Planned dust collection system

[DennisCA]

Greetings from Finland.

I'm currently building a garage that will be partially dedicated to a woodworking workshop. It's close to done and I've been considering dust collection options. I've done a lot of research and asked a lot of questions and what I've come to is I should aim for the following:

-Metal ducting in the size of 150-160mm (I think 5-6.3", metal because it grounds easily, no static issues with dust clinging)

-Ducting in the ceiling rather than walls where possible

-Vent outside (just seems like the best way avoid a lot of potential issues)

-Powerful blower. I have a 3-phase 4kw motor I plan to use in a jointer/planer, somewhat overkill for the small 8" machine I have, but I got it cheaply. I guess it can be refitted later for to a dust collector impeller/fan and be more suited to that task.

I was looking at cyclone separators and I am currently building my own shop vac from leftover parts and a cheap cyclone I bought from china. I was considering building a big one from Bill Pentz designs but since I am venting outside, and also reading Matthias Wandels experiences with his thien baffle system, it seems like this system is entirely adequate in separating most dust and chips and most fine saw dust. I gather there's some contention between cyclone and thien baffle users as well...

Anyway it seems like it works well and well enough for my purposes. I am wondering are there any guidelines for what size I should build given a certain airflow/speed? This will be a large and powerful system, though hopefully it should come out pretty cheap since I am building it myself from spare parts and 2nd hand stuff.

[DennisCA]

Not a lot of traction, but I guess most of this has been covered on this forum so far. But I have a specific question I'd like an answer to. I plan to use 150-160mm ducting in the ceiling and to the dust collector itself as I mentioned. But many of the ports on my machines are maybe 100mm or less.

Am I right though in making a "backbone" or main stem from thicker ducting while having smaller hoses and pipes to individual machines? Or is it a waste of piping?

[BernardNaish]

Thien separators work very well and are very practical.

I am not quite sure how you are using your 4kw blower? It sounds as though you are sucking from the planer and pushing the shavings and dust out through a pipe system? I do not think that would work. The usual way is to use a pipe system to suck from the machines, pass that loaded airflow through the separator and then into the DC. All suck - not push.

Your blower may not be suitable to make your own DC. It depends on the pressure/flow curves. Unless the blower is specifically designed for this use it will probably not have the right specifications.

If you had a DC with that much power it should be able to handle 150mm (6") pipework with ease. Even so keep all pipework as short as possible, use slow bends, ie with radius twice or thrice the diameter of the pipe or two 45 degree bends instead of one 90 degree. Use "Y" junctions with the incoming branch set at 45 degrees to the main flow instead of "T" junctions. Maintain the 150mm to as close as possible to the machines then neck down to 100mm (4") ot whatever size is on the machine. Keep any hoses to the absolute minimum as they will eat into performance.

Make a top hat separator as here except use polycarbonate sheet and not acrylic for the walls:

http://www.jpthien.com/smf/index.php?topic=563.msg3034;topicseen#msg3034

Close-couple the DC fan to the top hat with an air straightener section.

It is well worth having the DC  and separator in a separate walled room or chamber so that the noise of the former and the dust when emptying the latter is kept well away from the shop. You should fit a control system so that your wood working machines cannot be switched on unless the DC is already on. If you are as lazy as me it is all too easy to "forget" to turn on the shaving shifting system.

Consider if it is safe to vent outside! You are collecting shavings for your convenience and dust so that it does not damage your lungs. The most dangerous very fine dust will travel on the wind a surprising distance. Where will it end up and who might unknowingly breath it? If you cannot be certain then fit a fine dust pleated filter. It may even be illegal in your area for you to vent dangerous dust into the atmosphere.

[DennisCA]

My 4kW motor powers my planer right now, I have no dust collection aside from a small home made shopvac with a small cyclone. What I meant was I could reuse the motor for a DC system. I have no fan for it however.

The idea that the dust outside could travel far and be dangerous to anyone sounds unbelieveable, any data on that? Surely living in a city must be worse given the air pollution and particulate matter in the air from ordinary dust. This sounds even more excessive than bill pentz pages now.

[jdon]

Okay, Dennis, I'll add my $0.02, or the equivalent in Finnish markka. Your most recent post clarifies your plan.

