Many factors must be considered when selecting a lubricant for an application. High in priority is the likely operating temperature of the component; some applications operate cyclically between a maximum and minimum temperature, others are more consistent and operate at a fairly steady nominal temperature.
In all cases, the nominal, maximum and minimum temperature of operation must be considered in order to determine the most appropriate lubricant.
Simplistically both oils and greases evaporate or degrade at elevated temperatures, some types more than others. Synthetics are generally more thermally stable and resistant to extremes of temperature, however, for all lubricants a good rule of thumb is that for every 10-15°C rise in temperature, you typically half the life of the lubricant.
Another factor to consider is the viscosity and also the Viscosity Index (VI) of the lubricant. The Viscosity is basically how ‘thick’ the fluid is at a set temperature (usually 40°C) and is measured in Centistokes (cSt). The Viscosity Index is a measure of how the viscosity changes with temperature. Fluids become thicker at lower temperatures and thinner at higher temperatures, the ideal lubricant offers a more stable viscosity throughout a wide temperature range, a high VI.
The key to choosing a lubricant with the correct viscosity is knowing the operating temperature and the viscosity can then be chosen to give an adequate lubricant film at that temperature.
Mineral oils are less resistant to degradation than synthetic oils, however, additives can also be used to enhance the VI and resistance to oxidation.
When we consider grease lubrication the base oil properties must still be considered but we must also be careful when selecting the ideal thickener and additives. Some soaps are more thermally stable than others, some will melt at relatively low temperatures rendering the product useless, some are not compatible with certain materials and some are more resistant to water washout, there are many factors to consider.
What is High Temperature?
Obviously what we consider as a high temperature is relative and varies from industry to industry, application to application, however, a simple guide is as follows:
The typical operating temperature range of various synthetic oils are shown on an attached PDF download (see download tab above). Greases can be formed from these base oils to give similar operating temperatures.
Usually, the larger the operating temperature requirement, the more costly the product, however, it is the cost effectiveness that we must consider. Using the correct lubricant for the application can save on re-lubrication costs, reduce machinery down-time, extend product life and reduce wear and failures leading to increased productivity and savings.
IKV Lubricants are specialists in high temperature lubricants, oils greases and dry film coatings. Please contact us for details of the most suitable product to meet your application requirements.
Temperature deviation data