6 Things to Consider when Selecting an O-ring

6 Things to Consider when Selecting an O-ring

October 5, 2021


O-rings are one of the most cost-effective sealing products on the market. Their simple design and wide variety of sizes and material compounds make it easy to incorporate them into your next product design. O-rings can be found everywhere – in your kitchen faucet, your car, your cell phone, even the International Space Station. These round rubber rings effectively retain fluids & gases in equipment, seal sensitive components from harsh environments, and protect humans and the environment from chemical contamination.

Proper selection of an O-ring is more than just selecting a common size and material. O-ring technology has come a long way since it’s birth in the late 1800’s. Many synthetic rubber materials (compounds) have been developed for specific types of applications, media compatibility, and more extreme temperature ranges. Here are 6 things to consider when selecting an O-ring.

  1. Media Exposure

Not all elastomers are created equal. Each material type has its own advantages and disadvantages. Using only one type of elastomer across many different applications will eventually cause a failure. Understanding what chemicals, gases, concentrations, temperature of the fluid, and length of exposure should all be taken into consideration when selecting an elastomer.   Knowing your market and industry standards will allow you to select an O-ring that was tested in a similar environment. Sealing Devices can offer a large variety of O-rings with specifications including MIL, USP, FDA, NSF, and many more. 

  1. Temperature Range

With the increased demand from new chemical processes, more efficient engines, electric vehicles, and higher-powered electronics, an overall increase in equipment & process operating temperatures require O-rings to withstand wider temperature ranges than previously required. The need to use these devices in extremely cold environments has also increased. Different O-ring compounds have been specifically formulated to work across a wide variety of temperature ranges. Knowing the temperature range of the application will allow decisions to be made on elastomer type, or if elastomers should be used at all.

  1. Pressure

O-rings are typically specified to hold pressures up to 1500 psi, although instances have been reported of higher pressures being sealed with them. Knowing the pressure that needs to be held can have a direct influence on hardware geometry requirements, elastomer type, and durometer.  Some compounds have been specially formulated for service in extreme low pressure (vacuum), extreme high pressure, and rapid change between the two (rapid decompression).

  1. Type of application

Understanding the type of application is very important when determining your hardware dimensions, elastomer type, and documented specifications. O-rings have multiple possible static and dynamic configurations. Knowing whether the seal will be a static (ie. face seal) or dynamic (ie. radial seal, or piston seal) is the first step in determining your groove dimensions, assembly clearances and manufacturing tolerances need to incorporate the O-ring.

  1. Available load

Load is often overlooked in O-ring design. In order to effectively seal, O-rings must be compressed. The opposing force of the compressed O-ring pushing back on the housing is similar to a spring force and is how an O-ring provides sealing. In a correctly designed O-ring application, a squeeze of anywhere between 19% and 30% is recommended (face seals). The amount of available load can have a direct impact on the durometer chosen and vice versa.

  1. Size

Designing your sealing application using a standard size O-ring can provide a cost-effective solution without the need for custom tooling fees and long lead times. There are over 400 standard AS 568A size O-rings available as well as metric options and those specified by Military Standard specifications and organizations such as SAE. Custom sized Spliced & Vulcanized rings and custom molded parts are also available from Sealing Devices.  You can utilize our O-ring size chart to help you with the process.


Let Sealing Devices collaborate on your next complex sealing challenge and offer an O-ring solution that will last through your most extreme project requirements.  Contact us.