Page 200 - Rollingbearings

B.8 Sealing, mounting and dismounting
V-ring seals Axial clamp seals Other seals
V-ring seals (ig. 16) can be used with either Axial clamp seals (ig. 18) are used as sec- Felt seals (ig. 20) are generally used with
oil or grease lubrication The elastic rubber ondary seals for large-diameter shafts in grease lubrication They are simple, cost -
body of the seal grips the shaft and rotates applications where protection is required for effective and can be used at circumferential
with it, while the seal lip exerts a light axial the primary seal They are clamped in posi- speeds of up to 4 m/s and at operating tem-
pressure on a stationary component, such as tion on a non- rotating component and seal peratures up to 100 °C (210 °F) The coun-
a housing Depending on the material, axially against a rotating counterface For terface should be ground to a surface texture
V-rings can be used at operating tempera- this type of seal, it is suficient if the counter- of Ra ≤ 3,2 μm The effectiveness of a felt
tures between –40 °C (–40 °F) and face is ine-turned and has a surface texture seal can be improved substantially by
+200 °C (390 °F) They are simple to install of Ra = 2,5 μm mounting a simple labyrinth seal as a sec-
and permit relatively large angular misalign- ondary seal Before being inserted in the
ments of the shaft at low speeds Mechanical seals housing groove, felt seals should be soaked
The recommended counterface surface in oil at about 80 °C (175 °F) prior to
inish (surface texture) depends on the cir- Mechanical seals (ig. 19) are used to seal mounting
cumferential speed (table 1) At circumfer- grease or oil lubricated applications, where Metal seals (ig. 21) are simple, cost-
ential speeds above 8 m/s, the body of the speeds are relatively low and operating con- effective and space-saving seals for grease
seal must be located axially on the shaft At ditions arduous Mechanical seals consist of lubricated bearings The seals are clamped
speeds above 12 m/s, the body must be pre- two sliding steel rings with inely inished against either the inner or outer ring and
vented from lifting from the shaft A sheet sealing surfaces and two Belleville rubber exert a resilient axial pressure against the
metal support ring can be used to do this compound washers, which position the slid- other ring After a certain running-in period,
When circumferential speeds exceed 15 m/s, ing rings in the housing bore and provide the a narrow gap forms and these become
the seal lip lifts away from the counterface necessary preload force to the sealing sur- non-contact seals
Sealing, mounting and dismounting seal, which acts as a linger, repelling dirt Recommended counterface surface inish Table 1
faces There are no special requirements for
and the V-ring becomes a gap-type seal
V -ring seals have good sealing abilities,
the mating surfaces in the housing bore
which can be attributed to the body of the
and luids As a result, these seals are gener-
ally arranged outside the housing in grease
lubricated applications and inside the hous-
ing, with the lip pointing away from the
bearing, in oil lubricated applications Used
as a secondary seal, V -rings protect the pri-
mary seal from excessive contaminants and

For added protection in extremely con-
m/s
μm
taminated applications, SKF also supplies
B.8 moisture Circumferential speed ft/min Surface inish Ra μin
MVR seals (ig. 17 and SKF catalogue Indus-
>10
16–32
0,4–0,8
>1 969
trial shaft seals)
984–1 969
0,8–1,6
32–64
5–10
1–5 199–984 1,6–2,0 64–80
<1 <199 2,0–2,5 80–100
The surface inish must not be lower than Ra = 0,05 μm (2 μin )
Fig. 16 Fig. 17 Fig. 18
V-ring seal MVR seal designs Axial clamp seal

MVR1 MVR2

198