Invest now, save later—if, that is, you use the right tools. Though fieldbus instruments and wiring aren’t always less expensive than traditional components, supporters say the true value of fieldbus technologies lies in improving maintenance staff productivity and in adopting predictive maintenance practices to increase uptime.
In his “Digital Fieldbus Solutions” presentation earlier today at Invensys Foxboro’s 2007 User Group Conference, Charlie Piper, Invensys Process Systems Fieldbus Product Manager, explored how field instruments have gone digital, traced the history of Foundation fieldbus, and showed how users can implement device type manager (DTM) and enhanced device description language (EDDL) tools to gain double-digit percentage savings. Piper is product manager on the development teams bringing new InFusion and I/A Series solutions for Foundation fieldbus to market.
“Because instruments can talk digitally, their information can be brought up on a PC by someone who can interact with it,” says Piper. “Every customer I’ve talked with says fieldbus is all about the maintenance and productivity savings they can make. Initial hardware and configuration savings aren’t as important to users as the benefits they get every day by running Foundation fieldbus over the five to 15 years that their applications are running.” Besides allowing users to choose whatever vendor they want for their field device, Piper added, run-time PC-based benefits include aiding in troubleshooting, testing and diagnostics as well as improving uptime and maintenance productivity.
In addition, though fieldbus reportedly can generate 30-35% initial savings on wiring, depending on the number of devices installed, subsequent labor savings in the field are even greater. “We’ve shown that cable savings aren’t so much, but fieldbus can help generate 50% savings on labor in the field,” added Ian Verhappen of MTL Instruments.
Piper explained that 40% of manufacturing costs are maintenance, and that 50% of maintenance is corrective, which is 10 times more costly than preventive maintenance. He added that Foxboro’s I/A Series field management devices simplify preventive maintenance by making it simple to apply Foundation fieldbus.
“Customers should not have to be device experts for commissioning and maintenance; deal with hundreds of parameters in transducer blocks; worry about firmware and device description revisions; and design/configure the user interface to maintain the field device,” said Piper. “Our approach lets customers engineer a device type once and copy it to each instance; off-line engineer a device setup prior to site commissioning; use a new device for the first time in minutes; and replace a failed device in minutes without experts. They also can use traditional device descriptions; use enhanced device descriptions; add UI customization beyond the description; use device vendor DTMs for improved maintenance productivity with graphically rich Windows environments.”
To further improve mix-and-match interoperability, Piper quoted one supporter of Field Device Tool/Device Type Manager (FDT/DTM), who says, “FDT technologies give me the capability to use instruments of my choice, on the DCS of my choice, without loss of functionality.” Piper added that FDT’s applications for diagnostic user interface (UI) include open API standard for plug-in UI applications, can be used for complex devices such as positioners, and enable an infinitely flexible UI with the full power of Windows.
Meanwhile, EDDL can be used for configuration and basic on-line data viewing, and has an open standard for description language. Foundation fieldbus introductions based on EDDL are expected in 2007. In short, EDDs make configuration simpler because the device vendor’s descriptions organize multiple-configuration view screens and menus to open screens, and selects writeable parameters belonging on screens and on-line data screens. However, EDD can’t handle advanced diagnostic UIs, such as valve tests.