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Thread: Blast Cabinet exhaust?
04-16-2006, 12:35 PM #1
Looking for a good idea for exhausting my newly aquired blast cab. Cheap of course! Maybe a cheap shop vac? It is in the shop so it ought to have a decent filter. Although it is on wheels so I could roll it out side. Thought I,d see what some of you folks have done.
04-16-2006, 12:43 PM #2
I hooked my shop vac up to my home build cabinet.
04-16-2006, 12:50 PM #3
I'd get a fairly large inexpensive vac, and vent the exhaust from it outside the building. Better yet, put the vac itself outside the building, so you don't have to listen to it. Wire it up to come on whenever the light in the blast cabinet is turned on.
Unless you use expensive filters, there'll always be some fine stuff getting through, and you don't want that stuff in the shop where you'll be breathing it.
04-16-2006, 01:16 PM #4
I've got a large cabinet blaster and it started out in the shop. Wasn't long until I moved it outside though, mainly because it is so big. When it was in the shop, I had the vacuum part just outside the door. One thing to remember is to not use the silica sand it it. Get something like Black Beauty or glass beads, depending on the type of work you will be cleaning.
04-16-2006, 02:15 PM #5
"...you don't want that stuff in the shop where you'll be breathing it." Baloney. Lungs will heal up. Valuable hard to replace machinery subject to airborne abrasive flat wear out.
What? Not enough touchy-feel regard for health and welfare?
Seriously, you DO want a negative pressure in the blast cabinet and you need to isolate from the oily and clean parts of the shop. The best negative pressure set-up is a blower that exhausts where no-one cares about a little abrasive dust. While basic shop vacs work pretty well they don't do a good job of catching the fines even with a drywall dust bag. There are some cheap inverted filter shop vacs out there built for serving a blast booth but you still need to route the exhaust out of doors.
04-16-2006, 03:21 PM #6
the set up we had at my last place of work was a large vacuum and it had an extra filter bag where the air comes out of the vacuum to catch the finer particles....
04-16-2006, 03:29 PM #7
There has recently been a thread on Home Shop Machinist about an air powered dust collector sold by HF that uses an air jet and a venturi section to creat a strong negative pressure within a blast cabinet. I've about worn out the fan blades on the vacuum type dust extractor I use, and I,m considering buying one of those.
IIRC, only about $100 or so. Nothing to wear out.
04-16-2006, 03:55 PM #8
I purchased a vacuum unit made by the blast cabinet mfg. It looks like a household built in type unit, tub clips on the bottom, filter bag, and the exhaust I plumbed to the outside. Our cabinet is in a small room under a staircase, no dust problems in there.
my wheels don't slow me down
04-16-2006, 06:55 PM #9
You might consider a cyclonic separator between the blast cabinet and your vacuum. They can be had pretty cheaply, but they do have a pretty big footprint for a crowded shop.
04-16-2006, 08:35 PM #10
I connected a squirel cage exhaust fan to my cabinet and exhaust it outside. I also connected one up for a friend with a larger "paddle wheel" type blower - had to put a baffle in the suction line because it pulled too much suction on the cabinet. Do not have to worry about clogging filters.
04-16-2006, 09:36 PM #11
enco has a vac just made for a blast cabinet it works well
04-16-2006, 10:35 PM #12
So what happens if you don't have any vac on the blast cabinet at all? Why is the vacuum necessary in the first place? Why can't you blast without one?
(I obviously don't have a cabinet... [img]smile.gif[/img] )
04-16-2006, 11:36 PM #13
You can't see much in a blast cabinet without pulling the dust storm out. Most probably leak somewhere and would have positive preasure from the blast gun, which uses 90lb air and higher, forcing dust/grit into the shop.
04-17-2006, 11:06 AM #14
Yeah, of course the air from the gun would obviously pressurize the cabinet if not allowed to go somewhere, but why can't you just cut a hole in the top of the cabinet and run a big hose to somewhere you don't care about (like outside)? Gravity should keep the grit from going up the hose and if a little suspended dust does eventually manage to find it's way up the hose and outside to the trees, who cares?
Why is it beneficial to have additional suction from a vacuum source to negatively pressurize the cabinet? Are you saying can't see what you're doing without actually sucking the dust cloud out with a vacuum?
