In a recent Machinery Lubrication magazine article (September 2005), author J. Bennett Fitch discussed the benefits and inherent weaknesses of magnetic filtration devices. This article addresses and eliminates many of the inherent weaknesses found in these devices.

The Nature of the Problem
Studies by industry experts, research institutions, professional associations and others, have consistently determined that very small ferrous debris, often less than five microns, traveling through a vehicle's lubrication system may cause considerable damage to the power train: such as to the engine, transmission and other wear-sensitive surfaces. This problem is also present in nonautomotive equipment and machinery that rely on lubricating oil.

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Detail showing outflow orifice and magnetic caps

In addition to improving engine reliability, lubricant cleanliness can have a sharp impact on lubricant service life (drain interval). Wear metal suspended in circulating oil can prematurely deplete oil additives leading to increased wear and accelerated oil degradation. Particle contamination can also adversely affect fuel economy and harmful emissions to the environment.

Because wear particles are constantly being generated in the lubricating system, constant filtration is necessary to maintain optimal wear protection. The first line of defense has traditionally been the job of full-flow filters. Unfortunately, many full-flow motor oil filters do not remove debris smaller than 20 microns, which enables smaller contaminants to circulate freely through the system. Although damage at five microns has been widely noted, some studies have identified damage from debris as small as two microns.

The removal of ferrous debris is necessary for optimal engine performance and longevity, which is the purpose of magnetic filtration devices.

A New Solution
When evaluating possible solutions for resolving magnetic filtration problems, the first consideration is the necessity that each proposed solution must have been developed with some trade-off in mind. For example, attempts to maintain full-flow of oil and capture ferrous particles at the smaller sizes have historically required a large area of filter media.

The patented differential pressure magnetic filtration process, called "MagDog", offers a bypass filtration solution without many of these drawbacks. We believe that "slow and steady" wins the race.

MagDog
MagDog sits between the engine, or other equipment, and the spin-on oil filter and relies on fundamental hydraulic engineering principles. MagDog contains intake and outflow orifices that pass a small amount of oil through a chamber with strategically placed Neodymium rare earth magnets. These magnets are encased in crosshatched caps which greatly increase the area of surface attraction and concentrates the available magnetic flux for particle separation.

The placement of the device creates a small pressure differential between the engine and the filter inlet. A fractional amount of the oil volume then flows through the chamber at a slow and steady rate, containing the ferrous debris which is exposed to the magnetic separator. The technology ensures the ferrous material remains in the chamber.

The SAE J1858 test conducted by an independent lab (Figure 2) shows the capture patterns for a magnetite micron-introduced test contaminant. It shows the capture and retention of ferrous contaminants of different sizes ranging from two to 40 microns. Although only eight hours are presented, up to 98 percent of the contaminants were captured and retained. The test was designed to simulate a catastrophic amount of engine wear. At a one-percent rate of bypass, a volume of engine oil at about five quarts would enter the bypass chamber approximately nine times (during a typical drive time required to expend a tankful of gas).

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(Click Image to Enlarge)

Figure 2. Independent Test Results

A Powerful Solution
MagDog renders the captured oil nearly immune to viscous and full-flow surges, which are linked to detached particle agglomeration, because the magnetic loading zone is away from these surges. Furthermore, MagDog:

  • utilizes the abundant clearance in the axial direction for easy installation

  • uses filter diameter commonalities to create generic sizing, leading to convenience and lower costs

  • uses existing engine mechanisms, enabling fast installation

  • minimizes space requirements in cramped engine bays

  • provides additional cooling

  • provides easy access to the lubrication system via an included hydraulic port

MagDog overcomes many disadvantages of other contaminant-removal devices, including:

  • eliminating the need to remove the device during oil filter changes

  • minimizing the risk of accidental detachment in high vibration environments such as off-road, racing, etc.

  • eliminating the potential for debris to be reinjected during bypass cold-start operation

  • eliminating magnetic leakage, which utilizes the entire magnetic loading area

  • eliminating the need for special tools, skills and modifications for installation

  • eliminating the risk of clogging and resultant decreased flow

  • eliminating the need to accommodate many filter sizes

  • eliminating problems associated with limited radial clearance

  • eliminating the need to take the bypass lubricant volume from the main flow

  • eliminating the need to orient connections to external hardware

  • eliminating the possibility of magnet vibration shift and resulting particle cluster separation

MagDog provides a solution for the removal and retention of ferromagnetic contamination in automotive and industrial systems. MagDog concentrates on fluid conditions that facilitate the separation and retention of particles by providing a low velocity and surge-protected magnetic area with high-flux magnets. This results in a high gradient magnetic flux in direct contact with oil in a quiet and isolated zone. Therefore, detached particle agglomeration is heavily reduced.

In summary, MagDog offers a number of unique advantages over other magnetic filtration devices. These benefits include high particle retention rate, not affected by cold starts or high-demand surges, easy installation and inspection and low-maintenance requirements.