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Choosing The Right Hydraulic Fluid

hydraulic fluid

Choosing the right hydraulic fluid


For every hydraulic system, there are a huge variety of options available when it comes to your choice of hydraulic fluid. It is important to not that, while many fluids will accompany the system just fine, they may not be optimum for the purpose. With hydraulics, the two most important aspects for consideration are the viscosity grade and the hydraulic oil type of the hydraulic fluid.


Hydraulic fluid has a lot of different roles within the hydraulic system – it acts as both a heat and power transfer medium, as well as lubrication for the different components. Hydraulic fluids can either come in synthetic forms to withstand wider ranges of temperature, or water-based fluids for use when there is a potential risk of fire. The synthetic versions of hydraulic fluids are perfect for systems that experience higher pressures, temperatures and generally more extreme conditions. The water-based fluids are generally less expensive that synthetic hydraulic fluids, however, they are more expensive than petroleum – they offer very good protection against any fire hazards, however, this means that their other modes of protection are slightly weaker than that of the synthetic fluids.


Does having the right fluid matter?

Choosing a hydraulic fluid that offers the optimum rate of performance also depends on the type of pump which powers the system. There are three different types; vane, piston and gear. If your system features vane pumps, then maintaining a steady flow will require a viscosity range of 15 to 160 cSt. For piston pumps, the range is similar but slightly higher – 15 to 160 cSt. Piston pumps are also perfect for systems which operate at a higher pressure – they can produce pressures of up to 6000 psi. Gear pumps can be divided into internal and external gear pumps, the former of which can function with up to 2200 cSt. External gear pumps can operate a system with a hydraulic fluid of up to 300cSt. Despite the external gear pumps lower viscosity capabilities, they can produce pressures of between 3000 and 3500 psi – second only to the piston pumps for higher pressure systems.


Choosing the right hydraulic fluid depends on a few different factors – the viscosity of said fluid and the conditions of the system being the two most important. It is vital to keep in mind that, even though a system may run just fine with a particular hydraulic fluid, it may not be the optimum fluid for your system – it’s always worth a check.

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