One of the key issues impacting decisions of industrial modernization and upgrade is downtime. Few industrial plants can withstand the extended downtime required for modernization of control architecture and I/O. Nowhere is this truer than in utilities such as water plants.
An important water treatment plant in Canada serving more than 100,000 people provides a case in point. The facility could withstand short periods of manual control, but major outages were very difficult. At the same time, the plant was running on legacy hardware so out-of-date it was at risk for catastrophic failure, to say nothing of the unavailability of parts. The costs for maintaining uptime as well as the risk of downtime became the two driving factors in the modernization decision.
The water plant employed 4 disparate obsolete 90-70 control systems with no plant redundancy, increasing the potential for a serious failure. They used a SCADA system they were happy with, radio communications to 9 different PLCs over serial, and 79 Genius blocks throughout the facility.
To meet the absolute requirement for minimal downtime, Emerson and partner GESCAN Automation used a phased approach to upgrade. In phase 1, the intention was to convert multiple 90-70s to a single PACSystemsTM RX3i controller plus a redundant system. Phase 2 would convert all the extremely obsolete 90-70 I/O, and phase 3 would convert the Genius blocks to PROFINET.
Phase 1 was able to effect minimal downtime by converting small groups of 90-70s even within the phase as the figure below shows. Code conversion was accomplished automatically through the Machine Edition software.
This allowed the changeover to be accomplished in about a day, and due to the phased approach, caused very little downtime. In a matter of days, the system went from multiple disparate 90-70s to a single Simplex 90-70 to a single RX3i control system to redundant RX3is, while maintaining constant water supply.
In phase 2, the 90-70 I/O was converted to RX3i, which was accomplished by means of a conversion rack of the same form factor as the 90-70 I/O. It allowed switchover without rewiring allowing a single rack upgrade in thirty minutes. All five racks were converted the next day.
Phase 3, conversion of the Genius blocks, is an ongoing project with very little impact on plant operation.
While the total modernization could have happened even faster if the plant had shut down, the need for zero downtime guided all decisions. As it was, the plant accomplished a simple and yet unique and elegant upgrade with fast implementation and absolutely minimal downtime – the driving factor in industrial modernization.
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More information on PACSystems can be found on the Emerson website.