A dual isolation problem for rotating machines consists of isolation of housing structures from the machine vibrations and protection of machines during an earthquake to maintain their functionality. The desirable characteristics of machine mounts for the above two purposes can differ significantly due to the difference in the nature of the excitation and in the performance criteria in the two situations. In this paper, evaluation of seismically optimum mounts is illustrated. Simplified models of rotating machinery are presented which can adequately provide the relevant response quantities. Performance criteria for rotating machines are outlined. Using random vibration approach with a stationary excitation, it is shown that significant performance improvement is achievable by proper mount design. Results of shaking table experiments performed with a realistic set-up of a centrifugal pump are presented. It is concluded that a solution to this dual isolation problem lies in a semi-active mount capable of switching its properties from 'operation-optimum' to 'seismic-optimum' at the onset of a seismic event.
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