Dust Collection Duct Layout Advice Needed

Allrightnow

Blair
User
The layout looks good. I can't tell their height, but make sure blast gates are positioned where people can easily reach and will use them.

With a 9.5' ceiling, one option is to raise the floor 10" - 12" - screw ply, Advantech, etc. down to pillars and beams, then run the duct (and electrical for TSbelow the floor. That almost eliminates vertical drops except one up to the cyclone.

Unless you have really bad ducting with leaks everywhere, there is absolutely no need to add blast gates to close off trunks or drops. You just need them at each machine. With the machine blast gates closed, no air flows through the drop or trunk therefore there is no turbulence generated and no static pressure issue. Bill Pentz incorrectly left the recommendation to put blast gates on trunks/mains on his website, but he is WRONG! Since you are using PVC DO NOT glue or solvent weld it together- friction fit only. Use a single screw to keep it from separating if needed on vertical fittings and joints. Then after everything is fully assembled seal the fittings and joints FROM THE OUTSIDE ONLY with a TINY bead of silicone (not latex or hybrid) caulk. Remember the system is under negative pressure so the caulk will be pulled tight. If you use silicone on the outside you can easily disassemble parts and easily rub the silicone off with a finger, when it is time to reconfigure your duct- you will reconfigure sooner or later.

PVC, as you said wouldn't generate enough spark potential to start a duct fire. It is not a conductor so will accumulate static just inches from any grounding wire or foil so that is of marginal effectiveness. Often, once the duct is seasoned it stops generating static. Also, with the humidity in AL it may not be a problem anyway. If it is, just wrap grounded foil, screen, mesh, etc. in the areas most likely to be touched.

Make sure your sound isolation closet is ventilated so the motor will not overheat and it won't block air flowing from the filters- the closet is part of the "DC system." Any resistance anywhere in the system will reduce the efficiency of the system. Any chance of putting the closet outside or in the storage room? That would be my preference.
My reply has absolutely nothing to do with the subject at hand. Alan, I see you live in Washington, NC. It’s a place with a long and pleasant memory for me. I spent many a summer with my grandparents there fifty or more years ago. My grandfather ran the production credit association office there. Thanks for replying and giving me an opportunity to remember.
 

Rushton

Rush
Senior User
Several people suggested moving the cyclone into the adjacent storage room space for sound reduction. We obtained permission to use that space and I've done a couple alternate layout sketches. The concern we have in using this space is respecting the peace and quiet for two people with offices that open onto the hallway outside this room. Their offices are about 3 yards away from the top left corner of the room as oriented in the drawing.

This is the reason for layout #2 - it moves the cyclone another 6' away from their offices. Since sound attenuates at the square of distance, we're wondering if this addition 6' of distance will give enough further sound reduction to our office dwellers to be worth losing the more complete coverage of the shop's floor space.

Either location will be supplemented by some serious sound insulation to the walls surrounding the cyclone.

Note that I have not taken time to draw in the drops; just trying to see how the main trunks could run. As before, the green duct is 8" and the blue duct is 6".

Location Option #1 - The doorway shown in the wall at the top of the drawing will be blocked off. The closet in which the cyclone is located has a door leading to the hall to the left.

1613411096452.png


Location Option #2 - we trade off the flexibility of more complete coverage of the shop floor space to move the cyclone further way from the offices. The doorway shown in the wall at the top of the drawing will be blocked off. A full sound insulating closet would be build around the cyclone in this location and the walls for the current closet would be removed.

1613411456683.png
 

NOTW

Notw
Senior User
In your original layout I would consider having the hard line for the table saw and bandsaw stop higher in the air and run the rest as flexible hose, this way if you ever wanted to run anything wider through the table saw you could move the dust hose to the side which is a lot easier than trying to move PVC pipe. I doubt you would notice any reduction in suction switching from a few feet of PVC to a few feet of flex.
 

