Thread: How High can it suck?

G'day TT,

While I cant answer the question of how well it will collect dust with it set up he way you have shown but i can suggest you don't take it all the way to the roof.

Perhaps only go up to 2.2m-2.4m then come across horizontally with a nice big sweeping bend (6 x 15degree elbows) down to the machine. This should cut out approx 1m of vertical pipe and be much less of a restriction than the acute angle you've drawn.

Alternatively come straight across the floor (not ideal as you don't want to be tripping over it all day).

Just my two cents.

Ben

Thanks Ben - Your right about not wanting it on the floor.
I am thinking I could use a hanging strap/s from the portal frame & roof purlons so it doesn't have to go all the way up to the roof.
The idea of a radius-ed bend is also a beauty - thanks!
My only concern is how high It will suck before it has to go to the side and down to the bag.
Hopefully BobL (or others) might chip on with some real world data from their hard won experience!.
I'll likely be using WA Hardwoods mostly, so the dust/chips might be more dense / heavier than normal (~980kg/M^3 for Jarrah) from memory.
I'd sooner get good advice and do this dust thing once and do it right rather than re invent it a dozen times after the fact, to get it right. (i.e. avoid a dogs breakfast of fixes upon fixes).
In an ideal world, I would vent it outside via a chute and park a tandem tipping trailer with hungry boards under it, and just tow it away to dump when full - but I live in a far from ideal world these days so likely it will be bags of saw dust for a while - mulched with lime and dynamic lifter & poured out onto the gardens & under the orange and lemon trees etc for starters!.
Once the yards full?... who knows - likely I might start feeding it down the sewer or something if I get desperate!

Maybe start making & selling compressed sawdust fire logs.... (Daughter works at a servo - she can sell em by the bag for pocket money or something)!

I'll work something out!

To determine if it will block or not it's a simple question of calculating if the system will maintain an air speed of a greater than 4000 fpm inside the ducting, since 4000 fpm is the generally accepted minimum needed to keep sawdust suspended in the air stream.
If the air stream is moving at that speed or greater it will carry the sawdust - it doesn't matter if it going up or sideways the sawdust just needs to be held in the airstream.

A short length of 4" duct will when attached to a 2HP DC have a max flow of about 400 cfm.

This translates into an air speed of 4600 fpm through a 4" duct so it should theoretically hold the saw dust in suspension.

BUT
Now let's look at your specific situation
2 x 90º bends, about 10 m of ducting and 1 m of flex (all 4") will generate a pressure drop of ~5" of WC at 400 cfm.
Further losses will depend on what filters you use on your DC, but lets assume you have clean high quality pleated filters so the pressure loss will be ~0.5".
We should also add losses for the table saw but lets assume that is reasonably free flowing (they rarely are) so let's add 0.5" of pressure loss there.
The total pressure losses are thus 6".
Since a 2HP unit generates a max 8.5" of WC your system pressure will now be 8.5 -6 = 2.5" of pressure

NOW check the graph below out - find the 4" duct size line and follow it along until it crosses the 2.5" pressure vertical line.
This will give you around 200 cfm or 2300 fpm through a 4" duct - POOP the sawdust will settle out.

It may be better if 6" ducting is used. I will work out the calculation using 6" for a small fee





If you decide to go ahead with this anyway the one thing I would suggest is a vertical dust trap.
Maybe even use two dust traps - one for each vertical
These can be made in several ways but the easiest is to add a Wye in the vertical near the machine as shown in the picture below.
If the dust does fall out and plug the vertical it can then be easily cleared.
Depending on how often the sawdust falls out the sloping segment of ducting under the ceiling will also trap dust - this can be cleared by sticking a compressor line up into the ducting and blasting the settled sawdust with compressed air while the DC is running.
BTW the vertical traps will need to be cleaned regularly because they will naturally draw sawdust into themselves even without the ducting becoming blocked.
Another problem with your design is the >90º angle of the ducting high up near the roof - this is going to be a lot worse than a plain 90º bend.
I would also make all the 90º bends in large radius ie bend some 4" ducting yourself or use 6 x 15º PVC elbows.


The long and the short of it is that this task is simply not one for 4" ducting and a 2HP DC.
The minimum I would use in this case is a 3HP and 6" ducting and modify the machine to accept the 6"
Closer to ideal performance would be be obtained using a 4HP DC with a 15" impeller.
BTW shoulda put 6" ducting under the floor!

