Truefit Engineering Co. Ltd. Waliv, Thane, Maharashtra

Labyrinth Seal is used with SN, SNA, SNH, SNL, SD and SAF type housings. For large Plummer block housings, like SDJ, SDG SBD, THD types, the Labyrinth Seal is the preferred choice. For SOFN housings the labyrinth seals are supplied with internal design having additional external oil traps and are called ‘Sealing Collar’ When operating conditions are severe or when the speed is high, Labyrinth seals are recommended. To prevent rotation of the seal on the shaft, on O-section cord of synthetic rubber is incorporated in a groove provided in the labyrinth ring bore. The maximum permissible misalignment of the shaft in approximately 0.30. The labyrinth seal can be used at temperature range of - 500 C to + 200.0 C, Labyrinth Seals are suitable for grease or oil lubrication and axial shaft displacement but not suitable for vertical mounting. For external condition with dust, sand, grit, sharp objects, clippings, splinters and sunshine Labyrinth seal is suitable but it is unsuitable with splashing fluids.

The felt is a simple and adequate seal with grease lubrication at peripheral speeds up to 4 ms. 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.