Page 70 - SKF-bearing-housings

Split plummer block housings SNL 2, 3, 5 and 6 series

Four-lip seals In applications where bearings are mounted
Four-lip seals replace the former double-lip on a plain shaft with an adapter sleeve, split
seals (TSN .. G). When compared to double-lip felt ring seals are typically used.
seals, the new seals are more effective. They If the bearings are to be installed on a
also generate less friction, which enables stepped shaft with a cylindrical seat (housing
higher shaft speeds. Four-lip seals are hori- sizes 205 to 218 inclusive), loose felt strips
zontally split and easy to mount. can be used. The strips are 170 mm in length.
The permissible angular misalignment for They should be cut to the correct length and
seals mounted on shafts ≤ 100 mm in diam- soaked in hot oil for a few minutes prior to
eter is approximately 1° and approximately mounting. The required number of strips per
0,5° for larger shafts. housing (for both sides) is listed in the product
tables († pages 86 to 137).
V-ring seals
V-ring seals consist of a V-ring and a sheet Labyrinth seals
steel sealing washer with a vulcanized rubber For applications where there are high speeds
lip. The rubber lip fits into the seal groove in or extreme temperatures, SKF recommends
the housing. The washer is protected against using labyrinth seals. Labyrinth rings, mounted
corrosion. on the shaft, form a multi-stage labyrinth seal
V-rings can accommodate circumferential with the housing seal grooves. Hollow, silicone
speeds up to 7 m/s. For circumferential speeds rubber cords (2 ¥ 4 mm), supplied with the
between 7 and 12 m/s, they should be located rings, hold the rings in place on the shaft.
axially on the shaft. At speeds above 12 m/s,
a support ring must be used to prevent the
seal from lifting. Recommended dimensions Taconite heavy-duty seals with a radial
for appropriate support rings for axial and labyrinth
radial location are provided in table 4. Hous- For bearing arrangements that must operate
ing sizes 205 to 211 and 306 to 314 cannot be under highly contaminated conditions, such as
used with a support ring and are therefore not those encountered in mining, taconite heavy-
suitable for V-ring seals at operating speeds duty seals, which can be filled with grease, are
above 7 m/s. recommended. Grease enhances the sealing
The permissible angular misalignment for effect and extends the service life of the seals.
V-ring seals is approximately 1,5° for a 50 mm Taconite heavy-duty seals are labyrinth
shaft decreasing to approximately 1° for shaft seals combined with a V-ring seal. The inner
diameters ≥ 150 mm. ring of the labyrinth seal is solid but the outer
The axial movement of the shaft relative ring is split. They can be relubricated via a
to the housing is limited to ±1 mm for shaft grease fitting in the main body of the seal.
diameters up to 65 mm, to approximately The axial movement of the shaft relative
±1,2 mm for shaft diameters up to 100 mm to the housing is limited to ±1 mm for shaft
and to approximately ±1,5 mm for larger shaft diameters up to 65 mm, approximately
diameters. ±1,2 mm for shaft diameters up to 100 mm
For arrangements with a vertical shaft, the and ±1,5 mm for larger shaft diameters.
V-ring of the lower seal should be mounted
inside the housing.

Felt seals or strips
Felt seals or strips are simple and effective. At
circumferential speeds above 4 m/s, a small
gap forms between the felt and shaft, trans-
forming the contact seal into a non- contact,
gap-type seal.

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