Contamination of hydraulic circuits

Technical advice

The origins of hydraulic contamination are multiple and can often cause premature wear of your system. Here are the 3 most common causes of hydraulic system contamination. See how to prevent them, detect them and what to do when you are faced with this situation.

What are the sources of contamination in a hydraulic system?

Contamination of hydraulic fluid by water

Contamination of the fluid by another liquid (very often by water) is a significant cause of hydraulic contamination. This mixture can cause serious damage to the system such as corrosion or premature wear of the circuit. In addition, this type of contamination can introduce a change in chemical properties and a decrease in viscosity. This will have a direct impact on the lubrication of the hydraulic system and therefore on the wear of the system. In addition, as the oil passes through a filter, this mixture could reduce its efficiency and life. A simple fluid contamination may seem harmless, but it can have a particularly damaging impact on the hydraulic system.

The contamination of the hydraulic fluid by a particle

Another observed source is contamination by a solid particle that enters the system. A solid particle is defined as dirt, rust particles, dust particles or metal chips. The particle does not have to be large enough to damage a hydraulic system. Even very fine particles can travel through the system and cause blockage or premature wear of components. A larger particle could clog the system and cause even greater damage.

There are many sources of solid contamination. Contamination can be introduced by:

a damaged or improperly installed seal,
a damaged motor or pump that breaks down and leaves particles in the fluid,
when changing system components,
connection of hoses,
etc.

Air contamination of hydraulic fluid

A leak in the hydraulic circuit or a lack of tightness in the fittings can introduce air into the system. Air in a fluid can also cause problems such as oil foaming, chemical reaction and even oxidation. It is important to ensure that you have quality filters in good condition.

Can damage to an oil contaminated hydraulic system be prevented?

Several measuring devices can be used to prevent damage to a hydraulic system from contamination.

The filter maintenance indicator is a measuring device designed to monitor filter efficiency in real time. It will signal the presence of anomalies through its alarm system.
Water content meters can be used to evaluate the presence of water in a hydraulic system.
For solid particles, there is a particle counter that continuously measures the level of pollution in the system as well as the evolution of the pollution. An alarm is issued in the event of an anomaly in the system that exceeds the admissible threshold.

Measuring devices such as those offered by Rexroth can be used to determine the level of contamination in hydraulic systems.

How to avoid particles when filling oil?

Often a bucket/gallon and funnel are used to transfer oil into a system. This is a common method, but it is risky. The funnel must be clean and dry, and therefore free of dust, particles, water or other fluids. The “cap” or cup of the oil gallon must be clean to prevent particles from falling into the funnel and contaminating the system. In addition, there are filtration pumps that suck the oil from a gallon and transfer it to a tank. This method is useful in preventing contamination and ensuring the system is protected.

How do I know if my oil is contaminated?

The contaminant is not always visible to the eye and usually requires further analysis. There are tests that can be used to analyze the oil and determine whether or not contaminants are present. Most often, the analysis allows to evaluate the viscosity, the water content as well as the content of solid particles.

How to clean a contaminated system?

There are equipments on the market which allow a depollution of the fluid in a hydraulic circuit. The purpose of these systems is to circulate the contaminated fluid in an external equipment in order to eliminate the contaminants (water, gas or particles) present. Mobile filtration units can be connected to the circuit, allowing the fluid to be cleaned in the circuit. This type of unit has a pump whose flow rate will be determined according to the fluid tank in order to obtain a cleaning of the system in an optimal time. There are also so-called fluid purifiers. This type of equipment allows to clean a circuit containing particles but also water and gases that would be contained in the fluid. This system is more complete than the filtration unit. Depending on the level of contamination in the system, it may be necessary to completely drain the system and then clean and add clean oil.

In conclusion

The contamination of a fluid can be damaging to a hydraulic system, whether it is a contamination by gas, by a particle or by another fluid, the repercussions are not without consequences. In addition to the cost of cleaning up the system and repairing damaged components, the loss of productivity can be significant. It is therefore important to ensure that the system is well maintained and free of particles during maintenance (even if it is not always obvious).