Filter ratings: what they mean (and don't mean)

[R and D Nikkel]

I posted the same information in a longer thread but thought I would put it under its own title to make it easier for people to find. The question I was trying to answer was how efficient these filters are right away, since our brand new filters seemed to be passing a lot of dust. This is what I found:

Straight out of the box, the 80/20 blend filters (the Wynn 9L300BL or the Camfil Farr 211736-1 HemiPleat) only capture about 50% of the 1 micron dust, and less than 30% of the .5 micron dust. This link on the Wynn site http://www.wynnenv.com/filter_efficiency.htm shows the actual results when the filters are tested when brand new, and I have received information from Camfil Farr about their filters which show very similar results. This means that until the filters are used or pre-seasoned, they pass a LOT of the very dangerous dust. The rating given to them is MERV 10 (despite what the Camfil Farr brochure says about them being MERV 12 - that is old data). This is a good link that helps to understand what a MERV rating means: http://allergyclean.com/article-understandingmerv.htm

So then, why do they claim 99.99% efficiency at 0.5 microns as Wynn does on the link above and Camfil Farr does here http://www.farrapc.com/literature/pr.../hemipleat.pdf ? This last link gives the answer in the added word "by weight". This is part of the old ASHRAE 52.1 test. I quote from a Camfil Farr Technical Service Bulletin: "A 5-micron size particle has a relative weight of 125. 125 1-micron size particles have a relative weight of 125. If 126 particles (one 5-micron & 125 1-micron particles) are fed to this filter, the one 5-micron size particle is captured and the 125 1-micron size particles pass through. This filter may be deemed efficient at removing 50% contaminant by weight. However, the efficiency of this filter by particle count is 1/126 of 0.088% or less than 1%." (Italics added) So the newer test checks actual particles while the older one tests weight. So when using this test, it can look like most dust is being caught when actually most of the smallest (more worrisome) dust is passing through but almost all of the larger, heavier particles are being caught. This is still a very common way of describing the capacity of filters in the industry, but then people in the industry should know what it really means. The rest of us are mislead because we don't understand what it means and expect it to mean 99.99% of the particles down to 0.5 microns (and the Wynn site doesn't even use the words "by weight").

Now this is BRAND NEW. The Wynn links shows (and Camfil Farr has sent me the testing on theirs) that as the filters are loaded their efficiency increases. The test puts 30 gms of material into the filter (doesn't seem to depend on size of filter and they don't say what size particles are in that 30 gms) initially, and then repeats that 4 more times without cleaning the filters. As there is more material in the filters, they work better. Neither give data on the increase in resistance, and therefore the decrease in air flow, due to the loading. But this is what is happening in practice in our shops, and I know that our old filters did keep the air really clean as tested by the Dylos.

In fact, these companies (at least Camfil Farr) actually sell "precoat material" to season your filters with before you use them. This dust has an average size of 40 microns, and the instructions say: "If the material to be collected is small in particle size (predominantly under 5 microns), oily, sticky or otherwise unfriendly to the cartridge, longer cartridge life and higher initial efficiency can be achieved by pre-coating the cartridges." The idea is to coat the filters with larger particles that trap the smaller ones and, from the sounds of it, make it easier to clean the smaller particles out.

It finally got cold enough that we had to start using the filters. Within a couple of hours using the grinder the number of 1 micron particles coming out of the filter was between 3500 and 4500 as opposed to the 12,000 right at the beginning. Still far from good, but a whole pile better. And they will continue to get better as we get more dust into them. We don't have the ability to test to see increase in resistance or decrease in air flow due to the loading, but lots of air is still moving for sure. It will be interesting to see what comes through after we clean them the first time - if they stay relatively good or go back to passing more fine dust again.

So the practical application of all this? Brand new filters of this type still spew a lot of fine dust for a little while. So wear your masks for a while when starting new filters and be prepared to do a good shop clean after they get seasoned enough to trap the smaller particles. Or go the extra bucks and buy the filters labelled MERV 15 (Wynn 9L300NANO) or MERV 16 (Camfil Farr PTU-Poly-Tech Ultra High Efficiency) that really do trap 95% plus of the 1 micron sized dust when they are right out of the box. And look forward to spring when you can vent outside again.

