Need some advice on DC Plumbing

[DaveStL]

So yes, he would unequivocally say your HF machine (usually tested at about 800 CFM completely uloaded) would be totally inadequate.

I wonder if he painted himself into a corner as a proponent of the cyclone? On the Reviews page, there's a Q&A at the bottom. Question 9 specifically addresses the HF, and he says, "Doing a fine filter upgrade as recommended on my DC Cartridge Conversion page raises the airflow amply for it to be a good unit to use outside a small to medium sized shop." The fine filter is a 0.5 micron spun poly from Wynn that replaces the top bag. Wynn supplies poly bottom bags. Unless the HF leaks dust back into the room some other way, I don't see why you can't put it inside the shop with that filter. Airflow is airflow, and 0.5 micron Wynn cartridges are what he recommends for the cyclones. The problem he discusses with this conversion is solids entrainment to the filter, but it seems manageable-- and besides, that problem would exist whether the DC was inside or outside..

I bought the HF today, and am ordering the Wynn filter upgrade. Have to figure out how to test for leakage when it's all together.

Now, if the airflow is high enough with this system, 6-inch ducting may be worthwhile....

Dave

[DaveStL]

Well, I too have now spent way too much time investigating the Static Pressure spreadsheet, and it looks like it’s reasonable. I ran the math a different way (Perry’s Chemical Engineers’ Handbook, 5 ed) and got similar results. If anything, Pentz might underestimate the pressure drop per foot of duct because he appears to neglect the friction of the solids. Did he validate the spreadsheet with actual measurements?

I’m not sure the 4” ports are as bad as he thinks if you’re running two of them per tool—one on the normal dust collection port, and one on top (like a Shark) or as a hanging elephant trunk. I also haven’t investigated the recovery you get when the air slows down to main velocity.

I’m now a little concerned that the HF unit will be marginal, because it measures out with only a 10” impeller, and the “Fudged 2 HP” fan curve looks like you need to run it at 3”WC or better to keep the flow up. That’s around 40 equivalent feet of pipe based on my more severe estimate, and it needs to go it in a corner of a 9.5 x 23.5 shop with the main on (in) the ceiling. (Not a pretty curve though; does it really drop off that much there?) I'm confused here; did Pentz test with or without the stock bags in place?

It would be easier to design ducting for the Delta 50-760, but it has 1-micron bags rather than the 0.5-micron cartridge. Hmmm.

Dave

[JR]

Dave, this sort of churning DC analysis comes up from time to time. Your thoughts are similar to what a lot of people experience when trying to get up and running on a DC system. But it's really not that complicated.

Your HF DC with Winn filter will pull planer chips from the far side of the shop using 4" pipe. Make sure you help it out by putting a blast gate at every tool and use smooth pipe as much as possible. My longest run is about 15 linear feet, with a 10' flex hose attaching the planer. No sweat.

It's not going to leak. If perchance it does leak on the outlet side, you'll notice it and fix it. Leaks on the intake side are not really a concern - a little extra flow is good for the system. If you absolutely, positively have to exorcise all intake leaks, a little duct tape on each joint will fix you up.

My advice is to just get going with 4" pipe. You're going to have enough hassles figuring that out, without also adding a 5" or 6" step-down connectors to the problem.

JR

[Garasaki]

Bill's calcs are set up are to assume you are getting the required airflow thru the pipe, regardless of your system.

The correct values for PIPE ONLY RESISTANCE and assuming the default 800 cfm (more on that later too) should be (according to Bill's spreadsheet)

4" 15.8
5" 6.75
6" 2.81

<snip>

What you have to do, is change the Delivered velocity numbers from 4000 (his target number) to whatever the calculated velocity is. Otherwise all calcs are based on the target velocity of 4000.

I'm not sure I made this point clear enough.

Bill's worksheet dosen't provide the correct numbers if your velocity in the pipe is greater then 4000 (the target velocity, default value).

To get the CORRECT numbers for static pressure, you have to manually enter the Calculated Velocity into the Delivered velocity cell.

It makes a TREMENDOUS difference in your results.

[Garasaki]

Question 9 specifically addresses the HF, and he says, "Doing a fine filter upgrade as recommended on my DC Cartridge Conversion page raises the airflow amply for it to be a good unit to use outside a small to medium sized shop." The fine filter is a 0.5 micron spun poly from Wynn that replaces the top bag. Wynn supplies poly bottom bags. Unless the HF leaks dust back into the room some other way, I don't see why you can't put it inside the shop with that filter. Airflow is airflow, and 0.5 micron Wynn cartridges are what he recommends for the cyclones. ...

I think, although am not positive, that the cyclone design he recommends discharges to the outside rather then to a filter inside?

[DaveStL]

My advice is to just get going with 4" pipe. You're going to have enough hassles figuring that out, without also adding a 5" or 6" step-down connectors to the problem.

