The ultimate in reservoir breathers?

KleenVent KV series reservoir isolators keep dust, dirt, and moisture out of hydraulic fluid by separating ambient air from air in the reservoir. Shown are some of the models with steel (black) or polyglass (blue) shells in sizes from 21⁄2 to 80 gal.

Open-circuit hydraulic systems need breathers so air can exit and enter the reservoir as the fluid level rises and falls, respectively. However, it has been well documented for years that you should prevent ambient air from entering the reservoir unless it has at least been filtered. This is the function of filter-breathers — to clean any air that enters the reservoir as fluid level drops from normal system cycling.

Without the filter, dirt — or even foreign objects — can enter the reservoir and contaminate the hydraulic fluid. But even with a filter, humidity in the ambient air can still enter the reservoir. When this occurs, moisture in the air can condense as liquid water and further contaminate the hydraulic fluid.

Moreover, the particulate filter element will eventually become clogged if it is not changed periodically. If clogged badly enough, air will not be able to pass through the filter-breather, which could create a partial vacuum in the reservoir. This, in turn, could cause cavitation of the pump, which usually results in premature pump failure.

The next step in filtering air that enters the reservoir is a desiccant filter-breather. These breathers contain a filter to trap airborne particles, and a desiccant dries the air by absorbing moisture contained in the air. However, the desiccant eventually will become ineffective, so unless they are monitored or changed periodically, they can allow moisture to enter the reservoir.

Keep the bad stuff out
So how can you keep air, dirt, and moisture out of the reservoir without having to periodically change something? One technique gaining in popularity is a reservoir isolator.

A reservoir isolator incorporates a diaphragm chamber that captures ambient air as fluid level decreases. But because it is contained completely within the diaphragm chamber, the ambient air does not come in contact with air inside the reservoir. Therefore, airborne dirt (even sub-micronic particles), water, and chemical aerosols are isolated from the hydraulic fluid. Plus, because there are no filter elements toclog or desiccant that becomes depleted, reservoir isolators are essentially maintenance free.

Secret of their success
A new line of reservoir isolators was recently introduced by Parker Hannifin Corp.'s Hydraulic Accumulator Div., Rockford, Ill. Dubbed the KleenVent KV series, they use an elastomeric diaphragm that expands and contracts with decreases and increases in the volume of air in a hydraulic reservoir.

Rob Lorance, of Parker's Hydraulic Accumulator Div., explains, "Air is one of the worst contaminants in hydraulic systems because it promotes oxidation of the fluid, which, in turn, degrades the properties in the oil and eventually leads to varnishing of components. Air also brings moisture with it into the system, which can condense in the reservoir and fall into the oil as water. This leads to further degrading of the oil and its additives. Hence, a significant environmental benefit that comes from installing a KleenVent reservoir is much less waste for disposal."

With proper bladder material selection, KleenVent reservoir isolators are compatible with virtually any industrial fluid. Lorance says they are ideally suited for use with hydraulic systems in steel and primary metal mills, foundries, pulp and paper mills, power generation plants, automotive plants, and in any highly contaminated or humid environment. A universal kit is available for quick and easy 15-minute installation to existing power units.

Variety for wide application
The KleenVent KV series of hydraulic reservoir isolators includes:

  • eight models with capacities ranging from 21⁄2 to 80 gal
  • polyglass shells for 21⁄2-, 5-, 10and 20-gal models
  • steel shells for 20, 40, 60 and 80gal models
  • four bladder polymers to fit a wide range of fluids and operating temperatures from –40° to 250° F, and
  • an optional pressure/vacuum breaker to protect the reservoir in the event of a sudden fluid loss or over-filling.

For more information on KleenVent KV series reservoir isolators call (815) 636-4100 or visit