Palletiser cell, 1756-L73S with the L7SP partner, Studio 5000 v33. Our monthly check compares the signature on the Safety tab against the one in the validation binder. This month there is no signature at all and Safety Status says the task has no lock on it. Last month it was locked, with a signature dated from commissioning.
Nobody has edited the safety task as far as I can find. The one online session in the last month was a contractor changing a standard rung for a reject pusher timer, and he says he never went near safety. I compared the safety routines against the archived ACD by eye and they look identical.
So where did the signature go, is it a firmware thing? Not sure if I can just generate a new one and lock it or if this needs to go further than me, could someone explain?
Not firmware, not on the 1756-L73S. Was the safety task locked when the contractor went online, or only signed? And did he do the edit online, or download? A signature on a safety application with the lock off is not protected.
I would just generate a new signature and lock it. If the routines match the archive nothing has changed. Half our machines out in the field have lost a signature at some point.
> Was the safety task locked when the contractor went online, or only signed?
Signed, but I now think not locked. Our commissioning notes say lock, but the safety lock password was in the same folder as the ACD, so somebody may have taken the lock off during a later change and never re-locked. He did a download for the timer, not an online edit, he says.
Then that is where it went. With the lock off, a download deletes the signature, Studio prompts about it, if I remember right an easy prompt to click through. Locked, it would not have let him download without clearing the lock first. So the signature went with the download, and the safety logic itself probably did not change.
Probably is the point. Don't just re-sign, not on a palletiser. Verify the safety task against the validated copy, not by eye: Compare against the archived ACD, safety routines and tags. If it matches, generate a new signature, lock it, and record the signature and date in the validation file with a note why. Then move that lock password out of the ACD folder.
There's a writeup on the lock and signature side here: https://plctr.com/implementing-plc-safety-interlock-systems-in-industrial-environments/
Fair. For a palletiser, compare first.
Ran Compare against the commissioning ACD, still on V33. Safety task identical, only the standard timer preset differs. Generated a new signature, locked the safety application, new signature and date entered in the binder next to the old one with a note about the download.
The safety application was sitting with no lock on it when the contractor did his download, and the signature went with it. In TIA that would have needed the F password too, which is roughly what the lock is here, we just had it sitting with the lock off.
I still don't know who took the lock off it or when. The password moves to the safety engineer today. Thanks garyb.
Retitled for search, it was "signature gone??". Marking solved.