 

[Dog House]

Filter ratings: what they mean (and don't mean)

Thank you R & D for bringing this information forward. This is really important to know!

Fred Alexander

 

[Don01]

Thank you for the update.

In fact, these companies (at least Camfil Farr) actually sell "precoat material" to season your filters with before you use them. This dust has an average size of 40 microns, and the instructions say: "If the material to be collected is small in particle size (predominantly under 5 microns), oily, sticky or otherwise unfriendly to the cartridge, longer cartridge life and higher initial efficiency can be achieved by pre-coating the cartridges." The idea is to coat the filters with larger particles that trap the smaller ones and, from the sounds of it, make it easier to clean the smaller particles out.

In all of the reading I have done, the term seasoning has been used but sparingly. The absolute value of the cake or "pre clog" as you put it has been lost on the woodworking industry. It is absolutely critical for good efficiency and long term filter life, just like the swimming pool filter. Especially in cases like your where your percentage of fine dust still appears to be greater than 15%.
People still use these stupid bags. Where in industry do you find bags - in bag houses away from the workers with compressed air puling regularly to clean them.
Everytime the bag collapses on the single stage DC, most of the cakes falls off.

Now the canister makers put a crank on some paddles so after each session you can knock the most valuable dust off the media.

Rick Wynn told me that the spun bond fibres were much slicker and pore sizes more uniform than the old paper style filters. The output from you sander and grinder is likey more even is size than froma table saw.
So your .6 micron and larger dust is just blowing on through until that cake is established.

I stand with my original suggestion that you recycle coarser dust through your system. Perhaps the waste material as it is a bit heavier. Anything but fresh grinder/sander output.
Trouble is our cyclones are going to separate the heavier material. So even a significant amount of your waste material might not make it to the elements, but worth a try as you already have it. We caould start a collection aronf Edmonton
You want lots of 10-1 micron dust on those elements first.

Don

 

[R and D Nikkel]

I found it intersting that their precoat material is actually 30 - 50 microns, averaging 40. That is a lot larger than I would have expected it to be. The instructions for using it are to put 1 - 2 lbs into each filter with compressed air (not thinking of a cyclone system), then clean with 2 pulses (which is what the commercial ones do - large blasts of air backwards through the filters) and then put 1 - 2 lbs more in. My impression in talking with the dust guy was that a lot of this stuff will stick in the media of the filter and not come out with cleaning, and that increases the efficiency of the filter (and increasing the resistance, but they don't talk about that!). I agree that using larger particles first would be the best thing, now that I know what I know. How much that will help after we have used them for a couple of days??? That I don't know, though it won't hurt. And how do we get the larger particles through the cyclone? That I also don't know.
Seems totally backwards to everything we have heard about filters - put big dust into them before you use them. But that really is what the company recommends. Or else buy the more expensive but finer filters. However, they don't tell you how much more resistance you get from them (and therefore decreased airflow) and how much faster that reduces the life of the filter. For most people who do woodworking as a hobby, that is probably the better way to go. For people who use the filters more, if the life span is significantly decreased, that would be more of a consideration.

 

[Don01]

Cake is Good!

Cake is Good!

I found it intersting that their precoat material is actually 30 - 50 microns, averaging 40. That is a lot larger than I would have expected it to be. The instructions for using it are to put 1 - 2 lbs into each filter with compressed air (not thinking of a cyclone system), then clean with 2 pulses (which is what the commercial ones do - large blasts of air backwards through the filters) and then put 1 - 2 lbs more in.

That is "baghouse" thinking. Farr actually have an element with an internal cone that actually helps distribute the cleaning blast across the surface of the element.

My impression in talking with the dust guy was that a lot of this stuff will stick in the media of the filter and not come out with cleaning, and that increases the efficiency of the filter (and increasing the resistance, but they don't talk about that!). I agree that using larger particles first would be the best thing, now that I know what I know.

Certainly big chunks bridging to trap smaller chunks which bridge to trap even smaller chunks until the cake is very thick (think microns), and performance drops. You would need a differential pressure indicator to really know. I think this is Richard Brown's area of expertise. If the 40 micron cake down to probably 20 micron, survives the cleaning, that is good. Relative to the pore size, those 40 micron fibres are still going to create a web of fibres that will continue to trap progressively smaller particles. But, you want to hit the 40 with 30 then 20 then 10 then 5 and so on. Not hit 40 with 5. The idea of particles resisting cleaning seems to go against Rick Wynn's comments to me on the value of spun bond media - slicker, easier to clean.