Rushton

Rush
Senior User
Thank you, Notw. While my goal is to keep flex connections under 4', this is a good consideration.
 

tri4sale

Daniel
Corporate Member
You might check your building code and insurance
Agreed, since you are in a retirement community with a shared space, you might fall into commercial use not home/residential use, so a quick call into local permitting department might save you a lot of headache later.
 

tvrgeek

tvrgeek
User
No
In your original layout I would consider having the hard line for the table saw and bandsaw stop higher in the air and run the rest as flexible hose, this way if you ever wanted to run anything wider through the table saw you could move the dust hose to the side which is a lot easier than trying to move PVC pipe. I doubt you would notice any reduction in suction switching from a few feet of PVC to a few feet of flex.
Not what Bill Pentz says, but you only know for sure if you test.
 

Alan in Little Washington

Alan Schaffter
Corporate Member
If I were to guess, I'd say it was the higher SP (resistance or pressure drop) per foot of flex vs smooth wall duct. It is fairly significant- 3 times (According to Bill, "Even good smooth walled flex will increase resistance three or more times over straight duct.") but you guys can check for yourselves. I found it in two places on Bill's site- the quote above in the ducting section (3. Flex Hose & Hose Clamps ) and also on one of Bill's spreadsheets, but couldn't find it elsewhere in the text, but I didn't spend much time looking. I just discovered my name and a link to my autogate video unfortunately the link longer works and I didn't make into the acknowledgements page. :(
 

NOTW

Notw
Senior User
I will admit I did not read all of Bill Pentz's website, but I do know in my last shop I stopped the dust collection about 7' from the ground and ran flex the rest of the way down to my table saw and did not have a noticeable difference in suction. That being said I did no science to check and see the difference between suction at the end of the PVC and then again at the end of the flex, there could have been suction loss, but the dust collector was still collecting the dust so it didn't bother me.
 

NOTW

Notw
Senior User
Also, if the links to your setup no longer work Alan that is a shame your autogate setup is nothing less of awesome.
 

Alan in Little Washington

Alan Schaffter
Corporate Member
Also, if the links to your setup no longer work Alan that is a shame your autogate setup is nothing less of awesome.
The video used to be on the American Woodworker Magazine website. When they closed up shop/were sold, most of the media was moved to F+W but not my video. I'm not sure who, if anyone, owns any of that stuff now. (I haven't checked the WayBack machine). Also, unfortunately, somewhere along the way I deleted my master or lost it when I transferred files to a new computer. With all the time on my hands, maybe I should re-shoot it. The video of my adjustable height assembly table is gone as well (the two part AWW article can still be found). I could re-shoot that one too and add my similarly designed adjustable height woodworking bench to it.
 

Hmerkle

Hank
Corporate Member
The video used to be on the American Woodworker Magazine website. When they closed up shop/were sold, most of the media was moved to F+W but not my video. I'm not sure who, if anyone, owns any of that stuff now. (I haven't checked the WayBack machine). Also, unfortunately, somewhere along the way I deleted my master or lost it when I transferred files to a new computer. With all the time on my hands, maybe I should re-shoot it. The video of my adjustable height assembly table is gone as well (the two part AWW article can still be found). I could re-shoot that one too and add my similarly designed adjustable height woodworking bench to it.
Alan, that would be great and if were willing, we could post it on the "Learn" section of the NCWW.com site!
 

Pop Golden

Pop
Corporate Member
In my humble opinion floor sweeps are dangers. It's way too easy to sweep a screw or bolt off the floor into your DC. Metal and DCs don't mix very well. Seems like a recipe for a shop fire.

Pop :eek:
 

Alan in Little Washington

Alan Schaffter
Corporate Member
In nearly 20 years of use I've sucked up everything from chunks of wood, nuts, bolts, metal parts and debris, etc., etc. even a tape measure, but never had a problem, ever, except the one time something metal pierced the side of the cyclone. My current DC cyclone (and its predecessor) was plumbed in the push-through configuration (remember all single stage DC's are set up that way!) That means dusts hits the blower which doesn't have screen on the intake and the impeller first. The cyclone which doesn't have a screen either, comes after the blower. Anything sucked up goes though the fan and impeller before being blown into the cyclone. The blower has a heavy duty steel impeller so is unlikely to be damaged. The velocity of the air and low density of dust in the air stream rapidly cool and extinguish any sparks that might be generated and prevent ignition.

My shop is above the garage. 6" ASTM D2729 PVC ducting runs along the garage ceiling. Relatively short drops run up to the tools. The main duct passes through the wall at the right and into the motor/blower unit located in an adjoining utility room.





