Filter or cyclone?

[Afro Boy]

I currently have a H&F DC3 dust extractor (2HP, 1200CFM) and am looking for the next upgrade to it. Before I go ahead and build in some piping through the workshop, I thought I should address the efficiency of my extractor. If I could only do one right now, which would it be, add a filter, or build a cyclone?

I don't have a ready way to expel any air outside of the garage (unless I just keep the garage door open) so this may restrict the possibility of using a cyclone.

Am keen to increase the efficiency (in terms of dust collection) but also to ensure I'm not spewing fine dust everywhere, including in my lungs.

Any thoughts?

Cheers,
Af.

[Afro Boy]

Forgot to mention, I've been reading this page: http://billpentz.com/woodworking/cyc...conversion.cfm

If I go down the filter route, anyone know where I can get the filters Bill Pentz is talking about locally (Melbourne)?

Thanks,
Af.

[johnredl]

Watching with interest

[BobL]

By filter I presume you mean a pleated filter?
If so a pleated filter will decrease the back pressure on the DC enabling more flow. Being a greater surface area than a filter bag it should also stay cleaner for longer. This is worth doing but you will still have to regularly clean the filter and you must empty the back otherwise within 5 minutes of switching on the DC the filter will be back to where it was before it was cleaned. But there are far better ways to collect more dust than this, read on.

And by cyclone I presume you mean add a cyclone to the 2HP DC.
Adding a cyclone to something like a generic 2HP DC will be a waste of time because it will increase the back pressure substantially and hence reduce the flow at source, it won't filter the very fine dust of air all that well, and it will (as you say still need a filter). An efficient cyclone is not something you add to a DC but is built from the ground up to incorporated the impeller in the body of the cyclone.

If you want to improve the dust collection performance of your 2HP DC look at what I did in this thread.
https://www.woodworkforums.com/showth...generic+2HP+DC
The mods clearly demonstrate how flow rates on these can be improved.

You can expel the air out of a DC through a garage door. Just make sure you block any other gaps up so the air containing the very fine dust is not sucked directly back in through the gaps.
I assume you have another opening on an opposite wall that will allow fresh air to be drawn into your shed. If not you are stuffed.
You will still need to put the DC in an enclosure and vent that out of the door - do you understand why?
What sort of a door is it?

[Afro Boy]

Thanks heaps for that Bob. Ok, have done a whole heap of reading now and am thinking the following might be a good improvement for my system.

• Pleated filter to replace the cloth standard bag
• Move the impeller and motor up level to the bag inlet as per your other thread
• Increase the inlet size to 6"
• Increase outlet sizes on my machines where I can (tablesaw can be done, but thicky/jointer might be a problem)

Two questions ...

1. I read that you put a flange on the inlet pipe as it faces the impeller. Was that done on the melamine/mdf plate or does the pipe itself flange once it gets past the hole?

If it's on the attachment plate itself, does this look like what you've done?

flange.png

2. If there's no real benefit to be gained by converting this to a cyclone (as the motor isn't powerful enough), then there's no need to vent anything outside, correct?



To answer your questions Bob:

You will still need to put the DC in an enclosure and vent that out of the door - do you understand why?

If I have a cyclone, then the finest dust should be vented outside. I would need to enclose the DC because any dust escaping it would just be cycled back into my workshop. Is that the theory?


What sort of a door is it?

Where my dusty sits, it's next to the large roller door. Aside from removing a few bricks near one of the other walls or venting into the roof cavity, not sure it's really doable in that position. See (wonky) pic of the layout:
garage.jpg

Cheers,
Af.

[Evanism]

AF, I'd be inclined to fix your localised time/space distortions first. Looks like you might have an errant black hole somewhere near.

BobL is excellent, but he will tell you to put it all into a cabinet and vent that cabinet to the outside. Punch out a few bricks and make a nice neat hole and shroud it. His ideas are excellent, low cost, entirely practical and very do-able. Makes cold winters very problematic if you want a warm workshop....

With the ability to seal near the door and have another source of air, it unless you have a window at the back open, that big machine is trying to pump 1200 cfm of air out of your shed! The air has to be replaced from somewhere and garage doors are terrible... air gaps the whole way round. You'll just be sucking all that fuggy air right back in. Bad.

