LumberJocks

Advice needed on Dust collector ducting

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by Jagerheister posted 06-03-2020 12:56 AM 374 views 0 times favorited 18 replies Add to Favorites Watch
View Jagerheister's profile

Jagerheister

64 posts in 1900 days


06-03-2020 12:56 AM

Topic tags/keywords: bandsaw planer drill press miter saw spray gun jointer plane sander tablesaw

I just picked up this dust collector. It has an 8” inlet port. It has a 3HP motor, and according to the guy I got it from, a 12” impeller. From what I read, it produces 1650 CFM. Im connecting the following machines:
Table saw
Bandsaw
8” belt sander
Mitre saw
12” jointer
12” planer
and maybe a couple 2.5” ports

Im trying to use 8” ducting as a manifold, then neck down to 4-6” ducts as they split off in a “y”. It’s noteworthy that I probably won’t be using more than a single machine at once…

I’m having a tough time finding an 8” duct at any stores near me. 8” PVC doesn’t exist At HD or Lowes by me. I do think they have 30 gauge 8” galvanized HVAC duct, but I’m concerned that it will collapse under vacuum pressure. I’ve seen some of the spiral steel ducts, but they are pretty spendy.

So my first question; how much loss do you think I would get if I just used an 8 to 6” reducer at the inlet, and just run 6” PVC instead of 8”. Has anyone ran 6” or 8” ducting with a machine of this size? Will the difference be noticeable in terms of performance, or more importantly, will I regret not shelling out another $500-$800 on 8” spiral ducting.

Second question;Is this concern about 8” 30 gauge galvanized duct crushing under vacuum? I read that somewhere, but maybe someone has tried it and it was fine.

Final question; Are there any options that I am not mentioning here?

Any help will be appreciated. Thanks in advance.

PS. I already know about the PVC explosion debate.. No need to beat that horse… lol


18 replies so far

View Holbs's profile

Holbs

2346 posts in 2806 days


#1 posted 06-03-2020 04:04 AM

8” port on a 3HP 1650 CFM dust collector? Hmm….something fishy is going on here. Does the inlet port look home made?

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter "xylokopos/ξυλοκὀπος"

View Axis39's profile

Axis39

239 posts in 374 days


#2 posted 06-03-2020 05:15 AM

Not being any expert on Dust Collector specs, 1650 sounds a little low to me as well, although, that is across 8”? I smart enough for those kinda numbers.

Anyway, google ‘Plumbing Supply’ see if there’s someplace nearby that sells Schedule 20 Drain Sewer Waste pipe and fittings.

I do know you want the biggest pipe for as long as you can within the system. IOW, Neck down as late as possible.

-- John F. SoCal transplant, chewer uppper of good wood

View CaptainKlutz's profile

CaptainKlutz

3197 posts in 2271 days


#3 posted 06-03-2020 05:51 AM

Grizzly and others ship 3HP dust collectors with 7-8 in inlet ports. So port size is proper.

The question to use full 8 in trunk or less boils down to simple question IMHO:

Will you be using a large wide belt sander?

Many large wide belt sanders often use (2) 6in or (3) 4in outlets (or more) and specify 3HP minimum dust collector.

If Yes, then you want/need a 8in trunk line.
If No, then using a 6in is fine. Especially in a one man shop with only one tool used a time.

The same debate can be made if any tool would have (2) 5in ports.
Then you might want to keep the trunk size to 7in min, instead dropping all the way 6 in.

As far as duct wall thickness; you want at least 26ga, preferably 24 ga steel for metal ducts.

Be sure to check you local area for sheet metal fabricators that sell HVAC duct work. They will usually have what is needed in stock, or can make it in a couple days. Steel metal ducting is large and expensive to ship. Local prices tend to be better, but you might have to shop around to find a competitively priced shop.

If you need some more tips, try this WWW post:
https://www.wwgoa.com/article/simple-approach-for-dust-collection-ducting/

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View Fred Hargis's profile

Fred Hargis

6249 posts in 3270 days


#4 posted 06-03-2020 10:23 AM

You can extend the 8” several feet with galvanized snap lock, then neck that down to 6” PVC…it will work. I did the same with my Oneida which had a 7” inlet when i ran 6” PVC ducting. Not pretty, but I’m very much function over form. Oneida advised that the first few feet from the collector be the 7” size to allow the air stream to smooth out before entering the cyclone. But I would stick to the 6” for the rest of the system.

