Dust Collection main lines and drops. What sizes to use?

[Chris Atzinger]

Hi

I am in the process of mapping out my DC duct work. I am planning to use a 1 ½ HP grizzly cyclone DC that has a 6” port, with an optional 5” reducer. Based on what I have read, I want to use the 6” as much as possible for the main trunk line. For the drops, should I go from 6” main line to 5” drops to 4” flex/tool port? Or just go 6” main line to 6” drop, to 4” tool port. Should I scrap the 6” main, and just you 5” mains to reduce the number of...reductions?


Thanks!
Chris

[Dan Friedrichs]

Chris,

Without getting into too much detail (read Bill Pentz's website if you want that!), the minimum diameter of any part of your system will (more or less) determine the amount of air moved by the entire system*. So if you use 6" ductwork, but reduce it to 4" (even right at the tool), your system will perform just about the same as if you had 4" ductwork, as well. Thus, in order to get optimal performance, you need the equivalent area contained in a 6" duct all the way (including through the tool port, ductwork, exhaust port, etc). This may mean having to enlarge the ports on your tools, as most are 4", which is not sufficient to get good fine dust collection, no matter what the rest of your system looks like.

That said, a 1.5HP blower will likely not support 6" ductwork, either.

I'd suggest spending a good amount of time reading Bill Pentz's website. It will take awhile, but will undoubtedly save you from making many common mistakes.


(*assuming you are a 1-man shop, only using one machine at a time, and having one blast gate open at a time)

[David Kumm]

I think your plan is correct but you are using the wrong blower and motor. To run a 6" main line requires a bigger impeller than that . Talk to Pentz or Oneida and get it right. Factors include the distance of the runs, number of bends, amount of flex hose etc. While it is correct that a four inch gate at the machine limits the flow throughout the system, you will get restrictions and leaks at all the gates so you want a main line that uses the proper capacity of the blower. You may have to keep another gate partially open to bring enough air into the main line to keep the chip velocity up but that is a whole lot better than undersizing a system and getting crappy collection. Spend the time to understand how a system works given your layout and size accordingly. The extra money spent hurts once. A poorly performing system will annoy the hell out of you every day. Dave

[Aaron Rowland]

Surprised you didn't get more opinions. And opinions is what the answer to this question is made up with. So I'll give you mine. I assume you are using a bagger rather then a cyclone but I'll give my opinion both ways.

# 1- Ignore HP ratings. You can buy a so called 2HP blower with a 9.75" impeller from one dealer or a 12.75" impeller with a 2 HP motor from another. So always check the impeller diameter. Some dealers try to hide this number- Beware of these guys.

#2- Always use 6" duct work from the blower to the machine. No steps allowed. A 4" duct will cut CFM almost in half. If the impeller is to small to handle 6", it's to small for proper dust collection. The steps came from large industrial DC's but we don't use them and scaling doesn't work very well when dealing with air. I like PVC schedule S/D for many many reason. Some prefer metal, use either, I won't argue except only use 6" and that's a must if you want to pick up dust.

#3-Bagger impeller diameter- Minimum is 12.75"

#4 Cyclone impeller diameter- Minimum is 14"- 14.5". There is a cheat for small impellers like 14". Put the blower in front of the cyclone so it's a push though. That minimizes the cyclones pressure drop effect but you will have to replace damaged impellers if you do much work.

In this field 1/2" makes a huge difference in CFM!! The impeller is every thing. There is not that big a difference in basic Cyclones! The difference in numbers mainly come from the impeller diameters and filter drop. Ignore mag tests since they do not tell you how they tested it or the impeller diameter. Rumor has it that in some cases the supplier has slipped in a bigger impeller for the test. Also the filters have a huge effect on CFM .There is no data on pressure drop published that I know of.

The Pentz site agrees with most of my comments and I like what he says. But it's to dang long to read!

Do what I said and you will have a good system. Ignore it and you will replace it 2 years from now if you stay with the Hobby.

[David Kumm]

I am in agreement with Aaron. He said it better. The impeller is everything. It is a little more complicated than diameter, blade depth and configuration enter into the equation but the point is to find out what the cfm of the impeller is and size pipe accordingly. I would differ a little in using 6" on the verticals depending on the system. As you get farther away from the impeller and go past some drops and around some bends, your 6" pipe cfm may drop to where the velocity of the air gets marginal. If your machine has a 4" port and you have to pull large chips vertically the port in conjunction with prior restrictions might cause the vertical velocity to fall too low. In that case you care better to stay with a little smaller vertical. I usually drop after the elbow and reduce to spiral at that point. If you try to hook up two ports to the same machine you for sure need to keep the vertical pipes proportionate to the horizontal. I found a used anemometer on ebay to check cfm and velocity and use it to quantify my gut feelings. Plugging holes in the machine can help you out as well. Dave

[David Giles]

6" everywhere including machine ports.

Now wasn't that easy!

