Hydraulic systems, pumps or cylinders that convey gases or liquids to perform certain functions most likely have o-rings installed to prevent leakage. These mechanical devices, in various industries, are constantly being redesigned to work more efficiently or cost effectively. As these mechanical devices evolve, so must the o-ring.
To effectively prevent leaks, the o-ring’s characteristics and material construction must withstand the properties of any gas or liquid, extreme temperatures or high pressures that may be a part of the mechanical device’s functions or applications. As a result, innovations in o-ring sealing technology are continually being developed to accommodate these ever-evolving conditions.
Let’s take a look at how advances in o-ring sealing technology and material development help the o-ring adapt to extreme conditions.
The o-ring usually fits into a groove on one of two mating surfaces. When the two mating surfaces are connected, the o-ring in between compresses to form a barrier against leaks. Usually, o-rings are made out of some elastomeric material like silicon or rubber, but can be made out of plastics to suit the environment.
Extreme applications and conditions require an o-ring to perform without failure, and the materials and characteristics of o-rings have been developed to adapt to those extremities. Failure is not an option, especially in the automotive, aerospace, pharmaceutical, military and medical device industries.
An o-ring’s material can be made from a combination of various chemical compounds to improve the likelihood of zero leakage. These chemical compounds and materials that make the o-ring able to perform under certain conditions can include:
- Inert fillers
- Active chemicals
- Special additives
For example, plasticizers can be added to improve low-temperature properties while inert fillers can be added to improve physical properties.
O-rings used as seals in aircraft engines and automotive fuel handling systems should be made of a combination of chemical compounds and materials that:
- Withstand high temperatures
- Have a longer lifespan under constant use with a low compression set
- Resist against swell in high octane and oxygenated fuel blends, especially Ethanol/Methanol-blended gasoline
- Should not release volatile materials when heated
A material best suited for extreme conditions, particularly in the aerospace and automotive industries, is an o-ring made of fluorocarbon-based compounds. Here are the characteristics that this material can offer when considering an o-ring for extreme condition design purposes:
- Standard Compound: -13°F to +446°F for extremely high temperatures
- Unique Compounds: -40°F to +446°F for extreme low and high temperatures
- Shore A Hardness: 45 to 90
It is paramount to consider the application and environment in designing hydraulic systems, pumps or cylinders when deciding on the proper o-ring. Two characteristics have to be considered:
- The temperature range that the o-ring will have to operate in
- The pressure range that the o-ring will have to seal against
Knowing how much pressure the o-ring will have to seal against or the application used will help decide what Shore A hardness of material should be used. The Shore A hardness scale measures a material from extremely pliable to rigid with almost no flexibility. So on the Shore A scale, a 30 Shore A is softer than an 80 Shore A. Hydraulic o-rings usually fall between 70 to 90 Shore A. The idea is for the o-ring to be flexible enough to compress and form a seal, but sturdy enough to withstand pressure.
After reading about the different types of materials and characteristics of o-rings and the applications they can be used for, you can now realize the innovation in o-rings and sealing devices. An o-ring may look very basic, but material choices and characteristics can differ from one o-ring to another. Therefore, choosing the correct o-ring for the proper application will make everyone safe around it.