Low Pressure Turbine Blades Lifetime Management – Complex Procedure for Monitoring and Evaluation of Blade Condition

The paper describes an application of a complex procedure for monitoring and evaluation of low pressure turbine blade condition. A new procedure for the corrosion pitting inspection of the most endangered parts of low pressure turbine blades is described. Initiated by corrosion pitting, a crack may cause serious damage to the steam turbine blade resulting in its breakaway. Several measurement techniques are applicable for extracted single blades, but no conventional approach for turbine blades in situ inspection is available to date. An advanced 3D scanner combined with complex post-processing process was used to accomplish the task providing a distribution of the corrosion pits on a blade. Blade areas which cannot be 3D-scanned are evaluated by usage of replicas. The second part describes procedure for crack inspection using combination of ET, MT, PT, UT - Rayleigh waves and UT PA. The third part contains description of new formal procedure for deposit sampling from turbine blades which was developed and introduced into operation together with evaluation criteria. Also, particular plants chemistry guides were reviewed to cover all recent operational experience across the fleet. (author)