Hydraulic oils: why can a mistake in selection be fatal?
The importance of hydraulic oil for the normal operation of a hydraulic system is hard to overestimate because its primary purpose is to transfer mechanical energy to the operating units. But what can happen if it is chosen incorrectly? What characteristics should you pay attention to when buying? What types of hydraulic oils are available on the market, and what is their functionality? Read the answers to these questions in this article.
What is hydraulic oil, and what is its role in equipment maintenance?
Hydraulic oil is an integral part of any hydraulic system used in most branches of modern industry (mechanical engineering, aircraft manufacturing, metallurgy, shipbuilding, agriculture), as well as in special equipment and vehicles. Their popularity is due to the simplicity of the device, combined with reliability and ease of maintenance.
In these systems, hydraulic oil is necessary for the transmission of mechanical energy and forces. It is also responsible for heat exchange processes and the lubrication of components.
There are four main functions of hydraulic oils:
- Energy transfer: It enables the efficient transfer of hydraulic energy, as hydraulic oil is not compressed and flows easily through the hydraulic circuit.
- Lubrication of system elements: All moving parts must be well-lubricated to minimize friction and wear.
- Protection of parts from corrosion and various impurities.
- Cooling the system.
It is crucial to adhere to the manufacturer’s recommended oil change intervals when servicing any hydraulic system. It is also necessary to consider its properties: they must comply with the recommendations specified in the operating instructions.
Incorrectly selected oil or oil that has exhausted its properties can lead to the malfunction or complete failure of the hydraulic system.
Types of hydraulic oils
There are many types of hydraulic oils available on the lubricants market. They are usually classified by their application.
| Type of oil | Characteristic |
|---|---|
| Industrial (I-20A, I-40A, HLP) | These are the so-called base hydraulic oils, intended for units and machines that operate under low and medium loads, as well as under normal temperature conditions . They use a minimum of additives . |
| All-season (VMGZ-45, HVLP) | An excellent solution for servicing hydraulic systems of mobile equipment (trucks, tractors, construction equipment, etc.), which is often used outdoors and is exposed to sudden temperature changes . These oils have a high viscosity index. |
| Arctic (VMGZ -60, Arctic HVLP 32) | It is clear from the name that they are used to service hydraulic systems of equipment used in the Far North . They are designed for operation at temperatures down to -60 °C . |
Among international classifications, the most common standards are those of DIN and ISO .
ISO (International Organization for Standardization) is an international organization that has been specializing in the production of standards for 77 years.
According to ISO 11158 standard, hydraulic oils are divided into:
- ISO-L-HH — mineral, additive-free;
- ISO-L–HL — HH oils, which contain anti-corrosion and antioxidant additives;
- ISO-L–HM — HL oils with anti-wear additives;
- ISO-L–HR — HM oils with a high viscosity index;
- ISO-L–HV — also have a high viscosity index and are used primarily for construction and marine equipment;
- ISO-L–HG — HM oils with enhanced anti-vibration and anti-seize properties for sliding guides;
- ISO-L–HS are synthetic hydraulic fluids with special characteristics that do not have fire-retardant properties.
DIN (Deutsches Institute fuer Normung e. V.) is a German standardization institute. It is considered one of the main leaders in the development of standards and regulatory documents.
Classification of hydraulic oils according to DIN :
| Name | Description
|
| DIN 51524 (H) |
The simplest type of hydraulic oil, which is used in units that do not require special properties of liquids. Mineral, does not contain additives. |
| DIN 51524 Part 1 (HL) | Oils of this group are ideal for internal hydraulic systems with low pressure. They contain additives against corrosion and oxidation. |
| DIN 51524 Part 2 (HLP) | Working oils for modern hydraulic systems that are used indoors with small differences in operating pressure. As a rule, they contain a complex additive package. |
| DIN 51524 Part 3 (HVLP) | These oils are specially designed for hydraulic systems of mobile units. They cope well with their tasks even under conditions of sharp temperature changes. They must have a viscosity index higher than 140. |
The main mistakes when choosing hydraulic oil
In fact, the biggest mistake you can make when choosing hydraulic oil is to buy a product that is completely unsuitable for servicing the mechanism .
This happens when a person ignores the recommendations of the equipment manufacturer. As a rule, the operating manual for any unit specifies which technical characteristics of the oil must be taken into account when purchasing it, since different types of hydraulic systems require fluids with certain properties and qualities.
Using hydraulic fluid to service units for which it is not suitable can lead to serious damage and complete failure of the system.
What can happen if you choose the wrong hydraulic oil?
If the hydraulic oil does not meet the technical parameters recommended by the equipment manufacturer, this can cause many problems in its operation.
The most common of them are :
- Severe wear of pumps. This occurs because, in order to save money, low-grade oil is poured into the hydraulic system.
- Clogging of filters that stop passing contaminants, causing solid particles to continue to circulate through the system, quickly rendering its components unusable.
- Premature degradation of elements . This can happen precisely if the oil is selected incorrectly. For example, if its viscosity does not correspond to that recommended by the manufacturer.
- Reduced operating speed . This usually occurs due to contamination of the working fluid, as a result of which the hydraulic system components can become covered with deposits, which will slow down their operation.
- Decreased pressure in the system . This problem can be encountered if the viscosity of the oil decreases with increasing temperature. Therefore, when choosing it, it is worth considering the temperature values recommended for its operation.
Each of the above problems can be avoided by choosing the right hydraulic oil, which is suitable for servicing a specific hydraulic system in all respects. In addition, it must be of high quality and meet all the requirements of world and domestic standards.