A Novel Approach for Diagnostic of Aeroderivative GT Roller Bearings Through Ultrasonic Reflectometry Combined With Acoustic Emissions

Abstract Rolling element bearings are among the most significant components impacting aeroderivative Gas Turbine (GT) reliability. Their life varies from engine to engine, leading to non-predictable stops and maintenance intervals. Current state-of-the-art instrumentation does not provide a reliable or accurate monitoring for a rolling element bearing condition-based maintenance approach. A reliable, real-time prognostic system for the bearings can result in significant savings to the customer through optimized maintenance intervals, and reduction in unplanned outages. This paper explores a novel approach to monitoring these bearings using ultrasonic reflectometry combined with ultrasonic acoustic emissions as applied to aeroderivative GTs. Ultrasound is exceptionally sensitive to changes in a bearing’s operating conditions, such as loads, speeds, lubricated conditions, early on-set defects and temperatures. The measurement approach is performed by both collecting the response from an emitted soundwave that is sent through the roller bearing (active ultrasonic reflectometry), and by capturing the acoustic emissions. Different parameters can be measured by the two approaches due to the difference in frequency ranges they operate over. This combined ultrasonic approach is described in this paper through instrumenting a bearing from a Baker Hughes aeroderivative gas turbine on a dedicated test rig. This test rig replicates the bearing geometry in 1:1 scale, reproducing faithfully the assembly, and operational functionality. The new ultrasonic approach is corroborated using existing rig sensors such as accelerometers and Bently Nevada probes. The operating conditions (rotor speed, radial load and oil flow) are varied to collect data across the range of operating conditions that a bearing will experience in service.