Operational risk can take many different forms. Continuing to rely on older, obsolete control systems presents one set of downsides. But moving forward to the new and unfamiliar can be risky as well. Sonatrach, the Algerian-based energy company, recently faced just such a dilemma, related Abderahmane Frih, Sonatrach control engineer, in a presentation to fellow process automation professionals from the Europe, Middle East and Africa (EMEA) region at the Honeywell User Group (HUG) meeting, November 4-7, in Nice, France.
At the company's natural gas liquefaction and processing facility on the North African country's western Mediterranean coast, several major pieces of equipment were due for overhaul, and presented an opportunity to overhaul its aging controls infrastructure as well. The plant's 1990s-era Honeywell TPS network had begun to show its age, and the operating system for its Windows XP consoles was scheduled to be unsupported by Microsoft come April, 2014.
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Sonatrach entertained the two paths forward: a full-scale migration to the Experion PKS, complete with new fault-tolerant Ethernet (FTE) network and C300 series controllers; or a more affordable network retrofit that effectively replaced the older Universal Control Network (UCN) with its FTE successor, Enhanced UCN (EUCN), together with new Experion PKS consoles.
From a hardware perspective, the latter approach involved swapping out controller and network interface cards such that all their Network Interface Modules (NIMs) became ENIMs, and their High Performance Managers (HPMs) became EHPMs. Importantly, this approach would allow Sonatrach to begin to leverage new network and HMI technology while preserving the company's investment in control programming and strategy development.
A full migration to Experion, on the other hand, would also have required re-engineering of the underlying code, a risk the company didn't care to take, Frih said. "The re-engineering of our control strategies would have been a more extensive effort entailing a longer shutdown, a longer FAT [factory acceptance test]," Frih said. "So we chose EUCN instead of the full C300 transition," he said.
To execute the transition, Sonatrach entered into a three-year-long Lifecycle Management (LCM) agreement with Honeywell that will also allow the plant some breathing room to plan for longer term evolution. "Cost and downtime were key considerations," Frih said. "This was the lower risk decision."