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In the past, much of the plant’s material handling operation was done manually. The plant received truckloads of 100-lb paper bags of raw ingredients that varied in particle size and bulk density, and these bags were stored in the warehouse until needed. Pallets of bags would then be moved into production and staged on a production line, where an employee hand-batched the ingredients into a stationary hopper according to a given recipe. Many of the plant’s recipes required a variety of different types of materials to be added to the batch.
Once the ingredients for a batch were emptied into the hopper, a belt conveyor transported the batch from the hopper to a mixer, and the hand-batching process would start again. Each production line—there were four at the time—had a batching station with an operator emptying ingredients from 100-lb. paper bags into a hopper. (The company has added one additional production line since then.)
According to Fred Daniels, plant manager, the entire batching operation relied on operators adding ingredients accurately and efficiently. Spilled ingredients, as well as any residue left in emptied bags, often resulted in waste and potentially inaccurate batches. Additionally, manual bag handling created a dusty environment and caused some ingredient loss from spills near the hopper.
Operators were asked to maintain product accuracy and to control workplace dust by using engineered dust collection equipment for each product line and by cleaning the facility at the end of each day, but it was difficult to avoid empty bags piling up near each manual batching station. “We would accumulate the empty bags at each production line,” said Daniels. “Then we had people assigned to compact the bags for disposal. This was a very dirty and time-consuming process.”
Searching for a SolutionIn the late 1990s, the plant decided to look for a new system that could improve its material handling operations. The company wanted a system that would conserve raw materials; reduce the waste from empty paper bags; improve quality; and provide employees with a cleaner, safer environment. It decided to test an automated system from Ingredient Masters (Cincinnati, Ohio) as part of its evaluation process. “We set up one station for handling raw materials, and then we tested all of the various particle sizes and bulk densities of ingredients that we handled over a period of six months,” said Daniels.
Daniels was pleased with the results. “The system was very user and maintenance friendly,” he says.
During the six-month trial period, Uni-Ref also evaluated several other material handling systems, but many of these were either too large or too expensive, or required a complicated discharging operation. The Ingredient Masters system, on the other hand, could be custom designed and expanded to fit Uni-Ref’s specific requirements and was relatively simple to operate and maintain. Daniels was also impressed with the company’s knowledge of the industry. “The manufacturer knew our business. They definitely have a good knowledge of the refractory industry and they provided excellent support,” he said.
Installing an Automated SystemBased on its positive experience with the technology, Uni-Ref installed an Ingredient Masters Mini-Bulk System in early 1998. The system’s components include 12 dispensing stations that each support a frame for a bulk bag. Each frame is independent of the station, is transportable by forklift, and has an airtight flexible sleeve and slide-gate valve for unloading material to the station.
Each station’s components include a 42-cu-ft polyethylene dispensing bin with a PC-controlled, positive shut-off dispensing mechanism and a load cell. Product flow is controlled by a PC and a PLC as each station discharges ingredients to the belt conveyor.
Rather than receiving 100-lb paper bags of refractory ingredients, the plant now uses 3000- to 4000-lb bulk bags for most of its materials. Bulk bags are transported to the warehouse by forklift and placed in the support frame above a dispensing station. An operator opens the bulk bag to unload material to the dispensing bin, which is connected to the control valve with a dust-tight sleeve.
Once the material is in the bin, an operator uses a PC with a pre-loaded formula to control how much material is dispensed to the conveyor. The load cell measures the weight of the material to be discharged, and ingredients from other dispensing stations are sequentially discharged onto the conveyor, so as not to overload the transfer rate.
“Each station works independently, and they will all run until they have discharged the material and the amount that that the formula calls for,” Daniels said.
The belt conveyor transports the different ingredients for each batch to a large bulk bag that is then taken to a production line for mixing.
According to Daniels, the new system has made production at Uni-Ref far more efficient. Product spills have been almost completely eliminated, and operators no longer need to expend the time and effort to remove empty bags from the work area.
Daniels estimated that labor costs have been reduced by 30% and bag disposal costs by more than 55% with the new system. He also estimated that product loss due to spillage and residue left in empty bags has been reduced by nearly 80% after switching to the automated system. “We haven’t really put a dollar figure on the savings, but we know that the number of mistakes or human errors that we had in the past greatly outweighs the minor mistakes we have made learning this system,” Daniels said.
Production throughput has increased by over 20%, and the plant now operates at near 90% capacity. Aside from the cost savings and production gains, Daniels said that the potential worker injury has also been greatly reduced, and product quality has been improved.
“The biggest advantage [the automated batching system] gives us over manual batching is we have a chance to review the batch prior to it going into production,” said Daniels. “Previously we depended on our suppliers to provide the correct weight in each bag and the operator to produce each batch correctly during the production process.”