Does anyone know what is the purpose of O-ring for the bearing assembly on motor free end (NDE)?
Without the details of the design, I can only speculate. On one occasion I had worked on a gearbox at a jet engine test facility that had a high speed pinion supported on rolling element bearings. The pinion had to pass through a critical speed in its normal use. In spite of my balancing efforts the vibration was extremely high and the service required the gearbox to start/stop several times daily. I had the machine disassembled and slightly opened the bearing bore and added a groove with o-ring. This provided sufficient damping to enable passage through the critical. The application was somewhat similar to what is called a squeeze film damper.
This was a case where a gear sales person fancied himself a consultant on gear design. Ultimately the gearbox was replaced by a unit with fluid film bearings that was designed/manufactured by a reputable gear manufacturer. But several years of service were obtained with the original gearbox.
Thank you for your info. Anyhow, recently i have a problem in bearing looseness and wear at BPFO from this motor at NDE side, then we have a series of investigation including vibration analysis and come to replace the bearing. We are successfully replace the bearing but not the o-ring, since then during machine startup we experience a high vibration and spectrum shows bearing looseness, then we came to the replace the o-ring then the vibration went down.
It so happen that i am curious for the function of this o-ring and i cant find any.