Thanks for that graph and explanation Bob - sir your a gentleman and a scholar and your bloods worth bottling!

The Y traps are a GREAT idea.

Unfortunately for me, I'd already poured my slab & built the shed, before stumbling upon your epic shed thread with the underfloor ducting so missed my opportunity.

I have found some old DC / ducting and cylone type threads this morning and been reading those, and will probably set up a separate wheely bin collector outside the shed, and put the DC in it's own lean too enclosure along side it. After seeing your graph and explanations I might go for a larger than 2HP DC as well.

I will run 6 inch PVC sewer pipe for my ducts at this stage & use 6 x 15 degree bends to radius the bends for air flow.

The 6 inch duct line is just off the top of your graph - but it seems I should have ample air flow then with say 3HP?.

With the Y dust traps I'll use screw on sewer inspection opening (IO) lids with the rubber O seal, to keep them air tight and make them removable - but will drill a hole in the center of the IO lid and install a snaplock air fitting tail, and pressure blow gun handle valve apparatus below that - so there's always compressed air at the Y fitting when the DC is on, and all I have to do is squeeze the trigger occasionally to blow it all up into the air stream for removal / cleaning, but in the event of a serious blockage, I can still remove the cap by unclipping the snaplock air hose fitting & unscrewing the IO cap.

At least that's my plan at this stage - likely it will evolve as I go.

Thanks again for the data Bob - makes a heap better option that guessing and trial and error.

Originally Posted by Timless Timber

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Unfortunately for me, I'd already poured my slab & built the shed, before stumbling upon your epic shed thread with the underfloor ducting so missed my opportunity.

Yeah I came close to missing out and just managed to squeeze it in at the last minute.

The 6 inch duct line is just off the top of your graph - but it seems I should have ample air flow then with say 3HP?.

I dunno about ample, I would call a 3HP marginal in your size shed.
A large combination machine like your should really be utilizing 8" ducting and a 1900 (real) CFM air flow.

BTW I have provided an updated graph that shows more 6" flow rate as required - this is now - here.

With the Y dust traps I'll use screw on sewer inspection opening (IO) lids with the rubber O seal, to keep them air tight and make them removable - but will drill a hole in the center of the IO lid and install a snaplock air fitting tail, and pressure blow gun handle valve apparatus below that - so there's always compressed air at the Y fitting when the DC is on, and all I have to do is squeeze the trigger occasionally to blow it all up into the air stream for removal / cleaning, but in the event of a serious blockage, I can still remove the cap by unclipping the snaplock air hose fitting & unscrewing the IO cap.

This is actually SOP in some industry systems.
In systems which need to cover long horizontal distances it is also not unusual to use multiple vertical zig zags with dust traps at the bottom of each zig-zag.
Another method used to fluff up settled dust inside a horizontal duct is to have a 1/2" air hose permanently inside a the duct just laying on the bottom of the duct. The hose has lots of small holes in it and a timer regularly sends a pulse of air through the line while the DC is running.

Thanks again for the data Bob - makes a heap better option that guessing and trial and error.

No wuckers!

Pulse Line - noted. I will have about 3 meters of horizontal duct roughly - so no biggee to install a plumbed air line full of small holes inside the duct when I am putting it all together. I'm thinking not to glue the duct permanent - but instead to maybe friction fit joints and 100mph gaffa tape over the joints - so if I ever have to, I can still disassemble it for a serious blockage or if i ever re organize the shed for say an extra machine or something... I can modify it without resorting to hacksaws.

It's a steep learning curve ATM.... but I am enjoying the journey!

Lets see if I have this right.........(from the graphy thing)

If I've dropped to only 2 inches of pressure due to various friction losses etc, and I need 4000cfm to keep the sawdust suspended in a stream of air... then I would need to go to ~13 inch dia ducting? - to achieve the 4000 cfm (It travels faster cos there is less pipe friction?).

So if I do wish to use only 6 inch pipe, instead of 2 inches of pressure I'd need (extrapolating off the right side of the chart) somewhere around 20 inches of pressure - to achieve 4000cfm - to suspend the sawdust....

And I don't think a 3 Hp machine can generate much more than 8 inches in an ideal environment.

So I need a much bigger dusty - yes?

Which means that instead of a 15 amp single phase GPO outlet on that side of the shed (as I was planning), maybe I should allow a 2nd 3 phase outlet sufficient to run something that will do the job?

I feel my 3 phase power quote going up as I type!

