Poor chip extraction/Turbulence in ducting

T

Tom Grezek

New member
Any chance my setup could have vortex/turbulence within the ducting causing poor extraction?

I first tested the system using some small blocks (1"x0.5") and noticed they rattle around in the pipes for a long time. Some wouldn't flow through until I shut down the system. It seems like there is turbulence at full power causing a dead spot in the ducting, that changes when the blower speed reduces during power down.

I hooked up my Hammer A3/31 Planer/Jointer with disappointing results in chip extraction. About 1/3 of the chips seem to end up on the floor and on top of the material being cut, which presses the chips into the material being planed.

Here's my setup:

The Planer/Jointer has a 120mm (4.75") port connected to a same sized flex host about 10 feet long, which connects to Nordfab 6" ducting that goes straight up through the ceiling to a 45, then into a Nordfab ridged flex hose with a very slight curve, then into the CV 1800 dust collector. My total ducting run is about 25 feet with 13 feet being vertical from the shop floor up to the attic.

I also notice when I power down that a pile of dust will suddenly flow from the ducting into the cyclone about 5 seconds after hitting the off button. Again-it seams as if the dust is getting stuck in a "dead spot" at full power, which then changes when the blower powers down.

Let me know if you have any thoughts ideas.
 
My guess is that your connection to the jointer/planner is too small. You should have a 6 inch line to the machine. If you can't make the dust port on the machine 6 inches, then try two 4 inch ports.

I'm sure other members can give you the static pressure drop calculations, but I'm more of an experimental physicist: if the chips aren't flowing then the pipe is too small. You need more volume of air flowing to move the debris. The CV is powerful enough to move a 25 foot tape measure along 6 inch piping. If you go to the Wood Whisperer website, he has a video of his CV install. At the end Marc connects it to his 8 inch jointer and extracts wood chips from boards he machined several years before. It is just a demonstration that lots of air volume will move packed in chips and debris.

Good Luck!
 
Thanks for the input Mark.

Here's a little more info to help with ideas:

I seem to have the same "turbulence" in the ducting without any machines hooked up. I've sucked up small wood blocks and they'll bounce around in the ducting until I turn it off. Then they get sucked into the CV and drop into the dust bin.

Would my 120mm (4.75") port size on the planer/jointer influence the delayed flow of chips I see when the unit powers down? I probably didn't go a good job of explaining in my original post, but when I turn the CV 1800 off, a puff of material will flow from the ducting into the cyclone after it's slowed to about 75% of full speed, which leads me to think there's an airflow change that allows the rest of the dust to get sucked into the CV vs. hanging out in some dead space within the ducting. I'm not disconnecting from the Planer/Jointer, so any airflow influences (restrictions) should still be there.

Doesn't the Marc (Wood Whisperer) have the Powermatic planer with 4" ports?
 
Are you suffering from starvation with just that one port open, i.e. can you crack open a second port somewhere and get better flow and dust collection overall?
 
I'm thinking in that direction too, but right now, I only have 1 run of ducting, so there are no other ports to open. Also, when I have no machines hooked up, I've sucked small blocks of wood into the open 6" Nordfab ducting (about 10 feet of ducting attached to the CV) and the wood will knock around until I shut down the CV. Then it gets sucked in and drops to the bottom as the CV slows down to a stop. The only way to get less restriction would be to go larger ducting.

There's a 45 degree coupler just above the vertical ducting that goes into a 6" Nordfab rigid flex pipe that's 5' in length, then into the CV. I'm thinking the vortex is somewhere in the 45 & flex pipe area.
 
My suspicions are that you are losing performance due to leaks in the system -- in particular at the bin below the cyclone. Many installations find out the hard way that leaks into the bin reduce the efficiency of removal and reduce the airflow through the system. What type of bin and connection to it are you using?

Also examine the outlet side of your blower and the filters (if you are using them) to see if dust and chips have bypassed the cyclone into the output stream (if you block the blower outlet with clogged filters, you may only see the problem in drastic reduction of the performance upstream of the cyclone as you are now seeing). My suggestion is to check the bin thoroughly first (use a smoke stick or fine tissue paper up against any seams and the top). Then if it checks out to be leak free, disconnect the filters and check that they are not packed with dust and chips (if clogged, it is usually the result of a severe bin overflow or a leaky bin).

Next step if all is clear is to disconnect the filters and see if you have the same issues. I would be surprised if you don't have good performance at that point -- if it still is problematic, check your motor connections to insure your impeller is not turning the wrong direction as that would cause your problem as well. A basic CV1800 with decent ductwork can suck the chrome off a bumper hitch! Let us know your outcome of these tests.

Hope this helps.
 
Is your impeller spinning in the right direction? That'd be my guess based on the "it improves once I shut down" symptom.

Oops, sorry, just saw McRabbet's post once I clicked "Post". He recommends the same check.
 
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I concur - either you have massive leaks in your system or the impeller is spinning in the wrong direction. My unit didn't have a rotation sticker, so it took me a long time to figure out what counter clock wise rotation meant when assembled. Basically the impeller should be spinning right to left.

Look at my previous posts when I noted that I could not close the doors to my sound isolation closet due to insufficient exhaust pathways out of the closet. I weigh 300 pounds and could not force the doors closed, that is how much air pressure is generated by the CV 1800.

