The problem:
Some wind turbine generator platforms do not provide for adequate stiffness to accommodate the widely used 2-row 4-point contact ball pitch bearing.
- Ring cracking (corrosion fatigue, cracks through filler plugs, cracks next to lifting/stiffening plates, fastening elements & hub cracks)
- Contact ellipse truncation along with load increase (cage failure, raceway edge & ball fractures and spalling)
As a result several 2-row 4-point (2r4p) pitch bearings fail prematurely and need to be replaced in the field. Neither the blade root nor the hub can be fundamentally reinforced on site – costly multiple replacements are often the consequence. The 45deg contact angle of 2r4p pitch bearings makes it even worse – radial loads resulting from resolution of aero dynamical forces increase the ring separation and cause bearing ovalization.
T-Solid - the solution:
IMO made a change in paradigm: If you cannot avoid the detrimental deformation effects, choose a bearing design which can simply withstand it!
T-Solid, developed and manufactured by IMO, is a 3-ring/3-raceway pitch bearing which has same form, fit & function like the 2r4p pitch bearing to be replaced.
- The difference comes from the load independent 90deg contact angle: no ellipse truncation effects.
- No cage – logically no cage issues
- No filler plugs – logically no cracks through filler plugs
- Hoop stresses are much lower compared with 2r4p pitch bearings, therefore, T-Solid operational life is much longer.
- Fatigue issues are history with T-Solid!
T-Solid is field proven in many 1 to 4MW platforms – first T-Solid fielded already in 2016 on a 3-4MW class wind turbine! T-Solid was also chosen by OEM for a 8MW offshore turbine in 2021. T-Solid is available for many platforms including but not limited to hydraulic & electric pitch machines, blade on inner or on outer ring configurations, for OEMs and after sales market.
- In the after sales market T-Solid is first choice for blade bearing field retrofit in turbines which experience a shortfall in fatigue life especially in combination with stiffness issues. As robust as required for 20+ years’ service life at high prevailing hub deformation levels.
- OEMs use T-Solid for large low wind onshore rotors and large offshore machines.
- 2r4p pitch bearings (2-row 4-point contact) can be used as replacements in machines in which this susceptible design survived at least half of the service life. IMO 2r4p pitch bearings include a variety of product improvements to address known failure modes.
- T-Solid remains the better alternative, if life span shall be extended, maybe to 25 years for better return on investment.
- Never use 3-row roller type bearings for prematurely failing 2r4p pitch bearings! 3-row roller type bearings generally have a much higher demand on stiffness than 2r4p bearings, hence, early failure is almost predictable!
