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Forum topic by sandhill posted 08-29-2011 07:34 AM 1728 views 0 times favorited 31 replies Add to Favorites Watch
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sandhill

2128 posts in 3391 days


08-29-2011 07:34 AM

Topic tags/keywords: question

When I move into my new shop I want to run a vacuum line from the dust collector to each machine station. The DC unit is a 3 HP Jet Duel bag collector. Would it be a bad idea to run 6” main lines and 4” drops to the machine or should I go with 4” all the way through? I am not sure if 3 HP is powerful enough to use 6” runs. I got the unit used so I do not have any paperwork on it I think it may be 1900 CFM but I am not sure and can’t seem to find anything on the net for this unit.


31 replies so far

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Grandpa

3256 posts in 2142 days


#1 posted 08-29-2011 08:25 PM

I am not sure either. There is an article in the Oct. issue of WOOD magazine that deals with dust collecting. This author is pushing the larger trunk lines. I do know that larger pipes have less friction and less friction is the name of the game. I agree with him when he says to remove the “Y” at the collector to use a larger pipe. If the inlet is 6 inch then us a 6 inch “Y” or 8” use an 8” “Y”. If you leave the restricter at the collector then you might as well use that size pipe all the way out and handicap you collector by restricting it. We probably should use all we can on any machine. This would be like buying a 10” table saw and using a 7” blade on it. Sure it will work but how well does it really work.

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Manitario

2402 posts in 2350 days


#2 posted 08-29-2011 08:40 PM

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

-- Sometimes the creative process requires foul language. -- Charles Neil

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helluvawreck

23207 posts in 2334 days


#3 posted 08-29-2011 09:40 PM

I don’t know how many machines you have but your horsepower may not be enough to get them all. In a non scientific way your system will work pretty well if the cross sectional area of your blower inlet is equal to the total cross sectional areas of all the individual outlets at each machine. The idea is to keep the air flowing throughout the pipe at the same speed (4000 fpm maybe). Your elbows should be large radius material handling elbows (not a tight 90 degree). The air and dust will have less friction. When you have a pipe coming into another pipe it should never come in at 90 degrees. It should come in at an angle of 30 to 45 degrees (30 is better – less friction). When you have a pipe coming into another pipe you are suppose to increase the diameter of the pipe going to the blower. They make fittings called lateral tees for these branch pipe. They take care of the entry angle and increase the size of the pipe at the same time. If you need to branch off of a pipe and go 90 degrees then you do it with a lateral tee. If your branch angle is 30 degrees then you simply put a 60 degree elbow on the branch pipe so that you are going out at 90 degrees. Some people like to put blast gates on so that they can adjust the flow. I don’t like to do this. I believe it should be designed where the whole system is balanced. However, if your blower is just not big enough you could put on a couple of main branches going into a y fitting (these are called by many a pair of pants). Each of these would have a blast gate and you would use only one branch at a time by cutting off the other branch.

I use to know how to design them the way you are suppose to. The first project after engineering school that I had was to design a dust system for a 5000 sq ft shop with about 12 or so full sized machines. We now have a 180,000 sq ft plant and we use the non scientific way and a little common sense now. They usually work fine. Sometimes you just have to break the rules and fudge a little here and there. Our two main systems are 75HP each and then we have 3 or 4 others around 20-30 HP. Do a little reading about it – you don’t have to be an engineer to do it for a small shop. Just use the cross sectional area method and the different correct fittings and follow the basic rules. You can usually find out how many CFM your blower will move and you can find the recommended pipe sizes for different kinds of machines on the internet.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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Cosmicsniper

2202 posts in 2626 days


#4 posted 08-29-2011 09:55 PM

4” lines are perhaps 50% of the efficiency of 6” lines. The directive by Pentz is to keep your lines as frictionless as possible, as large as possible. The amount of horsepower determines if it is possible to have enough velocity AT THE MACHINE to capture the fine dust. At 3hp, you should have plenty enough power to run 6” for the entire system as long as your ducting is well laid out and the runs aren’t ridiculously long.

Pentz highlights all of this at his site, but I think if you have a typical garage-sized shop, 6” runs will be fine. Most people will run a 6” main with 5” or 4” drops to each machine. Unless you reformat your machines for 6” ducts, you’ll have to transition as some point. The idea is to stay 6” as long as possible.

