Controls and process applications can be restored

Restoration possible: Many distributed control systems (DCSs) are rapidly aging and risk breaking down. Luckily, there are many tools and innovative methods for supporting and breathing new life into controls and process applications

By Jim Montague

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To solve these problems and replace the old DCS, GTEC sought help from system integrator Bachelor Controls Inc. in Sabetha, Kan., and together they implemented PlantPAx process automation system and ControlLogix PLCs from Rockwell Automation, and minimized costs by retaining all existing field wiring and devices and reverse engineering control logic and strategies from the old DCS.

Read Also: Advanced Process Control Ain't Easy

The migration was completed during two, scheduled, four-day shutdowns. The first included installation of one ControlLogix controller, Ethernet and ControlNet communications and FactoryTalk View supervisory HMI software. The second involved the complete plant switchover with BCI replacing GTEC's outdated I/O racks for more than 800 I/O points spread throughout the plant, installing the remaining ControlLogix PACs, and checking that each I/O point responded correctly to controller commands.

Restart procedures began on the morning of the fifth day, and Hill reports that downtime and maintenance were greatly reduced. "There are some months that we operate with zero downtime," says Hill.

In addition, PlantPAx also helped GTEC install a new production line for grain-neutral spirits. "We just tied in the new I/O, downloaded the necessary programming to the FactoryTalk View SE software and ControlLogix controllers, and double-checked the I/O points for each valve and input," says Marvin Coker, BCI's senior project engineer. As a result, GTEC has expanded its production capacity by 75%, and is now able to manufacture 35 million gallons of industrial and beverage-quality ethanol per year.

Educate and Execute

Meanwhile, Plaskett reports the Benicia's refinery's migration to Experion began with I/O realignment, including an "A cluster," covering the refinery's upstream instruments and controls, and a "B cluster," covering its blending and other operations.

"More than 2000 points were moved and rebuilt," says Plaskett. "With movement of I/O comes deleting and rebuilding of points, meaning internal IDs changed, and all references needed to be cleaned up. With only one LCN in the beginning, DOC 4000 Express worked fairly well to allow us to identify and cleanup references.

However, we also used—and I would advise doing it—a homegrown cross-reference (XREF) utility based on the Find Names utility, which allowed us to find even indirection references that we also use at Benicia. We also learned it's easiest to do this before Experion is placed on top because priming for the Experion layer is also required."

Following some in-depth training and hands-on practice, the Benecia refinery's engineers and operators set up a testing system to explore the relationship between their LCN and Experion to gain more application-specific knowledge. In addition, because a critical part of any Experion system is the configuration of the fault-tolerant Ethernet (FTE) network, Plaskett added that Valero's engineers also secured help from Honeywell Network Services to set up a hot-standby router protocol (HSRP) in a redundant configuration.

"Using our test system, we were able to conduct extensive testing of switch shutdowns, router shutdowns and FTE cable disconnects," explains Plaskett. "The testing pointed out the need to carefully check operating systems on these network devices and to test, test and test for proper operation."

The detailed design also included an enterprise model database (EMDB), as well as three clusters, A, B and OM, with redundant servers on top of each individual LCN to allow future expansion. Also, each cluster would have its own subnet address, and these would be tied together with redundant routers, allowing for reliable DSA communications, as well as protected access to/from upper-levels plant networks.

To get its actual execution moving, Benecia's engineers decided to start with their graphics conversion. "We had an extensive set of operating graphics and wanted to retain the operators' familiarity with their layout and reduce their learning curve by continuing to use our 20 years of good graphics," says Plaskett. "By interviewing, visiting and getting proposals from several vendors, we found one that had shape libraries and navigation tools that met the ASM-like look and feel we wanted to give the operators, while also being able to take our existing graphic layouts and convert them efficiently to HMIWeb graphics. For this project, we decided to convert only our primary control graphics, which included 165 for A, 195 for B and 42 for OM, which adds up to 402 graphics that were converted and migrated out of 3000 total NW displays. My advice here is that, if you have a good set of DCS graphics, don't change them too radically during upgrade projects. And, for us, though ASM-type graphics are good for handling upsets, they're extremely bland for normal monitoring by operators."

Flexible Tools = Easier Migrations

One of the primary forces aiding DCS migrations these days is more capable software and hardware that can adapt more easily to legacy systems and allow more old I/O points and other devices to continue to run in updated environments.

For example, Tsb Sugar recently decided to consolidate automation and data assets at its 18-year-old Komati Mill in Komatipoort, South Africa, and planned to migrate from its old DCS to a control system combining PLCs, SCADA and even its manufacturing execution system (MES) into a one, overall information server. This would allow Komati to measure and optimize throughput, evaluate stoppages and downtime, predict final volumes, and provide device-layer and area-level bookings to Tsb's reporting layer. However, this plan required renovating and/or integrating new Quantum PLCs, legacy Provox and DeltaV DCSs, LIMS database, and SAP enterprise resource planning (ERP) systems into one data and reporting point. As a result, Tsb and system integrator Control Systems Integration (CSI) implemented ArchestrA System Platform and Wonderware InTouch SCADA/HMI, historian and MES Performance software from Invensys Operations Management South Africa. The plant also adopted AutoSave change management software from MDT Software and Top Server OPC solution from Software Toolbox to connect the PLCs to Komati's new systems.

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