-- Our village hasn't lost it's idiot, he was elected to congress.

View clagwell's profile (online now)

clagwell

250 posts in 570 days


#5 posted 06-03-2020 10:50 AM

Six inch will be fine unless you have an extremely long main run or lots of twists and turns. 8” 30ga will collapse. Your limitations will almost certainly be the machine ports, not the main duct.

The 12” fan is what’s really going to determine performance. The 1650CFM is probably for the blower alone, no cyclone or filter. Once you get a machine port connected you’ll be limited to about 400-600CFM for 4” ports and 600-800 or so for 6” ports.

So, an example. Let’s say you have a really low loss connection to a big hood around your miter saw and, with a 8” main are getting 800 CFM. Now, let’s say that main is 20’ long. If you change that to 6” the 800CFM will decrease to about 780CFM. For smaller ports with lower flow rates the change will be much less. For example, a 400CFM flow would drop to 397CFM. It would be an unmeasurable change at a 2.5” port.

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View OldBull's profile

OldBull

113 posts in 73 days


#6 posted 06-03-2020 11:52 AM

I can not give advice on what you need to buy, but after just going through this with different sizes I can offer 3 pieces of advice.

1. Make sure to identify what connects the pieces together, in my system, pipe will not fit into pipe, pipe will not fit into gates, only hose will connect 2 things together. This may not be the case with your system but make sure of which piece can connect to the next one or it may get frustrating. Some items may look like rubber and appear they would stretch but most are hard plastic. So a 2.5” connector will not fit over my 2.5” table saw connection.

2. Buy only what you need. Make a plan and stick with it, don’t guess or you will end up with a box full of parts.

3. Go to each piece of equipment, measure and right down what size the dust collector connection size is, you may find 2.5” to 1.75 inch. Know that a 1.75” or 2.5” inch fitting may not fit the their respective connector. On mine only hose will fit in between.

-- Relative bearing grease # CV-61 and CV-66

View controlfreak's profile

controlfreak

776 posts in 379 days


#7 posted 06-03-2020 12:49 PM

If you are worried about collapse especially if you accidentally close all ports you can install an emergency inlet near the motor with a spring tensioned flap that can stay shut with one or more ports open.

View ibewjon's profile

ibewjon

1653 posts in 3570 days


#8 posted 06-03-2020 01:12 PM

I would definitely not use the 30 ga. The larger the duct size, the heavier guage needed for suction lines. I use 5” 26ga on my 2hp, so 6” should work great, it is about 50% larger than 5”. The straight length ahead of the cyclone is definitely a big help for separation.

View clagwell's profile (online now)

clagwell

250 posts in 570 days


#9 posted 06-03-2020 01:22 PM


The straight length ahead of the cyclone is definitely a big help for separation.

- ibewjon

Did you test that? Or have a link to some actual test data? I’ve always wondered how much difference that made with wood dust. Do you have numbers you can show? That would be really helpful.

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View Redoak49's profile

Redoak49

4748 posts in 2766 days


#10 posted 06-03-2020 01:28 PM



Not being any expert on Dust Collector specs, 1650 sounds a little low to me as well, although, that is across 8”? the

- Axis39

Actually, 3 hp with only a 12” impeller the 1 650 is high. I barely get that with a 5 hp and 15” impeller .

I would put a cartridge filter on it as with the bag you are putting out fine dust.

View ibewjon's profile

ibewjon

1653 posts in 3570 days


#11 posted 06-03-2020 01:49 PM

I do not have a cyclone yet, so I have not tested it. But if Oneida suggested it, I believe it. It is their reputation, so I am sure it is well tested. And with any sensors or smoke detectors installed in HVAC systems, there is a requirement for straight pipe length of ( x) times the duct diameter for air stream stability. I forget what (x) is because I have not done any fire alarm work for several years. I never tested that either, some times you just have to believe!

View clagwell's profile (online now)

clagwell

250 posts in 570 days


#12 posted 06-03-2020 02:05 PM



I do not have a cyclone yet, so I have not tested it. But if Oneida suggested it, I believe it. It is their reputation, so I am sure it is well tested. And with any sensors or smoke detectors installed in HVAC systems, there is a requirement for straight pipe length of ( x) times the duct diameter for air stream stability. I forget what (x) is because I have not done any fire alarm work for several years. I never tested that either, some times you just have to believe!

