NTN - Large Bearings

Lubrication
Table 6.9 Factor K
Expelled oil temp minus
supplied oil temp ˚C
K
10 1.5
15 1
20 0.75
25 0.6
Furthermore, if it is assumed for calculation purposes
that no heat is radiated by the housing, and that all
bearing heat is removed by the oil, then the value in Fig.
6.3 for shaft diameter, d 0, regardless of actual shaft
diameter.
(Example) For tapered roller bearing 30220U
mounted on a flywheel shaft with a radial load of 9.5
kN (969 kgf), operating at 1,800 min -1 , what is the
amount of lubricating oil required to keep the bearing
temperature rise below 15˚C.
d 100 mm
dn 1001,8001810 4
From Fig. 6.4 q 180cm 3 min
Assume the bearing temperature is approximately
equal to the expelled oil temperature,
from Table 6.9, since K 1
Q1180180cm 3 / min
6.5.3 Relubrication intervals
The intervals at which lubricating oil should be changed
varies depending upon operating conditions, oil quantity,
and type of oil used. In general, for oil bath lubrication
where the operating temperature is 50˚C or less, oil
should be replaced once a year. When the operating
temperature is between 80˚C – 100˚C, oil should be
replaced at least every three months. For important
equipment, it is advisable that lubricating efficiency and
oil purity deterioration be checked regularly to determine
when oil replacement is necessary.
Bearing type
Self-aligning roller bearings
Tapered roller bearings
Angular contact ball bearings
Deep groove ball bearings,
Cylindrical roller bearings
3
4
5
6
8
10
15
20
30
40
dn10 4
2
1
Load P
kN kgf
300
200
30,000
20,000
100 10,000
70 7,000
60 6,000
40 4,000
30 3,000
20 2,000
15 1,500
10 1,000
8 800
6 600
4 400
2 200
Shaft
diameter
d
mm
40
0
160
140
100
80
60
20
Oil quantity q
cm 3 /min
100
200
300
400
500
600
700
800
900
1,000
1,100
1,200
Fig. 6.4 Oil quantity guidelines
A-44