DC Ducting

Darren Wright

Administrator
Staff member
Messages
20,088
Location
Springfield, Missouri
I'm looking at picking up the HF 2hp dust collector tomorrow. Just curious if anyone has ran rigid ducts for this using pvc? If so, what size did you run (4", 5", 6")? Did you use Schedule 40 pvc or the thin walled pvc?

Also, do you glue the joints? I was considering drill and screwing them so that i could re-configure if needed.

Thanks
 
My setup is with a Jet 1.5hp DC and Wynn cartridge is all 6" as far as possible, then 4" and flex as little as i can. I didn't use PVC because at 6" the fittings made my wallet cringe. I went with 6" snap-lock HVAC ducting - the cheap stuff at HD. The only trick was the crimps on the wyes are backwards - it was worth buying the crimper to turn 'em around, for me.
 
Hi,

When I started my dust collecting system I hit the web, libraries, purchased books, looked at magazine articles, etc., etc. I perused information for 2 or 3 months. I ended up runing 6" schedule 35 sewer and drain everyplace except the drops to the machinery. The schedule 35 was definite overkill. Don't get me wrong; I am glad I did it. However, I am sure that I spent more money than I needed to. Glenn found some ducting that is smooth inside (SMOOTH INSIDE IS CRITICAL. If not smooth it raises absolute heck with your efficiency. It has been a long time since I did the figuring. However, as I remember you have to have three times the dust collector to get the same result as you would if the ducts were smooth.) and lighter weight and less expensive. Ask him. That's what PMs are for.

My 2 hp dust collector does the job. It does it well. However there is absolutely no surplus "suction" to waste on right angle turns, flexable ducting, and other no-no's. It is Penn State 2 hp double bagger. It is quite inexpensive for a DC. I don't have a Penn State catalog to look for the model. If you really want to know, let me know, I can find it in my paper work or on the web.

Do NOT glue your joints. I will give you a written guarantee that you WILL move things around. If you glue it and change your mind you have to saw the joint out and throw it into the recycle. I have never had a problem with my friction fit joints---in fact I cuss a bit when I take one apart. I do not have a drop of glue in my entire system (2 bandsaws, TS, thickness planer, DP, Lathe, 12" disk and belt sanders, etc.) The wood lathe is my largest problem; I cannot create enough air movement over a large enough area to be really efficient. My ducting drops down to two 2.5in "move and stay put flex" ducts that I can place right where the cutting is occuring. They are in the way whenever I want to move the tool rest or darn near anything else. The only real answer appears to be to get a larger DC unit.

I don't think the PennState unit is much more money than the HF. It is trememdously more healthy however. It has 1 micron bags. The last time I looked the HF was 3 micron bags. It is that tiny stuff that raises heck with the alveoli in your lungs. If the DC is in a room you can close off, away from you, or exits outside, this is not a factor.

Do NOT make any right angle turns. They are efficiency robbers. Use two 45* angle ells with a piece of pipe coupling them to make a much softer, more efficient turn. Some companies make "long radius" 90* ells; these used to be quite expensive however. Don't try to be "pretty," think efficient instead. What are the shortest possible runs I can make without interferring with machinery, lighting or whatever.

I have written quite a few threads and posts about DC in FWW. Do a search for them under Jim C Bradley. I have not done a search since FWW has been updated so I am no help to tell you how. If you cannot find them, let me know and I will see what I can do.

It is your lungs and your life. To a certain degree you are looking at a trade off between money and how long you will live a healthy life. Put your money into your DC now; buy your pretty new tools later. Sorry, but I really get off on a rant about DC and healthy living for you and your family.

Enjoy,

JimB

My e-mail address will be changing in a few days. I do not know the new address yet. jandmbradley@cox.net will be good for a bit.
 
For the HF my off the cuff experiments show that 6" works, but is low on velocity so bigger chunks had a lot of hang time, 5" was a lot better. This was on really short (6' and 10') runs so I reckon longer would be worse. The stock inlet on the HF unit is 5" unless you modify it.

In the end I ended up re-organizing my machine layout and just using an 8' piece of 5" flex and moving it around, which is a pain, but works pretty well.

I ended up adding the $160 Wynne filter to mine so I was a bit over $300 all told for the unit itself (not counting duct). Looking around more I've seen a few larger 2HP and 3HP machines for competitive prices used, doing over I'd probably wait and get one of those (pretty much requires 220 though).
 
...The wood lathe is my largest problem; I cannot create enough air movement over a large enough area to be really efficient...

Jim, I don't know of any woodturner on the planet who has figured out how to collect dust efficiently at the lathe. You will always have some dust that gets away, regardless of the size of your DC. ;)
 
Thanks for the replies all! Have to order some things, so have some more time to research and decide what I want to do. Would like to do a 5" main, but the location of the DC may allow me to do 2 shorter runs of 4", still thinking this through though.
 
Go ahead and run 6" from as close to the DC to as close to the tool as you can. Use Wyes, not Tee's. Use dual 45's, not 90's. No sudden changes in direction. Think long sweeping curves; not really possible but, it keeps your mindset focused ;-)
 
Also, do you glue the joints? I was considering drill and screwing them so that i could re-configure if needed.

Thanks
Ditch the screws and use duck tape instead. Seals the joint from leaking and holds it together plus easy to remove for layout changes.:thumb:
The screws will stick into the pipe making for great places for things like that oppps shop rag to hang up on.:thumb:
 
Go ahead and run 6" from as close to the DC to as close to the tool as you can. Use Wyes, not Tee's. Use dual 45's, not 90's. No sudden changes in direction. Think long sweeping curves; not really possible but, it keeps your mindset focused ;-)

I doubt I'll be using more than a single 4" at any give time. CFM is larger with a 5 or 6" line, but won't velocity be increased with the smaller line?

