Hydraulic systems have smaller clearances than many. As such, it is imperative that these oils be kept clean and free from any debris. Most hydraulic components have a required ISO 4406 rating that should be met to ensure that the oils do not allow foreign particles to enter as these can easily clog the clearances and cause the system to stop working.
Chevron Lubricants produced a document that compiles some ISO 4406 codes for various types of industrial off highway equipment, which also includes the hydraulic standards. It noted the recommended ISO Cleanliness for John Deere hydraulic Excavators can be ≤23/21/16, this can be found here (Chevron Lubricants, 2015).
Hydraulic oils should be pre-filtered before being placed in your equipment even though there are filters on the inside of the equipment by reducing the amount of contamination entering the system from the onset, you can ensure a longer life for your hydraulic oil. Hydraulic oils should also be stored in closed containers not those that are left open to the atmosphere!
Advancements in Hydraulic Oils
According to (Fitzpatrick & Thom, 2021), the hydraulic oil market was approximately worth USD 77.5 billion by the end of 2021. Mobile hydraulics account for 65% of the market while industrial equipment represents 35% of the market. Clearly, the larger market share exists for mobile hydraulics. However, OEMs are also moving towards smaller oil sumps with longer oil drain intervals that can impact on the volume of hydraulics needed periodically.
Changes by OEMs also impact the formulation of hydraulic oils. For instance, if a smaller sump is used then, the hydraulic oil must now be able to cool faster, transport the same (or larger) force and maintain the intended viscosity of operation while being under greater stress. In these cases, the additive packages involving the antiwear, thermal stability, viscosity index improvers, defoamants and dispersants must be formulated to work in unison without compromising the other.
There have been changes in additive technology that allow for larger tolerances for various characteristics but while additives are evolving, the refining of base oils is also trying to keep up. With all of these evolutions, the chemical composition of hydraulic oil today vastly differs from one created in the 1950s. The requirements of hydraulic oil have also greatly evolved, forcing these changes in formulation.
Hydraulic oils today need to provide longer oil drain intervals, better stick/slip characteristics, increased efficiency, improved conductivity and wear performance and an added level of sustainability. Formulators need to create hydraulic oils that can adhere to these characteristics while also not infringing on regulatory requirements. This makes hydraulic oils one of the most powerful types of oils because they must conform to these requirements while also transferring force from one place to another.
References
Chevron Lubricants. (2015, January 24). Chevron Lubricants Latin America. Retrieved from Chevron Lubricants: https://latinamerica.chevronlubricants.com
Fitzpatrick, A., & Thom, M. (2021, November 08). How the Global Hydraulic Fluid Market Is Changing—And What It Means for the Future. Retrieved from Power Transmission Engineering: https://www.powertransmission.com/blogs/1-revolutions/post/189
Mang, T., & Dresel, W. (2007). Lubricants and Lubrication Second Edition. Weinheim: WILEY-VCH.
Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals, Third Edition Revised and Expanded, ExxonMobil. Boca Raton: CRC Press, Taylor & Francis Group.
