Shop Vac Overpowers Cyclone Separator

[Joe7]

I have two cyclone separator/shop vacuum combinations working in my garage wood shop.  Why two?  I added thesecond separator set-up rather than run vacuum piping to serve all tools - wanted to avoid piping, blast gates, etc.  I have a table saw and a router table running on one and a stationary belt sander, drill press, and small jointer feeding the other.  The first is a 2HP Genie and the second is a 4.5HP Shop Vac; both have 2" hose running from tool to cyclone port and from cyclone to vacuum.  The older Genie set-up passes virtually nothing to the vacuum (99.9% gets collected in the bucket under that cyclone.)  My new Shop Vac system is constructed exactly the same, however, the vast majority of waste is collected in the drum of the Shop Vac and very little if any is trapped in the bucket under the cyclone.  The only thing I can see that's different is the power of the Shop Vac over the Genie.  Did I put too much vacuum on the second system?  Is that why it "saves" to the vacuum instead of the separator?

[gee-dub]

You can definitely overpower some separators.  I run a couple of 6.5HP Ridgid vacs with Dust Deputy separators without issue.  The "trash can lid" type (5 gallon bucket size) would get overrun by the large vacs and I had to vent the vac ahead of the separator.  That cost me vacuum power so I upgraded the separator.

[drzaius]

Couple of possibilities.

Check for leaks in the seal between the cyclone & the bucket. Even a small one can drastically increase the amount of stuff getting through.

A cyclone needs lots of velocity to separate well, so if there is too much restriction from hoses, fittings or a clogged filter, efficiency will fall off.

[Joe7]

Thanks!  I've obviously overpowered things.  Drzaius. I am using a thin layer of foam padding between bucket and plywood lid and I clamp the whole thing down to the lip of a 5-gallon plastic bucket with threaded J hooks and wing nuts for a tight seal.  I should have seen the problem when I sucked in the sides of my plastic bucket - too much suction.  How do I remedy the situation?  Should I run piping and blast gates so the whole shop flows through just one vacuum? (probably the larger one to maintain suction strength)  Since I have two cyclone/bucket constructs, would there be any advantage to running the flow through both of them?!?  I'm thinking out loud here that by doing so, if I still have too much suction, I could tweak one or more of the blast gates a hair to vent ahead of the separator like gee-dub.

[drzaius]

Leaving everything else exactly the same, try swapping the vacuums & see if there is a difference.

[Joe7]

Drzaius - thanks again.  Your suggestion made it clear that I have way too much suction for the cyclone - great dust and chip removal, but suction is so strong, it doesn't allow cyclone to spin the air slow enough for debris to fall out and into my bucket.  I guess I need to run piping with blast gates; the gates will allow me to control the air flow to each tool, but I don't think it will reduce air flow through the cyclone (which is apparently the problem.)  I even thought of connecting both cyclones in series upstream of the vacuum, but I don't think that will sufficiently slow air flow to permit separation.   What about a blast gate right before the air line enters the vacuum?  Do you think that might solve my cyclone 'problem' at the expense of overworking the vacuum?  Perhaps (even with piping and blast gates) I will have to use the 2HP vacuum instead of my 4.5HP vacuum with piping/hoses to each tool.  Thanks for letting me pick your brains - any ideas spring to mind?

[drzaius]

Something doesn't make sense to me. I've always understood the higher velocity through the cyclone makes for better separation. I've never seen this happen with my Ridged vac & Dust Deputy, even with very short hoses & a new filter. If the dust isn't dumping in the cyclone, then that indicates a leak at the bucket

[gee-dub]

What are you using for a separator?  The Dust Deputy does fine with the high power vac.  Can you post a pic?  If you want to go the route that reduces your performance in order to make your current separators work you can drill a hole at the connecting point of the separator and use something like this to vary the bleed till you find the optimum balance.  You an also make your own with a section of PVC pipe.

This is the type that I found easy to overrun with the large Ridgid vac. 

