Refurbishment of Wind Turbine Gears via Surface Finishing

REM has supported the wind turbine gearbox industry for OEM applications since the early 2000s.  In the late 2000s, as many non-ISF® Processed wind turbine gearboxes were coming out of service for maintenance and warranty issues, REM developed and patented a subtractive gear repair technology for wind turbine gear (and other gear) applications.  REM’s ISF Process has now been used to repair used, damaged wind turbine gears for over a decade, recovering hundreds of gears to better than new condition.

Traditional wind turbine repair options include regrinding, hand polishing, or new component replacement; however, all three options have significant drawbacks.

Regrinding has limitations such as the risk of scrapping a component caused by too much removal or profile errors, offers no surface finish or texture improvement, and requires a post-grinding nital etch inspection (hazardous process) to ensure no metallurgical damage has occurred in the form of temper-burn/decarburization.  Hand polishing can take many forms with wind turbine gears (sanding, stoning, rotary tools, etc.), but has limitations such as being labor intensive, non-machine controlled, only capable of limited material removal, offers no surface finish or texture improvement, and risks incomplete or irregular damage removal.  New component replacement it is expensive, can have long lead times, and once again, still offers no surface finish or texture improvement.

Fortunately, REM Surface Engineering’s ISF Process creates a superior surface to grinding/machining, improves component performance, and offers cost savings other repair techniques do not.   By simplifying repair operations and salvaging more components, REM customers see increased direct savings.  The ISF® Surface is also an optimal surface finish for gears, improves component performance and creating upgrade options regarding lubricant packages and lubricant filtration.

Typical ISF Process material removal ranges for Wind Turbine Gear refurbishment are 0.001 -0.003” per surface (~25 – 76 µm); additional material removal can be executed pending part tolerances.  Targeted final finishes are: Ra = 2 – 8 µin (0.05 – 0.20  µm), Rz = 8 – 32 µin (0.20 – 0.80  µm) and Rmr (0.4 µm) = > 98%.

REM’s isotropic superfinishing technology is the only Wind Turbine Refurbishment method that is proven to lower O&M costs while increasing gearbox life, gear performance, and operating safety margins.  The ISF Process is able to repair damaged nitride components and can repair some component assemblies, thus reducing manufacturing steps/costs.

REM’s ISF® Refurbishment technology is available via outsourced processing at a REM location or as a technology installation at a customer site.

Some of the Wind Turbine Repair Applications REM’s ISF Process can assist with include:

  • Planet Gears
  • Sun Pinions
  • Intermediate Pinions
  • High Speed Pinions
  • Low and High Speed Helical Gears
  • Ring Gears
  • Advanced Applications
  • Integral Bearing Races (Planets)
  • Nitrided Ring Gears
  • Low Speed Assemblies
    • Low Speed Helical Gear + Hollow Shaft/Coupling
  • Intermediate Assemblies
    • Intermediate Pinion + High Speed Helical Gear
    • Double Helical Bull Gears

Manufacturing Benefits of ISF Process for Wind Turbine Repair:

  • No Part Drawing Required
  • No Risk of In Process Scrapping
  • Reduced Setup Time
  • Reduced Part Separation Requirements
  • Reduced Operation Steps
  • Processing of Assembled Components
  • Process Multiple Features Simultaneously
  • Eliminate Risk of Scrapping During Separation
  • No Post-Process Nital Etch Required

Quality/End User Benefits of the ISF Process for Wind Turbine Repair:

  • Significantly Reduced Surface Roughness
  • Improved Lambda Ratio
  • Increased Micropitting Safety Factor
  • Improved Load Carrying Capacity
  • Increased Component Life

Additional Upgrade Options Created by the ISF Process:

  • Reduced Lubricant Viscosity Requirements
  • Reduced Lubricant Additive Requirements (Anti-wear, Micropitting)
  • Reduced Lubricant Filter Size (smaller mesh)
    • Reduced Lubricant Contamination

Repairable Damage Types via the ISF Process:

  • Micropitting
  • Scuffing
  • Fretting
  • Corrosion
  • FOD Damage

Damage Not Repairable via the ISF Process:

  • Changes to tooth profile
  • Depth of damage exceeding maximum allowable metal removal
  • Undersized gear tooth

Have a Wind Turbine Gear Refurbishment need?  Interested in upgrading you used Wind Turbine Gears?  Curious about implementing an ISF Refurbishment Cell in your facility?  Contact us today for more information or to get a project started.  REM loves supporting renewable energy, and the opportunity to decrease costs of operation while increasing Wind Turbine uptime is one we are always excited to pursue.