An alarm segment is a segment in a chain from trigger to risk. Alarm segments are used for evidence-based alarming ...
Alarm segments may be obtained by single-step FMEA. Each segment is a simple connection from a prior hazard (or a trigger) to a hazard (or a risk) resulting from the first hazard.
Assume a safety-critical system with a boiler. When the boiler is too hot, the system is facing a hazard and is at risk. The boiler might become too hot if the thermostat is stuck on, or if there is a shortage, bypassing the thermostat.
In this example we have two triggers: Tr1: thermostat stuck on and Tr2: shortage bypassing the thermostat. The alarm segments are:
If there is evidence that the boiler is hot, then we can conclude by the algorithm that the system is at risk, but we cannot determine which of the triggers is responsible for the situation.
Updated on 26 Mar 2017.