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The
perfect solution for every application
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Courtesy of SKF Maintenance Products
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Even the very best bearing can only show optimum performance
when it is lubricated correctly. Here, it is extremely important to choose
the right bearing grease and to apply the most suitable lubrication intervals
and methods. This realization has prompted SKF, the world's leading
manufacturer of rolling bearings, to look intensively into the subject of
lubrication. SKF engineers consider grease to be a "fundamental"
component of the bearing arrangement and thus, as important as the bearing,
housing and sealing. SKF's vast experience in the development of rolling
bearings forms the basis for the development of a special range of
lubricants, the superior quality of which is obtained through continuous
testing and studies.
The strict standards and testing parameters developed and
applied at the SKF Engineering and Research Center have become
internationally recognized benchmarks for bearing greases. The comprehensive
range of SKF bearing greases is the result of many decades of research and development.
Each individual lubricant is precisely adjusted to the respective field of
application.
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SKF sets the standard
Tangible performance parameters mean more to SKF than the
chemical composition of the lubricant. The chemical composition is not the
only factor in determining the quality of a particular grease, since modern
lubricants are extremely complex. SKF has set the standards for developing
special testing parameters.
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Bearing grease selection
Incorrect lubrication accounts for up to 36 % of premature
bearing failures. All–purpose greases are inadequate for specialized bearing
needs and can cause problems rather than be beneficial. Bearing applications
have wide variations of operating conditions and correct lubrication calls
for matching the grease precisely to the application.
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Bearing greases help ensure smooth, trouble–free operation and
maximum reliability even under the most extreme conditions. They help prevent
contamination from penetrating the bearing, cushion any shock loads and
protect against corrosion. Selecting the right bearing grease for a certain
application is essential for achieving the maximum service life of a bearing.
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Selection criteria for correct lubrication include bearing
type and size, temperatures, speeds and loads, as well as the desired service
life and re–lubrication intervals.
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SKF Traffic light concept and Grease Performance Factor
The temperature range over which a grease can be used depends
largely on the type of base oil and thickener used as well as the additives.
The relevant temperatures are schematically illustrated in the following
diagrams in the form of a “double traffic light”.
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Operating temperature range of greases:
The SKF Traffic Light Concept
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LTL – Low–temperature limit:
The lowest temperature at which the grease will allow the
bearing to be started up without difficulty.
LTPL – Low–temperature performance limit:
Below this limit, the supply of grease to the contact surfaces
of rolling elements and raceways may become insufficient. Values are
different for roller and ball bearings.
HTPL – High–temperature performance limit:
Above this limit the grease will oxidize in an uncontrolled
way, so that grease life cannot be determined accurately.
HTL – High–temperature limit:
When exceeding this limit, the grease loses its structure
permanently (e.g., the dropping point for soap–base greases).
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Effect of temperature on grease functioning
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The values shown in these diagrams are based on extensive
tests conducted in SKF laboratories. These tests allow us to accurately
determine the temperature range of the SKF bearing greases given in the
selection charts included in this catalog.
The results of these tests are also used to evaluate the
grease life. The performance of each grease is then translated into a Grease
Performance Factor (GPF). Greases with highest values offer the longest life.
This factor, used in correlation with the SKF re–lubrication diagram (see SKF
General Catalog GC 5000), allows you to determine the correct
re–lubrication intervals for the chosen grease.
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Re–lubrication intervals
Choosing the right bearing grease for a certain application is
critical to bearing performance. Applying the correct quantity of grease at
the right intervals is of equal importance. Over– or under–greasing as well
as inadequate lubrication methods can shorten the bearing’s service life. For
determining the right amount of grease and the correct re–lubrication
intervals for a specific application, SKF has developed DialSet, a simple
computerized re–lubrication calculation program. Calculated re–lubrication
intervals are based on the latest lubrication theories published in the SKF
General Catalog (GC 5000) and depend on bearing type used, application
conditions and properties of selected bearing grease.
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The lubrication method used is equally important to the right
bearing grease, quantity and lubrication intervals. Using lubricators, manual
or automatic, facilitates proper lubricant supply to the application.
Maintaining cleanliness when lubricating bearings is crucial, as
contamination can cause the bearing to fail prematurely.
Using a grease meter in combination with a grease gun or pump
during manual lubrication helps ensure the supply of the right quantity of
grease. SKF’s range of grease guns, pumps and lubrication accessories is
designed for contamination–free grease supply as well as ease–of–use
Continuous lubrication using automatic lubricators, single or
multiple–point, provides the application with consistent and controlled
supply of bearing grease. This reduces the risk of over– or under–greasing
and positively contributes to optimizing the bearing’s service life.
Additionally, automatic re–lubrication reduces the risk of contamination.
Around the clock solutions offered by SKF, such as SYSTEM 24 and SYSTEM MultiPoint,
provide precise and reliable grease supply, exactly adjusted to the
application’s needs.
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