TL;DR
High exhaust temperature reduces turbine life and signals an efficiency problem. Check inlet air filtration, fuel control, and thermocouple calibration before adjusting firing temperature.
What you might see
- exhaust thermocouple readings above normal
- turbine efficiency declining
- exhaust temperature spread alarm active
- power output dropping for the same fuel flow
Likely causes
Dirty inlet air filter increasing pressure drop and reducing airflow
Fuel control valve fault delivering more fuel than commanded
Combustor hot spot from a damaged or blocked fuel nozzle
Thermocouple drift giving a falsely high exhaust reading
Required tools
- Thermocouple calibration reference
- Filter differential pressure gauge
- Fuel flow measurement equipment
- LOTO kit
Safety first
- Gas turbines processing hydrocarbon fuel operate with an ignition source continuously. Follow all hot work and hydrocarbon ignition control procedures near the turbine enclosure.
- High exhaust temperature can cause rapid hot section degradation. Do not continue operating above the high-temperature alarm setpoint without a documented engineering decision.
- Turbine enclosures contain high-temperature exhaust surfaces. Wear thermal PPE and confirm the enclosure is cooled before any internal inspection.
Procedure
- 1
Read the exhaust temperature spread across all thermocouples. A high spread indicates a combustor problem; uniform high temperature indicates an air or fuel control issue.[1]
- 2
Check the inlet air filter differential pressure. High pressure drop across the filter reduces airflow.[1]
- 3
Verify the fuel control valve position feedback. A stuck-open or overfeeding fuel valve raises exhaust temperature.
- 4
Compare the exhaust temperature to the power output. Declining output with rising temperature confirms efficiency loss.
- 5
Calibrate the suspect thermocouple against adjacent thermocouples. A single high reading in a uniform spread confirms thermocouple drift.
- 6
If inlet filter differential pressure is high, replace or clean the filter elements per the site filter replacement schedule.
- 7
If the combustor spread is high, plan a combustor inspection at the next maintenance window. Do not run a combustor fault beyond the alarm limit without a documented risk assessment.
Sources
Solar Turbines (Caterpillar) Solar Mars 100 / Titan 130 / Centaur 50 Centrifugal Gas Compressor / Turbine general technical documentation, Solar Turbines (Caterpillar)
Solar Turbines Mars 100 / Titan 130 / Centaur 50 general exhaust temperature diagnosis and combustor procedures (general)
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