This might not be an authorised method, but Bunnings and Clarke Rubber sells this spongy foam with a strip off sticky backing. I use this all around and it seals it well. Ive also been playing with large sheets of magnet (from a printer) cut into strips and also placed on the sides (my door is all metal and not a roller door though). This is almost air tight.

Ive also been playing with the sheet magnets to seal the table saw and jointer. Seal is the wrong word, more move them so the suction creates a scavenging vortex in the cabinet to keep it absolutely clean. My table saw accumulates sawdust on the bottom if I dont, which proves the 2HP isn't enough (but is my restriction due to power)

[Afro Boy]

AF, I'd be inclined to fix your localised time/space distortions first. Looks like you might have an errant black hole somewhere near.

It's just a science experiment of mine. Nothing to worry about, nothing to see here, she'll be right.

BobL is excellent, but he will tell you to put it all into a cabinet and vent that cabinet to the outside. Punch out a few bricks and make a nice neat hole and shroud it.

I understand the theory is to allow anything which passes through the pleated filter to be vented outside and not back inside the workshop. Where the extractor is placed at the moment, I would have to run the venting pipe a few metres to get it to a wall. I would imagine that could create an issue, yes?

Then I have the issue like you described, if I vent out near that garage door, the gaps in the door will just suck it right back in. I often work with that door wide open too so that in itself will cause an issue. Looks like I may have to rethink my whole layout.

Ive also been playing with the sheet magnets to seal the table saw and jointer. Seal is the wrong word, more move them so the suction creates a scavenging vortex in the cabinet to keep it absolutely clean. My table saw accumulates sawdust on the bottom if I dont, which proves the 2HP isn't enough (but is my restriction due to power)

That's a good idea. How have your experiments been working? Do you feel they make a difference?


For the moment, I'm looking for the one or two things I can do now to make a difference. It's not going to be perfect, but it will be better than it currently is. Eventually (with funds and time) I'll look to do more and more.

Cheers,
Af.

[Evanism]

It's just a science experiment of mine. Nothing to worry about, nothing to see here, she'll be right.

I understand the theory is to allow anything which passes through the pleated filter to be vented outside and not back inside the workshop. Where the extractor is placed at the moment, I would have to run the venting pipe a few metres to get it to a wall. I would imagine that could create an issue, yes?

Probably one for BobL, but reason would have me thinking so. He always bangs on about minimum length. Longer = friction/losses. Im pretty sure he would have quantified it in the above thread.

Then I have the issue like you described, if I vent out near that garage door, the gaps in the door will just suck it right back in. I often work with that door wide open too so that in itself will cause an issue. Looks like I may have to rethink my whole layout.

Could you put in a chimney? A second hand one? Push it straight out the roof?

Ive been sort of thinking about this myself. A mate of mine is an enviro-dude and he asked why I wouldn't use my waste to heat the shed.... ummmm.... a little pot belly in the corner would be nice Esp in Canberrrrraa in the winter! One could also make briquettes out of the bagged sawdust.

I sealed the shed so I could also run a small aircon efficiently. In summer it always hits 36 degreess and 43 is not uncommon. That heat is unreal to work in.

That's a good idea. How have your experiments been working? Do you feel they make a difference?

HUGE. I took the time to do this with the bandsaw (its covered in another thread), did the under-table router box (which is 100% perfectly clean and I do a LOT of routing) and started with cardboard and packing tape on the tablesaw. There is a huge gap under the top and the cabinet, big holes where the raiser and tilter winder are and the cabinet cover for the motor also has louvers.

The cardboard is ugly and moving it around to get the best effect was troublesome.

The genesis of the idea came from a Laguna(?) or SawStop saw cabinet picture where they had some plastic doodad under the blade to deflect the crud towards the dust port rather than spray it all over the arbors/etc. The next a-ha moment was when I built my undertable router cabinet. Nice and airtight except for the router bit hole. Bzzzzt. Router hot, suction low, DC straining.... so I grabbed my 25mm forstner bit and placed 4 holes in the cabinet... 2 at the back-bottom, one in the top-back-right and one in the front-bottom-left. This, in my mind, sort of came close to an additional 8000 square mm of air, plus the hole in the top. This allowed the DC to maintain a good hard suction (dust is sucked 10cm away from the bit!!!) but importantly made the inside of the box into a vortex. It is sterile clean. Router is cool to the touch after a flogging and Im satisfied the noise is "reasonable". Importantly, zero dust after routing...no clean up!

