protective overlay with a bulk hardness over 71HRC. Applications have been proven in the power industry in coal, ask and alternative fuel transport and grinding systems. Use in coal grinding systems have shown a 5 times improvement in wear life in key components.
Industry proven boiler tube protection against corrosion and wear
Castolin Eutectic was among one of the first companies to develop dense, thermally sprayed coatings to protect boiler tubes in power plants against wear and corrosion in the 1980s and have developed a considerable reputation and experience of these coatings. Success is based on a combination of alloy development and also a special coating deposition process (Spray and Fuse). A novel high Molybdenum, nickel, silicon alloy was developed and patented for severe corrosive/wear environments.
This solution combined with the inherent properties of such Spray and Fused coatings of metallurgical bonding, zero through porosity provided improved service performance over all other solutions on the market is increasing the use of this approach. The increasing use of alternative fuels is extending the corrosion problems in waste to energy plants and leading to new developments.
Through development in the early 1990s with leading power companies and high temperature wear institutes a family of iron-based high temperature alloys was developed to protect boiler tubes from high temperature erosion wear using the arc wire spray deposition process. Today these solid industrial references are being used for new alloy development, supported by improvements in application equipment to meet the increasing performance demands. At many coal/waste plants, boiler tube coating is an established route to extend tube life and progressive companies offer a range of protection alloys and processes tailored to the specific wear and corrosion demands of the plant.
Wear protection of transport tubing
The major wear areas outside the boiler are concerned with the crushing and transport of coal/fuel and ash removal.
A pneumatic ash transport from the boilers to the ash cyclone caused the original elbow lifetime to be increased by a factor of three by using a new design and the use of CDP wearplate solution.
Conclusions
Castolin Eutectic's thermal power plant repair service package includes: a wide range of innovative products to solve wear problems; on-site and in our workshop refurbishment possibilities; increased service life over conventional welding alloys; fast and effective return to service; aIloy development and in-house manufacturing.When a power plant's critical parts are too large to be moved for example, Castolin's CastoLab Services maintenance experts will visit a customer's premises to solve the problem on-site.
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Tony Nogaredes is Project Manager & Marketing, Castolin Eutectic, Lausanne Switzerland. www.castolin.com
