Ventilation dryers are used to protect a hydraulic tank from moisture. This measure completely prevents the ingress of humidity and water.

During use, the adsorber changes its color to a dark green and thus shows the maximum absorption capacity. If an adsorber is not changed after a complete color change, the air will not be dried. This means that the adsorber is useless and water finds its way into the tank.

Water through parallel aeration

If water in a hydraulic unit even though the mounted adsorber is orange, there can be several reasons. On the one hand, there can be a parallel ventilation opening or ventilation filter. Since a pure filter element of a ventilation filter has a lower pressure difference than an adsorber (filter with bulk material and valves), the air will flow in and out through this filter.

A parallel ventilation must be eliminated or closed by an additional adsorber. If there are different chambers in one unit, which can also be connected, it must be ensured that the air cannot flow into a system undried.

Water through cooling circuit

It is also possible that an existing water-cooling circuit allows larger amounts of water into the oil through a leak. Large amounts of water can get into the tank in a very short time and cause considerable damage.

Conclusion – Visability on the adsorber

A parallel ventilation of the hydraulic tank will not be visible on the adsorber. All of the air flowing in and out will flow through the “secondary opening” with lower pressure. In this case, the adsorber remains orange for a very long period of time.

If the adsorber does not or hardly changes color after 12 months, we recommend checking the oil and the function of the unit.

On the other hand, the adsorber will discolour from above in the case of water in the tank if the ventilation is forced to flow through it.

If the adsorber changes color from above, this is a good sign, as water is being absorbed from the inside of the tank. If this effect takes place over a very long period of time, the tank condition should be checked.


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