Page 199 - Rollingbearings

External sealing
Contact seals good, and contamination levels are minimal,  WARNING
a lower hardness can be acceptable. For oil
There are four common types of contact lubrication, to avoid the pumping effect Safety precautions for luoro rubber
seals: induced by helical grinding marks, SKF rec- and Polytetraluoroethylene
ommends plunge grinding the counterface. Fluoro rubber (FKM) and Polytetraluo-
• radial shaft seals If the primary purpose of the radial shaft roethylene (PTFE) are very stable and
• V-ring seals seal is lubricant retention, the seal should be harmless up to normal operating tem-
• axial clamp seals mounted with the lip facing inward (ig. 14). peratures of 200 °C (390 °F) However,
• mechanical seals If the primary purpose is to exclude contam- if exposed to temperatures above
inants, the lip should face outward, away 300 °C (570 °F), such as ire or the open
The seal type selected for a particular appli- from the bearing (ig. 15). lame of a cutting torch, FKM and PTFE
cation typically depends on: SKF can also supply machined polyur- give off hazardous fumes These fumes
ethane radial shaft seals. can be harmful if inhaled, as well as if
• the primary purpose of the seal (to retain they contact the eyes In addition, once
lubricant or exclude contaminants) the seals have been heated to such tem-
• the type of lubricant (oil, grease or other) peratures, they are dangerous to handle
• the operating conditions (speed, tempera- even after they have cooled Therefore,
ture, pressure and environment) they should never come in contact with
the skin
Radial shaft seals If it is necessary to handle bearings
with seals that have been subjected to
Radial shaft seals (ig. 14 and ig. 15) are high temperatures, such as when dis-
contact seals that are used for oil and grease mounting the bearing, the following
lubricated applications For detailed infor- safety precautions should be observed:
mation, refer to the SKF catalogue Industrial
shaft seals These ready-to-mount compon- • Always wear protective goggles,
ents typically consist of a metal reinforce- gloves and appropriate breathing
ment or casing, a synthetic rubber body, a apparatus
seal lip and a garter spring The seal lip is • Place all of the remains of the seals in Sealing, mounting and dismounting
pressed against the shaft by the garter an airtight plastic container marked
spring Depending on the seal material and Fig. 14 with a symbol for “material will etch”
medium to be retained and/or excluded, Radial shaft seal, mounted for lubricant • Follow the safety precautions in the
commonly used materials for radial shaft retention appropriate safety data sheet (SDS)
seals can be used at temperatures between
–55 °C (–65 °F) and +200 °C (390 °F) If there is contact with the seals, wash
The seal counterface, that part of the hands with soap and plenty of water
shaft where the seal lip makes contact, is of and, if contact has been made with the
vital importance to sealing effectiveness The eyes, lush eyes with plenty of water and B.8
surface hardness of the counterface should consult a doctor immediately If the
be at least 45 HRC at a depth of at least fumes have been inhaled, consult a doc-
0,3 mm. The surface texture should be in tor immediately
accordance with ISO 4288 and within the The user is responsible for the correct
guidelines of Ra = 0,2 to 0,5 μm. In applica- use of the product during its service life
tions where speeds are low, lubrication is and its proper disposal SKF takes no
responsibility for the improper handling
Fig. 13 Fig. 15
of FKM or PTFE, or for any injury result-
Oil caught by rotating linger at the seal Radial shaft seal, mounted for contami- ing from their use
nant exclusion

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