Why multiple passes on bag filter?

[muns53]

Quick question for the water heater/filtration still w- bag filter folks (like me) -- Why do we do multiple passes through the filter? I've currently got mine set up with a 5-micron bag -- couldn't I just go through it once and right into storage? Why recirculate it back into the water heater & cycle through multiple times?

Thanks in advance for sharing your knowledge!

Happy New Year:cheers:
Eric

[Clay]

it just cleans it better. I stopped doing muti pases once and i started changing Donaldson filters more often. Went back to multi passes and filters lasted longer. I think some stuff gets past the top of the bag is all i can figure and if you cycle it more than a few times, you will eventually get it all out.
I don't cycle it as long as some folks do, 30 minutes with my pump is plenty..about 8-9 passes.

[triplemoutdoors]

Quick question for the water heater/filtration still w- bag filter folks (like me) -- Why do we do multiple passes through the filter? I've currently got mine set up with a 5-micron bag -- couldn't I just go through it once and right into storage? Why recirculate it back into the water heater & cycle through multiple times?

Thanks in advance for sharing your knowledge!

Happy New Year:cheers:
Eric

Eric,
I have asked this question before. It just did not make sense to me so I decided not to do it. Now my oil is cleaner than most and I have not had any issues with one pass. I understand where Clay is coming from on it getting passt the filter bag. I am very careful when putting the filter bag in the housing and make sure it seats properly and the seam is not bunched up.

[Clay]

Eric,
I have asked this question before. It just did not make sense to me so I decided not to do it. Now my oil is cleaner than most and I have not had any issues with one pass. I understand where Clay is coming from on it getting passt the filter bag. I am very careful when putting the filter bag in the housing and make sure it seats properly and the seam is not bunched up.

Your oil is practically brand new right? If i had real good quality oil i would do it in one pass probably.
Try it with some nasty dark oil.

[Tampa450]

because filter bags are only NOMINAL and not ABSOLUTE

http://www.lenntech.com/absolute-nominal-filters.htm

[Clay]

because filter bags are only NOMINAL and not ABSOLUTE

http://www.lenntech.com/absolute-nominal-filters.htm

Well there ya go...

[skyskijason]

Bag filters can be either nominal or absolute. A common bag used for VO is a 5/1 bag. 5 microns nominal and 1 micron absolute.

I have asked this question before and Clay is the only one who has posted much improvement past one pass.

I use a 2 micron (absolute) spin-on filter for 'final filtration' before truck and have well over 10k on the first Donaldson in our V3. My F350 uses a 10mic spin-on about 1/3rd the size of V3 filter and it generally lasts 7-9k miles.

We also have a filter head that matches on-truck VO filter so we can use a filter from truck until it does not flow anymore for pre-filtering. I often throw a fresh filter on truck before a road trip, just because I won't be 'wasting' the useful life of that filter.

My theory is the original econo-masters who decided VO would be great CHEAP fuel were using less expensive nominal-rated bags as well as tee-shirts, blue jeans, etc. Same folks (often greasecar customers!) were happy to get 1000 miles/filter on car... (jus like gc customers today!)

[Marv]

I usually run mine for about 45 minutes to an hour...I figure that's good for 15-20 passes. Not sure if it makes a great difference to run it that long, but it's no extra work to me...just open the right valves and flip the switch.

[Clay]

Bag filters can be either nominal or absolute. A common bag used for VO is a 5/1 bag. 5 microns nominal and 1 micron absolute.

I have asked this question before and Clay is the only one who has posted much improvement past one pass.

I use a 2 micron (absolute) spin-on filter for 'final filtration' before truck and have well over 10k on the first Donaldson in our V3. My F350 uses a 10mic spin-on about 1/3rd the size of V3 filter and it generally lasts 7-9k miles.

We also have a filter head that matches on-truck VO filter so we can use a filter from truck until it does not flow anymore for pre-filtering. I often throw a fresh filter on truck before a road trip, just because I won't be 'wasting' the useful life of that filter.

My theory is the original econo-masters who decided VO would be great CHEAP fuel were using less expensive nominal-rated bags as well as tee-shirts, blue jeans, etc. Same folks (often greasecar customers!) were happy to get 1000 miles/filter on car... (jus like gc customers today!)

This all makes sence but the fact is a dirty filter cleans better than a clean filter so if you run more than once pass you will catch more unless your filter is already pretty dirty and restricted, then one pass would likely be all you need. But like you said, it depends how much life you want to get from a donaldson. 45 minutes is overkill but like Marv said, its just a little electricity, no skin off the back...and it can't hurt anything. I do a min. of 15 minutes and try to do at least 25-30 minutes. If my oil is 110*, that will get me 5-8 passes on a 50 gallon batch.

[sbaker]

Bag filters can be either nominal or absolute. A common bag used for VO is a 5/1 bag. 5 microns nominal and 1 micron absolute.

That doesn't make sense to me. Wouldn't it have to be the other way around? The nominal rating has to be higher than the absolute, by definition, doesn't it?

Whenever I've seen that kind of notation on filter bags it is referring to a double bag. I use 5/1 bags, but they are actually double bags with a 5 micron inside a 1 micron. Those are nominal ratings on the bags I buy. On McMaster, the only absolute rated bags I see are almost $30 each and are made of polypropylene.

Like Clay said, a dirty filter works better than a clean filter and using it should bring the actual filtration closer to the absolute.

[Tampa450]

A common bag used for VO is a 5/1 bag. 5 microns nominal and 1 micron absolute.

That must have been a typo.. I guess?

I honestly never knew that they made any kind of absolute filter bag...but then again I never really looked that hard.

And I agree - as your filter gets dirtier....it captures smaller particles.
(up to a certian point of coarse)