In-Line Passive Cyclone?

[Ben Mitchell]

Howdy!

I'm setting up my new shop, and as part of that I'm installing permanent ducting to my wood tools with a substantial DC system in a shed outside for noise reduction (return air system is "open the window" - I'm in California :-)

I found a too-good-to-pass-up deal on a used Dust-Hog SC3400 collector, and so it's now sitting on a pallet in the middle of the shop floor waiting for the shed to be built. This is a 7.5HP unit that pulls 3400CFM under ideal circumstances.

The SC3400 comes in several configurations for storing the collected material including: (1) A couple of little drawers in the base of the cabinet, or (2) a hopper system that directs material into a collection drum, or (3) a bin-vent option that will dump material into an outboard collection bin. Unfortunately, my unit is configured per (1) above with some small drawers. This is fine for sanders, chop saws and other tools that produce relatively small amounts of material, but my planer would overwhelm the drawers in a matter of minutes.

This leads to my question:

What's the word on putting a passive, in-line cyclone in the system that captures the big chips before they make it into the DC?

I'm thinking I could then run an 8" duct through the wall and split it in two branches, one that goes through the cyclone and then on to the chip-producing tools, and another that bypasses the cyclone and goes to the dust-producing ones.

All of the two stage systems I've seen power the cyclone and then force the exhaust through secondary filtration. Would it work to just buy a ClearVue cyclone body (which they sell as a standalone thing) and instead of putting a blower on top just duct it to a DC that pulls through it?

Thoughts?

Thanks,
-Ben

[Carl Kona]

Ben,

Sounds like a monster! If I understand that model, it is simply a very large single stage dust collector. So an inline separator would definitely be beneficial. You are basically talking about a super dust deputy type of setup that many people have. The only issue I would be concerned about is too much suction for the size of the separator. You will likely be fine with your unit but it would not hurt to ask Clearvue about the top end CFM that body can handle efficiently. Too little or too much suction through a cyclone will impact the efficiency of the through put (you can also look on the Pentz site under the cyclone design spreadsheet).

I see many people put undersized blowers on SDD XLs because it matches the pipe size they want to use. Will it work, sure but not as well as the correct size for the velocity of their system.

Hope that helps,

Carl

[Frank Walker]

Not sure just how this would scale up but it has worked well for me. When I designed this system over 30 years back, most of the ideas were "via rectimus" as not much info was available. The concept was to have the first stage so large in cross section that the velocity would not support the bigger stuff and it would settle out and just the fines would continue on through the blower and be captured in the bags. Obviously as the chip section fills up the area ratio is decreased but just need to clean it out before it gets too full. The only thing that shows up in the bags is dust that resembles face power. The blower is a 1HP Cincinnati and the AFF felt bags are a little less than 50 sq ft.

Duct work is in the floor and comes in on the left side of the picture.

Frank

DC2.JPG

[andy bessette]

Pretty sure the cyclone and blower want to be married. And that this should be the first stage.

[Eric Keller]

I used to run my DC through a trash can first with no baffle or any other airflow control at all. It doesn't do much for the fine particles, but it sure did get most of the big stuff out.

[Bill Space]

Frank said:

"The concept was to have the first stage so large in cross section that the velocity would not support the bigger stuff and it would settle out and just the fines would continue on through the blower and be captured in the bags."


I used the same concept as Frank. My separator is about 2' x 2' x 6' high. Holds a large garbage can in the bottom, and has a simple baffle. The air flow comes in the top, and exits behind the baffle to the one side. 90+ % (maybe more?) of the chips and dust fall into the garbage can. Frequently empty the garbage can, but rarely empty the dust collector bag.

2 HP dust collector in my case, but I am sure the idea could be scaled up.

Bill