How to Choose a Desiccant Breather

Noria Corporation
Tags: contamination control

"Can you offer any advice on selecting desiccant breathers for gearboxes in the mining industry? Which factor plays more of a role in breather selection: the sump headspace above the oil level, ambient conditions like high humidity or a dusty environment, the machine type (mobile unit or fixed installation), the type of oil and its application, or the oil’s cleanliness requirement?"

Desiccant breathers are great contamination control accessories for machines that would otherwise be breathing in dirty, wet air. These devices allow for the air being ingressed by the machine to be cleaned of particulate matter and also dried to help control the amount of water in the oil. This becomes very important in critical machinery as well as those that are in harsh environments where the oil may become contaminated and break down quickly.

These breathers have a particulate filter phase and a moisture absorption phase. Both of these phases are essential not only for the health of the lubricant but also for the health of the machinery. Solid particulate contaminants can lead to machinery failure mechanisms such as three-body abrasive wear. Moisture contamination can result in adhesive failure mechanisms and increase the rate at which lubricants break down.

Oil by nature is hygroscopic, which means it will absorb moisture readily from any source, including from humidity in the air. By utilizing a desiccant breather, you can reduce the amount of moisture in the air that is entering the system.

The headspace is important to keep in mind, as it can help determine the amount of “breathing” that will occur inside the machine. Therefore, it is imperative to understand how much the headspace can fluctuate. For instance, the headspace in a splash-lubricated gearbox will fluctuate less than that of a hydraulic system reservoir where there are large volumetric changes within the sump. This volumetric flow rate must be within the breather’s capabilities, or it may cause a vacuum or pressurization condition inside the component.

The environment in which the machine operates should be considered as well. For severe environments, such as those with water spray and large amounts of dirt, select a desiccant breather that can handle the expected amounts of contamination. For the most severe environments, you might choose a breather with a check valve or bladder assembly to help prolong the desiccant’s life.

The cleanliness level required by the machine must also be taken into account when determining the desired desiccant quality. Of course, the more critical machines should receive the most attention.

Considering all of these variables will provide the most effective way to select a desiccant breather. While a number of options are available, some are better suited for certain situations. Remember, it is far better to provide more protection than needed rather than to skimp on quality in order to save money.

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