Ethylene production (500MM tpy) facility in Quatar. Petrochemical site's Hot and Cold Flares systems were scope of the project. What complicated the solution was that there were eight (8) global scenarios that had to be evaluated for their over-load contributions, namely: Global cooling water and power failure scenarios Both mass and radiant flows were issues Both Hot and Cold Flares had limiting capacities Required a comprehensive event tree model to quantifiably determine overall SIL requirements of main flare capacity contributors. Supported as HIPPS and event tree calculation study principal consultant and report author.