Analysis of condensor tube thinning distribution and their failure modes based on eddy current data

The condenser in Steam Power Plant is critical equipment to convert steam from the steam output of the low-pressure turbine to become liquid. Thus, maintaining the reliability of the condenser will prevent progressive failure to other equipment. One of the methods to investigate their reliability is using eddy current test on the pure titanium grade 2 condenser tubes to measure their wall thinning level in comparison to their original thickness of 0.5 mm. Based on the measurement, any tubes having 0.05 mm in thickness (wall thinning level of 90%) and below are plugged to prevent potential leakage. In 2018, the condenser in unit 2 of Labuan steam power plant in Banten province, Indonesia was tested by eddy current on all tubes. Results indicate that condenser tube with wall tube thinning ≥ 90% were totaling 733 tubes (± 5% of the total tubes). The location and distribution of the highest probability of tubes leaking due to wall thinning problems were generated after statistical analysis. The data obtained in this unit can be used as a reference for maintenance strategy on other units working in the same condition. In order to understand the tube thinning mechanism, one tube at A-side inlet that has 97% of wall thinning level was cut and submitted to metallography and hardness testing. The results point out that no crack or corrosion product was found and the microstructure of the tubes did not alter as compared to their original tubes. This indicates that pure erosion mechanism takes place causing the thinning of the tubes.