Machine Design

Online seal design guide

An interactive Seal Design Guide is available at Users can access the guide free of charge after an initial registration. The guide provides information on basic concepts of O-ring design, seal types and gland design, critical operating factors, material selection, and special elastomer-seal applications.

The guide contains 14 sections to help users select seals and learn about O-rings. For instance, an "O-Ring Basics" section defines O-ring fundamentals such as geometry, compression, and how to provide an effective seal.

The guide also offers information on how to machine glands and the recommended surface finish. For instance, static applications can tolerate surface finishes as rough as 64 to 128 microns (rms). And although one might assume that dynamic applications require highly polished surfaces, that is not the case because they will not hold lubricant. In fact, shotpeened or electropolished surfaces are ideal, according to the Seal Design Guide, because they provide small pockets in the metal to entrap lubricants.

The guide also includes links to equations and tables. For example, a section explaining the effects of chemicals on O-ring seals has a button that downloads a PDF file of a Chemical Compatibility Table. The table lists 21 common O-ring materials and how they resist various chemicals. Chemical resistance for each material is classified as good, fair, questionable, or poor. The list of over 300 chemicals ranges from whiskey to methyl ethyl ketone.

The guide also has a glossary of common seal terms, a troubleshooting section, and a section listing standard O-ring sizes for users who already know application requirements. If users aren't sure of the O-ring size, equations are given for parameters such as maximum and minimum O-ring cross section, and maximum O-ring volume.

This information supplied by Apple Rubber Products Inc., Lancaster, N.Y.

TAGS: Hydraulics
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