(or did I screw up the graph Math thing - heck I don't even know what 'WC' stands for except water closet on set of house plans let alone the equations).

If the ducts get any bigger I'll be able to crawl up inside them to clean them out!

I was looking at the DC's at Carbatec site today....and saw they had 3 phase models...around 2+ grand or so..

Then again - the dust thing could kill me given my past history with it - so I have to get this right.

Sorry for the 101 questions.

Dust in suspension 90° with a 300mm long pipe - YouTube there is a couple more there as well.
I was doing a mod to some ducting sometime back and took a few vids of how it looks inside the duct, I held a bucket full of dust upto a 100mm dmv sewer pipe (which is more like 112mm? ID (from memory) ) which then goes into a 200mm duct, this vid clearly shows that my airspeed is high enough to keep the dust in suspension, what it doesn't keep in suspension is big bits like this
big bits in elbow.JPG
the ducting has a short vertical lift into the cyclone but there is not enough air speed to keep these sized bits in suspension thus they drop to the btm of the elbow and I have to periodically clean it out. A cleanout wye here would be good just like Bob suggests.
overall view of DC.jpg
I think that with your system if you have to blow it out to keep it clear I'd be going for the larger DC and keeping the dust in suspension.




Pete

You make an excellent point Pete - with a pic worth 1000 words!

Many years ago a mate had a factory down in our southwest round the corner from mine. We would saw timber on my mill and dry it in my kiln and run T & G flooring on his 2 VERY old Wadkin 4 siders (A 4 inch baby and a 8inch big boy).... and he had a extraction system and duct with cyclone similar to what you depict...

That thing could suck a proverbial golf ball thru a half in garden hose (We nick named it Delvine Brown after the hooker that Hugh Grant got caught with around the time) - but as you show, we still had slivers of wood come off, that went up the duct and blocked it eventually.

As I will be using the spindle moulder a fair bit, (hopefully) there's a high likelihood I will run into this issue, so the Y traps - will be a given for me.

Larger makes a lot of sense... the cost might be an issue....initially - but do it once do it right, penny wise and pound foolish and all that.

I MIGHT grab a cheap 2nd hand 2HP off gumtree for say $200 - do a few jobs with it in less than ideal conditions and use the proceeds to pay for a proper ducted setup....

That's one option i may have to consider if I want this done right - but I need to get it in my head what I am doing and using because if I have the sparky coming to do the wire up, then... i need to get the right power put in where the DC will eventually reside.

1 Ft dia pipes and cyclones - I tend to associate with the old 4 siders with 7 or 9 heads all making large quantities of dust at the same time!

All my 20 years in the factory we had a 2hp single phase mobile bag and filter with a 4 inch hose and moved it machine to machine.... dust wasn't a big concern and I paid for it with crook lungs after 20 years.



As you can see the old place was VERY basic, but it was 30 years ago we built it from recycled timber and Corrugated iron & the old man was very old school.



It was dust heaven in that place.....it was where all the dust went to die.

That's why I have to get this right if I want any chance of playing with wood again...

Interesting topic I must say.... my thoughts have metamorphosed completely in just one day as to what I need & what will do the job.

I am now worried about noise (for the neighbors) from a 3 phase 4 hp or greater DC mounted outside the shed in a lean too....

Ol Delvine Brown used to fairly howl - I could hear her from up at my factory when old Tiger Tom had one of the old Wadkins wound up.

My neighbors will have conniptions if I make a racket like that!

This is going to take some serious research, I think.

Those vids on Youtube are instructional and make the point for 45 degree bends over 90 degrees.

Many thanks to all of you - your contributions are most enlightening.

Originally Posted by Timless Timber

Lets see if I have this right.........(from the graphy thing)
If I've dropped to only 2 inches of pressure due to various friction losses etc, and I need 4000cfm to keep the sawdust suspended in a stream of air... then I would need to go to ~13 inch dia ducting? - to achieve the 4000 cfm (It travels faster cos there is less pipe friction?).

It doesn't work that way because most basic DC blowers will quickly run out of grunt well before then. To maintain 2" of press in a 13" duct requires a blower capable of moving 3000 cfm - that's about a 6HP motor and 16" impeller.

So if I do wish to use only 6 inch pipe, instead of 2 inches of pressure I'd need (extrapolating off the right side of the chart) somewhere around 20 inches of pressure - to achieve 4000 cfm - to suspend the sawdust....

