Choosing the Right O-Ring Compound
A three-question shortcut to narrowing down the elastomer you need.
Most compound decisions come down to three questions. Answer them in order and you’ll eliminate the wrong materials fast.
1. What fluid does it touch?
This is the biggest filter. Petroleum oil and fuel rule out EPDM. Hot water and steam rule out standard FKM. Brake fluid (glycol) rules out nitrile. Start by crossing off whatever your media attacks.
2. How hot (or cold) does it get?
Nitrile tops out around 250°F. Need more? FKM handles 400°F. Going very cold or need the widest span? Silicone runs from -75°F to +400°F, but only in static seals.
3. Is the seal moving?
Dynamic (moving) seals need good mechanical strength and abrasion resistance, nitrile and FKM are strong; silicone is not. For a reciprocating rod or rotating shaft, skip the weak compounds no matter how good their temperature rating looks.
Answer those three and you’re usually down to one or two compounds. See the full Materials page for the detailed comparison, or contact us with your fluid and temperature and we’ll help you choose.
