DC piping questions

[prov163]

I just added a new DC to my shop. Im planning to get some 4” pvc to hard pipe it. I have a few questions:

This is the new shop setup. My new Rikon 10-326 bandsaw is going to be between the jointer and DC. 

This is the pipe I was using before. I’m going to replace the blast gates (another question down the line)

As you can see, the black pipe runs from my table saw under the outfeed/assembly table. It’s about 7’ from the back of the saw to the back wall. Do I need to replace the black pipe with pvc or can I just run this to the pvc at the back wall? What I mean is will I improve the efficiency enough by running pvc all the way to the machine to make it worth the hassle? Moving the table is a no go. 

I’m planning to put blast gates directly on the DC ports because they will be easy to access. I’ll put another one between the bandsaw and jointer. I won’t be running any more than one tool at a time. Drawbacks?

Thanks for your help!

[krtwood]

If you're going to use that wye that's on the DC then the blast gates there are a good idea.  When I had that kind of setup the chips from the planer would find their way into the other side of the wye and start to clog it up.  Then when you go to use the other side either you get a big wad of chips going all at once or you get to take it apart to clear the clog.  So the gate will at least keep the clogging contained, if that becomes a problem.

My intuition is that the dust collection at the table saw is going to be slightly different shades of better than nothing either way but I can't speak from experience there.

[Chet]

The only thing I would add as far as you table saw connection - the straighter and smoother the inside surface of you pipe from you saw to the DC is the better results you will get.  But I guess only you can decide whether it is worth the trouble. 

[fcschoenthal]

In dust collection, the straighter and shorter the better and PVC (with the smooth inside) is better than the hose. Personally however, I would never run PVC directly to a machine. I would leave a hose connection just in case I need to move it even a little. Running some pipe from your DC along the wall past your assembly/outfeed table and then a hose to the saw would be a good way to get it out of your way more when you're at the table.

Right now I don't have piping setup (still trying to figure out where to put everything), so I have two hoses connected to the DC with blast gates like you're thinking about. I have one mounted to the saw and the other I can attach to the machine that I'm using. It's worked great for me so far. I only have to remember to close one gate before trying to use the other hose.

Chris

"It's never too late to have a happy childhood"

[Brendon_t]

Agreed with above that I would replace a good bit of the flex pipe with rigid pipe but leave 18" or so of flex at the end so that you can make small movements, sweep under/around..

[Chestnut]

This is minor but will still have an impact. The circled connections from the blower to the can thingy are pushed on a bit too far. You want a nice sweep curve in the flex line here. I understand the thought to make sure they are on the securely but you only really need enough flex tube to cover the ridge and leave enough from for the band to go around. You could back both connections off a bit.

[prov163]

Great advice guys.  I am going to run flex from machine to PVC in all areas.  I am not using the ole wye.  I had to use it previously as the collector only had one port.  Chestnut, I did put those on like water hoses on an engine - get as much surface connection as possible.  I will back those off a bit.

[Jfitz]

I'd consider re-mounting the impeller section so you could use a piece of straight pipe from the impeller to the bag/filter assembly.  If that's not in the cards, then +1 to what Chestnut said about adjusting the flex pipe to make it as gradual a curve as can be.  Would be great if it could be replaced with a single  bend of smooth wall pipe.

[Chestnut]

1 hour ago, prov163 said:

Great advice guys.  I am going to run flex from machine to PVC in all areas.  I am not using the ole wye.  I had to use it previously as the collector only had one port.  Chestnut, I did put those on like water hoses on an engine - get as much surface connection as possible.  I will back those off a bit.

Only reason i mention it is the tighter turns will create some turbulence entering the separation area and it will negatively effect the separation. It will also decrease the flow a bit.

[Carl10]

prov,

With most 1.5HP-2HP units and small runs you are better off using 5" HVAC ducting. Out of the box with 4" ducting you will be starting with ~575CFM and reducing it with every foot of 4" pipe you add. With 5" you will probably start ~675CFM. You will have ~50% more duct area with 5" (6" is too big).  With your short runs the cost is only slightly more.  Here are some sources for material (whatever size you use):

Blast gates and hose are available here 5" Aluminum ~$12 http://www.blastgateco.com/Cast-Alum...last-Gates.php

Wyes here ~$13 http://www.simplyplumbing.com/27013-smoke-flue-wye.html (these are actually longer than pictured ~24")

and here ~$20 http://thesheetmetalkid.com/wye-bran...duct-fittings/

or

 https://www.kencraftcompany.com/product/24-gauge-45-degree-sheet-metal-wyes/

 

 

Ducting: 5 pack of 26 gauge

 

https://www.grainger.com/product/GREENSEAM-Snap-Lock-Pipe-6PGC8

 

Hope this helps.  Let us know what you do.

