Thread: Dust extraction cupboard - ideas?

Dave,

Actually, it is cheap and easy to reduce the noise level to under 65 dB, so don't let noise stop you at some time in the future. Also, in Australia most of these units run from a 240 V supply using a VFD to drive a 3 phase motor. That gives us a 60 Hz supply to the motor which increases the motor speed and air flow by 20% compared to a normal 240 V motor.

Have fun!

Thanks for all the discussion and advice guys. I have plenty of ideas lined up to try out... there's just never enough hours in the week to try them all out though! I did do a search on a few U.S. woodworking forums last night and it seems quite a few people have tried venting their fine dust outside, including one person who removed the bags completely from his 2HP DC. He just used the dust collector motor to suck the sawdust through a Thien separator and then what was left went outside. Not the sort of setup you would use in a suburban environment but on a 5 acre block with plenty of farm land here it may be worth trying. I'm aware of the potential for the motor to overrun and possibly overheat with that arrangement but that's for another thread discussion on here.

I'm still curious to replace the top filter bag with a large plastic drum and then connect a outlet to the top of it for a vent outside. I'll get the dust collector first and get it up and running for a while before going any further with this idea. At least that will provide a slightly healthier environment than I have at the moment and get me started again with a few projects. Just gotta remember to wear the respirator...

cheers
Dave

Originally Posted by Dave32

Thanks for all the discussion and advice guys. I have plenty of ideas lined up to try out... there's just never enough hours in the week to try them all out though! I did do a search on a few U.S. woodworking forums last night and it seems quite a few people have tried venting their fine dust outside, including one person who removed the bags completely from his 2HP DC. He just used the dust collector motor to suck the sawdust through a Thien separator and then what was left went outside. Not the sort of setup you would use in a suburban environment but on a 5 acre block with plenty of farm land here it may be worth trying. I'm aware of the potential for the motor to overrun and possibly overheat with that arrangement but that's for another thread discussion on here.

It wouldn't matter where the workshop was or whether a DC is going to be vented outside or not using ANY chip collector, Thien separator or small cyclone on a small DC will rob sucking power/flow from systems that are already stretched at achieving the required CFM to capture fine dust at source.

I'm still curious to replace the top filter bag with a large plastic drum and then connect a outlet to the top of it for a vent outside.

All that will happen is you will get a volcano of medium to small visible saw dust spewing out of the vent.

I'll get the dust collector first and get it up and running for a while before going any further with this idea. At least that will provide a slightly healthier environment than I have at the moment and get me started again with a few projects. Just gotta remember to wear the respirator...

You seem to be focussing at the wrong end of the DC. The DC will have more than enough flow at the back end with conventional bags or filters if they are kept clean. Removing these will do nothing for flow at the front end unless 4" ducting and inlets are replaced with 6" versions. Then if you remove the bags you run the risk of over running the motor.

During my measurements of dust in sheds and DC devices if there is one elephant in the corner emerging, it is that no-one can ignore regular servicing (checking for leaks and cleaning filters) of their DC systems. To minimize the effect of undetected leaks developing in between servicing the best location for all systems is outside the shed. When I first looked into woodwork dust I thought that filter efficiencies would be the main contributor to dust levels in a shed. Instead the main reasons are collection at source and DC leaks.

It sounds like the cyclone separation method requires the air to travel around the top bag in a circular motion while at the same time being dissipated through the filter bag, and as you say, putting a single vent in the top of the drum will just force the saw dust straight up and out.

I do also understand that if you increase the size of the input duct and then remove the bags it would burn the motor out, so I won't be trying that. My main concern was the dust being passed through these Chinese made 4 micron filter bags and into the working environment again, which was the original idea of putting the DC into the cupboard. Then I read elsewhere that doing that can build up fine dust inside the cupboard, making it a possible hazard every time the bag is changed. Now you say that dust in the workshop is mainly from barely adequate CFMs at the collection point and leaks... hmmmm....

Without proper measuring equipment it sounds like I will be wearing my respirator at all times because how can you possibly tell it is safe otherwise? A fine build up of dust in the workshop over time would be the only indication that the system needs upgrading or tweaking and so without the measuring gear that's about my only option right now.

