Abstract

With the need for increased capacity at existing facilities and the design of larger new systems, flow-induced dynamics problems associated with turbomachinery and piping systems have become more common. These phenomena can result in significant noise and vibration related problems, and potentially lead to fatigue failures. In this paper, a brief review of the characteristics of flow-induced vibration and acoustic phenomenon, as applied to turbomachinery, is presented. A select number of case histories involving on and offshore installations in Europe, the Middle East, and the United States will be presented and involve:

* Flow-induced acoustic excitation of safety relief valve piping stubs resulting in excessive vibration and premature venting with loss in production.

* Acoustic excitation of compressor recycle piping caused by vortex shedding past piping discontinuities.

The importance of meaningful data collection and correlation with existing theory, and the modifications necessary for solution, will be discussed in order to enable design and operating personnel to gain insight as to the impact of flow-induced dynamics problems on safety, reliability, and maximum production.

Introduction

Flow-induced dynamics problems resulting in vibration and noise can be a serious occurrence in turbomachinery and associated piping systems. These problems, if not addressed, can lead to: piping systems. These problems, if not addressed, can lead to: * high noise levels affecting personnel hearing loss and community annoyance,

* increased turbomachinery nonsynchronous shaftvibrations,

* high turbomachinery casing vibrations,

* valve component failures,

* high piping vibrations to include excitation of shell resonances and fatigue of smaller piping elements,

* the potential for impeller fatigue damage,

* reduced aerodynamic efficiency, and

* increased downtime.

In approaching the diagnosis of flow-induced machinery noise and vibration problems, it is important to recognize the identifying characteristics of flow-induced vibration excited systems. Furthermore, correlation of theoretical calculations, with experimental or field data, is a requisite for identifying specific sources of problems and devising effective solutions.

Theoretical Background

In general, the source of most flow-induced noise and vibration problems in turbomachinery systems can be traced to the problems in turbomachinery systems can be traced to the coincidence of vortex shedding phenomenon with an acoustic resonance of the same frequency. The effect of the acoustic resonance is to amplify the dynamic pressure pulsations or vibrations created by the vortex shedding. The degree of amplification associated with the system response is related to the damping or "Q" factor in the system.

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