A customer needed to accurately measure the mass flow rate of snack food pieces from a cooler, in order to ratio control the amount of seasoning applied to the snack food pieces. The snack pieces were to discharge from a vibratory conveyor, flow through a mass flow measurement system, and then proceed to the seasoning tumbler where the seasoning was to be applied. They needed the meter to be able to output an instantaneous, accurate signal that could be used to control the seasoning feeder system. It was also critical to have a compact mass flow measurement system due to space constraints. The average density of the product was 4 lb/ft3 (64 kg/m3) with a maximum flow rate of 2500 lb/hr (1134 kg/hr) and a minimum flow rate of 300 lb/hr (136 kg/hr). This meant that the flow meter needed to be capable of handling and accurately measuring a volumetric capacity from 75 to 625 ft3 /hr. Besides providing an output to a controller, the meter needed to have a local display indicating flow rate, total throughput per shift, and the total throughput per week.
THE SOLUTION FROM EASTERN INSTRUMENTS
The customer installed a CentriFlow Meter. The unit selected for installation between the vibratory conveyor and the seasoning tumbler was a 12" Type I CentriFlow Meter, installed in the In-Line Flow configuration at a 20o installation angle. The Ratemeter/Totalizer was used as a local display of rate and total flow per shift, while the second totalizer function was used to totalize weekly throughput. The averaging analog 4-20mA output from the Ratemeter/Totalizer provided a mass flow rate to the PLC (proportional to the flow rate). This signal allowed the PLC to control the flow rate of the seasoning, the flow rate of the snack mix entering the tumbler, even the rate of the tumbler itself, allowing the customer to correctly ratio the seasoning with the snack mix, as well as to determine the totalization of the throughput of the process.
CONCLUSIONS
Once the CentriFlow Meter was installed, the unit was calibrated within a few hours and the seasoning system operated successfully. The meter's output provided a much more accurate ratio of snack mix to seasoning, thus saving the customer by reducing waste. After having used weigh-belts in the past, the customer was pleased with using the CentriFlow Meter due to the cleanliness, ease of calibration, and no zero drift.
MATERIAL TEST REPORTS
The CentriFlow Meter can be used to measure finished products such as potato chips, tortilla chips or processed nuts in order to properly season them. The CentriFlow Meter has also been installed in blending applications where multiple products are blended together to manufacture snack mixes.