My Table saw is a bugger. Dust gets in the winding mechanism and over time gets really stiff. I get the air hose, turn on the DC and fire a good blast down the insert hole and scavenge it all out. It swirls around and takes maybe a minute to clean it all right up... bit of WD40 or machine oil on the winder and problem is solved for another month. This made me think... hmmm, why not do the same as the router?.....bigger problem as its all metal, so I tried the carboard trick and it sort of worked, but made winding the up/down/angle handles a hassle as the tilt wants to move.... fridge magnets are too small, so I sourced a roll of the stuff!! Cut with scissors, made a cover for the winders and slip the magnets in long bits up under the skirt top.... works well!!!

Just need to think about an internal mechanism to create more swirl... but I think this is minor and just experimentation with some cardboard and tape.

For the moment, I'm looking for the one or two things I can do now to make a difference. It's not going to be perfect, but it will be better than it currently is. Eventually (with funds and time) I'll look to do more and more.

Cheers,
Af.

This sport can bleed you dry.....

[BobL]

[QUOTE=Afro Boy;1800365]

Two questions ...

1. I read that you put a flange on the inlet pipe as it faces the impeller. Was that done on the melamine/mdf plate or does the pipe itself flange once it gets past the hole?
If it's on the attachment plate itself, does this look like what you've done?[QUOTE

I put the curved edge on the melamine/mdf and the turned a recess in the front of the melamine/mdf so the inlet pipe sat flush inside the recess so the inside of the pipe was level with the start of the curved edge.

2. If there's no real benefit to be gained by converting this to a cyclone (as the motor isn't powerful enough), then there's no need to vent anything outside, correct?

There is just a much reason as all DCs and bags leak. These leaks can be WAAAAY worse than the stuff that goes through the filter. The only way you could be guaranteed of no leaks would be to have a particle counter to check the bag to bag housing seal, even the smallest ruck in the seal will leak - its just easier to ben the DC outside than it is to check for leaks.

You will still need to put the DC in an enclosure and vent that out of the door - do you understand why?
If I have a cyclone, then the finest dust should be vented outside. I would need to enclose the DC because any dust escaping it would just be cycled back into my workshop. Is that the theory?

Yep

What sort of a door is it?

Where my dusty sits, it's next to the large roller door. Aside from removing a few bricks near one of the other walls or venting into the roof cavity, not sure it's really doable in that position.

OK with a roller door what you do is make up a 200mm wide panel that fits right across the width of the door and cut a 150 mm hole in that at a convenient spot. If it's your roller door you could even bolt the panel onto the door. Put the whole DC inside an enclosure in the shed and vent the cupboard via some ducting out through the 150mm hole. I have seen a real nice panel that was made of sheet metal and a light angle iron frame, the outside of which matched the colour of the roller door and, like the roller door, was fully lockable.

If the roller door your only ventilation? If it is, my suggestion is not possible

[Muchacho]

Hi Afro Boy,

Good on you for looking to improving your extraction setup.Having been through this exercise myself building a 2HP cyclone (see fibreglass cyclone project ) I appreciate the work involved and the many difficult decisions to bemade. Hopefully the following will provide some of the information requested and provide some balance to some of the opinions given by others.

• You will not be wasting your time with a 2HP cyclone. It may be underpowered, but providing it is well built and exhausted outside, it will be better than what you currently have.
• Testing my system showed that it had similar airflow performance to Bob’s modified dusty. From this I concluded that a well built cyclone will cause no more restriction to air flow than the filter bag it will replace.
• The small volume of dust exhausted will be almost be undistinguishable. I’ve been running mine for over a year now and the only sign of dust outside is a slight buildup of very fine dust on the louvers of my exhaust box.
  
• One of the key decisions to be made will be where to locate the cyclone (or dusty enclosure)to best suit your machine layout, shed structure, external receiving environment and to reduce ducting losses,
• I reckon people overthink the makeup air issue. Unless your exhaust is right next to an open door, with the air leaving is your shed at a high velocity the amount of mixingis such that the concentration of fine dust drawn back into the sheet will be very low. It will be significantly lower than the amount of fine dust that your dusty currently circulates every time you turn it on.
  
• Building a cyclone system with the fan you already have is a low cost upgrade. It will not provide the sort of airflow that the experts say is necessary but it will be a worthwhile improvement. Provided the cyclone you build now is of suitable design (see Bill Pentz website), it would be easy to upgrade to a larger fan later if you findyou need more flow.
  
