Experimenting with Grease Thickeners

Two types of thickeners, calcium sulfonate and lithium complex, dominate heavy-duty greases in the pelleting industry. However, with innovative formulations, other thickeners show unforeseen benefits.
By Holger Streetz | October 07, 2020

Two types of thickeners, calcium sulfonate and lithium complex, dominate heavy-duty greases in the pelleting industry. However, with innovative formulations, other thickeners show unforeseen benefits.

Greases are semisolid lubricants that consist of a soap emulsified with a base oil. The purpose of grease lubrication is the high initial viscosity that drops with shear, invoking the effect of oil lubrication. The soap acts as a sponge to keep the oil in place. Different soaps thicken the base oil—mineral, vegetable or synthetic—and add certain characteristics to the resulting grease. Lithium complex greases make up approximately 60% of greases available in North America. The key characteristics are high operating temperatures and very good water resistance and work stability.

Two types of thickeners, calcium sulfonate and lithium complex, dominate heavy-duty greases in the pelleting industry. However, with innovative formulations, other thickeners show unforeseen benefits. Lithium complex greases are often used in automotive lubrication (chassis, wheel bearings) and heavy industrial applications (construction and mining). Calcium sulfonate greases provide extreme pressure and anti-wear properties. Excellent oxidation resistance, mechanical stability and corrosion protection characterize them. Therefore, these greases are often applied in marine and heavy mobile equipment, as well as pulp and paper industry. In addition to these common soaps for heavy industries, aluminum complex and bentonite are gaining attention. Aluminum complex greases have high maximum operating temperatures and good corrosion protection. They are typically used in high-load applications in steel, mining and food processing (H1 food grade). Bentonite, or clay, is H1 food grade thickener and has no dropping point. The grease has a buttery texture and is valuable in high-temperature applications. Polyurea grease is a nonsoap thickened grease with wide acceptance for its long life attributes. Its incompatibility with many other greases, however, sets very high demands for operations and maintenance, as confusion can lead to very expensive machine failure.

Grease Comparison: A Glance Toward Vietnam
In Vietnam, European brand pellet mills are lubricated with calcium sulfonate grease and have an average output of 5 to 6 tons per hour. Asian brand pellet mills use lithium complex or clay-based greases and have an output between 2 and 2.5 tons per hour. A huge difference is the volume of grease, as Asian pellet mill models consume up to five times the amount of European models, while production rates are just 50% of European models. Where European pellet mills consume one drum per mill per month, other manufacturers consume up to five drums per mill per month. The significant difference in volumes has several reasons; quality alone does not account for such a gap. While all manufacturers build robust equipment, operations and feed mix differ significantly. Hardwood puts much more stress on the equipment than softwood. Debarking has a great effect, too. Then, of course, some operators run the equipment above nameplate capacity, putting up with increased wear.

Swiss manufacturer Bathan AG, specialized in ceramic lubricants, manufactures the multipurpose grease KF 7, an aluminum complex grease with modified EP additives. Grease consumption is 95% lower than with regular greases, while lifetime of bearings improve. Many European wood pellet customers have switched to the new formulation without changing the set-up (95% lower grease volumes, with and without automated lubrication systems).  


Author: Holger Streetz
COO, Bathan AG
h.streetz@bathan.ch