-- jay, www.allaboutastro.com

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Fred Hargis

3950 posts in 1960 days


#5 posted 08-29-2011 09:57 PM

I would run 6” all the way to every machine I could convert to 6”. I think a 3 HP DC will pull a goodly amount of air, and do try to keep the elbows gentle (I used 2-45° el’s with a short piece of straight pipe between them). Putting 6” on the smallest DC’s is problematic, since they don’t move enough air to keep the debris suspended in the air stream. You should have no such problem. Here’s how dedicated I am to the large pipe all the way to the machine, on my drum sander I could not figure out a way to enlarge the factory 4” port. I replaced the whole top with a shop built cover, not pretty but very effective.

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

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sandhill

2128 posts in 3391 days


#6 posted 08-29-2011 10:41 PM

This is real good information everyone, this is why I belong to LJ’s. “Good people giving a hand” Thanks everyone.
The shop is 25’ X 50’ and the DC unit will be on the back wall so what I am hearing is run 6” to every machine and install blast gates to balance the system, am I on target with that assessment?

The DC unit has 3ea. 4” ports so it looks like I will have to make modifications. All my machines are 4” dust ports except for the planer which is capable of 6” if I remove the 6” to double 4” -Y- . I need 7 to 8 ports total, 1 at the planer, 2 on the band saw, 1 on the Joiner, 1 on the Table saw (for now) and 1, 4” + 1, 2” at the router table.

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helluvawreck

23207 posts in 2334 days


#7 posted 08-29-2011 10:55 PM

With all due respect to you and the others, sanhill, if you have a 25ft by 50ft and are serious about setting up a central dust system you should try to do it the right way. A 25’ x 50’ shop is a fairly large shop. What some of the others are saying breaks most every rule that I’ve ever been taught and I’ve been in woodworking plants for 40 years and have built probably 20 or 30 complete systems and have made countless modifications to our own systems during that time. I don’t care to get into an argument but I just say this because I would hate for you not to have a nice system if it’s in reach.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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Cosmicsniper

2202 posts in 2626 days


#8 posted 08-29-2011 11:47 PM

Debates are fruitful; arguments are not.

If you believe in Pentz’s research, then you’ll have to concur that dust collection meeting OSHA standards is not possible in typical systems without going to at least 6” pipe. From there, using lesser sized ducts poses a health risk, at least in some part. The degree to which we want to suffer depends on the size of our machines’ DC ports, our ability to run large and efficient pipe, and the DC’s ability to move large enough amounts of air at that piping size. For the record, Pentz’s states that you need around 4000 fpm AND around 800 cfm at the machine in order truly wipe out dust concerns.

Using my own 2hp DC with very short, efficient 4” PVC throughout, it was immediately obvious (to me anyway), that I was doing a good job of catching the chips, but not the actual dust. Makes sense, because i’ve pretty much throttled down my throughput to maybe 500 CFMs because of the 4” pipe. I will be upgrading to 6” as much as possible very soon…which is no big deal in my small shop.

The point is that you have to combine both velocity and throughput to give the best collection yield. Velocity alone does not suffice.

From the link Rob posted above, Pentz’s summarizes:

”Ducting resistance is known as static pressure. Even a short run of duct that is too small for a blower will cut the airflow down to the highest speed that pipe can sustain. The impact on most hobbyist blowers is terrible. A 3/4 HP blower with a maximum airflow of about 600 CFM will rarely provide more than about 300 CFM real air flow when connected to a 4” pipe. On that same 4” ducting a 1 HP unit that gives 650 CFM maximum rarely will maintain 350 CFM. A 1.5 HP rated at 1100 CFM barely gives 450 CFM. And a 2 HP capable of 1200 CFM is lucky to provide 500 CFM. Bumping up to 5” pipe adds about 100 CFM to each of these configurations. Bumping up to 6” pipe causes problems for the under 1.5 HP units because the air speed (FPM) can fall too far and make dust block the pipes, but with this bigger pipe, the bigger units end up going to 800 and 900 CFM. As a result, you need to use at least 5” duct for any hobbyist blower rated up to 1100 CFM and 6” or larger duct for blowers rated 1100 CFM to 1800 CFM.”

Regardless of how you feel about Pentz’s research, there is one thing I certainly agree with. We spend too much time thinking about filter sizes and Thein baffles without fully realizing that most of the deadly dust never actually reaches the DC.

