Grease was blackened upon disassembly. We are unsure if this is a cause or effect of the root failure mechanism. Note first failure occurred within 9 months of commercial operation. One bearing had a lot of damage – cracked outer race with pitting and spalling, damaged rollers and cage, pitting and fracture on inner race. False brinelling observed on other bearings that were not damaged as badly. Other gearboxes were removed based on high vibration prior to this type of complete failure. OEM is holding some of these due to warranty claims
Motors do not have VFD. They are single speed with no soft start.