The motor/blower (a very old Grizz with 3 hp motor with a 14" impeller) is mounted on stilts which are lag bolted into the studs, but the weight is carried by the legs. With the help of an eyebolt screwed into the wall and some rope I can single-handedly raise and lower the blower (once the cyclone has been removed at the flange.) I've had to do that once to replace the motor bearings. I have changed the start capacitor and start switch contacts twice but can reach them using a ladder. The cyclone has a 3D cone- it length is 3 times the diameter of the cylinder- a version of Bill Pentz's (1.64) design.





The cyclone exhausts air straight up to a shop level plenum containing two 300 sq. ft Farr-style cartridge filters (from Wynn Environmental?) connected in parallel.



An old piece of inner tube and two band clamps make great, inexpensive, low noise couplings- much cheaper than a Fernco!





Since it is a push-through configuration and under pressure, I don't need a fancy dust bin or barrel and air tight lid attached to the cone. The dust collects in a standard Food Lion 39 gal. leaf and lawn trash bag connected to the bottom of the cone with a band clamp. It is extremely easy and very neat to disconnect, tie off, and carry bags to the curb! My high dust alarm had not been installed yet in the first photo. (The pink Bondo was an experiment to see if I wanted to paint it fancy- it still looks like that today! ;)



Early high dust alarm which uses a day/night lamppost sensor and a simple bulb. It worked just fine but was replaced by a purpose-built IRLED version. I've got it wired to the DC control circuit so the DC shuts down if a high dust situation occurs. Since the sensor switch closes in darkness (absence of light), it is failsafe and there is no problem if the bulb burns out- the DC just shuts down.



 
Last edited:

Rushton

Rush
Senior User
Hi Charlie, thanks for your encouragement! Our planer is a DeWalt Model 735 13" planer mounted on a moveable flip top cart. You can see the cart, with its top flipped and the planer underneath, to the side of the bandsaw and in the general outfeed area of the table saw. There is a barely readable legend on it that says "Outfeed table, flip for Planer". We have a Byrd Shelix helical cutterhead ordered to replace the stock straight blade cutterhead.

My next efforts on this layout will be figuring out duct connections and shrouds to the machines. We are planning to install blast gates on the 6" drops nearest each machine. We will be using the Clear Vue Cyclone 6" blast gates (self-cleaning, and high flow-through because the D-2726 pipe fits inside the port so as not to reduce the full inside diameter of the pipe).
 
Last edited:

Rushton

Rush
Senior User
Making 90-degree turns when we just can't avoid them...

Continuing the layout design planning for this new dust collection system, I've been trying to sort out whether to use standard sweep 90-degree elbows or paired 45-degree elbows with this D-2726/SDR35 piping. I'd love to have available to me long sweep 90s (curvature of two-times-the-radius, 2R, or greater), but its simply not available in this standard of pipe.

I think I have finally received some engineering data that supports using a standard sweep 90-degree elbow with our D-2729 and SDR36 6" ducts instead of using paired 45-degree elbows.

In a thread I've been pursuing on the Australian Woodworker forum, beginning with post #24, U.S. member Dmorse discusses the engineering data involved. Our problem boils down to the curvature of the radius available to us in D-2729/SDR35 elbows. They are all less than 1R.

According to Dmorse's post, the sweep 90-degree elbow most commonly available in D-2729/SDR35 pipe is .833R, but the 45-degree elbows are only .5R. The 90s at this radius sweep have a loss coefficient of about .28. But the 45s with their .5R radius have a loss coefficient of about .71/2 each (one-half the loss coefficient of a sharp bend 90). When used in pairs, the total loss coefficient is the full .71 or greater. Much higher than the .28 of the standard sweep 90.

So, his conclusion is that, of the commercially available choices available to us for D-2729/SDR35 ducts, we're better off using the standard sweep 90s than 45s in pairs. (Contrary to everything I've understood over the years, but the data certainly supports it!)

Sweep 90 - Ninety_75rD_2.jpg


Standard 45 elbow.jpg


If anyone has some testing or engineering information supporting why we should be using paired 45s, I'd appreciate hearing about it.
 

Our Sponsors

LATEST FOR SALE LISTINGS

Top