Martin Kirchgassner, Castolin Eutectic, explains how preventive maintenance and repairs based on advanced wear protection solutions can extend the life of critical machinery.
The wear of vital machine parts is a significant cost for the cement industry, not only in terms of repairs, replacement, and ongoing maintenance, but also in lost production – millions of dollars per day in some cases.
The cement challenge
Machinery in cement production is subject to various different types of wear such as abrasion, impact, friction, erosion, fatigue, corrosion, and heat, as well as combinations of all of these factors. Since 1906, Castolin Eutectic has been developing and applying wear solutions for all aspects of the process from the quarry to the packing plant. This now forms the basis of the company’s philosophy ‘Pioneering Industrial Sustainability’, since if critical equipment functions optimally, it consumes less energy. Therefore, cement plants can help improve their energy efficiency and reduce their CO2 footprint.
This article outlines how wear protection in the form of advanced welding solutions or coatings can make a major contribution to uptime and productivity in four main areas: the Vertical Roller Mill (VRM), roller press rollers, kiln tyres, and fan refurbishment.
VRM: fast response and extended life expectancy
A VRM is used to crush materials into very fine particles. The key components in the VRM are subjected to severe wear which can increase dramatically when high silica content is found in the raw materials or where mills are grinding slag. The finish milling process is generally the single largest area of energy consumption in a cement manufacturing plant. That means wear problems can have an important impact on energy efficiency, and therefore plant profitability. A worn VRM roller profile also reduces grinding efficiency, which further impacts energy efficiency.
A key concern for any cement plant is the availability of the critical processing equipment, especially the VRM. Downtime during refurbishment is a major cost, and there is continual pressure to reduce this time and enable the plant to return to full production status. Castolin Eutectic responded to these challenges by reviewing the entire on-site welding operation to develop the Advanced High Speed Repair Concept. Its team delivers this through advanced welding equipment technology, application-specific welding consumables, advanced automation and data logging, multi head control, modern logistics and a dedicated VRM package.
This service provides the cement industry with the highest grinding performance and the fastest refurbishment speed – 36 hours for 3 or 4 rolls and a table. In some cases it totally avoids any kiln stoppage if the customer has the capability to store material temporarily.
The VRM can be divided into two parts, the top end and the bottom end. These parts can be fabricated from special wear plates known as CastoDur Diamond Plates (CDP®) based on composite bi-metallic materials. They comprise an easy-to-weld steel plate overlaid with abrasion and erosion resistant alloys by three possible methods: arc welding, metal-atomised coating or plasma powder coating.
At the top end, VRM outlet ducts often suffer severe wear due to the high-velocity fine particles. A previous solution would be to use AR 600 wear plates based on heat-treated high-carbon steel with wear and abrasion resistance around 15 times that of ordinary steel. However, when substituted by CDP the operational lifespan is increased by up to six times more than AR 600 wear plates.
In this application, the CDP features a mild steel base with a coating developed for extreme abrasion and erosion resistance. Its complex carbide structure contains a high density of hard particles. Extremely hard boron and niobium particles are finely dispersed in between chromium carbides, reducing their spacing and ensuring the best protection from abrasive and erosive media of finer size.
Enjoyed what you've read so far? Register to World Cement, for free, to access the rest of the article and the entire August issue.