Air born dust collection?

[Stacy E. Apelt - Bladesmith]

I edited my response to make it more clear. You need 4 things to keep your shop and air clean. That will keep the dust out of your lungs.

 

[godogs57]

Thanks so much. Looks like I need to get to work.

 

[Spideyjg]

As an example, changed mine today after about 3 sessions. Probably half was from tonight surface grinding 3 pitted 2 lb cleavers for about 2 hours.

 

[REK Knives]

As an example, changed mine today after about 3 sessions. Probably half was from tonight surface grinding 3 pitted 2 lb cleavers for about 2 hours.

Curious, What do the replacement filters cost on that?

 

[Spideyjg]

Curious, What do the replacement filters cost on that?

The Jet unit takes any 12X24X1 filter. The higher filtration the more expensive they are. The 9 or 10, highest filtration, can run $15.
This thing sits about 7 feet in the air about 3 feet from the grinder.

Washable electrostatics can be used.

It has an internal filter as well that is washable.

 

[Stacy E. Apelt - Bladesmith]

You can also take them outside and shake, vacuum, blow them off for a longer life.

 

[Mahoney]

If you want to protect your family from dust on a low budget, grind outside while downwind from the house and wearing your respirator. Once you bring the grinding inside, a dust collection system that will adequately collect the fine dust will probably cost more than the grinder did

Grinding metal can produce very fine dust that can hang in the air a long time and travel a considerable distance. Here's a cheap way to see if there's any floating in the air in your shop; get a "rare earth" (neodymium) magnet about 3/4" diameter or larger and 1/8" thick. Put it up on a wall somewhere in the shop far away from the grinder. Cut a piece of white paper about an inch bigger than your magnet and stick the paper to the magnet with double stick tape or glue, and look at the paper about once a week or so. If you never see a black spot on the paper over the magnet, congratulations, you either don't make fine dust in your work, or you have fabulous dust collection. Consider that the magnetic field lines only extend a few inches out from the magnet, so the dust on the paper is only the dust that was in an area maybe half the size of a grapefruit around the magnet. And this only catches steel, any silica/wood dust/aluminium/etc. will float on by...

Fine dust will settle, but it is very easy to stir up again. Any bit of breeze, or just walking through the shop is enough to get the fine dust moving. You can purchase a particle meter from Dylos and watch the effect for yourself.

I am not a fan of the hanging air filters for the following reasons, first, they are theoretically filtering out dust that you should have captured back at the grinder with your primary dust collection, and that's where the money should be spent. Second I have not seen a "shop air filter" yet that has a good enough filter to really capture the fine dust that is being stirred up by the fan in the air filter. Unless you have a MERV 15 or 16 (HEPA) filter in the unit the fine dust is just blowing through. Think about it, you wear a HEPA respirator to protect your lungs, why would you not clean the air in the shop to the same standard to protect yourself and your family when you travel through the shop without a respirator on?

 

[REK Knives]

The Jet unit takes any 12X24X1 filter. The higher filtration the more expensive they are. The 9 or 10, highest filtration, can run $15.
This thing sits about 7 feet in the air about 3 feet from the grinder.

Washable electrostatics can be used.

It has an internal filter as well that is washable.

Sweet thanks. The electro static filters seem the way to go, I use one on my house already

 

[joedhiggins]

Unfortunately not all of the particles are not heavier than air.. stuff stay in the air for a day or two....Especially grinding Micarta which releases Formaldehyde. Bone, Antlers etc ———————————It’s long term exposer to all of these fine dusts and any fine dust damages your lungs overtime!————————————-I have a customer that’s a Pulmonary Dr, he said Bakers can get a condition called.. “Bakers Asthma” from the fine dust of the white flour they are around.. I keep my mask on for the rest of day I’m in my shop after I stop grinding and have the air filter running....

I think I could have been more clear. I am not saying that grinders can release nothing with some linger time, but rather that once it is on the ground it will generally not offgas enough to be meaningful as long as you vacuum it up on a semi regular basis. My point was that if your garage has good airflow with the doors up you don't need to worry about air filtration.

Basically, throw on a respirator, grind your stuff, when you finish, vacuum up any mess (or use a dust catcher and a cyclonic with a water bucket), and pop the doors and let the air evacuate.

