A Review of The Final Turbine Inspection Report at the Lahendong Geothermal Power Plant

Abstract

In this paper, the author employs a review method based on the results of a turbine inspection conducted by the maintenance service unit of PT Indonesia Power in 2023. The review presents a comprehensive evaluation of the condition of rotor blades in the steam turbine of the Lahendong Unit 1 Geothermal Power Plant. The objective of this study is to assess the material integrity through a series of non-destructive testing (NDT) methods, as part of the Remaining Life Assesment (RLA) of the turbine components. The inspection included visual inspection, magnetic particle inspection (MPI), ultrasonic flaw testing, penetrant testing, in-situ metallography, hardness testing, as well as XRD and XRF analysis. Significant findings include pitting corrosion, rubbing, material loss, water droplet erosion, and cracks in several rotor stages. Microstructural analysis revealed the presence of martensite, retained austenite, and carbides, with indications of cavities along grain boundaries that have progressed to directional oriented cavities and even microcracks. Based on Neubauer’s classification, several blades have reached stage 4 and 5 (end of life), indicating substantial degradation. These findings provide a strong technical basis for predictive maintenance strategies and re-blading decisions in the next overhaul.