First, as far as duct size. The general rules for maximum performance are to keep duct runs short, wide, and straight as much as possible. That said, assuming you have several dust producing machines you want connected, the typical way is to go with a large diameter trunk line, with smaller branches to individual machines. With a 4 kW blower (16+ amps, I assume), I wouldn't go with less than 6" main duct size, or 4" for tool connections.

I think your major challenge is getting your impeller set up appropriately. As much as I admire Mr. Wandel's skill and creativity, I would be extremely leery of scaling up his wooden homemade impeller to fit a 4 kW motor- it just looks like a disaster about to happen. Design of an efficient impeller (at least to an amateur like me) appears very complex. Maybe you can find a used impeller of appropriate size with a burned out motor, or check out the Cincinnati Fan web site- there's a ton of information there. In the end, it may be more cost effective to get an intact DC blower and find another use for your motor.

I see both BernardNaish's and your points of view regarding dispersal of fine dust to the outside. It really depends on your locale. If your shop is in a more rural, less densely populated setting, fine dust will either settle to the ground or be so diluted that it causes no significant health risk, esp. compared to other airborne hazards. If you live near others, though, it would be more neighborly not to discharge dust in their direction. It begs the question, which I'm not sure anyone can answer, as to how close is too close.

Disclaimer: I am by no means an expert in anything! Good luck with your project.

[DennisCA]

My motor turns slower than Wandels impeller actually because we use 50hz in Finland, so if I made it to the same size it would be less effective, and probably draw very little power. It could be scaled up a little bit, but it would turn slower and probably be under less stress than his impeller if I made it.

The 4kw motor has a 9.5amp fuse on its control box, more than that it shouldn't use except for short bursts during startup. 400 volts of current does help keep amperage down.

I live somewhat half-way rural, I got neighbors within 10-15 meters of my garage, but if I vented it towards one side, I doubt it would be able to bother anyone, since the DC isn't active all the time and we're probably talking small amounts and it'd be in another direction where there is noone.

[jgt1942]

DennisCA - venting outside is a great option. I wish I could do the same but my neighbors would complain! When I built my unit I converted a Grizzly 220v 2HP unit and for my shop so far I've not had any issues however as a portable unit it is only connected to one machine when it is used. See the image below.

Running ducts pipe is a great option I will convert mine sometime in the future.

I'd suggest installing micro switches so when you open a gate the unit comes on. Better yet when you turn on a machine, the gate is opened and the DC is turned on.

I'd also suggest installing a sensor to turn off the DC when your can gets full. I don't have this on my unit and at times I do over fill the Brute 20 gal can. When this happens dust goes into the bag otherwise the bag is empty.

If you look closely you can see that the walls of my Thien are Plexiglas. I did this because I wanted to see the action but it also allows me to see when the can is full. However I try to empty the can often and avoid the mess created when the can is full. I don't have a sensor to tell me when the can is full (bummer). If you go the Plexiglas route I suggest building a form to assist in bending the Plexiglas. I did not and it was difficult to correct my mistakes. My Plexiglas is 1/4" thick, I used a MAPP gas torch to heat and bend it. A good heat gun will also work. If you put too much heat it will bubble. Once you goof once or twice you quickly learn how much is too much. :)

Originally I was going to use a 32 gal Brute can but goofed on the spacing and had to use the 20 gal can. But this is good because the full 20 gal can is MUCH lighter than a full 32 gal can.

Somewhere I read that we need not be concerned about the static electricity and the article suggested using plastic pipe rather than metal. I have a central vacuum system in my 3200 square foot house and it has all plastic pipe. I've lived in the house now for 8 years and so far no issues.

[retired2]

DennisCA - venting outside is a great option. I wish I could do the same but my neighbors would complain! When I built my unit I converted a Grizzly 220v 2HP unit and for my shop so far I've not had any issues however as a portable unit it is only connected to one machine when it is used. See the image below.

Running ducts pipe is a great option I will convert mine sometime in the future.

I'd suggest installing micro switches so when you open a gate the unit comes on. Better yet when you turn on a machine, the gate is opened and the DC is turned on.

I'd also suggest installing a sensor to turn off the DC when your can gets full. I don't have this on my unit and at times I do over fill the Brute 20 gal can. When this happens dust goes into the bag otherwise the bag is empty.