The particulate laden air will be gone in no time (I have cross flow through my garage - doors on both ends - and it is big, 2k sq ft, even with a wind speed of a couple of mph, you have achieved something in the 90s percentile of air replacement in a handful of seconds). In my case, if you leave the doors open for 5 minutes or so (assuming that you vacuumed first and the airflow isn't kicking up a ton more dust) the quantity of airborne particulate in the garage air (from the grinding, obviously there is particulate in outdoor air) would be measured a a probability of a single particle.

Based on the size of my garage and its doors, I can expect that a wind of 3 kts down the 'chute' as it were will give me about 53000 CFM of air movement. I have about 20000 cubic feet of volume in my garage. I (obviously) don't have laminar flow through the full garage or I would in reality be replacing the air totally in just under 23 seconds. Because of the turbulent flow, in reality, I will be replacing almost all of the air in that same period, but some of the process will essentially look like repeated dilution of small pockets of air. This is however all a technicality. I would guess that after 23 seconds, anything but the very most toxic of airborne agents would have reached harmless concentrations after even just 23 seconds. But we don't spray VX or similar into our garages, and I don't only give it 23 seconds, I give it a few minutes.

Some garages (most) don't have the cross flow that mine does, but the same general principle holds true. Air the thing out for a few minutes after you grind and vacuum and you have nothing to worry about.

I am not dumping on air purification and dust collection. They have their place (I have been considering air purification to go with my dust collection because I often have furniture finishes curing in the garage, and leaving garage doors open is not a good solution when you have still gummy finishes that you don't want to get dusty), but they are in no way required for safety in the way most knife makers work.

 

[googlebutt]

I've read on here that airborne particulates during wet hand sanding are less of a concerns, because the water traps the particulates. Assuming this is accurate, would adding a kool mist system to a grinder have a similar effect? I've seen sorrells use one in a tutorial, looks like the water is spraying directly on the contact point.

Edit: after some more reading, it seems like wet grinding, in combination with a spark bong/dust deputy rig might be just as, if not more effective in controlling the spread of dust through the air than dry grinding with any *affordable* dust collection system? Less fire risk as well.

 

[googlebutt]

If you want to protect your family from dust on a low budget, grind outside while downwind from the house and wearing your respirator. Once you bring the grinding inside, a dust collection system that will adequately collect the fine dust will probably cost more than the grinder did

Grinding metal can produce very fine dust that can hang in the air a long time and travel a considerable distance. Here's a cheap way to see if there's any floating in the air in your shop; get a "rare earth" (neodymium) magnet about 3/4" diameter or larger and 1/8" thick. Put it up on a wall somewhere in the shop far away from the grinder. Cut a piece of white paper about an inch bigger than your magnet and stick the paper to the magnet with double stick tape or glue, and look at the paper about once a week or so. If you never see a black spot on the paper over the magnet, congratulations, you either don't make fine dust in your work, or you have fabulous dust collection. Consider that the magnetic field lines only extend a few inches out from the magnet, so the dust on the paper is only the dust that was in an area maybe half the size of a grapefruit around the magnet. And this only catches steel, any silica/wood dust/aluminium/etc. will float on by...

Fine dust will settle, but it is very easy to stir up again. Any bit of breeze, or just walking through the shop is enough to get the fine dust moving. You can purchase a particle meter from Dylos and watch the effect for yourself.

I am not a fan of the hanging air filters for the following reasons, first, they are theoretically filtering out dust that you should have captured back at the grinder with your primary dust collection, and that's where the money should be spent. Second I have not seen a "shop air filter" yet that has a good enough filter to really capture the fine dust that is being stirred up by the fan in the air filter. Unless you have a MERV 15 or 16 (HEPA) filter in the unit the fine dust is just blowing through. Think about it, you wear a HEPA respirator to protect your lungs, why would you not clean the air in the shop to the same standard to protect yourself and your family when you travel through the shop without a respirator on?

M Mahoney I read through most of your posts regarding dust collection and I heavily value your advice. I'd like to get your thoughts on my proposed setup as a sanity check, I don't want to give myself a false sense of security.

This is my current setup, which I can push outside, wearing a respirator of course.

I just ordered a 2x72, so I need to upgrade my dust collection (or evacuation). I'll be building a new heavier duty cart for it, still on wheels, and ditching the cheap box fan for heavy duty industrial pedestal fan (pushing ~4,200 CFM like this). If I were to push my grinder against the wall there and set up the fan a few feet away to the right, do you think that's sufficient? I also plan on partitioning off that little corner from the rest of the garage with curtains. To me it seems very close to grinding outside, but with protection from the elements.

