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BadDog
06-20-2009, 06:17 PM
Well, last night I finally got around to rewiring my blast cabinet (patch panels were (re)done last week). Unbelievable that they were using this thing, you could SEE electrical conductors through the cracked/missing insulation! I was scared to plug it up the first time I tried it to see what worked or not.

I put in 2 qts of Silica 30 today just to test it, and other than a sticky main valve I need to look at, all systems are go. Added 1 more qt just for good measure and called it a success! :D

Not a surprise, but even with the cyclone separator there is significant particulate in the exhaust stream. This will probably drop as the excess of initial "fines" departs, but of course it will continue as grit brakes down. So I'm wondering what is the best solution for removing most of those without unduly restricting air flow?

They make bag filters just for that purpose, very similar to the ones used as dust collectors in wood shops, but they are not cheap. But since I can easily roll it outside to use, I'm wondering if there is any good home-brew solution. Then I began to ponder something like the old oil bath breathers or the like, but maybe using water. Just wonder what some of you may dream up, or what you may have seen that might work. If nothing good comes out of the discussion, I'll probably just order a "bag", but can't really do that till Monday anyway, so thought I would see what might shake out...

gnm109
06-20-2009, 06:28 PM
Well, last night I finally got around to rewiring my blast cabinet (patch panels were (re)done last week). Unbelievable that they were using this thing, you could SEE electrical conductors through the cracked/missing insulation! I was scared to plug it up the first time I tried it to see what worked or not.

I put in 2 qts of Silica 30 today just to test it, and other than a sticky main valve I need to look at, all systems are go. Added 1 more qt just for good measure and called it a success! :D

Not a surprise, but even with the cyclone separator there is significant particulate in the exhaust stream. This will probably drop as the excess of initial "fines" departs, but of course it will continue as grit brakes down. So I'm wondering what is the best solution for removing most of those without unduly restricting air flow?

They make bag filters just for that purpose, very similar to the ones used as dust collectors in wood shops, but they are not cheap. But since I can easily roll it outside to use, I'm wondering if there is any good home-brew solution. Then I began to ponder something like the old oil bath breathers or the like, but maybe using water. Just wonder what some of you may dream up, or what you may have seen that might work. If nothing good comes out of the discussion, I'll probably just order a "bag", but can't really do that till Monday anyway, so thought I would see what might shake out...


I have a Cyclone (brand) dust collector which was designed to sit on top of a 55 gallon barrel. It has a large exhaust filter bag over the 4" exhaust tube. It catches all of the fine particulate matter. I empty it now and then and also open the door in the side of the barrel that I cut to vacuum out the heavier stuff. It keeps the inside of the blast cabinet clear of dust when it's working and keeps it from covering everything in the shop as well.

I suggest a cloth exhaust bag on your outlet. ENCO has them and they can be used separately if you already have a dust collector. Here's one for $27.95 with current free shipping with the code which I've conveniently misplaced.


http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=7856351&PMAKA=422-0000

BadDog
06-20-2009, 07:51 PM
Thanks for the link!

How does that attach? Does it just have a 4" sleeve or something that slides over the outlet (mine's actually about 3.5")? Or would I need to construct a round to flat plate adapter or the like?

oldtiffie
06-20-2009, 08:06 PM
I've seen a method somewhere on the net - here? - that had a cyclone in the exhaust that also enlarged the pipe diameter. The cyclone got most of the "heavies" due to centrifugal force as they hit the sides and dropped into a hopper. The "fines" tended to drop out of the air stream as it slowed in the larger diameter pipe. This too was set on a large drum.

Needless to say, the finer the filtering the greater the pressure drop/restriction per unit filtering area required across it - even when new and worse as it get clogged up - and so will cause a drop in air flow across the entire system. That implies that the need for a finer filter required a larger filter area to reduce pressure drop/loss to an acceptable level in the system.

oldtiffie
06-20-2009, 09:06 PM
Filter blocking is a problem that needs to be addressed regularly. Some people just use "sound" and others when performance drops off.

Many air systems - air-conditioning (particularly where fine HEPA filters are used) and some vacuum systems - have a "pressure drop" guage and/or light/warning that senses the pressure drop to warn of the need to clean or replace the filters.

All that is needed is a good low pressure guage/switch with an air line to either side of the filtering medium. The controller just measures/senses the pressure differential ("drop") across the filters. A glass "U" manometer will do just as well most times.

