Felt ring seals are simple but efficient seals for use with grease lubrication. They can be operated at peripheral speeds of up to 4 m/s (800 ft/min). The seals can be used at higher speeds, but a small gap forms between the felt and the shaft. As a result the seals become non-rubbing gap-type seals.
For pillow block housings with bearings on adapter sleeves and shafts not exceeding a surface roughness of Ra 3.2 μm, the felt ring seals are split. Oil-impregnated felt is inserted into Light Alloy half-rings and the seals inserted into the grooves of the housing. The rubber O-section cords should be put into the grooves first as they prevent the seals from turning.
SNL pillow block housings for bearings mounted on the cylindrical seatings of stepped shafts, sizes 205 to 218 inclusive, can also be supplied with felt seals. In this case, the seals consist of loose felt strips that can be inserted into the sealing grooves. Before mounting the FS felt strips, soak for a few minutes in hot oil. The permissible angular misalignment for felt seals is approximately 0.5°. The seal counterface on the shaft should be ground and the surface roughness should not exceed Ra 3.2 μm (125 RMS). The axial movement on the shaft relative to the housing is not limited when felt seals are used. The ready-to-mount felt ring seals (in Light Alloy half-rings) are always supplied in packs of two. The felt ring seals are identified by the designation prefix TSN followed by the size identification and the suffix C, for example, TSN 511 C.

Plummer Blocks, Bearing Lubrication and Accessories