J. Phil Thien's Projects

Hi Bill. I would absolutely be interested in the results of any testing you cared to perform and share. I think another baffle (whether one of the sketches above or some other design) could be considered to add value if-and-only-if (1) short circuiting was indeed occurring and in the absence of the two conditions Phil described above that usually cause it and (2) if the additional baffle had its intended effect without also introducing some form of "fatal flaw" in terms of airspeed, SP, CFM, separation efficiency, etc. And Phil's reply all but confirmed for me my suspicion that #2 is a pretty big "if".

Having said that, suspicions and theories are one thing but real-world testing is the only way to know for sure. So by all means if you're interested enough to perform the testing then I'm certainly interested in hearing the results! Thanks!

Hi Phil. Thanks for the reply. And thanks also for sharing the results of your research, and for making this forum available for discussion and Q&A.

So just to make sure I understand are you saying that as long as the airspeed entering the can isn't too slow and the elbow is properly aligned in relation to the can then it should be possible to make this combination of can size and elbow size work without a "short circuit"? I don't think (?) airspeed should be an issue in my case since I will have just a single run of about 15 total feet of mostly rigid metal duct and I have an upgraded canister filter with a lot of surface area. The biggest impediment to airspeed in the whole system will probably be the elbow inlet itself. I'll try to align it as close to 90 degrees as I can get it but I think it will necessarily end up being a little less than 90.

I kind of suspected that like you explained the vertical baffle on one side might throw the cyclone effect out of balance and have an overall negative impact of one kind or another. So in any case I decided to go ahead with the standard build and experiment with add-ons only if I did end up experiencing short circuiting problems, and then only after trying to mitigate other factors like leaks and alignment issues. My build is still in progress but after it's finished and I've had a chance to use it a little I'll update with how it went. Thanks again!

I'm planning to use a 31 gallon metal trashcan and 5 inch plumbing (metal HVAC). From what I've read here it seems like for 5 inch the preferred or at least usual approach is a side inlet, with or without a "top hat". But in my particular setup this isn't really practical so I've decided to go with the "original" Thien separator using a top-mounted 90 degree elbow as the inlet.

With the dimensions involved (5 inch inlet, 5 inch outlet, and approx. 20 inch diameter can) do I need to be concerned about the inlet and outlet being too close to each other, and the incoming chips and dust getting caught up in the outlet's suction before they have a chance to slow down over the baffle's cutout and fall below?

If so, would a second vertical baffle, or even just extending down one side of the outlet pipe, help to prevent the premature mixing of the two air streams, or would it somehow just get in the way of the overall separation process? Or am I just over-thinking this?  ???

I attached a few Sketchup drawings that will hopefully make this more clear.