I have seen systems where a secondary vacuum system is fitted down-stream of and to "assist" the blaster exhausts and filters.

BadDog
06-21-2009, 02:11 AM
Good points. Mine already has the cyclone separator, it's the fines I'm trying to figure out how to control. Interesting though on the expansion chamber, and that's one thing I have considered, but with the addition of a water trap so they don't just get picked up and carried on by turbulence. Easier than a true oil/water bath, and might just work. But one problem is that the volume is so high, I think it would take a pretty good size expansion chamber to be effective. Like on the order of a 55 gal drum. I'm looking more for a 5 gal bucket solution. :D

A secondary goal is to muffle this thing a bit. Sounds a bit like working near a jet-way. :eek: Gotta wear ear protection around this thing...

And for my needs, I don't think I'm too concerned with pressure drop. I'm sure I'll hear it in plenty of time. Also, as it slows down, I'll have a visual indicator in that the cabinet will get start to get more "foggy".

oldtiffie
06-21-2009, 06:32 AM
Russ,

I don't have and so far don't need a shop metal-blaster but I do have a dust and shavings collector on my wood-workers "planer table" which extracts the air from the standard ~3 1/4" wood hand-held power planer outlet port.

I haven't used it for quite a while, but it seems to work well enough - even though I use it outside of the shop - just in case. I will get the details of it tomorrow and if I can find them I will post them here. It also works off my fairly old but still good enough "Shop-Vac".

From the planer, it goes into a "bucket" that has two down-facing elbows - as a "first stage" which gets rid of most of the "gunk" and from the second elbow to my Shop-Vac as a second stage.

So far as I recall, both the first and second stages have a 90 degree (elbows) inlet to and out from the "buckets". The change of direction seems to act as a sort of part cyclone using centrifugal force with inlets to and from the "buckets" each of which seem to act as an expansion chamber to slow down the air and scrap velocity. I think that there are filters in both stages - but I need to check.

I would guess that gravity takes care of the larger chips etc. and that the filters take care of the rest.

This is from memory - so don't take it as Gospel yet - until I check.

oldtiffie
06-22-2009, 07:39 AM
Russ.

Just as well I checked today - as I was OK with the principles but wrong with how and where they were applied.

I have the pics and the links to PDF files that should help. I just have to get it all together so that it makes sense.

I am quite sure that it will help you - with the ideas and the applications - but you may have to vary them to suit yourself.

More in the next day or so.

I will PM you with the link when I get it done.

Evan
06-22-2009, 07:57 AM
Build a box that takes a stack of 3 or 4 furnace filters. When it begins to clog throw out the innermost (or clean it) and add a new one at the other end. If you want to be really fancy you can buy a (not cheap) electrostatic precipitator filter that fits a standard furnace filter slot. That will take out 99% and can be washed with a hose to clean.

I use a furnace filter in a box to vent our clothes dryer inside to avoid wasting heat and humidity in the winter. Clothes put out some pretty fine lint but it doesn't get past the filter.

oldtiffie
06-23-2009, 04:59 PM
Bump.

Russ, I will see if I can get around to this today - or tomorrow.

ahs437
06-23-2009, 05:11 PM
The cyclone will spin out the grit (actually boulders in the dust world)... Fine stuff isn't worth trapping. It has no value for re-use and the size distribution could be below 20 microns (bad stuff to breathe). Let it go... heck, help it along if you can. Dilution is the solution and you REALLY don't want to breath it. Emptying filters is a significant exposure source. To trap stuff that small you need a LOT of filter surface area to avoid a pressure drop (and you don't want your blast enclosure backing up) .... If air can't get out it can't get in.... Furnace filters won't do a thing. Not designed for this application... a bag filter is going to work (and it will work better the more it clogs), but why waste your time. Electrostatic precipitation and scrubbers aren't small time devices suited for this application. My 2 cents... dust is my life (mining engineer)... Work safe

Andy

BadDog
06-23-2009, 06:17 PM
Good stuff, thanks.

My biggest issue is I don't want a fine coating of silica dust all over my vehicles, lawn furniture, people, dogs, and anything else within a quarter mile of the exhaust plume. :D So how best to eliminate or at least drastically reduce that mess? I'm not interested in catching/keeping/reusing it. I just want to reduce the dust coating on stuff and general exposure for anyone who happens to pass along in the path of the debris cloud...

gnm109
06-23-2009, 07:52 PM
Thanks for the link!

