9 - Seals

Abstract

This chapter discusses about seals, which are devices used to prevent or limit leakage of fluids or particulates. The aim of this chapter is to introduce the variety of seal configurations, give guidelines for the selection of seals, and introduce calculation methods for the quantification of some seal leakage rates. Static seals aim at providing a complete physical barrier to leakage flow. To achieve this, the seal material must be resilient enough to flow into and fill any irregularities in the surfaces being sealed and at the same time remain rigid enough to resist extrusion into clearances. Elastomeric seals and gaskets fulfil these criteria and are described in the chapter. Effective sealing may require high contact pressure between a stationary component and a rotating component, but minimal wear is also desired for long seal life. It is frequently necessary in machine design to provide some means of containing or limiting the flow of fluid from one region to another. Because of the very small nature of fluid molecules, this is a challenging task. Further, the chapter discusses a range of static and dynamic seals. Because of the wide range of applications, seals tend not to be available as stock items and instead must be designed fit for purpose.