Ditch the screws and use duck tape instead. Seals the joint from leaking and holds it together plus easy to remove for layout changes.:thumb:
The screws will stick into the pipe making for great places for things like that oppps shop rag to hang up on.:thumb:

Good point...Thanks! :thumb:
 
Ohhh is that why it's called duct tape....:rolleyes:
Well according to the HVAC code you have to use duct tape on duct work. If you put duck tape on it the inspector can make you change it.:thumb::thumb:
"The product now commonly called duct tape should not be confused with special tapes actually designed for sealing heating and ventilation ducts: this is not recommended by manufacturers. To provide lab data about which sealants and tapes last, and which are likely to fail, research was conducted at Lawrence Berkeley National Laboratory Environmental Energy Technologies Division. Their major conclusion was that one should not use common duct tape to seal ducts. (They defined duct tape as any fabric-based tape with rubber adhesive.) The testing done shows that under challenging but realistic conditions, duct tapes become brittle and may fail.[2] Commonly duct tape carries no safety certifications such as UL or Proposition 65, which means the tape may burn violently, producing toxic smoke; it may cause ingestion and contact toxicity; it can have irregular mechanical strength; and its adhesive may have low life expectancy. Its use in ducts has been prohibited by the state of California[3] and by building codes in most other places in the U.S. However, metalized and aluminum tapes used by professionals are still often called "duck/duct tapes"."
 
another vote for the PVC sewer type pipe for ducting and no glue on joints, the main runs i have under the concrete were because didnt want them to open up when the floor went in.. but the rest is friction.. and also go 6" as far as you can before you go to 5' or 4". on my recent sander DC upgrade i used schd 40 pvc but wished i had got the sewer and drain couldnt find any at the time.. better pricing on the thinner stuff darren..
 
Well according to the HVAC code you have to use duct tape on duct work. If you put duck tape on it the inspector can make you change it.:thumb::thumb:
"The product now commonly called duct tape should not be confused with special tapes actually designed for sealing heating and ventilation ducts: this is not recommended by manufacturers. To provide lab data about which sealants and tapes last, and which are likely to fail, research was conducted at Lawrence Berkeley National Laboratory Environmental Energy Technologies Division. Their major conclusion was that one should not use common duct tape to seal ducts. (They defined duct tape as any fabric-based tape with rubber adhesive.) The testing done shows that under challenging but realistic conditions, duct tapes become brittle and may fail.[2] Commonly duct tape carries no safety certifications such as UL or Proposition 65, which means the tape may burn violently, producing toxic smoke; it may cause ingestion and contact toxicity; it can have irregular mechanical strength; and its adhesive may have low life expectancy. Its use in ducts has been prohibited by the state of California[3] and by building codes in most other places in the U.S. However, metalized and aluminum tapes used by professionals are still often called "duck/duct tapes"."

We had other uses for the duck tape at the airlines... whenever the skin of the aircraft would get punctured, the mechanics would put a strip of the aluminum tape over the hole and send the plane on to the next station.:eek:.. eventually it would get to a station that had a machine shop and could replace the punctured skin area with regular aluminum skin.:thumb: I saw one aircraft that flew for a couple of months with a strip of tape on the side just forward of the forward cargo bay door.:huh:
 
We had other uses for the duck tape at the airlines... whenever the skin of the aircraft would get punctured, the mechanics would put a strip of the aluminum tape over the hole and send the plane on to the next station.:eek:.. eventually it would get to a station that had a machine shop and could replace the punctured skin area with regular aluminum skin.:thumb: I saw one aircraft that flew for a couple of months with a strip of tape on the side just forward of the forward cargo bay door.:huh:

We Called it 300 mph tape Chuck used it a lot on the Metro II and the SAAB
 
We had other uses for the duck tape at the airlines... whenever the skin of the aircraft would get punctured, the mechanics would put a strip of the aluminum tape over the hole and send the plane on to the next station.:eek:.. eventually it would get to a station that had a machine shop and could replace the punctured skin area with regular aluminum skin.:thumb: I saw one aircraft that flew for a couple of months with a strip of tape on the side just forward of the forward cargo bay door.:huh:

In Vietnam, we used it for 'emergency' helicopter battle damage repairs. Slap a piece of tape over bullet/shrapnel holes in the skin, write "WIP" (work in progress) on it with a magic marker, and send the bird back out. Some of those patches were on there for months before getting a 'proper' repair. I've even seen that stuff used to repair the leading edge of a helo's rotor blades.
 
There are really two components to the math behind dust collection. CFM and FPM - the first indicates the volume of air that can be moved by the DC, the second is a measure of the VELOCITY of the air that is being moved. For dust to be collected, and dust is the primary concern, it MUST remain suspended for it to be moved and collected - this takes velocity measured in feet per minute. I will check my old engineering notes but I think I recall the need to keep the air that is being moved, at a rate - at or above 4000 fpm. Essentially what this means is that given the value of your DC usually noted in CFM, the size of your pipe can be calculated to create the needed VELOCITY. A larger pipe may move more volume, BUT - may actually allow the velocity to drop below the desired min of 4000 fpm. If there is a real interest in this I will try to find my notes. I know - I have only opened up more questions for those planning their systems. BILL
 
Top