total media face area vs capacity.....

[tdi-rick]

Total media face area vs capacity of contaminent.

You would think that this would be a no-brainer. The greater the surface area of the media, the more contaminents (in grams) that could be retained for a given pressure drop for filters of equal rated efficiencies.
However, as with most things in life, this aint necessarily so...

As an example, I have the specs of two different brand of filters. These aren't straight crosses, yet are sufficiently similar to warrant a discussion.

1. Filter dimensions of 95mm OD x 92mm long.
258 Sq. In. of cellulose media
Beta 2=25
21 grams capacity

2. Filter dimensions of 94mm OD x 108.5mm long.
312 Sq. In. of cellulose media
Beta 2=25
9.52 grams capacity

Please discuss.

 

[tdi-rick]

Surface vs Depth filtration

OK, I'm assuming most/all cellulose medias fall into the surface filtration category. In this category, all things being equal, the greater the face area, the greater capacity and the longer the life for a given efficiency.

Can some thicker/less heavily pressed (0.030"+) medias be considered to have a degree of depth filtration ?

Is this how the first filter above has a greater capacity ?

 

[Ugly3]

Figures don't lie but liars can fingure.

 

[Jim Allen]

The thought comes to mind also that one or the other spec is a misprint or an error. They seem pretty far apart.

 

[Filter guy]

Depends...

tdi-rick...are these two comparisons you posted from the same or different filter manufacturers?

 

[Gary Allan]

tdi-rick (and I'd like to get Mel's take on this too) ..do you have a weight figure for the media?

My only thought here is that although ^" are not that far off ..that the construction can be quite different. There's also a 3rd dimensional component besides the weight factor.

 

[tdi-rick]

quote:

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are these two comparisons you posted from the same or different filter manufacturers?

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Different manufacturers. Sorry I didn't make this clear enough.

quote:

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..do you have a weight figure for the media?

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No Gary. I have the in-house spec sheet for the first one, and it doesn't mention it either.

As I mentioned in the Donaldson Synteq thread, A Donaldson rep cautioned me on paying too much attention to media face area. He said they would quote a capacity figure above a media figure. ie, it was more appropriate.

 

[tdi-rick]

just an observation, I've noticed that of the specs I've accumulated, Donaldson, Fleetguard and Mann-Hummel tend to have a greater dirt holding capacity for a given range of filter size's/efficiencies.

 

[kenw]

i think what you guys are looking for is loading factor. It is a combination of depth and density.

technically speaking, surface area isn't just the flat faces that we typically measure. It's the area available to stop and hold stuff and may actually be buried "inside" the media. you can't measure effective surface area with a ruler.

 

[tdi-rick]

Kenw, that's the question I'm asking.
I come from the air conditioning industry, and most of our medias fall into the depth filtration category. Some non-woven medias even use a graduated density from the air on to air off sides.
In simplistic terms, wire gauze is the easiest example of a surface retention media. It is a simple go-no go hole.
It appears that the medias I've branded as staight surface retention medias, ie, most cellulose based types, regardless of fluid(gas) being filtered have a degree of being able to be loaded through their depth.

 

[kenw]

yes, and that's why it is important that the media type and loading factor be included in the effectiveness calculations. Basically that's what your numbers show.

(i did a stint in the AC business myself, albeit short, water sourced heat pumps to be exact)

Obviously in the cases you presented in the opening post have significantly different loading factors, related to media depth and density/porosity, etc.

You could say that #1 has a loading factor of 0.08g/sq in, while #2 has 0.03g/sq in.

If the media is the same, sure, simple surface area can be used as a comparator. But between brands it rarely is the same so simple surface measurements can be very misleading.