Using the same type of grease for different applications can cause premature bearing failure. Grease must meet the specifications for a particular application. If it’s being added to the bearing for the first time, application specifications are all you have to worry about. However, if you’re changing from one brand of grease to another, you have to pay attention to the compatibility of the thickener for both greases.
If incompatible greases are chosen, the likelihood of bearing failure increases. While both greases may be within application specifications, if they are incompatible with each other, it can negatively affect bearing performance. Initially the mixture may seem to function; but once the bearing experiences regular use, the inferiority can quickly (and disastrously) become apparent. Sometimes it takes a while for the consequent problems to become obvious. If, for example, the bearings and seals are in good shape and the demands aren’t extreme, an incompatible mixture can work adequately for some time.
So let’s say you have no choice; grease has to be changed, how can you choose a compatible grease option? The easiest way is by ensuring that the new and existing greases are compatible. Your new grease vender should be able to advise you whether grease is compatible by running tests if unknown. If for some reason you have to switch to a grease that’s incompatible from what you’ve been using, it’s not completely detrimental. An incompatible mixture can still be mitigated. Before adding the new grease, remove as much of the old grease as possible. If you can’t completely remove all of the grease, make sure you increase the grease consumption temporarily enabling the new mixture to move through the system as quickly as possible.
Following these precautions should help prevent unplanned downtime due to bearing failure. It’s also a best practice to monitor the newly greased bearings after replenishment for potential problems.