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 ...