 

Carl

[Jfitz]

1 hour ago, Carl10 said:

Out of the box with 4" ducting you will be starting with ~575CFM

Carl - generally I agree, but this very much depends on the DC unit.  The starting point could be higher, or much much lower....

I'm curious where you get these numbers - again, I generally agree but your numbers are fairly specific so I'm curious.

 

 

[Chestnut]

Thanks for bringing that up Carl you make a good point. I even thought about suggesting 6", I wasn't sure where the first wye would be and how far the runs would be. I agree with fitz on the numbers though. It's possible to get more air through a 4" pipe but the pressure loss is going to be high. If you are going to split 2 directions directly out of the unit i'd go 5" if you are going to have some strait pipe before the first wye i'd do 6" and then split after that. I know you are redoing your layout. If it's possible try and change your layout so that you don't have to do a wye directly at the tool instead have a single main branch the collection will be immensely better that way.

I'd for sure run solid pipe to as close to your machines as possible.

[Carl10]

Jfitz,

I had the same unit several years ago and the unit has been tested by wood magazine among others. So fan curves are available to get performance numbers. Generally,  1.5HP-2HP units have 11-12" impellers (HF is the exception with 10") will get choked down with 4" ducts and they can't produce enough CFMs in 6" ducts to maintain a high enough velocity, so 5" ducts are the best balance.

 

Carl

[Jfitz]

8 minutes ago, Chestnut said:

if you are going to have some strait pipe before the first wye i'd do 6" and then split after that

Could be a good idea, but you do run a risk that the linear speed of air will not be enough to keep the dust moving.  This is the tradeoff - you might get a little more CFM with a 6" pipe, but since it has such a bigger x-sectional area, the actual linear speed could drop.  Generally 3500-4000FPM (feet per minute) are needed to keep dust in suspension.  I've always thought this to be more relevant for vertical sections, since it'd be easier to keep the dust moving along a flat/horizontal section.

If the unit has a 5" inlet (before splitting to 2 4" openings), I'd suggest keeping with 5" "Mains" along the floor and then downsizing to 4" only when needed.

FWIW, here's a link to a review from years ago comparing results from different units with different size pipes - with actual curves of CFM versus SP loss.  Good food for thought.

http://www.portercable.com/uploads/PCD/Documents/News/182DustCollectors.pdf

 

 

 

[Jfitz]

4 minutes ago, Carl10 said:

Jfitz,

I had the same unit several years ago and the unit has been tested by wood magazine among others. So fan curves are available to get performance numbers. Generally,  1.5HP-2HP units have 11-12" impellers (HF is the exception with 10") will get choked down with 4" ducts and they can't produce enough CFMs in 6" ducts to maintain a high enough velocity, so 5" ducts are the best balance.

 

Carl

Excellent!  I was hoping you'd say something like that.  I'm familiar with that review (I just posted above a link to it) and it's a pretty good source of data.  Too many times I read the statement that you can never get more than 400CFM through a 4" pipe - like there's some sort of relativistic effect preventing it.  That review was a good source of data and shows (to me, at least) that you can get pretty good results with 4" pipe and the right DC unit.

[Chestnut]

16 minutes ago, Jfitz said:

Generally 3500-4000FPM (feet per minute) are needed to keep dust in suspension.

This is for vertical. With the main being horizontal i want to say Pentz notes keeping dust in suspension all the way down to 2800 fpm. 2800 FPM is 550 CFM in a horizontal 6" main which that DC should be capable of if your only running 1 tool at a time and running 6" to as close to the collection point as possible to keep pressure drop to a minimum.

http://billpentz.com/woodworking/cyclone/ducting.cfm#faqs

This really has more information than any one needs and half of it you have to be an engineer to understand. I'll take this guys word over a WW mag that is being paid by the manufactures to do the tests I mean no offense to the WW mag. Also that article doesn't really account for a filter over a bag which is going to allow for more air flow. All of their flows are shooting for that 4000 fpm that is needed for vertical runs not horizontal.

