Hydraulic Oils: Definition, Types, Uses and Benefits

What is hydraulic oil and where is it used?

What are the other benefits of using adequate high performance hydraulic oils for equipment and hydraulic equipment owners?

Hydraulics represent systems where energy and power are transferred through fluids. The fluids used are called hydraulic fluids or hydraulic oils and they are used in different types of machines, equipment and various industries. In addition, hydraulic systems and components are used in agriculture, construction, mining, steel, shipbuilding, aviation, space industry, chemical industry, medicine, food industry, environmental technology and elsewhere. Name any industry in the world and there is a very good chance that it uses some type of fluid technology in stationary or mobile applications.

There are many advantages to using hydraulics and hydraulic oil. In some cases, a more environmentally friendly alternative is definitely one of the most important. In addition, they are fluids with a high carrying capacity. Thanks to wear, corrosion and other properties, they protect hydraulic systems even in the most demanding environments.

WHAT IS HYDRAULIC OIL?

Hydraulic oil is a fluid that has several functions. It acts as an energy or power transmission medium, a lubricant and a sealant. It is also the fluid that cools equipment and carries away contaminants.

Based on the division of hydraulics into hydrodynamics and hydrostatics, there are different types of hydraulic fluids. First, hydraulic oils used in hydrodynamic applications are called transmission oils. Secondly, hydraulic oils intended for hydrostatic use are called hydraulic oils. Moreover, in the latter application, applied pressures are high and flow rates are low. Therefore, hydraulic oils must be incompressible fluids that transmit power in a system or device.

When we think about lubricants, we can say that hydraulic oils are the most important lubricants after motor oils. Since the three main fields of hydraulics are stationary, mobile and flight hydraulics, we can say that each of these applications requires a specific hydraulic environment that is consistent with the operational requirements. When used optimally, hydraulic oils save energy, reduce wear and tear on the machine and components, thus extending maintenance intervals and extending the life of the machine.

TYPES OF HYDRAULIC OIL AND ITS APPLICATIONS

As with most lubricants, the primary category is mineral and synthetic hydraulic oils. The former are derived from petroleum, while the latter are synthesized or created artificially. In addition, there are also fire-resistant liquid-based hydraulic oils used in particularly sensitive environments, biodegradable food-grade hydraulic oils, STOU and UTTO universal mobile hydraulic oils and aircraft hydraulic oils.

As we mentioned at the beginning, hydraulic systems are everywhere and can be found in every industry. There are a wide variety of hydraulic machines, equipment and components that use hydraulics and require hydraulic oil to keep them running.

Hydraulic oil selection and hydraulic oil specifications depend on several factors. These include hydraulic system and hydraulic pump design and type, operating temperature and pressure ranges, and environmental considerations.

MINERAL BASED HYDRAULIC OIL

Mineral-based hydraulic oils are obtained from crude oil fractions. In addition, they are refined to a level where they achieve adequate lubrication properties. They are then enhanced with a system of additives. These additives perform various functions and may have anti-wear properties, rust and oxidation inhibiting properties, viscosity index improving properties and other properties.

Since they are petroleum-based, they are cheaper compared to their synthetic counterparts. Depending on the quality of the base oil and additive package, these mineral lubricating hydraulic oils can provide the same high performance as Valvoline HVLP and HLP conventional hydraulic oils. Additives found in mineral-based hydraulic oils protect hydraulic systems from corrosion, wear, and water contamination. They also improve the demulsifying properties and viscosity index of the oil, which improves their resistance to temperature changes. In addition, we can find hydraulic oils with cleaning/dispersing properties in this category.

SYNTHETIC BASED HYDRAULIC OIL

Synthetic-based hydraulic oil was intended to compensate for the shortcomings of mineral hydraulic oil. They are made from chemically produced base oils, which gives them better performance compared to mineral hydraulic oils. Moreover, they have proven performance at high temperatures, excellent oxidation stability and biodegradability. However, as synthetic fluids, they are much more expensive, can be highly toxic and potentially incompatible with some sealant materials.

FIRE RESISTANT FLUID BASED HYDRAULIC OIL

Both mineral and synthetic base oils are used in the production of highly biodegradable fireproof hydraulic oils. As the name suggests, these types of hydraulic oils are designed for use in areas where there is a high likelihood of fire, including aerospace, mining, steel mill and injection molding applications. Due to this important feature, they are used in many applications and are less expensive than synthetic hydraulic oils. However, when it comes to their anti-wear protection properties, they fall short of synthetic fluids. On the other hand, the additive system used in fire-resistant hydraulic oils improves corrosion protection, reduces friction and foaming.

Fireproof hydraulic oil can be mineral oil-based oil-in-water emulsions, synthetic water-based solutions, mineral oil-based water-in-oil emulsions, water-based and water-free.

FAST BIODEGRADABLE HYDRAULIC OIL

Hydraulic oils in this category were developed with increasing environmental protection standards. In addition, they ensure ecological compatibility and can be used in stationary and mobile applications in industry, forestry, mining, tunneling and earth-moving equipment.

In recent years, mineral oil-based hydraulic oils have been replaced by biodegradable hydraulic oils, such as Valvoline Ultramax Bio-46 premium synthetic hydraulic oil. In addition, they can be divided into several groups, including:

Water-insoluble vegetable oil types (rapeseed and sunflower oil).
Water-insoluble hydraulic oils
Water soluble hydraulic oils
Hydrocarbon products.

