- Joined
- Aug 28, 2024
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- 5
Some background on me, I have been a filter designer for over 40 years. Primarily designing filters for aerospace applications. Mainly aerospace hydraulic applications although I did design 4 air filters for the B2 Stealth Bomber back in the 80's. I was also the Chairman of the SAE A6C1 Aerospace Hydraulics Filtration and Contaminaion for a number of years. It was at one of our SAE meetings that the US Army approched our group and mentioned that it has been having horrible hydraulic pump failures on their Black Hawk helicopters. There are three hydraulic pumps on each Black Hawk and every year at Fort Rucker in Alabama, they had to change out around 300 pumps because of the bad results they were getting from fully qualified glass fiber filter elements. Now these elements had to pass the most stringent testing of MIL-F-8815 which is an expensive test to run but the Army still suffered from a huge amount of failures due to a highly contaminated hydraulic system. This was also the case with the Apache and Chinook. The Army had some really smart guys however down at Redstone Arsenal in Alabama where the Army Engineering Directorate is stationed. They looked at MIL-F-8815 and realized basically that this is a static flow test. You flow the fluid through the element at a constant flow rate and slowly add test dust until the element reaches its terminal differential pressure. Real life is not like this. The flow in real life is dynamic. Everytime the pilot moves the stick or the pedals or any control in the hydraulic system, the flow changes. The Army instrumented one of their helicopters with flow meters, temperature gauges and accelerometers, anything to try and see an accurate picture of what was happenening during flight with the hydraulic filters. They then designed a filter test they called DFE, Dynamic Filtration Efficiency which raised or lowered the flow rate every 5 minutes during the multipass test. So a test running at 20 gpm went down to 15 gpm after 5 minutes and then 5 min later, it went back up to 20 gpm. What they found horrified them, the qualified filters they had been using for years simply broke down and allowed the trapped contaminate to go back into the system. This was the failure issue with these elements. The Army came to our SAE meeting and asked the aerospace filter companies present if they had a media that was resistant to this dynamic failure. Well, at the time, I worked for a British filter company that had no business with the US Army (but really wanted to get into that business). We had been using a material called sintered metal fiber. It was a random mat of 316L stainless steel fibers all sintered together into a pleatable filter media. This stainless filter media ranged from 3 micron up to 100 micron in filtration rating. Since it was 100% stainless steel, it could take any temperature that stainless could handle, any chemicals stainless could handle and it could be welded or assembled by epoxy into a filter element. The only problem with metal fiber is that it is more EXPENSIVE than glass fiber media. We talked to the Army and they had us manufacture a series of metal fiber elements for the Apache and Black Hawk and in order to put them on a helicopter we had to get them qualified. This proved to be fairly easy as the metal fiber media was much stronger than the glass fiber and had no media migration or fibers coming off the element media and going into the system. Once qualified, the Army placed these elements on the Apache and Black Hawk helicopters and performed 36,000 flight hours. What they found was a 10X reduction in maintenance. They went from losing 300 pumps the first year to 25 the next year and then none the third year.
Now why have I put all this text into a forum that has to do with automobile filters? Well, I thought that if this material does so well in aerospace, lets try it on a car. So I purchased a spin on housing from System1Filters for my 2018 Nissan Rogue Hybrid and had a metal fiber element made by one of my customers. The result, well so far I have driven 50K miles with the same filter element. After one year, I changed out the Mobil 1 oil since the acid number started to creep up but have not removed the filter. I send a fluid sample out to Wearcheck labs in Cary, NC every 6,000 miles to see how things are doing. New Mobil 1 is very dirty. It is around ISO 4406 Code 23/21/18. My car has stayed around 18/16/13 throughout the test which is cleaner than new oil. Actually, the last test I did a few weeks go the level dropped a little more which means that the smaller holes in the filter are getting plugged but the filter has not gone into bypass as metal fiber has a huge dirt capacity. When it does reach the time I want to change it out, I will send the element to Carolina Filters in Sumter, SC for cleaning and return it back to the car. Metal fiber is cleanable and reusable and can be completely recycled as it is 100% SST.
Anyway, below is a photo of metal fiber media showing the sinter bonds on each fiber. There are no glues or binders in this media and it has a super high porosity of around 80%. I used to work for Bekaert Corporation who makes this media but no longer do.
Now why have I put all this text into a forum that has to do with automobile filters? Well, I thought that if this material does so well in aerospace, lets try it on a car. So I purchased a spin on housing from System1Filters for my 2018 Nissan Rogue Hybrid and had a metal fiber element made by one of my customers. The result, well so far I have driven 50K miles with the same filter element. After one year, I changed out the Mobil 1 oil since the acid number started to creep up but have not removed the filter. I send a fluid sample out to Wearcheck labs in Cary, NC every 6,000 miles to see how things are doing. New Mobil 1 is very dirty. It is around ISO 4406 Code 23/21/18. My car has stayed around 18/16/13 throughout the test which is cleaner than new oil. Actually, the last test I did a few weeks go the level dropped a little more which means that the smaller holes in the filter are getting plugged but the filter has not gone into bypass as metal fiber has a huge dirt capacity. When it does reach the time I want to change it out, I will send the element to Carolina Filters in Sumter, SC for cleaning and return it back to the car. Metal fiber is cleanable and reusable and can be completely recycled as it is 100% SST.
Anyway, below is a photo of metal fiber media showing the sinter bonds on each fiber. There are no glues or binders in this media and it has a super high porosity of around 80%. I used to work for Bekaert Corporation who makes this media but no longer do.
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