Good points, esp. about the 4" pipe. I'm trying to catch the fine dust, and although it looks like a single 4" pipe won't do that, a second 4" inlet either at the top of the tool or as a hanging pickup might be the solution. Running independent 4" mains back to the DC eliminates the step-down issues. Haven't done the delta-P calcs yet, but the flow area is ~89% of a 6" pipe.

Dave

[DaveStL]

I think, although am not positive, that the cyclone design he recommends discharges to the outside rather then to a filter inside?

He has cyclones with a .5-micron final filter that discharge inside. He advises discharging a bag-type dust collector outside, or putting the bags in a box and piping the box to a final filter. This is one of the things I don't understand: if you have a good filter on the DC, why wouldn't you discharge it inside?

The other part is, although the fine filter will increase flow rate vs the stock bags, he tests w/o a filter. Looking at the "Fudged 2 HP" curve which does appear to be the HF, flow drops to 800 cfm (presumably the definition of "ample") at 3" WC. This is where it gets tight. His spreadsheet numbers appear in the ballpark for the 6" 800 cfm case that I checked independently, although I might have some quibbles about his extra 11.5 equivalent feet for the hood (above the usual 1 velocity head equivalent for acceleration when doing conveying calcs) and the possible lack of consideration of the solids.

The bottom line is I think JR is right. Just design it to get close and put it together. Unless the twin 4" calcs come out very bad, that's what I'm going to do. The pressure drop correlations just aren't all that accurate (for example, Le/D for an ell has a +/- 25% uncertainty) so I'm not real comfortable with the lack of a safety margin in the design, but the downside would be losing some or all of the $150 for the dust collector if it has to be replaced. The 0.5-micron filter looks worthwhile on its own merits.

Dave

[williwatt]

Basically, +1 on JTimmons' comprehensive reply. I've just plumbed my new shop space with 4" PVC. I ran the hard pipe as close as possible to each tool and then made the final connection with a piece of 4" hose not exceeding about four feet in length. Counting all the turns and the hose, the longest run is probably upwards of 30 feet. The system is powered by the HF 2HP DC, and it works great, even for the CFM-hungry drum sander.

Not familiar with the black PVC pipe you refer to, but I would suggest the tried-and-true green sewer and drain (S&D pipe) and matching fittings. The reason is that this will give you the closest and easiest (to the best of my knowledge) match-up to standard 4" dust collection fittings. A 10' stick of the green pipe will run you $10-15 and the fittings are two to four bucks apiece, depending. Other kinds of pipe have certainly been used but to my knowledge the green S&D results in the least amount of hair-pulling when you go to make up all your connections.

Tom Miller helped me design my system and may have some additional thoughts for you, if he sees this thread.



In the photo above, you can just see the on-the-floor run that serves my cabinet saw. It's not ideal but it's not in a major traffic aisle and I've already learned to step over it when I'm in that part of the shop, so NBD.

Quick question: Where can you buy the green S & D pipe? I have seen it being installed, but have never seen it in a store.

Bill

[LarryG]

Bill,

I got mine at Lowe's. In the store here, it's in a separate area near the regular PVC (Schedule 40), but still separate from it. The fittings to fit the green pipe are in bins underneath.

I think people here on the forum have bought it at Home Depot, too, but the one in my town doesn't carry it.

A plumbing supply house should have it, too.

[footprintsinconc]

has anyone considered 6" piping?

[Garasaki]

Yeah that's sort of what this whole thread is about...

Dave, does it really make sense, financially and from a time savings/hassle standpoint (which seems to be your motivation), to go with dual 4" runs rather then a 6"?

[ksum]

Dave, does it really make sense, financially and from a time savings/hassle standpoint (which seems to be your motivation), to go with dual 4" runs rather then a 6"?

I cannot speak from Dave's viewpoint, but for me, 6" pvc was not that expensive. Especially since I made most of my fittings myself. (see attached photo) I used the directions, and template program at
http://harderwoods.com/tools.html
to do this. I also didn't need long runs since the piping is along the floor up one side of my 1 car garage. (see sketch attached) All told, I spent around $140 US, using 6" sewer pipe (S&D was not available in that size around here) and standard 4" and 2.5" DC connections. That does not, however, include the flex pipe I purchased for the connections. 2 2.5" hoses and 4 4" hoses allow me to hook up to everything, including the mobil thickness planer jointer, and vacuum the floor! It does cover the glued in fittings and blast gates, though. I installed this all this spring, so the prices are pretty current.

I have plastic blast gates on the 4" connections, but cut the bottom off with a bandsaw to keep dust from building up in there. I also made my own 6" blast gates at the wye based on the directions at
http://benchmark.20m.com/articles/Bl...ebuilding.html
There are 3 6" blast gates. Each is made out of 6" pipe and since there is a 45 bend at 2 of the locations, they are also the connections for the wye to bends. For the run to the rouret, I could have used a long pipe on one end, but used a 6" coupleing instead.

