Product Announcement from Buckeye Rubber & Packing Co.
The O-ring is the most widely used sealing device in the fluid power industry because it is effective, economical and easy to use. It is available in many synthetic rubber formulations, from basic Nitrile to the high performance perfluoroelastomers. The parameters of fluid, pressure, and temperature will determine which O-ring is best suited for a given application. When pressure forces the O-ring, which is in essence a highly viscous fluid with a very high surface tension, to flow within a grove, it flows against and slightly into any gaps. by blocking the clearance, fluids and gases are sealed in and prevented from escaping. The nature of the O-ring is to remember its original shape and attempt to return to it. This elastomeric memory feature is what precludes an O-ring from extruding into the gaps that it is sealing.
When the width of the extrusion gap (diametral clearance) exceeds design recommendations for the operating pressure, back-up rings are often recommended. The most common back-up rings are molded endless from 90 durometer elastomers, PTFE, or filled PTFE materials. These rings can be machined as split or solid(endless), depending on the ease of assembly into the application hardware.