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Critical Path and Governor Shutdown
Definition of Critical Path SD and Governor SD

First of all, let me tell you the events that lead to my question...

On an LM2500+ that had a T48 overtemp emergency SD, also a Critical Path SD and a Governor SD signal arouse. The main issue is that the T48 overtemp SD is categorized as a FSWM SD (Fast stop with motoring) which enables the turbine to perform a high speed crank to cool down and avoid an engine lock out. But the governor SD and critical path SD, which are triggered by the initial overtemp, are FSLO SDs (Fast stop lock-out) so the unit is not allowed to crank and therefore enters in a 4-hour lockout.

I tried to understand the PLC logic and all I see is that the critical path SD is triggered by other external SDs that are considered critical (overtemp, engine stall, overspeed, etc.). But i really don't know what the meaning and purpouse of this critical path SDs are and why are they different from the initial SD cause.

I hope i am being clear enough, any help on how this SD logic works will be really appreciated! Thank you!