Due to their properties, biodegradable hydraulic oils are also used in marine applications and hydraulic systems of boats and ships.

HYDRAULIC OILS USED IN THE FOOD INDUSTRY

This category is based on numerous international guidelines that regulate which base oils and additives can be used in the composition of these hydraulic fluids. Food grade hydraulic oils have subgroups that indicate whether the lubricant is suitable for use in the food industry where direct contact with food cannot occur, and a subgroup where such contact may occur. The base oils of these hydraulic lubricants are special white oils, special polyalphaolefin grades and special polyglycols.

STOU AND UTTO UNIVERSAL MOBILE HYDRAULIC OILS

Universal tractor gearbox oil (UTTO) and super tractor universal oil (STOU) are hydraulic oils and fluids for gearboxes and hydraulic systems of agricultural machinery with and without "wet" brakes.

AIRCRAFT HYDRAULIC OILS

These oils are used in aviation hydraulic systems and can withstand high pressures and extreme climates with drastic temperature changes. Therefore, these fluids must be exceptionally thermally stable and have a high viscosity index. In addition, they must be fireproof and contain no pollutants.

ADDITIVES IN HYDRAULIC FLUIDS

The lubricating properties of hydraulic oils are achieved by adding additives. In addition, these systems of additives, mixtures of additives or additional packages have different properties and different functions. Creating an additive package is a very delicate process, as the additives must be compatible and complement each other.

Some of the properties of base hydraulic oils that can be improved are stability, anti-corrosion, anti-wear, viscosity and temperature stability, foaming, cleaning, water separation and coefficient of friction to name the most important.

Based on these functions, additives are divided into two main categories:

* surface-active additives, including anti-wear agents, friction modifiers, rust inhibitors, detergents or dispersants
* active additives, including viscosity index improvers, pour point improvers, anti-oxidation additives and defoamers.

An additional classification based on the system of additives used in the composition of hydraulic oil is as follows:

additive systems containing zinc and ash
zinc- and ash-free additional systems (e.g. Valvoline HLP ZF hydraulic oils)

MOST IMPORTANT PROPERTIES OF HYDRAULIC OIL

As we can see from the categorization above, hydraulic oils must have certain properties to meet the requirements of hydraulic systems and operating conditions. Whether it is a heavy duty application or an application with less extreme operating conditions, a hydraulic oil must:

• not compressible
• stable in terms of viscosity and at different working and climatic temperatures (high and low)
• fireproof
• non-corrosive
• anti-wear
• resistant to water contamination

In addition, the choice of hydraulic fluids must be cost-effective for the hydraulic equipment or equipment owner.

A single hydraulic oil usually cannot fulfill all the above points. Therefore, hydraulic oils are specially developed according to their conditions of use.

HYDRAULIC OIL VISCOSITY

The viscosity of hydraulic oils is a very important property, as it indicates its resistance to temperature fluctuations. The viscosity index of mineral-based hydraulic oils can be improved by adding additives. For example, high viscosity index hydraulic oils improve the performance of hydraulic systems and pumps at low temperatures. At the same time, they offer protection against wear at high temperatures.

HYDRAULIC OIL DENSITY

The density of hydraulic oil plays a very important role in the lubrication and performance of hydraulic machines. Typically, systems can only pump fluids of a specific density. Therefore, if the density of the hydraulic oil is affected, the efficiency of the hydraulic pump will also be affected. For example, as the density of a fluid increases, so does the erosion potential of the fluid. In systems with high turbulence, hydraulic fluid can wear out valves, piping, and other parts and surfaces in contact with the fluid.

High density hydraulic oil improves system antifouling by helping to suspend, transport and remove contaminants. In this case, the contaminants remain in suspension for a longer period of time and the filters remove them more efficiently, resulting in a system that is much easier to clean.

ADVANTAGES OF HYDRAULIC OIL

Every hydraulic oil is different and can offer different benefits depending on the application and additive package.

In general, hydraulic oils based on mineral oil or synthetic oil can offer the following advantages:

*Protection against corrosion and rust. In other words, hydraulic oils are hydrolytically stable.
Thanks to the stability of the viscosity of hydraulic oils, optimal operation is possible even at extreme operating temperatures and conditions.
* Protection against foaming, mud and precipitation. In return, system efficiency, reliability and performance increase.
* Protection when the hydraulic system comes into contact with air and water, which means that hydraulic oils have anti-oxidation properties.
* Filters in hydraulic systems maintain their filtration efficiency because hydraulic oils also act as a contaminant remover.
* Hydraulic equipment is protected from water emulsion, as the oil quickly separates water and prevents damage. This property is also known as demulsibility.
* Some hydraulic oils are biodegradable and can be used in sensitive environments.
* Wear and tear protection thanks to hydraulic oil additive packages such as Valvoline Ultramax HVLP and HLP and Valvoline Ultramax Extreme designed for heavy-duty applications. As a result, the life cycle of equipment and hydraulic equipment is extended.

IN CONCLUSION

Hydraulic systems that harness the power of fluids can be found in an impressive and wide range of hydraulic machinery and components. These systems are used in almost every industry in existence and are designed to work in a variety of operating and environmental conditions. The fluids used in hydraulic systems are hydraulic oils, which can be classified into several groups based on their composition and/or application. In addition, they are a means of removing energy, lubricating and cooling fluids of hydraulic systems, sealants and various types of contaminants.

You can find the hydraulic oils offered in our e-shop here.