Plumbing parts for dust collector systems?

[George]

I have read a few posts in the past from people who have used plumbing parts for dust collector systems. I wanted to modify my system and I thought I would try to use 4" drain pipe for some runs, as I assumed that was the plumbing product these people were using instead of 4" pvc flexpipe.

I checked the 4" white pvc and the 4" black ABS pipe at Canadian Tire but both were slightly too large to have 4" flexible pvc tube slipped over it.

My question is, how are people adapting plumbing pipe for dust collection. Do you use duct tape to make connections? Or, is there something else here that I am missing?

[Mike G Soo On]

If you are going to use 4" drain & sewer pipe for a main run with down drops, than you have to put in a blast gate.When you use a blast gate you use the large end of a 4" pipe to go over the main, the piece you use is about 6" long, then the gate than a piece that fits into the flex pipe.
This can be a bought piece or a home made piece, mine are out of a 3lb coffee can for 6" and tomato can, vege can any of the medium size ones, the flex pipe fits right on it.

Mike G

[Michael in Port Alberni]

I am using the 4" perf pipe with the hole duct taped over, and some creative use of duct tape to transition to various fittings. Some may think it somewhat mickey mouse, but the system is very efficient and if there is a blockage it's easy to clear. If you have more cash than you know what to do with, you could buy all the dedicated parts, but to me that's a waste of $. The only dedicated parts I have bought are some 2 1/2 flex hose, blast gates and a few transitions for the hose. The rest can easily be adapted from what you have in the shop.

Cheers

Michael

[Wally in Calgary]

George -- 4" PVC works great for DC runs. Here is a pic of a blast gate that use's only one coupling cut in half and a few leftovers. If you want to join the flex to the PVC then just heat the flex a little and turn it into a pc. of 4" pipe then tape over the joint.
Cheers Wally!!



http://www3.telus.net/public/cass1976/Wally'sWoodPics/Blast%20Gate%203.JPG

[Ken in Regina]

Here's how I did the connection to my tablesaw with white sewer pipe parts. I just used my tablesaw to cut the slots, squeezed them together into a taper and wrapped it with clear packing tape. The flex hose fits over it nicely.

As you can see, I have a plastic connector threaded into the end of the flex hose. It is slightly tapered design so that it's a jam fit on anything you slip it over. It makes it much easier to connect than the bare hose.



http://www.sasktelwebsite.net/gansk/unpublished_pics/tablesaw-dc-port2.JPG

[Dan & Colleen]

I tried connecting my shopvac to my tablesaw by mounting a piece of paneling to the bottom of the saw housing and connecting the hose to a hole in the back of the saw. It didn't seem to work too good. The dust wanted to come out the slots in front where the blade raise/lower handle comes out. There are also air slots on the sides of the housing. What am i doing wrong? Does the hose have to go on the bottom of the saw? Do I have to cover over the air slots in the side?

TIA
Dan

[Doug in Keswick]

I have one question with regards to the sewer pipe for Dust Collector piping are you running a ground wire inside the piping to each tool it is hooked up to to prevent explosions from static electricty greated in the pipe.

[Eaglesc]

Contractor saws aren't the easiest thing to to hook up for dust collection but try to do it with a shop vac is like "P"ing in the wind.
The shop vac won't move enough air at the correct speed to hold the dust in suspension.
There is a difference between dust collection and sucking up sawdust with a shop vac.
A shop vac is meant to clean up a mess after it has been made.
A D.C. system is meant to get the dust at the source before it becomes a health hazard.
If you want to do a little research on Dust Collection,get a big drink of your choice and settle down for some reading:



Bill Pentz (http://billpentz.com/Woodworking/Cyclone/Index.cfm)

[Eaglesc]

Explosions from home Dc's are nonexistant.
You might get an uncomfortable shock,but there has not been a documented case of a home DC exploding.
Not to say teoretically it couldn't happen just that it hasn't.

[Bob, in Lachute, Qc.]

Hi Eagles, I just posted something on this very subject, at Sawmill Creek.

We quite often see posts stating that "this doesn't happen", like it's a given fact. Well lemme ask this, how would you ever know????? When was the last time a home fire was covered on the evening news???? or made it to the papers???? The only time you'll hear of a homefire, is either on a small local broadcast, or if an entire community risks being wiped out by a forest fire.

DC fires can be started in other ways too. A nail hitting a steel impeller, with a spark, smouldering on top of a pile of dust, being fanned by incoming air.

Industrial applications do not allow use of combustible ducting, to convey combustible waste. Could your insurance company balk at a claim, suggesting the inappropriate use of combustible pipe????You'd have to be able to prove this was not the case, in a court of law. An expensive process.

I've seen the posts suggesting that there is no risk, but it didn't address any of the points I've made, AND, it also assumed that because they never heard of an incident, it just wasn't so. Why WOULD they hear??????Are they on a special notification list????

Most people use PVC because they THINK they'll save money compared to buying metal spiral pipe. It just isn't so. Sure, if you go and buy retail, from a specialty outfit like Oneida, you'll pay through the nose for spiral. No wonder. They buy it, pay to have it shipped to their location, store it, advertise it, then ship it out. You pay for all those things. Buying direct from a small local manufacturer, you'll actually pay less than PVC. These guys are everywhere. Just look in the Yellow Pages under "Piping". Another approach, is to contact any heating and ventilation contractor. They can point you in the right direction.

I paid $17. Canadian/ $12.50 US, for 10 feet of 6" metal spiral pipe. That $17., was tax included. Cost me less than PVC, and totally eliminates all the concerns about static/fires/grounding, anddddd, the fittings are more appropriate to dust collection.

http://www.woodweb.com/knowledge_base/PVC_piping.html

All the best, Bob

[Ken in Regina]

Dan, as Eagle suggested, you probably aren't moving enough air with a shop vac to get it done very well. If you look at my picture, you will see that I'm sucking through the panel I put in the bottom of the saw. Here's what I did to close in some of the back end of the saw.

