Biggest obstacle one faces in migrating to newer system

Saffa · Mar 12, 2021

And to add to the above, if it's a big step change like my project was, a complete code rewrite is a good idea. We implemented improvements we'd been wanting for years, but which were too challenging in the old Quantum ladder logic.

I have done another SLC500 to Schneider M340 conversion using their code conversion tool, and as others have said... do not rely on that to get you a good end result. What it did for us was allow the plant to be swapped over and operational in a single day, but for future proofing we rewrote a lot of the code from ladder into FBD.

Yacineg · Mar 12, 2021

Saffa said:
A written methodology statement is a great tool for making you fully think through each step, and for allowing others to check your thought process. Plus, when the client signs off on it then there's shared responsibility to make it work.

I did a wastewater pumping station PLC upgrade from a modicon Quantum 534 to a M580 hot standby. The station overflows in 90 seconds at peak flow if no pumps are running (4000L/s rated flow). We had about 5 minutes at normal flows though, so every part of the job had to be planned with the possibility that we'd need to pull the pin and stop work if a storm event occurred, so we had to be able to have 10 pumps operational by the end of each day.

My methodology statement was about 70 pages long, down to the detail of "move wire labeled 30034 to terminal T34. Enable level sensor LIT301 in new PLC. Uncomment MOV instruction #56 to copy value back to Quantum."

It took about 3 weeks to write and plan it, and about the same amount of time to move over all the wires to new terminal blocks, 1 at a time, keeping as much operational at any one time as possible. My colleague did all the code, I did the wiring. The plant manager came down for a look-see after day 2 and nearly had a heart attack when he saw what the PLC panel looked like. I think he thought it would stay a birds nest once we were finished!

This would be possible if you have a fully documented system. Many times we are called in when everything goes south & expecting to get the system up & running in an hour.

Saffa · Mar 12, 2021

I agree, that's for when it's a planned job rather than a breakdown. All bets are off when the system is broken.

We've done the same approach for completely undocumented systems. Essentially the planning stage is the documentation stage.

We try and guide clients down the path of doing this kind of work before it turns into a breakdown situation. Not always successful of course.

Biggest obstacle one faces in migrating to newer system

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Yacineg

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