[Chris Atzinger]

Thanks for your responses. For anyone who loves details, and I would assume that is anyone replying to dust collection threads, here is what I have, and here is what I am considering. This is going into a new garage (we just bought a house).
-I have a 22'x 15' space
I use a
contractor table saw
Jointer
Planer
Drill Press
band saw
spindle and belt sanders
lathe
Miter saw

Here is my planned layout:
https://picasaweb.google.com/lh/photo/sOOGgFr6oIYlxxK7_3rW1UIF2c-3FZz4U0p0q2v1paE?feat=directlink

The green bars are the ductwork, the squares mark the drops near tools. This is where my initial question came from. Should the drops be the same diameter as the main lines or should I reduce since they are verticals, to maintain chip flow.

I initially thought that the smaller grizzly G0703P cyclone would work.
http://www.grizzly.com/products/1-1-2-HP-Cyclone-Dust-Collector-Polar-Bear-Series-/G0703P
It has a 13.5" impeller and sucks 775 CFM over 10ft of smooth pipe. It has a 6" inlet, and an optional 5" reducer

After the first few posts,

I thought an upgrade to the Grizzly G0440 2hp cyclone would cover me.
http://www.grizzly.com/products/2-HP-Cyclone-Dust-Collector/G0440
It has a 14.5" impeller, sucks 1354 CFM, and has a 7" inlet.

I have been reading as much as I can about this over the last few months, and the deeper into the rabbit hole I go, the more confusing it gets...

Thanks for your input and suggestions. It is appreciated.

-Chris

[David Kumm]

David, 6" all the way may be easy- if you can modify all the ports to 6", if you only use one port per machine, and if your impeller is sized to provide enough cfm to compensate for real world losses along the way. Get any of those things wrong and it won't be so easy to fix. Dave

[Dan Friedrichs]

#4 Cyclone impeller diameter- Minimum is 14"- 14.5". There is a cheat for small impellers like 14". Put the blower in front of the cyclone so it's a push though. That minimizes the cyclones pressure drop effect but you will have to replace damaged impellers if you do much work.


Like most stuff that Aaron posts, this is incorrect. Push-through or pull-through won't make any significant difference (the pressure losses occur equally on the exhaust side, too). And unless you are regularly sucking up rocks and tape measures, you won't damage your impeller, either.

[David Kumm]

Chris, I looked at your layout- 6 or 7 drops and machines that may not all take 6" ports. Go to the Oneida website and take a look at the fan curves for their various systems. They also show the expected operating ranges. CFM fan ratings are only good if you know the static pressure as well. My non scientific but experienced gut tells me the 2hp grizzly is as small as you dare go but I don't know how they rate their fans. Dust collection is important and the size of your system warrents doing it right. Talk to Pentz or Oneida and spend a little extra for the advice. Absent that I would err on the high side with a bigger unit. Dave

[Aaron Rowland]

Like most stuff that Aaron posts, this is incorrect. Push-through or pull-through won't make any significant difference (the pressure losses occur equally on the exhaust side, too). And unless you are regularly sucking up rocks and tape measures, you won't damage your impeller, either.

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I don't make up stuff and you have never been able to prove me wrong. I do note that I also have rarely seen any posts by you giving out new ideas. Your posts are almost all negative comments. Baldor Motors proved you dead wrong on my OP on bleeder resistors. You sure didn't argue with them when proven wrong.

It's good however that comments be challenged if you don't understand them. In that way the OP has a chance to present his case and maybe some one can learn something from the exchange.

So the argument is- does it or does it not make any difference in CFM if the blower is placed before or after the Cyclone. I claim it makes a huge difference if the blowers impeller remains the same size. You didn't mention impeller size which indicates to me you have no concept of why the position of the blower and size of the impeller is important and no idea of what you are talking about.

So can you tell us why a pull through cyclone uses a bigger impeller with a given size motor then a push though Cyclone or single stage blower ?

All the Hobby type Cyclones we buy are pull through for good reasons. If you check the single stage blowers sold you can get a good idea what size impellers are used for various HP motors. That is of course if the HP numbers are real. Then if you take the same HP motor installed in their cyclones you will notice something very obvious- The impeller is about 10% larger in a cyclone then in a single stage blower using the same size motor. Why would this be? Both systems have similar CFM and with a given size motor should flow the same amount of air regardless of the system it goes in according to you with the same size impellers. But it doesn't work that way.

The reason a pull though Cyclone uses a bigger impeller is because the impeller is operating in less dense air because of the pressure drop of the cyclone. The impeller is running in a partial vacuum compared to a single stage blower or push through cyclone and to compensate requires a larger impeller. It's that simple.

In a push though cyclone the impeller does not see less dense air cause by the cyclones pressure drop and it uses the same size impeller as a blower with out the cyclone. If you put the larger impeller in front of the cyclone, as in a push through, the motor will be overloaded and burn up.

