Bearing Oil lubrication is mandatory when
greasing limits are exceeded.
Several different oil lubrication systems are used, the most
common for machine tool being:
- oil injection
- oil mist
- air-oil
Oil Injection
Oil injection is preferred for bearings having to operate
at very high speed and high load, that is in conditions that
do not allow “oil mist” lubrication because of
the need to cool the bearings.
Oil is injected into the bearings through nozzles placed
so as to lubricate the ball to race contacts with minimum
oil churning. Drainage channels must be provided to prevent
oil from stagnating and churning and hence generating heat.
Besides ensuring proper lubrication, the amount of oil crossing
the bearings also removes the heat generated by bearing operation
and maintains overall temperature at acceptable levels.
The assembly should also include oil filtering, a heat exchanger
to dissipate the heat removed from the bearings and an adequate
oil reserve. A suitable size reservoir facilitates heat dispersion
and the settling out of debris and avoids early lubricant
ageing.
This type of lubrication obviously requires accurate and
proper analysis. Precise rules for calculating oil flow take
account of the bearing type to be lubricated (series and pitch
diameter) and assembly composition. Oil viscosity is an injection
system is according to ISO standards VG10 or VG15.
| Viscosity Grade
ISO |
Kinematic Viscosity at
40¡ deg C |
Kinematic viscosity limits
at 40¡ deg C |
| Minimum |
Maximum |
| VG 2 |
2.2 |
1.98 |
2.42 |
| VG 3 |
3.2 |
2.88 |
3.52 |
| VG 5 |
4.6 |
4.14 |
5.06 |
| VG 7 |
6.8 |
6.12 |
7.48 |
| VG 10 |
10.0 |
9.00 |
11.00 |
| VG 15 |
15.0 |
13.50 |
16.40 |
| VG 22 |
22.0 |
19.80 |
24.20 |
| VG 32 |
32.0 |
28.80 |
35.20 |
| VG 46 |
46.0 |
41.40 |
50.60 |
| VG 68 |
68.0 |
61.20 |
74.80 |
| VG 100 |
100.0 |
90.00 |
110.00 |
| VG 150 |
150.0 |
135.00 |
165.00 |
Required oil quantity for oil jet lubrication
|
Bore (mm)
|
|
50
|
50 120
|
120 280
|
|
|
|
Quantity
of oil (l/h)
|
|
2...24
|
15,,,120
|
60..300
|
|
|
GRW
Product Desc.