Friday, November 21, 2008

Upgrading of PLC

The author is currently working in captive power plant. PLC 2/30 is currently installed in boiler controls for starting, stopping and FSSS controls of boiler. It is also communicating with DCS mod 300. As DCS is being replaced by our instrumentation guys with latest DCS in market, we're also thinking in going for upgrading/replacement with new PLC.

My query is whether we can go for upgrading to PLC5 series on same 1771 platform so that existing backplanes can be used. This will reduce my cost also. If yes, what are min. changes to be done? I/O's digital--512. no remote I/Os are there. No additional software change is there.


Posted by Trevor Ousey on 8 November, 2008 - 2:05 am
PLC5 hardware is quite expensive, the processor is at least twice the price of a comparable ControlLogix with reduced features. If you wish to keep the 1771 rack and IO modules, make it a ControlNet rack (or RIO) off of a ControlLogix system. This will give you more flexibility for communication and hardware. We have done this several times with PLC5s and the bonus is you can just go back to the PLC5 if there are problems with your program and you have ran out of commissioning time.

The 1771 hardware is not obsolete, it still has little more life, but
Rockwell will increase the pricing on it to encourage end user to migrate as they have in the past, and have longer deliveries.

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