Page 117 - Rollingbearings

Selecting grease or oil
Table 2
Relubrication interval adjustments

Operating condition Description Recommended adjustment of t f Reason for adjustment
/ bearing type

Operating For every 15 °C (27 °F) above 70 °C Halve the interval To account for the accelerated
temperature (160 °F) up to the high temperature ageing of grease at higher
limit (HTL) temperatures
For 15 °C (27 °F) under 70 °C Double the interval To account for the reduced risk
(160 °F) (maximum once) 1) of ageing of grease at lower
temperatures

Shaft orientation Bearings mounted on a vertical shaft Halve the interval The grease tends to leak out
due to gravity
Vibration High vibration or acceleration levels Reduce the interval Interval reduced depending on
machine speciic instructions
(e.g. vibrating screen)
Outer ring rotation Outer ring rotation or eccentric shaft Calculate the speed as nD rather than nd m The grease has a shorter
weight grease life under these
conditions

Contamination Contamination or presence of luid Adjust depending on the contamination level: To reduce the damaging effects
contaminants caused by contaminants
Low
Relubrication intervals are given by grease life. It
is assumed that there will be no or slight ingress
of contamination entering the bearing.
Medium
Some contaminants may enter the bearing. Some
additional relubrication is required to remove
contaminants.
High
There is a clear risk that contaminants will enter
the bearing. Relubrication is required to remove
aged grease and to remove contaminants.
Severe
Relubrication is primarily needed to lush the Lubrication
bearing and remove contaminants.

Bearing size Bearings with a bore diameter Reduce the interval by a factor 0,5 initially. If These are typically critical
d > 300 mm grease samples taken before relubrication are arrangements, which require B.4
found to be satisfactory, the relubrication interval strict, frequent relubrication
can be increased gradually. programmes
Cylindrical roller Bearings itted with J, JA, JB, MA, MB, Halve the interval These cage designs require
bearings ML, MP and PHA cages 2) higher oil bleeding from the
grease

1) For full complement and thrust bearings, do not extend the interval
2) For P, PH, M and MR cages, there is no need for adjustment.

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