But if you use 6" pipe instead of 4" you won't be down to 2"
You can calculate it for yourself using staticcalc.xls from Bill Pentz website.
Basically you stick some numbers into a spread sheet and it does it for

And I don't think a 3 Hp machine can generate much more than 8 inches in an ideal environment.

Maybe a little more but not much.

So I need a much bigger dusty - yes?
Which means that instead of a 15 amp single phase GPO outlet on that side of the shed (as I was planning), maybe I should allow a 2nd 3 phase outlet sufficient to run something that will do the job?

A 4HP unit like a cyclone would be about right for your shed. This will run off a 15A plug and if you get the VFD option you can spin the impeller from 50 to 60Hz and get 12" of pressure.

(or did I screw up the graph Math thing - heck I don't even know what 'WC' stands for except water closet on set of house plans let alone the equations).

Close, "Water column"

I was looking at the DC's at Carbatec site today....and saw they had 3 phase models...around 2+ grand or so..

You'd be far better of with a Clearvue than one of those.

As always, BobL speaks with wisdom.

All the available evidence suggests that the best DC solution for small to medium sized sheds is the Clear Vue ... but I own one, and so am biased. I did a lot of research and got advice from many people before figuring out that BobL was the only guide I needed, along with the stuff on Bill Pentz's site. However, the Clear Vue is not the cheapest option. The best seldom is.

I was wading ankle deep is dust until I got my cyclone. Now my shop stays clean and I breathe clean air. Also, I'm in the good books with SWMBO, as I no longer get dust in her nice clean house.

My set-up, including the VFD, cost a little over $2,500, plus ducting and flexy. The Clear Vue was the only machine that combined excellent air flow with a very small footprint, no filters to block or clean and no need for 3 phase power. In my shop, 3 phase power would have cost as much as my cyclone, so the VFD was a very cheap fix. If I'd gone for a 3 HP dusty I'd have bags to empty and filters to clean and would have needed to build a shed for it outside the shop to avoid leaks putting dust into the shop and to avoid the superfine particles that get through the filters. This shed made a 3 HP dusty more expensive than a Clear Vue, which has a tiny footprint and easily fell into my shop. The 3 HP unit, by comparison, is huge. It gobbles up a lot of space that I did not have.

So far as picking up larger chips is concerned, have a look at my table saw in action. Table Saw Overhead Dust Collection.wmv - YouTube The drop saw does the same thing. The off cuts all wind up in the bin. Never had one get stuck in a duct.

As Bob says so often, even a great system like a Clear Vue will be choked by poor guards/ports on machines, or by poor duct design. If you would like to see some of my modifications, go to https://www.woodworkforums.com/f200/m...66/index6.html I am indebted to BobL for a lot of advice on these subjects.

Finally, if you really are anal about clean air, consider getting a Clear Vue Max. It allows you to have at least two six inch ports open simultaneously. That means that you can be operating a machine and at the same time have an overhead port open to clear the air in the shop of any tramp dust that might be floating about. If I had my time again, I'd likely get the Max with a VFD, however, as you will see in the videos, the 1800 with a VFD running at 60 Hz makes Delvine Brown look like a novice. Be aware you need to make the main line of your duct 8 inches rather than six, dropping down to 6 inch lines to each machine, and this 8 inch duct adds to the cost.

IMAG0021.jpg
Here is a pic of what was discussed earlier in the thread ... a wide radius bend. I only had one 90 degree bend in my main line, and it seemed worthwhile to spend a few bucks on fittings to minimise losses.

I had the oppourtunity to visit John last week for a chat and check out his setup, I was curious to see how much suck and noise it made, using the well known ooo ahhh I reckon about this much guesstimate I reckon mine is very similliar and makes about the same sort of noise at the outlet, to reduce noise at the outlet (the outlet makes the most noise) you will need a muffler, additionally it will help to insulate the lean to.
I can walk ~20m away from the dusty (direct line) and because I know it is going I can hear it but I doubt the nieghbors will hear it if they are making their normal amount of noise, I can walk around the corner of the house and I can barely hear it.
There are a few noise reduction threads on the forum and of course BP's site.



Pete

Ok even betterer!.
So now I'm at a CVMax (with VFD? = Very Fine Dust? Vertical Finger Decapitator?) and another $2.5K on top of the $2.5K for 3 phase....
Suddenly "the Journey" is fast losing it's appeal for me again!

