Proper monitoring of gas turbine performance deterioration can significantly reduce gas turbine ownership costs. All gas turbines will suffer from performance related faults during operation. Performance deterioration means increased fuel consumption and reduced power output. Higher fuel consumption results in higher operating costs and lower power output can result in lost revenue. Both these effects reduce profitability.

Typical causes of performance deterioration are:

• Fouling
• Compressor and turbine rotor tip clearances
• Variable guide vane problems
• Compressor and turbine Labyrinth seal damage
• Foreign and domestic object damage (FOD & DOD)
• Combustion problems (fuel nozzle and damage to combustion chamber)
• Hot end gas path component damage
• Corrosion problems in gas path components

Compressor fouling is the most common form of performance deterioration and almost all engines suffer from compressor fouling. Although the effect of compressor fouling has been recognised by gas turbine users and compressor washes mitigate fouling, however little has been done to optimise the engine washes. One user estimates the cost of fouling per engine, due to improper cleaning at about 500,000 USD per year.

GPA offers consultancy services analysing the performance deterioration of your engines and highlighting faults at engine component level including compressor fouling. This is achieved by employing component matching and gas path analysis techniques to detect changes in component characteristics. We refer to these changes in characteristics as fault indices. By trending these indices for each gas path component we can highlight performance-related faults at engine component level. The analysis will also trend the loss in power output and increased heat rate due to performance deterioration.

Using the trends for compressor fouling together with the user information for fuel costs, lost revenue and downtime cost we will endeavour to optimise the compressor wash.

Other Services Offered

• Estimate the turbine creep life used during operation. Engines operating at 90% of ISO rated power will result in an increase in creep life by about 5 times that of ISO the rating life. If the ISO rated life is say 25,000 fired hours then operating at 90% power will give a creep life of about 100,000 hours. However engine loads ambient conditions and performance deterioration has a big impact of engine life. In one instance the creep life used was at least a third compared with that quoted by the manufacturer. This estimates to about 175,000 USD per year saving on engine overhaul costs.


• For good measure we will also analyse your combustion system. We shall compare each thermocouple reading in the exhaust gas temperature rake with the expected reading. Any deviation in these respective readings can imply problems with the fuel nozzles (Carbonisation or fuel nozzle becoming loose) and changes in the combustion chamber. Such faults can result in severe damage to the hot end sections and such damage can easily result in repair costs that often exceed 1m USD.


• Investigate instrument faults and highlight those instruments whose readings are suspicious.Based on your engine details, GPA can supply a list of on-line measurements that are needed to carry out the analysis.


• An off-line service where we will predict the emissions from gas turbines using GPA's XEMn modules.

For further information:

E-mail: sales@gpal.co.uk