Relubrication interval
The period during which a grease lubricated bearing will fuction
satisfactorily without relubrication is dependent on the bearing type,
size, speed, operating temperature and the grease used. The relubrication
intervals (hours of operation) obtained from Diagram 1 are valid for
bearings in stationary machines where loading conditions are normal. The
diagram is based on the use of an age-resistant good quality lithium
grease and is valid for bearing temperatures of 70 °C
(158 °F)
measured on the outer ring. The intervals should be halved for every 15 °C
(27 °F) increase above 70 °C (158 °F), but the
maximum permissible operating temperature for the grease should obviously
not be exceeded. Generally for temperatures above 80 °C (176 °F)
a high temperature grease
is recommended.
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Conversely, if operating
temperatures are lower than 70 °C (176 °F), the intervals can be lengthened to about twice the
values for operating temperatures of 50 °C (122 °F) and below. It should be noted, however,
that relubrication intervals may vary significantly even where apparently similar greases are
used.
For small bearings, particularly deep groove ball bearings, the relubrication interval is often
longer than the life of the bearing application. Therefore, relubrication is normally not
required.
In such cases, ball bearings fitted with shields or seals and which are "lubricated-for-life" may be used. Where there is a risk of the grease becoming contaminated, the
relubrication intervals should be reduced. This reduction also applies to applications where
the grease is required to seal against moisture, e.g. bearings in papermaking machines.
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| Relubrication |
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| The amount of grease needed for relubrication can be obtained from the equation
below |
| Gp |
= |
0,005 D B |
| where |
| Gp |
= |
grease quantity, g |
| D |
= |
bearing outside diameter, mm |
| B |
= |
total bearing width, mm |
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(for thrust bearings, use H = total height) |
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When operating conditions are such that relubrication can be carried out at infrequent
intervals, it is sufficient if the bearing housing is accessible and can be opened easily. The cap
of split housings and the cover of one-piece housings can usually be taken off to expose the
bearing. After removing the used grease, fresh grease should
first be packed between the
rolling elements.
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Where more frequent relubrication is required provision should be made for
regreasing; preferably a grease nipple should be fitted to the housing.
A grease gun
(lubricator) can then be used. To help ensure that fresh grease actually reaches the bearing
and replaces the old grease, the lubrication duct in the housing should either feed the grease
adjacent to the outer ring side face, or, better still,
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into the bearing, e.g. spherical roller
bearings with lubrication groove and holes in the outer ring, figures 1 and 2. After a number
of such relubrications the housing should be opened and the used grease removed before fresh
grease is added. |
| Scale a:
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Radial ball bearings
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| Scale b:
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Cylindrical roller bearings, needle roller bearings
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| Scale c:
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Sperical roller bearings, taper roller bearings, thrust
ball bearings;
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full complement cylindrical roller bearings (0,2 tf);
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crossed cylindrical roller bearings with cage (0,3 tf);
cylindrical roller thrust bearings,
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needle roller thrust bearings, spherical roller
thrust bearings (0,5 tf)
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DialSet re-lubrication calculation program
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DialSet is a calculation program which easily determines the right time
setting for your SYSTEM 24 and SYSTEM MultiPoint applications. In addition
it recommends when to use LAGD 125 and when to use the LAGD 60.
Available on CD-ROM in six languages.
Click here to
download DialSet
Designation: MP3506
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| © SKF Maintenance Products Date of issue: 2002-05-01 |
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