You were correct when you pointed out that Marc the Wood Whisperer had a 4 inch line to his jointer. However, his system works and delivers massive air flow.

It may have been McRabbet that calculated for me that the CV 1800 is trying to expel 50 square inches of air when properly set up. A 6 inch trunk line only has a cross section of 28.26 square inches, so your system should be roaring. Not only is that chrome coming off the trailer hitch, you should be worried about the entire frame being sucked into the pipe works.

Good Luck!
 
I've only seen one style of cyclone body, but I don't think we can say the impeller is spinning in a certain direction, because we don't know which style of cyclone body he has - I'm guessing the impeller if wired correctly will spin one direction for the "left-exit" style, and the opposite direction for the "right-exit" style.

Basically Tom, the impeller is "back-handing" the air in that the blades actually curve away from their path of rotation. They should not be "scooping" the air because that would cause the air flow to rush into the center of the impeller, instead of away from it.

The blades should be pulling the air up and shoving it out in such a way that the air rushes around the perimeter of the impeller housing and has a straight shot out the "exit", without having to make any turns to get out.
 
I am equally certain that the design of the impeller is such that it can only spin in one direction to work correctly. The impeller is a backward inclined design, so it has to spin in a counter clock wise direction. How the air exits the cyclone is not relevant to this issue. The air doesn't know how it got there, it only knows it has to leave.

The exit ramp can be turned in any direction to accommodate the installation in a particular shop, so it is doubtful this could account for a difference.
 
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It could be, the LH and RH cyclone bodies may only differ at the inlet, and the outlet may be identical on both. As I said, I've only see the body style I ordered.
 
I'm in the same boat, effectively. I have a Felder jointer/planer with a 120mm to 6" reducer on it to ~6' of 6" flex. My 6" flex runs into ducting and takes 1 90 degree turn into a wye and then 25' of 6" into the cyclone. I do have 1' of flex into the input of the cyclone as I couldn't hit the input with the pvc. I don't believe even with the "small" inefficiencies I have above that would account for how poorly my setup works.

I couldn't pickup a small wooden block with my suction on a bet. My system runs well enough to extract the planer, fill the 35gal fiber barrel and then clog the filters solid with chips. But the suction vacuum at the machine is terrible. If that makes any sense. I'm seriously frustrated with my setup and need to hire some onsite vacuum consulting to fix this!
 
Wow that is terrible.

Is it possible that the 1 foot of flex tubing is causing turbulence? There is flex tubing that is smooth on the inside. You can heat solid PVC pipe to bend it. You can get metal flex tube that that is smooth on the inside as well. See the Woodwhisper's website. He has a video of a CV installation in his shop and they had to use flex metal tubing to make the connection from the trunk line to the intake.

Based on everything I've read and the posts of others you want the four or five feet before the intake ramp to be as straight and smooth as possible.

Chips and shavings in the filters is sign of a real problem. Do you have a leak in your cyclone connections?

Hope you can resolve the issue.
 
So after some more diagnosis I found an obstruction, small, but it has helped.

My main line runs under the floor and I wye off of that and come up into vertical "pedestals" for the jointer/planer, TS, mitre station, bandsaw. The only major drawback I find with the under the floor main is my natural hesitation to lift the panels and inspect the areas for problems. Major PIA.

Anyway, my suction is still not likely going to pull a block of wood off my palm but I'm clearing the lines fine now after removing the debris.
 
tdenap,
Something is very wrong. The cv1800 will yank a 25 foot tape measure off your palm if near an inlet. If you put your hand near an inlet it will pull quite hard. I encourage you to post pictures so people on this site can help you. One thing you can do is to check the rotation of the fan to make sure it is correct.
bababrown
 
I concur - there is something wrong with the either the rotation of the fan or you are starving the system of air. Starving could be in the pipe system on the inlet side or the outlet side in the filters. If air can't get out, it can't get in.

You can look at my picture file in the Gallery. The table saw connection is a huge U shape and there is no reduction in the drawing power of the CV. Sounds like your piping system is much more efficient than mine, yet mine will pull the tape measure from the table saw to cyclone without any problem.

If you have no elbows under the floor, then debris has to be a sign of low air volume. Rotation of the fan or multiple openings in your piping are the only plausible explanations.
 
tdenap,

Since you installed a Clearvue in 2012, I wonder whether the poor performance problem might be the result of a recent change you have made to the system, including the duct work. If a change has been made to the system then perhaps the change has affected performance.

You also mentioned sucking chips from the planer into the filters. If the filters have become clogged with chips and the filters were not subsequently cleaned well, then air cannot be pulled into the system because it has nowhere to exhaust due to dirty filters. Even if the chips were cleared away, a system operating since 2012 could easily have clogged filters that need back flushed with compressed air. A reliable check of the filters is to remove the filters, turn on the cyclone and check the suction. Improved suction means the filters are the problem.

If none of this seems to apply, the only other idea is to try to isolate the problem to either the duct work or the cyclone. With the cyclone on, check the suction at a machine dust collection port to get some sense of the suction. Then disconnect the duct work from the cyclone and check the suction at the cyclone inlet. If the suction at the inlet is quite a bit stronger than at the machine dust collection port, then the problem is in the duct work. If the cyclone has about the same suction as at the machine duct collection port, the problem is in the cyclone.
 
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