Migrating Legacy PLC-5s to DeltaV

Way back in the mid-1980’s, when I was a newly-minted engineer working oil & gas production projects offshore in the Gulf of Mexico, a new series of PLCs came on the scene to replace the Allen-Bradley PLC-2’s we had been using. They were the PLC-5 series.

Now, more than 30 years old, the CPUs used in these PLCs were placed into end of life status which meant no further factory support for the CPUs as well as a recommendation to migrate 1771 I/O cards. I caught up with Emerson’s Javier DeLuna about the choices that have to be considered moving forward.

Manufacturers and producers face options whether to modernize to a newer family of PLC or move the I/O and logic to a distributed control system (DCS), such as the DeltaV system. For many users with PLCs and DCSs, the ongoing challenge has been to maintain two databases, keep expertise and skills to manage the systems, and stock sets of spares for each system.

Modernizing the PLC to the next generation with a conversion rack solution has some issues. The swing arms for the I/O is covered by a metal plate which prevents access from maintenance person and create a loss of around 250 I/O. There is a possibility of damaging field wiring since this wiring must be pushed inward 3 inches and be repositioned to work properly. Increase equipment depth and additional migration cables also may mean the equipment and cabinet could require modification and moved cable trays—creating additional expense.

Emerson’s DeltaV team developed a quick switchover solution with the swing-arms in the same position as the legacy 1771 I/O chassis. This solution fits in the same space as this chassis with six DeltaV mounting kits also available.

DeltaV quick switchover for Allen-Bradley 1771 I/O16-channel DeltaV signal conditioning cards are available for the most popular non-isolated I/O types including digital input (DI) and digital output (DO) at 120VAC and 24VDC, as well as 4-20mA analog input (AI) singled-ended cards. These DI/DO signal conditioning cards connect to 32-channel DeltaV DI/DO cards where one DeltaV card replaces two PLC-5 cards. The AI signal conditioning cards connect to a 16-channel DeltaV AI card for a one-to-one replacement. The DeltaV signal conditioning cards connect via a standard ribbon cable to the DeltaV mass-connection I/O terminal block.

This modernization path also means a single DeltaV database to maintain a system-wide function block language. A web-based PLC-5 analysis tool helps estimate the cost and effort required to migrate the PLC logic.

Now with this 1771 I/O solution combined with a DeltaV PK Controller, users are able to tackle their PLC obsolescence in a very holistic way. The PK Controller brings both a standalone or an integrated approach to meet users’ preferences on their automation strategy, while still bringing the power of the DeltaV system. This is true for small form-factor solutions requiring under 100 I/O to full DeltaV integrated solutions with thousands of I/O.

Contact your local sales office or Emerson Impact Partner for more on the capabilities and delivery times on this modernization solution or visit the Modernization & Migration section on Emerson.com. You can also connect and interact with other modernization and DeltaV experts in the Services group and DeltaV forum in the Emerson Exchange 365 community.

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