On the determination of bearing support pedestal conditions using shaker testing

摘要

An approach that enables rotor dynamists to determine the bearing support structural conditions through shaker testing is presented. This paper highlights minimum frequency separation requirement between the second rotor vertical critical mode and the bearing support structure mode for safe operation. When the rotor and the bearing pedestal structure frequencies are tested closer to operating frequency, it is probable that structural response could increase monotonically due to instantaneous step change in mass unbalance forces leading to structural degradation and catastrophic damage if the machine continues to operate. This paper discusses how to identify and assess support structure conditions whether they are healthy for continued operation or degraded in service and need stiffening based on the experience gained in fifteen shaker tests on identical/similar structures. Shaker test data enables engineers to assess the pedestal structural conditions by comparing dynamic stiffness of the second rotor vertical critical frequencies between bearing support structures of identical and/or similar designs. In summary, a validated evaluation approach is presented to obtain support stiffness values to calibrate rotor dynamic models and to assess health conditions of bearing support structures as well.