Definition: Hydraulic fluid is the energy transfer medium in all hydraulic systems. However, the job of hydraulic fluid goes beyond the simple transmission of power. Although transmitting hydraulic energy is the core purpose of hydraulic fluid, it is useful in four secondary functions - heat transfer, contamination removal, sealing, and lubrication.

Hydraulic machines produce a lot of excess heat during routine operations, often caused by inefficiencies of the components, like pumps and motors. Without a way to carry heat away from these components, it could result in overheating issues with resulting damage of seals and internal components, especially as a result of low local viscosity. As oil returns to the reservoir, it often passes through a cooler to help maintain optimal temperature range before it is pumped back out to the system. Conversely, hydraulic fluid can carry heat into a system during cold starts, when needed.

Hydraulic oil is prepared by the addition of additives in the base stock according to usage, area of usage, ambient condition of usage, the criticality of machines. There can be a variety of base stocks such as mineral oils, synthetic oils, vegetable oils, water-based oils. These base oils can be also further segregated as follows:

1. Mineral Oils: Group I, Group II, Group III. Mineral oils are used in a variety of industries in various forms such as laxative in biomedicines, veterinary, etc as common ingredients in cosmetics, lubricant, and coolant in mechanical & electrical industries.
2. Synthetic Oils: Halogenated compounds, Polyglycols (PAG), Polyether, Poly- alpha-olefin(PAO), Polyether, Silicones, Esters, Phosphate Esters, Polyol & Dibasic acid esters. Synthetic oils can be used as a substitute for petroleum refined oils in extreme temperature operations. One of the major advantages of synthetic oil is its ability to resist chemical decomposition in the presence of water, it also separates from water easily and can operate at higher pressures.
3. Vegetable Oils: Natural vegetable oils such as Canola Oil, Soyabean Oil, Sunflower Oil, Cornflower Oil. Vegetable oils are mainly used in the food industry, they are also used in personal care and cosmetic industries, paint industries. They are also used in electrical industries as insulators due to their non-toxic nature.
4. Water-Based Oils: Water Glycols, Emulsions, Synthetic Solutions. Water-based oils such as water glycols, emulsions have excellent fire-resistant properties. Excellent fire-resistant properties along with good cost and performance make it the right choice for many industrial applications. They also have good operating pressure and temperature ranges.

Thus from the above illustrations, we can identify different types of base stocks and their segregations, and use of these segregations according to the customized needs.

Also read: https://www.linkedin.com/pulse/functions-hydraulic-oil-reasons-its-contamination-anshuman-agrawal/

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