VOTING LOGIC AND DEGRADATION

[zamyusuf]

Good day all,

I'm working as Vendor-DCS Engineer and I'm still learning.. I want to ask regarding degradation voting logic which made me confuse to understand,
what is the meaning by degradation by voting logic?
for example, if I had voting logic 1oo2, what is the degradation logic of it?

Thank and Regard,

 

[danw2]

explanation here:
aLink

 

[Channing]

I assume it to mean that the voting mechanism is degraded when one or more of the components fails (or detects a fault) and moves to a safe (open) state. For example, a Safety Instrumented Function (SIF) is considered to be in a degraded state when one of the sensors in a 2oo3 fails. It places "stress" on the system and must be repaired or replaced within a defined period of time called the Mean Time to Restoration (MTTR). Otherwise, your safety system is non-compliant in the context of the standards that define function safety.