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PostPosted: Fri Jun 19, 2015 11:16 pm 
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Well, I just got 4 tools' worth of 4" triple-wall PVC installed for dust collection, and discovered (belatedly) that I have several sections of 6" metal pipe stored out of sight (and out of mind, evidently). Does it even work to put such big pipe on a smaller DC? (1.5HP Jet Bulldog, similar to the Vortex sold now) If it's no great loss, I'll just put the metal pipes on Craig's List or take it to the Rotary fundraiser auction this month. Thoughts?


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PostPosted: Sat Jun 20, 2015 7:13 am 
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forestgirl wrote:
Well, I just got 4 tools' worth of 4" triple-wall PVC installed for dust collection, and discovered (belatedly) that I have several sections of 6" metal pipe stored out of sight (and out of mind, evidently). Does it even work to put such big pipe on a smaller DC? (1.5HP Jet Bulldog, similar to the Vortex sold now) If it's no great loss, I'll just put the metal pipes on Craig's List or take it to the Rotary fundraiser auction this month. Thoughts?


It would reduce velocity thru the pipe and could lead to chip/dust build up around bends or not have enough velocity to pull it up thru a vertical run.

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PostPosted: Sat Jun 20, 2015 1:03 pm 
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Hey Gene,

I'm going to have to disagree with you on the virtue of 6" pipe over 4". The critical parameter is not the velocity but the volume (and corresponding mass) of air. The amount of solid material that can be conveyed is dependent upon the ratio of ratio of solid mass to gaseous mass. A 6" pipe will have less parasitic drag (from surface to volume), and will convey more air, and thus more solids.

In fact, velocity can work against you. That is the mechanics behind a cyclonic separator, the air speed continues to exceed that of the solids until the solid drop out.

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PostPosted: Sat Jun 20, 2015 1:33 pm 
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tms wrote:
Hey Gene,

I'm going to have to disagree with you on the virtue of 6" pipe over 4". The critical parameter is not the velocity but the volume (and corresponding mass) of air. The amount of solid material that can be conveyed is dependent upon the ratio of ratio of solid mass to gaseous mass. A 6" pipe will have less parasitic drag (from surface to volume), and will convey more air, and thus more solids.

In fact, velocity can work against you. That is the mechanics behind a cyclonic separator, the air speed continues to exceed that of the solids until the solid drop out.

Cheers,
Tom


If the impeller intake were 6" I'd agree. However, I think her's has 2 4" intakes so that would be the determining restriction as to volume of air moved I believe. If she combines the 2 intakes into a single 6" pipe, then the volume would obviously be greater, and 6" pipe would be beneficial.

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PostPosted: Sat Jun 20, 2015 5:56 pm 
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My Grizzly 3hp cyclone has 2 7" intakes which I maintain on two runs under and over the shop. I drop to 4" at each machine as close to possible. The exception is a drop to the chop saw where the overhead 7" run is dropped to 4" for about 8' horizontal then 6' vertical down to the saw. This latter is the only one that seems to have a problem with anything of more mass than just sawdust, eg small chunks or larger chips. Usually when I disconnect the hose from the saw I'll find these neatly collected for the kindling bucket.

Of course, 3hp is not a fair comparison to a 1.5hp DC but I think Tom's assessment is spot on.

With the exception of the size of the input at the DC itself, of course.

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PostPosted: Sat Jun 20, 2015 6:42 pm 
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It dawned on me after I started the thread that, indeed, I have two 4" intakes -- a Y that fits over the large intake port in the metal DC housing. The way my shop's set up, it would be difficult to take advantage of that big port. I'll send the 6" pipe off to someone who can use it. Thanks for the info!


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PostPosted: Sat Jun 20, 2015 6:47 pm 
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Hey Jamie,

Since the volume increases by the square of the radius, you'll actually move more than twice the air with a 6" pipe over a 4" pipe. It really does make a difference. Don't take my word for it, check out the DC forums and manufacturer's websites.

Cheers,
Tom

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PostPosted: Sat Jun 20, 2015 9:24 pm 
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I'll save that for the next incarnation of a shop, for sure. Just too eager to get rolling to make a U-turn and redo the collection stuff. I was very excited to discover the triple-wall PVC, but it took quite a bit of time to figure out how to make it work with the various parts I had (blast gates, reducers, etc.) Just very happy to have mostly pipe instead of hose in my diminutive shop:

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