How does that attach? Does it just have a 4" sleeve or something that slides over the outlet (mine's actually about 3.5")? Or would I need to construct a round to flat plate adapter or the like?

Sorry, I should have come back earlier.

The bag attaches to the Cyclone Exhaust with a 4" ID hose clamp. In one of your posts below, you mentioned that you don't like noise. You wouldn't like my Cyclone unit then. It sounds like a Jet plane taking off with the afterburner engaged. LOL.

It does hold in most of the fines. If you want none of the fines in your shop, you could mount the unit outside and run a tube into the shop with the start/stop switch inside.

oldtiffie
06-25-2009, 08:03 AM
Russ,

I apologise for not getting back but in my usual fashion I succeeded in side-tracking myself - again.

I have the pics I want (needed more and had to set up and put equipment away etc.).

I will be a long-ish post with quite a few pics and links, but I'm sure you will see the principles, applications and uses of what is essentially an easy, portable and effective filter system. It is fairly easily made from stuff that is around the shop or easily and cheaply bought.

I will have it done in the next few days - he says - again with the same old lame excuse!!!

BadDog
06-25-2009, 12:36 PM
gnm:
Yeah, seems like my "cyclone" system is much like yours in that it sounds like a jet taking off. My current solution is also as you suggest, I roll it outside, and will continue to do so even with a filter. My main concern (other than noise) was the dust clout that settles over everything nearby.

tiffie:
No worries mate. :D Believe me, I know ALL about getting side tracked on stuff. In the last week I made a "precision" mounting plate for a friend building a glass lathe (finished), a dozen "top hat" bushings for a friend doing upgrades on a truck (finished), parts for my bandsaw (not finished), parts for my motorcycle (finished), some shop re-org (never finished), and of course fooling with the blast cabinet (not finished). Little here, little there, next thing I know the week is gone and little to show for it...

oldtiffie
06-27-2009, 02:13 AM
Russ,

I apologise for not getting back but in my usual fashion I succeeded in side-tracking myself - again.

I have the pics I want (needed more and had to set up and put equipment away etc.).

I will be a long-ish post with quite a few pics and links, but I'm sure you will see the principles, applications and uses of what is essentially an easy, portable and effective filter system. It is fairly easily made from stuff that is around the shop or easily and cheaply bought.

I will have it done in the next few days - he says - again with the same old lame excuse!!!


gnm:
Yeah, seems like my "cyclone" system is much like yours in that it sounds like a jet taking off. My current solution is also as you suggest, I roll it outside, and will continue to do so even with a filter. My main concern (other than noise) was the dust clout that settles over everything nearby.

tiffie:
No worries mate. :D Believe me, I know ALL about getting side tracked on stuff. In the last week I made a "precision" mounting plate for a friend building a glass lathe (finished), a dozen "top hat" bushings for a friend doing upgrades on a truck (finished), parts for my bandsaw (not finished), parts for my motorcycle (finished), some shop re-org (never finished), and of course fooling with the blast cabinet (not finished). Little here, little there, next thing I know the week is gone and little to show for it...

Hi Russ.

I hope that this both helps you and is worth the effort and the wait.

I'll see if I can get it right and finished this bloody time!!

So here we go.

First of all, the principles here are those of a partial cyclone where the air-stream is diverted and the changes in velocity (speed and direction) of the air-stream causes the particles in the air to have their speeds reduced to the extent that gravity takes over and they drop. There is the principle of filters/strainers as well as push and pull air-streams. I have combined them in parts.

