For our second plant installation, we were told that we didn’t need to go through that same process. Supposedly, with advanced diagnostics, we could shoot our networks and scan them before we hung the instrumentation. After hanging the instruments, we could scan the network again and compare the noise levels, power draws and the health of the network.
I wasn’t convinced this would work. I do know that installation practices have a significant effect on the quality of communication. So we were very careful to install our system perfectly. We installed the first four segments and did all the initial checks: we walked down all the bricks, walked down all the terminations, did the resistance and capacitance checks, conducted a manual scope sweep, and we checked each instrument with a handheld configurator. Then we used the ADM to validate all of that information—and it matched perfectly.
The Advanced Diagnostic Monitor
During checkout, the ADM even detected a problem on one of our bricks that the handheld configurator did not catch. It was over-terminated, but not to the extent that it violated the minimum point where Foundation fieldbus wouldn’t run. We still had a running system. We weren’t getting any communication errors, yet the network was deemed unhealthy by the ADM. We had failed to turn off the built-in terminating resistor on one of the bricks. My confidence in advanced diagnostics was starting to grow.
The next system we brought on-line had eight segments. This time we made sure that the terminators were right and the trunk cables were terminated correctly. After we determined that the segments were good, I used the advanced diagnostic monitor to commission all eight segments. It took only 20 minutes and actually found two problems that my field technicians missed―one where they forgot to turn on the termination at the end of the segment trunk, and another where the polarity was reversed. The errors were corrected in ten minutes, and the segments were back up online and completely healthy.
After that, we hung 40 instruments on the segments and used only the diagnostic system to validate. Not one had a problem. In fact, even our longest run―1500 feet―came on line with no problem as quickly and as easily as the run that was five feet from the cabinet.
Currently we have six different areas in my facility where we’ve installed Foundation fieldbus using the High-Power Trunk concept. We’ve stopped using the handheld, and we no longer haul the oscilloscope out to the field. Once the system is installed, I do the sweep remotely, and we are ready to go. I have total confidence in the ADM.
Even More Features
The diagnostic system also provides a commissioning wizard, alarming and data logging, and a built-in oscilloscope for displaying in-depth detail of fieldbus signals. Once all the instrumentation is on the network, the software allows me to enter the tag names for each node address manually on a particular segment. During troubleshooting, it’s easy to see which instrument has the problem without ever going out into the field. The commissioning wizard is very easy to use and very intuitive.
The diagnostics feature is equally reliable. It measures device signal level, proper termination and cable continuity. It provides a baseline report and comprehensive system documentation. The baseline is continuously compared against actual values and if there’s a problem, it tells me exactly what the problem is, indicates possible causes and then offers possible solutions. Best of all, I’ve never had to go out into the field to diagnose a problem.
The physical layer diagnostic module captures snapshots of all values and can store that data for up to two years for long-term trending. Because it has the ability to create a visual representation of the digital fieldbus communications coming from the control room, it truly provides an “extra set of eyes” on communications, making you aware of a problem before it arises. As a matter of fact, we were having trouble with a valve, and the manufacturer tried to tell me that it was because I had an unhealthy network. I showed him some of the screen shots from the software—he’s never mentioned the health of my network again.
Another neat feature of the system is the remote software. When I commission the segments, I do it remotely, from the comfort of my office. I don’t need to be out in the field fumbling with my laptop. I can monitor the network remotely—even when I’m at home.
We’ve never had any issues or compatibility problems with any of our vendor’s fieldbus products. We have Endress + Hauser, Emerson Rosemont, Yokogawa, SMAR, and all of it is plug-and-play.
The amount of time that we’ve saved with advanced diagnostics has been dramatic. It actually takes longer to walk down the system to set the jumper switches and the boxes than it does to commission the system. The physical walk down and commissioning for the first, four-segment system took a day and a half; on the following eight-segment the physical walk down took about 60 minutes, and the commissioning took a mere 20 minutes. Our confidence level in the network also increased dramatically. When the ADM certifies that the system was good, we know it is good.
From Incident-Based Maintenance to Predictive Maintenance
Advanced diagnostics has enabled me to go from incident-based maintenance to predictive maintenance. When you have a chemical plant running 24/7, and an instrument failure of any kind will bring your operation to a halt, you need a communication system that you can rely on. You need one with greater power capacity, signal quality, consistency, and efficiency. The ADM- FISCO combination delivered on every requirement. It simply outclassed every other product that we used previously.