Machines use multiple rolling bearings, and 90% of them are lubricated with grease. Lubricating the bearings reduces power losses and improves the overall efficiency of mechanical systems. Grease is used to reduce the friction and wear between the moving parts
Grease is made up of a base oil, thickener, and additives. The base oil is used for lubrication and thickeners for maintaining the viscosity and additives to enhance the performance. The elasticity prevents the grease from leaking, and the fluidity helps lubricate the bearing. Conventional greases are not designed to withstand high temperatures.
At high temperatures, conventional greases oxidise and lose their consistency. They break and become ineffective. Specialised grease must be used for high temperatures. High-temperature greases are designed to work at high temperatures and can be used in kilns, dryers, ovens, wheel bearings and other applications that require high temperatures.
High-temperature grease can work effectively at elevated temperatures and increase machine lifespans. It does not break down at high temperatures (above 150° C and sometimes above 200° C) and can guard against rust and corrosion. It is resistant to thermal degradation and does not lose its lubricating properties when exposed to high temperatures.
It can maintain the required viscosity at high temperatures without becoming too thin or running. It is resistant to oxidation and chemical breakdown when used in high-temperature applications.
Many high-temperature greases are water-resistant which prevents washout in wet conditions.
It can maintain consistency, adhesion and lubricating properties in extreme conditions. Selecting the right high-temperature grease for bearings operating at high temperatures ensures the longevity and reliability of the machines. You should consider the specific temperature range and operational environment while selecting a high-temperature grease. Some high-temperature greases are lithium-based grease, Molybdenum disulfide grease and silicone-based grease.
Lubrication using grease
While lubricating bearings if you do not leave empathy space and pack the bearing housing fully with grease and operate it then it can lead to failure. After a few minutes of operating the bearing the temperature inside the bearing will start to rise and the machine will continue to operate until the grease property is lost. This will lead to the bearing failing prematurely.
The main reason for using a lubricant inside the bearing is to form a thin oil film between the moving surfaces to avoid any metal-to-metal contact. The rolling elements inside the bearing are separated by a spacer which provides space to fill in the grease.
If you pack the space fully and leave no empty space then the rolling speed will become 4 – 5 times higher which will lead to the grease ‘Churning’ which increases the temperature. The bearing will have to push through the access grease as they rotate which will lead to the degradation of grease and overheating.
Around 30-40% of grease volume is enough to lubricate the bearing and it will last till the relubrication interval. The bearings need optimal grease to work efficiently and not more or less. Using more grease can increase the temperature and using less grease can reduce the life of the bearing.
Selecting high-temperature grease
- You should ensure that the grease will be able to withstand the maximum temperatures that your machine will reach.
- Choose grease with synthetic oil as such greases are thermally stable and perform better at high temperatures.
- Greases are available in different grades and you should choose a grease with the right consistency depending on your application.
- Choose grease with additives which can enhance the performance like extreme pressure additives, anti-wear additives and oxidation inhibitors.
- If your machine operates in wet or humid conditions then you should select grease that provides water resistance.
- You should ensure that the grease you use is compatible with the seals and other lubricants you may be using. This will help to avoid any chemical reaction, overheating and breakdowns.
- You should try to use eco-friendly greases to reduce the environmental impact.
High-temperature greases use high-quality mineral oil, specialised thickeners and additives. They can perform effectively in a wide temperature range and loads. It can be used to protect against friction and wear between the moving parts. It is formulated to withstand high temperatures where the conventional grease may break down and become ineffective. High-temperature greases can maintain the temperature by dissipating the heat produced.
High-temperature greases use synthetic oil which contains antioxidants to enhance the re-lubrication interval. Its performance can be improved by adding rust and corrosion inhibitors. Complex soaps are used as thickeners to provide lubrication over a wide temperature range. High-temperature grease can be used to operate the machine smoothly.
