Large Stator/Rotor Eccentricity – A Unit Failure Case Study 1 INTRODUCTION A 120 MW Kaplan unit failed in December 2015. The reason for the failure was the detachement of the tangential keys from the rotor causing damage to the stator core (Fig. 1). To find the root cause a detailed analysis of the data from the database of the installed monitoring system was performed.Fig. 1 TOP: Key that became loose in operation. BOTTOM: Left key is the one found in the rotor hub, right key is the one that hit the stator core. Additionally, after the unit was repaired, vibration and air gap measurements were performed during the commissioning to provide information regarding it’s stability of operation. For this purpose, the portable measurement system CoDiS-PDS1 (Computerized Diagnostic System – Portab

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