Bearing Greasing is the most common form of
lubrication as it is simple and easy to use.
When
operation conditions such as speed, temperature and cleanliness
are within the limits indicated by the grease lubricant vendor,
bearings require no special maintenance, nor subsequent topping
up. This can therefore be call long-life lubrication.
Bearing Grease type selection is critical
for safe bearing operation, depending on:
- operating temperature
- life
- protection
- noise level
A wide range of quality synthetic grease
lubricants is available commercially. Products satisfying
the standards listed in the table below are frequently used.
Speed, load and operating temperature are
basic parameters for grease selection.
Bearings operating at high temperatures,
such as in electrospindles, must be lubricated with long life
grease with a base oil of adequate viscosity and high wear
resistance.
APPLICATION |
GREASE |
Speed (ndm)
Load |
Viscosity
NLGI Consistency
Thickener |
|
Up to 600,000
Light/Medium |
3,000
2
Lithium |
|
Up to 600,000
High |
4,000
2 Calcium/Lithium |
|
Up to 900,000
Medium |
3,000/4,000 2 Calcium/Barium/Lithium |
|
Up to 900,000
Light |
3,500/4,500 2 Calcium/Barium/Lithium |
Grease
Life
The effectiveness of a grease reduces in
time due to operating conditions such as temperature, dynamic
stress and contamination and to its chemical
and physical characteristics.
These parameters are hard to estimate, so
grease life hours ÒLgÓ are calculated prevalently on statistical
data.
Figure 2 gives the necessary elements for
assessing the life of quality synthetic greases in optimum
operating conditions. The upper part of the curve refers to
operation in moderate temperature conditions, such as belt
driven spindles; the lower part refers to applications where
the presence of another heat source, such as an electric motor,
increases bearing temperature markedly, with negative effects
on the lubricant.
Running In
Grease lubricated bearing require an initial
running-in period to ensure the correct lubricant distribution
and to avoid bearing overheating at the starting operation.
The most common form of running-in entails
gradually reaching maximum speed and achieving stable temperatures
at each step. Another procedure is an intensive sequence of
run and stop cycles according to a pre-set program.
The latter reduces running-in time but requires constant
observation and is only recommended for automated running-in
equipment. This is not advisable for bearings which have to
operate at a particularly high speed.
Grease Quantities
The amount of grease to introduced into the
bearing depends on operation speed. The amount is calculated
by multiplying factor K (function of maximum rotation speed,
expressed ndm Ð Figure 3) by the Òreference quantityÓ showing
in the diagram (bore and bearing series function; Figure 4)
In the case of small bearings where the grease
quantities are very small it is advised that before greasing
the bearings are immersed in a grease solution (containing
3-5% grease) then removed and allowed to drain (and the solvent
to evaporate) before applying the grease. This ensures that
all the bearing surfaces are covered with a thin layer of
the lubricant.
 
Factory Greased Bearings
SNFA bearings are very often supplied with
the type and amount of grease as specified by the customer.
This solution offers operating and economic advantages for
the user, as the bearing is greased during the manufacturing
route with greater control over cleanliness, quantity and
distribution.
|
GRW
Product Desc.