• Consider upgrading now to a 3HP fan. I’m not sure what your local second hand market is, but there may not be much difference between the sell price of the 2HP vs buy cost of a 3HP. This will also leave you with an operational dusty while you build yournew cyclone.
  

Key things to remember will be to upsize your machines ports to 6” and to minimize the amount of flex and fittings on your duct runs. Looking at your shop layout, you could have a few metres of ceiling mounted rigid, followed by a large radius bend and a couple of metres flex dropper that you hook individually to each machine as required. For a small fan, individually plumbing each machine will probably cause too much pressure loss.

Regards, Tim

[BobL]

• I reckon people overthink the makeup air issue. Unless your exhaust is right next to an open door, with the air leaving is your shed at a high velocity the amount of mixingis such that the concentration of fine dust drawn back into the sheet will be very low. It will be significantly lower than the amount of fine dust that your dusty currently circulates every time you turn it on.

The high velocity makes very little difference as air velocity drops dramatically over just a metre or so of distance from the outlet and while the initial ejection is rapidly diluted, depending on the variables discussed below, over time the total concentration of dust ejected can build up to be greater than what is being ejected from the DC

I did a few tests on this a few months ago but have not reported on these because I was hoping to get some more specific results but the guys at the uni needed the particle counter back so I haven't done any more.

These tests are quite difficult to do because the wood dust is mixed in with a lot of "other dust" and the the "other dust" varies significantly over time.
There are also many variables to deal with and test ; e.g. the amount of air involved, amount of fine dust being emitted by the DC, the geometry/size of the space the dust is being ejected into, how wet/hunid and how windy it is, the direction of the wind, height of the ejection point above the ground, and the length of time the DC is run for.

To test this I put the naked generic 2HP outside my shed about 3m away from the main door to my shed and ran ducting back inside the shed. The space the DC was venting into was our small (~10 x 10 m) back yard between the shed and the house. It was a fine still day and took ~4 minutes to detect any additional dust coming back through the door. One problem with doing this test is because the DC is not totally enclosed I could not measure the total emission of dust by the DC (remember all DCs leak so to measure their total emission they need to be inclosed and have a single outlet]. The dust levels of the return air over time varied up and down but overall it continued to increase slowly over the test period of about half an hour. I then decided that the neighbours had heard enough noise and I stopped the test (I have issues with our neighbour and his garden blower so I always try to do the right thing noise wise). I need to do some more testing when the neighbours are not around.

I can also report on the following which I have tested several times with varying speed winds. My DC enclosure vents at ground level into a 10m long x 1m wide alley/gap between my shed wall and my neighbours 1.8m high fence. On a very still day the concentration of fine dust in the alley can reach levels above that coming out of the DC. The DC enclosure vent is 1m away from a door in the shed that I use to access the alley and even on a breezy day, with the door open it only takes a minute for the fine dust to be detected coming back in though the open door and within about 5 minutes the return air through the door is as dusty as the air being vented at the enclosure. This is why I keep this door closed.

One thing I think will make some difference is if a chimney is used. The air coming out of a DC is usually slightly warmer than then even the slightest breeze will carry away the fine dust.

[Afro Boy]

Ok, so have absorbed even more info on this. In order, here's what I'm thinking:

1. Conversion
This looks reasonably straight forward and I hope to get it done in the next week or two over a few nights. This would involve building a new frame, making some new openings, moving the motor/impeller, etc.


2. Ducting
Where the extractor is now, I have a straight run of 2.5m to the tablesaw and it can all run on the ground.

If I move the extractor out of the way to the side wall, I'll have a 5.5m run to the tablesaw which will need to go up the wall, across the ceiling, down to the floor, and across to the tablesaw outlet. No doubt this will have a bit of an impact. How much, I'm not so sure. Is it worth worrying about?


3. Pleated filter
Any thoughts or recommendations for where I might get a good quality yet reasonably priced one to suit this extractor? I'm in Melbourne. What should I be looking out for?


4. Boxing
Building a box to contain the whole extractor unit. How do people get to the on/off switch or is it usually moved outside? What about changing bags and seeing when it's full? Anyone used a plexiglass/plastic wall on one of these?


5. Venting
With a box, I'll need to vent. Looks like it will be through the ceiling/roof. The garage door is often open so that's out of the question (no point if the dust will just blow back in). The back wall is out because that's where our patio is. The two side walls are out because one is the neighbours house and the other is a bedroom!

