Expanding Reservoir Air Filters

Tags: contamination control

In all vented tanks, the rise and fall of fluid levels is offset by a corresponding volume of incoming and outgoing air. Keeping the incoming replacement air clean is essential for contamination control and thus the reliability of hydraulic systems.

While targeting the system's reliability, JLM Systems Limited has developed the OilMiser™ Reservoir Aspirator (ORA) kit. This product represents a complete rethinking of reservoirs and storage tanks vented to the atmosphere. The kit builds on the unique features of the original OilMiser™ FILLorDRAIN™ which, during the initial development, focused on preventive maintenance.


Figure 1. ORA-1000-4100

In the Beginning
Removing uncertainty from any maintenance procedure translates directly into measurable productivity gains such as more predictable activity times, less resistance, more compliance and better results. With the unit, the five-micron air filter remains in place throughout the filling and/or draining procedure. If preferred, the aspirator can be reconfigured with an optional top-end coupler. These adaptors will accept air filters and breathers from other manufacturers. Female pipe adaptors can be used whenever clean or conditioned air is ducted from a remote supply.

Over the years, the reservoir aspirator kit has improved with the addition of a sampling port and off-line filtration connections. Essential elements for oil maintenance best practices include fluid handling, oil sampling, fluid cleanliness and air quality. The kit meets these elements.

Progressive Development
JLM Systems decided to take an extra step from focusing on the logic of preventive maintenance and took an interest in the science of reliability-centered maintenance, hence the development of the reservoir aspirator kit.

Traditionally, a 40-micron filler/breather was used on hydraulic reservoirs to control airborne contamination. Today, improved maintenance practices see air breathers with micron ratings of 10, five, two and even one micron absolute. High humidity also presents a challenge to the hydraulic reservoir, and in this situation, desiccant air breathers are commonly used.

Improved reservoir air breathers will have a positive impact on machine reliability; however, they fail to address three basic issues. The first is bidirectional air flow through the filter media. Second is the issue of the back flow of fumes and gases and third, the true differential pressure across the filter media.

The kit addresses these basic issues that limit the effectiveness of reservoir air breathers.


Figure 2. Bidirectional Ar Flow

Air Flow
Filter elements are designed, tested and rated for flow in one direction only. However on most hydraulic reservoir and liquid storage tanks, air breathers have bidirectional air flow.

Airborne contaminants collect in a random weave of fine filaments. These particles remain held in the filter media under unidirectional flow. However, particles blocked in one direction can be dislodged by flow in the reverse direction. Hydraulic reservoirs experience a rapid inward rush of air when oil flows outward and the hydraulic cylinders extend, and a greater air rush outward when the oil returns to the reservoir as the cylinders retract. Solid contaminants held in the filter media can work their way out of the filter media in either direction.

Unfortunately, flow stresses are also imposed on the fine media filaments. Under bidirectional flow, these filaments flex back and forth. Add in trapped particles oscillating back and forth, and the filaments will eventually fatigue and fracture. Over time, the air filter becomes a contamination generator.

The kit addresses this issue by offering two independent flow passageways in one body. The vertical airway is called the inflow control gate (or ICG port). The second passageway is termed the exhaust control outlet (or ECO port) (Figure 2). Both the ICG and the ECO are unidirectional passageways.

Fumes and Gases
Malicious fumes and gases can exit the reservoir via the ECO port, while replacement air re-enters the reservoir via the ICG port. Therefore, internal fumes and gases can be piped out of the immediate work area and can be further conditioned or safely released to atmosphere to meet local OSHA and environmental regulations.

Normally, the fumes and gases generated inside the reservoir exit through the air breather when the fluid level rises. These fumes and gases generally have an oily composition. Oily vapors can coalesce in the filter media, degrading the overall performance of the air breather. Desiccant air breathers that purge incoming air, also purge outgoing air as well. An oil film that builds up on the desiccating materials inside the air filter will reduce its overall effectiveness.

The ICG located on the ORA kit lets replacement air enter the reservoir in one direction only while preventing any exhaust air from exiting the reservoir through this gate or port. In the absence of contaminated back flow, the useful life of an air breather is increased.

Filter Element Life
The only true measure of the service life of a filter element is the differential pressure (or particle count) across the media. In the absence of accurate and meaningful measurements for bidirectional air flow through the filter media, most air breathers on reservoirs and storage tanks are replaced prematurely, or are left in-service far too long.

An optional vacuum gauge port is located on the ICG cavity, downstream of the air filter. Under unidirectional air flow, vacuum gauge readings are more accurate and reliable. The discipline of condition-based analysis can now be used to establish the useful life of an air breather.

Many hydraulic reservoirs operate in extremely wet and contaminated environments, or in hostile and dangerous locations. With the kit, they can now be safely aspirated both from and to a remote location. Clean air can be piped into the reservoir from a controlled source via the ICG port and exhaust can be vented in a controlled manner. The problems and complications caused by back flow are no longer mitigating factors.

The kit is shipped with all internal parts assembled. A tank-top gasket and mounting screws are included. The ORA can replace most reservoir filler/breathers that use a conventional mounting pattern of six holes X 2.88-inches BC mounting pattern. The basic kit comes standard with a one-inch NPT female pipe thread for the ECO port or an optional SAE-16 female O-ring port.

About the Company

JLM Systems Ltd. manufactures products for oil maintenance and machine reliability. For more information, www.oilmiser.com.