Newby dust collector question

[David L Morse]

For a horizontal and vertical (down) run, 6" or larger may be nice and certainly would have less flow restriction. But, with the larger diameter/volume, it will also reduce the velocity of the air proportionately. I'm wondering if I would have enough suction to pull dust and large chips (from wood lathe) 9 feet upwards vertically. Dust maybe. Wet chips ???

You might get as much as 3kft/min in 6" with the HFDC using it's 5micron bag. That could be considered marginal for your vertical runs.

Given the somewhat asthmatic performance of the HFDC blower you'll probably see about a 25% difference in CFM between 6" and 4" ducting.

[Jim Becker]

For a horizontal and vertical (down) run, 6" or larger may be nice and certainly would have less flow restriction. But, with the larger diameter/volume, it will also reduce the velocity of the air proportionately. I'm wondering if I would have enough suction to pull dust and large chips (from wood lathe) 9 feet upwards vertically. Dust maybe. Wet chips ???

Dust collectors do not work based on suction. They work based on moving large volumes of air at what is effectively low suction. It's all about maintaining air velocity and volume measured in Cubic Feed Per Minute. A 4" duct can't get much above 400-450 CFM regardless of the fan capability at the dust collector end. The increased volume capacity of a 6" duct can support in the neighborhood of 800-1000 CFM. Your 2hp HF fan will perform much better with a 6" duct than with a 4" duct and if I'm not mistaken, it's native input capability is 6". (It may have a reducer on it)

[Bill Space]

Also one has to take into account that one mans satisfactorily clean is another mans dirty. I have had guys tell me their dust collection is great only to walk into their shop and see dust everywhere.

In my mind the dust collector is there to remove dust and chips from the tool being used. There are MANY ways to produce chips and dust that end up on the floor of the shop.

I just judge my system performance by looking inside the machine and seeing if the chips and dust is removed. For me, my dust collector is used to remove waste from the machines, not as a shop air cleaner, although it does that to some degree as well, as I do not see a much in the way of dust on the side of the basement where the dust collector resides, along with the wife's washer and drier.

Personally, I do not see a correlation between a shop with a lot of dust and chips on the floor and the functionality of the dust collector system. Apples and oranges to a great degree in my mind. This is probably the reason a lot of shops have floor sweeps installed. I don't have one but really need a couple...

Bill

[Jeremy Treibs]

I will leave it up to the more seasoned guys to answer the technical side of the house questions... but concerning where to get this said material... I found my 6" fittings at a place called Habitat for Humanity here in western Washington. It has a lot of junk but I generally find a couple 6" fittings every week or so for a couple bucks a piece. A little soap and water and they look brand new again. If you aren't in a hurry, you can potentially save yourself a lot of money by going that route. I used the 6" green S&D from the local home center.

[Alan Schaffter]

In my mind the dust collector is there to remove dust and chips from the tool being used. There are MANY ways to produce chips and dust that end up on the floor of the shop.

I just judge my system performance by looking inside the machine and seeing if the chips and dust is removed. For me, my dust collector is used to remove waste from the machines, not as a shop air cleaner, although it does that to some degree as well, as I do not see a much in the way of dust on the side of the basement where the dust collector resides, along with the wife's washer and drier.

Personally, I do not see a correlation between a shop with a lot of dust and chips on the floor and the functionality of the dust collector system. Apples and oranges to a great degree in my mind. This is probably the reason a lot of shops have floor sweeps installed. I don't have one but really need a couple...

Bill

Try to re-direct your thinking. A dust collector has many purposes- at the lowest level is to collect chips and large dust particles (those you can see and which generally don't stay airborne much.) That is fairly easy to do with most DC's. At the highest level the purpose of a DC is health and safety- to collect as much as possible of the fine, invisible dust (the hazardous-to-your-health stuff in the .5 - 10 micron size range) that escapes unseen from most machines and can stay airborne for extended time. This is not an easy task and as Jim says requires a considerable amount of CFM.

To each his own. You pays your price and takes your chance.

[Bill Space]

"Try to re-direct your thinking. A dust collector has many purposes- at the lowest level is to collect chips and large dust particles (those you can see and which generally don't stay airborne much.) That is fairly easy to do with most DC's. At the highest level the purpose of a DC is health and safety- to collect as much as possible of the fine, invisible dust (the hazardous-to-your-health stuff in the .5 - 10 micron size range) that escapes unseen from most machines and can stay airborne for extended time. This is not an easy task and as Jim says requires a considerable amount of CFM."

This is interesting but I think not directly related to the OP's question.

The OP's question related to air flow through a given length of pipe. It never occurred to me that a system that moved chips and saw dust from the machine might be less effective at capturing the fine dust generated. I don't think this is the case within the machine, but I can see how this would be a concern: IF such material does not get into the piping, it cannot be carried away to the down stream filter.

So are you saying that a system that is able to move chips satisfactorily is likely to be less efficient at moving small, light weight particles? Seems counter intuitive to me. I doubt this is what you meant.

But the OP was asking about flow through a pipe, not about design of an air purification system. From my experience the answer is that if you get the chips and dust into a 4" pipe of the length mentioned, it is highly likely they will be delivered to whatever filter you have in your system.