How much that will help after we have used them for a couple of days??? That I don't know, though it won't hurt.

From you reports, most is flowing through the filters, so probably not much concern there.

And how do we get the larger particles through the cyclone? That I also don't know

.

Possibly plug the waste bin at the bottom of the cone and do a controlled overflow.

Seems totally backwards to everything we have heard about filters - put big dust into them before you use them. But that really is what the company recommends.

Not really. This is the way filters work. Even the old fibreglass furnace elements were not doing a good job until they "looked" dirty, but that is when we changed them. Lightly mist your furnace filters with vegetable oil and see what happens

Or else buy the more expensive but finer filters. However, they don't tell you how much more resistance you get from them (and therefore decreased airflow) and how much faster that reduces the life of the filter./QUOTE]

Again consider that you already have .5 micron nominal element, but the dust you are producing is obviously finer than that. In theory, the flow should stay as along as the cake is sound.

Cake is good! Clean elements are bad.

For most people who do woodworking as a hobby, that is probably the better way to go. For people who use the filters more, if the life span is significantly decreased, that would be more of a consideration.

I am continually surprised at how many woodworkers treat dust collection as a house keeping item rather that a health item. How many people on WW forums discount Bill Pentz as to complicated, costly etc. I have yet to read any critique of his science. How much crap there is still on the market, that people believe so they buy. No standards, it is disgusting.

People are use to disposing of automobile air and oil filters. The service those elements see is off the chart compared to our dust collection. We can manage our filtration, maximize performance, minimize cost but there is no one guiding us.

You have learned more in one week than this hobby has in a decade.

But yes, getting the media optimized as quickly as possible in our world is paramount. We do not work in a bag house environment. We need those filters seasoned and ready to go in short order.

You, I and a few others on this forum have a Dylos. Most don't. If you can't see it, how can it be a problem?


Don

 

[R and D Nikkel]

Cake is good! Clean elements are bad.

I think there is a line somewhere in here because too much cake decreases the air flow and ups the back pressure to the point it affects collecting the dust at the source. Do we know this? Yes, because earlier this year we blew out the insulated ducting we had going between the cyclone and our old filters. There was that much back pressure. And when you can notice the difference in suction at the machine, as we can when the filters are getting too full, you know there is a difference from the back pressure. This is the reason we decided to change over to a system where we can clean the filters better and more easily, and therefore more often. It will be interesting to see what kind of dust we get through after one clean/two cleans etc.

But, you want to hit the 40 with 30 then 20 then 10 then 5 and so on. Not hit 40 with 5.

I can see that being ideal, but I don't know that even the big companies do things like that. They didn't tell me that they had different precoat products and when I asked the guy the size of the material he had to do a bunch of checking to figure it out so it wasn't something they had discussed a lot probably. These Hemipleats are made especially so that they are easier to clean as well. I see the cleaning as being a very important part of the whole system because without the cleaning, the air flow is so choked the filters can't work well. It is walking that fine line. I think the ideal would probably be the MERV 16 filters kept very clean. How practical that is????

 

[McRabbet]

Excellent thread, folks. Thanks for posting this!

 

[R and D Nikkel]

I've been reading the testing procedure more carefully and have found out some more interesting information. I'm looking at the chart on the Wynn site here http://www.wynnenv.com/filter_efficiency.htm . The initial testing is with a totally clean filter. The first "loading" is 30 gms or and increase in 0.04 WG (inches of water gauge) of resistance, whichever comes first. The second loading is till you get an increase in resistance to 25% of the "manufacturer's recommended final pressure drop". The third loading is to 50%, the fourth to 75% and the fifth to 100% of the "manufatcturer's recommended final pressure drop". In other words, the final loading on this chart is when the filter is a clogged as the manufacturer ever wants it to be! I have the same kind of chart on the Camfil Farr filter and it looks to be slightly better, but then that would depend on what they recommend the "final pressure drop" point to be. On the Camfil Farr one, that is 3 WG. I think this would mean 3" difference in measured static pressure, but I am not sure on that. I haven't tested the pressure in our system, so I don't know the percentage drop that would make in the amount of air moving. Maybe some of you who have that knowledge could help figure out how significant a drop that is. The Wynn site doesn't state how much it accepts as a "final pressure drop".

