Chemical Processing - May 2008 - (Page 42)

>> making it work ily quashed a high alarm that was a nuisance due to a field issue without suppressing a critical low alarm; this wasn’t possible with the old system where suppression took place at the tag level instead of at the individual alarm level. We’ve also added alarm suppress/ re-enable when certain equipment is out of service. A pop-up faceplate allows operators to auto-suppress hand-chosen alarms via calculation blocks built into control modules. Hysteresis adjustments have permitted us to provide a larger dead band on some alarms, which also has eliminated some nuisance alarms. The system promises additional benefits in the future. For instance, we’re considering eliminating an AspenTech DMC platform on the acetonitrile unit and incorporating its functions within a DeltaV PredictPro model-predictive-control package to cut the costs of five PCs and an annual maintenance contract. We’re also considering opting for a safety instrumented system integrated with the DCS for new construction. Our Triconex system works well but is a separate platform that required substantial serial communications configuration into the new system during the recent conversion. a better approach Looking back over our conversion experience, I don’t think I’d ever want to convert a process automation system for a critical unit as large as ours if it were not running. Trying to start up, troubleshoot and tune hundreds of loops all at once would be a nightmare. Our approach has other advantages as well. Separating a hot conversion effort into HMI and controller-I/O phases enables operations and maintenance staff to become comfortable with the replacement automation’s HMI without concern about controllers and I/O. Personnel prefer to adjust in small bites to many minor graphical differences. Typical might be the new system’s Auto and Cascade positions for switches versus the old system’s Auto and Manual. Later, personnel can focus on process logic changes while controllers and I/O are converted without, at the same time, being overwhelmed by a new HMI. CP Eric Schnipke is a controls engineer for Ineos Nitriles, Lima, Ohio. E-mail him at eric.schnipke@innovene.com. ColdWaveTM Refrigerated Dryers wring the nasty oily water out of compressed air systems to deliver pure, clean, dry compressed air to your air-powered operations. Equipment lasts longer and you will keep productivity high and energy use low - saving you money and making a small contribution to reducing global warming. Specify ColdWaveTM Refrigerated Dryers and weather those hot, humid dog days of summer. Hankison_ColdWave.indd 1 42 • May 2008 www.chemicalprocessing.com 4/30/2008 10:14:29 AM http://www.hankisoninl.com/coldwave http://www.hankisoninl.com/coldwave http://www.chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing - May 2008

From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor WirelessHART signals a change at plants Avoid costly fabrication mistakes Watch out with variable speed pumping Hot cutover boosts control system migration Plant InSites Process Puzzler Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - May 2008

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