Spray Coating

Carried Out by: Metal-7
Client: Noth American Iron Mine
Date: 1/12/03

An Upper Michigan Iron Mine  used a roll feeder to transport and screen green balls to the traveling grate system at the taconite facility. The roll feeder has 19 rolls 8-½” diameter X 225” long that roll the green balls. The rolling maintains the shape, screens the undersize and fines until they are loaded on to the traveling grate where they are fired and hardened into iron ore pellets.

The rolls were coated with ½” urethane cover to prevent wear. The required roughness Average (80ra) was difficult to produce and caused sticking on the rolls. The sticking would prematurely wear the neighboring rolls and also caused the rolls to become a roll crusher which increased the fines and reduced screening efficiency. The problem was not reduced by different Durometer urethane or rubber from multiple manufactures.

During the last twenty years, METAL 7 has designed several coatings which has allowed companies to improve their market position, to become more competitive and/or to develop new technological opportunities.

Metal-7 had just introduced a new thermal spray coating that has tungsten carbide in it for wear abrasion and can handle some impact forces. The new coating A19 was the best coating for the application. One roll was installed and tested with no sticking. Two more rolls were purchased and placed in series with excellent results. Over the next year the entire roll screen was replaced with Metal-7 rolls and has been running perfectly since. Until 2 was soon converted to a smaller 7-¼” roll for better screening with the A19 coating.

October, 2009 five rolls have been sent in for repair and re-coating, establishing the average life over 5 years which exceeds the expectations in performance and life. This life cycle improvement has also incurred the following:

  • Reduced fines
  • Larger % of on size balls
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