Cyclone Issue Solved

[Bill Adamsen]

I'd experienced an issue jointing wider Eastern white pine boards, where the shavings would get caught up in the throat of the cyclone and clog it without ever setting off the alarm. A change to the flexible ductwork may have actually solved the problem quite by chance. My flexible ducting was about eight or nine inches longer than it needed to be, and this caused a problem pulling out and emptying the drum of shavings/sawdust by "pressing down" on it like a spring. It was annoying and I decided to shorten the flex to a length that actually "lifted" the top off the drum to make changing easier. An unexpected benefit was that the shavings stopped clogging the cyclone (I was in the middle of a lot of jointing with EWP). It seems that the twist on the flex functions like a screw to work the shavings down into the drum ... stretching it made the thread more aggressive, and moved the shavings down faster. Would never have guessed.


https://www.youtube.com/watch?v=1wQL0lPdtd4

[Robert Payne]

Bill,

Looking at your video, it appears to me that the sawdust and chips are being held up by air coming up from the bin -- I suspect you may have a leak in the galvanized barrel that is allowing air to get in. My experience is that these cans can leak at their handles, the base and the lid unless thoroughly sealed. Check for air leaking in using an incense stick or (heaven forbid) a lit cigarette. Any smoke going into the bin will locate a leak. Given the behavior you are seeing now, you are probably getting significant bypass of dust into your filters unless you fix this issue.

Your point about the length of the flex is well taken -- it points out how much surface friction is present in un-stretched flex. A good example why users should avoid much of it in their duct work layouts.

[Michael W. Clark]

+1 on the possible leak in the drum or hose causing the material to swirl and not drop. In addition to incense or smoke tubes, you can also use a piece of tissue paper. Hold it close to the suspicious leak points and it will be sucked up to the leak.

[Bill Adamsen]

Robert:

Good point. I'm not sure I considered that the cyclone (and waste barrel) is under vacuum. I wrapped the cardboard barrel in plastic (a single plastic bag) and taped off any possible openings with duct tape. When I turned on the vacuum indeed the plastic did compress (as the photo shows) much as a vacuum bag for composite work would compress. But as the video shows, I'm not sure there is much difference in the flow of material out of the cyclone, perhaps a bit more efficient. The take-away is that I'll get a seamless plastic barrel. Thanks for the feedback!



https://www.youtube.com/watch?v=RHpio6Un1O8

[Peter Quinn]

I have a fiber barrel I intended to use as a component of a DC system, often wondered if they were porous to any extent? I wonder if you could improve performance by sealing the barrel with a coat or two of finish? The ring lock on mine from onieda has a gasket, seems to seal pretty well though I've never tested it under vacuum. I know the galvanized barrels we use at work develope leaks and performance suffers greatly when they do. The bypass hits the filters and clogs up the works quick, then the general level of performance drops until the cartdridge filters are cleaned out.

[Bill Adamsen]

I see 55 and 77 gallon poly drums, and I'll move in that direction. I spent significant time carefully sealing leaks in the pipe ... yet completely missed the leaks between cyclone and drum.

[Robert Engel]

I used a Brute trash can and stapled a bicycle inner tube on the top lip.
Works great.

One thing, you don't want upward pressure on the lid you want it pushing down a little.

[Jim Andrew]

Mine is a plastic drum, and a steel lid, but with no ring to hold the top tight, so I put foam weatherstrip on the drum, and use spring clamps to hold the lid down. My chips fall faster than your second video, so must be working very well. I place a trouble light on the lid when I am planing, so I can see the hose for when it fills. The first video really does show your chips floating and not settling down in your drum. Thanks for posting the videos.

[Mike Chalmers]

Bill,

Looking at your video, it appears to me that the sawdust and chips are being held up by air coming up from the bin -- I suspect you may have a leak in the galvanized barrel that is allowing air to get in. My experience is that these cans can leak at their handles, the base and the lid unless thoroughly sealed. Check for air leaking in using an incense stick or (heaven forbid) a lit cigarette. Any smoke going into the bin will locate a leak. Given the behavior you are seeing now, you are probably getting significant bypass of dust into your filters unless you fix this issue.

Surely if you have a bag in the barrel with the top turned over the lid, any leakage from the barrel itself would b contained?