It's simple to verify these facts with a Shop Vac. Put a ammeter or Watt meter on the line cord and observe what happens if you place your hand partially over the inlet. You will notice a rapid and severe decrease in amps or watts. The induced decease in air density results in a tremendous decrease in CFM. Now if you place your hand over the exhaust a very small change in power results. This proves that blowers are much more sensitive to inlet pressure then exhaust pressure.

So you are dead wrong again in your criticism of my post. If what I have posted is incorrect about diameter please show me where. Your only experience with DC's appears to be with the 1HP , 9.75" diameter HF blower.

I would appreciate a polite rebuttal without insults or smart remarks, Thank you.

[Tom Willoughby]

I am at a similar stage to Chris in that I have received a ClearVue cyclone and have just ordered 6" S&D pipe for the main lines in my workshop. I am planning on putting 6" flex tubing to each tool, which makes perfect sense when dealing with a single dust collection port. My question is whether I have to reduce the diameter of the drops when 2 drops are used for a single tool? For example, I am planning on collecting dust above and below my table saw and at my router table. Will it drop the CFM too low by running two 6" lines to a single tool?

Thanks.
Tom

[Leo Graywacz]

I have a system that is similar to what you are describing. I used a short 7" main that dropped to 6" for the main trunk. I have 5" drops going to my machines so I can have more than one gate open at a time. You need to look at what the specs are for the machine you are attaching the DC too. If you put 800 CFM on a machine that only requires 400 CFM then you are wasting power and some machines actually do worse when you have to much vacuum on them (My Jet 15" planer leaves more chips when I have to much suction on it rather than the 450 CFM they recommend). You can balance your system and put the correct amount of flow on each machine by ducting it with the right size ducting.

Here is my system. As I said, the drops are 5" and most have a 5"-4" reducer to match the port right at the machine port.

http://fototime.com/45357C42ECC2980/orig.jpg

[David Kumm]

I would run 2 4" lines. Drop 6", then branch to two 4". You want the vertical velocity at about 4000fpm and the horizontal at 3500 approx. Unless your system is so powerfull that you are pulling 6000+ fpm on the 6"- which begs the question "why use 6?" when you split the air flow you will get too much drop in velocity . Two 4's = a 6, two 5's = a7 approx. My guess is Pentz knows his systems so well he can tell you what velocity you will get assuming the length of run, number of bends, and length of flex hose. If you know that, you know how big you can size the verticals. The fan blade type annenometers are great. I found a used one on ebay for about $100. Invaluable for setting the paint booth and finally figuring out what I really had with dust collection. Dave

[Tom Willoughby]

Thanks Dave. I see that most people use 2 x 4" branches when connecting back to a 6" main to maintain adequate airflow. I have SawStop guard on the table saw that has built in dust collection but the diameter of the hole is very small and I doubt that much air would move through it so maybe I'll leave the bottom port at 6" and go with a 4" drop to the tablesaw guard. I'm pretty sure that the SawStop guard was designed to be used with a shopvac and the air turbulence created by the blade.

Unfortunately, I don't have annenometer so I'm working with theoretical optimization at the moment.

Thanks.
Tom

[Tom Willoughby]

Thank you for the picture Leo. Everything that I have read mentioned to go with the appropriately sized ducting right to the machine and to modify the machine (typically enlarge a 4" port to a 6" port) to ensure adequate dust collection. I had not heard that too much suction could actually be worse than what the machine was designed for. I'm a one man show so I'll only be using one machine at a time so at most I'll have 2 gates open for those tools that collect on the bottom as well as the top.

Thanks.
Tom

[Leo Graywacz]

I am a one man show myself and I use two to three machines at the same time. Usually the planer/jointer jointer/tablesaw or jointer/tablesaw/edgesander. I have it setup so I can push a board through the jointer spin around and push the part through the TS. Handling the part only once.

[Tom Willoughby]

You sound very organized Leo. I start and stop my dust collector with each machine. I also look at the plans in between machines and sometimes go get a coffee. Only weekend "work" here and definitely not production.

[David Kumm]

Tom, you should be fine. Tablesaws shoot sawdust that moves easily compared to chips from jointers and planers. I had a planer that left strings over an inch long as chips. That machine really needed both suction and flow to work. Great planer though. Dave

[Leo Graywacz]

You sound very organized Leo. I start and stop my dust collector with each machine. I also look at the plans in between machines and sometimes go get a coffee. Only weekend "work" here and definitely not production.

This is my job and how I make my living. Turning machines on and off especially if you are going to be using them in the next couple of minutes isn't worth the effort of pushing the switch. My DC states that it shouldn't be turned on more than 8 times in an hour (I think). So when I turn it on I will leave it going for 10 minutes or so before I shut it down.

I am pretty efficient at processing parts and have my systems down pretty good. When I invite other tradesmen into my shop when I am working on their projects I always amaze them at how fast I do things. And it is a perception thing, as fast as I seem to move I think it is too slow and there are too many steps to do things. But they always comment on how quick things get done.

[John Petsche]

Great pics