[Jfitz]

Agreed on FPM for vertical, agreed on BP site, and agree with cannister filter over bag filter, but slightly disagree on the article/review.  It's about the only one I've seen that actually measures airfllow, with longer pipes (higher SP), and with a filter on it ( a vendor advertising max CFM with no pipe and no filter is basically saying what a great fan it is).  And it clearly shows not all DC units - even at the same HP - are created equal.

I didn't realize 2800FPM for horizontal was 'good enough' - I probably read it somewhere but forgot.  Makes me rethink changing out my main lines for 6" pipe.....hmmm....

[Chestnut]

7 hours ago, Jfitz said:

Agreed on FPM for vertical, agreed on BP site, and agree with cannister filter over bag filter, but slightly disagree on the article/review.  It's about the only one I've seen that actually measures airfllow, with longer pipes (higher SP), and with a filter on it ( a vendor advertising max CFM with no pipe and no filter is basically saying what a great fan it is).  And it clearly shows not all DC units - even at the same HP - are created equal.

I didn't realize 2800FPM for horizontal was 'good enough' - I probably read it somewhere but forgot.  Makes me rethink changing out my main lines for 6" pipe.....hmmm....

I'm VERY cynical though and don't trust stuff that has ad money or hands in others pockets. That's on me. I did look through it again and it's one of the better reviews out there but the top recommendation being a grizzly come on that's fishy . Even if they claim to be unbiased i believe the are trying to be but you can't tell me there isn't any bias unconsciously put in to it. Hell i do that myself, festool is awesome right? :D

As far as the FPM and the 6" vs 5" vs 4". It's a very odd relationship. The 4" will keep the velocity up but cost more in static pressure and move less CFM so if you assume that same CFM in a 6" it can seem like it's not going to work. With the increased pipe size that static pressure can go down significantly and allow for more air flow better collection and still have enough velocity to clean. The key is to take 6" to as close to the tool as possible.

[Jfitz]

Making it worse, the SP loss calculation (per foot of pipe) is dependent on air velocity - so going to a 6" pipe should reduce air velocity which can be calculated, but since SP loss will drop the overall CFM should increase slightly.    Whatever - I'm with you on the 6" in this case as long as he doesn't need to go vertical.  6" along the floor at the base of the wall should be a good 'main''.  

[Chestnut]

Even if it's running up high and you need drops just have the drops be 4". I probably get a bit to excited about this stuff. It's not that I'm a huge dust fanatic i just really enjoy fluid dynamics.

[Jfitz]

1 hour ago, Chestnut said:

Even if it's running up high and you need drops just have the drops be 4". I probably get a bit to excited about this stuff. It's not that I'm a huge dust fanatic i just really enjoy fluid dynamics.

It is pretty fun stuff to understand.  I went with 4" smooth pipe for my system - 5" would have been ideal but I didn't want to spring for metal ducting at that point.  6" seemed like overkill but now you have me thinking about upgrading to 6" where possible if I ever re-do my shop and DC.

[Chestnut]

If it ain't broke!

[Coop]

I had no idea that DC could be that involved. I thought if it didn’t suck enough, then more hp

[prov163]

That’s it, I’m quitting woodworking   I run a museum and I thought we had a lot of geeks - RFLOL. I didn’t mean to start a “holey” war. 

I’m going to have to spend some time studying your replies and then just take a SWAG. I’ll post my progress here and results here. 

[Carl10]

Prov,

No war starting, but DC topics usually have a lot of opinions and subjectivity (not too much in this discussion).  Bottom line is what do you want from your DC?  To feel air moving through an opening and the ease to make that happen. Or to move the most air possible with the equipment you have.  There are countless numbers of people that saw a YouTube guy use undersized pipe on his DC and it picked up chips so they copied it and then went on to profess themselves as experts of using undersized pipe and how great it works! (all untested of course).  Do they move air? Will they pick up chips? Is it cheap?  Of course.  Could it be better, absolutely.  The funniest was when someone asked for help on a system that he was going to use corrugated drain pipe, because he had it.  It too would work, until it clogs.  So there are pros and cons to whatever you connect.  Usually cheap and easy has a performance impact.....