I did not try to plug up all the holes because I need enough air flowing into the body of the saw to replace what the dust collector is trying to suck out. What I'm trying to do here is direct the airflow in about equal amounts from the front (around the adjuster wheels) and back so that the dust will get pulled down the dust collector chute.

http://www.sasktelwebsite.net/gansk/unpublished_pics/tablesaw-rear-panel.jpg

[Bob, in Lachute, Qc.]

Hi Dan,

It's quite easy to make an effective dust-hood for a small contractor saw, even using just a shop-vac.

I'll try my best to describe verbally, how I made mine, for my old contractor saw.

Look under the saw, and take the measurement of the opening. Make a piece, equal in width to the back of the opening. That piece could be made of hardboard, or lauan, or anything handy. That piece will be fastened to the saw, using duct-tape, or something similar.

Let that piece hang down toward the floor. Determine how long you want to make that piece. About 1 foot would be ok, maybe 15". Now, taper that piece, starting with full width where it joins the saw, and tapering inward from both sides, 'til you have roughly a 3-4" width at the bottom edge of that piece.

Now, piece #2, will be the piece that fits at the front edge of the saw opening. Again, make that piece the full width of the saw's opening. Measure the distance from that edge, to the bottom edge of the first piece you made. Naturally that 2nd piece will be longer than the first, since it's on an angle. The rear piece would be vertical. Tape the two pieces together at the bottom. Viewed from the side, you have a "V" like structure, but one leg of the V is vertical, the other on a slant.

The sides, are identical. Again just make a piece, the same length as the front to back opening under the saw. Make the other edges match the side openings of the first two pieces. Tape them.

You now have a square funnel. Drill a hole at the lower back piece, near the bottom of that "funnel". Make the hole just barely undersized for your shop-vac's nozzle. Now, carefully sand the hole larger until the shop-vac's nozzle fits in the hole, but stays in position by friction. Voila, you're done.

I used a large shop-vac, with 2 1/2" hose. It worked like a charm, took no time to make, and was made from scraps. A similar plastic hood from Craftsman, was $47 at the time. It lasted for years, and was still on the saw when I sold it.

[Allan Johanson - South Su]

Hi Bob,

The points you brought up really have nothing to do with the grounding issue about running a wire inside the pipes to prevent a static charge.

A nail hitting a steel impeller is a real concern. Running a floor sweep can be dangerous if you stuff bits of metal in there with fine sawdust.

But running a wire on the inside of a plastic pipe is another issue entirely.

Check this out:

http://mywebpages.comcast.net/rodec/woodworking/articles/DC_myths.html

While metal pipe will indeed deal with the static buildup issue if you are scared of it, the metal will not help those other issues you stated.

I wish I had your suppliers for metal pipe around here. Even the distributors charge a small fortune! I need to keep looking. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Allan

[Bob, in Lachute, Qc.]

Hi Allan,

I'm familiar with Rod Cole's article. It's been around for years. What I'm amazed at, is that this guy says he never heard of a shop fire with PVC. Why the heck would he??? Is he on a special notification list???? When was the last time you ever heard any details of any housefire???? There's been a dozen or so in and around Lachute in the last year. Did you hear any details as to what caused those???? Of course not.

The points I raised, deals with fire insurance companies. The very fact that they do not cover industrial use of combustible pipe, when conveying combustible waste, speaks for itself. If you ever did have a shop fire, could they balk at paying out, based on that very reason????

Here in Lachute, about 6 or 7 years ago, an outfit called Charlebois et Fils, burned to the ground. They specialise in architectural doors and windows. The fire started when the first worker in that morning , started the dc. He said he heard a low rumbling noise, and that was followed by a huge explsion. The resulting fire burned so hot, even the metal frame of that factory melted, along withh all the machinery. Took 2 days to put it out. There were no other workers at the plant, yet, and no machinery running. Did YOU hear about that fire???? Do you thing anyone notified Rod Cole????? 45 men were put out of work for over a year, 'til the factory was rebuilt. They probably used metal pipe too. Who knows how it started? Probably dust that had settled in the pipes, suddenly letting go, and sending a cloud to the cyclone. What caused the spark????

Anyway, back to the pipe. Quite aside from the fact that the fittings are better suited using metal pipe, there is simply not ONE advantage of using PVC. The ONLY "claimed" advantage is "price". Can you think of even one reason why, OTHER than price???

As I said, you ain't gonna find this stuff at the big-box stores. You have to look around a bit. But virtually any heating and ventilation contractor, can put you in touch with a small local manufacturer. They're EVERYWHERE. Looking in the Yellow pages under "piping" should get you there. Check out local industrial parks too.

The perception that PVC is cheaper, is flat-out wrong. I had no trouble locating some, but it did take a bit of "digging".

Take a look at Dave in Acton's set-up, or Gus in Maple, or Dennis in Montreal. They all got good prices on metal spiral.I'm sure that's not exclusive to eastern, and Central Canada. Surely there are some manufacturers near you. Just gotta do a lil' digging.

All the best, Bob

[Eaglesc]

I use anything that will move air.
The only benifit of using spiral that I can see is you can run loger lengths with fewer hangers.
I have been building and installing ductwork for 15 years and the need for spiral is a waste of money in the home shop.
There might be a small benifit in improved air flow but not to offset the cost of standard galvaized pipe.
The issue of nails ao,etal fitting the impeller can be solved with a chip separator.Means less bag emptying.

I use a mix of galvaized pipe, PVC,flex pipe and coffee cans.(13 ounce)
Aluminum tape, duct tape, hose clamps, and plastic bags.
It don't have to be pretty it just has to work!

[Bob, in Lachute, Qc.]

I agree Eagles, but there you go again, suggesting spiral is a "Waste of money". I don't understand how that image gets generated. I found it to be CHEAPER than PVC. That being the case, why would you want to use PVC??

All the best, Bob

[Allan Johanson - South Su]

The price of spiral vs pvc is TOTALLY dependant on your area and the attitude of the wholesaler. It isn't right to say what you can find one one place can be found in another.

