Dr Gary Heath explains how component repairs can lead 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.
Component repair rather than replacement produces immediate costs savings and also reduces the use of materials, energy and transport in producing these new components.
If the lifetime of the 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.
After years of research, field tests and involvement of power plant engineers, many innovative products have been developed to support the maintenance departments 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 in this article.
Wear resistant plate solutions
For the wear protection of large surface areas such as chutes, coal mill cones, separator discs, blades or slag protections the ideal solution is the weld overlay wearplate.
Castolin Eutectic have the widest global wearplate range sold under the name CastoDur Diamond Plates (CDP). CDP plates consist of an easy-to-weld steel plate over-laid with abrasion and erosion resistant alloys. Innovations have included the patented lightweight, smooth powder fused plate, superhard Tungsten Carbide plate and the first impact resistant plates.
A new Stainless Steel base metal allows these plates to provide optimal wear resistance in aggressive corrosion environments such include fans, cyclones, chutes, liners, etc.
Another recent development was to translate this technology into producing internal weld overlay of seamless tubes.
The production technology allows wear protection coating of 3m long tubes of any internal diameter down to 82mm.
The major wear areas outside the boiler are usually on pneumatic transport piping and elbow of coal/fuel and ash removal. Here, original elbow lifetime increased by a factor of three by using a new design and the CastoTube solution.
In the 1970s, Vertical Roller Mills (VRMs) became increasingly dominant for grinding raw materials mainly in the power industry due to their high energy efficiency and excellent drying capacity.
The VRM components are subjected to severe wear and this wear can increase dramatically when high silica content is found in the raw materials.
Consequently such wear problems can influence significantly the profitability of a plant.
During the past decades, together with our partners we have proved that preventive maintenance on VRM can extend the critical component lifetime by as much as 100 per cent. This is done with automated weld overlay of the rollers and the tables, plus use of CDP wearplates on house and rotation parts.
Such maintenance operations have been performed on over 60 units, with 80 per cent being on-site repairs but also many repairs in our workshops.
More than 30 different VRM models have been weld overlaid for more than 20 companies throughout the world. From small VRM (roller: 1.65mØ and table: 2.75mØ) to massive ones (roller: 3.2mØand table: 5.5mØ), we have been successful working on equipment from Polysius, Loesche or FLS and Raymond.
Together with the R&D department, the VRM team has developed special anti-wear products providing unbeatable resistance to abrasion, impact and erosion.
The new TeroMatec wire EO 8338 (open arc wire) which provides an extra smooth surface but an extremely resistant coatings.
Reduced wear on rollers
In one recent application in the Middle East this new EO8338 wire was able to reduce wear on the rollers from 9 grams per ton crushed to 3 grams when build up to 40mm thickness on a four roller system.
Today these solid industrial references are being used for new alloy development, supported by improvements in application equipment to meet the increasing performance demands.
Extending tube life
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.
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.
In addition, these coating processes can be applied either on site or off site in dedicated coating workshops, depending on the plant's scheduling.
Castolin Eutectic's thermal power plant repair service package includes:
- A wide range of innovative products to solve wear problems.
- Increased service life over conventional welding alloys.
- Fast and more efficient return of plant to service.
- Alloy development and in-house manufacturing.
Castolin's Castolab Services maintenance experts can visit a customer's premises to solve the problem on-site.
Castolin Eutectic is a leader of application solutions in maintenance, repair and wear protection. More than 100 years of experience in welding, brazing and thermal spraying technologies stand for professional and innovative solutions.
The company employs more than 1,500 people worldwide in over 100 countries.
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Dr Gary Heath is with Castolin Eutectic, Lausanne, Switzerland. www.castolin.com