Material Handling March 1988 Plant Services
Chemical spray prevents ice buildup, ends conveyor belt punctures
J.A. Summers General Foreman,
Raw Materials Handling, Bethlehem Steel Co., Chesterton, IN
John Papamarcos Senior Associate Editor
Problem
The Material Handling Division of Bethlehem Steel Corporation, Burns Harbor Complex, uses stacker/ reclaimer machines for iron ore, coke and other raw materials necessary for ironmaking by the Blast Furnace Division. As a critical part of the production process, excessive downtime of these machines could not be tolerated. However, in winter, buildup of ice and frozen fines on the pulleys of the steel cable reinforced boom belts would result in punctures of the conveyor belts due to breakage of the steel cables. This required the stacker/reclaimer to be taken out of service for repair or replacement of the belt.
The Burns Harbor Complex, located at the southern end of Lake Michigan, is subject to some severe weather conditions. In particular, the pulley and belt of the stacker/reclaimer are located 40 ft above ground level and have no protection against wind, snow and freezing rain. As temperatures fall below 28°F, warm, moist reclaimed material contacts the cold pulleys and freezes.
Iced lumps formed in sizes ranging from 1 to 4” in diameter. Freezing fines would continue to build up until the larger lumps punctured the belt. These punctures would occur each time the pulley completed a revolution, and would run the whole length of the belt. Icing such as this could and did, destroy the steel cable belts. These belts are prestressed to a tension of 2100 psi, and there is no tolerance to allow for ice buildup on the pulleys. When ice did build up, it could cause a knot of frozen material to form on the pulleys. This would cause the cables to snap, which in turn would result in punctures of the conveyor belt.
Solution
Attempts were made to eliminate the ice formation by applying antifreeze to the belts, but this was not effective. Then, one day, a representative of another company (who was at the plant in regard to another matter) heard about the ice formation problem and mentioned that he had a product that should be effective. The product had demonstrated success in preventing belt icing and in removing ice glaze, and in preventing and removing ice buildup on idlers and pulleys. It is also formulated to produce belt friction, so belts can carry coal when they harden under extreme low-temperature conditions.
Bethlehem Steel obtained a quantity of the product and experimented by applying it by hand. The results were good, so an automatic system was installed. The product is sprayed directly on the pulley and, in turn, the belt is coated by a squeegee effect. Local plant personnel developed a custom-designed spray system, which is designed to turn on automatically, depending on the temperature, and to spray at any frequency needed again, depending on weather conditions. For example, at 28°F the pulley is sprayed for 15 seconds every 15 minutes. At 32°F, the pulley is sprayed every 30 minutes.
Since the product was so effective in preventing icing of the stacker/ reclaimer boom belts, it was decided to try it on the bucket wheel, which often became coated with frozen fines, and would require downtime for cleaning. Results in this case were also good and a spray system was designed to apply the chemical into the buckets of the digging wheel. This system is manually operated. About every 2 hours when icing conditions exist, the operator stops digging and pushes a button to spray the bucket wheel for 2 minutes. This helps reduce freezing fines from building up in the digging buckets and spills plates
Results
Bethlehem Steel Co. is very satisfied with the conveyor belt deicer. It not only ended downtime and the cost of repairs to the stacker/reclaimer boom belts, but it was also found to be effective in preventing the buildup of frozen fines on the bucket wheel.