I went to the wholesaler that sells to the distributors that in turn sell to the retailers. I bought an 8x8x8 wye for $30, normally $50. Garrett bought an 8x8x8 wye in Victoria for $20. It depends on so many things.

In any case, you were curious about an advantage for PVC over metal....I'd bet that PVC will contain fewer leaks when installed by an average person than a metal system.

BTW, for myself, I'll be going all metal. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Allan

[Bob, in Lachute, Qc.]

Allan,

I have no issues with PVC. I see the guys do it all the time. That's not my point.

I mentioned the insurance possibilities.

Personally, I prefer metal, and for me, it cost less. Same for everyone else I know, who actually went out to look for some.

The whole idea of suggesting that PVC costs less, or that metal is sooo expensive, is NOT correct, but that idea gets repeated constantly. Sure that will be the case if the only comparison made ,is some web-site re-seller's metal pipe, vs a big box store for PVC.

Metal, costs less, and eliminates every concern, so why not? All the industrial guys use it. No doubt the wyes and elbows are more expensive, but they're also less resistant, and more appropriate.

Nothing wrong with HVAC fittings too, as long as you go long radius, or 45 degree take-offs. Two adjustable 90's, set to 45 degrees each, and put end to end, make a great long-raduis 90, and it costs peanuts. About $3.00-$4.00 each.

All the best, Bob

[Allan Johanson - South Su]

You've got to watch some of those sheet metal pieces though. Some are crappy tack-welded scraps crudely formed into shape. I've seen some ugly stuff out there.

So ugly in fact that I've been thinking of making my own wyes and tapered reducers.

You've got to watch for leaks with HVAC fittings too. Leaks will kill your system and HVAC parts hemorrhage air.

For those of you who choose to use HVAC parts, do yourself a favour and buy some of that "high velocity sealant" or a quality foil tape. Not duct tape.

Cheers,

Allan

[Bob, in Lachute, Qc.]

Allan,

I sure have to agree on that one. In fact, I probably own the single ugliest long radius "gored" elbow I've ever seen, lol. The welds are horrible. My grandmother could have done better.

That said, I'm quite sure if I took it back to Mega-Tube, they'd switch it for a better one. Works fine, however. Good guys to deal with in the Montreal/Laval area. Amazing prices, too. They even cut my 10 ft lengths to size, for free.

Those gored elbows, are really expensive, retail. About $60. each. They were about half that at MegaTube.

I'd only buy those as a last resort, on a really restricted run.

All the best, Bob

[Bob, in Lachute, Qc.]

He,he,he, I THOUGHT that would "git yer attention", lol. I stuck this in down here, where others might not notice.;-))

Allan,
I just got off the blower with Belfab, and spoke to a helluva nice guy by the name of Carl Martel. Veeeery helpful.

I called to ask about a caged back-inclined fan-wheel, their "RBI" fan-wheel. Carl's gonna send me all the specs, right down to noise specs, as well as pricing for those. They'll make 'em up in any size you want, with almost any material you want, steel, aluminum, whatever.

2nd from the bottom of this page,
http://www.belfab.net/blowers.html

I called specifically about the 15", but he's sending details on the 12" as well. Might have it this afternoon. If not, Monday.

I also spoke to him about blower housings.

One of the off-the-shelf blowers, for the LW series dc's, produces 1760 cfm AT (are ya ready fer this?) 1760cfm,AT 8" SP. That's with a 9" intake I believe. Now that's just a plain radial fan-wheel. He's gonna provide the details, of that housing with the 15" caged B.I.

Oh, I also asked him about aerodynamic inlet cones, or "bells". They're available as well. Can reduce entry-losses, at the blower intake. Would also be great for plain-end ducts.

One of the series they have is the "Hummer" series. That's part of the "LW" dc line-up. Those run huge impellers, but at half speed, 1800 rpm. Those reduce noise dramatically, due to reduced tip speed. QUITE interesting.

Have a greatttt weekend. All the best, Bob

[Allan Johanson - South Su]

Careful...Phil might be reading this. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Sounds interesting, Bob. But you really shouldn't get me thinking about stuff like this because I might have to upgrade my wimpy 14" impeller before even really using it! http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

But seriously, if I find my current system too wimpy I'm glad I bought the massive motor because that can spin pretty much anything I'd ever think to use.

I like having oodles of sucking power at my disposal. Consider your potential situation where you were thinking of buying a CMS and were curious about room for a good DC hood. If you have the power of a small tornado in your shop, you can stuff four 5" hoses at each side of the box for the ultimate in sucking power to grab those pesky dust particles. That 15" BI fanwheel can probably do 2000cfm at a lower SP so that would be a great way to deal with it.

You could have a small "octopus" at each tool and no speck of dust would ever escape. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

For my current system, I'm probably going to run 7" branches to the tools and that will easily handle two 5" drops at each tool. For a case like my Performax that has a built in 4" fitting on the case, I'll probably leave that alone (I'm afraid of ruining the lid). But I'll make a custom second hood with a 6" drop to gather more dust. Or maybe run two extra drops with 4" hoses in front of and behind the spinning drum. I'll study the dust flow patterns after hooking up the initial 4" hose and go from there.

But the cool thing is I have the Magnehelic gauge so I can do specific testing for each tool and see what the airflow is and how much headroom I'll have. Some machines might have up to 1600cfm to play with and others might only have as little as 1000 cfm. But I'll know exactly what I have to work with and I'll custom tailor each machine for the best dust collection.

I'm looking forward to it.

Allan

[Garrett in Victoria]

[Ken in Regina]

Okay, so that creates lots and lots of questions, like:

- can that RBI fan be retrofitted to the JJ? What cost?

- could you use one of those blowers as the basis for a home-brew outfit like the one you described when we were talking about building a preseparator? E.g. a box with two barrels under it, suck into one end and out the other into a couple of needle-felt bags .. using this blower to do the sucking?

