Online Method for Assessment and Tracking of Wear in Kaplan Turbine Runner Blades Operating Mechanism

Abstract

Kaplan turbines rely on an operating mechanism inside the runner hub to control blade angles. Contact surfaces of the moving parts on these mechanisms are constantly subjected to frictional and contact forces, inflicting wear which can lead to malfunctioning and performance reduction. In this paper, a novel method for wear assessment in individual blade joints of the runner operating mechanism is presented. The technique consists in monitoring blade angles separately during turbine operation through inductive proximity probes mounted on the discharge ring. These angles are contrasted with the operating mechanism positioning data at several instants and the performance of each joint is evaluated. This technique has been implemented on a 92 MW Kaplan turbine. In October 2018, excessive clearances in three blade joints were detected and an inspection was recommended during the next programmed maintenance. The runner hub was later disassembled and all joints inspected, which confirmed those joints had been worn down and were replaced. This result shows that the proposed method can effectively assess clearances on blade joints during operation, providing an early detection method to anticipate mechanism malfunction and incorporate in the Condition-Based Maintenance plan for production optimization.