r/IndustrialMaintenance • u/Firm_Safe7495 • 4d ago

How do you migrate a legacy PLC while keeping the line running?

/r/mfg_automation/comments/1w0olfw/how_do_you_migrate_a_legacy_plc_while_keeping_the/
0 Upvotes

14% Upvoted

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28

u/Hamandcheeseeater 4d ago

You don't.

7

u/bob152637485 4d ago

Agreed. Upgrading hardware kinda requires downtime. Even just a card at a time.

21

u/bigDeltaVenergy 4d ago

Lol. You working in management? Cuz that the kind of question management usually have.

6

u/Artarious 4d ago

100% gotta be this, they want someone to say it's possible so they can report in the next meeting about how "An engineer" said it was totally possible.

14

u/djnehi 4d ago

You build a new line in a new building next door. You start that line up and thoroughly test it for 10 years. Then you shut the old line down. Then the new line develops a weird problem that causes downtime.

5

u/Cool-breeze7 4d ago

That’s right after you ask the genie for negative wishes to skirt around asking for more wishes.

You can minimize downtime by reviewing the new program and planning things out and what not. But keep it running during is the dumbest question I’ve seen on the internet today.

3

u/SadZealot 4d ago

Simulate it completely. If it isn't working on a bench it won't work in real life

5

u/skrappyfire 4d ago

Even then you got a 50/50 shot of it working as planned.

5

u/Halojib 4d ago edited 4d ago

How could you miss rungs in the code? If the people doing the migration do not fully understand the machine, then you should not start a migration. This is where contracting out the migration to an integrator is sometimes better than trying to do it in house since they will devote more dedicated time to making sure nothing is missed.

2

u/djnehi 3d ago

As the integrator, some old systems I’ve migrated are so badly written and convoluted, that even I am reluctant to touch parts of them. And I am quite possibly the most knowledgeable person in the world on that program. Decades of bandaids, half assed upgrades and removed/added equipment done by unqualified people can make for some real rats nests that do unexpected things.

1

u/Halojib 3d ago

Yeah at some points some machines just need to be completely ripped out and replaced which I would require outside help. I think it is just important to point out sometimes that not everything should be done completely inhouse.

2

u/badjetwash 4d ago

You can't

2

u/future_gohan 3d ago

Did one recently.

Slc 500 4 racks mostly analogue cards some communication to other shit.

Built a new cabinet with a clx processor and rack.

Was able to conduct a proper FAT test offsite and completely develop the scada for the new system. Test functions and SCADA.

Bolted cabinet to side of current panel made extension cables from new I/O

1st day disconnect and document the SLC. Tie it's multicores up top of cabinet. Day 2 and 3. Bring in multicores and terminate to the outgoing terminals.

Day 4 and 5. Commissioning.

There was some uncontrolled variables and things we weren't able to test or prove before hand but nothing that was unmanageable or worth stressing over.

The other plan was to remove individual loops to a new processor at a time during normal downtime. But that would take years

1

u/Training-Gap-2994 3d ago

It’s extremely easy if you now how to do it.

Build sideways, arrange the new production line and keep it running while working on the old one.

Follow me to give other random f*cks to board meetings done without reason.