Viton (FKM) Oil Seals - Durus

What Is a Viton Oil Seal?

Viton is a registered trademark of Chemours for fluoroelastomer (FKM) - a synthetic rubber with a chemically saturated fluorocarbon backbone. The fluorine content gives FKM exceptional resistance to heat, oils, fuels, and aggressive chemicals. Viton oil seals identify by an "FKM" or Viton designation on the spec sheet and typically by a V-containing type code in the part number (CV, BV, SBV, VBV, etc.).

Durus Viton oil seals are functionally identical to NBR seals in fit and dimensions - the same 1.000" × 1.625" × 0.250" envelope works in both compounds. The choice between NBR and Viton is driven by operating conditions, not by dimensional fit.

When to Specify Viton

• Continuous temperature above 250°F - NBR begins to harden and crack at sustained temperatures above 250°F. Viton remains flexible to 400°F continuous
• Synthetic lubricants - Synthetic gear oils, ester-based oils, and PAO synthetics swell NBR but are compatible with Viton
• Fuels and gasoline - NBR has limited fuel resistance; modern ethanol-blended gasoline and aromatic fuels require Viton
• Brake fluid (DOT 3, 4, 5.1) - Glycol-ether brake fluids attack NBR; Viton is the standard compound for brake system seals
• Aggressive chemicals - Acids, oxidizers, ketones, and most industrial chemicals are compatible with Viton
• Outdoor / UV exposure - Viton has better ozone and UV resistance than NBR

When NOT to Use Viton

Viton is not universally superior. Avoid in these applications:

• Below -40°F - Viton stiffens at low temperatures; use silicone for extreme cold
• Steam service - Hot water and steam can hydrolyze the fluoroelastomer over time
• Amines and amine-containing fluids - Will attack Viton; use EPDM or another compound
• Cost-sensitive standard applications - Viton typically costs 4-6× more than NBR; reserve for applications where the performance is actually required

Operating Temperature Comparison

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Frequently Asked Questions

What is the temperature range for Viton oil seals?

Viton (FKM/fluorocarbon) oil seals operate from -40°F to 400°F continuous. Short-duration excursions to 450°F are tolerable. For comparison, standard NBR (Buna-N) seals are limited to 250°F continuous and will harden, crack, and fail above that temperature. The expanded high-temperature capability is the primary reason to specify Viton over NBR in industrial applications.

When should I use Viton instead of NBR for an oil seal?

Specify Viton when any of the following apply: continuous operating temperature exceeds 250°F; the fluid being sealed is a fuel, synthetic oil, or aggressive chemical incompatible with NBR; the seal is exposed to outdoor UV and ozone; or the equipment requires extended service life in hot conditions. For standard mineral-oil-lubricated industrial equipment running below 250°F, NBR remains the cost-effective choice.

Is Viton more expensive than NBR oil seals?

Yes. Viton oil seals typically cost 4-6× more than equivalent NBR seals due to the higher cost of the fluoroelastomer raw material. Specify Viton only when the operating conditions actually require its temperature or chemical resistance. For applications well within NBR's capability (mineral oil, under 250°F, clean environment), NBR provides identical sealing function at a fraction of the cost.

Can Viton oil seals be used with water or steam?

Viton can be used with cold water without issue. However, hot water and steam (above approximately 200°F) can slowly hydrolyze the fluoroelastomer over extended exposure, leading to reduced service life. For continuous steam or hot water service, EPDM or specialty steam-rated compounds typically outperform standard Viton. Confirm the specific fluid and temperature with Texas Belting at (888) 203-2358 before specifying Viton for water-based applications.

How do I identify a Viton oil seal versus an NBR seal?

Three indicators: 1) The product description or spec sheet specifies the compound - "Viton (FKM)" or "Fluorocarbon" indicates Viton, "Nitrile" or "NBR" indicates Buna-N. 2) The Durus part number typically includes a V in the type code for Viton compounds - examples: CV, BV, SBV, VBV, VC (Viton C-type). 3) Viton seals are often colored brown or green-tinted versus the standard black of NBR, though this is not universal. Always confirm via the part description.