There primary considerations when selecting the right hydraulic oil are the viscosity and hydraulic oil type requirements. These are determined by factors such as the type of pump in the hydraulic system, the operating temperature and the operating pressure of the system.
The following shows one basic way of selecting the right type of hydraulic oil for a hydraulic system.
- Determine the type of pump
- Select the type of hydraulic fluid
- Consider the application
Vane pumps require a viscosity range of 14 to 160 centistokes (cSt) at operating temperatures. Piston pumps can generate a higher operating pressures and need oil with a viscosity of 10 to 160 cSt. Internal gear pumps may use oil with a viscosity of up to 2,200 cSt, while external gear pumps cap out at 300 cSt viscosity.
Full synthetic oils are ideal for high and low operating temperatures and when high operating pressures are needed. Petroleum fluid is the most common hydraulic fluid and often comes formulated with performance-enhancing additives. Water based is the least common and is ideally used when there is a higher probability of fire.
Knowing the type of application the hydraulic system is being used for helps determine the oil's viscosity and additives. Certain applications will require a higher quality oil.