-- jay, www.allaboutastro.com

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sandhill

2128 posts in 3391 days


#9 posted 08-29-2011 11:58 PM

I wish I could have someone come in and install an Oneida system but funds are not that much I still have to buy a fork lift, and 50K for inventory to start, add that to one years rent and utilities and we are up to 75K counting equipment that I will put into the business. I must use what I have. Maybe if the store side does well enough I can expand to add the other two parts of the building which would give me 4000 SF then I will have someone come out and design a system. I just need to make what I have work now.

cr1 Its a 3HP Jet I have no paperwork, I got it for $100.00 on Craigs list.

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helluvawreck

23207 posts in 2334 days


#10 posted 08-30-2011 01:36 AM

I work on our machinery, I’m in charge of the maintenace an engineering in our plant. We have 37 inch wide belt sanders, gang rip saws , molding sanders, chop saws, and finger jointing systems and 5 wienig molders, etc. The suction in our machinery is so strong that on a number of occasions I have had the hat pulled off my head if I get within ten inches of the ducts if I’m not thinking. I always wear a work hat so I know immediately if I want to retreive my hat there is nothing to do but go out to the central collection location and find it before it gets covered up. It is a couple of hundred feet away from the nearist molder. Anyways, I’ve enjoyed talking to you guys and God bless you in all of your woodworking and may you always be profitable and happy in your work. We started with nothing. In a 25’ x 50 ft shop you can build your own dust system.

If we don’t get the dust and shavings out of the way we grind to a halt.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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sandhill

2128 posts in 3391 days


#11 posted 08-30-2011 01:50 AM

I sent JET an email with the SN# and asked if they could locate a Manuel maybe I will luck out. I also have a Delta 1100 CFM 3/4 HP I am getting rid of as soon as I get this one hooked up and working.

By the way the JET unit has an 8” port with 3 4” ports coming off it. I think I said it was a 6” port earlier but I was mistaken.

I guess I will run an 8” main trunk and drop to 6” at the machines. Does that sound like it will work? I have about a 25’ run to the last machine. I know that seems a bit long but do you think it will do the job as long as I use blast gates for each machine?

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crank49

3981 posts in 2438 days


#12 posted 08-30-2011 02:11 AM

Your collector, if it has three 4” pipes, will handle a 7” pipe and be balanced. The cross sectional area of three 4” pipes is almost the same as one 7”. A quick way to see what is balanced is to square the diameter. So, 7×7 = 49. 4×4 = 16 each and 3 pipes x 16 = 48. 48 is very close to 49 so this is balanced.

If you have multiple drops from a 6” or a 7” and the drops are the same size as the trunk line, you will have to shut off all but one of the drops at any one time.

Your system could handle three 4” drops all open at the same time, BUT the trunk is supposed to be reduced in diameter each time you connect an open drop. This gets to be complicated to explain.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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helluvawreck

23207 posts in 2334 days


#13 posted 08-30-2011 02:39 AM

Look, I want to apologize fellows. I’m not trying to be some kind of big shot know it all. I’m actually quite a humble person. I usually don’t post on anything like this unless I think I might can be helpful. All I wanted to do is offer some help. If I have stepped out of line in some way then all of you have my utmost apology. I will try to do better in the future.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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sandhill

2128 posts in 3391 days


#14 posted 08-30-2011 03:19 AM

helluvawreck Look think nothing of it I was not offended and I welcome and value your opinion so keep on posting. It’s hard to write what you want to say the way you want it to sound, that’s the only trouble with the written word LOL.
I found some information about my DC. Air Flow is 1900 CFM with a 10.2 Static pressure which I suspect is somewhat less being its age 1993 I think???

What crank49 said makes the most sense to me, or at least the way he explained it and my guess is its about the same as everyone else in theory.

I guess I will have to wing it and try different configurations.

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Sawkerf

1730 posts in 2536 days


#15 posted 08-30-2011 03:38 AM

Early this year, I reworked the piping to my Jet 1100cfm DC. I removed the plastic 6” x 4” x 4” “Y”, and went to 6” trunks with 4” drops to the tools. I modified my TS to use a rectangular heat vent feeding into a 6” duct. All the duct work is 6” HVAC duct. The increase if effeciency was very significant.

The September issue of Wood magazine has a nice article about DC that explains a lot without getting into a lot of theory and calculation. They recommend going to 6” if your DC will take it.

-- Adversity doesn't build character...................it reveals it.

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