Old setup in location as a placeholder (that corner will be cleaned of all flammable materials ):

 

[Mahoney]

Save the money on the fan and spend it on a lean-to or Eze-up for protection from the elements outside. The fan is going to stir the air in the garage up, and if there's no corresponding garage door on the opposite side of the shop, the make-up air for what you are pushing out the garage door will have to come back in the same door. See the problem? How much of the fine dust stays outside will depend on the weather conditions at the time. The heavy dust will stay in the garage and make a mess. Dust collection is a complex process, and rarely can it be done both cheaply and effectively.

 

[googlebutt]

Save the money on the fan and spend it on a lean-to or Eze-up for protection from the elements outside. The fan is going to stir the air in the garage up, and if there's no corresponding garage door on the opposite side of the shop, the make-up air for what you are pushing out the garage door will have to come back in the same door. See the problem? How much of the fine dust stays outside will depend on the weather conditions at the time. The heavy dust will stay in the garage and make a mess. Dust collection is a complex process, and rarely can it be done both cheaply and effectively.

Thanks for the reply. I actually already have the fan in the mail, and I just got my Dylos pro to monitor things for what it's worth. Additionally, I scored a Vortex VTX800 8" inline fan for cheap on ebay, and I have a Wynn 13f230nano filter in the mail to construct Bill Pentz's 1000cfm MERV 15 air cleaner. I understand that air cleaners are essentially only good for reducing the time it takes for particulate levels to return to a safe level, but I went for it anyway. Seems like it's much, much better than any similarly priced air cleaner.

I was playing around with the idea of actually running a garage partitioning curtain along the entire length of the open garage door, except where I'll be standing, in an effort to keep dust from re-entering. This is probably wasted effort, but I figure it's worth a shot (MERV 15 air cleaner to deal with stirred up dust, fan to direct most of it outside). Of course I'll be wearing a my half mask with p100's, monitoring closely with my Dylos, and if it's unsafe I'll buy an easy up.

Couple more pics of the area, new tool stand will be on casters.

I'm also strongly considering buying a Jet 1100 (the only 1.5hp blower that Pentz recommends, has an efficient 11.5" impeller) and routing it directly out of that vent or through the window using 6" ducting, but I'm majorly concerned about sparks making it through. I also considered adding a super dust deputy in between, but with that comes the fire risk. Do you think that sparks can make it out of the system from the tool stand position, up and then out of the window? Will that short horizontal to vertical jog be too much to maintain 5,000 CFM at the point of creation? If venting directly outside, how would you rate the potential fire risk when sanding wood/steel in the same system?

 

[Mahoney]

The fire risk is 100% when grinding wood and steel in the same system. The same applies when mixing steel and flammable metal dust in the same system. While you might get lucky and never have a problem, dust collection and sparks are the fire trifecta. Lots of finely divided fuel, lots of oxygen, and an ignition source. The cost of a separate dust collection system for wood is a tiny fraction of the cost of a fire.

I can't answer a lot of your questions definitively, how far sparks can travel in a duct will depend on airspeed, and how laminar the airflow in the duct is. It can be many feet. Water mist spark suppression systems used in industrial dust collection systems usually require 20' of duct or more between the detector and the spray nozzle. I can tell you that in my tests, sparks can travel as much as 5' down a 6" duct after passing through a Nordfab spark trap, this is within design parameters. Some cyclones can be effective spark suppressors, if the airflow inside is turbulent enough

Venting outside solves a filtration problem, but look how close the window is to the garage door. With a breeze in the right direction, the fine dust will blow right back in the door. If you are blowing air out of the shop, air has to come back in somewhere. So don't count on a curtain helping much. Are you concerned about the grinding dust piling up in the yard? If so a cyclone will contain a lot of it, and may trap some sparks. Are you in a high fire risk area? If so, a spark suppressor of some sort would be a wise investment. Both the cyclone and spark suppressor will put additional load on your blower, so you will need a more powerful blower to get the 5000 FPM airflow in your duct. For a 6" duct that's 1,000 CFM, so a minimum of 2 Hp with a good impeller, Pentz would recommend 5 Hp

If you were going to buy a cyclone system for direct venting, the best "bang for the buck" right now would be the 2Hp or larger Grizzly. Steel impeller and reasonably efficient cyclone design. The filter is not worth using, and the collection drum is a bit big. If it gets full of grinding dust, you won't be able to pick it up and dump it... Obviously, don't use the plastic drum liners with steel grinding dust...

