Hydraulic Seals and Pneumatic Seals
Many seals on the market are interchangeable between hydraulic and pneumatic applications, therefore it is the details of your application that will determine which seal to use. For example, you will need to know your media, pressure, temperature, and speed/velocity.
Hydraulic seals can be made from a variety of materials and durometers such as rubber, fabric reinforced rubber, polyurethane, PTFE, and PTFE blends. The type of material is determined by the specific operating conditions or limits of your system.
Pneumatic seals are predominantly made using a softer elastomer such as rubber. There have been many improvements in materials over the years with new technology creating internally lubricated elastomers for pneumatic applications with little to no system lubrication. Like the hydraulic seals, the type of material is determined by the specific operating conditions or limits of your system.
Two Basic Types of Seals
There are basically two different types of seals, pure lip seal and pure squeeze seal. There are also three basic shapes of seals, round, square and rectangular. Below is an illustration of a lip seal and a squeeze seal in their “free” state as they would appear outside the groove, and how the seal would appear when installed in the groove. Also, an illustration of the three basic seal shapes.
Below is a continuum with pure lip seals on the left where there is low friction, wear and sealability. On the right is pure squeeze seals where friction, wear and sealability are high. The compromise seals in the middle will have varying amounts of friction, wear and sealability.
As we move from left to right on the continuum, we move from simply bending the seal lips to displacing increasing amounts of material. The more material displaced the more mechanical squeeze generated, the greater the sealability but also friction and wear increase. As friction and wear increases seal life decreases.
In general, most pneumatic seals can be used as a hydraulic seal in applications of lower psi. Conversely, most hydraulic seals cannot be used as a substitute for pneumatic seals due to the hardness of the material. As stated earlier, your specific application will determine which seal is best for you.
If you have any questions about seals you can contact Patriot Fluid Power anytime.