How to Pick the Right Remote Terminal Unit (RTU) in the Utilities Industry

In the gas industry, safety, precision, and reliability aren't just important—they are non-negotiable. Choosing the right Remote Terminal Unit (RTU) is critical in ensuring that operations run smoothly, data is managed accurately, and stringent safety regulations are met. Based on my experience and insight into the industry's needs, here are the key criteria for selecting an RTU tailored for gas industry applications.

Hazardous Location Rating

The RTU must be specifically rated for hazardous environments, particularly for natural gas applications, classified as Class 1 Division 2, Group D. This classification, outlined by the National Electric Code (NEC) and International Electrotechnical Commission (IEC), ensures the RTU can safely operate in environments where flammable gases or vapors could be present, especially under abnormal conditions. This rating protects both personnel and infrastructure from risks such as ignition or explosions, which are especially critical in gas processing and distribution facilities.

Environmental Durability

Operations in the gas industry are often subject to extreme weather conditions. It's essential that the RTU can withstand:

• Cold Temperature Ratings: The unit must function reliably in subzero conditions—down to -30°F, which is vital for regions with harsh winters.
   
• High Temperature Ratings: The RTU should endure high temperatures, up to 150°F, ensuring performance stability during heatwaves or in environments like compressor stations.

Additionally, it’s important that the RTU can be installed without additional climate control systems, saving costs and reducing complexity, especially in remote locations.

Field Replaceable Internal Battery

In remote areas, quick and easy maintenance is key to ensuring operational continuity. A field replaceable internal battery allows field personnel to replace the battery on-site, reducing downtime without requiring specialized tools or equipment. This feature improves system uptime, enhances long-term reliability, and supports operations in geographically isolated areas.

On-Board Datalogging and Memory

Modern RTUs must have robust data logging capabilities. This is crucial for tracking performance, maintaining accurate records, and ensuring regulatory compliance. Look for:

• On-Board Storage: The RTU should include sufficient internal memory to store critical data locally, ensuring continued operation during communication outages.
   
• External Storage Options: Support for external storage devices, such as USB drives or SD cards, allows for increased data capacity and redundancy, making it easier to archive long-term data and integrate with backup systems.

Comprehensive Communication Ports

Connectivity is everything in industrial operations. An RTU needs to support:

• RS485 Serial Ports: For long-distance communication and multiple device connections.
   
• RS232 Serial Port: To interface with legacy systems.
   
• RJ45 Ethernet Port: For high-speed networking and integration with modern control systems.
   
• USB Programming Port: A USB B or USB C port simplifies firmware updates and configuration tasks.

These diverse ports ensure that the RTU is compatible with both current and future technologies, providing flexibility and scalability.

Diverse Communication Protocols

To ensure seamless data exchange and system integration, the RTU should support multiple communication protocols, such as:

• Modbus RTU Serial (RS232, RS485) and Modbus TCP/IP Ethernet: Widely used for reliable data communication in industrial environments.
   
• DNP3 Serial (RS232, RS485) and DNP3 TCP/IP Ethernet: Essential for secure telemetry and SCADA applications.
   
• HART Protocol: For advanced diagnostics and integration with smart instrumentation.
   
• NTP (Network Time Protocol): Critical for maintaining synchronized time across systems, ensuring accurate data logging and operational coordination.

By supporting these protocols, the RTU guarantees broad compatibility with various devices, ensuring both current and future scalability.

User-Friendly Programming

User accessibility and ease of use are key for RTUs, as they streamline configuration, monitoring, and maintenance tasks. Look for:

• Customizable Programming Compliant with IEC 61131-3 Standards: This standard offers flexibility by allowing RTUs to be programmed using widely recognized languages like Ladder Logic and Structured Text, making it easier to tailor the RTU to specific operational needs.
   
• No-Cost Programming Environment License: Many RTUs come with proprietary software, but these often come with high upfront costs or recurring fees. Choosing an RTU with a free or no-cost programming environment eliminates these financial barriers and is especially beneficial for smaller companies looking for cost-effective solutions without sacrificing functionality.

Vendor-Supported Software Modules

Vendor-maintained software ensures that your RTU is reliable, secure, and compliant with industry standards. Key modules to consider:

• AGA Flow Calculation and Audit Trail Software (Compliant with API Standard 21.1): This software is critical for accurately measuring and tracking gas flow, which is essential for billing, regulatory compliance, and operational efficiency. Compliance with API Standard 21.1 guarantees adherence to industry best practices.
   
• Proportional-Integral-Derivative (PID) Control Software: PID control ensures real-time adjustments to process parameters, optimizing performance and maintaining stability in critical systems like pressure and flow control.

Vendor-maintained software ensures your RTU system remains up to date with the latest advancements, security patches, and regulatory updates, all while improving performance and reliability.

Conclusion

When selecting the right RTU, it's crucial to balance operational needs, environmental considerations, and future scalability. By prioritizing safety ratings, durability, communication capabilities, and ease of programming, gas industry operators can ensure more seamless integration, enhanced efficiency, and long-term reliability. These criteria serve as a practical guide for decision-makers, helping them choose an RTU that meets their operational goals and adheres to the high standards the gas industry demands.

Manav Mittal is a seasoned project management expert specializing in automation within the utility, oil, and gas industries. With over nine years of experience, Manav has honed his skills in delivering multi-million-dollar projects with exceptional precision and efficiency. He is happy to discuss RTU selection directly.