Why is it necessary to maintain hydraulic and lubrication oils to avoid contamination and degradation?

Particulate and water contamination are the most frequent causes of hydraulic system failures and shutdowns. Because of this, knowledge of the precise level of contamination can be critical to the efficiency and functionality of the system and must be monitored and corrected when necessary.

Contamination of oils eventually leads to their degradation and, therefore, to the loss of their properties and a reduction in their useful life.

A number of specific consequences of oil contamination are premature clogging of filters, increased component wear, high noise, corrosion, cavitation, abrasion and erosion, degradation of additives and, finally, unscheduled downtime and costly breakdowns.

In terms of degradation, oils that are stored or in service in hydraulic systems eventually undergo changes in their composition and lose their physicochemical properties over time. However, depending on the type of oil and the working conditions and environment, this deterioration can be more or less controllable and frequent.

Oil degradation leads to a number of unwanted products that can result in varnish deposits, the presence of water - which can lead to corrosion - and damage to key parts of the hydraulic system, such as servo valves or pumps.

What are the main causes of oil contamination?


The contact of the oil with water leads to a chemical reaction in which the oil molecules react with the oxygen in the water, generating new compounds that alter the properties of the lubricant. In addition, a high level of oxidation can cause acid corrosion, thickening of the oil or variation in viscosity with respect to the original oil, increase in the level of dirt in the oil (sludge), etc.


It is the consequence of oxidation and other chemical reactions that break down the oil. The resulting chemical compounds, such as hydroperoxides, carboxylic acids, ketones, aldehydes, etc., are generally soluble in water and can further accelerate the hydrolysis process. Water contamination by condensation also leads to the risk of corrosion and premature wear of the pumps.

Thermal degradation

The molecular bonds of the oil weaken at high temperatures, above its thermal limit, causing its decomposition and propensity to form new bonds with other elements.

In short, oxidation, hydrolysis and temperature increase in oils trigger a series of chemical reactions that cause the decomposition and degradation of these oils and their additives. Acid compounds and resins are generated that can precipitate, forming varnishes or lacquers, sealing valves, collapsing filters, etc., which represents a high risk for the protection and correct operation of the systems.

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