A remote terminal unit (RTU), also called a remote telemetry unit, is a field device used for remote data acquisition and control.
These units are designed to operate at a distance and under harsh environmental conditions. For example, an oilfield company might use RTUs to manage and monitor the status of oil wells across a large geographic area where wired connectivity is limited. A nuclear power plant, meanwhile, might deploy RTUs in areas that are potentially hazardous for workers.
RTUs collect data from digital sensors and analog equipment and then send this data to centralized systems for processing and analysis. Remote terminal units can also receive commands and execute control actions, but they typically do not feature a human-machine interface (HMI).
Read on to learn more about the role of RTUs in industrial operations, management and maintenance.
How does a remote terminal unit work?
A remote terminal unit connects to central control systems over wired or wireless communications. Data can be sent and received by RTUs, allowing teams to track equipment status and send specific commands as needed.
Key components of a remote terminal unit include:
- Input/output modules that interface with sensors, actuators and meters
- Data acquisition pathways for analog and digital signals
- Communication modules for continuous connections, such as cellular, radio, satellite or Ethernet
- Local capacity for data processing, buffering and alarm handling
In combination, these components enable the transmission of data to SCADA, DCS and cloud platforms, and allow RTUs to execute control commands as needed.
Consider a food processing plant using RTUs to monitor compliance with current good manufacturing processes (CGMPs). Remote terminals enable data collection without direct process interaction, which reduces the risk of accidental contamination.
If an issue is detected, RTUs can alert production staff. Based on the severity of the issue, teams can issue commands that enable the unit to slow or stop production.
Common applications of RTUs in industrial environments
RTUs can be used in many industrial environments. Because of their rugged nature and robust connectivity, they are typically used in areas that are difficult to reach, dangerous for staff or are a significant distance from primary production locations.
Some common applications of RTUs include:
- Manufacturing plants with remote assets: RTUs are often used in large plants or campuses with remote assets, such as underground equipment or machinery located in satellite buildings. This allows the collection of data from disparate sources in real-time.
- Pump stations, substations and compressor stations: Utility providers may leverage RTUs to connect multiple stations and substations across a large network of critical machinery.
- Distributed MRO and facility monitoring functions: Distributed maintenance, repair and operations (MRO) initiatives and facility monitoring functions both benefit from RTUs. For example, a company with multiple MRO sites each holding different components and parts can integrate RTUs for up-to-date recordkeeping and stock monitoring.
RTUs and SCADA systems
Supervisory control and data acquisition (SCADA) systems are the primary receivers of RTU data.
Think of SCADA RTUs as the edge computing devices of SCADA networks. Much like their IT counterparts, these edge devices are capable of data ingestion and operation at a distance. In conjunction with centralized SCADA controls, these terminals enable:
- The collection of real-time operational data
- The distribution of this data across HMI dashboards
- The use of alarms, alerts and trend analysis to spot and solve problems
- The application of remote diagnostic and control processes
- The reduction of on-site personnel requirements
While RTUs aren’t essential for SCADA systems to function, these terminals provide additional content and context that enable more effective SCADA operations.
RTU vs. PLC vs. IED—What’s the difference?
RTUs, programmable logic controllers (PLCs) and intelligent electronic devices (IEDs) perform similar functions but fill distinct roles in manufacturing and industrial processes.
RTUs are optimized for remote, low-bandwidth and harsh environments. They emphasize communications and data transmission reliability and are designed to operate for long periods of time without maintenance or upgrading.
PLCs, meanwhile, are optimized for high-speed, local control logic with an emphasis on real-time industrial automation and sequencing. As a result, PLCs are best used for on-site applications where they can be easily monitored and maintained.
IEDs incorporate smart functionality and advanced communication protocols to enable advanced diagnostics and automation. They are similar to RTUs in that they can be deployed in virtually any environment but are more complex to integrate and maintain. Growing areas of adoption for IEDs include power supply and control system management.
As industrial operations evolve to include hybrid devices that combine physical and digital operations, many companies now deploy a combination of RTUs, PLCs and IEDs for maximum asset visibility.
Role of RTUs in maintenance and reliability
RTUs also play a role in maintenance and reliability.
At scale, they offer benefits such as:
- Continuous equipment health monitoring
- Early detection of abnormal conditions
- Reduction in the number and frequency of emergency maintenance calls
- Improved response time to equipment and asset failures
- Data-driven maintenance planning
- Enhanced support for remote control troubleshooting and diagnostics
These remote units also help facilitate the deployment of Industry 4.0 initiatives and the integration of IIoT technologies. RTUs are part of the Industrial Internet of Things (IIoT), and modern RTUs have both the bandwidth and compute capacities needed to act as edge devices across industrial networks.
In addition, RTUs support secure data transmission from legacy assets, which in turn underpins AI-driven analytics of equipment operations data, enabling companies to take proactive maintenance actions. Consider an oilfield RTU that detects a growing temperature differential in a continuously operating well. The unit sends this data to centralized SCADA systems, which in turn send an alert to maintenance teams, who field a technician team to address the issue. The result is minimal, planned downtime and a quick fix instead of unexpected and costly equipment failure.
While IEDs are gaining ground across industrial environments, RTUs still play a critical role in operations monitoring and management. In large part, this is because teams can’t simply rip-and-replace RTUs with IEDs. In the case of on-site power management or alert monitoring, it’s often worth the time and effort to decommission RTUs and connect IEDs with legacy infrastructure. When it comes to remote monitoring stations or hard-to-reach environments, however, the cost of deploying IEDs often outweighs the benefit.
Key benefits of using RTUs
The rugged and reliable nature of RTUs offers multiple benefits for businesses. Some of the most common include:
- Improved visibility into remote assets
- Increased machine uptime and faster maintenance response
- Lower operational and labor costs
- Reduced safety risks due to limited site visits
- Enhanced data accuracy and consistency
- Support for scalable monitoring across multiple, remote locations
Ultimately, RTUs act as the eyes and ears of industrial operations, allowing teams to better track, monitor and manage conditions as they occur.
Implementing RTU-enabled operations
Building an RTU-enabled environment starts with asset management: What devices are currently in use, where are they located and how are they performing?
Once companies know what they have, they can determine if systems are working as intended or if RTU networks require an upgrade or overhaul. Given the growing importance of always-connected Industry 4.0 initiatives, organizations often benefit from a refresh of their current RTU network to ensure devices and connections deliver consistent performance.
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