Power Generation Gas Turbines Reliability

Each start-stop cycle imposes thermal stress on hot section components as they heat from ambient to firing temperature and cool back down. The magnitude of thermal stress depends on the rate of temperature change and the temperature differential. Hot restarts cause less damage than cold starts. Factored start counts weight each start type according to its severity. Modern gas turbines may consume 10 to 20 equivalent hours of hot section life per start depending on the start type and firing temperature.

Essential monitoring parameters include corrected power output, corrected heat rate, compressor discharge pressure, exhaust temperature and spread across thermocouples, inlet differential pressure across filters, vibration at all bearing locations, and lube oil condition. For combined cycle units, monitoring should extend to HRSG performance including stack temperature, drum levels, and steam production rates to capture the total system efficiency picture.

Large rotating equipment, NERC bulk power compliance drives three accelerations. Mechanical: load cycling and vibration are higher than design conditions. Chemical: corrosive or particulate exposure attacks seal materials and bearing journals. Thermal: temperature excursions soften lubricants and warp tight clearances. The compound effect on Gas Turbines typically shows up first as EGT spread, vibration trend, combustor pulsation.

Techniques that catch hot-section component wear, combustor damage, rotor blade fatigue earliest are vibration analysis, oil sampling, and infrared thermography. In Power Generation service, the large rotating equipment, NERC bulk power compliance factor often makes a fourth technique valuable — typically ultrasonic for leak detection, MCSA for motor health, or borescope inspection for internal condition. The right mix depends on which specific Power Generation sub-sector and operating mode.