Felt Seal is normally used with bearing housing of variety SN, PDN, TVN, Flanged housing, SD500, SD600, SD30 series. For SDG type also felt seal is used along with labyrinth seal.
The felt is a simple and adequate seal with grease lubrication at peripheral speeds up to 4 m/s. It can be used at temperatures of -40 to +100 degree C. Felt seal is contact seal rubbing on shaft surface. It can also be used at higher speeds but a small gap will then generally be formed between the felt and the shaft, so that the sealing action becomes that of a non-rubbing gap- type seal.
Plummer Block housing of series SNA, SNH and SNL are available with split Felt Seals consisting of oiled felt incorporated in the two halves of an aluminum alloy ring. Such seals are designated as TC or TSNA 500C & TSNA 600C. There is an external groove in alloy ring halves where O- section rubber cord is inserted while fitting the seal halves into the bearing housing. The O-section cords provide an effective contact between the housing and the alloy ring in addition to preventing the ring rotation in the housing.
Bearing Housings of series SNA 205 to SNA 218 , SNH 205 to SNH 218 and SNL 205 to SNL 218 can be supplied with felt seals which are loose felt strips and which are fitted directly in housing grooves (without alloy rings). Before fitting, the felt strips should be immersed in hot oil for a few minutes. The maximum permissible misalignment of the shaft is approx 0.5 degree. It is recommended that the surface roughness of shaft should not exceed Ra = 3.2 micro.
Generally felt seal is not suitable for oil lubrication in housing and vertical mounting but suitable for axial shaft displacement. Felt seal can be selected for external conditions with dust, sand, grit, sharp objects, clippings, splinters and sunshine, but it is less suitable with splashing fluids.