Beyond the Specifications for O-rings - Using Good Science to Answer the Form, Fit and Function Questions

Particularly in many aerospace applications, the customer and supplier of an O-ring rely on the part drawing and associated materials specification to make decisions about whether the O-ring is appropriate for an application. That all works well, many times, but there are many instances where the O-ring is supplied to all the documented requirements yet still leaks or fails in the application. Aerospace application failures tend to invite a lot more attention than automotive application failures since aerospace O-ring failures usually involve leakage and grounded aircraft or worse. In this paper, application examples and case histories will be used to demonstrate the utility of several scientific techniques (gland analyses and installation analyses, testing at application temperatures in application fluids, FEA analyses, and simulated functional tests) will be used to illustrate problem solving in these demanding applications. In many cases, we need to go much farther than just the part print and material specification to truly analyze Form, Fit and Function of an O-ring.