The OilMiser Reservoir Aspirator overcomes the limitations of conventional filter-breathers by providing two separate flow paths — one for incoming air, and one for outgoing air.

Unless it is part of a sealed system, a hydraulic reservoir expels or draws in air whenever the fluid level within it rises or falls. Any dirt or moisture in the ambient air can work its way into hydraulic fluid in the reservoir unless a means of drying and filtering the incoming air is provided. Normal convention had been to use a 40-μ filler-breather to clean the incoming air somewhat. More recently, many breathers have incorporated 10-, 5-, 2-, or even 1-μm filter elements and desiccants to absorb moisture that otherwise would enter the reservoir.

The benefits of keeping ingested air clean and dry cannot be overstated. However, an air breather alone may not address three basic issues.

First, filter elements in breathers are designed for unidirectional flow. However, air flows into and out of a hydraulic reservoir, which compromises the effectiveness of a unidirectional element.

With a unidirectional filter, airborne particles collect in a random weave of fine filaments and remain there. However, reverse flow can dislodge these particles. Therefore, solid contaminants trapped in the breather’s filter media can work their way into the reservoir from the cyclical air flow caused by the fluid level rising and falling.

Second, fumes and gases generated inside a reservoir exit the breather to the ambient air whenever fluid level rises. The gases generally have an oily composition. They can coalesce within the filter media, degrading the breather’s effectiveness. Desiccant breathers suffer the same fate. Any oily residue buildup on the desiccant can render it less effective.

Some manufacturers recognize this problem and provide a check valve that routes outgoing air directly to atmosphere, without going through the filter or desiccant.

Third, unlike hydraulic filters used within the system itself, breathers generally do not have any type of pressure or vacuum gauge to indicate when they have reached their dirt-holding capacity. Therefore, they usually are left in service long after their effectiveness has been depleted.

The OilMiser Reservoir Aspirator (ORA), from JLM Systems, Richmond, BC, Canada, addresses all three of these issues. First, it has two separate flow paths for air.

Incoming air enters through the top, and a check valve prevents any backflow of air within the reservoir from entering the ORA. A second path routes air from the reservoir out to the atmosphere. Again, a check valve prevents ambient air from entering the ORA. Also, a vacuum gauge port is provided to assess the condition of the filter element.

For more information, call JLM Systems at (604) 521-3248, e-mail info@oil miser.com, or visit www.oilmiser.com.