If you look closely you can see that the walls of my Thien are Plexiglas. I did this because I wanted to see the action but it also allows me to see when the can is full. However I try to empty the can often and avoid the mess created when the can is full. I don't have a sensor to tell me when the can is full (bummer). If you go the Plexiglas route I suggest building a form to assist in bending the Plexiglas. I did not and it was difficult to correct my mistakes. My Plexiglas is 1/4" thick, I used a MAPP gas torch to heat and bend it. A good heat gun will also work. If you put too much heat it will bubble. Once you goof once or twice you quickly learn how much is too much. :)

Originally I was going to use a 32 gal Brute can but goofed on the spacing and had to use the 20 gal can. But this is good because the full 20 gal can is MUCH lighter than a full 32 gal can.

Somewhere I read that we need not be concerned about the static electricity and the article suggested using plastic pipe rather than metal. I have a central vacuum system in my 3200 square foot house and it has all plastic pipe. I've lived in the house now for 8 years and so far no issues.

Dust explosions in home shop vaccum systems is a wildly exaggerated issue.  With a little research on the internet you can find articles dispelling this concern.  I can't point you to them, but I think the subject has been covered more than once in this forum.

[BernardNaish]

The reason you had problems bending acrylic is that it is too hard to be used as a flexible material. Think of it as plastic glass. Polycarbonate is ideal for bending and is much more scratch resistant.

[DennisCA]

So I'm not really progressing here because I don't have a motor I can build from, well I have the 4kw beast but I need it for my jointer/planer. I'm only willing to pay scraps for a used induction motor and so I have to be patient and wait.

But in the meantime I wonder if the separator design that matthias wandel used for his dust collector build has been covered in discussions? Tried searching for his name but did not find much all three mentions of his name are in this thread. I would have thought someone might have been interested in comparing his design vs. the top hat style. The main difference seems to be his is taller.

[retired2]

So I'm not really progressing here because I don't have a motor I can build from, well I have the 4kw beast but I need it for my jointer/planer. I'm only willing to pay scraps for a used induction motor and so I have to be patient and wait.

But in the meantime I wonder if the separator design that matthias wandel used for his dust collector build has been covered in discussions? Tried searching for his name but did not find much all three mentions of his name are in this thread. I would have thought someone might have been interested in comparing his design vs. the top hat style. The main difference seems to be his is taller.

There are some double high top hat designs that were covered here, but I can't find them quickly.  Do a search on the phrase double high or 2H, I think those descriptions might have been used in the discussions.

[jgt1942]

The reason you had problems bending acrylic is that it is too hard to be used as a flexible material. Think of it as plastic glass. Polycarbonate is ideal for bending and is much more scratch resistant.

Thanks for the info, now I know!

[DennisCA]

I read that for cyclones, having a bigger outlet means reducing air resistance and also reducing the speed of the air flow at the outlet, which increases separation. Or so says Bill Pentz, I am wondering if this applies for thien style separators as well? Most people seem to build their separators with identical sized inlets and outlets.

[tvman44]

Interesting question!  :)

[retired2]

I read that for cyclones, having a bigger outlet means reducing air resistance and also reducing the speed of the air flow at the outlet, which increases separation. Or so says Bill Pentz, I am wondering if this applies for thien style separators as well? Most people seem to build their separators with identical sized inlets and outlets.

Don't see any reason why Pentz's statement does not also apply to separators.  So, why then do so many have inlets and outlets the same size?

When it comes to stationary systems, I can think of a number of reasons.  Most of us don't have the luxury of a 3hp or 5hp behemoth as the heart of our system.  So, we start with a 1-1/2 hp that is marginally powered for the task.  So, it is advantageous to keep the mains and drops as large as possible, but not so large that the velocity drops below what is required to keep the waste entrained.  That usually means mains are the same size as the inlet port on the separator.

Then we come to the separator, which more often than not is sized to match the diameter of the waste drum being used.  So, if the separator is far enough from the inlet of the DC, then yes a larger outlet pipe could be installed on the separator and then reduced back down before entering the DC.  That sounds good, but there are two problems.  First, many people, myself included, have the separator close coupled to the DC and there is not room to make size changes, and keep in mind adding pipe and reducers adds to the system losses.  The second problem is that when the outlet pipe diameter gets closer to the inlet pipe diameter the probability of by-pass waste increases.  And remember, the diameter of the separator has already been set by the drum.