Now looking at options for getting a flue put in with a roof cowl. This should let the fine dust travel off with the wind. Going to be a bit of work to go through the ceiling, tiles, etc.

Is venting in this way without a cyclone an issue?


6. Cyclone
Eventually, I should build a cyclone system. With the ductwork, box and vent in place, this shouldn't be too difficult to retrofit.



Am thinking I'll do 1 - 3 in one bout. Then wait until I have some more funds to do the boxing and venting. That would give me most of what I'm after.

Thoughts, theories, criticisms?

Cheers,
Af.

[BobL]

2. Ducting
Where the extractor is now, I have a straight run of 2.5m to the tablesaw and it can all run on the ground.
If I move the extractor out of the way to the side wall, I'll have a 5.5m run to the tablesaw which will need to go up the wall, across the ceiling, down to the floor, and across to the tablesaw outlet. No doubt this will have a bit of an impact. How much, I'm not so sure. Is it worth worrying about?

In general, reducing the possibility of leaks by placing the DC up against a wall would be more beneficial that an extra 5m of ducting

3. Pleated filter
Any thoughts or recommendations for where I might get a good quality yet reasonably priced one to suit this extractor? I'm in Melbourne. What should I be looking out for?

You just have to shop around to get the best deal. The budget ones general let quite a lot of fine dust through (note the thick needle felt bags) for the first couple of hours of use so put a bucket of sawdust in the collection bag and run the DC outside for a couple of hours to condition the filter. Once they are conditioned they are fine.

4. Boxing
Building a box to contain the whole extractor unit. How do people get to the on/off switch or is it usually moved outside? What about changing bags and seeing when it's full? Anyone used a plexiglass/plastic wall on one of these?

Take the switch off the DC and move the switch to the outside of the enclosure.

Plexiglass is a good idea but it is also likely to charge up and collect dust so you can't see what is going on.

A simple manometer/pressure gauge to measuring the pressure drop across the filter may be of some value in determining when the filter needs cleaning. This is MUCH more important than seeing when the bag is full. After cleaning the filter the bags should be emptied whether it's full or not otherwise the fine dust will fluff up and clog the filter again within minutes.
see this post https://www.woodworkforums.com/f200/using-pressure-determine-filter-cleaning-time-187330

5. Venting
With a box, I'll need to vent. Looks like it will be through the ceiling/roof. The garage door is often open so that's out of the question (no point if the dust will just blow back in). The back wall is out because that's where our patio is. The two side walls are out because one is the neighbours house and the other is a bedroom!
Now looking at options for getting a flue put in with a roof cowl. This should let the fine dust travel off with the wind. Going to be a bit of work to go through the ceiling, tiles, etc.
Is venting in this way without a cyclone an issue?

That depends on the cyclone, a well designed and made cyclone should be fine this way.

[QC Inspector]

Try an industrial dust control/collector/handling company for filters. They may not be cheap but they are much better than the Asian ones with the paddles used on many import dust pumps.
http://www.donaldsonfilters.com.au

Pete

[Albert]

If you have time, you can play around with a cyclone, Donaldson torit makes very effective cyclones but they are very tall ie over 3m at least. For home workshop types Billpentz type seems to be working very well but I think it's quite loud and if you venting outside and you are in a residential zone, whether you are in Aus/NZ your local council is likely to have a rule about this... Venting inside with filter probably is the best if you want to stay under the radar? I am not sure the Asian import mobile cyclone is any good. I mean they can all suck but each system has it's pros and cons. A system suitable for one workshop may not be suitable for another workshop which was setup for different purpose.

I use baghouse system (Holytek 24 socks system, 4kw, 20 inch impeller) because this gives me the freedom to use multiple machine at a time, I am looking forward to next year when I start to employ workers then I can reap the benefit of a 12 inch main duct system. I was told by a filter expert that sometimes these dust extraction company out there can sell you a relatively cheap US/euro built machine but the filter you need to buy from them cost an arm and a leg, and if you want to use filter extractor, it's recommended for the cfm/filter area to stay under 1:100 ratio, say your filter area is 20m2, your inflow cfm should be under 2000, in Denmark this ratio is even 80-100, this ratio is to ensure the dust does not clog in between the filter media and only cakes on the filter so when the machine cleans itself (whether mechanical shaker or compressed air) it will come down to the bins.