SKF - Rolling Bearings

Selecting bearing size using the life equations
For other degrees of contamination or in the
most general case of circulating oil, oil bath
and grease lubrication, the contamination factor
for a bearing arrangement can be determined
using the simplified equation
t q c 2 w y
h c = min (c 1 k 0,68 d 0,55 m , 1) 1 – ———
v < 3 P JL z b
d m
B
min (#1, #2) = use the smallest of the two
values
where c 1 and c 2 are constants characterizing
the cleanliness of the oil in accordance with
ISO 4406, or of the grease according to the
classifications in table 6. Note that in case of
oil filtration, the corresponding level of filtration
efficiency (in accordance with ISO 16689)
(† table 7) can also be applied in place of the
metrological characterization of the status of
cleanliness of the oil.
Table 7
Factors to determine contamination levels for an oil lubricated application in accordance with ISO 281
Filtration ratio ISO 4406 Circulating oil lubrication with
in-line filters
Oil lubrication without filtration
or with off-line filters
b x(c) Basic code c 1 c 2 c 1 c 2
b 6(c) = 200 –/13/10 0,0864 0,5663 0,0864 0,5796
b 12(c) = 200 –/15/12 0,0432 0,9987 0,0288 1,141
b 25(c) = 75 –/17/14 0,0288 1,6329 0,0133 1,67
b 40(c) = 75 –/19/16 0,0216 2,3362 0,00864 2,5164
– –/21/18 – – 0,00411 3,8974
77