Needle Roller Bearings - Ntn-snr.com

Sealing Devices
NTN
9.2 Combined seals
Several seal types are used in combination for a seal
application under an environment where dust, water
content, etc. exist so much or for mechanical portions
which are not allowed to be contaminated by lubricant
leak.
Table 9.3 Clearances
Seal type
Oil groove seal
Labyrinth seal
Shaft diameter
Radial
clearance
50 and less 0.20.4
Over 50 to 200 0.51.0
50 and less 0.20.4
Over 50 to 200 0.51.0
Axial
clearance
1.02.0
3.05.0
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.
Fig. 9.11 Combined non-contact seal
Combination of labyrinth seal and oil groove seal
9.5 Seal materials and corresponding operating
temperature ranges
The oil seal lip is ordinarily made of nitril rubber, but
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
Nitril rubber
Acrylic rubber
Silicone rubber
Fluoro-rubber
Felt
Operating temperature ranges ˚C
25100
15130
70150
30180
40120
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
Combination of contact seal and non-contact seal
Table 9.6 Seal types and corresponding allowable speed
(Reference)
9.3 Clearance setting
Oil groove seal and labyrinth seal have the better
sealing effect as the shaft - housing clearance gets the
smaller, but the actual clearance is generally selected
from the following clearance values, under consideration
of machining and assembling conditions, shaft
deformation, etc.
Seal types
Felt seal
Grease seal
Oil seal (Nitril rubber)
Oil seal (Fluoro-rubber)
V-ring seal
Allowable peripheral speed m/s
4
6
15
32
40
A-47