Coasting down signal analysis as a tool for detection of proximity of resonances and a case study

Steady state vibration response of a machinery-supporting structure is strongly influenced by resonances closer to its operating speed. The coasting up/down response of the machinery and the corresponding signal may throw light on the proximity of resonances and pre-cautions can be taken to de-tune it away from the operating frequency. The paper presents the theoretical and experimental background of coasting down response characterized by continuous variation of frequencies. A case study is shown for illustration of the phenomenon and how a large vibration problem in a beam supporting the bearing of a turbo-generator is effectively solved using information obtained from the coasting down signals.