Page 112 - Rollingbearings

Lubrication

B.4 Lubrication

Selecting grease
Rolling bearings must be adequately lubri-
cated to operate reliably. The lubricant is
required to reduce friction, inhibit wear, pro- or oil
tect the bearing surfaces against corrosion
and may also be needed to provide cooling.
This section describes: The irst step in the lubrication selection pro-
cess is to decide whether to use grease or oil.
• how to select between grease or oil In most cases, grease is the appropriate
• how to select a suitable grease choice for open bearings.
• how to select a suitable oil

For information on lubrication of sealed
bearings, refer to the relevant product Lubrication selection
sections.
low chart and
How lubrication relates to other criteria
Lubrication Lubrication selection and lubricant prop- A low chart to help select the correct lubri-
selection criteria
cation method is shown in diagram 1
erties greatly inluence the operating tem-
The main reasons to choose grease are:
B.4 perature, which in turn inluences: • cost-effectiveness
• whether you should use grease or oil
• simplicity – grease is easily retained in the
• the relubrication interval required for bearing and housing, thus requiring less
grease complicated sealing arrangements com-
• whether oil lubrication is necessary, pared with those for oil lubrication
because circulating oil can be used to
remove heat The main exceptions to choosing grease are
• the lubrication condition – the viscosity in applications where:
ratio, κ, which inluences the bearing size
selection based on SKF rating life • operating conditions require a grease
relubrication interval that is unacceptably
short
• lubricating oil must be used for other pur-
poses (such as in gearboxes)
• heat removal via circulating oil is required
• purging or removing used grease becomes
cumbersome or expensive to handle

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