Known as the smallest gaskets, o-rings are donut-like, round gaskets that seal off space between both static and moving parts to prevent leaks. O-rings are fairly inexpensive to manufacture and quite effective, making them very popular in a variety of industries. Industries include: the medical field, aerospace, aviation, chemical processing, water treatment and even, occasionally, jewelry making. Overall, o-rings serve pneumatic, hydraulic and vacuum flow applications.
The o-ring seal is achieved when its disc-shaped cross-section is deformed by compression. The more pressure is applied inside or outside the o-ring, the stronger the seal becomes. The sealing capabilities of an o-ring, however, are not based on how well it deforms. Rather, they are based on its resilience, which is measured by its ability to hold its original shape after deformation.
O-rings may be made with any of a broad range of natural and synthetic elastomers. The choice of which depends on the properties a manufacturer seek and a material’s reaction to that which it seals, such as sealing pressure, chemical compatibility, temperature and lubrication requirements. Read More…
Rubber is a very popular material for making o-rings; the most frequently used rubber types include teflon, viton, silicone, neoprene and nitrile. Since aerospace applications like brake systems and engine turbines require extremely strong and resilient o-rings, theirs are usually made from materials like EPDM, perfluoroelastomer and fluorosilicone.
Petro-chemical hydraulic applications, which include oil refining, water treatment and chemical processing, use viton, nitrile, perfluoroelastomer, teflon and the like because they are highly resistant to fuels and chemicals. Heat exchangers and chiller systems rely on neoprene o-rings to seal refrigerants, like freon, inside. Other options include polyamides, indium, melt processible rubber, saniflour, clear plastic and various metals.
Clear plastic is used routinely in hospitals and medical care centers, for IVs and other clear tubing. Because they are so inexpensive to make, rubber o-rings and silicone o-rings sometimes make appearances around earplugs and as necklace strings. Silicone also lends its support to applications that require a material high in resistance to fast, wide temperature swings, extreme dry heat and UV weathering.
O-rings are durable, but they still may require supportive coatings. For example, some o-rings require lubricants. Typically, this is only required with o-rings that join moving joints; the lubricant helps reduce wear and abrasions. While lubricants are often made from elastomers, manufacturers must take care to not pair a o-ring with a lubricant made of the same material, or the o-ring will erode.
To protect an an o-ring from natural deterioration and the effects of harmful chemicals, manufacturers may consider encasing it in Teflon. However, this material is only suitable for use with some applications because, though Teflon is strongest synthetic material available for use with o-rings, it is not very flexible.
The upkeep of o-rings is incredibly important. Without diligent adherence to quality control regulations, disaster could strike; this was the case in the Challenger space shuttle tragedy of 1986, which was traced back to a faulty o-ring on the rocket boosters.
This particular o-ring failed because, that morning, below freezing temperatures caused it to freeze in a deformed position. So, during lift-off, it couldn’t create a proper seal and the space shuttle exploded. The research into and the subsequent use of materials with higher endurance properties were a direct result of this fatal accident.
In addition, regulations related to packaging, labeling and expiration dates tightened drastically. Regularly examine your gaskets for stress and fractures using prescribed procedures, such as inspecting critical application o-rings under UV lights.