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 processing of raw ingredients from a granular material in specific proportions, which are then batched and attached to the seed downstream in the process. This processing of raw ingredients often requires a fully automated grinding system to prepare the ingredients for the seed coating.
In this 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 system:
- Two (2) Bulk Bag Unloading Systems w/ Surge Bin and Loss-In-Weight Feeder
- One (1) Flexible Screw Conveyor w/ Surge Hopper
- One (1) Fine Grinder
- One (1) Existing Filter Receiver
- One (1) Existing Silo
- One (1) HMI/PLC Control Panel
- One (1) VFD/Starter Control Panel
While it is very typical that Sterling Systems & Controls, Inc. provides the mechanical equipment on systems applications, in this seed coating grinding system application we provided only the design and manufacture of the two control panels, the HMI/PLC Control Panel, and the VFD/Starter Control Panel. Sterling Systems is a UL Listed control panel manufacturer certified for the USA and Canada.
HMI/PLC Control Panel & System Operation
Sterling Systems & Controls understands the seed coating process, not just simply control technology. We worked with the supplier of the mechanical equipment, our sister company and partner Prater Industries, to make sure the mechanical equipment would do the job required by the customer and we 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” industrial touchscreen HMI, and an Allen Bradley PLC mounted in an enclosure running a custom designed Sterling Systems & Controls grinding system process control application. The HMI/PLC Control Panel and PanelView Component HMI provide all control and equipment status information necessary to run the automated process control system for this seed coating application.
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 (automatic) for automated operation of the grinding system. The operator will use the HMI to select one of five previously stored sets of parameters to run. Each set of stored parameters contains the following data points:
- Raw Material #1 Speed Setpoint (%)
- Raw Material #1 Agitator Speed Setpoint (%)
- Raw Material #2 Speed Setpoint (%)
- Raw Material #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 the Automatic position, the operator will then press the START button on the panel. The START (310.4) button will flash during startup. The system will verify that the material level in the existing 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 time, the system will display a Low Pressure alert on the HMI screen.
The above partially illustrates the customized process control system implemented by Sterling Systems & Controls, Inc.. This includes monitoring and controlling all items listed above to produce the necessary finely ground and blended RM#1 and RM#2 for further use in producing finished and coated seed. The HMI/PLC panel also includes all the weight instruments for the loss-in-weight feeders within the system.
VFD/Starter Control Panel
The VFD/Starter panel encloses the electrical controls required to operate all of the process equipment items. This is a 480VAC panel and includes; a control transformer, VFD’s and motor starters for the bag unloaders, feeders, fine grinder, all airlocks and other process equipment items within the overall system.
While not included in this specific system, Sterling Systems & Controls can interface with a local business system and can also provide a supervisory remote control application if desired. This is called WebCentral™ Supervisory Control. WebCentral™ is a software package that allows corporate users to access the database of a Sterling Systems & Controls, Inc. process control system, such as the seed process equipment mentioned above. This can be used to enter and manage all configurable items remotely using a simple web browser.