In the demanding world of lubrication, there are applications where a viscous lubricant needs to be applied to ensure that moving parts are lubricated sufficiently. In these cases, a grease is the most suitable option to ensure optimum performance.
The composition of a grease is a soap base that is emulsified with mineral/synthetic or vegetable oil. The composition can be categorized as follow:
- Lubricating Oil – 80% to 90%
- Thickener – 8% to 15%
- Additives – 2% to 5%
Composition
Different types of thickeners, referred to as metallic soaps, can be used depending on the application. Factors to take into account when selecting the correct thickener will include temperature, speed, pumpability, and water presence to mention a few.
Complex Soaps have been developed as a way to improve the heat resistance of normal soap type greases. For example, for a high-speed bearing under high load (more heat generation within the bearing), a Lithium Complex Soap will be preferred above a standard Lithium Soap.
The most common types of soaps can be classified as follow:
- Lithium
- Lithium Complex
- Calcium
- Calcium Complex
- Aluminium Complex
- Barium
- Sodium
- Polyurea
- Calcium Sulphonate
- Calcium Sulphonate Complex
- Bentonite Clay
Consistency
The softness or hardness of any grease is known as the consistency, which also happens to be its most readily recognised characteristic. The consistency can range from heavy consistency (Block Form) to a fluid (Cooking Oil). The National Lubricating Grease Institute (NLGI) ranks the value obtained from the penetration test to give the consistency.
Most grease requirements, both Automotive and Industrial, can be satisfied by an NLGI number 2, usually specified in the description e.g., Grease 2 or Grease EP2. Some NLGI 0 or 1 greases are developed for low temperature for central systems with a long-distance greasing line.
Additives
Most additives used in the manufacture of lubricating greases are the same additives used in lubricating oils. These additives can be classified as Oxidation Inhibitors, Corrosion Inhibitors, Extreme Pressure (EP) Additives, and Tackifiers. In addition to this, Fillers or Solid Lubricants can be added to assist with shock loads and vibrations in parts to be lubricated. For instance, Graphite/Molybdenum Disulphate (Moly) is used in greases for pins and bushes where sliding surfaces are directly in contact with each other.
Compatibility
The compatibility is also a very important factor to consider because, there are known cases where incompatible greases are mixed, leading to component failure. Compatibility should never be assumed unless, the replacement is of the same type and grade as the one previously used. Please see the below chart for compatibility of the different grease soaps for reference:
In the vast world of grease lubrication, the correct product, in the correct amount, at the correct time will deliver the best performance and extend the life of the component to minimize downtime and costs.
Here at Chemical Solutions and Innovations, we have a variety of lubricants to suit your needs. Simply reach out to us today and let us advise you what product will best suit your needs.
