Dust in the filters

R

R and D Nikkel

New member
When we got our system in 2007, we were not expecting to have to clean the filters very often based on the resports we had seene. So when we were getting dust in the filters to the point of having to clean them every couple of months (and when we didn't, blowing the insulated ducting either off the system or, finally, rupturing it due to the back pressure) we were surprised and did a LOT of experimenting. With our set up, you can actually see chips going up and down between the bin and the cyclone when the bin is close to full. We contacted both Bill and Ed and did some experimenting based on their suggestions too. Here is what we are currently thinking is going on after two filter set ups and three bin set ups.

Number one reason for dust in the filters is definitely a leak below the cyclone in the bin set up. So that is the first thing to totally rule out. Use incense sticks (stinky things!) to look for air flow going in to your set up anywhere. Another test is to take a big garbage back with no holes in it and encase the whole bin set up in it. Duct tape the garbage bag to the cyclone and turn it on. If the bag sucks down to the bin quickly, you have a leak somewhere. If there is only very slow changes then that isn't a problem. (Nothing is totally suction proof, and to move chips you need as much air as you would need to blow them off your hand. A very slow change in the air in the bag won't do this. Information from Ed and Bill had us test this out.) So no, we don't have a leak below our cyclone, yet we still get more dust in the filters than is normally reported. So why?

In our case, we make a lot of really fine dust with a huge belt sander and a carbide grinding disc on a side grinder. This stuff overall is far finer than what is made with the planer or the band saw. The hardest dust to separate is the finest stuff, and even with a small percentage going to the filters, it adds up. Also, this is our business. Our equipment is used for hours pretty much daily. We make a lot more fine dust than the majority of people who use these systems. So that is part of the reason.

But the most important reason, I believe now, is that the distance between the cyclone and the bin is crucial for separation, and we have a low system with the bin close to the cyclone. This means that the swirling vortex of air changes direction inside the bin, not above it. Bill told us his design originally had a 6" long tube below the cyclone before the flex connection to the bin. We now have 6" total between the bottom of the cyclone and the bin. It still isn't enough. We have discussed with with a number of people and our conclusion - you need distance between the cyclone and the bin for proper separation. What is that distance? I don't know, and when we were talking with Bill a few years back, he didn't know either. But it is longer than 6" and probably less than 10" from our experiments. However, we don't have that extra 4", so we will just empty the bin earlier and see how that goes. Our next step would be to cut down the bin further yet, but so far with our new filter set up the cleaning is easier to do and we are just staying on top of that.

So, to people setting up the system, I would strongly recommend that they plan it so there is more than 6" of distance between the bottom of the cyclone and their bin. The more the better. It makes it really tough then to get things under an 8' ceiling and have a decent bin size, but for filter longevity, it is worth it.

The best plan, always, is to vent outside when/if you can, which we do all summer. And we don't see a whole pile of dust out back the shop though there is some. I think the wind blows it away. But with our winters, we have to use filters unless we want to literally freeze. Part of that balance thing...
 
Spun bond questions

Spun bond questions

Interesting but understandable that the length of this duct to the waste bin is important. There is a lot of action in the cone so haveing the correct amount of separation could be a factor.
Is there a reason 10" might be the max?

I also believe the spunbond media is not for a closed shop. Initial pore size is to large, the surface area is to small. Even for yourselves, you went from somewhere 300 sq ft/element to 179 sq ft / element. They may clean great, but in our application they do not cut it.

I am still a believer in cake, but our cyclones are so darn efficient, there is not enough of the right cake material getting through. This is even more difficult with these hemipleats.

We have to always keep in mind that these filters are made for engine and compressor intake air, not lungs.

Don
 
I am wondring about that not having an extra 4". To experiment, you can play with the length by adding below the lid rather than trying to make changes above.

The lid would have a hole in it that you connect the flex hose to, but the cyclone doesn't really care where the lid is in relation to the bottom of the separation cone, just the length of the pipe below it.

so if you went with

...............| |................
...............| |................


so above the lid you have your 6" of flex, but attach to the bottom part of the lid an exta 4" of some 6" pvc pipe, then the total length would be that magic 10" and you can see if it makes any difference for virtually no cost and it's easily changeable to see if you need a longer length or not.

Just thinking outside the box for a bit. worth a try.

Matt.
 
Roadkill,
I've done experiments like that. What I found was that the real distance is probably not much more than 8", but I am not at all trying to set a distance for sure because I don't really know. I just know it has to be longer than 6" because I know that doesn't work. I was hoping the new owners of Clear Vue would take the matter up and do some proper testing on their own to see what really is idea. In our set up, having something extend even 2" into the bin would mean having real problems removing the bin from below the lid.

Don,
We are happy with our filters and our set up. Initially the dust coming through was high, which was why I did the research to figure out what the real numbers mean and posted it here: http://www.clearvuecyclones.com/Bullentin/showthread.php?t=1190 The ease in cleaning, the lower back pressure due to clogged filters, and the readings that are great tell us that the filters we have are more than adequate. The MERV 15 filters would be great right out of the box, but they also clog up much faster than the ones we have (as explained in the above post) which would necessitate that much more cleaning and that much more wear on filters and therefore they would need to be replaced that much sooner. For people who want great numbers right away or who don't use their system a lot, the MERV 15 are the way to go. For people like us, the MERV 12 are good in a relatively short time period as they get "seasoned". The hemipleats also clean easier than the old ones, especially when filtering outside to in, and I believe that the different way they are made makes the difference in air flow compared to the total surface area. Since we run with two of them, we are happy with our set up, like I said.
 
