Maintenance in the Digital Age

Despite some remaining protocol issues and turf wars, digital networks and smart devices are turning maintenance from a tiresome chore into a competitive weapon. Sixty-five billion dollars. No, that’s not the cost of the latest bank bailout.

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It’s the estimated value of the process automation systems worldwide, which, according to ARC Advisory Group Inc., in Dedham, Mass., are near the end of their life cycles. Replacing them should prove to be a golden opportunity for automation users as well as vendors. As ARC sees it, this will provide users with the opportunity to replace older field devices with intelligent digital units and thus begin to capitalize on digital technology’s ability to optimize the health and performance of field assets.

Apart from today’s smart devices, there are three main components of this optimization: the digital networks that facilitate greater communication between devices and systems; the embedded software that takes the devices’ raw data and puts it in standard forms that are readily comprehensible to other systems; and the asset management systems that take the flood of information coming from the plant floor and organize and evaluate it in ways that are meaningful to plant personnel.

The predictive promise

Digital process plant floor networks come in several flavors, with Foundation Fieldbus and Profibus dominating the scene along with the Hart Communication protocol. “Many people think of fieldbuses as a way to save money in installation because they free you from reliance on large quantities of expensive copper wire,” says Carl Henning, deputy director of the Profibus Trade Organization (PTO), Scottsdale, Ariz., the Profibus and Profinet trade organization for the United States. “Yes, that is a benefit, but the real benefits occur during operation because of the maintenance information you can get and use to convert your organization to a predictive instead of a reactive maintenance environment,” Henning adds. “We are enablers for that type of technology, that type of conversion.”

Sure, maintenance has always been acknowledged as important, though in the dull and dutiful way that flossing after meals is acknowledged as an important part of overall hygiene; that is, it’s rarely been viewed as a game changer. Digital technology is altering that scenario.

“I see an increasing number of installations today that are considering moving to fieldbus technology, and the main reason for them to do so is that they really want to tap into the diagnostics information coming from fieldbus devices,” says Bernd Schuessler, business development manager for automation vendor Pepperl+Fuchs Inc., Twinsburg, Ohio. This, says Schuessler, enables them to run their operations more efficiently and identify potential problems before those problems result in work stoppages. “It’s all about keeping production up and running, and eliminating unexpected shutdowns.”

Well, perhaps not all about that. Predictive maintenance can save companies money in other ways as well. Scheussler says studies indicate that nearly two-thirds of maintenance trips to the field are unnecessary. In addition to the labor costs, the expense of unnecessarily replacing healthy devices simply because the maintenance schedule says they should be changed is considerable.

Predictive maintenance also goes beyond devices to encompass the network itself, thanks to tools like Pepperl+Fuchs’ Advanced Diagnostic Module (ADM), which monitors the physical layer of Profibus and Foundation Fieldbus installations, generating documentation for each network segment and alerting users to the nature and location of potential faults.

“With the ADM, we can detect whether you have water ingress on a transmitter so you have time to fix the problem before you lose that device,” explains Schuessler. “We can look at signal form and signal amplitude. We can also look at jitter, which functions like an early warning sign of something happening on the physical layer, and monitor a host of other factors as well.” In short, users can pinpoint network problems before they lead to failure or suboptimal performance at the device level.

Devices under a microscope

Still, these plusses are dwarfed by the benefits of real-time monitoring and management of the devices themselves.

“There are a number of different machine parameters that you can monitor to help determine machine degradation,” says Preston Johnson, segment manager for sound and vibration sales and marketing for automation vendor National Instruments Corp. (NI), of Austin, Texas.

These parameters, says Johnson, include temperature, pressure, flow and vibration, noting that advance warning of the majority of mechanical faults can be obtained through vibration monitoring.

“Temperature can be a very valuable measurement because when a mechanical component begins to degrade, it tends to have more friction, causing temperature to rise. It’s an indicator of machine degradation that tends to show up a little closer to the failure point than vibration, meaning there is less time to react. But temperature can be used to augment vibration monitoring to get a more precise picture of where in the degradation cycle that machine is,” Johnson adds.

You get the picture: precise monitoring of key variables can yield sharply defined snapshots of the health of machines, devices and processes…if you know how to interpret the data, that is. Many of NI’s products, like those of some other leading vendors, help the users in this regard. Indeed, smart digital devices typically have the ability to alert users to the possibility of failure.