 

[googlebutt]

The fire risk is 100% when grinding wood and steel in the same system. The same applies when mixing steel and flammable metal dust in the same system. While you might get lucky and never have a problem, dust collection and sparks are the fire trifecta. Lots of finely divided fuel, lots of oxygen, and an ignition source. The cost of a separate dust collection system for wood is a tiny fraction of the cost of a fire.

I can't answer a lot of your questions definitively, how far sparks can travel in a duct will depend on airspeed, and how laminar the airflow in the duct is. It can be many feet. Water mist spark suppression systems used in industrial dust collection systems usually require 20' of duct or more between the detector and the spray nozzle. I can tell you that in my tests, sparks can travel as much as 5' down a 6" duct after passing through a Nordfab spark trap, this is within design parameters. Some cyclones can be effective spark suppressors, if the airflow inside is turbulent enough

Venting outside solves a filtration problem, but look how close the window is to the garage door. With a breeze in the right direction, the fine dust will blow right back in the door. If you are blowing air out of the shop, air has to come back in somewhere. So don't count on a curtain helping much. Are you concerned about the grinding dust piling up in the yard? If so a cyclone will contain a lot of it, and may trap some sparks. Are you in a high fire risk area? If so, a spark suppressor of some sort would be a wise investment. Both the cyclone and spark suppressor will put additional load on your blower, so you will need a more powerful blower to get the 5000 FPM airflow in your duct. For a 6" duct that's 1,000 CFM, so a minimum of 2 Hp with a good impeller, Pentz would recommend 5 Hp

If you were going to buy a cyclone system for direct venting, the best "bang for the buck" right now would be the 2Hp or larger Grizzly. Steel impeller and reasonably efficient cyclone design. The filter is not worth using, and the collection drum is a bit big. If it gets full of grinding dust, you won't be able to pick it up and dump it... Obviously, don't use the plastic drum liners with steel grinding dust...

Totally understand what you're saying about the fire trifecta, I've totally nixed the idea of mixing media in any dust collection that I do. If I end up going with a blower and cyclone, I'll only be using it for steel, as that's the bulk of what the grinder will see, and wheel the grinder out in the backyard for handles (I only use wood). I feel much better about a degradable substance like wood in the yard, as opposed to steel.

Regarding the window, there's actually a fence and a gate on that side of the house. Not sure how effective that will be in disrupting the airflow, to be quite honest.

From my research, I figured the Grizzly didn't have enough grunt to reach that 5000 FPM/6" duct sweet spot with anything other than direct venting (no filters or cyclones). By cyclone, are you referring to something like a dust deputy? The only cyclone I can find with 6" inlets is the plastic super dust deputy XL, otherwise I'd have to get the metal version which as a 5" inlet and a 6" outlet and use this short reducer. Would you be reasonably confident that the 2hp Grizzly, combined with that dust deputy and 6" ducting would get me to that 5,000 FPM zone?

If I do go this route, I was also considering routing the ducting out the window and into a metal trash can. At the end of the session, I'll just yank the duct back inside and close everything up.

Thank you again, it seems as if you're taken Bill Pentz's ideas and adapted them specifically to our needs, and tested them in the real world.

edit: Do you think that adding water to the container that the dust deputy is installed on will help reduce sparks down the line?

edit 2: The 2hp Grizzly isn't 110v, so I'll have to go for the JET DC-1100, Delta 50-676 (first two recommended by BP) or this Shop Fox W1685

 

[Mahoney]

The caveat: Don't expect to build the same system we did and have the same results. Do it wrong and it might blow up. It works for us safely on our machines and processing mostly mild and some hard steel. I did fairly extensive testing before committing to the install

The Grizzly cyclone systems we are using in the metal working area are the G0440. This is an "off label" use as far as the manufacturer is concerned. Metal dust is mentioned in the manual, along with a lot of other things, as material the system should not be used with. The fan curve shows over 1200 CFM in 6" duct. Our duct runs are short, about 10' to the grinders, with a Nordfab spark trap inline, back pressure about 2" H2O IIRC. This should put airflow at about 1,000 CFM. I don't have any settled dust in the horizontal portions of the ducts when I've opened the spark traps for cleaning. We return the air to the shop, so have custom made MERV 15 flame retardant filters, about 500 sq ft. of media for each system to minimize back pressure. Now perhaps you understand my comment that the dust collection system can cost more than the grinder

I don't think any blower pulling less than 20 amps at 110 volts will be able to move enough air to really get the fine dust at the air speeds you need for metal grinding dust. I've wasted some money on less than 2 Hp blowers, and not been satisfied, YMMV An exception might be a shop vac connected to a portable power tool with a really well designed hood.