The airspeed through the bucket was too fast and the chips wouldn't fall out of the air stream.  I tried extending the exit tube but, never really found a sweet spot where separation was good and capacity wasn't compromised.  Also, if your bucket is collapsing, get a better bucket. ;-)

[Cheeset202]

I am struggling with your logic that the shop vac is overpowering your cyclone.  Plenty of people use the dust deputy (if that's what your using) on much larger DC systems than your shop vac so something else is going on.  Some pics of your system would help.  The shop vac is definitely not going to work with hard piping and blast gates, nowhere near enough cfm and fpm for that!

[wtnhighlander]

13 minutes ago, drzaius said:

Something doesn't make sense to me. I've always understood the higher velocity through the cyclone makes for better separation. I've never seen this happen with my Ridged vac & Dust Deputy, even with very short hoses & a new filter. If the dust isn't dumping in the cyclone, then that indicates a leak at the bucket

The idea is that the cyclone reduces velocity so that particles fall out the bottom, but it only reduces a percentage of the incoming air stream's velocity.  If the air stream is fast enough initially, the cyclone can't slow it enough to drop the particles. 

[Tpt life]

Oh boy, this is deeper than maybe can be easily understood. The center of any spinning system barely moves. Think the eye of a hurricane. The outside can be moving rapidly, and in fact that outside velocity in a closed system will push material to the center of flow where it is moving more slowly. We see this also on rivers in a way, where most items are pushed to the edge where drag slows things down. That is slightly problematic as rivers are reversed of cyclones. They have lineal flow instead of circular flow. They reflect more of what happens in your collection pipes and what actually causes the problem that the cyclone is designed to correct. The cyclone directs the air to be faster around the edges and more stagnant in the middle. Both prior comments hint at different parts of that equation.  Typing on a phone while riding. Hope this is coherent. 

[Just Bob]

44 minutes ago, Joe7 said:

Your suggestion made it clear that I have way too much suction for the cyclone - great dust and chip removal, but suction is so strong, it doesn't allow cyclone to spin the air slow enough for debris to fall out and into my bucket.

I run a dust deputy with a central vac that is rated for a 4000sq ft house and have no issues.  In fact I haven't changed the vac filter in over a year.  I think there is something else going on.  Looking on Oneida's web page they say this:

Sealed Air Tight - If there are any cracks or leaks present in the drum (or anywhere else in your custom assembly) this can create a backdraft that will significantly reduce the cyclone's ability to separate material(s).

I do run mine through 1.5 inch duct with blast gates and the system is limited to my miter saw, router table, sanders etc.. saves a ton of space and for me is much more convenient than a shop vac "puppy dog" following me around the shop.  I would double check everything before you condemn the shop vac.

 

[andrew-in-austin]

You are not overpowering anything.  You have a leak somewhere in your cyclone and/or container below it.  It has to be perfectly sealed.  FWIW, the HP ratings for shop vacs is 100% BS.  If you want to know the power of a vacuum, look for the "airwatts" value.

[Joe7]

Thanks everyone - good insights all.  I went back to each connection and made sure all seals were tight.  Did a test run on some floor sweepings; got more than I expected inside vacuum, but significantly less than before, so snugging everything up has helped (and possibly provided a clue as to my 'problem.')  I attached some photos.  Vacuum "A" is a 2HP Genie that has hose connections to my table saw and router table.  Vacuum "B" is a 4.5HP Shop Vac with hoses to my sanding station and jointer (and occasionally a chop saw.)  I have carpet padding cut to fit on top of bucket "A" and foam rubber cut for bucket "B;" it is " B" that is giving me problems.  I did notice better 'action' inside cyclone "B" after I snugged everything, so maybe it is a simple matter of having poor seals at connections like Andrew and Bob suggested.  Since I move hoses to different tools on occasion, all my connections are a very tight friction fit; I am going to seal the connections better in the event a tight friction fit is not good enough.