I have connected a bandsaw with 2 4" connections, a tablesaw with currently a 4" and a future connection for a shark guard, and a router table with a 4" connection to under the table and a 2.5" to the fence. Outside of the pipe itself, I purchased 2 wyes (laterals), 2 45 degree bends, 2 6" caps, and 1 6"x4" reducer. The reducer is shown in the picture. I used a 4" hose to 4" pvc fitting in the small end, but had to heat the pvc to soften it to get this to fit.

For the router, the 6" run ends at a cap with 2 holes drilled in the end, and the propper fittings glued in place.

In the photo, you see 3 4" connections. Currently the table saw is hooked to one and the bandsaw to the other 2. When I get the shark guard, I will use the second wye to connect to both ports on the table saw. That will leave this connection as a spare for hooking the planer or jointer to. That leaves me with 2 spares in the center of my shop. This run is shown between the bandsaw and table saw in the attached sketch. The DC pipeing is in light grey, outlined in blue. The darker grey is all work surfaces at the same height.

[DaveStL]

I'm back to 6" now. The dual 4" isn't going to allow enough air. I didn't realize the difference is that dramatic.

It turns out that at 800 cfm, the 6" has a big pressure drop advantage over twin 4" pipes, even though the velocities are not much different. Pressure drop in the pipe is related to velocity squared divided by diameter. Two 4" pipes have 89% of the cross-sectional area of a single 6" so the velocity is 12.5 % higher, and the diameter is 2/3 as big. Just for the air, the head loss is 90% more [(1.125^2)/(4/6)-1]. The solids are an additional complication because they move a little slower than the air that's carrying them. They get closer to the air velocity in the smaller pipe so their contribution gets even bigger; the overall pressure drop per foot of pipe is as much as 117% more than for a single 6".

A good way to look at this is two 4" pipes have 89% of the cross-sectional area of a single 6", but 33% more wall for the air to rub against.

Need to minimize the 4", esp. 4" flex, and bring in the 4" that carries most of the solids downstream (closer to the DC) to avoid leaving piles of sawdust.

My other problem is layout of the shop, because it has a sink with an ell counter that dictates a lot of the equipment placement.

I'm glad to hear the 6" isn't as difficult as it seems!

[DaveStL]

I have plastic blast gates on the 4" connections, but cut the bottom off with a bandsaw to keep dust from building up in there. I also made my own 6" blast gates at the wye based on the directions at
http://benchmark.20m.com/articles/Bl...ebuilding.html

ksum,

That looks like a well-planned and -executed system. If I understand what you did on the 4" gates, would simply orienting them w/ the slides opening downward have prevented the buildup? This would obviously be difficult to operate if they're on the floor, but I'm looking higher....

Dave

[ksum]

ksum,

That looks like a well-planned and -executed system. If I understand what you did on the 4" gates, would simply orienting them w/ the slides opening downward have prevented the buildup? This would obviously be difficult to operate if they're on the floor, but I'm looking higher....

Thank you, Dave. It actually had about 6 changes in 4 phases of construction that started after a lot of reading and a week of layout planning. I built each part as I needed it over the course of a couple months. Bandsaw first, then tablesaw, next the reducer in the pic for jointer and planer, then to the router with the new table saw hookup wye installed at the same time. That is why there are 3 4" gates and the reducer as shown in the picture. Currently the table saw hooks up to the right hand gate. When the shark guard comes in, this will move to a 6x6 wye next to the table saw, as shown in the layout sketch. The wye is in place, with a cap on the side for now. Phase 5 will be installing the 4" and 2.5" connections for the saw and 2.5" pipe up and overhead for the shark guard. There may be a 6th phase for a 2.5" hookup for a sander, but that is not in the near future. The nice thing about the PVC is that I have done nothing more than push the pieces together.

The picture is taken looking down at an angle to the piping between the band saw and table saw. The pipe is about 5" off the floor (it sits on scrap pieces of 4x6), so the top of the 4" blast gates are 18"-24" above the floor. It is easy to bend down between the 2 saws and open/close what I need. The gates lift to open, push down to close. So the bottom is cut off to allow any dust to hopefully fall/push out the bottom and hopefully not build up. If you had them on a vertical run, I would think they would push anything out, the same as the metal ones. I figured it was worth trying for the cost savings.

Last night I made a change to the 6" blast gates. You can see 2 in the photo's background. Currently to open them, I slide a piece of masonite out of one and into the other. That left a 1/8" opening at both the top and bottom of the home-made gates. I glued a strip craft foam to one side, on both top and bottom. I knew it would help some, but was surprised by how much it felt like it changed things based on the difference in pull on my hand in a with/without foam anecdotal "test."

Now I just need to wire the 220 volt receptacle to a couple 3-way switches located at each end of the garage. I am already tired of walking 10'' to turn the DC unit on, and KNOW I will either loose a remote, or I'll will be at the router and the remote will be at the band saw, which means I would be walking the 10' anyway.

Karl