 

[bababrown]

R and D Nikkel

R and D Nikkel

I think the 3" water column is the correct interpretation and I think Wynn's number will be close to that. Note that 118 feet per minute is the minimum face velocity allowed in the ASHRAE 52.2 test. If you take the 12.75" outside diameter of the filter and the 34" height you get 9.458 square feet of "face". They must test with the air blowing from the outside. Multiply that by the 118 feet per minute and you get 1116 cubic feet per minute. Note how well that compares with Wynn's number of over 1100 CFM. That is for one filter whereas we run two filters at just about 500 CFM each ( 1000 CFM total) at the most. Because pressure builds with the square of velocity or flow rate the test should show almost 5 times the pressure drop we would see in our systems. It is (1116/500)^2 = 4.98 times. So the 3" stated should be about 0.6" the way we run the filters.
This is interesting stuff. If you read up on ASRAE 52.2 a MERV 10 filter doesn't even include the data for the four bins from 0.3 to 1 um. And those percentages don't get high until we get up to MERV 15 or 16.
Try this URL for info on ASHRAE 52.2
http://www.nafahq.org/LibaryFiles/Articles/Article006.htm
bababrown

 

[R and D Nikkel]

Bababrown,
The test results I have from Camfill Farr are for a test run at 675 CFM air flow. This is what shows similar (though better) results as what the Wynn link I posted does. The report has NA (not applicable) by the Nominal Face Velocity in fmp. I believe this is probably because they use a standard size of filter in their tests. When using real filters, they have to use CFM to account for the size of the filter. These are official ASHRAE test results, so they have to meet the velocity ratings somehow. And the 675 CFM is probably pretty close to what we will be putting through our two filters if our system has good air flow on our CV 1800 which will put through 1442 CFM maximum.
I can't figure out how Wynn gets the 1100 CFM from 118 fmp. The question I have is are they talking "face" area, or total media surface area, which for the Wynn filter is 300 ft. The Camfill Farr one I have is from a filter with a 12.75" OD, 8.38" ID (same as the Wynn), but this one was only 27" tall. They list the Estimated Gross Media Area as 140 square feet. (The Hemipleat design uses a lot less surface area and claims the same or better filtration effects because of the extra air flow it allows. At least that is my interpretation of their claims.) Dividing the CFM by either the "face" area or the media surface area gives rates that are far below the minimum 118, but these are official ASHRAE tests, so there must be another factor in there somewhere that we are not taking into account.
One thing I did see though, was the total weight of the dust needed to get to the fifth loading, or 100% of the final pressure drop. It was 2218 gms, or almost 5 lbs of dust. It took 1147 gms, or just over 2 1/2 lbs, to get to the 50% area. So that is a lot of dust and should reassure us somewhat that we won't get to that level very quickly.

 

[bababrown]

R and D Nikkel,
Wynn is using the face area. It's just PIx(12.75/12)x(34/12) = 9.46 sq ft. Then multiply by 118 to get 1116 CFM. With a 27" tall filter one would get 886 CFM at 118 fpm. Apparently CAMFIL FARR tested at a lower air velocity. I'm wondering if they tested using the older ASHRAE 52.1 standard. (?) That is a weight based standard like you described.
bababrown

 

[R and D Nikkel]

No, the information I have is the official ASHRAE Standard 52.2 - 1999 Test Report and is signed from the lab that did the testing. So I still think there is probably something else we don't know here. (LOTS I don't know!!)

 

[reprosser]

Lots of interesting data....totally confused now.

I have not yet finished installing my Clear Vue with Wynn 9L300BL filters.

Should I do something with the filters before hooking everything up, or will just running the unit "dirty" up the filters automatically?

What are the correct steps?

 

[R and D Nikkel]

Not sure what is best. I think everyone just puts them in and uses them, but I would suggest to wear your mask for the first while when they are putting through lots of dust. Way less than the old "dust pumps", but still more than enough to smell. We have been using ours for 1 1/2 weeks now and the readings have gone down substantially. We'll report back when we know more.

