2018 23 Paper: Third time Lucky -Benmore thrust bearing wipe investigation

Benmore Hydropower Station Six 90MW units totalling 540MW.
In May 2017 one of Benmore’s units wiped its thrust bearing, for the third time in quick succession from the same mystery cause, the repeat bearing failures occurred during tail water depression operation 10-15 minutes from start-up. Each time all the thrust pads were wiped with no damage to the spring beds or other obvious failings. The two previous in-situ repairs were proven unsuccessful by the repeat failures, the decision was made by Meridian to disassemble, remove the rotor and complete a thorough inspection and repair of the unit.
The following paper discusses the, as found condition of the unit, investigations to identify the root causes and combination of root causes to trigger the failure of Benmore Unit 6. Following up with the innovative solutions to resolve the root causes including; in-situ machining of the thrust bracket, uniform distribution of high pressure bearing oil and bearing pad design. The paper also touches on the in-house management of the works and how management confidence was achieved in a collaborative environment to deliver a quality solution.

• Author: Hannah Joslin, Jade Lloyd, Simon Ashton, Steve Taylor
• Exchange: 2018 - Albury AGL
• Company: Meridian Energy
• Topic: Bearing, Francis, Generator
• Key Words: Bearing, Guide, Oil Samples, RCA, Repair, Tail Water depression, Thrust, Thrust Runner, Umbrella, generator