Got lots more but that oughta do it for starters... http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

[Bob, in Lachute, Qc.]

Sounds good Allan. I'm quite certain you'll be fine as is, anyway. I can't imagine having to upgrade yours at all really. I was thinking though, that by playing with the inlet plate diameter, you MIGHT get better SP response. You simply may not need it, too. Holy jumpin, you're probably getting over 4,800-4900 fpm, as is.

Don't forget this also, SP drops to about 0.03"/ft at 4000 fpm, when you use 8" pipe. With 6", it's 0.04, or slightly higher.

By playing with the inlet plate, it wouldn't necessarily mean using a smaller "uptake" tube, inside the cyclone. That could stay almost the same, to control velocity through that portion of pipe. A reduction, could occur right at the inlet. That's where the aerodynamic inlet cone comes in, to reduce entry-loss.

I was thinking primarily along the lines of my Torit clone, and I remember Ed in Leaside mentioning something, too. I was looking for a source alternative to Sheldon, also. With the B.I. I just don't need to deal with the weight.

I'd kinda like to build one, but just can't justify it at the moment. The Belfab gives me all I need . I don't plan on expanding my shop, for at least a year, so if I can get a half decent price, I just may start the ball rolling early.

Those LW blowers, are interchangeable/upgradeable. I was thinking they might have a used one, from an upgrade they may have done.

That being the case, I'd take my time to build a dc for my next shop. That would be a two-man shop, so the larger shop capacity may require it. Mind you, I might just split the shop, and run two JJ's. One run, down each wall.

More than anything, I'm curious about the B.I.'s SP performance. Most of the really strong "draw" dc's I've seen, use intakes, or piping, equivalent to 1/2 impeller diameter, too. That relationship, exagerates even more, with the high-pressure blowers. Wouldn't take much to experiment with that. Just an MDF ring, with a nicely "rolled" inside edge, for testing. There's your excuse to get that OneWay, lol.;-))

With dirty air, you'd pretty well have to use metal. Ceramic would be great, too. Just find a Crafts-person, to make one, and bake it. Then epoxy it to the intake plate.

Well, I'm rambling. Time for supper. Gonna be a late night. I wanna watch Jacques Villeneuve, qualify P-1, for the Shanghai Grand Prix, yippeeeeeeeee.;-))

Have a great weekend. Bob ;-))

[Bob, in Lachute, Qc.]

Hi Ken,

The caged B.I.'s(Back Inclines), are strictly a "clean-side" fan-wheel. They are better suited to small material hits than an airfoil however. They also require less power to drive, than a radial fan-wheel. Mechanical efficiency , runs about 85%. Airfoils, 95%. Those B,I.'s, are also not prone to buffetting like the airfoils.

They're ideal in pull-through cyclones, because of quite advantageous SP curves. The curves are steeper than an equivalent diameter radial fan-wheel, with less cfm drop-off, as SP increases. Most of the commercial cyclones, like the Torits,use caged B.I. fan-wheels, especially over 3 hp.

The operating range of the 20" body Torit, is between 1250- 2500 cfm, with an 8" inlet, using the 3-5hp caged B.I. Imagine 1500 cfm, with a staggering 11.4" of EXTERNAl SP. That represents a MONSTER duct length, in the order of 250-300 feet or more. Jaw-dropping suction.

http://www.donaldson.com/en/industrialair/support/datalibrary/000984.pdf

You COULD make a dc using that fan-wheel, just with a box, and some drums, but it would have to be styled along the lines of a Pulse-Jet dc, or a Bag-House dc. Like this,,,

http://www.donaldson.com/en/industrialair/support/datalibrary/000985.pdf

See how the dirty airline, comes into the side of the funnel???? The waste immediately sheds velocity inside that large body, and drops into the drum(s). The large upper cavity, REALLY reduces velocity, so small particle filtration is excellant, especially with so much filtration surface. You could easily copy that, mount it to a wall, with the blower at the top of the cabinet, pulling air. You could use bags, or cartridges.

I'd probably go to a service center, for large trucks, and get some discarded air-filters. They often have to pay to dispose of those. Blow 'em out with a compressor, and mount a half dozen or so, on a baffle, inside the cabinet. You could have them flow inside/out, OR outside/in. Totally depends on how you mount 'em to the interior baffle.

I'd recommend outside/in for those, so I'd have the filters hanging downward from the baffle, inside the cabinet. To reverse that, just flip the baffle, so the cartridges or bags, are up top, above the baffle. This way, the bags would inflate. That top compartment, would be only clean air.

Piece o' cake.;-))

All the best, Bob

[Allan Johanson - South Su]

Hey Bob,

I've got an SP question for you.

Since I got a reading of 1711cfm with 9 feet of 8" pipe and a tight HVAC 90 deg turn on the end, and at the same time the SP reading was 2.6".....

Since I don't have my charts handy, I fired up Bill's static pressure spreadsheet. I entered 9 feet of 8" pipe and one 90 deg turn. I also entered the cfm of 1711. BTW, the velocity in 8" pipe @ 1711cfm is 4902fpm.

His calcs say the SP of that ductwork is 0.99".

So....the question is this:

Is the SP loss of my cyclone 2.6" - 0.99" = 1.61" at that point in time? Some of that is probably due to entry losses at the end of the duct...or is all of that 1.61" at the end of the duct and the cyclone body itself not registering any SP changes in a cyclone? That last part doesn't make any sense.

I'm just trying to make sense of these numbers because things aren't adding up if I take into account what I see commonly written about SP loss of my cyclone body and entry losses at the end of a duct and it's hurting my pea-brain. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

BTW, pitot tube placement in the nine foot main duct was according to Dwyer specs.

Oh yeah...my cyclone is 20" diameter and was intentionally built that way to lower the resistance and increase the airflow. Normally Bill's cyclones are 18" in diameter with the larger impeller. Also, I rounded over the lower blower plate (where the 10" dia cyclone body outlet joins the plate) for smoother airflow to the fan.

