W HY DO G E ARBO X E S FAI L P RE M AT URE LY … AND W HAT CAN BE DO NE ABO UT I T ?

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We are committed to the industry.

This means communicating what we have learned through our investments and experience.

This is an evolving story.

What you are going to hear today is what we know, and the reasons why we are going in the direction

that we are.

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Agenda

Why are gearboxes failing prematurely?

ISO 6336-5 Remanufacturing

specification RCA to

Revolution: Example

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Why are gearboxes failing prematurely? 1. Improper Assembly, i.e. bearing

settings, gear floats

2. Material Quality Inconsistency

3. Lubrication Maintenance Practices

4. Gearbox design architecture sensitivity to non torque loads

5. Site specific operating conditions varying from design parameters

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“Wear” related failures generally take more than 5 years to develop, but tough sites could see sooner with specific

designs.

Generally considered “infant mortality,” but

may take more than 3 years to develop

depending on site conditions.

ISO 6336-5: Strength and Quality of Materials

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Material Cleanliness Grades: - ML, similar to AGMA 1 - MQ, similar to AGMA 2 >>> Default for industrial AND wind! - ME, similar to AGMA 3 >>> higher allowable stresses, select availability - MX, special grade >>> not readily available

Specifies location of core hardness in finished tooth

- Recognizes process control test bars - i.e. each heat treat load has traceability ensuring core hardness assumed by standard

achieved

References importance of application driven safety factors, both contact (pitting) and bending (fatigue).

These assumptions are the fundamental material science building blocks of gearbox design.

Contact vs. Bending

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Contact – Macropitting Bending - Fatigue

Gear Component Design Safety Factors

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*GBX performed calculations from assumed turbine loading condition. Representative values.

Rated Power Required Required 1.5MW 1.5MW 1.5MW 1.5MWSafety Factor Design Design Model B Model B Model A Model AISO 6336-5 Gear Material Quality Criteria Criteria MQ MQ MQ MQGear Positions Contact SF Bending SF Contact SF Bending SF Contact SF Bending SFRing 1.2 1.5 1.194 2.067 1.624 2.004Sun 1.2 1.5 1.361 2.198 1.198 1.987Planet Pinion 1.2 1.5 2.018 2.305 1.247 1.657Planet Gear 1.2 1.5 1.434 2.206 n/a n/aLSS Gear 1.2 1.5 1.498 3.102 1.328 2.317IMS Pinion 1.2 1.5 n/a n/a 1.271 1.934IMS Gear 1.2 1.5 n/a n/a 1.315 2.278HS Pinion 1.2 1.5 1.418 2.884 1.269 1.887

And if turbine operates at higher power…

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Rated Power 1.5MW 1.5MW 1.8MW 1.8MW 1.95MW 1.95MWSafety Factor Model A Model A Model A Model A Model A Model AISO 6336-5 Gear Material Quality MQ MQ MQ MQ MQ MQGear Positions Contact SF Bending SF Contact SF Bending SF Contact SF Bending SFRing 1.624 2.004 1.51 1.728 1.456 1.614Sun 1.198 1.987 1.106 1.741 1.065 1.629Planet Pinion 1.247 1.657 1.151 1.437 1.109 1.339LSS Gear 1.328 2.317 1.229 2.013 1.186 1.887IMS Pinion 1.271 1.934 1.177 1.697 1.136 1.592IMS Gear 1.315 2.278 1.225 2.008 1.184 1.878HS Pinion 1.269 1.887 1.183 1.794 1.142 1.693

*GBX performed calculations from assumed turbine loading condition. Representative values.

Short story. 1. Wind turbine gearboxes are smaller than they

should be. i.e service factor

2. They fail for similar reasons, but also each have their nuances based on the OEM design.

3. Improved maintenance can help, but….

4. The site conditions ultimately drive failure rates and reliability.

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Standard Gearbox vs. Revolution

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Component 3YR, Standard RevolutionMaterial Type MQ MQRing Regrind, Nitride New, CarburizedPlanets Regrind NewSun Regrind NewLSS Gear Regrind New or regrindIMS Pinion Regrind NewIMS Gear Regrind New or regrindHSS Regrind NewPlanet Bearings Thru hardened Timken, CarburizedHSS-IMS Bearings Timken, Carburized Timken, CarburizedGBXtreme Filter No YesWater Lok No YesAmsoil Fill No YesLoad Test Yes YesWarranty 3YR 5YRCrane Coverage No Yes

*Note with longer warranties, all “pinions” are replaced new. These are rating element of gearbox.

Gear Regrinding. GBX Specification.

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Ring Gears are not reused. HS Pinion Shafts are not reused. The rest of the components follow this process:

1. First thoroughly cleaned and visually inspected. If damage is too great for successful regrind (~0.002”), it is scrapped.

2. Then magnetic particle inspection (MPI) for internal cracks. 3. Then sent to gear supplier for nital etch inspection to confirm grinding

temper does not exist. 4. Gear is then measured to ensure sufficient stock (0.003”) is available to

attempt regrind. If measurements are below lower tolerance, part is scrapped.

5. The gear is reground to 100% clean up, then remeasured to ensure above lower tolerance limit.

a. Additional step for planet gears, which includes a check of bearing bores (OD, cylindricity, roundness)

6. Gear is then MPI’ed and nital etched again. 7. If all passes, it is shipped back to us and certified for reuse.

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47.9%

53.0%

58.0%61.0% 62.0%

67.0%

75.0%

79.0%82.0%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

80,000

90,000

100,000

110,000

120,000

130,000

140,000

150,000

160,000

170,000

180,000

190,000

200,000

Repair Load Test Lube System/ Hoses /Fasteners

BearingUpgrade

HS Pinion Planets Ring Gear /Sun Pinion

LSS Gear IMSAssembly

3YRGBXchange

New

Repair vs. Remanufacturing

Assuming a typical $200k new gearbox

Recertification Component Credits ~$10-40kCommon Repair Exclusions ~$20-30k

Core (Hsg/Carrier) generally 15-20% of new

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Uneven 4 Row Planet Roller Load Share

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Extreme Loading Conditions: Hertzian contact stresses

The collateral issues it can cause…

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Uneven load sharing on 4 cylindrical planet rollers

Excess clearances in bearings permits signficant movement from non torque loads.

Any material inclusions accelerate failures

Housing may crack when gearbox locks up from debris collecting in sump.

Upgrade solution: Integral 2 row.

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Significantly improved load share. Integral race permits larger diameter rollers with increased capacity.

Additional upgrade: Higher Grade Material.

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Power 1.8MW 1.8MW 1.8MW 1.8MWSafety Factor MQ MQ ME MEGear Positions Contact SF Bending SF Contact SF Bending SFRing 1.51 1.728 1.778 1.819Sun 1.106 1.741 1.216 1.828Planet Pinion 1.151 1.437 1.266 1.509Planet Gear n/a n/a n/a n/aLSS Gear 1.229 2.013 1.352 2.114IMS Pinion 1.177 1.697 1.294 1.782IMS Gear 1.225 2.008 1.348 2.108HS Pinion 1.183 1.794 1.301 1.884

Turbines will operate above rated power. Higher grade material provides some additional service factor.

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Revo.2 is coming….