A smaller system can get the "dirt" and with care you should be able to engineer something that will move air at 5000 FPM. Water filled "spark bongs" work for a lot of folks, and some commercial systems use a water or other fluid filled stage for spark suppression. I prefer to avoid the water because it comes with a bunch of work related to avoiding bacterial and fungal contamination. But if you are not getting the fine dust, grinding outside downwind of the house while wearing your respirator is still going to be safest for your family.

 

[googlebutt]

The caveat: Don't expect to build the same system we did and have the same results. Do it wrong and it might blow up. It works for us safely on our machines and processing mostly mild and some hard steel. I did fairly extensive testing before committing to the install

The Grizzly cyclone systems we are using in the metal working area are the G0440. This is an "off label" use as far as the manufacturer is concerned. Metal dust is mentioned in the manual, along with a lot of other things, as material the system should not be used with. The fan curve shows over 1200 CFM in 6" duct. Our duct runs are short, about 10' to the grinders, with a Nordfab spark trap inline, back pressure about 2" H2O IIRC. This should put airflow at about 1,000 CFM. I don't have any settled dust in the horizontal portions of the ducts when I've opened the spark traps for cleaning. We return the air to the shop, so have custom made MERV 15 flame retardant filters, about 500 sq ft. of media for each system to minimize back pressure. Now perhaps you understand my comment that the dust collection system can cost more than the grinder

I don't think any blower pulling less than 20 amps at 110 volts will be able to move enough air to really get the fine dust at the air speeds you need for metal grinding dust. I've wasted some money on less than 2 Hp blowers, and not been satisfied, YMMV An exception might be a shop vac connected to a portable power tool with a really well designed hood.

A smaller system can get the "dirt" and with care you should be able to engineer something that will move air at 5000 FPM. Water filled "spark bongs" work for a lot of folks, and some commercial systems use a water or other fluid filled stage for spark suppression. I prefer to avoid the water because it comes with a bunch of work related to avoiding bacterial and fungal contamination. But if you are not getting the fine dust, grinding outside downwind of the house while wearing your respirator is still going to be safest for your family.

Good points, I'm out of room in the breaker box, so I'll have to get a quote on that and a 240 circuit.

I reread bills site and I forgot he had suggested one of those drum mounted units for the guy who asked specifically about collection for grinding metal on a 2x72. I found a dayton at a reasonable price point that pretty much ticks all the boxes, except it has a 5" inlet. It makes a lot of sense since I was planning on venting outside anyway. I'm thinking I can just plop it right under that window. Is something worth exploring?

https://m.grainger.com/mobile/product/DAYTON-Dust-Collector-3AA17

Edit: disregard, this isn't really suitable for hot material, unless I take the bag off.

 

[Mahoney]

It's a 1.5 Hp unit, that 1100 CFM rating is probably without any duct and maybe without the drum attached. 5,000 FPM in a 5" duct is 700 CFM, so it will probably keep the dust moving if you vent it directly to outdoors, but I doubt you will have the 1,000 CFM you should to get the fine dust

 

[googlebutt]

It's a 1.5 Hp unit, that 1100 CFM rating is probably without any duct and maybe without the drum attached. 5,000 FPM in a 5" duct is 700 CFM, so it will probably keep the dust moving if you vent it directly to outdoors, but I doubt you will have the 1,000 CFM you should to get the fine dust

Would it then be wise to go with a 5" ducting rather than 6" if I go with that shop fox unit/dust deputy combo, considering I'm venting straight outside? I'm going to design the ducting to be as short and horizontal as possible, so I thought it might be worth potentially sacrificing velocity for more cfm at the point of creation by going with 6". Might just be a wash with this level of equipment, just trying to be smart about what I can afford.

 

[googlebutt]

M Mahoney I have a quote out to have my unused 10-30 outlet converted for the 3hp grizzly unit. I found some assets in sketchup that I've been playing around with. I was curious if you had any thoughts on this duct routing? I'm trying to figure out how to eliminate as many bends as possible. Everything is roughly to scale. The cost of metal tubing for this ultra short configuration make me want to barf!