What is an O-ring?
There are many definitions of O-rings. In essence, it is a seal that has the form of a ring with a circular cross-section. O-rings are typically made of rubber and are primarily used for sealing purposes in swivelling joints.
There are many different types of O-rings, and how they look and what they are made of depends on their application. O-rings play an integral part in modern-day engineering and O-ring failure have been known to have disastrous consequences.
When it comes to engineering, nothing beats the importance of proper sealing and isolation. Your selection of O-rings can have a significant influence on the success of your prototype, vehicle or design. O-rings also play a pivotal role in ensuring durability, performance, and minimalisation of the risk of failure. Let’s take a look at some of the things that you should consider when selecting an O-ring.
Material
The material that you choose has to be compatible with other factors and applications of your design. If the material of your O-ring design is not compatible with the rest of your design, it can be detrimental to the functionality and overall effectiveness.
The O-ring material should be compatible with the operating fluid. If not, the operating fluid can cause the O-ring to swell and deteriorate, diminishing it’s sealing ability and increase the risk of failure.
The O-ring material should also be able to withstand the fluctuations in temperature. Temperatures that are too cold can harden the O-ring, causing it to snap. If the O-ring is made from the wrong materials, temperatures that are too high can also reduce the O-ring’s sealing abilities.
If the overall design is applied in a manner that changes the pressure around the O-ring, its material should enable the O-ring to maintain its sealing abilities nonetheless.
Seal Grove Surface
The seal groove surface of the O-ring housing is particularly important to ensure maximum performance and effectiveness of the overall design. The surface is too rough; there can be microscopic openings between the O-ring itself and the surface of the seal housing. This reduces the O-ring’s ability to seal the surface effectively. A sealing house surface that is too smooth, on the other hand, can cause an aqua-plane effect and also diminishes the O-ring’s sealing ability. It is, therefore, clear that the surface roughness should be somewhere in between.
Generally speaking, a seal groove surface of 16 rms will ensure optimal sealing for gases where a sealing grove surface of 32 rms works best for fluids. If the objective is dynamic applications, make sure that the O-ring’s surface housing has an rms of anything between 6 to 18.
Conclusion
Before selecting an O-ring for your application, it is important to ensure that you understand the sealing requirements of your design. Keep all the circumstances of the design’s functionality in mind, including temperature and pressure. Make sure that the O-ring material is compatible with the operating fluid and that the roughness of the housing surface allows for optimal sealing.
