Main Bearing RCA
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This document discusses Sentient Science's analysis of main bearing failures in wind turbines and other rotating equipment. It presents Sentient's digital main bearing wear model, which uses SCADA data, load modeling, bearing dynamics modeling, and a wear model to identify early damage progression in main bearings and provide recommendations to extend their remaining useful life. The model outputs include local contact forces, sliding velocities, equivalent radii, overturning moments, and thrust and radial loads. Sentient's approach aims to help operators and suppliers reduce costs through increased asset life and supply chain control.
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Main Bearing RCA
- 1. © 2016 Sentient Science Corporation – Confidential & Proprietary Main Bearing RCA
- 2. © 2016 Sentient Science Corporation – Confidential & Proprietary Material Science Differentiation 1. Asset Management for Operators 2. Computational Testing & Reconfiguration for Suppliers ☑ Life Extension☑ Root Causes☑ Predict Earlier Key Industries Served WIND ENERGY • 20,000 assets under contract globally AEROSPACE • Rotorcraft, Fixed Wing, & Defense • (15 Years of R&D) RAIL • 1 Million km Global Railways • Wheel Rail Interface Sentient Science is a trusted third party enabling life extension of rotating equipment through a digital platform, connecting operators and suppliers through asset actions that lowers the cost of energy.
- 3. SentientScienceCorp.-Proprietary/PrivateLevel1 Why Investigate Main Bearings? 3 High Risk: Main bearing failure often transfers thrust loads to the gearbox, which can lead to catastrophic damage in the gearbox. High Cost: Main Bearing Replacement ranges from $150K - $300K. In extreme cases can cause upwards of $500K. Uncertainty: Alerted of main bearing failure after SCADA temperature alarms are going off. Supply Chain Control: Lack of control in supply chain due to no lead time for main bearing failures, causing unexpected downtime.
- 4. SentientScienceCorp.-Proprietary/PrivateLevel1 Premature Failure in Main Bearings Main Bearing Wear Model Three Point Configuration Spherical Roller Bearing INNER RACE, OUTER RACE, ROLLER CAGE, GUIDE RINGS High Radial load capacity Accommodates misalignments Require relatively high ratio of radial to axial load Increased sliding due to Heathcote slip Thrust Load Bearing Design Low RPM Loss of Lubrication Uneven Load Distribution Surface Roughness Lubricant Viscosity High Pressure High Sliding Low Lambda Low Lambda
- 5. SentientScienceCorp.-Proprietary/PrivateLevel1 Failure Modes in Main Bearings Main Bearing Wear Model Wear on Inner Race Micropitting Macropitting Spalling Abrasive Damage Roller, Cage Crack FAILURE PROGRESSION IN MAIN BEARINGS (manifests as early as 6 TO 10 YEARS) Sentient’s Main Bearing Failure model identifies early manifestation of damage in Main Bearings and provides recommendations to slow down damage progression, such that the Remaining Useful Life of the bearing can be extended Asperity Plastic Deformation Adhesive wear, Surface Fatigue Wear Bands on Inner Race Incubates in the vicinity of wear bands Cyclic shear stresses at shallow depths below the asperities Loss of geometry due to significant micropitting High contact stresses, edge loads Debris dents the race and rollers Rapidly evolves and accelerates damage
- 6. SentientScienceCorp.-Proprietary/PrivateLevel1 Main Bearing Wear Model DigitalClone Live Main Bearing Model Strategy WIND LOAD MODEL BEARING DYNAMICS MODEL WEAR MODEL SCADA data Turbulence Intensity Windspeed Wind Direction Loads on Main shaft Bearing Configuration Geometry Bearing Clearances Material Elastic modulus Main shaft RPM Contact Pressure Sliding Velocity Material : Hardness, Elastic Modulus, Ultimate Strength Surface topography : 𝑅 𝑞, 𝑅 𝑠𝑘, 𝑅 𝑘𝑢, 𝛽 𝑥, 𝛽 𝑦 Lubricant: Viscosity, PV Coeff Main Bearing Risk Ranking [MTOD] Critical locations Life Extension Action Wear Rate Wear Coefficient Inputs Outputs Local Contact Forces Sliding velocities Equivalent Radii Overturning Moments Thrust, Radial Load
- 7. © 2016 Sentient Science Corporation – Confidential & Proprietary Learn More! Sentient Presentation Schedule Wind Europe 2017 1. DigitalClone Live Product Update 2. Why Data Science Wont Lower the Cost of Energy 3. Reducing Costs with Digitalization 4. Duke Energy Case Study 5. Rewitec Additives to Extend Gearbox Life 6. Moventas XL Life Extension Program 7. How to Value Digitalization 8. Sentient in the China Wind Market 9. DigitalClone Bearing Product Release 10. Wind Loads Modeling 11. Drive Train Modeling 12. Data Fusion Materials Science & Data Science Hello 7 Meet the team in the booth for further discussions
Editor's Notes
- At Sentient Science we computationally test models of rotating components to understand components useful life through a material science based approach. With this we create Digital Life models of wind turbines to predict health and remaining useful life of the turbines major system. Our approach allows us to understand prior to a failure where a crack is occurring and to provide our *supplier and operator* customers with asset actions to extend the life of our machines. We also are in different industries, we started in the Aerospace Industry with money from the US Government and we have expanded into wind with currently 22,000 assets being monitored. We have also been making headway into the Rail industry with the millions of kilometers of railways that need smart maintenance.
