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Powder & Bulk Solids, June 2018

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CaseStudy 32 J u n e 2 0 1 8 I Automated Grinding System for Seed Facility It isn't unusual, in fact it is commonplace, for seed to be treated with pesticide, fertilizer, and other things that will aid in the growth of the plant and its harvest yield. Some treatments require process- ing of raw ingredients from a granular material in specific proportions that are then batched and attached to the seed downstream in the process. This article summarizes one such application. There are two granular raw materials. Both are dosed into a fine grinding machine at specific rates and proportions. Included in the process control and automation system for this grinding and clas- sifying system: • Two bulk bag unloading systems with surge bin and loss-in-weight feeder • One flexible screw conveyor with surge hopper • One fine grinder • One existing filter receiver • One existing silo • One HMI/PLC control panel • One VFD/starter control panel While it is typical that the automation vendor, Sterling Systems & Controls Inc. in this case, pro- vides the mechanical equipment on systems ap- plications, in this application only the design and manufacture of the two automation system con- trol panels (the HMI/PLC control panel and the VFD/starter control panel) was provided. Sterling Systems is a UL listed control panel manufacturer certified for the U.S. and Canada. HMI/PLC Control Panel & System Operation It is important that the automation supplier un- derstand the process, not just the control technol- ogy. In this application Sterling Systems worked with the supplier of the mechanical equipment, Prater Industries, to make sure the mechanical equipment would do the job required by the seed processing customer. Sterling Systems designed and manufactured the HMI/PLC control panel as required, customized to do the specific job that was needed. The main operator interface for this system is via an Allen Bradley PanelView 10-in. industrial touchscreen HMI, and an Allen Bradley PLC, mounted in an enclosure running a custom designed process control application by the auto- mation supplier. The HMI/PLC control panel and PanelView HMI provide all control and equipment status information necessary to run the automated process control system. Each piece of equipment has a virtual M-O-A switch in the HMI. Placing all switches in the M (manual) mode allows the system to be operated manually. All switches must be in the A (auto- matic) for automated operation. The operator will use the HMI to select one of five previously stored sets of parameters to run. Each set of stored pa- rameters contains the following data points: • RM#1 speed setpoint (%) • RM#1 agitator speed setpoint (%) • RM#2 speed setpoint (%) • RM#2 agitator speed setpoint (%) • target fine grinder load (amps) • fine grinder high amps (amps) • fine grinder low amps (amps) • filter receiver discharge airlock speed setpoint (%) • filter receiver fan high amps (amps) • filter receiver fan low amps (amps) • fine grinder speed (%) • fine grinder feeder airlock speed (%) After placing all switches in automatic, the opera- tor will then press the start button on the panel. The start button will flash during startup. The sys- tem will verify that the material level in the exist- ing silo level is not indicating a high level condition in the silo. If a high level condition is present, the system will generate an alarm and will not start. Next, the silo blower will be started and confirmed running. While the silo blower is running, the system will monitor for silo blower low pressure. If the silo blower low pressure sensor indicates a low pressure for longer than a programmable NFPA tolerance check

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