Switching to application-specific greases with advanced formulations can bring about performance benefits – and manufacturing operations of all sizes are beginning to realise these gains. However, changing over to a new product is never as straightforward as you think; improper implementation risks triggering unscheduled downtime and costly maintenance! Read on to find out how to avoid the potential pitfalls of switching grease in industrial operations.
Switching to application-specific greases with advanced formulations can bring about performance benefits – and manufacturing operations of all sizes are beginning to realise these gains.
However, changing over to a new product is never as straightforward as you think. If you don’t properly implement the change, you risk triggering unscheduled downtime and costly maintenance!
For oils, it is often feasible to completely drain them out due to their fluidic nature. But for grease applications, it is much harder to remove all of the old product before applying its replacement. This risks triggering compatibility problems even when greases feature similar formulations.
The growing complexity of grease thickeners and function-enhancing additives has helped the formulation of products with clear operational benefits, but these advances can cause problems when greases are co-mingled.
Incompatible additives and thickeners risk triggering a performance reduction so severe that it causes damage to components through ineffective lubrication. Therefore switching greases needs to be carefully managed in order to minimise compatibility issues.
Incompatibility indicators – what to look out for
There are a number of incompatibility indicators, the most frequent being a change in the consistency of the grease mixture relative to that of the individual pure greases. This will become more pronounced as the operating temperature or the rate of shearing of the grease mix increases.
Incompatible greases may also exhibit abnormal oil separation at higher temperatures. This could lead to grease or base oil leakage, premature ageing or inappropriate oil bleed in the contact zones.
How you test for incompatibility
Compatibility cannot be predicted with certainty from knowledge of the composition of the greases. Before a change in grease occurs, it is essential to test a blend of the two products.
A common test protocol is to evaluate the stability of a mixture by comparing its properties and performance against those of the neat greases comprising the blend. The principle of the test is to shear the co-mingled greases at various ratios under controlled and identical conditions – to discover any change in structural stability compared with the performance of the ‘pure’ grease products.
The general compatibility between two greases can be established through three primary performance measurements: dropping point, consistency and mechanical stability. The overall assessment of the test results determines if the greases are:
Generic grease compatibility chart*
*This matrix is based on information commonly used in industry. It provides a general assessment of grease compatibility based upon the structural stability of mixtures of different grease thickeners. It does not address potential additive related incompatibilities or other performance features. Classification may differ for specific greases depending on composition and manufacturing process. It is always recommended to thoroughly remove and clean out any old grease remaining in application prior to converting to a different grease. Information in this table does not engage the responsibility of ExxonMobil or its affiliated companies.
In order to ensure the best possible performance, we advise you to work with an experienced grease supplier with the most appropriate products for their specific application (check out www.mobil.com/Industrial to find out more).
Importantly, when you are systematic and careful in choosing your greases, you can optimise machinery operation and avoid significant costs due to premature equipment failure.
What are some of the issues you’ve faced when switching greases? What was the best way to change them for you? Happy to hear your views in the comments below, or hit ‘Like’ on the toolbar to the right if you found this Tip of the Week useful!
Cuando nos tocaba cambiar una grasa,teníamos la duda sobre como cambiarla,si se tenia que limpiar la maquina,sin dejar rastro de la otra,no equivocarnos en la cantidad de aplicación a los cojinetes.