Allan

[Bob, in Lachute, Qc.]

Well Allan,

It's 3:22 AM, I just finished watching the live telecast of the Chinese Grand Prix qualifying, in Shanghai, andddd, I'm having a nice tall, ice-cold Grolsch, as a night-cap. Lemme see if I still have any active brain-cells at this point. I'll probably look at this in the morning , and wonder "What the hell was I thinking, lol.???"

First off all, the inlet, or entry loss of the cyclone, has now been eliminated, or rather "moved", to the duct end.. I know Oneida doesn't see it this way, but who the hell are they, lol???(just kidding). seriously, that's how I see it at the moment.

Figuring the exact sp of that straight pipe, and elbow, would require using a reference of some sort. So let's use 4000 fpm, and a value of 0.035" SP, at 4000 fpm. That would make that elbow, depending on what type it is, (I'll assume smooth-walled, long radius) That elbow would be equivalent to 12' of pipe. So total equivalent length is 21 feet.

To calculate length SP, using the fan laws, you'd have to square, the initially calculated resistance for 21 feet of pipe. So here we go.

21ft. of pipe x 0.035"SP/ft=0.735" SP AT 4000 fpm.

ACTUAL velocity, is 4900 fpm. So that is an increase of, or multiple of 1.225, sooooooooo
1.225x1.225=1.500" x original SP(.735", soooooo
1.5 x .735= 1.1025" for that duct.(length only)

Now we have to add entry losses. I'll assume you have a plain end duct. To calculate that, I'll use the calculator at Beacon Engineering.

Well, that gave me 2.86" entry loss, for a plain-end duct, using 8" pipe, and 1700 cfm. Using the calculator, and adding the 21 ft length, I get a total of 3.769" SP. Velocity pressure, is 1.482" SP

Deduct Velocity pressure, from 3.769, and you get 2.287" SP. Hmmmm, we're pretty darned close there. I used a long radius elbow value, and I just realized you said tight HVAC. That difference, would be the increase undoubtedly, Roughly .3" SP, so that tight radius elbow, is actually acting like a 21 ft duct/ at 1700 cfm.

Make sense, lol?????

I wouldn't worry too much at this stage, about the low SP number, Allan. That's really wide pipe, with low resistance compared to the same velocity through a 6" pipe. It's 0.03" SP/ ft,for 8" pipe, instead of 0.04, for 6" Pipe. So duct length increase, won't be very punishing. Necking down might be a problem though, and that's why I suggested to try that reducer at the blower inlet. Anyway, it's way too early for that at this stage.

The next step would be to see how much cfm drop-off you get, by adding more pipe. Do you have an extra 10ft length there????? Add that, and take another reading. Let me know what you get.

While you're at it, try to add a reducer at the end of the 8" pipe. Perhaps to 7", then 6" too. Take both readings.

I suspect there'll be severe drop-off in cfm, with the 6" reducer. That's where the blower inlet reducer might help. At this stage, I'm quite certain if you use a 7" blower inlet, you'll see improvement in cfm, with the 6" reducer that is at the end of the pipe. I know that's a pain to take apart, so maybe do it at your convenience.

Something else to remember, when using 8" pipe, you no longer need 3500 fpm, for a horizontal main. 3300 fpm, is the minimum "recommended" for 8" pipe. So a gain there.

Once we see the effect of adding another 10 ft pipe, we can start to plot a system curve, to project some numbers. You'll probably be a helluva lot better off than you think. Don't forget, the resistance value per foot will drop, with each foot of length you add, because you'll be pulling less air. So adding 30 feet of pipe, doesn,t mean it's calculated at 0.03" SP per foot, or .9"SP

What it does in essence, is create a new "system curve".

The original high SP, of the first 30 feet of pipe we already measured, will drop. So will the entry loss, at the end of your NOW 60 ft duct. That alone, will make a big gain.

Dang, I think the dog got my Grolsch, it's emptyyyyy. And at this stage(4:35 AM, now), so is my brain. I'm off to lala-land. See you in the morning.

All the best, Bob

[Allan Johanson - South Su]

Hey Bob,

What I'm really curious about is on Bill's spreadsheet he says to use 3.5" SP loss for a neutral vane cyclone and 3.0" SP loss for a cyclone with an air ramp. A WOOD-style cyclone would have 4.5" SP loss.

You mentioned Terry got his cyclone down to 1.5" SP loss.

So....when I do a test reading in a short 9 foot length of 8" main duct and read that the SP is 2.6" while flowing 1711 cfm, am I correct in thinking the 1.61" SP unaccounted for is my SP loss due to the duct entry loss plus the cyclone preseparator loss?

Taking one step at a time.... http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Allan

[Ed/Leaside]

Have you tested the blower with just the 9 foot length of 8" main duct, as in no cyclone? It shouldn't be too hard to jury-rig that set-up.

[Allan Johanson - South Su]

No I haven't...but I do happen to have a 10"x8" reducer (for a planned muffler) that I can use to hook up my 10" cyclone outlet tube to my 8" main duct....

One of these days I'll give that a shot.

[Bob, in Lachute, Qc.]

Allan, goodmorning.

I'm not certain how you have your tester set-up, nor do I have experience with those. From what I gather, you can set it for varying functions. Is that your case????

I've seen references to "Total pressure", on some sites. In that situation, Total pressure, equaled velocity pressure, AND static pressure.

I thought of something else last night, after I went to bed. Did you take a single reading???? If so, you might have the SP reading, for the centre of the duct only. From what I understand, it should be a 16 point reading, progressivley closer to the duct wall. Most of the HVAC guys, use a lil' trick, which yields very similar results. I saw that on Dwyer's website. They use the single centre reading, and multiply it by 0.9.

Sooooo, if you had a 2.6" SP reading at the centre, and multiply by 0.9, you get slightly over 2.3" SP. overall. Wasn't that exactly what we came up with last night??? I'll have to re-read it. Coffee's only starting to kick in, still got cobwebs.

