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Grease Changeover Precautions

Did you know that every grease is incompatible with at least one other grease?
Some of the most incompatible greases are aluminum complex, calcium complex, clay and
polyurea-thickened greases. The most common effect was substantial softening, however lithium
grease sometimes hardened. It is important to note that even if thickeners are generally
compatible, two greases may contain clashing base oil or additive formulations. Also, not all
thickeners of the same group are compatible with each other.
Polyurea grease is an example of this as two polyurea grease formulations in specific cases
may not be compatible with each other.

Where is it absolutely necessary to change the grease type used, there are some precautions
that should be taken to minimize the risk of potential incompatibility. First, the following
conditions should be met:
1. Verify that the bearing arrangement allows excess lubricant to be purged from the system.
Bearing damage may result in sealed-for-life or shielded bearing arrangements.
2. Verify that the bearing is operating properly before switching products. Improper fits,
clearances, bearing configurations or existing bearing damage cannot be corrected by
changes in lubrication.
3. Verify that the bearing operating condition can accept a full-fill lubrication condition. This
procedure should not be applied to bearings designed to operate with limited grease quantities
because excessive bearing operating temperature may occur.

Grease Changeover Procedures


Assuming all conditions have been met, the following procedure may be used to change out
greases.
1. Use up as much of the old grease as possible before bringing in the new grease.
2. While the bearing is running, slowly pump in the new grease until the excess grease being
purged from the bearing changes in consistency or color. This waste grease should eventually
appear similar to the new product.
3. Repeat the previous step after one to two hours of operation or after the bearing has returned
to normal, steady-state operating condition.
4. Run the bearing for one week (if the previous relubrication frequency was greater than
one week) and relubricate using the normal procedure.
5. Temporarily increase the regrease volume at least during the first two regrease intervals.
The increased grease flow will help move out any remaining old grease and will provide sealing
while overly soft grease may still be in the bearings.
6. Initiate testing (power consumption, amperage draw, relubrication frequency, vibration,
etc.).
Prior to reverting to the original regreasing interval, sample the purged grease, test its consistency
and check for oil separation.