As oil breaks down, as it eventually does, many issues can crop up, one of which is gelation.
Gelation means that the oil has stopped being fluid and has become resistant to flow. Obviously, this is a major problem, leading as it does to poor lubrication and possible equipment failure. By getting to know more about gelation, you can do more to prevent it and ensure that your machinery runs more efficiently for longer periods of time.
What are the signs of gelation?
ASTM International says that oil gelation is categorized by:
“A rheological condition of an oil characterized by a marked increase in the flow resistance over and above the normal exponential increase of viscosity with decreasing temperature, particularly at lower shear stresses and temperatures.”
It is possible to use the ASTM D5133 test to analyse the likelihood of oil gelation. In this test, oil is heated up and slowly cooled at the same time, so that its viscosity can be measured at varying temperatures.
The results of this test are a gelation index, which can be put into chart form, and which can be used to determine at what temperature oil will quickly thicken. This is known as its gelation index temperature.
This information is useful for determining how likely it is that oil gelation will occur in any environment, allowing you to manage oil supplies and storage more carefully.
It is usually the case that the highest acceptable level of oil gelation on the gelation index is 12 with an upper viscosity limit of 40,000 centipoise. If oil gelation gets any higher than this, there is a real risk that it will no longer be able to be pumped, or that it will not flow around a machine, thus causing problems such as overheating.
Another problem that can occur is air binding. This is a condition in which an air void is present in the oil sump. As the oil is too thick to fill the void, it can lead to extreme wear and tear and equipment failure.
As you can see, the most important step you can take to avoid oil gelation problems in oils, whether from Shell, Q8 or another top brand, is to have the gelation temperature of your oil tested. By doing this, you will be better able to manage your equipment, and take steps to save your oil when there is a need to do so.