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Bulk Terminal Controls
Precise Bulk Terminal Controls, Accurate Truck Loadout
Bulk materials such as grain, flour, cement, flyash and fracking sand are either milled on-site or shipped to the bulk terminals in rail cars or trucks. On arrival they are unloaded and stored in silos. Finally the operator loads materials from the silos into trucks for local deliveries. Alternatively, the terminal can handle bagging, blending or batching into other products. The bulk terminal software supervises inventory, selects the silos to be filled, runs the filling conveyors and monitors progress.
In truck delivery terminals, a truck scale under one or several silo discharge points sends data to the control system. Alternatively, the installers mount the whole silo on load cells and it can be used as a legal-for-trade scale. The operator monitors incoming trucks and directs them to discharge into one of the silos. While this process continues, he fills trucks with the desired bulk material weight. The Baker-Hughes terminal in Shafter, near Bakersfield CA is typical. This terminal has 12 silos of 610 tons capacity with three truck scales for truck loadout, each handling 4 silos. Read about it in a World Cement Magazine Editorial.
Control System
The BatchTron bulk terminal controller uses a PLC with a touch screen as the operator interface. It does not need switches or lights since everything is on-screen. This eliminates maintenance issues, and also makes them easy to upgrade. The screen is located at the operator's desk while the PLC is located close by or in a nearby building where most of the motors are located. Consequently, this eliminates long runs of power cable and reduces the control wiring to a single ethernet cable .
When actuators are located in groups at long distances from each other, remote I/O can be positioned in the Motor Control Center or around the plant. As a result, wiring and cost are reduced.
Variable Frequency Drives control the speeds of the rail car discharge conveyor and the bucket elevator. Conveyor speed and other parameters are all stored in the PLC. They are accessible for editing from the operator’s screen with the appropriate passwords. Other screens display data from the VFDs. Examples are speed and motor current, useful for fault diagnosis.
Truck Loadout and Inventory Control
A PC computer runs the Bulk Terminal Controls version of the BatchLink software which shows the on-hand inventory in each silo. The BatchTron truck loadout control system loads trucks by automatically opening and closing feed gates. This dispenses material into each compartment of the truck as required. The truck scales transmit weight values to the control system.
The filling system proceeds automatically. When complete, the operator prints the delivery ticket and the software updates both the customer and inventory records.
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Since rail deliveries may not have the convenience of a local rail scale, the operator in these cases must take deliveries at face value. However, the SiloWeigh.Net silo inventory system can verify the deliveries to their respective silos. The operator updates on-hand inventory values to correct any errors. An Internet connection makes service and training possible whenever it is necessary.
Camera System
A multiple camera system monitors incoming and outgoing vehicles. Likewise, it monitors the rail car discharge and bucket elevator discharge to the various silos. In addition, the operators use it to guide trucks under the filling socks in the silos by mobile radio
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The latest camera models transmit data digitally via ethernet cable and ethernet switches at junction points throughout the plant. The operator can zoom-in the large screen display on any camera for detail views. A separate PC computer handles this operation, with a separate link via the Internet for service and updates.
This view shows the bulk material control console on left. The inventory and SiloWeigh.Net computer are on its right, the camera display at top and scale indicators and ticket printers at lower right.
Silo Inventory
Silo inventory is calculated from deliveries minus the truck loading amounts. The SiloWeigh.Net system can be installed on all silos to further monitor actual silo loading as a cross-check on the calculated values
6 to 8 sensors are installed on the walls of each 25 ft diameter skirted silo. As a result, readings of the weight are stable to within 2% of full scale. The local PC computer allows the operator to view two screens. One shows the SiloWeigh.Net, display, giving the levels in the silos or a history trend graph, as seen at right. The other shows the inventory and truck shipments, plus the weight values from the truck scales.