[Robert Payne]

Actually, if air is leaking into the barrel, the bag inserted into the barrel will collapse. In my initial post above, I did not realize the OP was using a fiber drum with a metal top -- they can leak too. My preference is a heavy Polyethylene food barrel with a lid made of either 3/4" MDF or plywood and a groove cut with a router corresponding to the barrel lip and neoprene weather stripping glued into the groove -- no leaks and easy to make. The inlet is sized for the flexible duct below the cyclone and a metal started collar secured to the top and sealed with silicone caulk. A catch bag in the barrel can facilitate dust/chip removal (by heavy duty ones!).
Surely if you have a bag in the barrel with the top turned over the lid, any leakage from the barrel itself would b contained?

[Bill Adamsen]

Robert and Mike. I've done a fair amount of vacuum bagging, so the moment Robert suggest "the leaking barrel," I decided to wrap the barrel with plastic (a bag) to test the theory. Sure enough, as you can see in the photo above, the plastic bag has tightly conformed to the cardboard barrel. It's not unlike what a vacuum veneering bag looks like when compressing a veneer of composite. It indicates that there is a leak somewhere in the barrel or barrel fittings.

From my experience with vacuum bagging, I can tell you that any time you have a setup requiring sealing tape, it can be extremely challenging to stop the leaks. While I believe the barrel is leaking in a multitude of places, even a single leak in the wrong place will create the vacuum effect we're seeing with the bag over the barrel. So a bag inside the barrel would require the area between bag and barrel to have much smaller leak than anywhere else, or else the bag could end up inside the cyclone chamber. Does anyone successfully put a bag inside their cyclone?

[Mike Chalmers]

Robert and Mike. I've done a fair amount of vacuum bagging, so the moment Robert suggest "the leaking barrel," I decided to wrap the barrel with plastic (a bag) to test the theory. Sure enough, as you can see in the photo above, the plastic bag has tightly conformed to the cardboard barrel. It's not unlike what a vacuum veneering bag looks like when compressing a veneer of composite. It indicates that there is a leak somewhere in the barrel or barrel fittings.

From my experience with vacuum bagging, I can tell you that any time you have a setup requiring sealing tape, it can be extremely challenging to stop the leaks. While I believe the barrel is leaking in a multitude of places, even a single leak in the wrong place will create the vacuum effect we're seeing with the bag over the barrel. So a bag inside the barrel would require the area between bag and barrel to have much smaller leak than anywhere else, or else the bag could end up inside the cyclone chamber. Does anyone successfully put a bag inside their cyclone?

Lots of folks have bags in the barrels under their cyclones. Some machines have a separate hose from the cyclone to the barrel to create negative pressure between the barrel and the bag to keep it in place. Most, including mine, use some sort of retention set up. Mine came with a cage you put inside the bag. I have also wrapped the cage with a piece of corrugated plastic to keep the bg from trying to get through the holes in the cage.

So, if you have a bag such as I have described, any leaks would cause the bag to try harder to get into the cyclone, they shouldn't affect the cyclone itself.

[Anthony Whitesell]

Robert:

Good point. I'm not sure I considered that the cyclone (and waste barrel) is under vacuum. I wrapped the cardboard barrel in plastic (a single plastic bag) and taped off any possible openings with duct tape. When I turned on the vacuum indeed the plastic did compress (as the photo shows) much as a vacuum bag for composite work would compress. But as the video shows, I'm not sure there is much difference in the flow of material out of the cyclone, perhaps a bit more efficient. The take-away is that I'll get a seamless plastic barrel. Thanks for the feedback!


We should remember this for later. The plastic bag on the outside of the drum is a great idea for checking for leaks. Very visual.

[Rick Potter]

I am with Mike,

My Onieda has a fiber drum, but I really don't know if it leaks. It has always lifted the drum off the ground until it gets some sawdust weight in it. When I put the plastic bag in the drum it still acts the same, picking up the whole drum a bit when empty.

The home made bag holder I pictured in a thread about hold downs a few days ago works just fine to keep the bag from getting sucked up. No problems. Of course a couple coats of finish on the inside should seal it up anyway.

[Martin Wasner]

They need to make mini rotary air locks, then you don't have to worry about sealing the drums.

[Michael W. Clark]

They need to make mini rotary air locks, then you don't have to worry about sealing the drums.