Originally Posted by Dave32

It sounds like the cyclone separation method requires the air to travel around the top bag in a circular motion while at the same time being dissipated through the filter bag

This is a minor point but air passing thru the bag is not a requirement for cyclonic action. Cyclonic action is air moving in a circle concentrating the heavier particles on the outside of the circle and lighter ones in the middle. On a two bag generic DC system there is a downward sloping partial annular divider between the bags - air is injected into the bottom bag in a circular motion so more of the bigger particle end up in the bottom bag and the excess air then moves up through the middle of the divider into the top bag (not much circular motion happens in the top bag) and the air then dissipates out through the bag

, and as you say, putting a single vent in the top of the drum will just force the saw dust straight up and out.

Correct

I do also understand that if you increase the size of the input duct and then remove the bags it would burn the motor out, so I won't be trying that. My main concern was the dust being passed through these Chinese made 4 micron filter bags and into the working environment again, which was the original idea of putting the DC into the cupboard.

Which bags are you referring to? If you refer to the 5 micron needlefelt bags, they are every bit as efficient at fine dust collection as the most expensive pleated filters. The big advantage of pleated filters is they do not need to be cleaned as often and so maintain max flow for longer. As the flow drops, then less fine dust is collected at source.

Then I read elsewhere that doing that can build up fine dust inside the cupboard, making it a possible hazard every time the bag is changed.

Even if it happens (see next paragraph) this is a bit of a red herring. Long term total exposure is what really matters and this is equal to concentration x time. Concentration may be high but time is small compared to the time spent working in a shed. To reduce the risk even more I do wear a mask when changing bags. I must do an actual measurement next time I change my bags to see what the actual exposure levels are.

If a DC is well maintained, the reality is the wood dust concentration in the cupboard where a DC is located will not be that high. In fact the CLEANEST space on average in my shed for dust, is the cupboard my DC is located in. This is because the needle felt filters are so efficient and I keep them clean and I have no identifiable leaks. Like I said earlier the main issue with external location of DC appears not to be a problem with bag/filter efficiencies but leaks and poor collection at source.

Now you say that dust in the workshop is mainly from barely adequate CFMs at the collection point and leaks... hmmmm....

Correct. Even if it looks like a setup is visibly collecting all the dust it probably isn't.

Without proper measuring equipment it sounds like I will be wearing my respirator at all times because how can you possibly tell it is safe otherwise? A fine build up of dust in the workshop over time would be the only indication that the system needs upgrading or tweaking and so without the measuring gear that's about my only option right now.

Even though I have a Triton full flow respirator I really dislike using it and any face mask and only wear them when I know dust capture at source is performing poorly. Instead I prefer and promote the running of a DC for some time after the last dust making activity. The dirtier and the longer the dust making activity the longer I run the DC for after the last dust making activity. My experiments show that fine dust has a half settling time of ~20 minutes in a closed shed with no DC running. If you want to reduce the fine dust down to 10 times it's starting value then theoretically 10 x 20 min = 200 minutes is required. However, if the DC is kept running and the shed has good ventilation then this can be brought down very quickly. FOr example, an open doorway and a big DC can bring the levels down in minutes instead of hours. A roller door and a window will do wonders for dust levels in a shed. These are cheap solutions available to most woodworkers in Oz but now always for folks in colder climes.

Dave,

As always, BobL makes good sense. My shop was an unmitigated dust disaster until a few months ago. We can never eliminate dust, but we can sure reduce it dramatically.

I am currently overseas. When I get home I am sure to find a slight layer of dust over my shop ... and in my bedroom and kitchen and lounge. Wood dust is my real problem, not dust generally, which is everywhere.

Because I have good airflow, hoods that do a good job of capture at the source and no filters/leaks, and because I run the cyclone for a while after making wood dust, it is likely that my dust collection is close to as good as it is ever going to be. Not perfect, but so low that I need not be concerned about total exposure. For our health, it is total exposure (concentration X time) to the very fine (invisible) dust that counts.

I started out trying to keep my shed cleaner, but finished by looking after my health. As matters stand the biggest dust producers in my workshop are now hand tools like drills. If that is my biggest problem, I can live with it.

