Root Cause Analysis for Gas Turbines

A structured methodology combining fault tree analysis with 5-Why questioning is effective for gas turbines failures. The fault tree maps the physical failure progression through the compressor blades, combustion liners, turbine nozzles, bearings, and fuel system, while 5-Why analysis traces human and organizational causes. This dual approach ensures that both the immediate physical cause and the systemic factors enabling the failure are identified and addressed.

A thorough RCA for a significant gas turbines failure typically requires two to four weeks from failure event to final report. This includes evidence preservation, data gathering, analysis sessions, and corrective action development. Rushing the investigation risks missing latent root causes. Complex failures involving multiple interacting causes may require additional time for laboratory analysis or testing.

Three triggers. First: rising trend on any key measurement (vibration amplitude up 30 percent over six months, wear metals climbing, IR megger declining). Second: a recent repair on the asset — post-repair baseline needs reconfirmation. Third: a process upset that may have exposed the equipment to conditions outside design (overload, contamination, thermal event). Any of the three justifies a 60-90 day check instead of waiting for the next scheduled analysis on failures meeting RCA threshold round.

Physical evidence, time-sequence, hazard chains. For Gas Turbines specifically, the signals to watch are EGT spread, vibration trend, combustor pulsation. A typical Root Cause Analysis report on Gas Turbines reports against the Apollo, 5-Why, fault tree per MIL-STD-1629A framework. Findings tie back to specific failure modes from the Gas Turbines failure population: hot-section component wear, combustor damage, rotor blade fatigue.