How do you select the right hydraulic filter?

There are many things to look at when selecting the right hydraulic filter. Below we have listed the most important ones for you. So the first, and most logical thing to do is to look at the dimensions. Does this filter fit my machine? However, there are more things to pay attention to, such as the filter material, the filter efficiency, whether the filter is suitable for hydraulic oil and whether the filter is suitable for the load that your machine places on it.

Dimensions of the hydraulic filter

There are a number of things to pay attention to regarding the dimensions. First of all you have to look at the “outer diameter” and the “inner diameter”. These dimensions are especially important to get a good fit and to ensure that the filter seals properly and does not leak.

The second thing to look at is the threads used. This can be metric or inches. The most important thing here is not so much which measure is used by the manufacturer, as long as the thread fits properly.

The third is often an underexposed part of the filter; the size of the filter housing itself. This is quite a strange one because the size can sometimes differ from the capacity. A higher quality filter, for example with a better filter media, can still be the better filter in a smaller package. However, if you have heavy loads on your machine, high pressures in your hydraulic system or many pressure peaks, it is better to go for the larger of the two if in doubt. The large filter simply has more filter surface and can therefore better deal with these challenges. If you use a liquid or oil with a higher viscosity, it is better to go for a filter with a large surface area, because the oil simply flows less easily through the filter and you want to limit the pressure loss that occurs in every filter.

Suitability for the hydraulic oil to be filtered

You cannot see the interior and the filter media from the outside. This is why many filter manufacturers list it in the filter properties. In principle you can say that there are two main types of liquid; mineral base and synthetic.

The mineral fluids or oil are often cheaper, but have the disadvantage that they are more sensitive to temperature fluctuations and can often contain moisture. Synthetic oil is in many cases the better choice, but it also has its disadvantages. For example, certain synthetic oils can attack cellulose filter media and the filter sealing rings must also be made to withstand this. In practice, when using synthetic oil, it is better to opt for a filter with a filter media made of fiberglass.

Operating pressure of your hydraulic filter

This one is pretty self-explanatory. Your new filter must be able to withstand the hydraulic pressure in the system. But there is also another reason to look at this property when selecting the right hydraulic filter. Pressure loss occurs in every filter because the oil has to pass through something instead of flowing freely.

With a higher operating pressure or many pressure peaks, it is better to go for the larger filter with a larger filter surface. This minimizes pressure loss and maintains sufficient operational pressure in your system after the filter. You also often see that the more expensive filters can handle a higher operating pressure and have less pressure loss in the filter. If your machines require a lot of pressure, for example in larger excavators, tractors and shovels, use an A-brand filter and, if available, the larger alternative.

Filtration efficiency of your hydraulic filter

This is often referred to as the beta ratio or beta coefficient. This seems like quite a technical term, but it is fairly easy to explain. The beta ratio indicates how many impurities and what size particles the filter can remove. This involves looking at how many particles of a certain size still pass through the filter. For example, β10=100 means that of all the 10 micron particles that pass through the filter, only one in a hundred is not filtered and therefore comes out the other side.

The filtration efficiency in the filter is often indicated as a percentage. The differences sometimes seem very small, for example 99.9% compared to 99.99%, but in this specific case this means that ten times more contamination passes through the filter with filter one compared to filter two.

Absorption capacity of your hydraulic filter

This indicates how many impurities the filter can handle until it loses efficiency. All particles that are filtered out naturally remain somewhere. These slowly clog the filter and ensure that the flow is no longer optimal and, in the worst case, that the filter no longer does its job properly and that contamination passes through the filter. The first does not seem so bad at first glance, but when the flow in the filter is no longer good, the pressure in the filter and the pressure loss increase. The latter in particular means that your machine will have more difficulty delivering the same performance. This ultimately results in higher fuel consumption of your machine. Another disadvantage is that a lower pressure after the filter can cause cavitation in your hydraulic pump or hydraulic motor. This is a phenomenon in which tiny air bubbles form in the oil and implode. This implosion creates an extremely high temperature, up to thousands of degrees, which literally eats away the inside of your engine or pump.

It is also true that a clogged filter causes the temperature in your hydraulic system to rise. This has major consequences for the lifespan of your components, valves, hoses, motors and pumps. Roughly speaking, you can say that at a hydraulic oil temperature of 85 degrees instead of 60 degrees you can increase the lifespan of components by 5 to 10. Of course, this also applies to your filter and the filter material, but that is the least of your worries in this case.