A new way of applying old technology to solve a current problem often falls on deaf ears. That’s because when people hear of a solution using technology they heard about decades ago, they usually close their minds. They assume they already know everything about the old technology, including the limitations that kept it from producing significant benefits.
Such is the case with magnetic filtration technology. People may jump to the conclusion that this technology involves magnets placed around a filter canister or in a reservoir. The opinion may be that magnetic filtration has little effect because ferrous particles attracted to a magnet are generally found only in new systems during a break-in period. They may also deduce that particles attracted to a magnet can quickly find their way back into the main body of fluid when the next flow surge occurs.
The new approach
These arguments hold true for conventional methods of magnetic filtration. However, Magnom Inc., Chicago, introduced a new method of applying magnetic filtration technology that removes contaminants from the flow stream and does not restrict flow. Furthermore, Magnom’s patented technology is not intended to replace media type filtration but to enhance it.
The technology developed by Magnom removes sub-micron and larger sized contaminants from hydraulic fluid using a combination of magnets and specially formed steel plates to collect the ferrous particles — often considered the most damaging contaminants present in most hydraulic systems.
Housed around central magnets, the steel plates transmit magnetic fields that attract ferrous and other magnetically sensitive particles into collection zones between the plates. The plates are arranged as positive-negative pairs, and because opposite charges attract, positively charged particles are drawn into negatively charged collection zones formed between pairs of plates. Likewise, negatively charged particles are drawn into positively charged collection zones. Because ferrous particles tend to hold a positive or negative charge, they will be attracted either to a negative or positive collection zone.
Furthermore, flow pulses and surges — inherent to most hydraulic systems — do not dislodge the particles from the collection zones. This is because trapped particles are not in the main stream of fluid flow. Moreover, magnetic force (opposite charges) holds particles within the collection zones. For the particles to exit the collection zones, they would have to overcome the magnetic force of a pair of likecharged plates. So in essence, the particles are held in place by the attraction of opposite charges and the repulsive force of like charges.
We have seen the enemy
The hard, small particles of ferrous metals typically found in hydraulic systems are too small to be trapped by even the finest media-type filters. Furthermore, these particles typically have sharp edges and are dense, so they can tear the media when they pass through the filter, shortening media life. And because they are hard, sharp, and dense, they can damage and cause premature wear of other components as well.
These particles are not always ferrous in nature. They may be brass, aluminum, or stainless steel particles that have become attached to a ferrous particle, or they may even have become charged, and, therefore, removed by the magnetic fields. Removing these contaminants interrupts the chain reaction of wear to extend the life of components within the system and improve reliability.
Unlike media filters, Magnom cores do not create an increasing high pressure drop as more contamination is collected. This is because particles collect in areas removed from flow paths. In fact, pressure drop is not a factor when applying Magnom cores. The cores are sized so that the flow area around all the steel plates equals or exceeds the flow area of inlet and outlet ports.
Unlike media-type filters, magnetic separation technology occurs independent of particle size, so even submicronic particles can be removed without expensive filter elements that create substantial pressure drop. If they are not removed, they can pass through filter elements and recirculate through the system again — causing wear and damage each time they do.
As noted already, Magnom cores should not be used to replace conventional, media type filters. Instead, they improve system filtration and extend the life of media filters. They do this by trapping particles that would otherwise collect in filter elements, and they remove the hardest, most damaging particles from the flow stream. And unlike ultra-fine media filters, electrostatic fluid cleaners, and centrifuges, they provide a simple and inexpensive technique to maintain higher fluid cleanliness.
This article originally appeared in print as "New Tricks for an Old Dog," in the March 2008 issue.