TL;DR
Compressor fouling reduces airflow and raises heat rate. Perform an online water wash first. If performance does not recover, plan an offline crank wash at the next available outage.
What you might see
- compressor discharge pressure below expected for ambient conditions
- turbine exhaust temperature rising above expected
- fuel flow higher than normal for same output
- heat rate deteriorating over weeks or months
Likely causes
Airborne particulates, hydrocarbons, or salt bonding to compressor blade surfaces reducing effective airfoil camber
Degraded or bypassed inlet air filters allowing higher particle loading
High-humidity coastal or industrial environments accelerating deposit accumulation
Infrequent wash intervals relative to the site contamination level
Required tools
- DCS performance data (CDP, exhaust temperature, heat rate)
- Demineralized water supply for wash system
- Inlet filter differential pressure reading
Safety first
- Online water wash must only be performed within the OEM-specified load range. Injecting at high load risks compressor surge.
- Offline crank wash requires the turbine to be fully shut down and cooled to safe entry temperature before any inspection of the compressor inlet.
Procedure
- 1
Review compressor performance data from the control system: corrected speed, compressor discharge pressure (CDP), and exhaust temperature versus the base-case at the same ambient. A CDP drop of 2% or more confirms fouling.[1]
- 2
Confirm the online wash system is charged with demineralized water and the wash nozzles are not plugged.
- 3
Initiate an online water wash per the plant operating procedure at the prescribed load reduction setpoint.
Warning: Never inject water wash fluid outside the load range specified in the OEM procedure. Over-injection at high load can cause compressor surge or thermal shock. - 4
After the wash cycle is complete, allow the turbine to return to the pre-wash operating point and re-read CDP and heat rate.
- 5
If performance improvement is less than expected, schedule an offline crank wash. This requires shutting down, cooling, and injecting wash solution at crank speed per the OEM procedure.
- 6
Inspect inlet air filters for damage, by-pass leakage, or clogging. Replace filters if differential pressure across the inlet system is above the alarm limit.
- 7
Increase online wash frequency if the contamination rate is high for your site.
Sources
GE Vernova GE 7HA.02 / 7F.05 Gas Turbine (Heavy / Aero) general technical documentation, GE Vernova
Gas turbine compressor fouling, online and offline wash procedures, general power generation references (general)
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