Another thing I thought of, to illustrate the effect of the smaller blower inlet plate, vs impeller diameter.

If you look at the Wood Magazine Test, Dec. 2003, and look at the big Penn State, well, total cfm was dismal. Especially considering it has a 14" impeller. It pulled BARELY over 800 cfm, at a low 1 1/2" external SP. The reason is obvious. They use all 6" porting, for the inlet, even the outlet, from what I understand.(Yuk!!)

But there's something else here.

Take a good look at the SP curve. You see how it is VERY steep, compared to all the others?????. At one point, that Penn State, is even pulling MORE air, than the Top cyclone in the test, the Oneida 2hp Commercial.

That's a prime example, of reducing the blower inlet diameter, in relation to the overall impeller diameter. That's where the static pressure performance is being created.

In the Penn state's case, although it has less airflow initially, (undersized pipe) it is LESS affected, by lengthening the duct network.(External SP) Mind you, it's happening at 500 cfm, and that's too low a volume for 6" pipe anyway. Velocity would be a paltry 2500 FPM. But none the less, a good illustration.

In the Oneida's case, using the same 14" impeller diameter, it pulled much more air initially. 50% more. That's because it used a 7" intake. The SP curve, is not as steep, however, and it is more sensitive to duct-length increase. Necking down to 6" pipe, would result in a big SP hit, and much lower CFM.

Obviously, you have to chose the characteristic you want, or try to balance the two.

If a guy has a very restrictive network, he would require a dc with better suction, or a high SP tolerance. He'll move less air, but he'll get better results at the farthest point in his network. For a guy with a nice efficient network, well, he'll be better off with a high air volume, and not necessarily strong SP performance. Now in your case, because of that really wide-diameter blower inlet(10", isn't it??)Well you're moving a huge air-volume.

(This is for lurkers, and newbies") That illustrates why I ALWAYS say to people, don't chose the dc first, then try to adapt it to your needs. Start at the OTHER end. Start with the single most restrictive requirement. Your "worst-case" scenario. Only "THEN" chose the ducting you need, to achieve the desired flow. 6" for 800 cfm, 7" for 1,100 cfm, and 8" for 1,400 cfm.

Once that individual has decided that, he needs to calculate his total duct length resistance for that "worst-case" branch. If he want's 800 cfm, and his branch measures 6" diameter, and 5" total SP resistance, well he needs a dc that can provide 800 cfm "AT" 5" "External" SP. If not, he'll get lower cfm. Perhaps too low for that pipe diameter to provide adequate velocity.

So only THEN, should he chose a dc that can meet that need. The result will be a marriage made in heaven.

Back to you, Allan. You just may have achieved exactly what you intended to do in the first place. You wanted to move a lot of air. You'll do exactly that with the 8" pipe. Forget the dc, and the ducting. Just think about the air in front of the inlet, at the tool.

You have PLENTY of velocity to get the waste to the drum, so THAT is not a problem, That large diameter pipe, has LESS restriction value per linear foot, at lower velocities.

Sure, suction will appear stronger as velocity is increased, but what's the point????? You don't need it. Having 7000 fpm velocity, won't get the waste to the drum any BETTER, than 4000 FPM velocity. Only quicker. Waste of energy.

Your concern since the outset, was to capture as much of the "Fines" as possible, and only high volume will get you there.

Just think about those big Denray downdraft tables. They move 5000 cfm, but at VERY LOW SP levels. That's where I'm going to use my big airfoil blower. (2400-2700 cfm). It's perfect for that application, yet useless for a dc.

In your case, the ONLY time I'd start to get concerned, is when the duct velocity STARTS to drop below 3300 FPM, and you're a longggg wayyy from there. I'd sure as heck not waste energy with a tight HVAC elbow, however. That 21 ft equivalent length, is awesome. That's the entire length of my shop, lol. That's why I use over-sized diameter elbows, on my preseparator. You just don't need the velocity through that elbow, and it drops the resistance in half, or better.

All the best, Bob

[Bob, in Lachute, Qc.]

Man , oh mannnn, I can ramble, lol. I just reread your question, and I'll try to be "A LOT" more specific.;-))

From the way I understand your measurement, it is a "single performance point" measurement, and only shows the difference between outside pressure (outside the duct), and inside pressure. It's that differential that forces airmovement. It's purely a "specific performance point" reading, and has nothing to do with the resistance of your individual components, like 3.5" SP for the cyclone, for instance. It's just a "RESULT".

If you start with just a free-flowing impeller, then add a blower housing, inlet, pipe, outlet, filters, well all those things add resistance, to bring you down from the initial "free air" volume. You might have been moving 2500 cfm, before adding all those components, maybe 3000.

What you're left with, is a reduced flow of 1700 cfm. That total component resistance, has ALREADY been impacting on the "free-air" measurement.

What your measuring, is the "resultant flow".

From there, you'd only have to figure out the effect of adding duct length. You'd do that using a "table", for a guideline.

If you had a system curve already plotted, it would be easy. This present way, involves doing a bit more calculating, and testing. No big whoop.

All the best, Bob

[Allan Johanson - South Su]

Rambling? Never! http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Yeah...I got all that stuff. I know that the 1711cfm @ 2.6"SP was the result of that particular layout/cyclone at that point in time. I was wondering though if I could figure out the SP losses of the ductwork using basic tables or Bill's spreadsheet and then assume the remaining SP loss was due to the cyclone body itself and the entry losses due to the resistance of air entry into the ductwork.

This is simply for my own amusement to see if I could estimate the SP loss for my cyclone body if I accounted for everything else I could think of.

Why? Because at times people will say a cyclone SP loss is in the 3-4.5" range and I'm wondering what they're talking about when I'm getting a reading of 2.6" with a chunk of ductwork attached in a running cyclone. As I mentioned, I designed this from the start with the intention of lowering the resistance to move more air...and maybe I did manage to get it quite low.

But then again, maybe that singular reading isn't indicative of the cyclone body SP loss at that airflow velocity (because it will vary with airspeed) for some reason.