- ibewjon

Yeah, I know. Like agent Mulder I want to believe too. :)

I guess the question is does it makes enough difference that you should compromise other perfoemance aspects of your system to get that? If it’s convenient, then sure, keep it straight. But if not, how much do you really give up?

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View Fred Hargis's profile

Fred Hargis

6249 posts in 3270 days


#13 posted 06-03-2020 04:18 PM


I guess the question is does it makes enough difference that you should compromise other perfoemance aspects of your system to get that? If it s convenient, then sure, keep it straight. But if not, how much do you really give up?

- clagwell

I didn’t test it without the 5’ of straight pipe, but I did test with it. My Oneida separated 98.4% of the total dust (by volume) and as I recall they spec’d 99%. This isn’t easy and the results I had can be easily challenged, besides I don’t know if Oneida’s numbers are by volume or weight. But everything that got past was the finest particles, and I thought that wasn’t good enough. I sold that DC. To test first cleaned my filter as best I could. This included blowing it out from the outside, then placing it on the floor and dropping each end form about 18”, rotate 1/4 turn..repeat. Then I took my shop vac and brush and ran it across the pleats from the inside. Re install the filter and run the DC in normal use until the 55 gallon was full. Then repeat the filter cleaning, but saving everything to measure. Also measure how much debris was in the can. Viola, you have your separation. I did this at Oneida’s request, BTW.

-- Our village hasn't lost it's idiot, he was elected to congress.

View clagwell's profile (online now)

clagwell

250 posts in 570 days


#14 posted 06-04-2020 09:55 AM



I didn t test it without the 5 of straight pipe, but I did test with it. My Oneida separated 98.4% of the total dust (by volume) and as I recall they spec d 99%. This isn t easy and the results I had can be easily challenged, besides I don t know if Oneida s numbers are by volume or weight. But everything that got past was the finest particles, and I thought that wasn t good enough. I sold that DC. To test first cleaned my filter as best I could. This included blowing it out from the outside, then placing it on the floor and dropping each end form about 18”, rotate 1/4 turn..repeat. Then I took my shop vac and brush and ran it across the pleats from the inside. Re install the filter and run the DC in normal use until the 55 gallon was full. Then repeat the filter cleaning, but saving everything to measure. Also measure how much debris was in the can. Viola, you have your separation. I did this at Oneida s request, BTW.

- Fred Hargis

Yes, that’s a tedious test and requires a lot of care. Kudos for going through that effort!

I’ve always wondered about a manufacturer quoting a single number for collection efficiency since it varies so much with particle size. The cumulative collection efficiency is highly dependent on the size distribution of the dust going in. And that size distribution depends on the operation that produces it, e.g., sanding versus planing. Collection efficiency also depends upon CFM through the cyclone ans well as material density, r.g., poplar versus oak.

All that considered, I think you did a great job and essentially confirmed Oneida’s number given all of the uncontrollable variables and difficulties of the test.


... But everything that got past was the finest particles, and I thought that wasn t good enough. I sold that DC…

I don’t understand that. Can you add some insight?

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View Fred Hargis's profile

Fred Hargis

6249 posts in 3270 days


#15 posted 06-04-2020 10:37 AM

I’ve went through this quite a few times of the past several years and pretty much have quit bringing it up. Anyway, even though only 1.6% of the material was getting to the filter, that was the finest of the particles…and the filter would quickly clog. It got so bad that I wound up putting a magnehelic on the system to monitor when I had to clean it out. Oneida offers the same type of setup (or they used to) and the dust bin clearly had some specs on when to clean the filter. But if I had a long DS session going I could actually see the readings change on the magnehelic. After about 6 years I had to replace the OEM filter because it got so clogged I couldn’t clean it enough for use. Right or wrong I blamed the design of the cyclone body for this, and decided to replace it with a CV. I had mentioned that I did that test for Oneida. That’s because I was working with Bill Witter (founder of Oneida) to solve my separation…..after I did that test and reported the results I never heard from them again. I realize that a lot of folks are quite happy with their Oneida…I’m just reporting what happened in my case.

-- Our village hasn't lost it's idiot, he was elected to congress.

showing 1 through 15 of 18 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com