Mechanical Face Seals are a special form of mechanical seals. They are also known under other designations, such as lifetime seals, floating seals, duo cone seals, toric seals and heavy duty seals.
Types:
There are two different types of Mechanical Face Seals: The most common form is Type DO, which is characterized by the use of an O Ring as the secondary sealing element.

Type DF, on the other hand, has an elastomer with a diamond-shaped cross section as a secondary sealing element instead of the O Ring.

Both types consist of two identical metal seal rings which seal against each other on a lapped seal face.
Technical data for metal seal rings:
Material: High-alloy, Corrosion-Resistant Cast Iron
Process: Cast
Hardness: HRC 65 To 72
Life time: More than 4000 hours