Hydraulic oils

These properties should be provided in the ideal hydraulic fluid:

Although there is not a single liquid with all these ideal characteristics, we can choose the most suitable liquid for the hydraulic system, and it has been found that mineral oils with some chemical additives can meet most of these characteristics.

The optimal choice of hydraulic oil requires full knowledge of the system in which it will operate, as the engineer must know the basic characteristics of the system in the following respects:

Hydraulic oil:

Hydraulic oil consists of basic oil and a selected set of additives that work to give the oil its final properties according to the level of oil performance

First: Add-ons of the viscosity factor enhancer:

The highest and lowest operating temperature rates, as well as intra-system pressure, determine the viscosity requirements for oil.

At the highest operating temperatures, the oil must maintain a lower viscosity in Khin that it must maintain a degree of viscosity that allows a pump in low temperatures.

Second: Additions to preventing wild:

Wild is the inevitable result of metal friction, so the designer's main goal is to reduce wildness by preventing metal friction by developing special additions.

Where the use of oils and additives reduces the use of oils and additives that will make a thin layer (membrane) of oil prevents the use of moving metal pieces

It should be noted that excessive wildness may be due to poor operating conditions such as excessive pressure or insufficient cooling.

Third: Water separation additions:

The hydraulic system introduces large amounts of water during operation through air loaded with water vapor (moisture) and these quantities can be removed by discharging them from the oil tank medicine periodically

However, small amounts of water can contain inside the oil, especially if the oil tank is relatively small.

Hydraulic oils may be added emulsion contraindications to increase the speed of water separation

Fourth: Additions to the prevention of foams:

When oil carries air, it would harm the hydraulic system, so oil should be prevented from loading with air either by oil additives or by allowing air to get out of the oil inside the tank, and in general there are two types of foams:

Surface foams often accumulate on the surface of the oil in the tank
Air suspended inside oil

Surface foams are the easiest to handle as they are prevented by foam-proof additions and the proper design of the oil tank contributes to reducing the formation of organs and giving them enough time to disappear.

As for the suspended air, it causes major problems in the hydraulic system. In addition to the loss of pressure, it may cause the phenomenon of relapping.

Warning: The use of some types of anti-surface foam formation additives at high concentration may increase the chance of suspended air

Fifth: Oxidant and Rust Prevention Additions:

Hydraulic oils contain echo prevention and oxidation additions and the addition of echo prevention works to protect metals from rust as the addition of oxidation prevention prevents oxidation of oil and thus prolongs its life

There are two main problems when talking about the problem of eating:

Chemical acid-induced eating
Rust caused by moisture

Echo occurs when oil-contaminated water attacks the iron parts of the hydraulic system and repellents protect parts of the system from rust.

While oxidation of oil results in acids that process chemical eating of metal and antioxidants prevent the formation of these acids by preventing oxidation of oil

Hydraulic oils (lubrication and wild)

The pressures on modern hydraulic systems and the great development of micromechanics have resulted in very precise retreats between moving parts.

For example, some control valves are produced with a allow of 5 mμ, which is equivalent to five million meters.

Hydraulic oil creates a membrane that keeps those fine parts apart, filling the void in what is known as hydrodynamic lubrication, resulting in low ground rates and allowing components to reach the validity period, which may amount to several million pressure cycles.

The thickness of the lubrication membrane depends on:

For the wife of oil, the load is on the oil.
Relative speed between moving surfaces

Equipment designers try to avoid the critical lubrication phase by using hydraulic oil with a suitable viscosity, but the viscosity of oil changes by changing temperatures and loads and speeds vary greatly during operating cycles and as a direct result of this most hydraulic components work part of the time in the critical lubrication area.

When the mechanical parts work in the critical lubrication area, contact occurs in the moving surface parts, causing fine particles to eat from the surface of the metal and these molecules move to the liquid and move with it within the hydraulic system and if the system cannot get rid of them in the filtering process causes a violent mechanical wild.

Pollution of hydraulic oils:

Hydraulic oils perform four basic functions

Power transfer via hydraulic system
Lubrication of metal parts
Needle the hand of the components of the system
Working as a governing substance that prevents pollutants and dust from entering the system

If any of these functions are disrupted, the hydraulic system will not function properly, which means that it is very possible that a sudden failure may reach the stage of collapse of one of the components of the system.

Pollutants enter the hydraulic system in several ways:

As part of the system itself, as pollutants from manufacturing and installation processes.
Produced internally in the system as a result of operating conditions
Gained from outside the system during operation

The effect of pollutants in the hydraulic system is shown by:

Mechanical intervention
Chemical interaction with: hydraulic system components – hydraulic oil
- Hydraulic oil additives

Mechanical intervention works on:

Dam oil corridors with pollutants
Mechanical ground work between solid pollutants and the surface of the inner metal

Chemical reaction includes:

Echo formation and other oxidation products
Turning oil into other unwanted ingredients (acids, deposits, varnishes)
The additions are eaten (and sometimes turn into harmful products on the lubrication system)

Any of these interactions, if an event would be very harmful to the hydraulic system, and without protective measures and protection of hydraulic oil, the resulting problems could escalate into a malfunction in the system's components.

The symptoms of wildness are reducing the efficiency of the system and reducing the reconstruction of the components.

In the bulbs the land is observed by low pressure as a direct result of the increased dimensions of the clearances and when the output of the film decreases the pressure in the hydraulic system decreases and the efficiency of the system as a whole deteriorates

As for valves, the wild increases the internal leakage rate and the effect of this leak in the system depends on the type of valve, for example:

In the valves used to control the rate of transmission increase leakage means increased transmission rate and in valves designed to control pressure, increased leakage causes weak pressure within the circuit

It also shows the mechanical effect of "wild output molecules" in making the internal parts of the system such as valves and parts of the valves variable flow pump stuck and operating strangely and volatilely and this is evident with the flow of syriac where it appears in the form of irregular operating mechanisms

Pollution of hydraulic oils with water

Water pollution in hydraulic oils is just as harmful as pollution with solid pollutants.

In general, oils have a degree of water saturation, and when the water content is lower than that degree, the water is completely dissolved in oil, and the degree of saturation of oils with water varies depending on the different quality of the basic oil, but it is in the range of 500 ppm at 23°C.

And when the percentage of water in oil is higher than saturation, the water is suspended with oil, which means that it is in the form of drops suspended with oil and these drops are collected sometimes and deposited at the bottom of the tank and sometimes as a result of the continuous flipping process in the system these suspended drops turn into tiny drops and spread inside the oil

Chemical effect of hydraulic oil pollution with water

Water interacts with most components of the hydraulic system where:

Reacts to iron alloys, forming a echo.
Water encourages eating through the formation of the galvanic cell where water works on the formation of electrolyte and in the presence of different minerals arranged in the electrochemical chain within the hydraulic system activates eating
Water reacts to oxidation inhibitors found in oil, producing acids and deposits where acids act as chemically eating minerals (Acid Metal Attack) while sediments act as solid oil pollutants.
At high temperatures (above 60°C), water reacts to ZDTP wild prevention additives, leaving oil without adding wild blocking, causing high mechanical ground.