ETD recently completed a project on Investigation of Pitting Damage to Compressor Vanes of 13E2 Gas Turbines.
The following samples were supplied by the client for analysis by ETD:
- Two compressor vanes stage 5 (with pits);
- Particle samples collected from the GT compressor inlet.
The study included:
- Visual / macroscopic examination of the general surface condition and the pitting damage on the samples;
- Microscopic examination of the general surface condition and the pitting damage on the samples. Metallographic sections of the damaged areas were prepared in order to examine the size, shape and roughness of the pits, which helped to differentiate between corrosion pitting and impingement damage;
- Chemical analysis of deposits on the component surfaces and inside the pits – Energy Dispersive X-Ray (EDX) analysis of deposits was carried out in a Scanning Electron Microscope (SEM). This analysis confirmed the presence of any corrosive contaminants such as chlorine and sulphur;
- Chemical analysis of particle samples collected from the GT compressor inlet;
- Identification of the damage mechanism (pitting corrosion or solid or liquid impingement damage) based upon the findings of visual examination, microscopy and chemical analysis;
- Hardness testing to check the mechanical condition of the vane components;
- Identification of potential causes of the damage and, if possible, the source of contaminants that have contributed to the damage;
- A report on the investigation of pitting damage, including (i) analysis of the risk of continuing to run the GT with the observed level of pitting damage on the vanes, and (ii) recommendations for remedial actions that may be possible to avoid or minimize the risk of pitting damage to the GT units.