 

[Ed Haney]

I thought I had a dust leak?

I thought I had a dust leak?

This is interesting and timely. I just posted about my new CV installation and my "dust leak" I've been trying to find. I was coming to the conclusion that my filters may be passing the dust.

As I wrote elsewhere today. BEFORE running ANY dust through my system my shop was reading about 1200 or so on my 0.5um Dylos. I would turn on the CV and it would drop the dust count to 200 or less. So I knew my system was "working".

Then I started using my CV to collect sawdust. I ran a very small amount of material through my bandsaw and counts went up to about 4000 and then dropped quickly as I stopped sawing and let the CV continue to run to filter the air in my shop. (I only have 8'x20'x9'h shop = 1440 cubic feet, so the CV can turn over the air about every 70 seconds in theory.)

Then I moved to my Jet 16-32 drum sander with 80 grit paper to sand some gaboon ebony. The collector pulled hard enough to suck the belt conveyor up to the drum! The sanding produced fine back ebony dust and my counts immediately went from about 1200 to about 70,000. Needless to say I put on my P100s dust mask.

I did find 3 leaks on the outlet to the filters and fixed them. Then I took the collection bin completely off the CV and ran the unit while producing NO additional dust. My counts immediately jumped up to 40,000 with no additional dust feeding the system. I am wondering if dust in the filters are continuing to be blown through?

I though about running some mahogany dust I collected from my table saw via a Dust Deputy through the CV. I a few pounds of it and it is much more course than the ebony dust.

What to do to get my counts down? I got this for my health and expected to have counts below 300 on my Dylos.

Ed

 

[R and D Nikkel]

Ed, Is your Dylos a 1 micron or a .5 micron? We were reading 12,000 plus on the 1 micron dylos when sanding maple and pine. When you took the dust bin off, I assume you blocked the bottom of the cyclone. Other wise you would have been sucking air from the room up the cyclone and that could have affected your counts??
I checked counts today and they were often less than 2000 coming right out of the filters, so using them does decrease the numbers. Remember we are a small business so use the filters a few hours per day.
We do have some precoat coming, but it got cold enough (-25C, -10 F) that we HAD to start using the filters first. When we get it, our plan is to record the numbers we are getting, do a clean of the filters, use the precoat according to directions and then see what kind of numbers we get after that. The main goal of the precoat, as I understand it, is to help "season" (ie. preclog) the filters with larger material. That material then traps the smaller stuff, but lets that small stuff get cleaned out easier. And I don't know how well or how quickly it works to get the numbers down, or how our using the filters prior to seasoning them will affect it. I guess we'll see. We'll report back.
By the way, I got the load test results on the Camfil Farr MERV 16 filters. They start out actually getting 99% plus of the 1 micron stuff and 98% plus of the .5 micron stuff. But, they take less than 1/4 of the amount of dust to get the same increase in resistance in the filters. ie. they plug up 4 x as fast. That would be the best thing to get the numbers down the fastest, but you would be cleaning them a lot more.
I'll try to put pictures of our set up in the gallery once clean them to show how we now have it set up. We'll see how it works first.

 

[Ed Haney]

My Dylos is 0.5 micron.

With the collection bin removed and NO dust coming up through the bottom of the cyclone and NO dust being made (all machines and activity stopped) the counts on the Dylos quickly rise from 1500 in the room to 40,000 by just turning on the CV. This rise happens in less than a minute. (And it takes several hours for the room to settle down by itself - meaning I must wear a dust mask for hours or not be in the shop!!). So the pre-captured dust must be being pushed through the filters. This is the best reason that I come up with. I did not think I was buying a dust blower.

I am going to get some table saw mahogany and pine dust from my Dust Deputy and suck that through the cyclone today and see if that helps or not. I have about 1/2 of a 5 gallon pale of it to try. I'll put an new bag on in the collection bin.

As I stated earlier, this is really disappointing. I would have bought the Nanos if I had know there was a significant difference. I even called Wynn to discuss it BEFORE I touched or installed the standard filters that comes with the CV. Or with Onieda selling true HEPAs now that would have been an option. I just hope these filters start cleaning the air up the way they did before being used for fine dust collection.

