We have had 3 gearbox failures in the first 2 years of operation at one of our new sites. These are B&W/SPIG Forced Draft ACC’s with Flender H2NV gearboxes. Wondering if anyone else has had similar infant mortality issues. In all cases the lower output shaft bearing has failed (greased bearing). Potential failure mechanisms could be poor lubrication / grease break down, bearing overload or damage. We have not ruled out manufacturing defects or design flaws. We do have high vibration on many gearboxes especially blade pass frequency.
What was the condition of the grease when repairs were made? Any indication of insufficient grease, oxidation (color change), or water? What did the bearing look like after removal? What faults were present (photos?)? Any indication of EDM from stray electrical current, if motor has a VFD control? The grease filler tube has to be full of clean grease before any measured amount can be added to the bearing housing. I have a lot of experience with ACC fan sound and vibration problems and some gearbox failures.
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.