O-Rings are a critical sealing element in in today’s industrial world. No matter what mechanical applications an industry develops, O-Rings are necessary to create and maintain the sealing of fluids and gases in Industries rangeing from Aerospace to your home faucet.
O-Rings are basically circularly shaped rubber used to seal a joint between two flat surfaces. Both surfaces can be static, but often one is dynamic (has motion). Because o-rings conform but also have recovery, they are able to adapt and seal dynamic surfaces.
The varieties of these circular seals available in the market, however, can be very confusing and overwhelming. Choose the wrong O-Ring and your application will fail. Choose the right one and you may have a seal for 20 years or longer.
The real problem is of choosing the right rubber compound for the job. Most rubbers are compounds meaning they are blends of various types of rubber with a primary type of material. Selecting a reputable source helps ensure the compound you are getting will perform as expected. Some cheap imports are loaded with clay or inferior material to make them less expensive. There are many primary rubber types including Aflas, SBR, NBR, Buna-N (Nitrile), Silicon, Buna-N, EPDM, Kalrez, PTFE, FEP encapsulated and Viton. Beyond that the difference in compunds makes hundreds of version of each. Some with higher or lower swelling rates when exposed to oil, or higher or lower temperature resistance all depending on the compound. Color can be added: Silicone can be translusent, orange or Red for example. Viton is often colored brown just to distinguish the expensive Viton o-ring from an inexpensive Buna-N o-ring.
Not only does the material vary from one O-Ring to another, the size plays an important role as well. The standard sizes of the O-Rings manufactured can follow multiple standards including AS-568 (USA Aerospace Standard) Metric, BS (British Standard) JS (Japanese Standard) as well. O-Rings also come in a variety of shapes. The 3 common shapes are Round, Square Cut and Quad rings (also called x-rings).
With all these variations of O-Rings, how do you choose the right one? The answer can be simple or complicated depending on the application. In general the key factors are will the selected material withstand the media being sealed, at the given temperature and pressure. Secondly, is the application static or dynamic. If static, chemical compatibility, temperature and pressure are the key factors (like a gasket). If dynamic however, the speed and surface finish must also be considered. Friction can easliy generate excessive heat. A rough surface can act as an abrasive and greatly reduced the life span of the o-ring.
If your installing an o-ring into an existing application much of the work has been done for you. If however your in the design stage (design guides should be consulted) you must consider how the o-ring is to be held in place, the size of the o-ring groove and if a back-up ring is required to elevate the amount of pressure the o-ring can seal. O-rings seal well because they are conformable, but that same conformability can work against the seal and allow it to be extruded in high pressure applications.
Just consider its usage and the choice can be made. The choice of O-Rings can be made based on the application it is to be used in, the speed of the application, the temperature, pressure, and strength conditions that it might need to endure, and the size of the groove it needs to fit in.
American Seal & Packing O-Ring distributes a complete range of o-ring types, shapes and sizes. Its meticulous staff can also helps you pick up the correct material as well as the size of the o-ring for your application. The O-Ring kits assembled by American Seal and Packing O-Ring sales consists different standard sizes of rings that can be worked with readily in the industry. All these O-Rings are tried and tested on different parameters to provide solid, impeccable seals.