PCs performing real-time control have been "the next big thing" in process automation for decades, but many still doubt their reliability and maintainability. The solution is to use an industrial PC (IPC), which can perform just as well as a DCS or a PLC. What should you look for in an IPC?
"Motherboard design is a key factor in overall IPC reliability," says Joe Ottenhof, the regional manager for Beckhoff Canada. "The motherboard should be designed and built by an automation company specifically for industrial applications. It should have components with higher temperature, shock and vibration ratings than a commercial motherboard; and it should meet or exceed published standards for industrially rated equipment. The use of inherently low-reliability components such as catalytic capacitors should be minimized."
The next component to examine is the data storage device. "The single most unreliable device in any PC, industrial or commercial, is the hard drive. It should be qualified for the device and easily replaced without the use of tools, or the IPC should use non-rotating mass media such as industrial Compact Flash or a solid-state drive," he adds.
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End users also are still apprehensive about lifecycles because PC vendors tend to upgrade their offerings frequently with little concern for application longevity. "Users should ensure that their IPC CPUs come from a manufacturer's embedded list of processors, which is the long-term available subset of CPUs. The user should make certain the manufacturer has a field notification process that provides ample notice of a product's end of life, as well as a succession plan," he concludes.
Though IPCs have yet to be fully accepted for real-time control, process plants have adapted them wholeheartedly as operator interfaces on the plant floor and in the field. But a better solution in many cases is a thin client that can provide most features of an IPC at a much lower cost and in a smaller form factor.
A thin client connects to a PC-based server, and provides the operator with high-speed, two-way access to one or more applications. Because the thin client only provides operator interface with the applications maintained at the server, it requires much less processing power and software maintenance than a PC, and it can provide benefits over and above an IPC.
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"When migrating from IPCs on the plant floor to thin client solutions, usually the first thought is to simply rip and replace, but a more effective solution is to evaluate and implement a thin client architecture to improve workflow," says Tony Baker, PlantPAx characterization and test manager at Rockwell Automation. "Operators are responsible for maintaining visibility and control over an entire plant, and thin clients can provide major simplification in a typical automation system where operators must access multiple PC-based applications."
Baker adds, "Management software allows thin clients to access multiple applications at a single terminal. Access can be managed through Windows Security credentials for individuals/roles, or can be accessed via tabs, similar to those in Internet Explorer. When evaluating thin client solutions, think beyond simple replacement or PCs, and take the opportunity to revisit workflows of plant personnel to improve productivity."
Marc Leroux, who works in global marketing for collaborative production management at ABB, explains, "A pharma customer collected facilities data from several automaton systems in multiple buildings. An employee walked from building to building four times per shift to collect the information. Our .Net-based thin client solution lets the employee automatically collect the data into an Excel spreadsheet, and generate daily reports. He also built a dashboard that he could access from anywhere in the facility, which showed him the values and parameters from each building in real time."