Still, making sense of the aggregate of plant data, and drawing actionable conclusions from it, is the job of asset management systems, often referred to as plant asset management or PAM. Available from a number of leading vendors, these systems not only interpret data and present it to the plant’s operators and maintenance staff, they also determine the relative importance of that data, much like the editor of a newspaper determining what gets placed on the front page and what gets tucked away on page 12.

Without this editorial function, operators could be swamped by the flow of information. This hypothetical editor also maintains archives so that it can not only check a device against what it is supposed to do, but also against what it has done in the past. This degree of specificity helps avoid failures, and also allows users to safely modify device operations in order to boost production or achieve other objectives.

The piece missing from this discussion so far is the device-resident software. These are the tools used to present device information in a standardized format. In effect, they tell the asset management system or other systems that the device is speaking a specific language. Without them, asset management would first have to search among an array of possible languages until it found the right one, and then, assuming the system was capable of understanding it, the work of analyzing the information could begin.

Device talk

At the device level, two sets of initials occupy the space—EDDL, which stands for Electronic Device Description Language, and FDT, which represents Field Device Tool. Though relatively little known, these powerful software tools play a vital role in facilitating preventive maintenance and helping to turn digital automation into a nearly plug-and-play affair. They can coexist in the same plant, though proponents of each tend to bristle at the mention of the other.

EDDL has the longest history. It goes back to 1992, when, as DD, or device description, it was launched as an aid to device set-up and diagnosis. Widely adopted, it became an international standard (IEC 61804-2 from the International Electrotechnical Commission) in 2004, when the name EDDL was hung on it. Supported by Profibus, Foundation Fieldbus and Hart, it became nearly ubiquitous. Working quietly in the background, many automation professionals were unaware it existed.

There was a problem, though. In keeping with the general direction of digital automation, many users were asking for greater graphics capability to be embedded in intelligent devices. Enter FDT.

FDT was launched in 2003 by vendors ABB, Endress+Hauser, Invensys, Metso Automation and Siemens, and was officially chartered in Diegem, Belgium, in 2005 as the FDT Group. Its goal is to provide a standardized communication interface between field devices and systems that is independent from the communication protocol and the software environment of either the device or the host system, allowing any device to be accessed from any host through any protocol.

Its backers intended FDT as a complimentary technology; that is, one that would work with existing EDDL applications, but add the beefed-up graphics that users were asking for. This solution, as Germany’s Institute for Information Technology in Mechanical Engineering (ITM) put it, proved “unsatisfactory,” as device makers and automation vendors balked at supporting two dueling standards. In response to this type of feedback, the EDDL Cooperation Team and the FDT Group agreed in 2007 to work together to create Field Device Integration (FDI), a device-level protocol that would bring together and extend the best features of EDDL and FDT.

Meanwhile, in 2006, EDDL launched an updated version of its standard (IEC 61804-3) with enhanced graphics capabilities. The new graphics give device manufacturers considerable control over the content and structure of the display while still ensuring a consistent look from device to device.

“For instance, the device manufacturer decides the display shall contain a button,” supposes Jonas Berge, director of PlantWeb consulting in Singapore, for vendor Emerson Process Management, Austin, Texas. “The system decides the size and color of the button. This way, the device vendor can provide access to all functionality in the device, yet the display from one device to the next is consistent.”

Berge, a strong supporter of EDDL, notes, “EDDL is not only used to put information on the screen, but is also used by device management software to automatically configure an OPC server to make all data from any device available to external software.”

OPC looks ahead

OPC, the open connectivity standard designed to allow devices and software from disparate vendors to communicate with each other, as well as with higher level systems, has not been seen as a key player in the maintenance arena. “Typically, there has not been a lot of asset data, or maintenance information, that is made available through OPC, but that is changing,” says Jim Luth, technical director of the OPC Foundation, Scottsdale, Ariz.

Luth says the vehicle for this is OPC Unified Architecture (UA). “It’s the next generation of the OPC specification, and it allows much richer data constructs and organization of data, and more complicated types of applications, to make use of OPC.” He sees this aiding communication between devices and asset management systems, and enterprise resource planning (ERP) systems as well.

Check out a podcast of Automation World Editor in Chief Gary Mintchell interviewing Emerson’s Jonas Berge about EDDL, at www.automationworld.com/podcast-4816
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