Ed

 

[R and D Nikkel]

Ed,
Maybe you want to clean your filters first. Blow them out from the outside and vacuum the inside. Get rid of that really fine stuff as best you can. Not sure if it will help a lot, but it sure can't hurt.
The problem with getting things like HEPA filters is that they clog up so badly with so little dust compared to the other filters. It is finding that line. But again, what are you doing? Lots of sanding on really hard wood = lots of really fine dust. Planeing a lot of pine, not as much fine dust.

 

[Don01]

Filtration - What we don't know

Filtration - What we don't know

This information raises some real concerns.
Some of the discussions out on the net refer to the advantage of introducing chaos into a particulate bearing gas stream to aid in the of the particulate matter. Much like a industrial exhaust stack or even your vehicle exhaust, as soon as the gas stream leaves the confines of the pipe or stack, it looses momentum, direction and adopts a random, chaotic flow pattern. In this condition, the gas component mixes with the environment and the particulate begins to settle out.

This bit of physics comes into play when our single stage 1 micron felt bag of some 30-50 square feet is replaced with a 274 sq ft pleated cartridge (Wynn 35a 80/20 blend), the exit velocity of the gas drops, the direction of flow inside the canister becomes more chaotic as there are more places to flow to with less velocity.

This all makes good sense to me.

In 2008 started inquiring about the differences between paper and spunbond media. I could not get my head around the fact that having more air whizzing through a smaller surface area .5 micron rated element was a good thing.

I questioned Rick Wynn of Wynn Environmental ands Daniel Moscardini of Maddocks Group on the relative benefit of the lower surface area. I tried to open a discussion on this in this thread, http://www.clearvuecyclones.com/Bullentin/showthread.php?t=1024&highlight=Wynn, but the discussion did not go to far.

Discussion with Wynn Environmental

Don Burch wrote:
> With respect to the 35A100SBOL (Spunbond) and the 35A274BLOL (Paper)
>
> I am having difficulty understanding the positive effect of reducing the
> available surface area by 174 sq feet.
> I can see where some of the loss in flow could be offset by the larger
> pore size, but that isn't what we want is it?
> Please clarify.
> Given that the area above the element is usually waste space, can you
> make either element taller - 36"
>
> Thank you,
> Don Burch
> Fort Saskatchewan, Alberta.
>

-------- Original Message --------
Subject:
Re: Filter Element Surface Area
Date:
Mon, 28 Jan 2008 13:31:02 -0500
From:
Rick Wynn <Sales@WynnEnv.com>
To:
Don Burch <theunk@telus.net>

Don,

There's more to it than just the surface area. Spunbond media has much
slicker fibers, and a much more uniform pore structure. It's easier to
clean a spunbond, so on an apples-to apples basis the paper blend needs
to be 2.0-2.5 times the sq. ft. to achieve the same pressure drop.

The wasted space has a purpose. Since the spunbond can get the job done
with less media, the pleat count is lower. This is extremely beneficial
when there are fibers in the dust. Paper blend filters are hard to
clean if fibers get packed down in the pleats...spunbond's open pleat
design eliminates this problem.
...

Thanks,
Rick

This regarding 35A canister conversion elements. The spunbond is rated at 1 micron, the paper at .5 micron. I suspect the same logic would apply across the board. Wynn do not supply a spunbond Farr style, only in the Torrit style.

Discussion with Maddocks Group

-------- Original Message --------
Subject:
RE:
Date:
Mon, 7 Jan 2008 10:24:54 -0500
From:
Daniel Moscardini <daniel@maddocksgroup.com>
To:
Don Burch <theunk@telus.net>


The square footage would be 130 for the 36" spunbond cartridge
but the other factor to consider is the 'Average Air to Cloth Ratio'
which is the number of cubic feet of air per square foot of media.
Paper products have a ratio of 1-2:1 and spunbond is 4-6:1
So paper would be 300 to 600 cubic feet and Spunbond would be 480 to 720.
Dirt releasablity would also be better with spunbond because of the much
more open pleat design (not packed in as tight).

-----Original Message-----
From: Don Burch [mailto:theunk@telus.net]
Sent: Monday, January 07, 2008 12:16 PM
To: Daniel Moscardini
Subject: Re:


Dan

Are you saying that a square foot of spunbond passes 3-4 times as much
air than blend?
If you are filtering .5 micron or less at 99.99% would they not pass the
same amount of air?


