During a recent outage, the gas turbine inspectors noticed cracking damage in one of their compressor blades. ETD was requested to or carry out an investigation of cracking damage to this GT compressor blade.
ETD was supplied by the client with one failed compressor blade (cracked) and one compressor blade (un-cracked).
ETD carried out the following work:
- Visual / macroscopic examination of the general surface condition and the cracking damage on the blade samples, including the recording of the blade dimensions;
- Microscopic examination of the general surface condition and the cracking damage in the blade sample. Metallographic sections were prepared, in order to examine the extent of cracking in the damaged areas, as well as the condition of the un-cracked blade to help identify the damage mechanism e.g. fatigue, corrosion, impingement damage etc.;
- Chemical analysis of deposits evident near the fracture surfaces – Energy Dispersive X-Ray (EDX) analysis of deposits was carried out in a Scanning Electron Microscope (SEM).
- Analysis of the base material chemical composition for the compressor blade samples, to determine theactual material constituents;
- Fractographic analysis of the fracture surfaces to identify the damage mechanism, using SEM (Scanning Electron Microscope) coupled with findings of visual examination, optical microscopy and chemical analysis;
- Hardness testing to check the mechanical condition of the compressor blade material;
- Identification of potential causes of the damage and the source of any contaminants that may have contributed to the damage;
- Estimation of the remaining life for the un-cracked blade, using fatigue life assessment according to EN12952 standard. Observations from the other analyses was used to assess the blade material condition and to refine the life assessment results.
- A report was submitted to the client based on the investigation of the cracking damage with photo documentation, including (i) analysis of the risk of continuing to run the GT, and (ii) recommendations for remedial actions to avoid or minimize the risk of damage recurrence to the GT units.
ETD has extensive knowledge and experience of damage mechanisms and failure root cause analysis of components operating in power plants. For more information about ETD’s Failure Analysis services, please click here.