Then my brain starts to hurt. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

FYI, that 0.9x estimate from Dwyer instead of a 16 point measurement is SOLELY for figuring out the velocity pressure. For measurements you place the opening of the pitot tube in the middle of the duct. BUT, the middle of the duct is where air is moving the fastest. It moves a little slower on the outside edges of the duct. Taking a 16 point measurement and averaging all the numbers will give you a more realistic velocity pressure value to calculate the average airflow in CFM.

An approximation is to multiply the reading of the velocity pressure in the middle of the duct with 0.9 and then take that new velocity pressure reading and then calculate the CFM.

BUT....this does not apply to SP. SP readings can be taken at any point in the duct. Middle, edge...it doesn't matter. That's the way SP behaves.

I verified all this stuff by moving the pitot tube around while watching the gauge. It all makes sense. That 1711cfm was calculated after I did my own averaging of velocity pressure readings.

Where's the aspirin? http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

Allan

[Bob, in Lachute, Qc.]

Allan,

By the way, you're producing 1.08 Brake Horsepower with that airflow. The motor's probably idling. You're not using your power efficiently, and you've got tons of reserve left.

I'm 100% convinced that if you reduce that blower inlet diameter to 7"-8", you'll utilise that capacity more efficiently. I'd bet that 7.5"inlet diameter, would be almost "spot on", and you'd be running at roughly 60% rated motor output. (3 BHP) You'd gain BOTH in cfm, AND SP capability.

"Cooooollll running's, Mon", Bob ;-))

[Bob, in Lachute, Qc.]

Allan, figuring out how much room you have left for ducting involves using a figure for cfm (1711, in your case).

You use the current flow of 1711 cfm, and get the velocity (4902 in your case). You compare that to existing tables, that you'll find at Airhandling.com, or Oneida.

If the tables show fixed velocities , like 4000 fpm, then you'll have to use the fan-laws, to calculate the SP.

Use that 4000FPM number, and ADD the difference which you have. Again, yours is 4900 fpm. Sooooo, the velocity ratio difference, is 1.225.

4900/4000 = 1.225

Square that number.

1.225x 1.225= 1.50"

So if the table shows 0.03" SP per foot length of new pipe, you'd multiply that 0.03(original SP per foot, at 4000 fpm), by 1.50

0.03 x 1.50 = 0.045"SP/ft.

So, 0.045"SP per foot of duct, or 0.45" per 10 foot length. All of that assumes you're still flowing that same initial 1711 cfm.

What of course happens is, the added resistance, will decrease airflow.

Naturally, if you had an already plotted fan curve, or system curve, you could go right to that point, to see the result ahead of time.

Since you don't have that, you'd have to calculate it, by applying the fan-laws.

Let's say you're looking at adding 30 feet of pipe. Well the resistance would be,

30 x 0.045= 1.35"

Now reduce air speed, by that ratio.
Divide 4900, by 1.35, and you get,

4,900/1.35 = 3,629.63 fpm.

In an 8" duct, that would translate to 1266.6 cfm. Sure hope I did that right.

Ohhhh, Gawdddddd , by brain hurts now toooo <;-))). Got smoke comin' out me ears, lol.

All the best, Bob

[Allan Johanson - South Su]

Back up a second there, Bob. You may need some more sleep. http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

At the moment I don't care about the effects of adding on more ductwork. That's easy to figure out and it'll be what it's going to be. No worries.

All I'm curious about today is how I can wrap my head around me measuring that 2.6" SP while flowing 1711cfm of air in my cyclone when Bill and others say a cyclone alone will typically require 3-4.5" of SP headroom. Bill and Don Beale spent a lot of time on that SP calculator and it's easy to use so when I plug in my numbers I get 0.99" SP for ductwork at the velocity of 4902fpm.

Where is the remaining 1.6" of SP loss going? Entry loss into the ductwork is part of it.

But is it right to say part of it is the cyclone body SP loss? If not, why not? If so, I guess I made a very efficient cyclone that is way less restrictive than "normal".

My poor brain... http://www.canadianwoodworking.com/forum/images/smilies/smile.gif

[Bob, in Lachute, Qc.]

Allan, 1 more thing.

The cyclone's resistance, is calculated from the original "free-air" blower rating. with that BIGGG 10" opening, you probaly already had a low SP number. Maybe 7.5"-8", buttttttt, a high cfm number. Let's put it at 7.5"

Welllll, if the cyclone's body added 4.0", you're now at 3.5" available SP. Add the filters and outlet resistance, and that might reduce it another .2" SP. You now have 3.3" available SP.

Adding that 30 feet equivalent of ducting, was roughly 1" SP, so you have 2.3" available SP left. Sounds right on. Whaddaya Tink??????

I yearn ferrrr fooood. Gonna go have supper, and a bottle of aspirins.;-)) Bob

ANOTHER "1 more thing",,,,,,Don't forget Allan, the SP value of the cyclone, is calculated from the original 7.5" available SP, at the free-air blower inlet. Since you chose to go with a more free-flowing system(more cfm), the resistance woulda gone up from Bill's calcs. You're blower inlet, is much larger than the cyclones intake. That's a multiple of 1.5625. Usually, it's ZERO. The net result severely increased entry-loss.

If the original free-air cfm, was 2500 cfm, well just the entry loss, is 6.184"

If free-air rating is 2000cfm, then the cyclone's entry-loss, is 3.958"

[Bob, in Lachute, Qc.]

Allan, the 1.6" SP, is the available "left-over" SP, after you add that ducting.

You're actual available sp, will be more though, that's because it will now be claculated at the reduced airflow, which resulted from adding your ducting. ;-)) Bob

[Ed/Leaside]

The drawing is to scale. I assume this is what you're suggesting, so that as SP increases the fan is less likely to chew on it's own exhaust?

