Bearing Accelerated and Representative Testing

Published 29 April 2020

Many components in a wind turbine system rely on rolling element bearings (REBs) to operate. However REBs, including main shaft bearing failure rates (over a 20-year lifetime), can be as high as 30% (Hart et all.,2019). Premature bearing failure is detrimental to the annual energy production and will dramatically increase operations and maintenance costs. At present, the wind energy industry conducts extensive durability tests during the system development process to ensure bearing reliability. However, the industry standard test focuses on a sub-surface fatigue failure and is therefore not representative of operational field conditions of the turbine and does not address the critical premature failure modes that are observed in the wind industry.

The Solution

ORE Catapult are leading an initiative designed to enhance the industry standard wind turbine bearing test procedures. The Bearing Accelerated and Representative Testing (BART) programme is currently under development in collaboration with the Powertrain Research Hub at the University of Sheffield, in addition to a range of other stakeholders who are working on related projects.

With current validation tests during the system development less representative to the actual field operating conditions, BART proposes an alternative methodology. The test practise suggested here will bring critical field operating conditions into the testing environment, allowing for enhanced bearing reliability assessment in the early development stage. This in turn enables the development of 10+MW offshore wind turbines and its components with confidence, contributing to levelised cost of energy reduction with the increased reliability, and fostering UK supply chain growth in this sector.

BART is a long-term technology development roadmap programme comprising a number of sub-project initiatives including:

  • Theoretical Fatigue Life Estimation
  • Field Failure Mechanism Investigation
  • Field Operating Condition Analysis
  • Measurement Technique
  • Damage Detection Technique

These projects are desgined to continuously improve bearing test methods as the industry expands. The programme’s primary focus is currently on on two of the most critical components within the wind turbine system – the pitch bearing and the main shaft bearing. During the BART programme, the failure mechanism and its major factors will be identified and representative bearing test procedure will be designed. As a result, BART will address how to reduce the risk of false brinelling or fretting corrosion.

Process for enhanced test strategy development

ORE Catapult’s Role

In order to replicate these operational conditions during testing, the detailed pitch movement and load information are essential. However, the conventional Load Revolution Distribution (LRD) data from turbine aeroelastic simulations loses these critical details during data processing. The ORE Catapult team has developed a pitch cycle and load analyser code that can capture these details from time-series data, which are then fed into the enhanced pitch bearing test strategy, as described by Figure 1 above.

The enhanced test strategy development for the main shaft bearing is ongoing but will take a similar approach, whereby critical failure modes and associated operating conditions will be analysed prior to implementation of the test regime.

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