In iron and steel casting, a ladle bottom had better be able to take the heat. And the pressure. 3,200° F and tons of it, pour after pour. HarbisonWalker International (HWI), a member of Calderys, the largest supplier of refractory products in North America, knows that what goes into a ladle bottom can make the difference between expected longevity or an early trip to the scrapheap.
“The life of a ladle bottom mostly depends on the purity of materials being used and how they’re mixed,” said Ken Newell, quality and safety manager at the company’s plant in Thomasville, Ga. “We had an old mixer built in the ‘60s and were increasingly concerned about downtime and safety.”
Worn parts increased mixing cycle times, and the difficulty of finding replacement parts required more and more lead time, affecting productivity. To protect its reputation for world-class products, HWI turned to Pewaukee, Wis.-based Mixer Systems, Inc. for a solution.
“Our first exposure to Mixer Systems was procuring parts from them for another mixer that had gone out of production, so they were a logical resource,” Newell said.
Mixing low moisture castable materials for making high-temperature refractory and furnace shapes is a very abrasive, demanding application. Mixer Systems offers three different styles of mixers specifically designed for the refractory market.
“We proposed the Model Super 100 Turbin mixer for HWI,” said Scott Adams, product manager of the company’s DustMASTER division that serves the refractory industry. “The Turbin is a low-profile pan style mixer that utilizes a stationary tank with internal rotating mixing arms and scrapers. It offers more aggressive mixing, a roll/shear action that quickly creates a homogeneous mix.”
Before committing to the purchase, HWI took Mixer Systems up on its standing offer to test-mix customer materials at its headquarters.
“We sent materials for Mixer Systems to trial in a mixer there, and did the same with one of their competitors,” Newell said. “Overall, we were much more impressed with Mixer Systems, it was easier to do typical maintenance than on the other machine. We also liked the mixing action better, felt it was more thorough and required less energy.”
The project scope at HWI in Thomasville included the mixing plant along with the demolition of the existing mixer area and complete mechanical/electrical installation of the new plant. The mixer was supplied on a platform structure with stairway for easy access. The mixer discharge height was designed for direct loading into a casting bucket that can be transported to the molding area with a forklift.
“In operation, a 4,000 lb. batch is loaded through the top grated cover of the mixer from a superstack via an overhead crane,” Adams said. “Water is batched during the mixing process using custom-designed controls produced and programmed in-house, and water meter interface for a 3% to 5% addition rate. A hydraulically operated slide door discharges the completed batch in 30 to 45 seconds.”
Mixer Systems also worked with HWI on specifying wear parts with a longer lifespan. These included components made of urethane, AR-225, AR-360 bolt-in steel liners, and cast Ni-Hard paddles and scrapers.
“Comparing our tonnage now with before, we’re close to doubling it with overall lower wear part costs,” Newell said. “And we know these wear parts are something Mixer Systems can supply.”
From signing the purchase order to delivery, the project took about six months. Installation was also provided by Mixer Systems, with placement, assembly, wiring, plumbing and equipment startup all completed in eight days.
HWI has realized a speedy return on investment from the new plant with reduced batching time. “Depending on the material, the majority of batches take three to four-and-one-half minutes, where our previous mixer was at a minimum of five minutes,” Newell said. “The efficiency helps us create more capacity in an eight-hour day since we only mix one shift.”
Clean-up of the mixer after batching has been reduced as well due to the easy access into the mixer through hinged safety interlocked top cover doors. The mixer charging hopper can be removed for even more access if required. Maintenance items and adjustments are also easily reachable, generally on the outside of the mixing tank.
Eager to keep its edge in the highly competitive refractory catables industry, HWI has invited key customers to inspect its operations since the installation of the new mixer.
“They’ve been through the facility and have been impressed with what they saw here, the material and the lengths we go to keep contamination out and the washdown of the mixer,” Newell said. “The customer says, ‘This is what we’re trying to do,’ and they have enough trust that we can give them a good product.”
HWI expects their new Turbin mixer to have a long and productive life.
“Mixer Systems has been very, very good about answering questions or concerns we had since the day installation was completed,” Newell said. “You get the feeling when talking to them you’re getting expert advice. I’m extremely happy with their support.”










ixtures too early or too late in the main water sequence can prevent them from dispersing properly which can weaken the mix or alter its intended characteristics.
ater from the mix, can further complicate matters, preventing the formation of a smooth, homogeneous blend. These small missteps, if left uncorrected, can significantly degrade the strength, workability and finish of the final product.










