Powder Coated Tough - Fall/Winter 2007 - (Page 29) Powder Recovery Using a PLC to control the powder recovery portion of the system can improve performance in a number of ways. Typically, the recovery system uses a motor-driven fan assembly to draw powder into the recovery system, whether it is a cyclone separator or cartridge collector. The PLC controls the operation of the motor starter, on or off. The on/off status of the motor starter can be made dependent based on additional information collected by the PLC. For instance, a roll online/offline booth can be programmed so that the recovery system is started only when in the online or offline position. If the booth is between positions, the recovery system can not be started. Some recovery systems employ a variable speed drive control to run the fan motor. The PLC can be used to automatPositioning parameters are entered into the PLC through ically adjust the fan speed of the motor the operator interface similar under various conditions. Examples to the zone triggering parameters, although include reducing the fan speed during normally not having negative temporary idle production, or increasing values. This prevents the guns the fan speed for maximum draw during from being in a position that could cause a collision. booth cleaning. The fan speed can also be automatically adjusted to provide a consistent airflow through the booth to compensate for changes in the static pressures of the collection equipment. This also eliminates the need for a mechanical airflow damper assembly on the recovery system. Static pressures on the collection filters can be monitored using pressure transducers that are interfaced to the PLC. Filter pressures can be displayed in a digital format on an operator interface screen, which eliminates needle type gauges. The pulse-down filter With the addition of color touch screens, touch pads, and touch keypads, system operations are enhanced. Operator interface with the day-to-day tasks are automated and displayed on a powder booth status screen for review. This zone triggering screen allows the operator to see active and inactive zones. By assigning active zones to each gun, a gun will only trigger when the product has passed through the respective zone. This allows only the guns needed for a given product to be triggered, which again improves transfer efficiency. Powder Coated Tough 29
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