Everything other than the mitre saw (10" USA-made "Bosch") and its bench/table (made in China) are "Triton" products which are an OZ firm with all of their stuff (at least they were - can't be sure lately) made here as well. All the products as well as the catalogue and manuals are here:
http://www.triton.com.au/companyprofile.php

http://www.triton.com.au/documents.php

http://www.triton.com.au/documents/download.php?id=2

http://www.triton.com.au/index.php

http://www.triton.com.au/accessories.php?id=1#accessory_11

This is the filter end of my planer set-up. The planer acts as a driver fan and exhausts via a ~3 1/2" corrugated flexible bend that causes the larger particles to lose speed and drop into the bottom of the filter-medium bag. The now slower-speed finer particles are caught by the large surface-area filter medium bag. The bag it very easy to remove, turn inside-out - or just up-end and empty. There is not much that it misses. It takes a lot to fill or block the the bag.
http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton2.jpg

http://www.triton.com.au/documents/download.php?id=81

Next is the Triton "dust collection system":
http://www.triton.com.au/accessories.php?id=1#accessory_57

http://www.triton.com.au/documents/download.php?id=22

which relies on a suction (from my old "ShopVac"). It has a partial vacuum at the input which "assists" the "blown" (positive pressure) air and wastes (from a tool) via a corrugated hose and a 90 degree partial bend which slows the larger particles down and gravity takes over and drops them to the bottom of the "bucket". The partial vacuum in the bucket acts as an expansion chamber and so slows the air velocity and so catches smaller particles. Any (most?) that remain in the air-stream are caught by the filter media in the top of the bucket - just before the vacuum exhaust. The exhaust/partial vacuum is supplied by the ShopVac which has another 90 degree bend and so catches any more suspended solids as the air stream is deflected and speed reduced in that partial vacuum as well. I can either install or remove the ShopVac filters. If I wanted additional vacuum "assist" I could install another vacuum cleaner in the line down-stream of the ShopVac exhaust.

In just about every case the cutting tool provides the air with the initial velocity to the waste in the air-stream:
http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton4.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton5.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton6.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton7.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton8.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton12.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton13.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton14.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton15.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton9.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton10.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Triton/Triton11.jpg

Thruthefence
06-27-2009, 02:21 PM
Maybe exhaust it into a drum half full of water, like one of those drywall vacs, but with positive pressure? Make the standpipe with numerous small holes to break the bubbles up, more surface area to 'cleanse' the debris from the air stream.

BadDog
06-27-2009, 02:29 PM
Thanks for all the effort Tiffie. A bag like that (and mentioned previously) might be just the thing to reduce the cloud.

It also might be useful to add a secondary bucket like you show, basically being an expansion chamber to reduce the particles going into (and clogging) the filter bag.

For reference, I finally got off my back side and took some pictures of it. Not much, but it clearly shows the hopper/separator assembly along with the extractor impeller assembly.

And don't think too much about the return hose currently in place. It was cheap and gave me a way to make it functional until I can get a proper rubberized return hose.

Click for full size:

http://img4.pictiger.com/dfa/18279618_th.jpg (http://baddog.pictiger.com/images/18279618/)

http://img4.pictiger.com/a0b/18279620_th.jpg (http://baddog.pictiger.com/images/18279620/)

BadDog
06-27-2009, 02:32 PM
Oh, and the second pic shows the 3.5" exhaust outlet. That's where I need to collect the "fines". For now I just roll the hole assembly out of the shop so it sends the cloud into my back yard...

And the rubber mat is just lying there to "relax" (flatten) in the heat. It's part of another unrelated project and is not a patch or in any way part of the cabinet. :D

BadDog
06-27-2009, 02:39 PM
Thru:
Yep, that's what I was talking about when I mentioned a water/oil bath filter/trap. But I don't think it needs to be immersed and bubbling to work. That would (I think) considerably slow the flow, which would not be good for the extractor functionality. Rather I think that stopping a few inches above the liquid and making the flow both expand and change direction should throw many/most into the liquid to be trapped. I'm sure water drops would escape the final exhaust, but that's no bid deal. Maybe point it into my wifes rose garden? :D

What I really need to find is one one of those 5 gal bucket tops that works like tiffies linked bucket. Slight mod and I'm off to the races!

Rich Carlstedt
06-27-2009, 05:08 PM
Keeping things simple, I rolled some chicken wire around a 2 pound coffee can, with enough wire for top and bottom.
Then I extracted the can and used the loose wire on the top, to engage the 2 1/2 inch exhaust hole which runs to my shop vac ( outside).
This 'form' is inside my blast cabinet at the top and out of the way of shot.

Now , I just sleeve the chicken wire form with a cheap shop vac filter paper
and close the neck with a rubber band. ( no sharp points please !)

When I am done glass beading, I shut off the vacumn and I hit the bag and all the fines fall off.

It is really a pre-filter for the shop vac and works good.
Rich