Mainshafts are one of the key components of both the drivetrain and of the entire wind turbine. While they may not exist in larger wind turbines, such as the Mitsubishi 2.4 MW, as well as in direct drive turbines, mainshafts such as these pictured are a critical element in connecting the blade hub to the gearbox
A potential weak link is the availability are the gearbox mainshafts.
- While reverse engineered mainshafts can be sourced elsewhere, the drawings and specifications are closely held by the Original Equipment Manufacturers ("OEM’s"). Even though the same forgings may be available from the same manufacturer, then without utilizing material and hardness specs that are guaranteed to greater than or equal to the OEM specification, then the resulting mainshafts could snap and potentially destroy the entire wind turbine.
- However, mainshafts are generally repairable. If you can purchase enough additional stock such that you can repair them while installing the new replacements, and the repairs can be accomplished and returned to inventory before depleting the spare mainshafts, then the program becomes sustainable. This will require good repair partners, an agreed to repair specification, an agreement regarding which mainshaft bearings should be utilized, and an on-going internal analysis and balance of what is the proper number of spare mainshafts that should be maintained by your organization.
- For the GE 1.5 MW fleet a “universal” mainshaft should be considered because the mainshaft flange varies by whether turbine's bedplate is welded or cast, and there is no guarantee of which bedplate will be in an older "S" or "SLE" wind turbine model. A "universal" configuration is created by grinding out the requisite notches for the interlock mechanism required for the welded bedplate design along the edge of the mainshaft flange that mates to the blade hub, as well as insuring the requisite holes for the interlock brake of a cast bedplate rotor lock system are tapped in exactly the correct locations in the mainshaft flange.