Dust collector pipe/fittings - Woodworking Talk - Woodworkers Forum
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post #1 of 8 Old 04-17-2020, 05:02 PM Thread Starter
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Dust collector pipe/fittings

I'm setting up a dust blower for my sawmill that will eventually be ducted to jointer, planer etc.
I've got a 5hp blower rated at 4,900 cfm that screams like crazy so I want it as far from the mill as possible.
Like this: https://www.woodmastertools.com/shop...ust-collector/
It has a 6" inlet that fits metal furnace duct but I'm not sure if that's stiff enough to hold that much vacuum.

The 6" will be a 40-50 ft run from the blower to the flex hose running to the mill. The mill has a 4" port so there will be about 15' of 4" flex hose. (suppose I could upsize the flex hose and use an adapter on the mill)

Not sure if this is going to be a disaster.....possibly crushing the metal duct and too much restriction in the flex hose.
Too costly to put in an Oneida system.
Could use PVC but adapter fittings seem to be hard to find.
Any suggestions?
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post #2 of 8 Old 04-17-2020, 07:38 PM
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Funnace duct is meant for low "pressure", not ......

Furnace duct is not meant for that kind of suction. Probably a drain culvert would be OK for that sucker ......
I think if it were me, I'd be using schedule 40 6" PVC at a minimum. This is a one time expense, so don't go cheap now and regret it shortly afterwards.
https://www.pvcfittingsonline.com/re...hedule-80-pvc/

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #3 of 8 Old 04-18-2020, 05:25 AM
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Contractor HVAC supply stores have heavier gauge galvanized duct.
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post #4 of 8 Old 04-18-2020, 06:34 AM
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That DC has a 13" fan, so about 12"w.g. maximum vacuum. 30Ga HVAC snaplock duct will collapse. 26Ga will be OK, but is a little harder to find. Spiral pipe is good but more money. PVC Sewer & Drain (ASTM 2729 or ASTM 3034) will also work, no need for pressure pipe like Sch40 or even DWV.

The CFM claimed for that DC is wishful thinking. A 13" fan and 6" inlet and outlet will be more like 1600CFM, not 4944.

You'll get much better performance with 6" hose instead of 4", very roughly 780CFM vs 450CFM. That estimate doesn't include any bends, excess entrance loss, or the outlet ducting and bags, just the ducting you listed. Actual numbers will be less, those are stated only for relative comparison between the two hose sizes.
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post #5 of 8 Old 04-18-2020, 12:42 PM Thread Starter
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Quote:
Originally Posted by HoytC View Post
That DC has a 13" fan, so about 12"w.g. maximum vacuum. 30Ga HVAC snaplock duct will collapse. 26Ga will be OK, but is a little harder to find. Spiral pipe is good but more money. PVC Sewer & Drain (ASTM 2729 or ASTM 3034) will also work, no need for pressure pipe like Sch40 or even DWV.

The CFM claimed for that DC is wishful thinking. A 13" fan and 6" inlet and outlet will be more like 1600CFM, not 4944.

You'll get much better performance with 6" hose instead of 4", very roughly 780CFM vs 450CFM. That estimate doesn't include any bends, excess entrance loss, or the outlet ducting and bags, just the ducting you listed. Actual numbers will be less, those are stated only for relative comparison between the two hose sizes.
I'm leaning toward pvc right now but will have to run a ground wire (inside the pipe?)
Finding connection fittings seems to be an issue. I did find this one to go from 6" OD on the blower to outside of 6" SCH 40 PVC (about 6 5/8")
https://www.lowes.com/pd/Fernco-6-in...ing/1000075385

I aggree that the 4" flex hose will be restrictive. 5" might be a better compromise and that would give me a looser fit on the mill to allow for some pivoting so the hose won't twist. Full travel on the mill carriage is about 21' so I'll probably have a loop of hose suspendend from above to keep it from draggin on the ground.
I saw one setup where they had a pulley running on cable under the roof trusses and hung the flex hose from a rope off the pulley. Allowed for free movement over the mill travel.

Not sure how to connect the flex hose yet. Need to find something like this to go from 6" pvc to 5" flex hose.
https://www.rockler.com/rockler-sche...apter-for-hose

Any recommendations on type & source for good durable 5" suction hose?

Last edited by Shop guy; 04-18-2020 at 12:52 PM.
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post #6 of 8 Old 04-18-2020, 03:29 PM
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Is this a commercial operation? If so, fire codes will likely restrict you to metal duct. A grounded wire inside PVC pipe won't do it. In a hobby environment it can surppress nuisance static charge effects but won't meet code.

If you must use Sch40 instead of thin wall sewer pipe note that the ID is more than 6" so it should actually fit over the inlet.

5" hose is a good choice. Using that in the previous simulation I get 720CFM so, yes, close enough to 6".

There are several online sources for hose. One place to start with is mcmaster.com.

But, again, if you are commercial, talk to a local HVAC duct supplier. They should have some experience here and be able to fabricate any adapters that are needed.

-----Dave
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post #7 of 8 Old 04-19-2020, 10:24 AM Thread Starter
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I'm not really a commercial operation. I'm on a farm and it's a one-man operation so most code requiements don't apply. That said my insurance man might have other ideas about it. If I run ground wires through the inside of the pvc and make sure my electrical service it up to code I don't think there are any issues.

I ran across some really nice flex hose, some of which has a ground wire molded in, but it's way expensive.
https://wholesalehoses.com/store/hos...y/Lumber-Mill/
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post #8 of 8 Old 04-19-2020, 12:10 PM
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If you are trying to reduce nuisance shocks then a wire spiraled around the outside of the pipe will work about as well as one inside. It does not need to be bare but absolutely must be grounded. The disadvantages of the inside wire are possible clogs and the constant sparking it causes inside the pipe if it's bare. Note that there is no way to prevent buildup of charge on an insulating duct. You can only shield it.

Try here for hose. It's not as rugged you might want but it won't be very expensive to replace either. Given the leadtime for the 25' lengths you might want to keep a spare around if you can't afford downtime. You will need to ground the spring wire in the hose.

Edit to add:

I just noticed that Wynn also has antistatic hose at a good price.

-----Dave

Last edited by HoytC; 04-19-2020 at 12:33 PM.
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