Yes, it would be nice if the current owners did do more testing. The benefit of having customers like you is that it improves the quality of the product, but you are after all a customer, not an R&D department, and you are in the business of making money for yourself, not testing someone else's product.

My suggestion was based on your comment:

But it is longer than 6" and probably less than 10" from our experiments. However, we don't have that extra 4", so we will just empty the bin earlier and see how that goes. Our next step would be to cut down the bin further yet, but so far with our new filter set up the cleaning is easier to do and we are just staying on top of that.
Click to expand...

If putting an extra 4" inside the separation bin gives your that extra bit of protection in case you don't empty soon enough,then that is all the better for you. As you responded, you believe that it's less than the 10" mark then having that extra 4" is just a safety blanket.

From a testing perspective, what I would want to know is does the density and size of the separated particles make a difference to that distance. For example, your stream has a very high amount of fine dust, and does due to it's weight and characteristics make the distance required longer than say someone who has a high volume of larger chips for instance from a jointer or planer? Having an understanding of the dynamics can help the next customer who would have a knowledge of their dust situation better plan out how it implement this solution. It makes just as little sense to have a long tube on a unit that doesn't need it, as it is to have a short tube on one that does.
 
When I say that the 6" doesn't work, it is because I can see chips from the planer going up and down in the flex hose from the bin to the cyclone. This happens when the bin is getting fuller (not full or overfull, but fuller). But the chips don't go through the impeller to the filters because there are not chips in the box or in the filters when we check it out. I don't know about the dust because it is too small to see. And I know we get more dust in the filters than others seem to get. But then, I know we make way more fine dust than most people make too. So... unless there is someone who really can test things properly, this is all just anecdotal.
I did ask about others with a short connection distance to see if they have had similar experiences. The only response I got was from someone with a very short connection but a 55 gallon drum as his dust bin, which he would empty at about 1/2 full due to weight factors. So even though the connection was short, the distance to the dust and chips was long. I would be interested in hearing from other who do have a short set up from the bottom of the cyclone to their dust and see if they see similar things in terms of chips going up and down. I assume they would but...
The only problem I see with a longer distance between cyclone and bin is less room in the bin requiring more frequent emptying. I guess depending on how our system continues to function, cutting down the bin further would be the next step, but I hate to do that unless we have to. Now, how will we know if we have to??? That I don't know either...
 
Last edited:
This has been an interesting discussion, but it raises one question in my mind: Has anyone experimented with an offset connection to the bin -- in other words, a connection port that is set a few inches from the edge of the bin versus in the center of the bin. My gut feeling is this would reduce the development of a full symmetrical eddy in the bin and might reduce any return to the cyclone. As a side benefit, it might also facilitate lid removal.
 
A great addition to the CV supporting products page would be to offer 6" flex hose by the foot. I wanted to have a slightly longer piece than the 6" length that came with the system, but did not want to buy a 10' length.

Steve
 
Cone to bin distance

Cone to bin distance

Has anyone investigated this any further?
I am closer than ever to finally using my CV for more than garage wall art.
I have 10' ceilings so I have some flexibility in the distance between the cone discharge and the waste bin.

Don
 
As it turns out, I had a tall ceiling to work with (about 10'4") so I used a longer piece of 6" flex from the bottom of the cyclone to the dust bin. With the dust bin in place, the top of the dust bin is about 18" from the bottom of the cyclone and it works great. I guess that the additional length really helps with dust settling as I have yet to have even a single speck of dust show up in the cleanout box (I built it with a Lexan window so I could see if it needed emptying.)

I have attached a couple of photos that show this portion of my system. These photos were taken the day I got this part of the system assembled in March, 2013, but the cleanout box is still as clean inside as the day I installed it.
 

Attachments

  • Bin Sensor Mounting.jpg
    Bin Sensor Mounting.jpg
    674.6 KB · Views: 0
  • Dust Bin, Cleanout Box, Bin Sensor & Filters.jpg
    Dust Bin, Cleanout Box, Bin Sensor & Filters.jpg
    726.3 KB · Views: 0
Kim,

It was good to see your installation and to hear that your longer entry to the collection bin is working well. Love to hear about the good separation and near total lack of dust in your filter cleanout box (I guess that makes it a "clean" box, har, har!). While you didn't mention it, I guess your bin sensor system is working as expected.
 
Rob,

Yes, the bin sensor works great. I think I posted some lengthy comments and photos on a bin sensor thread last summer. Somewhat relevant to this thread is the effect of using a longer flex hose from the cyclone to the dust bin. As you can see from my photos in the previous post, my bin sensors are wall mounted about 10" above the lid to the dust bin.

I was concerned that dust would build up in the flex and that it would make a mess when I went to empty the bin. As it turned out, the eddy inside the bin makes the dust build up in a conical shape. All I have to do is give the bin & lid a quick shake and all the dust settles to about 2" below the rim of the garbage can / bin. Perfect!

My conclusion is that whenever possible, a longer section of flex below the cyclone can only help. BTW, I got my flex from McMaster-Carr and it works great.
 
You must log in or register to reply here.
Back
Top