Setting Vibration Criteria For Turbomachinery.

Abstract

Vibration of a journal within a fluid film bearing produces a dynamic load on the babbitted bearing surfaces. A rational vibration criterion can be based on a consistent magnitude of this dynamic load among widely different machines rather than a simple equality of shaft mils of vibration. An analysis and curves are provided for some common types of turbomachinery bearings which can be used to correlate mils of vibration with bearing dynamic load. The analysis shows that the percent of bearing clearance consumed by a vibrating journal, together with its steady load, are two important factors in establishing the dynamic load magnitude. These factors can be used to provide a simple estimate of allowable shaft vibration for a specified dynamic load criterion at acceptable, alarm or trip levels.