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Dust collection, plastic or steel plumbing. How large?

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Forum topic by b2rtch posted 07-07-2010 02:52 PM 6568 views 0 times favorited 77 replies Add to Favorites Watch
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b2rtch

4822 posts in 2510 days


07-07-2010 02:52 PM

Topic tags/keywords: question

I have been reading about how to install my dust collector and the piping/duct work.
I read several place that “plastic” piping should not be used because of the static electricity concern.
I was planing on using ABS or PVC.
Is this a real concern?
What is your experience?
What do you think about this?

Addtion:

I am reading Bill Pentz’s blog.
He writes that 4.00” duct is really not large enough to move enough air to get the small wood particle (the most dangerous for our lungs) out. He recommends to run at least 6.00” duct.
Is this overkill?
What do you think?
Thank you.
Bert

-- Bert


77 replies so far

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PurpLev

8523 posts in 3110 days


#1 posted 07-07-2010 03:22 PM

for small shops and the smaller DCs (and cyclones) this really does NOT warrant any issues, worst case you’ll get some light static charge on the outside of the pipes. the real concern is when you use the high load industrial machines in large shops that have a lot of fine dust in the air.

that aside – I think PVC are OK to use in the shop, but since you are planning to install those concealed and permanently under the floor – might as well go the extra step and use metal plumbing for the efficiency of it as the metal plumbing interferes less with the air flow and is has smoother walls.

mind you – depending on the DC that you use, and the runs that you intend to install, 4” pipes may or (more likely) may NOT be the best size. 6” may also NOT be the best size if your DC cannot support the airflow.

planning a proper DC system takes time and preparations to make sure you do it right.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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BertFlores58

1684 posts in 2384 days


#2 posted 07-07-2010 03:38 PM

Any system will do provided you have the screen filter on every suction point.. 4 inches is quicker than 6 inches. The voilume that you have to pump matters with the time. It is just like the compressor. Shavings for example can clog your system if it forms like a ball of 6 inches. NOTE: BENDs specially sharp bends reduces pressure.

-- Bert

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jusfine

2405 posts in 2387 days


#3 posted 07-07-2010 03:40 PM

For a few bucks, an HVAC engineer can size your ducting according to the cfm of each machine and capability of your collector.

Use the search function, I found when I asked a few questions about DC systems, a lot of it has been covered here over the years and there have been really good threads earlier.

I agree with the plastic pipe, should not be an issue in your situation.

My DC is running under the shop floor as well, fittings should be ready this week and installed on the weekend… (keeping my fingers crossed).

-- Randy "You are judged as much by the questions you ask as the answers you give..."

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b2rtch

4822 posts in 2510 days


#4 posted 07-07-2010 04:18 PM

I have been designing/working around hydraulic and pneumatic systems for many years.
I can see that there is a limit on how big a duct I would want to install because as I increase the diameter I reduce the air velocity and I believe that the velocity is what carries the chips away.
As much as possible, without reducing the diameter so much that my ducts will clog all time, a smaller diameter should be better as the air velocity is higher.
Now I also have to dial in the pressure drop and other restrictions due to the fittings.
I use the HF 2HP dust collector. It has a 6.00” port.
I think that I am going to install a 6.00” main duct with 4.00” branches and that everything should work fine.

Now the next issue is that to install a 6.00’ duct on the concrete slab and to build a floor on the top of it will require using at least 2.00”x8.00” lumber.
Does nay one know about rectangular plastic ducting?
May be 4.00×6.00 which would allow me to use 2..0”x6.0 instead?
Thank you.
Bert

-- Bert

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sawblade1

754 posts in 2488 days


#5 posted 07-07-2010 04:39 PM

I would personally go for metal ducts and get away from plastic at any means possible also if you insist placing it in the floor please plan for cleanouts and do not go under 6” dia. pipe. running it overhead you don’t loose much height, cleanout is a snap literally, and your D/C can pull in chips not lift them out of the floor. By pulling chips out of the floor EX. the 6’ run to D/C plus a straight 90 degree elbow adds approx 15-20 feet of pipe cfm to a system.

-- Proverbs Ch:3 vs 5,6,7 Trust in the lord with all thine heart and lean not unto your own understanding but in all your ways aknowledge him and he shall direct your path elmerthomas81@neo.rr.com

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b2rtch

4822 posts in 2510 days


#6 posted 07-07-2010 04:41 PM

Thinking about what I wrote , I realized that to have a 6.00 main duct with 4.00”branches would be a mistake, counterproductive and a cause for problems as the flow coming from one machine would enter the main duct the velocity would drastically drop causing the debris to fall and to lay on the bottom of the main duct.
I believe the keeping the duct diameter constant would be better.

