feature | controlling flow Fig. 3. Festo points to these four configurations (valve assemblies and combinations of inputs and outputs) for pneumatically actuated control. Configuration 1 Inputs Configuration 2 Namur Valve Outputs Sensor Box Sensor Box Pneumatic Connections Compressor Valve Terminal | EFFICIENTPLANTMAG.COM Configuration 4 Namur Valve running to the actuator. One of the lines will be pressurized, depending on the desired valve state. This setup also includes one electrical wire to communicate the state of the valve. Inventory: one electrical wire and two controlled pneumatic lines. This system benefits from short runs of electric and pneumatic lines to a local control panel. Configuration 3 uses only a Namur valve and does not provide feedback to the controller. This setup requires one electrical line for control and one connection to the supply air. The advantage of this system is that it does not require a local controller in a panel. It does however, require a potentially long run of electrical wire to communicate with the PLC. Inventory: one electrical wire and one pneumatic connection to the compressed-air line. Configuration 4 uses a valve terminal to control an actuator and two controlled pneumatic lines from a cabinet. This design requires only two pneumatic lines and may be ideal for a hazardous location or in an area where there are concerns that electrical devices may be exposed to excessive water. Potential disadvantages include the run of long pneumatic lines if a local 26 Configuration 3 Valve Terminal controller is not included. Inventory: two controlled pneumatic lines. Determining where the control cabinet will be mounted is critical in each of the four configuration scenarios, i.e., will it be at risk of overheating or require positive ventilation? Different types of enclosures offer different levels of protection. The cabinet manufacturer will provide a rating for environmental resistance based on National Electrical Manufacturers Association (NEMA) standards. PAYBACK Understanding the basics of automating valves puts plant personnel in a better position to operate and maintain these systems. This knowledge takes some of the mystery out of automation and ultimately leads to higher water quality and consistency. EP For more details on automating water processing operations and other applications, standardized control panels, and information on a variety of related support services, visit festo.com. NOVEMBER 2017http://www.festo.com http://www.EFFICIENTPLANTMAG.COM