A little of what I know about Magnetic Filtration
Hello,
I ran across this thread while searching the web for the word Filtermag. I am impressed with the size the thead has has grown to, and at the large amount of information, opinion, speculation, experience, etc. I have not read every post, but I read many of them.
As a point of introduction, I am the Vice President of Engineering for a company than manufactures magnetic oil filtration products. The company has been in business since 1987, originally making magnetic inline filters for hydraulic equipment. I have been with the company since 1993, when they switched over to the manufacture of automotive products. We do not sell in Australia, and I am not going to mention my companie's name. I am trying to find the balance that exists between trying to establish my credibility here, and appearing to be trying to promote my companies product.
Hopefully, I have found that balance, and can offer you some useful information to aid your decision making, and save you effort, money, disappointment and frustration.
I will try to keep this short, limited to a few short facts.
Magnets on the bottom of a filter are totally ineffective unless the filter is clogged (and not working), because by design, oil does not flow in the bottom of the filter.
https://www.aulro.com/afvb/images/im...2012/08/37.jpg
Flat magnets on the side of a filter, are mostly ineffective, because most of the magnet is not in contact with the filter's curved surface. Not only does magnetism fall of very quickly with distance, but magnet - air gap - steel makes an effective magnetic shield.
Magnets of moderate low to moderate strength in general, will not trap significant material when installed on the outside of a filter, because the steel canister provides some shielding and interferes with the lines of flux, dissipating the effective strength of the magnet. If a magnet needs to be fastened to the canister with some sort of strap, then the magnet is certainly too weak to be very effective
Thicker magnets are preferred to thinner magnets, because the effective depth of penetration is proportional to the magnets' thickness. For a Neodymium Iron Boron magnet (the strongest type) this thickness should exceed 5mm.
The magnets' shape, should approximate the curvature of the side of the canister. As I said, I was looking on the web for Filtermag. To Filtermag's credit, there unit does curve. It is a good unit, but in my opinion, is far too expensive.
Oil Filters are usually made to filter materials larger than 20 microns. As they get used, their filtration improves, because as debris is added to the filter pleats, the clog, and begin to reduce the effective size of the pores.
Of course once too much clogging has occured, oil flow is diminished, an the filter most be replaced.
Particles as small as 2 microns, contribute to engine wear, according to the Society of Automotive Engineers. Effective oil filter magnets, remove particles smaller than one micron.
Neodymium Boron Iron magnets, are the only truly effective magnet type, to accomplish this level of filtration available at the present time.
Good magnetic filters, can remove non magnetic materials through two methods. The first method a trapping of particles between magnetic particles mechanically. The second is due to paramagnetism, where non-magnetic materials, like aluminium and copper, become magnetic when inside a strong magnetic field.
Not all magnets are suitable (even NBI magnets), because the magnet strength can be reduced by elevated temperatures.
Becuase good oil filter magnets remove large and small particles, magnetic and non-magnetic, the filter material flow oil better longer.
Magnetic drain plugs can capture some material, but is too far away from most of the oil to capture most of it before is gets to the filter.
One poster said to the effect, that the oil moves too quickly for a magnet to capture particles. Another posted mentioned using an oil filter cutter to inspect the insides. This second poster is on the right path. Inspecting an oil filter this way, instantly disproves to 'too high velocity" theory.
A bit of caution: Cutting a filter with a saw or grinder, will ruin the evidence through contamation. A type of cutter which works by shear or groove rolling (like a pipe cutter) is needed. Be very careful, canister sides can be very sharp, one of my technicians received 5 stiches to prove it.
I hope you found the above information credible and useful, enjoy your landrovers!