-- Bert

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jusfine

2405 posts in 2387 days


#7 posted 07-07-2010 04:52 PM

Bert, almost every system I have seen begins with a larger main run, with smaller ducts running off of it.

Mine has a 7” main, with 5” and 4” runs under the joists.

My DC sits on the main floor (shop is in the loft) so it pulls the dust / chips as if it was installed with overhead ducting, but installing 30 degree elbows in your case should help.

-- Randy "You are judged as much by the questions you ask as the answers you give..."

View SteveMI's profile

SteveMI

954 posts in 2756 days


#8 posted 07-07-2010 04:54 PM

Bert – Technical question. I also have a HF 2hp DC and some tools that are sized for shop vac 2 1/2” hose. I use the full 6” with hose for table saw, planer and v-drum sander. For the others (router, miter saw, band saw) should I reduce to 2 1/2” at the input to impeller?

My shop doesn’t allow me to have fixed piping, so moving the DC and tools is how my life goes.

Steve.

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ClayandNancy

511 posts in 2477 days


#9 posted 07-07-2010 04:58 PM

Alot depends on what tools you are using and the cfm required by them. You didn’t say which DC you have, that will also effect the size of your pipe. b2rtc is right with a 6” main and 4” branches, there’s alot of people that have the HF DC and will probably jump in here. Go back to Pentz site again and use his calculations to figure it out. Never heard of anyone using square vent??? Plastic is the way to go. Easy to change and add on when necessary.

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PurpLev

8523 posts in 3110 days


#10 posted 07-07-2010 06:05 PM

FYI… check Bill Pentz requirements for the motor spec and blower size in order to utilize 6” ducts… quite a bit higher than the HF 2hp DC…

and no – you should NOT use rectangular ducts for DC. those are good for PUSHING conditioned air and air alone – but not designed for PULLING dust. you’ll need circular ducts that have minimum drag on the air flow.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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b2rtch

4822 posts in 2510 days


#11 posted 07-15-2010 05:23 PM

I was still debating about using steel or plastic ducting.
I would recommend to anyone who has an opinion about this to read this article:

http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html

I am now 99% sure that I shall use “plastic” ducting

-- Bert

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PurpLev

8523 posts in 3110 days


#12 posted 07-15-2010 05:29 PM

Bert. the benefit of metal is not the grounding although that is a nice small benefit that comes along the way.

metal ducts have a much lower air resistance than PVC and bottom line – provide with a higher CFM to your machines.

here’s the thing. in my book – one should use metal ducting as those are dedicated for that purpose. now – ask yourself, for what reason would you NOT use metal ducting?

the only reason that comes to my mind is $$$ – PVC is by far more affordable. so the question remains – are metal ducts out of budget?

if they are – use PVC, it’ll work, as many people use it. I wouldn’t even worry about grounding as for small shops it really isn’t that major.

But – if you are building something for the long run, and plan on efficiency – I’d go with metal ducts.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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b2rtch

4822 posts in 2510 days


#13 posted 07-15-2010 05:38 PM

Why would a metal pipe be more efficient than a plastic pipe of same ID?
In fact, since I have been working with both, I believe that PVC or ABS is probably smoother than metal and so creates less turbulence and a better flow ( I could be wrong).
Three reasons to go plastic: price, availability and ease of installation and modification later on (OK that make four reasons).

-- Bert

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sawblade1

754 posts in 2488 days


#14 posted 07-15-2010 05:53 PM

plastic pipe has thick walls and take up CFM area making it less efficient Static electricity is a bad concern also metal ducting is the way to go, avoiding connector issues from under/ oversized PVC pipe I was a plastic process tech for years and die swell from an extruder can vary .10 up to .50 and be a real pain with plastic D/C fittings. the cost you save per ft of plastic pipe you will spend on connector to make it up at blast gates etc. BTW the cost of grounding PVC pipe depending on how long it runs can add to the cost also.
to answer your other question on square ducts simply put is NO sawdust can and will lie in square duct as it needs to be moved like water in a pipe not like a conveyor the roundness also helps keep build up down and minimizes high impact jamming of large chips and keeps things easy to clear
Keep us posted:)

-- Proverbs Ch:3 vs 5,6,7 Trust in the lord with all thine heart and lean not unto your own understanding but in all your ways aknowledge him and he shall direct your path elmerthomas81@neo.rr.com

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b2rtch

4822 posts in 2510 days


#15 posted 07-15-2010 06:05 PM

SAwblade1, did you read this:

http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html

If I use PVC or ABS I shall not ground it.
If I ground it it would only because I got tired of getting shocked.

By the way this article also answer those who told me that I should not install my dust collector outside, the code seems to say that a dust collector has to be installed outside.

-- Bert

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