I do like the look of the Clearvue Max - Not so fussed about the metal bucket collector tho - to me a wheelie bin under it would be better - lined with a big black plastic bags & just fold the lid back - clamp on the unit lid, and when its full - un-clamp - twist tie the black plastic bag top & fold the wheelie bin lid closed, and walk it out to the street ready for the Rubbish truck to collect.

Maybe even have 2 or 3 wheelie bins... and if they all get full in the 1 week, just distribute them up and down the street late at night in the dark out the front of a few neighbors houses, so the garbage truck truck doesn't realize its all my sawdust they are collecting!

With that big metal drum collector, I'd have to manually tip it into a wheelie bin all the time when full...and my weekly physio bills are already enough to fund her monthly BMW payments! The less heavy lifting the better.

I'm now correct in thinking, I run a 8inch duct lengthways down the center under the shed roof pitch - and take 2 x 6 inch lines to my machine/s?.

I like the sound of this... and the vids of the clearview in action are pretty impressive... any idea what decibels sound level they run at? The small footprint would be good - it would fit between my shed and the back fence... at least. (I only have a little over a meter width). Just enough to put some soundproofed enclosure around it.

It seems mighty tall tho... with a 2 meter fence how much of it will be visible above the fence to annoy the neighbors?

One thing that's confusing me... just a little.

This 6 inch 8 inch ducting - all the math stacks up for it...

BUT

on My Combination Machine...



The dust duct connections off the machine for thick-nesser, spindle moulder, and saw outlet are all 90mm!

The one from the saw has a rubber concertina type hose inside off the bottom of the saw blade cover, that's only 50mm...and joins into the external 90mm outlet!

If I go all 8 inch duct down to 6 inch duct for the machine - won't these small 90mm outlets on the 3 different parts of the machine, just restrict the flow of sawdust down to what a 4 inch pipe could handle anyway?

All of the 6 & 8 inch duct work I've seen commercially, is usually connected to big Weinig 4 siders, with 9 heads producing big volumes of sawdust....into hoppers, that you cart away in a 8 tonne truck...

I've got a 6m x 7m garage in the backyard with a combination machine - using only one part at a time - the jointer, or the thickneser, or the saw or the spindle moulder....

It's not like I have it set up to run commercial quantities, of skirtings, architraves, T & G Flooring (which would be better off run thru a 4 sider in one pass anyway).

It's for one man to tinker on his shed and make stuff - jewellery boxes etc.... maybe a small bench or something.

Is all this cyclone and 8 & 6 inch ducting a bit of overkill? The price is.... and in an ideal world - I'd LIKE to have it, I'm just wondering...if it's really necessary....from a noise point of view and cost point of view.

I mean if a neighbor complains about noise... and the council bloke comes round with his DB meter - and sees a sawdust cyclone sticking up 3 meters off the shed... - he is going to think I'm running a joinery shop that should be in the light industrial area - and close me down, but if he sees one bloke making a few jewellery boxes with a combo machine and 2HP mobile woodfast dust bag, he's less likely to think I'm in business... so to speak.

Am I about to use a sledge hammer to crack a walnut here?

How many of the hobbyists on this site run 8 and 6 inch ducting & cyclones to their back yard shed is I guess what I am wondering.

Just trying to get some perspective is all.

Bob I seem to recall you running a double 2 or 3 hp bag setup in your shed lean too?...in your shed thread...although your underfloor duct was 6 inch from memory.

It might end up being something have to start small and work my way up to a clearvue max cyclone... there are a few used 2 hp dust bags setups on gumtree for ~$200, that would get me started.... and yes my healths an issue for me so I need to take this seriously..... and get ti right...

Decisions decisions..

I have the weekend and the wood show, to mull it all over... right now I feel a bit giddy... like $5Ks worth of giddy - enough to make me wanna sit down!.

I'll make an effort to swing past the FWW association stand Sunday Bob and try to catch up & put a face to a name (and to thank you in person).

Cheers

90 mm outlets are most likely to be only part of your problem with machinery. Most machinery outlets are way too small but just opening them up might not solve the air flow problem. You need to ensure that there are enough holes and gaps so that enough air can flow. There is often no way around cutting holes into the machinery cabinets and hoods and just to make things more interesting just about every machine is different.

I get an email every other day from forum members and other people asking about dust extraction. The most common questions are around using 2HP DCs to control dust which is why I went to such an effort to test a generic version of this DC and modified one to see what it could really achieve. The bottom line is no DC out of the box will extract the desired 1000 CFM from most machinery. Even a clearvue will require machine outlet enlargement and 6" ducting to achieve this.