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Three Important Things You Must Know About Hydraulic Fluids

1.Viscosity

Viscosity is the most important property to consider when selecting hydraulic fluids for a specific application. Viscosity is a measure of the strength of the oil's adhesion. It determines the friction and resistance of the moving part on the oil. It is this resistance that pushes the flow of hydraulic oil between the metal surfaces. The viscosity of the oil at the operating temperature of the equipment determines the friction of the bearing, the speed at which the hydraulic oil flows through the bearing, and the bearing capacity of the bearing.

Hydraulic fluids of the correct viscosity can be quickly distributed to the surface of moving parts one of the key factors in extending pump life. Actual use of viscosity below the recommended viscosity may result in internal leakage of the pump and consequent increase in oil temperature. Conversely, when the actual viscosity is higher than the recommended viscosity, the hydraulic oil flows slowly, and the internal friction of the fluid increases, which is not well distributed throughout the hydraulic system. Therefore, you need to strictly follow the original equipment manufacturer's recommendations.

2. Base oil used in hydraulic oil

Conventional hydraulic fluids are blended with solvent-neutral mineral oils (ie, Group I base oils). However, the current trend is more inclined to use hydrotreated base oils (ie, Group II base oils). The increase in the type of base oil used means that the cost of hydraulic oil is correspondingly higher. But hydraulic fluids that are blended with a higher level of base oil can provide longer protection for your equipment. Because of its lower volatility, it has stronger antioxidant capacity and demulsification ability. In addition, higher grade base oils mean less oil and more saturated hydrocarbons, both of which help protect your equipment.

3. Hydraulic oil compounding agent

Factors affecting the choice of additives include: performance, compatibility, economics, etc. of the additives.

As hydraulic systems become more and more miniaturized, the residence time of hydraulic oil in the fuel tank is also shorter and shorter. This means that the air needs to be released in a shorter period of time (air pollution can affect the control accuracy), control foam and cooling in a shorter period of time (so the device tends to operate at higher temperatures). In a shrinking hydraulic system, the additives in the hydraulic oil must play a greater role. Because they must cope with pollutants (such as dust and metal particles) in a shorter period of time. Shorter residence times in the tank also mean shorter demulsification times, and the presence of condensation or leakage, the inevitable presence of moisture in the hydraulic fluid. The moisture in the hydraulic fluid can clog the filter, causing corrosion and pump wear, which can affect the performance of the hydraulic fluid.


In summary, the use of the right hydraulic oil additive is essential. For example, demulsifiers can promote oil-water separation, allowing moisture to drain out of the system more easily. Corrosion inhibitors and anti-wear agents protect the surface of working parts from harmful contaminants.


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