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 Gearbox Reliability 

Database: Yesterday, 

Today, and Tomorrow 

Shuangwen (Shawn) Sheng

Wind Turbine Tribology Seminar

October 29‒31, 2014

Chicago, Illinois

NREL/PR-5000-63106
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Outline 

 Before 2012

• Project background

• Major accomplishments 

 October 2012 to September 

2014

• Status update

• Representative results

• Observations 

 October 2014 to September 

2016 

• Project plan.
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Project Background 

 The Gearbox Reliability Collaborative: 

• Aims to improve gearbox reliability and 

availability 

• Takes a multifaceted approach: testing, 

modeling, condition monitoring, and 

database. 

 The Gearbox Reliability Database project: 

• Aims to quantify the magnitude of the 

problem and identify top failure modes 

and root causes

• Collects gearbox failure event data from 

project partners, all have executed 

nondisclosure agreements with NREL

• Directs wind turbine gearbox reliability 

research and development (R&D) and 

provides a benchmark for evaluating

technology advancements. 

Plot source: Sheng, S.; Link, H.; LaCava, W.; van Dam, J.; McNiff, B.; Veers, P.; Keller, J.; Butterfield, S.; Oyague, F. (2011). Wind Turbine 

Drivetrain Condition Monitoring During GRC Phase 1 and Phase 2 Testing. 58 pp.; NREL Report No. TP-5000-52748. Golden, CO: National 

Renewable Energy Laboratory. 

Illustration by NREL
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Major Accomplishments

 Developed GearFacts, a gearbox 

rebuild event data recording tool 

and a postgreSQL database 

 Collected some data at very 

detailed levels 

 Built a Sharepoint site hosted by 

NREL for data sharing and 

information exchange 

 Provided training to project 

partners on gearbox failure 

analysis.
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Major Accomplishments (Cont.)

 Released first round of damage distribution based on confirmable 

damage records

 Samples: 34 incidents, 4 original equipment manufacturers (OEMs)

 Bearing failures dominant 

 Bearing faults are concentrated in the parallel section; gear faults are 

concentrated in the planetary section.
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Status Update 

 Continued most activities from before 

October 2012

 Initiated the normalization of taxonomy 

for wind turbine and plant based on 

ReliaWind and Sandia CREW databases

 Reduced data collection complexity by 

examining data fields collected by 

GearFacts and prioritizing them into 

three categories: high, medium, and low

 Introduced Microsoft Excel spreadsheet 

template for data collection with only 

high priority fields. 

Wind Site Name

Wind Site State Province Region

Wind Site Country

WTG Make/Model

WTG Pad No.

WTG Total Run Hours Estimation 

WTG Total Production kWh Estimation 

WTG Type of Power Conversion

WTG Type of Generator

Gearbox Maker/Model (if you are not comfortable 

sharing this with NREL, please skip)

Gearbox Serial No. (if you are not comfortable with 

the full description of the serial No., please share 

the last three digits.)

Gearbox Originally New or Rebuilt

Install Date

Failure Date

Gearbox Run Hours Estimation 

Gearbox Production Estimation (kWh)

Original Lubricant Type

Current Lubricant Type

Inline Filter Rating (50 mirons, 20 microns, 10 

microns, or 5 microns) 

Offline Filter Rating (3 microns)

How was Damage Detected 

Dominant Failure (Worst) Location

Secondary Failure (2nd Worst) Location

Dominant Failure (Worst) Mode

Secondary Failure (2nd Worst) Mode

Corrective Actions (Uptower repair, internal 

component replacement, or gearbox replacement) 

Other Drivetrain Component Failures Before this 

damage

Other Drivetrain Component Failures After this 

damage

Additional Notes
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Status Update (Cont.)

 Developed new data collection tool with less complexity 

than GearFacts and deployable on portable devices

 Partners increased to more than 20 including turbine and 

gearbox OEMs, gearbox rebuild shops, wind plant 

owner/operators, and consulting companies

 Total assets represented by owner/operator partners 

reached more than 34% of the U.S. end of 2013 installed 

capacity 

 Data entries on gearboxes increased to about 900, among 

which about 1/3 with confirmable damage 

locations/components => need to standardize data 

collection 

 Six major gearbox OEMs are represented by the data. 
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Representative Results

The left chart was released in 2013, based on 257 damage records, and the right graph was released in 

2014, based on 320 damage records.

 Both represent six gearbox OEMs

 Both indicate gearboxes could fail in drastically different ways 

 Bearings: 70% (2013) to 64% (2014), dominated by high-speed shaft (HSS) and intermediate-speed 

(IMS) bearings

 Gears: 26% (2013) to 25% (2014), dominated by Helical gears 

 Others: 4% (2013) to 11% (2014), dominated by lubrication and filtration system

 Both bearing and gear faults are concentrated in the parallel section.
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Representative Results (Cont.)

 Samples: about 80 

records

 Axial cracks: 71% 

 Spalling: 23% 

 Pitting: 6%

Axial cracks (dominated by high-speed and intermediate-speed stage 

bearings inner raceway)

Photo sources: Gary Doll, University of Akron (left two), and Ryan Evans, Timken (far right)
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Current Observations

 Value of and need for a reliability database demonstrated by: 

• Participation of more than 20 partners

• Inquiries on gearbox reliability information from the global 

wind community

• Direction of reliability R&D and mitigation strategies.

 Challenges: 

• Standardized reliability data collection practices for not 

only gearboxes but also other major 

components/subsystems

• Lack of representative data at a bigger population to better 

reflect the reality 

• Actively engaging partners to submit data.
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Project Plan 

 Introduce a three-tier data-sharing mechanism: 

 Launch remote data collection Web service

 Focus more on data collection and analysis

 Target a few dominant failure modes and release 

industry-wide statistics

 Expand the scope of the database to cover main shaft 

bearings and other major components/subsystems. 

Data-sharing 

partner

Data/reports shared 

exclusively with 

partner

Data/reports shared 

among all project 

partners

Data/reports released 

to the public by NREL 

Partner: inquiry-based, 

same-level of details 

as data submitted 

Public: annual statistics updates 

by also removing sensitive 

information like data owners 

Member: periodical reports 

by removing sensitive information 

like OEMs and Serial Numbers 
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Thank You! 

Data collection is the foundation to derive information and gain knowledge! 
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Acknowledgments 

 U.S. Department of Energy Wind and Water Power 

Program 

 Data-sharing partners 

 The gearbox reliability database project team 

• NREL Technology Transfer office

• Data collection tools developers

• NREL colleagues handling logistics and communication 

tasks 

 NREL Gearbox Reliability Collaborative project 

colleagues. 
Shawn Sheng

(303) 384-7106