Buna-N, also known as Nitrile. The most common rubber used in Mechanical seals. Suitable for water, petroleum oils and fluids, mild chemicals. Not suitable for Biodiesel/Biofuel, Propylene glycol, strong acids or caustics. Life expectancy drops as water temperatures rise above 180F.
EPR also known as EPM, EPDM and Ethylene propylene. Commonly used for hot water, Propylene glycol, hi pH solutions. Not suitable for petroleum based fluids and oils.
Viton also known as flourocarbon. Used for many chemical and higher temperature applications, including Biodiesel/Biofuel. Not suitable for Propylene glycol. Viton can be recognized by its weight. It is approximately 50% more dense than Buna-N or EPR which is enough to be measured on a high resolution scale.
Aflas is serviceable in applications involving strong acids and bases, high temperatures, steam and petroleum products. It is considered a premium priced rubber and is not readily available except as o-rings.
Neoprene is not commonly used in mechanical seals. Special applications include refrigerants and ammonia/oil service
PTFE more popularly known by DuPont's trademark Teflon is virtually chemically inert and can operate at high temperatures. Its draw back is that it has poor memory (ability to bounce back to shape) which limits its applications.
Carbon is black, can be scratched, and is the most common face material - good for most chemicals. Can be used to mate with most any other face material
- P-66 Carbon
P-66 carbon is black, harder than standard carbon and used to reduce damage to faces caused by abrasives or poor lubrication.
- Molded Plastic
Molded plastic looks like carbon, is a less expensive substitute for carbon in light duty service such as pool pumps.
Ceramic is white or off white and is the second most common face material- good for most chemicals. Can only be mated with molded plastic or carbon. Not to be used in applications where the seal can see a quick drastic change in temperature as the ceramic can crack (thermal shock). This problem is common in portable pumps that start up dry until they prime. Ceramics are brittle and can be damaged from mechanical shock.
Ni-resist looks like steel. This is a high nickel content cast iron and can only be mated with molded plastic or carbons. It is softer than ceramic and subject to corrosion. Commonly used where seal is subject to thermal shock. Pump manufacturers will supply as original equipment in order to reduce warranty claims due to mechanical and thermal shock issues.
- Silicon Carbide
Silicon Carbide is dark grey, light weight and very hard. It cannot be scratched and is brittle like ceramic but thermally stable. Can be mated with carbon, silicon carbide or tungsten carbide. Used to reduce wear from abrasive media, poor lubrication and thermal shocking.
- Tungsten Carbide
Tungsten carbide looks like steel but is much heavier. It is very hard, cannot be scratched and is thermally stable. It is not brittle and can be mated with carbon, silicon carbide and tungsten carbide. Used to reduce wear from abrasive media.