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. |
