Importance of the Filtration in Hydraulics

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Hydraulic FiltrationTo the extent that over time the importance of filtration grows. This is because of hydraulic equipment manufacturers reduce internal tolerances and increase the loads of the different elements (pumps, valves, etc..)

using the best quality oils, making the 'small' foreign particles that were not a problem now they are.



Today that there is the need to produce more and faster machinery is very demanded and downtime for maintenance is almost null, so you have to try that the machinery got not damaged, which can only be achieved if the Glossary Link fluid is kept free of contaminants.

Let's do a review of the fundamentals of filtration, with an explanation of the manyfacets of the topic. The terms used correspond to filtration in general, but mostly have a particular relationship with hydraulic oil filters and oil.

The fluid in the power transmission systems (fluid power) are the means by which this happens. But apart from this you could say it is the main function it has other that are secondary.

Glossary Link Lubricant. Prevents the components of the various hydraulic components to wear out.

Refrigerant. Helps the heat generated internally in the components to be quickly evacuated.

Sealant. When placed between moving parts to each other, helps to seal and prevent excessive oil leaks out internally.


The fluid most used in the world today is the one that comes from Petroleum oil. It has excellent lubricating properties, is relatively inexpensive and very easy to get. In very specific applications, such as blast furnaces in steel mills and aviation other compounds are used so that the fluid will not catch fire, are much less common, besides being more expensive, in many cases requires that the Glossary Link seals and some components be special for compatibility.



Contaminants are foreign elements to the fluid. In theory, the hydraulic fluid has to be pure, free of contaminants. From experience we know that is impossible to maintain afree fluid of impurities, but the goal is to keep the lowest possible level.

The pollutants are:

Air, water and solid particles.

Air in the hydraulic reservoir


The air is in minimal proportions in the oil normally, but when in large quantities due to problems with the suction of the  Glossary Link pump or Glossary Link aeration in the tank, the air will cause problems such as premature wear of the component with low lubrication, oxidation, bacterial growth, oil deterioration, spongy movement and noisy machine.

Water as a pollutant that reduce the natural lubrication also, it generates further oxidation, bacterial growth. It is detected by the white Color in the oil, like milk.


The solid particles are the most dangerous pollutants and more difficult to eradicate or Glossary Link control. Sand, dirt, steel, bronze, aluminum, the latter coming from outside or generated from the parts of the different elements themselves, which according to their size can generate accelerated wear, obstruction of Glossary Link control orifices in valves and pumps, parts binding Such as pistons and vanes in pumps and motors, spools in valves, etc. Depending on the size, the problems they bring are different. Particles less than 10 Glossary Link micron (1 Glossary Link micron= 1 millionth of a meter, or 1 thousandth of a millimeter) will generate slow (long time) wear, but depending on the concentration. And larger particles generate accelerated wear and catastrophic failures (rupture of parts such as shafts, rotary assemblies etc.).

The major source of such pollutants is the environment, the air surrounding a machine. For this reason is that manufacturers of hydraulic equipment built tanks sealed to prevent contamination from entering the system. The more loaded the environment (earth-moving machines, backhoes, tractors, etc.). the greater the chance of contamination. To give an idea of how this works, look at these statistics on how many particles get into a hydraulic system from the environment:


MANUFACTURING PLANTS AND MILLS 106 to 108 per minute *

CLEAN ASSEMBLED AND PLANTS 106 to 108 per minute *


You have to remove the pollutants that are already in the oil while avoiding
new ones from entering .

Removing the air is done correcting the source of this contamination, ie. loose suction, or low oil level in the tank, the tank returns that are above the level, or seals in pump shafts damaged.

For water contamination, we must examine the origin and correct it, and although there are filters to remove water from the oil, if there is too much it is probably more economical to change the oil.

For the solid particles there are several solutions as appropriate. Let's start by saying that if a system enter so many millions of particles per minute, the work to be done is monumental, billions of particles that a Glossary Link filter should remove.

Because there are so many different applications, and so many different environments in which the machines will work, the hours of work of the machine, or monthly frequency, that the solutions are also different.


Hydraulic Filters and Elements


The main point of entry of particles into a hydraulic system is the tank, therefore we must install a filter in the vent of the tank and ensure that the tank is sealed, it will nothave another point of income. If the environment is very polluted, a standard filterworks very well, but in loaded environments better filters are recommended. The oil that enters the tank from the system should be filtered very well using the return filters.The oil that goes from the tank to the pumps has to be filtered but given the restrictions in the suction, use wire mesh, at least to ensure that the pumps will not receive large particles.

If the hydraulic system contains dirt sensitive valves ( Glossary Link servo valves, proportional valves,etc..) Glossary Link pressure filters should be placed in the pump discharge.

For applications which should ensure a very low level of contamination you can use analternative filtration system, often with oil cooler, consisting of a Glossary Link motor-pump set, ahigh-capacity filter, contamination monitors (gauges) and has to be connected to work on two opposite ends of the tank.

The Glossary Link filter media used today are basically made of similar materials to the paper, but folded in multiple layers within a cylindrical Glossary Link cartridge having a large holding capacityin a relatively small in size. For having these elements a non-uniform pore size, is going be able to retain particles of many different sizes, so in order to select them you have to look very carefully at the manufacturer's specifications. The cheapest are made ​​of paper, but does not have good characteristics, are acceptable for most applications, but if there are in the system Glossary Link piston pumps, motors, or Glossary Link servo valves, fiberglass filters should be used.

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