My second project, lighting for my bead blasting cabinet

[pontiac428]

Flyinfool, you are correct on how cyclones work. During engineering, the height of the cyclone can be set for a particular efficiency, but ultimately it is air velocity that determines the particle size cut point. Cobbling together systems of vacuums and whatever separator you have on hand would certainly require some trial and error. Wood shops are a much better application with their big, light particles. I would prefer filtration for such fine particles as blasting debris. That's what is used in heavy industry for blasting and powder coating, you only see cyclones in wood shops.

 

[C-Bag]

My cyclone was just engineered to stock. 24" tall, 8" at top and 4" at bottom. The vac tube is 2" PVC and about 14" from the top down the middle on the inside. It was just a Hail Mary because I got maybe two sessions out of the hepa filter before it was totally clogged with powdercoat. And because it got pretty warm blowing out the filter didn't do much. After doing the DIY cyclone it takes at least 15 runs of powdercoat before it's plugged for good. So it's paid for itself. But the combo of glass dust from over pressure( I dropped pressure down and it drastically cut down on the glass dust) and it not being affected by temp really got to the hepa filter. There was some glass dust in the cyclone bucket and none in the vac bucket. Just all in the filter. I really think Brino is on to something with water in the bottom of the cyclone bucket for glass dust.

 

[pontiac428]

Getting 15x more blast time per cleaning by adding the cyclone is impressive! Especially a little guy like that, I was expecting your shop vac to have enough pull to short circuit the cyclone. You can also run cyclones in series if they don't take up much space. I still just wheel my shop vac over to my cabinet when I use it (straight through the rear bulkhead supplied in the cabinet). Since I use the vac for general purpose, I never see filter loading. Doesn't mean it isn't happening. With a dedicated unit, it makes sense that you would quickly figure out what works and what doesn't.

 

[pontiac428]

Here's a really good paper on this application of cyclones. There's information you can use in the shop to improve your design here.

 

[brino]

I really think Brino is on to something with water in the bottom of the cyclone bucket for glass dust.

A cyclone "bucket" with water in the bottom is one thing......I'm also thinking about having the intake tube under the water level so all the air has to bubble up through. I'm wondering if that may help to get the very fine dust stuck in the water. In fact, maybe more of a water filter than a cyclone.

I believe I saw something similar for drywall dust.....

-brino

 

[C-Bag]

A cyclone "bucket" with water in the bottom is one thing......I'm also thinking about having the intake tube under the water level so all the air has to bubble up through. I'm wondering if that may help to get the very fine dust stuck in the water. In fact, maybe more of a water filter than a cyclone.

I believe I saw something similar for drywall dust.....

-brino

Woa, dust hooka! I don't know how I'd do that with the cyclone. Maybe as another dedicated stage? I feel like I'm already close and that maybe the water in the bottom of the bucket will do the trick. That whole cyclone thing was just desperation and realistically it's more like 5-6x's better than without.

 

[C-Bag]

Here's a really good paper on this application of cyclones. There's information you can use in the shop to improve your design here.

Wow, I looked all over to try and get some kind of clue about making a cyclone. It was probably a good thing I didn't see that as I'd have to hire a math translator to put that to work. One of the things I don't understand is why the vac pipe is so short on the examples. I never could find any cutaways so I made the big WAG and extended the vac pipe down where I figured it couldn't pick up anything from the inlet. An interesting point in looking at the PDFs is the use of electrostatic for filtering. I get a good electrostatic charge of the cyclone when doing powdercoat. I didn't notice if the same thing happened with glass dust.

 

[pontiac428]

Electrostatic filtering is amazingly efficient. I see it used in bag house applications (wood dust) usually post cyclone. The only reason to pursue it is if you need to reduce the costs of HEPA cartridge replacement.

The engineering term for a bubbler is "impinger". They are used for certain things on the lab bench or for aerosol sampling, but I can't think of any industrial applications beyond what a humidifier or evaporative cooler that cleans the air of particulates can do as a side effect. That's not to say it won't work in the shop. It might be hard to tune for efficiency and noisy to operate, plus you have haz waste on your hands when the liquid is "pregnant" with particles of paint (lead and chrome), metals, and ultrafine pulverized blasting media (beryllium, crystalline silica).

Does anyone have a means for varying the output of the canister vac? I figure most of them draw too much power for a rheostat.

 

[C-Bag]

Electrostatic filtering is amazingly efficient. I see it used in bag house applications (wood dust) usually post cyclone. The only reason to pursue it is if you need to reduce the costs of HEPA cartridge replacement.

The engineering term for a bubbler is "impinger". They are used for certain things on the lab bench or for aerosol sampling, but I can't think of any industrial applications beyond what a humidifier or evaporative cooler that cleans the air of particulates can do as a side effect. That's not to say it won't work in the shop. It might be hard to tune for efficiency and noisy to operate, plus you have haz waste on your hands when the liquid is "pregnant" with particles of paint (lead and chrome), metals, and ultrafine pulverized blasting media (beryllium, crystalline silica).

Does anyone have a means for varying the output of the canister vac? I figure most of them draw too much power for a rheostat.

I'm worried too about what to do with the waste. It's one thing if it's dry but another wet. All of it is worrisome. Powdercoat is supposedly non toxic and because of its propensity for static charge it seems easier than glass dust to control. Not that I knew what I was doing just that my lo budget ways of dealing with it seemed to worked out. My mini booth is made out of sheetmetal with the frame being 3/4" EMT. Somehow this seems to attract a lot of the powdercoat as the majority of it ends up on the bottom of the mini booth with the next bigger lot ending up in the cyclone bucket.

The first time I tried my HF blaster I used sand and it proved to be way too rough finish for powdercoating over. Not until this last experiment did I try glass beads. The pressure pot I believe made a huge difference but it also took a lot of messing with setting the pressure and setting the three different valves. Then this whole issue of lighting, so it was a lot juggling with stuff. Another issue is I need to put my compressor on its own 220v circuit. Too many issues for something I don't often need

Are you trying to vary speed of the vac to tune amount of vacuum? I've not seen on shop vacs what the old house vacs used to have that was a sheetmetal sleeve that fit over a port in metal hose end that you could rotate it over the port varying the amount of bypass causing a leak so to speak. It would be a project to make something as the shop vac makers seem to go out of their way to make their hose size proprietary. It could be done out of PVC.

 

[Flyinfool]

As mentioned you can add a variable "leak" in the hose to reduce the volume of air being sucked in at the end of the hose. but this will not reduce the airflow at the vac its self, it may even increase it.

Most vac motors have carbon brushes and are of the universal motor type. (Some newer stuff uses brushless DC motors) The Harbor freight speed control for routers will work on most universal type motors to vary the speed, but with reduced speed you have to watch that the motor does not overheat. you are not just slowing the vac air speed but also the cooling fan speed. Most vacs do not use the vacuum air for cooling, it is a separate fan.