Our Mark-IV control system of GE Gas turbine having logic forcing issue as Id Code which is require to force the logic have been disable since 2017 in all the three unit of G.E Mark-IV control system. Even though Id Code is very much correct, and same Id Code have been used since commission 1990. What might be the cause of not accepting the Id Code? And is there any solution for this issue?
If your Mark IV was commissioned in 1990, it was one of the newer Mark IV panels, and it may have been supplied with some user-configurable parameters. And, even if it wasn't, I believe it was possible to change the USER ID. So, even if you believe the password hasn't changed, it's very possible it was inadvertently changed by someone.
Unfortunately, I believe to change the password you need to know the Master Password, or at least the current password. I don't have access to the Mark IV Maintenance Manual, I believe it is GEK-83883 (but I may be wrong--it's been a LONG time), but I believe there instructions in that manual for changing the password.
I will attempt to find my copy of the Mark IV manual over the weekend and see if I can find any more information.
But, I've never heard of this problem. I believe the information is stored in non-volatile RAM. I guess, in thinking about the non-volatile RAM thing, it's possible that if the "right" card were replaced the password might be "changed" without anyone being aware of the "change." Or, if there are Diagnostic Alarms related to memory chips that might be related to the "changed" or lost password.
Hope this helps!