Granted, without an excellent dust capturing setup, there will be things left floating in the air around the tool you are using. This seems to be beyond the scope of the original question...but it is certainly something we all should keep in mind.

Bill

[Brice Rogers]

My original question was just about what kind of pipe that most people use. I got a good answer (SDR 35). I enjoyed reading the other comments - - some were educational.

Now I'm trying to sort out the connector issues. It is interesting that copper pipe and fittings all fit together and seem to make sense, whereas a 4" dust fitting, a 4" hose, a 4" SDR 35 (or perhaps class or schedule 20), ABS, and schedule 40 all have different sizes and couplings. I have been looking in Rockler and got a kick out of the number of 4" to 4" adapters they offer. Slowly this is falling into place (I think).

I'm in the process of starting the build of a Thien baffle separator (it "baffles" me how well it works given it is so easy to build) and will just be blowing the fine and dangerous dust outside. (BTW, I live on a large property with no neighbors close by).

[Alan Schaffter]

This is interesting but I think not directly related to the OP's question.

The OP's question related to air flow through a given length of pipe. It never occurred to me that a system that moved chips and saw dust from the machine might be less effective at capturing the fine dust generated. I don't think this is the case within the machine, but I can see how this would be a concern: IF such material does not get into the piping, it cannot be carried away to the down stream filter.

So are you saying that a system that is able to move chips satisfactorily is likely to be less efficient at moving small, light weight particles? Seems counter intuitive to me. I doubt this is what you meant.

But the OP was asking about flow through a pipe, not about design of an air purification system. From my experience the answer is that if you get the chips and dust into a 4" pipe of the length mentioned, it is highly likely they will be delivered to whatever filter you have in your system.

Granted, without an excellent dust capturing setup, there will be things left floating in the air around the tool you are using. This seems to be beyond the scope of the original question...but it is certainly something we all should keep in mind.

Bill

This is exactly Brice's issue and countless dust collection threads over the last 15 years! First do the math and you will see using a typical DC velocity of 4000 fpm and disregarding losses due to duct length, bends, fittings, etc. the max you will see through a 4" duct is about 350 cfm at best (area in sq. ft. X vel = pi X r² X 4000= 3.14 X 4 ÷ 144 = .087 sq. ft.). If you go into the industry tables of recommended dust collection CFM for WW machines (a version can be found on Bill Pentz site), you will see that this is insufficient for most. And again, this is being generous with the velocity and also ignoring system losses! Now, if the dust is generated at a single point (its not!), doesn't spread, and that point is directly in front of the duct intake (never is) it might be sufficient.

Remember, air is drawn into a (two dimensional) circular duct opening, while dust typically expands from the point of origin, outward (spherically) in all directions.

My original question was just about what kind of pipe that most people use. I got a good answer (SDR 35). I enjoyed reading the other comments - - some were educational.

Now I'm trying to sort out the connector issues. It is interesting that copper pipe and fittings all fit together and seem to make sense, whereas a 4" dust fitting, a 4" hose, a 4" SDR 35 (or perhaps class or schedule 20), ABS, and schedule 40 all have different sizes and couplings. I have been looking in Rockler and got a kick out of the number of 4" to 4" adapters they offer. Slowly this is falling into place (I think).

I'm in the process of starting the build of a Thien baffle separator (it "baffles" me how well it works given it is so easy to build) and will just be blowing the fine and dangerous dust outside. (BTW, I live on a large property with no neighbors close by).

As to pipe- typical requirements are- 6", light weight, inexpensive. Plumbing (Sched 40) pipe fails on the last two, especially when you look at the price of fittings- a 6" X 6" X 6" Sched 40 wye can cost close to $30 or more. SDR 35 (the Blueish-green stuff) is less expensive, however it is just about as heavy as Sched 40. (O.D.s are different so they use different fittings)

What you really want is a sewer and drain (S&D) pipe labelled ASTM 2729 and variously called "thin wall", "thin-walled S&D", "thin wall gravity drain", "Solid perf" (both 4" and 6" 2729 come in solid and perforated). It is typically white and has a simple, non-gasketed bell at one end. 6" flex can be coaxed over the pipe or slipped inside the bell end. It has the same O.D. as SDR 35 and so uses the same fittings. Since the wall is thinner the I.D of ASTM 2729 is slightly larger than SDR 35. 6" fittings can be found at Lowes, but in the drainage/irrigation NOT the plumbing area. They stock the fittings for 6" SDR 35/ASTM pipe, but not 6" ASTM 2729 pipe itself (they do carry it in 4" however). Sources for the 6" ASTM 2729 pipe include irrigation supply houses, John Deere Landscapes (nation-wide), Menards in the Mid-west (so I'm told), Ferguson Water Works (nation-wide), etc. but it may be hard to find and you need to ask for the correct stuff. But, for a big duct layout it is worth it. You'll only save a bit over SDR 35 and a bit more over Sched 40 pipe, but you can typically save a lot, $10 or more, on a 6" wye compared to Sched 40.

[Jim Becker]

Brice, avoid those so-called "dust fittings" from the woodworking merchandisers. Most are poorly made and that makes this more restrictive to air flow. If you're going to use the S&D pipe, utilize S&D fittings and manufacture what you need to adapt to a situation from wood, plastic and metal as appropriate.

[Robert Delhommer Sr]

SDR35 pipe is the way to go.