ROOFING SHINGLE MANUFACTURING: Andesite Granules Flow Measurement and Control
PROCESS PREDICAMENTS
A manufacturer of roofing shingles needed to accurately control the flow rate and total of various roofing granules (andesite granules) that they were batch blending into a variety of recipes for the different shingle colors that they manufactured. The customer was having quality control issues with the color blends and was finding that there were color variations within different batches of the same color shingle. In order to achieve a more consistent shingle color across different batches of shingles. The customer wanted to be able to control the flow rate and the batch total of each individual granule color coming out of their respective silos. The flow rate and batch size of the granules would change depending on the shingle color and thus, the granule recipe that went into that color of shingle. Each color of andesite granule was stored in separate silos and the customer wanted to be able to call forth a recipe and have the correct amount of each color granule be dispensed from the silos. The product would discharge onto a belt that would feed the granules into a day bin where they would be stored until needed for a production run of that shingle color. The feeder needed to be able to dose individual granule colors at varying flow rates from 5,000 lb/hr up to 100,000 lb/hr, depending on the shingle color/recipe blend. The feeder also needed to maintain its accuracy across the entire flow range without calibration or accuracy drift, regardless of the batch size.
EASTERN INSTRUMENTS SOLUTION
The customer installed a series of CentriFeeder ICV units, one under each silo. The units selected for installation were CentriFeeder ICV-06 feeders with integrated control valves. The feeders each had a local color, touchscreen HMI that displayed flow rate and total. The setpoint for both flow rate and total could be entered via the local display, or sent down to the feeder from a PLC. Depending on the recipe selected, the batches could be as short as 30 seconds, to as long as several minutes.
CONCLUSIONS
Once the CentriFeeders were installed and the calibration was completed, the feeders performed well within the desired measurement accuracy of +/-0.25% over the full range of the feeder and had a batching accuracy of within +/-0.50%. The accurate and consistent batching of the various CentriFeeders ensured that the customer could depend on the quality of the color blend for each of the differnet color shingle recipes and that the color would remain constant and consistent even over various batches of the same color shingle. This tight control over the batch blending operation allowed for major savings in materials as well as a more consistently manufactured product.
MATERIAL TEST REPORTS: Roofing Shingles and Supplies
A variety of CentriFlow Meters have been used in the production of shingles, in order to measure the various components of the shingles as the shingles are being manufactured. They have even been installed in locations measuring the load-out as these components are loaded into trucks and rail cars.
