Seal faces, elastomers and material combinations

Some knowledge of the different materials that are common within mechanical seals is important to determine the correct seal when it comes to seal faces combinations and the material of the o-rings.

With the mechanical seal we are dealing with two seals, primary and secondary. The primary seal is the seal created by the hydrodynamic film between the two (very flat) seal faces. The secondary seal is the seal between the stator part and the housing and the rotor part on the shaft. The secondary seal is (almost always) achieved by using o-rings or gaskets (elastomers). Below you will find a brief overview of the most commonly used materials and combinations. Contact Qseals directly for advice.

The metal housing and the other metal parts of the seal are usually made of stainless steel.

Primary Seal – Seal Faces

Material Description
Ceramic Alumina (CER) All-round seal, limited pressure / temperature range. Brittle material, easily affected by abrasive liquids, limited corrosion resistance.
Stainless Steel (SS) Type 304 or 316, used for most metal parts of the seal.
Carbon (graphite) (CAR) Brittle material, easily affected by abrasive liquids. Better resistant to dry running.
Silicon Carbide (SiC) Very wear-resistant but brittle material, very resistant to corrosion.
Tungsten Carbide (TC) Very wear-resistant and sturdy material, poorly resistant to dry running.

Secondary Seal – Elastomers

Use Material Clean with Temperature Peak Temperature
Oil / grease / solvents Nitrile (NBR) -45° tot +120° 150°
Water / steam EPDM (EPR) Lye / Caustic Soda -40° tot +150° 180°
Chemicals Viton (FKM, FPM) Acid / Hydrochloric / Nitric acid -33° tot +200° 230°
All FEP Viton (FKM,FPM) Lye / Caustic soda / Acid / Hydrochloric acid / Nitric acid -20° tot +210° 250°
All FEP Silicone Lye / Caustic soda / Acid / Hydrochloric acid / Nitric acid -60° tot +220° 250°
All AFLAS (TFE/P) Lye / Caustic soda / Acid / Hydrochloric acid / Nitric acid -10° tot +200° 250°
All Kalrez (FFKM) Lye / Caustic soda / Acid / Hydrochloric acid / Nitric acid -40° tot +300° 330°

*Lye = Sodium hydroxide = Caustic Soda

Additional material information

NBR Good resistance to oils, less resistant to chemicals and high temperatures.
EPDM Good resistance to alkalis, less resistant to acids and other chemicals.
Viton Good resistance to acids and other chemicals, less resistant to lye.
FEP Viton Viton with Teflon coating, versatile, resistant to high temperatures and chemicals.
FEP Silicone Silicone with Teflon coating, versatile, also resistant to low temperatures and chemicals.
AFLAS Fluoroelastomer with high electrical insulation value and very good resistance to oils and steam.
Kalrez Perfluoroelastomer applied under extreme conditions or for tool life extension.

[slideshow]

Need help?

We gladly help you with free advice. Our specialists are available for you each workday from 08:00 till 18:00! Contact us via:

+31 38 85 21 801