Upgrading Legacy Control Systems

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Owners of old Bailey Controls (now part of ABB) systems can also update via a software upgrade. Citect, an HMI/SCADA software vendor, has taken legacy Bailey DCSs owners under its wing, and offers an easy-to-implement upgrade path. "Citect has a lot of experience changing-out Bailey systems," says Brooke Mauro, services and partner channel development manager at Citect. "Customers can continue to use I/O and Bailey Infi 90 controllers, but they get the latest operator interface computer equipment and software."


Nufarm, an agricultural and specialty chemical manufacturer in Melbourne, Australia, used Citect to upgrade its Infi 90 system. "We needed to integrate all our plant data into one standard, easy to use interface," says Tuan Truong, Nufarm's project coordinator.


Nufarm just added a Citect HMI/SCADA software system to its existing Bailey DCS, and avoided any disruption to plant operations. "The system is a huge improvement in terms of presentation, user friendliness, control functionality, robustness, data exchange, data storage, remote access and support," says Truong.


Look around at the HMI/SCADA vendors to see if you can just buy a plug-in package. Prices start at less than $1,000, and systems are available from leading software vendors such as Citect, Wonderware, Intellution, Iconics, InduSoft and several others.



As noted, many processors have a significant investment in I/O, field instrumentation, PLCs, cabinets, controllers and other hardware that continues to work just fine. Therefore, the next step along the upgrade path is to keep as much of it as possible and upgrade or replace only what you must.


Before starting any upgrade project, Foxboro/Invensys checks the old I/O to be sure it is up to the task. "In 99.9% of the cases, we find no corrosion present and no need to rip out cabinets or wiring," says Betty Naylor-McDevitt, director of migration at Invensys. "This is due in part to the fact that many older legacy systems required installation in clean environments. The wiring and infrastructure installed in such environments will last virtually forever. So, when it comes to wiring and fixtures, we say - if it ain't broke, don't fix it."


Joel Young, vice president of engineering at Digi International, Minnetonka, Minn., says that adding connectivity to legacy systems is a big part of Digi's business. "We make it possible to extend the life of existing systems with only an incremental investment," explains Young. "We provide a path by which connectivity can still be used as other components get replaced."


Young describes a system Digi installed at ChevronTexaco: "Chevron needed to integrate 200 of its Square D SyNet PLCs with Wonderware software via Ethernet. The existing PLCs used a proprietary system that required a specialized PC board. To further complicate the issue, the PLCs were no longer in production and were not Ethernet compatible."


What to do? Replacing 200 PLCs would be extremely costly. Besides, the PLCs were performing their control tasks admirably. The old technology just couldn't talk to the new HMI.


Digi connected the legacy PLCs to the HMI PC with its off-the-shelf RealPort communications module, so that Chevron could continue operations with no changes.


Schneider Electric has an interesting way of upgrading an old network. "Install a Telemecanique Momentum PLC that can translate other vendors' network protocols," advises Joe Eiden, segment manager at Schneider. Once the Telemechanique PLC gains access to the legacy network, you can take advantage of its built-in web server, XML programming and other languages to integrate it to higher-level systems.


Step Two: New HMIs

If you are working with a "modern" HMI/SCADA system that's more than a few years old, it's probably running on obsolete PC hardware and a dated Windows operating system (OS). These old technologies are unable to access web servers or more current Windows-based architectures, such as .Net and OPC. Virtually every HMI/SCADA package has an update for its own software, and some vendors offer software that can update other suppliers' applications. Wonderware, for example, can update old Intellution iFix or FIX32 HMI/SCADA systems.


When upgrading to a new Windows-based control software package, however, it is best to start from scratch with a new PC and current Windows OS. Trying to upgrade an old PC and its OS is frustrating, fraught with problems and not worth either the time or money. At today's prices it's much easier just to buy a whole new computer system.


The situation is likely to be the same with obsolete HMI hardware. Throw it out and install new. For example, thousands of Allen-Bradley PanelView HMI terminals exist in the control world, and many are getting long in the tooth. Rockwell offers an HMI upgrade path featuring its current PanelView Plus terminals.


You can also replace them with software and a PC. InduSoft's (Austin, Texas) Import Tool for PanelBuilder converts existing applications from PanelBuilder 32 to WebStudio, and then runs them on any PC, Panel PC, PDA or embedded display. Not only do the old PanelBuilder HMI displays work the same as before (See Figure 2), the new HMI software provides all the advantages of a modern Windows architecture.


Step Three: Update Control Processors

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