Performed a comprehensive fault tree analysis to validate the reliability of backup utility systems supporting energized-to-trip (ETT) Safety Instrumented Functions at a 267 kpph TBHP production facility. The study evaluated electrical backup systems including 4160/120 VAC and 120/24 VDC power, generators, diesel-powered firewater systems, 2oo3 voting chemical injection pumps, and nitrogen supplies for valve actuation. Developed a detailed FTA model incorporating over 350 gate functions to verify availability of critical utilities following total power failure. Served as principal SIS consultant and authored the final analysis report.