Expert advice on remote telemetry units

Q&A with Matthew Hawkridge, Chief Technology Officer at Ovarro. He tackles a series of questions about remote telemetry units (RTUs) and reveals how they allow engineers to better understand critical, complex pieces of equipment.

Where are RTUs used in industrial processes?

RTUs are widely used in the industrial sector for process automation and control as part of a supervisory control and data acquisition (SCADA) system. Effectively, RTUs are mini-computers that collect data locally, act upon it immediately and report securely to the central control room, whilst maintaining a local historical store as an additional backup. 

Although RTUs were traditionally used to monitor and control remote field devices, they are now routinely specified for industrial processes as engineering, operations and planning teams gain a better understanding of their benefits. In these applications, the RTU connects to a plant control room or SCADA, providing a low latency response to changing process conditions as well as performing data filtering. They ensure that only key, critical information is passed securely via the narrow communications links, minimising data throughput but maximising useful information received. 

How are RTUs different to sensors?

The move to ‘digitisation’ in industrial processes means that, historically, sensors were used to collect information. However, as good as sensors are at improving efficiency and assisting the move to automation, they only offer a partial solution and they ignore key problem areas with data collection and information management. RTUs are specifically designed to address these limitations - RTUs gather data locally, analyse it, act upon it and report the resulting information to the control centre. 

In many cases, especially for large industrial processes, communications can be limited, irregular, or simply unreliable. RTUs solve this by being able to store information indefinitely, until it is required. Each piece of information is plotted against a timeline, so that engineers can understand the state of an asset at a given point. That means being able to look back in time to spot anomalies or trends. In simple terms, RTUs ensure that there are no gaps in information, allowing engineers to drive efficiency and reduce maintenance budgets in complex manufacturing and industrial processes.

How can RTUs help in process control applications?

When it comes to process control, RTUs operate in a very similar way to PLCs. Both are controllers that can have multiple different types of I/O, different communications modules, and programming of processes. This allows them to act without operator intervention.

However, if there is a communications breakdown or a failure of AC power, the RTU will continue to operate and maintain site control. In these situations, algorithms in the RTU allow it to act autonomously, keeping the production process running. Data extracted from assets can be stored in the cloud, analysed using customized embedded algorithms and data analytics to identify problems before they cause equipment down time. 

With the RTU acting as the site co-ordinator and maintaining a full history of events, engineers have a better understanding of the site conditions both in a live environment and historically.

What are the advantages of an RTU over a PLC?

The single biggest advantage of an RTU compared to a PLC is that the environmental robustness of the former makes it the stand-out choice for demanding industrial and manufacturing applications.

That means RTUs can be used in localities with extreme climatic temperatures and/or remote locations that are off the power grid. For instance, Kingfisher RTUs have been selected as high availability process controllers with extensive communications capabilities for sites with temperatures ranging from -40°C to 85°C. Their resilient and secure nature, combined with independent communications links, redundant power supplies and redundant process controllers make them an extremely robust solution in these applications.

Again, RTUs can perform autonomous control in real time and then report to SCADA that it has everything under control. Engineers at the SCADA interface can ‘supervise’ the operations by setting new KPIs (Set Points) or updating instructions (open/close this, start/stop that, for example) for RTUs to then act upon and manage locally. 

What are the benefits of ‘information’ gathered by RTUs?

Information gathered, analysed and interpreted by RTUs provides the operator with the tools to improve efficiency, safety and maintenance costs as well as reducing shutdowns or fines due to environmental and safety incidents. Achieving these goals requires RTUs to collect additional data points from a vast range of equipment. For instance, new data points may replace manual dips tests to verify the accuracy of primary level sensors, track product density to ensure that the right product is in the right vessel or monitor product temperatures, inert gas blanket supply and pump vibration. 

There are benefits for engineers overseeing remote sites that are vulnerable to theft and vandalism, too. Deploying a suite of RTUs for the monitoring of equipment ensures a cost-effective and safe way to protect physical assets at these locations. The opportunity list is virtually endless. 

How do RTUs facilitate edge computing?

Edge computing is usually associated with the first data server in the cloud network that receives information from a range of machines. In theory, the edge server allows for a faster response to changing events. If you consider that between the local, cabled communications network on site, the global fibre optic networks that link data centres, and the radio or 4G/LTE connection between your site and data centres, the weak link is the connection to the machine. 

Of all the pathways that your data must traverse, the connection to the machine is the one most likely to fail, and servers sitting in data centres are on the wrong side of that link. It is the RTU that sits at the true edge of your control system, gathering information, providing local, low latency control, and protecting your assets, irrespective of communications connectivity.

Are RTUs cyber secure?

Until relatively recently, industrial networks were isolated from IT networks, however, now they are deeply interconnected and as such need to be robust against cyberattacks. As a result, RTUs need to incorporate a range of security measures such as: Firewall SSL (authentication & encryption), HTTP, FTPS & SFTP, SMTPS and open VPN. Auditing should be carried out regularly according to IEC 62443 4 2 and ISO 27019. 

What are the key features of an RTU?

The key features needed in an RTU are security and resilience to the site environment, an ability to operate with minimal drain on local power resources and the processing power to perform local control algorithms autonomously. It is also beneficial to have extensive diagnostics capability and a low mean time to repair (MTTR) to reduce the time required for engineer to spend on site, improving both efficiency and personnel safety.

A challenge in remote areas is power supply, which is the reason why the RTU should incorporate intelligent management of power consumption as well as battery or solar power sources.

Can RTUs facilitate IoT?

There has been a considerable improvement in RTU processing power and memory recently, which means they are capable of running and storing data in the most challenging of applications. This increased processing power is helping facilitate the industrial internet of things (IIoT). A significant area of opportunity is the ability of IIoT to create smart assets, even those that are part way through their lifecycle. For example, deploying RTUs with latest processing power on an old asset can turn it into ‘smart’ asset. This helps engineers to make the most of their ageing equipment and reduce lifecycle costs.