Following this I received a fax containing a lot of technical specifications, but no clear answers.

It seems that 1 square foot of spunbond passes 2 -2.5 (Wynn) to 4 to 6 (Maddocks) times as much air as paper. This would suggest that the gas stream entering the element has 2 to 6 times more velocity and force. 2 - 6 times less chaos within the space between the gas stream and the surface of the element.
The cyclone is running at peak efficiency, fantastic separation, but because these thing work on % by weight, less coarse dust passes into the filter. This mean a long time before the cake builds.
If our cyclone is doing its job, the ratio by weight of the exhaust gas is now heavily skewed towards the less than 1 micron particles. The very particles we are trying to eliminate. The Dylos readings certainly confirm the extremely high count in the 1.0 (Nikkel) and 0.5(Haney) micron range.
One very big red flag for me is for Rod & Denise, and anyone else who uses this type of element in a commercial environment, I hope your respirators are near .1 to .2 micron because of your extended exposure to high concentrations of extremely fine dust.

Rod & Denise: I would strongly urge you to see if your old elements can be cleaned. Try Paul Gagnon at Western Ultrasonics in Edmonton. I worked with him a few years ago on cleaning oil sands bitumen from our filter elements. If his process can shake that crap off, a little dust should not be a problem.
If they can be cleaned, do it and put them back in service as soon as you can. Order a spare set of elements from Clear Vue or Wynn if they will sell directly. I had heard they were not as keen on shipping to Canada, but that may be rumour only.
The hemipleats will settle in eventually, but for how long and what will you see after the first cleaning?

Mine aren still in the box. Do I scrap them or get 2 more to up the surface area?

I really think surface area is critical - possibly more important than easy cleaning. Other than the occasional overflow, I have never heard anyone on this forum complain about poor filter life from the blend media. But how many are monitoring dust at the .5 micron level as Ed is?

Ed, what elements are you using?

I invite a good discussion on this because, if the blend elements that are in use are passing untold amounts of less than .5 micron dust into the work space, many people could be exposed.
I do not see this as an issue with the cyclone, but our understanding of the components of the exhaust gas stream and filtration.

I am no expert on this, just trying to apply my own sense of logic to the issue.

Don

 

[R and D Nikkel]

Don
I'm no engineer and the only chaos theory I know about is when I look at my desk... so that part of your post goes over my head a little. I think part of our problem is how we think about the filters. I had in my mind the idea that they were solid with holes only 1 or 0.5 microns in size depending on the "rating" so everything larger got trapped. That isn't how they work apparently. This is where the testing comes in. They aren't testing the filter media by measuring hole size. They are testing it by measuring what comes through it at specified conditions. With that, you can compare between media types. The chart Wynn puts up on its site (though missing some information) is really helpful to compare between their paper ones and the Hemipleats we have, which are also an 80/20 blend. Comparing these two standard test results, the Hemipleats with less surface area actually catch a slightly higher percentage of dust at the different sizes than the Wynns with more surface area do. I expect the CFM testing levels are similar, but Wynn doesn't put out what CFM level their test was run at.
What I do know is that lower resistance is better because less resistance = more air flow. The whole system works more efficiently the more air it moves and the filters can backlog the whole thing right up to the port on the equipment if it won't let much air through. So I am not worried at this point about adding more surface area. If the two we have now have more air flow than our two old ones did (when all were new), and if they catch the same or more dust per cfm, then we will get better performance from our system than we had before.
We can't go back and use the old filters. For one thing, we have changed our system to filter from the outside in, not the inside out, so that basically be backflushing the filters into our shop - not a good thing. We also destroyed them by scavenging the bottom metal and gaskets to use for our cleaning function. And yes, masks are being worn when the meter tells us counts are high. We also have an air filter we are running again that also helps bring the counts down. But at least now we can use it! Prior to the cyclone it got choked with dust so quickly it was basically useless and hung idle for years. Now it is being used as it was meant to be used - to clean up the final traces of fine dust, not be the only dust collector in the place!
Once we do a clean we will put pictures up of our system, and give more information on how things are going. The dust levels are coming down, but it is taking a while.