BTW interesting suggestion about the ceramics. There's a pottery guild 9 units, less than 100 feet, down from here. Hate to think what would happen if it developed a craaaack. http://www.canadianwoodworking.com/forum/images/smilies/wink.gif



http://www.canadianwoodworking.com/chat/pics/pic133510.jpg

[Bob, in Lachute, Qc.]

Hi Ed,

Correct basic idea, but not quite what I had in mind. Here's a pic of one, at the inlet of a Cincinatti Fan airfoil blower. Mine is similar. Scroll down 'til you see "inlet collar" pic.

http://www.cincinnatifan.com/NEWPDFs/SQAFinternet.pdf

The "non-vible" inside edge, is nicely rolled, to reduce friction. I'd suggest that coming down from Allan's 10" blower intake, to 7.5", you'd have to exagerate the height of that unit, or rather, front-to-back depth. In effect, an aerodynamic "funnel", within the cyclone's "up-take" tube. Making it shallow, would create too wide of a surroundingn edge. 1.25" wide.

Once the desired reduction is achieved, then it flares back outward, inside the blower, toward the fan-wheel tips. I like where yours , terminates. Very much like mine.

As for the ceramic inlet-cone, I figure if the guy is smart enough to make one, he has the common sense to reinforce it properly, with mesh, imbedded in the ceramic. The ceramic would be ultra-smooth, and harder than steel. More abrasion resistant.

I'll know Monday, if I can simply buy one from Belfab. I'll post the details, when I know.

All the best, Bob

[Bob, in Lachute, Qc.]

Allan, you took your reading, and saw 2.6" SP, right???

So now you're adding ducting, equivalent to 1" sp.

The 1.6" "left-over" SP, is your left-over suction capacity. In otherwords, what's left over after adding the 1" sp of length.

Now, when you take your new reading, you'll see 1.6" SP, right???,,,,,,, NOT!!!!!!!!!!!

Why???????

It "WOULD" be 1.6" SP, "IF" the original cfm hadn't changed ; after adding that 1" SP of ducting, it dropped to a new level.

You're flowing less air now, and that will be the new reference point you're starting from, when you add MORE ducting.

Your new reading after adding that first original 1"SP of ducting, might now be something like 1275 cfm, AT 2.0" SP.

It has absolutely nothing to do with the resistance of your cyclone body. Zip,,,, Nadda.

To know your cyclone body's resistance, you'd have to start from the blower's free-air measurement.

;-)) Bob

[Allan Johanson - South Su]

Yeah....the blower's "free-air" stats are key here. I think it's all making sense in my congested pea-brain now. (I'm suffering from a nasty cold.)

BTW, that 2.6" SP was WITH the 9 feet of main duct. So the 1" SP loss in the main duct that was calculated is only part of it. Add on entry losses and it'll work out. In some ways if I think of it as vacuum (and how the vacuum would change depending on where a restriction was relative to the blower) then it makes things clearer.

I think the word "headroom" tends to hurt my brain in this situation because there isn't any headroom when you are trying to get the max airflow and that's the way I've been thinking. If all you want is 800cfm, then there is lots of "headroom" since this unit will easily deliver that.

Basically, with every inch of ducting I add onto the system, my 1711cfm @ 2.6" SP will change. The cfm will drop and the SP will rise.

Here are some more stats:

1711cfm @ 2.6" SP
1593cfm @ 3.0" SP
1543cfm @ 3.6" SP
1325cfm @ 4.6" SP
1082cfm @ 6.2" SP

It can fall off pretty fast if you have a crappy duct layout or if you size your ducts too small so the velocity ends up being too high, creating high SP losses.

I'm going to make my own SP calculator spreadsheet since I plan on using 7" branch ducts and Bill's spreadsheet doesn't handle that size.

Before I permanently mount the cyclone on its stand, I'll take it apart (since I made it so I can unbolt the cone from the upper cylinder) and mount that 8" main duct to the 10" cyclone outlet tube and take more measurements. I might also make a couple wooden donuts and pair it up to a length of 8" HVAC pipe and make an inner cyclone outlet tube that is 8" in diameter to match my main duct size and see if that gives me different numbers.

I'll keep you posted.

Allan

[Bob, in Lachute, Qc.]

Allan, what are those "stats" exactly??? Are those measurements/readings from adding pipe????

I think I screwed something up in my calcs. This staying up all night, to watch the Chinese Grand Prix, and being up 'til 5:00 am, doesn't help. I think I reversed some numbers earlier. I'll look at it in the morning, errrrrr, afternoon ;-)), it's 5:09 AM, Gawwwwdddd!!!! G'nite. Bob

[Allan Johanson - South Su]

I can't remember exactly which was which, but a couple might have been from adding a ton of flex hose and most were from obstructing the end of the duct by placing a piece of wood over it, partially cutting off the airflow.

http://www.woodsucker.com/testing.htm

You'll see in the pic at the above link what the woodsucker guy did with his piece of wood with a hole in it. I didn't bother with a piece of wood with a hole, I just stuck a rectangular piece of wood over the 8" duct opening. Maybe it isn't the "correct" thing to do (excessive turbulance???), but maybe it's OK?

In any case, that's what I did to reduce the airflow to get some more numbers, many months ago.

Cheers,

Allan

[Bob, in Lachute, Qc.]

Good Morning Allan.

Welll, I woke up not too long ago, and , it took me about 6 or 7 minutes, to sort out which sock, goes on which foot. Thennn, I realised "it doesn't matter". THAT was a GOOD sign. Butttt, it went downhill from there. My next dilema, was "Which end of the sock, do I put my foot in???"HMMMMM.

I sat in front of my PC, enjoying my freshly ground coffee, and surfed a bit, trying to get some info on SP. NOT easy. I gave up.

I re-crunched some numbers, and while the calculator is pretty decisive with the answers, I on the other-hand, am not ;-)).

I would CAREFULLY weigh ANY responses you get from me today, and assume TOTAL UNRELIABITY.

I CRAVE R.E.M. SLEEP !!!!!

Mebbe after a li'l "Nappy-Poo", it'll get better ;-))

All the best, Bob