I was frustrated with break-ins. You plan to complete A, B and C, but ended up working D, E, and F.
I guess that’s working life for ya.
Basically, safety instrumented system is a robust and well-engineered automated logic-solving microprocessors that perform certain functions together with sensing devices and final safety element (mechanical by majority) to prevent safety incident, mitigate consequences of an incident and bring the situation to a safe state. The safety instrumented function can’t completely eliminate the risk, but it will further lowers the probability of an incident and the mitigate the consequences to the situation (plants, building, park, room, etc.)
Ahh-a, I think I got the definition close. Somebody correct me.
1) Mitigating – Fire is detected in a main building. Safety valves on the gas supply pipe to the kitchen shut close to prevent gas feeding into the fire. Deluge valve opens to spray water onto the fire. Alarm rings to alert the people in the building. They evacuated per certain procedure and the person in charge calls the firemen for further action and investigation on the cause of fire.
2) Preventive – Gas supply pipe has a small leak, gas detector picks up the concentration, alarm goes off, damage control team arrives to rectify the small leak and reset the fire & gas system.