Page 51 - needle bearings

Sealing Devices
NTN

Table 9.3 Clearances
9.2 Combined seals
Seal type Shaft diameter Radial Axial
Several seal types are used in combination for a seal clearance clearance
application under an environment where dust, water 50 and less 0.2ʙ0.4
Oil groove seal
content, etc. exist so much or for mechanical portions Over 50 to 200 0.5ʙ1.0
which are not allowed to be contaminated by lubricant 50 and less 0.2ʙ0.4 1.0ʙ2.0
leak. Labyrinth seal
Over 50 to 200 0.5ʙ1.0 3.0ʙ5.0

9.4 NTN seals
Special-purposed NTN seals are available for the
needle roller bearings.(Refer to Table 9.4 on page A-48.)
For the more detailed information refer to "Dimensions
Table" on page B-233.

9.5 Seal materials and corresponding operating
temperature ranges
Fig. 9.11 Combined non-contact seal The oil seal lip is ordinarily made of nitril rubber, but
Combination of labyrinth seal and oil groove seal acrylic rubber, silicone rubber and fluoro-rubber are used
as the lip material according to atmosphere temperature,
an objective to be sealed, etc. Table 9.5 shows the
operating temperature ranges available for the respective
materials.

Table 9.5 Seal materials and corresponding operating
temperature ranges (Reference)
Seal materials Operating temperature ranges ˚C
Nitril rubber ʵ25ʙʴ100
Acrylic rubber ʵ15ʙʴ130
Silicone rubber ʵ70ʙʴ150
Fluoro-rubber ʵ30ʙʴ180
Felt ʵ40ʙʴ120

9.6 Seal types and allowable speed
The allowable speed for the contact seal type depends
on the surface roughness, accuracy and lubrication
property of sliding surface, operating temperature, etc.
Table 9.6 shows the allowable speed every each seal
type, as a guideline.

Fig. 9.12 Combined seal Table 9.6 Seal types and corresponding allowable speed
Combination of contact seal and non-contact seal (Reference)
Seal types Allowable peripheral speed m/s
Felt seal 4
Grease seal 6
9.3 Clearance setting
Oil seal (Nitril rubber) 15
Oil groove seal and labyrinth seal have the better Oil seal (Fluoro-rubber) 32
sealing effect as the shaft - housing clearance gets the V-ring seal 40
smaller, but the actual clearance is generally selected
from the following clearance values, under consideration
of machining and assembling conditions, shaft
deformation, etc.

A-47