By John Rezabek, Contributing Editor
Unless you’ve been living under a rock for the last 20 years, surely you're familiar with the Nike ad campaign that admonishes us to "just do it." One way to interpret the underlying theme is that we're being told to "stop procrastinating and begin your rigorous physical regimen. You'll thank me later." If one takes the advice, sweating ensues and after some energy-drink infusion, one eventually becomes the new physically fit warrior, just like the ones we pass on the way to work huffing and puffing through their early-morning runs.
I too would like to "just do it," but somehow I "just don't."
When you read about other users exploiting their intelligent devices' capabilities, such as HART "Plant of the Year" Mitsubishi Chemicals Ethylene plant in Kashima, Japan, do they seem like those intrepid physical-fitness warriors? Do you think "Gee must be nice," but then allow your instrument department to become "couch potatoes" when it comes to getting value from the intelligent devices in your facility? Maybe you've rationalized that an entrenched "union mentality" will portray these newer tools as about as appetizing as a high-fiber tofu shake. Or maybe you feel that it's someone else's purview – the reliability engineer, perhaps – to lead the effort and secure the needed funding. Yeah, and I'm still waiting for Jillian and my new personal chef to show up and get me back in 36-inch waistline jeans. Jillian, are you reading this?
You know, you may just be "the biggest loser." Sure Mitsubishi's ethylene plant might have another engineer or two free to devote his or her energies to the cause of maximizing the value of device diagnostics. They are doing some impressive things, even developing their own diagnostics for pH measurements. They make extensive use of DP cell plugged-line diagnostics and can cite a number of instances where the alert helped prevent, for example, an untimely trip of an ethylene reactor. That's some big money. Even the most fast-tracked short-timer MBA-imbued plant manager—the one you pass biking in his spandex tights on your way into the plant—can appreciate the value in that. The more measurement and control accuracy and reliability impact the bottom line, the easier the sale. As many have noted, the most elegant advanced control is only as good as the associated measurements and control valves. If undetected stiction is preventing your control valves from doing even one pull-up, the vexing effect on advanced control schemes may persist for years.
This year our site decided that all new DP cells in flow applications and even gauge pressure transmitters would be purchased with the diagnostics option, which includes plugged-line detection. I've had enough winters where critical measurements, like boiler feedwater flow or steam header pressures, have frozen up and caused mass confusion or even unit outages. We have a plan and management support for finally getting some value from our smart devices. You can too.
Stranded diagnostics? Wireless appendages (thumbs, knobs, corn cobs, etc.) are cropping up all over. ABB, Emerson, Endress+Hauser and Pepperl+Fuchs all have one. The idea driving them is this: A device whose diagnostics you can't view with your ancient legacy DCS or PLC can have a radio affixed and data relayed via a WirelessHART gateway to your waiting asset management system.
But wait, there's more. If you have one of about a dozen or so common control systems, you can wire up some multiplexors with surprising ease. You may have to wait for a unit outage, but Pepperl+Fuchs and MTL offer muxes that mount on near-direct-replacement field termination assemblies customized for a variety of DCSs and PLCs. The P+F/Elcon product fit our Triconex ESD system perfectly, and a single electrician was able to change out about 6 AI cards—192 pairs, including 24-V power distribution and RS-485 network—per 10-hour shift. Zero errors. If your plant outage is years off, the WirelessHART radios may be the way to go, but you'll still need to take each device out of service briefly to connect the radio. Maybe the very brave can co-terminate a couple wires in a field device without interrupting the 4-20 mA signal, but who wants to risk it?
If you have smart instrumentation in your facility, the time is at hand to get some value from it. You may be quite amazed by what you find, from valves that haven't gone to their requested positions in years to transmitters that are freezing or overheated. Why let another week slip by with all your smart devices asleep on the couch? Just do it—you'll thank me later.
