What Is Hydraulic Oil?
Hydraulic Oil/Fluid is used in hydraulic systems across an enormous variety of industries and machinery from aviation and agriculture to logistics and engineering. It also has other uses. The properties of hydraulic oil also make it useful as a coolant, a sealant, and a lubricant.
First and foremost though, hydraulic oil is used to transfer power from one end of a hydraulic system to the other. Because hydraulic oil does not compress, this gives hydraulic systems immense power. This is evident in its uses such as in forklift trucks which lift huge loads and the hydraulic braking systems which need to be powerful enough to stop large vehicles such as lorries and tractors.
Hydraulic oil is often mistaken as hydraulic fluid. The difference being that hydraulic fluid has additives from fluids such as water and salt solutions to chemicals that prevent wear and tear or are rust-resistant. Another major difference is the flashpoint – hydraulic oil is highly flammable but hydraulic fluid, which was developed after WWII to improve safety, is not.
International Standards Organization Viscosity Grade (ISO VG)
ISO VG Background
Viscosity is just about the most important property of lubricants including hydraulic oils/fluids. However, until 1975 there was no definitive or common measure of viscosity in hydraulic fluids for manufacturers or users. This created a lot of confusion and meant it was difficult to ensure people were using the right fluids for the right jobs.
So, societies across the globe, including the American Society for Testing and Material and The British Standards Institute, got together and created the ISO VG or International Standards Organisations Viscosity grade as a universal measure.
Hydraulic Oil ISO VG Grades
The following is a rough guide to ISO VG grades and their typical uses.
- ISO VG 100 Hydraulic Fluid is most often used for the type of industrial machinery which bears heavy loads.
- ISO VG 68 Hydraulic Fluid is designed for use in systems that bear heavier than usual loads.
- ISO VG 15 Hydraulic Fluid is mainly used in power steering and hydraulic brake systems.
- ISO VG 22 Hydraulic Fluid is generally used for pressurised airlines for hydraulic powered tools.
- ISO VG 32 Hydraulic Fluid is for higher-powered hydraulic tools.
- ISO VG 46 Hydraulic Fluid is suitable for the kinds of high-pressure hydraulic systems in industrial settings.
ISO VG Considerations & The Importance Of ISO VG
Hydraulic oil, like other oils, is affected by changes in temperature. Specifically, its viscosity (or fluidity/thickness) changes according to the ambient temperature. The higher the temperature, the lower the viscosity – think of butter melting or oil heating in a pan – it becomes more mobile, more fluid.
When the temperature is lower, again think of butter or oil, but this time – when it is in the fridge. Cooler oils become less fluid and have a higher viscosity.
Depending on its uses, hydraulic oil may be subjected to intense variations in temperature. This can lead to oil deterioration and leaks if it is too hot. Or, it can freeze under colder conditions. Either can seriously damage a hydraulic system.
To prevent these problems additives are used which stabilise hydraulic oil in extreme temperatures. This is then measured with VI, the viscosity index – the higher the VI, the hotter the temperature it can withstand.
Even with the introduction of the ISO VC grades over 40 years ago, choosing the right hydraulic oil can still be a cause for confusion at times. Furthermore, even when the right hydraulic fluid is being used, it is still important to get your hydraulic system checked regularly including condition monitoring and oil analysis to ensure you are getting the best out of your hydraulic oil before changing it.
For these services, as well as all your other hydraulic system needs and purchases, get in touch with us at MCH Hydraulics.