National Oil and Grease Seals -- Types and Applications
50,000: These spring loaded seals are standard for most general applications, where fluids are to be retained.
10,000: Spring loaded sealing member to retain fluids and felt auxiliary to exclude dust, etc.
20,000: Spring loaded sealing member to retain fluids and opposed leather auxiliary to exclude dust.
30,000: These seals, like the 20,000 series, are designed for fluid retention and dust and dirt exclusion. The selection of either type is dependent on assembly problems.
40,000: Suitable for light sealing conditions or where space prohibits use of more efficient spring loaded types.
70,000: Combination spring loaded opposed sealing members for retention of two fluids.
80,000: External expansion type seals for press fit on shaft or hub to effect sealing at periphery of seal.
90,000: Combination spring loaded sealing members in tandem - used in applications under a head of oil, or for heavy duty applications.