Oil, thickener, and additives are the three major components in grease. They determine how the grease behaves when subjected to different operating conditions. The thickener is somewhat like a sponge that holds the oil and the additives in place.
Most greases manufactured today use high-quality mineral oils as their major fluid component. They are produced with preeminence in quality to provide satisfactory performance in a wide variety of applications. Synthetic oils are known to offer better performance in extreme temperatures (low or high).
A thickener is a substance that gives grease its gel-like structure, which contributes to its texture. The best materials for the thickener depend on the application.
Additives play various roles, they:
- Enhance desirable properties,
- Suppress undesirable properties
- Impart new quality-enhancing properties.
Most common additives are rust inhibitors, anti-wear, friction-reducing agents, extreme pressure additives, polymers and oxidation inhibiting compounds. Additionally, compounds such as moly or graphite may be added to reduce friction during heavy loading on or low speeds.
Functions of Grease
Grease plays a significant role of lubricating moving surfaces and maintaining a thin film on the surfaces without leaking. Quality grease should retain its lubricating properties even in extreme conditions.
Applications that are Suitable for Grease
The use of oil and grease is not generally interchangeable. Grease is used in environments where the use of oil is not practical or convenient. Grease is mostly used for:
- Certain types of applications that are designed to run intermittently or are generally in idle mode for an extended period of time.
- Components, which typically require thicker films of lubricant.
- Applications operating under extreme environments such as slow speeds under heavy loading, shock loads, and extreme temperatures and pressures.
- Components that are not easily accessible for servicing and require lubrication.
Functional Properties of Grease
- Grease stays in place better than oil. Oil lubricated bearings require more complicated seals as compared to grease. Since grease is thicker, it is easier to contain with simplified retention devices.
- Its levels do not need to be monitored as rigorously as an oil lubricated bearing.
- Because of its consistency, grease functions as a sealant to keep out contaminants and minimize leakages.
- Grease hold lubricants such as graphite and molybdenum disulfide (moly) in suspension to help it function effectively under extreme conditions.
Characteristics of quality greases
- Excellent ability to be pumped to the application
- High ability to withstand the effects of water without compromising its effectiveness in lubricating.
- High resistance to deterioration when subjected to extreme temperatures (low or high) or high pressures.
- High heat resistance with the ability to retain consistency even at high temperatures.
- Oxidation stability, which is the ability of a grease to successfully resist a chemical reaction (union) with oxygen. If such a reaction happens, the grease could form an insoluble gum-like deposit that significantly inhibits the functioning of the grease as a lubricant.
- High and low temperature effects. Grease does not possess as good of the heat dissipation ability as oil. Extreme temperature may cause oxidation and subsequently harden the grease. On the other hand, if the temperatures of the grease drop below a certain point, its viscosity will increase making it difficult to flow thus becoming ineffective to lubricate the moving parts.