Been busy lately so sorry about the late reply... Some really good advice there Bob, thanks once again for the information. You sure know your stuff. I've been reading up on dust extraction now for a few weeks and I've gone through dozens of web sites but I've probably learned most from this forum.

Wandering slightly off this discussion slightly but I've been looking at all the 2HP 2 bag collectors available here in NZ lately and decided to take a look at the local tool shop where they have one in there. All these 2 bag collectors look almost identical in their design and after looking at the build quality and being slightly disappointed I decided after much thought to go and spend a little more and get the Jet Vortex model. 1200 CFM as opposed to 1500 CFM on some of these others, but I'm a little wary about the specs anyway as the "FM-300" has been listed as either 1200 or 1500 CFM from quite a few tool shops. Which one do you believe? I know 1200 is barely adequate but space and money are a little limited and it's a compromise.

I'll go ahead and get it setup and then start considering the dust cupboard design with ventilation outside. I found a great thread here with lots of photos so I'll base it on that as well as everything we've discussed here. You're right Bob, the exposure to dust vs. time when accessing the cupboard would be minimal, especially wearing the respirator. I also have a respirator on the way having decided on the 3M full face model. Currently using a Fuller mask but I'm not convinced it's completely safe.

Having a 2 car garage with a door and window at the back is a great environment for flushing the workplace out too, especially if there's a good breeze. Not having any dust measuring equipment makes it challenging to decide if the workplace is safe enough to go without a mask so I'll probably have to wear it most of the time but it's relief to know that with both the DC running and all doors open it's likely to be 'reasonably' clean in there. Come Winter that will change though.

I do get quite a build up of dust in the garage so it's also going to be challenging to decide if it's originating from the woodworking or from elsewhere. I'm glad my garage is away from the house John, as having wood dust in the lounge, kitchen and bedroom would be a real hassle!

Originally Posted by Dave32

Been busy lately so sorry about the late reply... Some really good advice there Bob, thanks once again for the information. You sure know your stuff. I've been reading up on dust extraction now for a few weeks and I've gone through dozens of web sites but I've probably learned most from this forum.

Thyanks

Wandering slightly off this discussion slightly but I've been looking at all the 2HP 2 bag collectors available here in NZ lately and decided to take a look at the local tool shop where they have one in there. All these 2 bag collectors look almost identical in their design and after looking at the build quality and being slightly disappointed I decided after much thought to go and spend a little more and get the Jet Vortex model. 1200 CFM as opposed to 1500 CFM on some of these others, but I'm a little wary about the specs anyway as the "FM-300" has been listed as either 1200 or 1500 CFM from quite a few tool shops. Which one do you believe? I know 1200 is barely adequate but space and money are a little limited and it's a compromise.

For all practical purposes it doesn't matter what the claimed flow rates are. If you use 4" ducting the most you will get is ~420 CFM. If you use 6" ducting the most you will only get is ~1250 cfm

I'll go ahead and get it setup and then start considering the dust cupboard design with ventilation outside. I found a great thread here with lots of photos so I'll base it on that as well as everything we've discussed here. You're right Bob, the exposure to dust vs. time when accessing the cupboard would be minimal, especially wearing the respirator. I also have a respirator on the way having decided on the 3M full face model. Currently using a Fuller mask but I'm not convinced it's completely safe.

Correct

Having a 2 car garage with a door and window at the back is a great environment for flushing the workplace out too, especially if there's a good breeze. Not having any dust measuring equipment makes it challenging to decide if the workplace is safe enough to go without a mask so I'll probably have to wear it most of the time but it's relief to know that with both the DC running and all doors open it's likely to be 'reasonably' clean in there. Come Winter that will change though.

Goo ventilation is your best friend

I do get quite a build up of dust in the garage so it's also going to be challenging to decide if it's originating from the woodworking or from elsewhere. I'm glad my garage is away from the house John, as having wood dust in the lounge, kitchen and bedroom would be a real hassle!

It sure would.

Dust build up is a strong indicator that dust is not being collected at source which is caused by insufficient flow at source.