Is Combining SCADA and MES a Good Idea?

Technology convergence is well-known in nearly every sector. We’ve all seen it happen in the consumer tech sector, most notably as our cell phones transformed into smartphones that allow us to make and receive phone calls, visit websites, provide GPS travel directions, conduct video meetings, take high quality photos, and much more.

This kind of convergence happens in the industrial sector too.

A couple of high-profile examples include the programmable automation controller, which extends the capabilities of a programmable logic controller with broader industrial computer capabilities and, more recently, the growing combination of robot and vision technologies to expand and enhance industrial robotic picking and placing.

This combination of existing technologies, particularly in industry, serves two purposes—to extend the capabilities of each technology beyond what each could do on its own and reduce the amount of systems operators or managers need to rely on for information. With respect to the latter purpose, it’s as much a technology consolidation as a combination.

One early example of this can be seen in the evolution of MRP (materials requirement planning) into ERP (enterprise resource planning), as more front office and plant applications were combined with, what was originally, a production planning and scheduling tool.

Now, we’re beginning to hear about the potential of combining MES (manufacturing execution systems) and SCADA (supervisory control and data acquisition) technologies. To learn more, we connected with Sam Russem of Grantek (a system integration firm) for a recent episode of the “Automation World Gets Your Questions Answered” podcast series. We spoke with Russem about this because, not only is he aware of this technology consolidation, he’s worked with manufacturers who have done it.

Differences and overlaps

We began our discussion by focusing on the differences and similarities between MES and SCADA to better understand where these systems are distinctly different and where possibilities for convergence make the most sense.

“Both of these systems are software tools designed to perform a lot of different functions. MES is going to do things like manage your production orders and data relevant to them, analyze some of your raw production data, and turn that into more useful management information like track-and-trace information or summarize raw data into performance KPIs (key performance indicators),” said Russem. “It also needs to communicate in real time to your SCADA systems and work transactionally with business and ERP systems. On the SCADA side, that’s really defined by the ability to connect to plant floor equipment, particularly PLCs, sensors, and other shop floor devices; raw data records [from these devices] are often kept in that SCADA layer. Most importantly, SCADA is where you have the supervisory controls that let your human operators see what’s happening with the plant floor equipment and help to control it.”

Since both systems are focused on device data acquisition and visualization, it helps to view them with respect to the ISA 95 or Purdue Model.

“When you're talking about Level Zero of the Purdue Model, these are physical production processes that happen in real time,” Russem explained. “But up at the Level Four business systems, those are usually operating in terms of weeks and quarters. Therefore, a SCADA system at Level Two needs to be able to communicate a lot faster with PLCs. That’s why it can communicate at sub-second rates. MES works on a slightly longer time scale; it is not usually going to be getting into sub-second level control data, it's more focused on hours, or shifts, or sometimes days or weeks. This difference in speeds affects the protocols that each of those systems use. SCADA needs to be interfacing with industrial protocols like OPC, EtherNet/IP, or Modbus, whereas MES has an even wider range of communication protocols it needs to support because it talks to SCADA systems—usually through OPC or database connections—but also to the business systems through a firewall using web services and other protocols.”

Given these differences in communication speeds, it would be easy to dismiss the possibility of combining MES and SCADA, but Russem noted that the concept of “flattening the stack” helps explain the push toward combining the two systems due to the human interfacing nature of both.

“If you can present your control layer and your management layer in a similar platform in a similar way, where it's kind of seamless between those two functions, there's definitely an opportunity to streamline that human interface,” said Russem. “They're also, of course, both managing your production assets. They're just usually concerned about doing that at different scales. For example, think about the temperature of a batch tank. A SCADA wants to know the temperature of the batch tank tag and it wants to monitor that every second because if it starts to drift in a bad direction, the SCADA system is going to be where you’ll issue your correction and try to bring that temperature back into control. The MES is going to care about the temperature of the tank too, but it likely only cares if it actually went out of spec and it needs to know an exception for future quality review. So, while they’re focused on different aspects, they are both connecting to the same type of data.”

What’s the benefit?

Russem contends that the main driver behind the idea of combining MES and SCADA is, ultimately, about reducing things like license costs and hardware overhead.

Another benefit he noted involves reducing the number of screens and process complexity that operators must deal with daily. “You walk up to these machines and there can be five different screens just to run a single piece of equipment. So, anytime you have an opportunity to streamline operations or bring things to a single control point to make sure that people don't need to be monitoring multiple screens to get the information they need to do their job, there are huge benefits.”

If you can present your control layer and your management layer in a similar platform in a similar way, where it's kind of seamless between those two functions, there's definitely an opportunity to streamline that human interface.

Despite such benefits, Russem does advise caution if you’re thinking of combining MES and SCADA. “A combined MES and SCADA system can require a lot of compute power, as both are heavyweight systems on their own. By putting them all together, you're making a super system and you need to make sure that you have the physical compute power to monitor and maintain them. This is especially important for SCADA because it’s working in real time and is absolutely mission critical. You don't want slow network speeds to affect your ability to actually control your process.”

Real-world application

Referencing a manufacturer who has combined its MES functions into an existing SCADA system, Russem said, “In this plant, they had comprehensive SCADA layer connecting to all their PLCs and it was the main terminal their line operators would use to run material through their process every day. Then they had an MES initiative, and they built that MES using the same SCADA platform. This SCADA system had a set of MES modules that could be added into the platform.”

The system this manufacturer is using is Inductive Automation’s Ignition SCADA with Sepasoft’s MES modules. Sepasoft is a strategic partner of Inductive Automation.

To have all of this within one system was very beneficial to the manufacturer, Russem said, as they developed this system with an agile approach of starting with SCADA and iterating on that over time to add production scheduling, OEE (overall equipment effectiveness), and SPC (statistical process control) to manage their risk at each of those stages.

“The only downside we really saw was that the system got a bit bulkier, and there is a little bit of a risk to the business (as a result),” he said. “As they continue to add more features and more lines [to the system], there might be a place down the road where they're going to need to split that [combined system] into multiple servers to run it; at which point it might actually make sense to kind of split out their MES and the SCADA functions again. I'm not quite sure if we're going to get to that point. But we are looking at a horizon where it could make sense to split those again, and we'll see how it all works out.”