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Building from Worker to the Queen

With its Unified Architecture, the venerable industrial open connectivity standard known as OPC can be implemented on non-Microsoft systems, while retaining compatibility with older OPC.

BP Pipelines of North America, in Forest City, Ill., operates a network of pipelines in the United States that transports 450 million barrel-miles of petrochemicals each day. The company’s control center in Tulsa, Okla., is responsible for the transport of oil and natural gas from South-Central and Midwest oil fields to locations nationwide. Last year, management at the Tulsa control center decided to add leak detection to the supervisory control and data acquisition (SCADA) system to monitor pipeline leakage. The SCADA system gathers data from production systems and stores it in a Sybase database that has been modified for real-time applications.

The challenge was to feed process data from the Sybase database to the leak detection system. “We tried for months to find an OPC server that would communicate via ODBC (open database connectivity) to the real-time Sybase product,” says Chuck Amsler, team leader for SCADA applications at BP Pipelines. “It was an older version of ODBC, and we just couldn’t get at the data. None of the applications we tried could do it.”

Amsler turned to Cogent Real-Time Systems in Ontario, Canada, to see if there was a way that the company’s OPC DataHub product could be used to make the connection. He spent a few hours consulting with Cogent’s technical staff and came up with a DataHub script that can support a connection to the SCADA system and queries the Sybase database. Once the process data reached the OPC DataHub, it was just a matter of bridging the data to the leak detection system’s OPC server.

Now, the data flows from the SCADA system to the leak detection system reliably and consistently. “Once we saw how easy it was for the OPC DataHub to make the connection, we decided to use it to log the results,” says Amsler. “With Cogent’s help, we wrote another script to transfer the leak detection calculations back to an Oracle database for eventual reuse by the SCADA system.” On the Oracle side, the OPC script allows Amsler’s team to modify the logging process even while the system is running.

For 10 years, OPC has offered open connectivity from automation to enterprise systems. OPC originally stood for OLE for process control, based on a Microsoft Corp. technology called object linking and embeddng. Over the past decade, though the OLE name has faded away, OPC technology has gained importance as data sharing has become even more important. So has the need to connect devices and applications from a variety of vendors. Just like the printer driver that allows a wide range of applications to interface with a printer, OPC is the driver installed on computers to help software applications interface with industrial data sources.

These data sources can include control systems, programmable logic controllers (PLCs), databases, historians, scales, temperature gauges, maintenance systems and more. The recently developed OPC UA (Unified Architecture) takes OPC further into embedded devices and up to enterprise systems, while relying on Web Services rather than Microsoft common object model (COM) and distributed COM (DCOM), which are slipping into legacy status.

OPC comes of age

The sweet spot for OPC is its ability to make a wide range of devices and applications interoperable. “There’s a need for openness, so you’re not bound to one vendor, so data isn’t stuck inside one machine, so data isn’t stuck in the plant,” says Eric Kaczor, product manager for software, at vendor Siemens Energy and Automation Inc., in Alpharetta, Ga. “Customers want to design a system that is not bound to one vendor’s proposal.”

OPC has become the default driver for connecting disparate vendor devices and unlike applications. “The most important thing about OPC is that it’s the standard in the industry,” says Roy Kok, vice president of sales and marketing at Kepware Technologies Inc., a Portland, Maine, supplier of communication software for automation. “It has become the interface to every product on the market, and it allows you to choose best-in-class products.” He notes that there is a huge installed base in OPC. “It’s an extremely successful standard.”

The vendor community has recognized the importance of OPC and has responded by building OPC into its products. “As time goes on, vendors are making their products more solid on OPC. Companies are betting a lot of money on OPC’s ability, and it’s paying off,” says Randy Konder, president of the OPC Training Institute, in Edmonton, Alberta, Canada.

