| Rotating machinery such as pumps and compressors are among the critical equipments in essential facilities such as hospitals. Ensuring the safety and functionality of these machines during and after earthquakes is one of the important goals of seismic hazards mitigation.; Rotating machinery have a dual vibration isolation problem associated with them which consists of isolating the housing structure from the machine's operational vibration and in addition, protecting the machine during a seismic event. 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.; Traditionally, in analysis from vibration viewpoint, rotating machines have been modeled as rigid block. However, in reality these machines have a complex internal structure and while for certain parameters they might effectively behave as rigid blocks, in other cases it would be inadequate or even unsafe to ignore their actual internal structure.; In this research, evaluation of operationally and seismically optimum mounts for rotating machines is illustrated. Performance criteria and associated relevant response quantities are outlined. Simplified modeling technique of rotating, machinery is presented which, compared to the option of finite element modeling, can speedily but adequately calculate the relevant response quantities. Using random vibration approach, it is shown that significant performance improvement is achievable by proper mount design. The design methodology is outlined and analytical results are presented. Results of shaking table experiments performed on a realistic setup with centrifugal pump are presented. It is concluded that a solution to this dual isolation problem lies in a semi-active mount which is capable of switching its properties from "operation-optimum" to "seismic-optimum" at the onset of a seismic event. An implementable semi-active mount setup is outlined. |
