Page 114 - Rollingbearings

B.4 Lubrication
Relubrication intervals Determining grease where
quantity for initial ill V = free volume in the bearing [cm 3 ]
Use diagram 2 to estimate the relubrication (for standard grease, mass in grams multi-
intervals t . The diagram is valid for bearings and relubrication plied by 0,9; for luorinated grease, mass
f
with a rotating inner ring on horizontal in grams multiplied by approximately 2)
shafts under normal and clean operating Commonly, the free volume in bearings is B = bearing width [mm]
conditions, using: completely illed during installation and the D = outside diameter [mm]
free volume in SKF plummer block housings d = bore diameter [mm]
• the nd factor multiplied by the relevant is partly illed SKF recommends that the free M = bearing mass [kg]
m
bearing factor b where volume on each side of the bearing in a
f
– n = rotational speed [r/min] customer-designed housing is equal to the
– d = bearing mean diameter [mm] free volume of the bearing For bearings
m
= 0,5 (d + D) with a metallic cage, the free volume in the
– b = bearing factor dependent on bearing bearing is approximately
f
type and load conditions (table 1) π 2 2 -3 M
V = —– B (D – d ) × 10 – –––––––––
• the load ratio C/P 4 7,8 × 10
-3
The relubrication interval t is the estimated
f
number of operating hours that a good quality
lithium soap grease with a mineral base oil
can perform adequately when the operating Diagram 2
temperature is 70 °C (160 °F) High perfor- Relubrication intervals at operating temperatures of 70 °C (160 °F)
mance greases can extend relubrication
intervals and grease life t [operating hours]
f
The relubrication intervals given in 50 000
diagram 2 must be adjusted according to
table 2, page 115
When the speed factor nd exceeds 70%
m
of the recommended limits (table 1), check
the inluence of the selected lubricant on the
operating temperature and speed
In practice, relubrication intervals above
Lubrication 30 000 h are not reliable, because intervals 10 000
of that length exceed the predictable perfor-
mance life (because of lubricant ageing) of

B.4 most greases 5 000
Adjustments for
relubrication intervals

Various adjustments for relubrication intervals
are described in table 2 under various
operating conditions You may also calculate
lubrication intervals using the SKF Bearing 1 000
Calculator (skf com/bearingcalculator)

500
C/P ≥ 15

C/P ≈ 8

C/P ≈ 4
100
0 200 000 400 000 600 000 800 000
nd b [mm/min]
m f

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