04-17-2006, 02:19 PM #15
"Are you saying can't see what you're doing without actually sucking the dust cloud out with a vacuum?"
FTF, in most shop with cheapo blast booths, yes depending on how much "flour" tramp dust and rust is mixed with the blast media. A percentage of the media shatters or wears down as it cycles through the nozzle. Then there is the paint and rust thats blown off. Not many blast booths come equipped with a classifier that removes all but the usable abrasive from the booth interior.
A friend of mine has a 3 ft x 6 ft blast booth in his custom shop. He's stripped so much paint and rust the media charge is heavily contaminated. If you don't turn on the Torrit filter first, within seconds it's like a billowing dust storm between the glass and the work.
04-17-2006, 10:11 PM #16dloc Guest
Three approaches. 1) Buy a good Torrit good to 0.2 microns or so. Not modify it to fit your shop-vac. 2) Go to the local big box store and buy a Gortex replacement filter for your shop vac, also good to better than 0.2 microns or so. This is the easiest approach. 3) Go to the local autoparts store and buy a canister air filter element for a big diesel engine and modify it to fit your shop-vac. Need to sheck the specs on the latter but many are also good to 0.2 microns.
Dust particles between 0.5 and 20 microns is what gets you because they lodge in the lungs. Particles smaller than 0.05 float in and out in the air stream. Ones larger than 20 microns get filtered out before reaching the lungs. Particles between 0.5 ansd 20 microns are too small to be seen by the naked eye. So it is what you can't see that will get you.
04-18-2006, 12:11 PM #17If you don't turn on the Torrit filter first, within seconds it's like a billowing dust storm between the glass and the work.
Makes me regret a decision I made a year ago not to buy a nice used blast cabinet that was being sold by a shop consolidating locations and equipment. They were selling it cheap because the filter was torn and they considered the cabinet unusable without repair.
They said that it billowed grit all over the place, and with that description, the problem sounded a lot more complicated than it really was. I thought the filter had something to do with the media source, not the dust exhaust.
Now I know better! [img]smile.gif[/img]
04-21-2006, 02:27 AM #18
Most sandblast cabinets use either silica sand, glass beads (which are actually identical to silica sand in chemical composition), walnut hulls, plastic, and silicon carbide. When you sandblast with silica materials the silica dust comes out the back of the cabinet unless you have a dust extractor system. This dust is really fine silica. It can be so fine that it settles in the lungs and is so fine that the body can not get rid of it. Silica in the lungs causes silicosis. You get steadily more short of breath, the lungs scar and eventually you cannot breathe at all. Silicosis is the chief real cause of black lung. You can see them under the microscope. Little clear needles. The carbon in coal is actually pretty nontoxic. The silica in the coal is what does the nasty. The body does a good job of getting rid of large particles, but below a certain size the body can not get rid of them.
I sandblast and use either an air fed hood or a cabinet with a dust extractor. In addition to using the dust extractor, I have a second hose that leads from the outlet side of the dust extractor to the outside of the building.
If you run a hose from the cabinet or room to the outside, you are pumping that fine dust into the atmosphere. That dust can be thick enough to be visible. You run the risk of having a visit from the EPA or the county health department. The filter bag on a shop vac is not fine enough to trap the fine dust from a blast cabinet. Clean your shop and use a shop vac for a while and I think you will find that there is a fine dust on all flat horizontal surfaces such as machine ways.
Laurentian liked this post
10-29-2014, 05:09 AM #19
I realize its an old tgread, but I have some issues with my swtup. I have a small blasting cabinet, hooked to a fine ash bucket with a filter, and then to a 1300w shop vac. when I turn it on, I dont see any dust collecting or coming out, but then it is imposible to work inside booth-gloves are getting sucked, and I can hardly move them :-)
How to fix this? my vac doesnt have power adjuster
10-29-2014, 07:30 AM #20
If you're trying to reduce the vacuum.....
Reduce motor speed with a variac, put a blast gate in the vacuum cleaner hose and adjust the opening till it's just right, put a smaller vacuum cleaner hose on, squeeze the hose with two pieces of wood and a clamp...... anything that will reduce the hose size and is adjustable.
Or do the same to the vacuum cleaner outlet side.