[drzaius]

That looks like open cell foam, which won't be giving you a perfect seal as air can pass through it. Try using some wide closed cell weather stripping & have more attachment bolts, like 6 instead of 3.

And there is no hole cut in the foam for the dust to fall through. What's with that?

[Cheeset202]

Totally confused with foam at the bottom of the dust deputy?

[Marmotjr]

3 minutes ago, Cheeset202 said:

Totally confused with foam at the bottom of the dust deputy?

I think it was for a test, but yes, I too am confused.

I am speaking from my experiences in a sand blasting shop here, but it was a 3 story tall, cyclone separator/sorter, that I was often stuck trouble shooting when it went bad, which was often (it was old). 

If you have a leak below the cyclone, it allows air into the cyclone, causing "lift" on the debris you want to fall into the lower section.  We would usually have at this point a controllable flue in the lower hopper that would allow us to regulate exactly what size particle was lifted into the next section along the suction chain, or would drop into the vibration sorter.  With no air flow (leak) at all, every particle should drop down into the hopper.  Wide open, only big chunks would fall down.  

Wood particles are much lighter (well, less dense) and have a much greater surface area for air flows to act upon.  So if you have even a small leak somewhere in the hopper (from the base of the cyclone to the bottom of the bucket), the wood particles are far more likely to get lofted into the shop vac.  I think you ran a test with the smaller shop vac, and did not see anything.  The stronger shop vac may be able to pull air through a small leak where the smaller one cannot. 

If you are using that foam to seal the lower bucket, I would switch to something more air tight.   The bigger shop vac is probably able to pull air through that.   

Leaks other places in your system should have no affect on the performance of the cyclone, they'll just reduce your overall suction. 

[bleedinblue]

Not to sound condescending at all, but this is the internet...  Just to be sure, I think we need confirmation that the foam is not placed at the bottom of the dust deputy when in use before any more troubleshooting is done...

[drzaius]

12 hours ago, bleedinblue said:

Not to sound condescending at all, but this is the internet...  Just to be sure, I think we need confirmation that the foam is not placed at the bottom of the dust deputy when in use before any more troubleshooting is done...

Ya, that is what I'm questioning. The photo seems to show the foam blocking the hole in the bottom of the DD from the bucket.

[Joe7]

LOL!!!  In my haste, I attached the wrong photo and you guys caught me!  I took a series of pics to use in a tutorial and the step right after "cover with foam for seal" is "now, cut a discharge hole in the center of the foam"  No wonder it looked fishy!  I've attached the "real" photo here.

[Minnesota Steve]

That looks like open cell foam, and so it's going to be pulling air in from the underside of the cyclone which won't work.

Also the discharge hole through the plywood has to be exactly the diameter of the cyclone if not slightly larger.   Otherwise it blocks the dust from exiting out the bottom, and it'll get sucked back in.

 

[Joe7]

Thanks, Steve - good points.  The photos don't show it but diameter of cyclone discharge port is exactly matched by plywood I mounted it on.  Silicone liberally spread to all joined surfaces before screwing into position.  I'll try a different seal than the foam; I would have thought by tightening the plywood onto the foam against the rim of the bucket (very tight) would have compressed the foam into a nice seal.  I want to eliminate all the possible air leaks, so I'll try an alternate to the foam - any recommendations?  (I used a piece of carpet padding on the other cyclone and it is working well, but you may have a better material in mind.)

[gee-dub]

I have a suggestion.  You want a closed cell foam or rubber product.  Now, having said that I use the bucket an lid that came with the DD which has no additional seal, just the snap-fit function and all is well.  I actually ditched the vacuum barrel.  I moved the blower and filter to a small box that collects about a teaspoon of spoil every 6 months or so.

This is the prototype that worked so well it has never yet made it to version 2.  I did reinforce the underside of the bucket lid wit a disc of plywood to make it more resistant to sucking down.  Other than that is it stock.

[Marmotjr]

That's a leaf blower......

 

Love it. 

[Tpt life]

I like paint buckets with built in o rings.