- In this presentation before we get into the how main bearings fail let’s go briefly over the why we should investigate this. Main bearings have a high cost ranking from $150k to $300k and the maintenance is usually overlooked during annual services. Most operators put a higher focus on gearbox maintenance, but there are a number of actions that can be done uptower to prevent damage to the main bearing like hot oil flushes, measuring and correcting misalignment and thrust load control. Moreover damage to the main bearing can spread to the gearbox as the bearing transfers thrust load instead of supporting it as it should. If you know the main bearing is failing ahead of time you can prevent the damage spreading to the gearbox. If you know the the main bearing is failing, you can also plan ahead to obtain the best quality components at the best price while eliminating unplanned downtime. Sentient Science allows the operator to select the best components because we look at depth at the design and materials of each component and of course determine which component will have the longest life.. We want to avoid the firefight that starts once the SCADA temperature alarms are going off and it is too late.
- Now that we briefly talked about the why let’s talk about the *why* let’s talk about the *how* do Main bearing fail prematurely in 6-10 years as we have observed. Spherical Roller Bearings are the bearing of choice for most main bearings because the high load capacity and their ability to accommodate misalignments. However the ratio of radial to axial or thust load needs to be high. Thrust load should not be more than 20%--30% of the radial load, but we observe in the field that the thrust load the main bearings observe is as high as 60%. Thrust loads lead to loss of lubrication condition and uneven load distribution that in turn leads to low lambda or a low film thickness to surface roughness ratio and high contact pressure. The downwind side is overloaded with less lubrication. Also Spherical Roller Bearings lend are inherently prone to high sliding velocities, this compounded with the loss of lubrication conditions can also lead to low lambda situations. Moreover Spherical Roller Bearing see low RPM conditions at which there is not enough velocity for a lubrication film to develop to separate the raceways of the rollers, depending on the lubrican viscosity and the surface roughness asperity contacts may readily happen.
- The most common failure progression in a main bearing is found to be wear on the inner race. Due to high sliding, uneven loads and low lambda conditions, asperity contacts occur and adhesive wear or surface fatigue wear takes place. This cause narrow and shallow wear or plastic deformation bands on the inner race. When these wear bands occur the geometry at the microscale is no longer optimal and high pressure along the vicinity causes micropiting. High cyclic shear stresses in the near subsurface are the primary cause for this type of failure. Micropitting eventually leads to macropitting and abrasive damage due to generated debris. At this stage the failure accelerates and leads to roller and cage cracks. The most common failure progression in main bearing is found to be wear on inner race. Due to high sliding, uneven loads and low lambda conditions, asperity contacts occur and adhesive wear or surface fatigue wear takes place. This causes narrow and shallow wear bands on the inner race. There are however exceptions to this common failure mode. White structure flaking is observed as well as spalling on outer race. However, the cause of these failures are associated with the same mechanisms we mentioned like initial sliding, poor lubrication conditions and higher loads.
- Now that we talked about the why investigate main bearing failures and how main bearing fail let me speak briefly about the Sentient Approach. We divide our work into three main buckets. For the wind load model we take the scada data and other factors to determining the moments and forces that act on a bearing. Then we develop a bearing dynamics model to go from the macro loads to the micro loads like local contact forces and sliding velocities. Then we take these inputs from the system and bearing model, with out material characterization to determine the wear rates at various locations. We have talked about individual bearings. However Sentient has spent a large amount of time and resources in solving the problem of running these models for the large fleets we serve. Hence we can look at the wear problem from a fleet perspective and find the turbines the components that need to be checked to apply life extension actions like comparing suppliers, , hot oil flushes, measure and correct alignmnent, and advance planning.