Exploring Compatibility Limits for Lubricating Greases Formulations.

Grease compatibility is thought to be an important consideration for both grease manufacturers and end-users. When switching from one grease to another, the supplier is typically asked if the two greases are compatible. Two incompatible greases could be detrimental to the equipment and even cause failure in extreme cases. However, provided due care is taken, switching from one grease to another is quite possible. Grease incompatibility is a multicomplex issue that can occur due to interactions between the thickeners, the base oils or the additives. Almost 70% of the global grease demand is based on lithium thickener chemistry. Due to the increasing debate on the gradual decrease on lithium greases reliance, the interchangeability between other types of thickeners is becoming more and more relevant. The aim of this study is to investigate the compatibility of various commercially available grease formulations that could replace lithium-based greases – namely aluminum complex, polyurea and calcium sulfonate complex – against conventional lithium complex. The ASTM compatibility methodology was utilized as a baseline, by analyzing three different mixing ratios for each combination, yet it was extended to include other protocol to report the various interactions of the different blend components. The results indicated that for the examined grease products the lithium complex-polyurea combination were the most efficient, while the lithium complex-calcium sulfonate complex blends were the least compatible. Proper management of grease compatibility ultimately contributes to improved operational efficiency and reduced maintenance costs.