Integrated Precleaner/Filter Designed To Increase Filtration Efficiency

Diesel Progress North American Edition, April, 2001 by Mark McNeely

One of the many decisions an equipment manufacturer makes is whether to add an air intake precleaner to a machine's engine air filtration system. Yes, the precleaners add some amount of restriction to the air filtration system, but they have also clearly demonstrated their ability to extend filter life, especially the harsh operating environments of the off-highway equipment industry.

Precleaners have been particularly useful where airborne contaminants, such as dust, sand or other debris, quickly clog filter elements and rob engines of their peak performance. While precleaners have typically been "add-on" pieces to engine air intake systems, a new integrated precleaner/intake filter canister from Enginaire Clean Air Systems is designed to combine both the initial air cleaning capabilities of a precleaner with the primary cleaning of the main paper filter element.

Enginaire's integrated air filter canister with its built-in precleaner provides an axial flow of air through the filtration system and thus avoids many of the airflow restrictions of a tangentially oriented precleaner/filter arrangement, according to Bill Decker, president of the Janesville, Wis., company. The integrated VLR (very low restriction) filter/precleaner offers a four-stage filtration system that is deigned to be less restrictive than traditional tangential entry canisters.

"The VLR is basically a filtration system that decreases the airflow restrictions by having more of an axial flow of air," Decker explained. "By doing some appropriate deflections and changing orifice sizes we have been able to cut the restriction of the precleaner without sacrificing cleaning efficiencies."

The VLR filtration system's first three models are designed for airflow capacities of 5 to 20 cfm, 20 to 120 cfm and 75 to 250 cfm. Further product developments will bring the capacities up to 500 cfm.

Decker noted that in addition to cutting air restrictions, the VLR filter system is also smaller in size because it eliminates the "right angle" precleaner/filter arrangement of a tangential system. "When we're out talking to customers we've found that their requirement is to make the filtration system smaller," he noted. "Everyone wants the canister to fit underneath the hood now.

"Assuming identical paper filter elements, the restriction of these systems then really becomes the design of the canister. That's what is relevant," Decker continued. "So I have designed the restriction out of the canister and increased the overall exposure of the paper element. Using roughly the same amount of energy from the restriction saved, I am able to run the precleaner."

In a test of three arrangements of air filtration systems, Enginaire made a comparison of air filter life that demonstrated its VLR system to be the least restrictive filtration system. On its airflow bench, in accordance with SAE J726, the company introduced SAE course dust at a rate of 10 grams per 80 seconds to the inlets of the three systems. The flow rate was maintained at 50 cfm by adjusting flow after each 20 grams of dust that was introduced. The test was performed using a common paper element and run until each system reached a pressure drop of 20 in. of water.

The results concluded that the VLR integrated filtration system was capable of ingesting the largest amount of course dust before reaching the pressure drop limit.

"If somebody is happy with the filter life they're getting but they want a smaller package, now they can use a smaller precleaner and a smaller filter to get the same result," Decker said. "Conversely, some OEMs are looking at anything that will help in extending maintenance intervals, whether it's change intervals for oil or air filters."

Decker noted that just about any on-or off-highway machinery could benefit from use of a precleaning air filtration system and that Enginaire has had particular success in the commercial lawn and garden equipment industry. "We've been on several OEMs of commercial lawn and garden equipment and our business is growing in that industry," Decker said. "Regardless of the application, the precleaner is what gives us the differences in efficiency and prolonged filter life over a standard canister. And it's a nice, small inline package."

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