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| Continuous feeding requires only one part-time operator. Previous weigh-belt system required two operators. |
Moonachie, NJ -- Algood Foods of Louisville, KY, manufactures peanut butter on a contract basis for supermarkets throughout the U.S. The company also supplies other manufacturers with peanut butter for further processing into cookies and confections.
One of the most crucial operations of the peanut butter making process is the mixing of peanuts with the proper amounts of salt, sugar, and stabilizer. Depending upon the recipe called for in a given production run, each of these ingredients vary. For example, stabilizer may be cottonseed, palm, peanut, or any number of hydrogenated oils. Continuous mixing requires accurate ingredient feeding, and places heavy demands on both processing equipment and operator.
PROBLEM:
Microprocessor controls monitor feed rates and adjust feeders for change in bulk density Weigh belts with integrated volumetric feeders were being used for the proportioning of ingredients. During the course of operation, the ingredients would stick to the weigh belts. This caused inaccurate weight measurements and resulted in substandard product mixtures and rework. In extreme cases, substantial amounts of product were scrapped.
Production was frequently halted to allow time for cleaning the belts and recalibrating the scales. Algood President Barney Barnett explains, "Weigh belts proved uneconomical due to high maintenance costs and inaccurate because product buildup resulted in zero reference change. For that reason the weigh belts were operated volumetrically most of the time." According to Barnett, one cu ft of peanuts can vary by as much as 4-5 lb from the next cu ft due to differences in nut size and moisture content. Volumetric measurement alone was not able to compensate for these bulk density changes.
Bridging of ingredients above the belt feeders often caused partial flow losses that were not caught in time. This was another problem which made off-spec mixtures inevitable, and reworks unavoidable. Algood needed an alternative to the problems associated with their weigh-belts.
SOLUTION:
An evolution has taken place on the production lines. Algood initially installed a weight-loss feeder to control the flow of dextrose. They gradually changed over to a completely beltless system of weight-loss-differential gravimetric feeders. The new system requires no calibration. Weight-loss feeders require relatively minimal attention once the operator sets the feeder rates for a particular recipe. Microprocessor-based controllers provide continuous totalization of ingredients at the end of the day, production run, or any desired time interval. Watertight gasketing and wiring facilitate sanitation of the equipment. Food-grade stainless steel construction is used for all product contact surfaces.
The weight-loss-differential feeders employ different feeding mechanisms to effectively handle the flow characteristics of each ingredient. Since peanuts comprise at least 90% of the final product, they require a higher feed rate than that of the other ingredients. The peanuts are metered by a higher capacity single auger-type feed system, while the lower feed rates for the finer, granulated ingredients are controlled through the use of a dissimilar-speed, double-concentric auger metering mechanism.
Both the feeding mechanism and its supply hopper are integrally mounted on an all-flexure, counterbalanced scale (or weighing) system. The flexures are stainless steel for longevity. As material feeds, the amount of product being fed is sensed (as weight loss) by a high resolution weight sensor producing a 20 binary bit (digital) output. This information is simultaneously processed by a microprocessor controller which modulates the feed output based on the feed rate selection. A master rate controller monitors the operation of each feeder, interfacing with the individual feeder controllers to ensure the precise proportion of the ingredients. The controllers update every 0.25 sec, tracking weight loss and modulating the feed output accordingly. In effect, the auger metering mechanisms respond to controller signals to compensate for detected variations.
For example, if peanut density decreases due to a smaller size nut or lower moisture content, the auger will be instructed to increase the flow rate accordingly. "One of the biggest assets of the system is that it adjusts for bulk density," declares Plant Manager Dick Schulbaffer, "if one feeder deviates from the specs we put in the master control, the whole system shuts itself down." When a feeder deviates from the rate preset in the master control, an alarm will sound for 30 sec to alert the operator. If the operator does not respond, the system will shut down to prevent production of sub-standard product. Both platform and overhead type weighing mechanisms are utilized with the feeders and integrated into the production line. In continuous operation, weighing accuracies are typically between ± 0.25 to 1 % total deviation.
RESULTS:
The switchover to weight-loss-differential feeders from weigh belts has virtually eliminated the problems of equipment maintenance, production downtime, product scrap, and reworking. John Stinson, Engineering and Maintenance Manager, comments that the feeders "prevent off-spec product that we wouldn't have caught until quality control. Re-work takes hours."
The savings in time, labor, and money are incalculable, but real. "It's impossible to say exactly how much the system has saved us, or when it will pay itself back," Stinson explains, "before, if a production deviation went undetected for minutes, hundreds of pounds of product could be lost. In an hour, we are talking about tonnage."
The system has not only solved problems, but it has gone further to improve product quality and uniformity, cleanliness, yield, and inventory control. Algood now knows to the fraction of an ounce how much peanut butter is manufactured. The highly accurate metering and proportioning of ingredients enable product line diversification.
Algood Foods has been so impressed with the feeders that they installed a completely new, second line of four feeders in July 1988. Work is now in progress to interface printers to the master rate controller so that data can be saved for long-term statistical analysis. Information on feeder number, feed rate, and deviation taken at various time intervals will further improve inventory and, production control.
For more information contact:
Acrison, Inc.
20 Empire Blvd.
Moonachie, NJ 07074
Telephone: 201-440-8300
Fax: 201-440-4939
Email: informail@acrison.com
Website: http://www.acrison.com/
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