While OPC is not built to connect plant-critical systems, it is being widely used to share non-critical data. “OPC is used with HMI (human-machine interface) mostly to talk with other HMI or controllers. It’s good for connecting to HMI and getting information out to ERP (enterprise resource planning),” says Siemens’ Kaczor. “If you miss a message over OPC, your plant is not going to go down.”

Kondor notes that OPC can be problematic when users bog down with the limits of Microsoft. The problem comes with Microsoft’s authentication requirements. “Sometimes people don’t understand OPC, and thus, it gets a bad rap. Some say they can’t get OPC to work,” says Kondor, of the OPC Training Institute. “Often, that means there is no authentication. That has to do with Windows, not OPC.”

Some vendors use a tunneling method to bypass Microsoft’s authentication limits. “We specialize in data connectivity. Our niche is that we connect OPC to other things across a network through tunneling,” says Bob McIlvride, communications manager at Cogent. “Our product tunnels through firewalls so we can bridge OPC server-to-server.”

OPC UA promise

The OPC Foundation, in Scottsdale, Ariz., has recently created a Unified Architecture that takes the standard beyond traditional OPC. The goal of OPC UA is to replace, modernize and enhance existing OPC-defined interfaces. UA is also leaves Microsoft COM and DCOM behind. This was necessary, because Microsoft has relegated COM and DCOM to legacy status.

The goal of UA was to move OPC to platform independence, so OPC would not be tied to proprietary Microsoft technology. UA takes OPC and makes it available over Web Services and Microsoft .Net. The OPC Foundation has also been working with several automation standards groups such as the Instrumentation, Systems and Automation Society (ISA) and the Machinery Information Management Open Systems Alliance (MIMOSA) to ensure that OPC can allow rich data in complex domain models to be exchanged among independently developed applications.

The result is a complex standard that that can reach deeper into embedded controllers while stretching upward into enterprise systems. “OPC UA is a big undertaking. The idea is to take standard connectivity and move it forward so it’s more than just a Microsoft platform,” says Eric Murphy, senior solutions architect, MatrikonOPC, a division of Matrikon Inc., a provider of industrial intelligence products based in Edmonton, Alberta, Canada. “UA takes data from an embedded controller—from the process control level and other sources—and takes it up to the enterprise level.”

Vendors such as Wonderware, an automation software supplier, are putting a lot of emphasis on UA. “Our focus now is OPC UA. And we will be coming out with products that will make OPC UA happen,” says Rashesh Mody, vice president of HMI and SCADA business at Wonderware, in Lake Forest, Calif. “OPC has become ubiquitous with connectivity. Everybody wants it and everybody now has the drivers.”

While UA is still in draft form, it’s getting tested in the real world. “When will UA roll out? It’s rolling out now,” says Matrikon-OPC’s Murphy. The OPC Foundation announced the release of OPC UA in June 2006. But as noted by Murphy, “the OPC Foundation wants to make sure the UA specifications are correct. But the only way to see if it works is to get it out there.”

One of the selling points of UA is its ability to work with installed OPC. “In the long run, OPC UA will go further than the original OPC,” says John Weber, president of Software Toolbox Inc., an automation software supplier in Matthews, N.C. “UA has a wrapper software, so those with existing OPC DA (Data Access) can move forward.”

OPC UA is a more robust—and more complicated—system than the original OPC. The OPC Foundation notes that the complicated nature of UA is necessary. “The criticism of OPC UA is that it’s complicated. Yes, it’s extremely complicated,” says OPC Foundation President Thomas Burke, “But so are Web Services, so is the MES (manufacturing enterprise system) layer.”

The future for plants points to interoperability. Control engineers are starting to expect easy data sharing between devices and control systems, and between plants and enterprise applications. OPC is becoming the standard that provides the data-sharing connections.

OPC UA was designed take those connections even further. The goal is to make all the applications and devices in automation interoperable. “The control engineers of tomorrow—the ones who are coming out of the universities now—are used to the interoperability of consumer electronics,” says Burke. “They expect this interoperability in the control marketplace.”

Sidebar - What's Sweet about OPC UA?
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