Gearbox shaft breakage
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This is a fracture of the output pinion shaft of the wind turbine pitch gearbox; there are two thrust cylindrical bearings mounted closely together on the shaft. The fracture occurs on the side of the shaft near the gearbox, that is, on the drive end side; the bearing on the drive end side is severely damaged, with its inner ring and cage broken into multiple pieces. The bearing on the non-drive end side is intact (the deformation of the cage in the image was caused during disassembly). I would like to ask the experts: can the cause of a broken shaft be determined through fracture analysis?
There are issues with the material, the coupling is misaligned, and the foundation bolts are loose, among other things!
The bolts were checked and found to be tight; there is no coupling inside this gearbox, and it uses a connection mechanism of motor shaft – planetary gears – output shaft. It’s uncertain right now whether the shaft broke due to a damaged bearing, or if the shaft broke first and that caused the bearing to get damaged
It must be the break in the shaft that caused damage to the bearing, because if the bearing were to fail first, there would be wear. From the pictures you sent, no wear on the bearing balls can be seen; therefore, it is concluded that the break in the shaft is what led to damage to the bearing
Correct it to check for any tilt, and then examine the material to see if there are any issues
The shaft surface is damaged, resulting in fatigue fracture under alternating loads
Alignment, material, loose anchor bolts
Check the DCS trends to see if it’s a problem during startup. Ask the staff on site who is turning it on if there are any abnormalities during the startup process.
From a cross-sectional view, the blackened area may be an old injury; there might already be cracks in this area； For the same unit, it is necessary to check this area; it is best to do so when there is a chance to shut down the machine.
It seems to have broken at the keyway; could it be due to excessive load, or is there a problem with the shaft itself at that keyway?
There are keyways; is there stress concentration here? The shaft should break first. If the bearing fails first, the roller cage will definitely be in a terrible state.