**Keywords:** Valve Position Indicator, DeviceNet, Intelligent Valve Position Indicator, Fieldbus Control System **Introduction** In modern industrial automation, control systems monitor and manage devices such as on-off valves and regulating valves through fieldbus technology. This enables not only analog control but also digital control, significantly expanding the application range of fieldbus-based systems. StoneL offers a wide range of valve position indicators with various protection ratings and communication protocols, including AS-i, Modbus, DeviceNet, and Foundation Fieldbus. Additionally, gateways allow integration with other protocols like Profibus and Ethernet. StoneL's valve position indicators are divided into six series: Eclipse, Visual Indicator, Quartz, SolaR, Onxy, and Hawkeye. The compact Eclipse is compatible with ISO-compliant Namur actuators, while the Visual Indicator provides clear visual indication of valve positions up to 75 feet. The Quartz series is ideal for hazardous environments due to its epoxy coating, and the SolaR series is corrosion-resistant, making it suitable for general industrial applications. The Onxy series is designed for corrosive or flame-retardant environments, and the Hawkeye features a fully sealed stainless steel housing and thermoplastic probe for use in fire-rated areas. For the petrochemical industry, StoneL introduced a Foundation Fieldbus (FF) valve position indicator that can be paired with low-power, intrinsically safe solenoid valves. These valves operate at low voltage and current, with an explosion-proof rating of Eexia IIC T6, allowing up to 16 valve position indicators to be connected on a single bus, reducing wiring complexity and saving time and cost. At Changzhou Chemical Plant, a PVC silo control system utilizes 28 DeviceNet-enabled SolaR intelligent valve position indicators. The system uses an OMRON C200HG controller, with a C200HW-DRM21-V1 master station connecting all 28 devices via a 4-wire trunk network for remote monitoring and control. **DeviceNet Bus Functionality** DeviceNet supports up to 63 devices on a single network and can interface directly with popular PLCs such as Allen-Bradley, GE, and OMRON. It allows both simple digital and complex analog devices to be connected using a two-wire power supply and data line, forming a 4-wire bus. Designed for use in hazardous environments, DeviceNet effectively reduces noise and ensures reliable performance in industrial settings. **General Purpose with DeviceNet (SolaR Series)** The SolaR series includes two digital inputs for valve position detection, two 24V DC digital outputs for solenoid valve control, and a two-wire analog input (8-bit resolution) for 4–20mA meters. Communication baud rates can be set to 125k, 250k, or 500k, depending on system requirements. **Changzhou Chemical Plant PVC Silo Control System Overview** The system manages four silos—TK-1-1, TK-1-2, TK-3-1, and TK-3-2—for storing PVC powder from different production units. Valves UV-6, UV-13, UV-20, and UV-27 serve as feed valves, while UV-21, UV-28, UV-23, and UV-26 act as discharge valves. Additional valves control air blowing and mixing processes. **Control Logic** Feed control groups silos into two sets. When the material level is within normal limits, the system initiates a blow-mixing cycle. If the level is outside the acceptable range, an alarm is triggered. Discharge valves are manually operated, and the system prevents simultaneous opening of multiple valves to avoid errors. **PID and Manual Control** Air pressure is controlled via PID, with adjustable parameters and manual/auto switches. The user interface displays process views, flowcharts, material level trends, pressure curves, and parameter settings. **Hardware Configuration** The system uses an OMRON C200HG PLC with a NT631 touch screen. Key modules include a 16-point digital input card, a 16-point digital output card, an 8-channel analog input module, a dual-loop PID module, and a DeviceNet master. **Application Results** Using DeviceNet reduced cabling costs by 30–40%, saving approximately 70,000 RMB in materials and labor. PLC hardware savings amounted to 10,800 RMB. Overall, the project saved 80,800 RMB, representing a 40% reduction in costs. Construction time was also significantly reduced, improving efficiency during factory commissioning. **Conclusion** The implementation of DeviceNet-based valve position indicators has proven to be safe, reliable, and cost-effective. Maintenance has been nearly eliminated, ensuring smooth operation and contributing to the plant’s economic success.

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