Case Study: High-Performance Vibrators Improve Hopper Performance for Refractories Manufacturer
Effective vibrators can remove leftover materials from hopper walls and prevent product contamination.
Wahl Refractory Solutions, based in Fremont, Ohio, was founded more than 90 years ago by Oscar C. Wahl. Since then, the 60-employee company has grown to be a recognized leader in the manufacturing of precise and durable refractories castables and pre-cast shapes. The company develops and manufactures its own alumina-based refractories products, ranging from very small to those that weigh more than 30,000 lbs.
Refractories are commonly needed for heating applications above 1,000°F and must also withstand physical wear and corrosion by chemical agents. Refractories are used to build structures subjected to these high temperatures, including linings for furnaces, power plant reactors and boilers, as well as ladles, stilts and kilns. Some refractories have also been used as heat shields for the Space Shuttle.
Not only does Wahl produce more than 200 types of refractories, but the company also makes a variety of castable materials used in the production process. This dry, castable composite material needs precise metering through steel hoppers before the mixing process. Wahl relies on 2-in. impact vibrators and 2-in. air-cushioned vibrators from Cleveland Vibrator Co. (CVC) to ensure that all of the dry material flows completely out of the hoppers.
“We use a specific amount of castable material for each refractory part, so it’s vital that all the material is totally out of the hoppers,” says Andy Aelker, senior buyer for Wahl. “Plus, we don’t want to mix composites because we use different materials for each project. That means the hopper must be free of residual contaminants from the last job.”
One of Wahl’s primary castable materials is slurry-infiltrated fiber castable, or SIFCA®. SIFCA is a precast composite composed of refractory slurry and stainless steel fiber. It is a combination of stainless steel fibers and any one of 10 slurry types. Another Wahl material is FIBERStone, a combination of high-temperature ceramic materials and specially alloyed stainless steel fibers.
“Depending upon the specific job, we can load the hoppers with different material every day,” says Aelker. “Without the vibrators, some material would stick to the hopper walls. That leftover material would then co-mingle with the new, incoming material, causing contamination and an inferior castable product.”
Preventing Sticking and Clogging
Wahl chose the CVC 2-in. impact vibrators because they are ideal for moving sticky materials that tend to clog hoppers under continuous vibration. The impact vibrators deliver individual impacts at timed frequencies that can be adjusted to fit the job at hand. Their low-frequency knocking action simulates a manual, forceful hammer strike—without the manpower or potential damage to equipment.
Wahl also uses CVC 2-in. air-cushioned vibrators that offer a quieter performance with the same force as the CVC impact vibrators. The air-cushioned vibrators provide purely linear force to allow the controlled application of directional force on materials. These vibrators are used as a flow or discharge aid on bins and hoppers, but are also useful on feeders, conveyors, alignment tracks, screeners, and compaction tables. The air-cushioned vibrators deliver quieter performance with only slightly less force than the impact vibrators.
Turning dry castables into refractories is accomplished in several steps. In one facility, workers mix the composite material according to a customer’s order, then meter the material into the steel hoppers, which measure 6 x 6 x 9 ft and can weigh as much as 2,000 lbs when filled. Wahl has 30-40 hoppers in continuous use for various customer orders.
Steel hoppers are transported across the complex to another building where the refractories are produced. With the aid of a forklift, three to four hoppers are placed on top of a conveyor bin where the product is metered into the mixer. Workers place a CVC vibrator into a pre-made channel on the outside of the hopper wall for the most effect.
Several Seconds Does the Job
“The vibrator is only on for few seconds, but it’s enough to shake the whole hopper around and knock all the material out,” says Aelker. “Since we use these hoppers for different applications, it’s important that the entire product is removed. The hopper then goes back completely empty ready to be filled again.”
After the dry castable material is conveyed into the mixer, the composite turns into slurry, which is used for forming into the desired shape. Firing inside an oven forms the ceramic bond that gives the product its refractory properties. The final stage involves milling, grinding and sandblasting.
The vibrators have been put to the test since CVC contacted Wahl two years ago for an initial order. “We had Cleveland Vibrator repair two older vibrators that we put back into service, then purchased two more new units on a trial period,” Aelker says. “After one month on the trial, we purchased them outright. We now have four vibrators in constant use and have been very satisfied with the performance.”
Benefits of the 2-in. impact vibrator include:
• One-piece, ductile iron housing, hand-finished bore and spring-less design ensure long effective life
• Use of exhaust muffler reduces noise levels
• Dual diameter piston allows for mounting at any angle on bins, chutes, pipes and hoppers handling; industrial vibrators come with mounting fasteners and a gasket for quick setup
Benefits of the 2-in. air-cushioned vibrator include:
• Air cushion prevention of metal-to-metal impact and exhaust muffler reduce noise levels while pneumatic power allows for operation in hazardous areas
• Dual diameter piston allow for mounting at any angle on bins, chutes, pipes and hoppers