The major function of any type of grease is to remain in contact with and lubricate moving parts. The grease should happen without any forms of leakage due to various factors such as gravity, centrifugal forces, or being squeezed out under pressure. The most important practical requirement of grease is to retain its properties regardless of any pressure or temperature change.
It should be noted that grease and oil cannot be used interchangeably due to various reasons. Generally, grease is used as a lubricant in scenarios where oil is not practicable or convenient to be used due to factors such as temperature variations, the significant role of gravity, and centrifugal forces. Generally, grease is used for:
Equipment/machinery that is run periodically or has been stored for a long period. This is because grease hold in place forming a lubricating film.
Machines that are not frequently lubricated due to inaccessibility. High-quality greases have the capability of maintaining their properties for extended periods. One such application is “sealed-for-life” use in types of equipment such as gearboxes and electric motors.
Equipment operating under extreme conditions like high pressures and temperatures, shock or slow speed under substantial load.
Worn out parts. Unlike oil, grease maintains thicker films in clearances broadened by wear and can extend the life of such parts.
Grease can be used as a sealant to reduce leakage and keep the area contaminant free. Due to its thick consistency, grease acts as a very good sealant thus preventing lubricant leakage and entry of foreign contaminants and corrosive materials. In addition, grease also keeps deteriorated seals effective.
Unlike oil, grease is easier to contain. Expensive systems of circulating equipment and complex retention devices are required for oil lubrication which is not the case for greases. Due to its rigidity and consistency, greases are easily retained with simple and less costly retention devices.
Grease can retain solid lubricants in suspensions. Fine solid lubricants such as graphite and molybdenum disulphide (moly) are mixed with grease to boost the properties of grease such as extreme pressure applications and high-temperature stability.
With grease, the fluid levels do not have to be controlled or monitored.
About the Author:
Rajan Hirani is ILD/Sinopec’s Technical Support Officer. He is responsible for the chemical analysis of lubricants, delivering subsequent recommendations on the most effective lubricants and application technologies to customers. Rajan is a PhD Research Scholar in Chemical Engineering. He holds a Bachelors degree in Chemical Engineering (First Class Honours) and an Advanced Diploma in Science and Engineering.