I hear you and you are correct, but you need a good airlock to be effective. The smallest ones I know of are 6" and cost as much or more than a upper-end hobby cyclone system. They are intended for industrial applications. In addition, you have the controls, power, and extra headroom to accommodate the airlock.

Just my opinion, but for a fraction of the cost, you can have a metal drum and good sealing lid with level sensor. This is the route taken on most single cyclone installs that discharge into a container. Sometimes there are other reasons the mandate the use of an airlock.
Mike

[Chris Parks]

Put a packer under the drum to lift it and then shorten the flex hose to prevent the material stalling in it.

[Martin Wasner]

I hear you and you are correct, but you need a good airlock to be effective. The smallest ones I know of are 6" and cost as much or more than a upper-end hobby cyclone system. They are intended for industrial applications. In addition, you have the controls, power, and extra headroom to accommodate the airlock.

Just my opinion, but for a fraction of the cost, you can have a metal drum and good sealing lid with level sensor. This is the route taken on most single cyclone installs that discharge into a container. Sometimes there are other reasons the mandate the use of an airlock.
Mike


That's why I said a mini one. You have to be moving a fair amount of material to justify even a small one from Oneida. I think their little guy is a .25hp, and it'll fill a 55 gallon drum in less than ten minutes. Spendy too. I just looked at their website, $2400. I sure wish I had one dust collector, sitting outside, and dropping dust into a dumpster or dump trailer. Emptying bags or drums is a royal pain, not to mention messy if you aren't careful. Not matter what, I still end up having to empty something into the dumpster, and it's always windy.


I think all of the air locks I've looked at, rotate on a horizontal axis and look like they have paddles. I wonder if having a pair of discs, mounted on the same shaft, rotating on a vertical axis with holes that are offset would work on a small scale? The shaft would be off center of the cyclone. Maybe sealing them is a nightmare, and that's why I haven't seen that design? Or, maybe it is done that way, and I just haven't noticed one yet. The vertical profile of it could be pretty darn small. Just a few inches between the discs would work I'd think. I would think you could make one pretty easily. A pair of uhmw discs so it's slippery, with them sandwiched between a high density foam for a seal. I'm picturing cutting up the foam mats that dovetail together on the edges for a home made one. There would have to be something to keep chips from going into the seal too. Some sort of lip, or a pair of lips that would prevent chips from working their way in. It'd take a heck of a slow motor, and quite a bit of gearing or pulleys to get the RPM down low enough though.

[Michael Weber]

Between the two videos I notice there is a big time difference between the time it takes for the shavings to clear the tubing after the board exits the planner. Its over 10 seconds in the first one and only a couple in the second. Both videos take the same 2 seconds for the shavings to appear after the wood hits the planner. Not sure that means anything and might be due to the lower volume in the second video. Just interesting to me.

[Michael W. Clark]

That's why I said a mini one. You have to be moving a fair amount of material to justify even a small one from Oneida. I think their little guy is a .25hp, and it'll fill a 55 gallon drum in less than ten minutes. Spendy too. I just looked at their website, $2400.

That's a fabricated airlock. You want cast iron with the housing and rotor machined for a tight sliding fit. If the airlock doesn't seal, it doesn't serve the purpose.

Meyer makes good quality air locks. There are others too, but that is the style I'm referring to.

[Martin Wasner]

Still $1700 and will move two cubic feet per minute on a 6".

[Michael W. Clark]

Still $1700 and will move two cubic feet per minute on a 6".

That is a high volume for a 6" feeder. If you turn a feeder too fast, you will create a fan effect (pump air back into the cyclone) and cause problems too. A 6" will generally handle less than half of that volume. The volume of material will be less than that because you will not get 100% fill on the pockets. You want a very low fill factor if you are handling planer shavings.

Even though a 6" will more than handle what a small system will typically produce, the pockets are small. I would be hesitant to use a 6" if you have a planer/jointer on the system. If the shavings hang up, it keeps other material out and you plug the cyclone.

I would estimate a good quality 6" airlock to be $3500+ retail price. An 8" is not that much more, but you get over twice the volume per revolution.

This is why I said for a single cyclone, you are better off spending the money on a good drum and seal kit and you save the height too. Airlocks are good when you have combustible dust (yes, wood dust is combustible quite often), discharging into another device that cannot be sealed, or you cannot shutdown to empty the drum (you can use two drums for this case sometimes with a diverter or slide gates).

Edit to remove references to Oneida.