How much pressure loss in a typical Thien separator?

[bobgroh]

Realize this is a bit of a loaded question but does anyone have an idea of how much loss I should expect in a 'typical' Thien separator?  Thinking of a design for a dust collector rather than a shop vac (i.e. low pressure).

Bob Groh, Blue Springs, Missouri

[retired2]

Realize this is a bit of a loaded question but does anyone have an idea of how much loss I should expect in a 'typical' Thien separator?  Thinking of a design for a dust collector rather than a shop vac (i.e. low pressure).

Bob Groh, Blue Springs, Missouri

In the long thread on my build there is a table of performance data.  It does include measurements with and without the separator installed.  I don't remember the exact numbers, you can look them up, but I think in my case the separator results in about a 35-40% hit.

[bobgroh]

Thanks for the reply.  I did go into your 'build' posting and found the data you referred to.  Does indicate a chunk of loss.  Ouch.  On a positive note, it also indicates that I would need to have a very careful build to minimize losses.  Not too surprising overall - a cyclone can/does have a bit of a loss.  And in a system like I am going to use, I just have so bloody little to work with. But, hey, there is my challenge!  Again thanks and I'll keep digging away at the design.

[retired2]

Thanks for the reply.  I did go into your 'build' posting and found the data you referred to.  Does indicate a chunk of loss.  Ouch.  On a positive note, it also indicates that I would need to have a very careful build to minimize losses.  Not too surprising overall - a cyclone can/does have a bit of a loss.  And in a system like I am going to use, I just have so bloody little to work with. But, hey, there is my challenge!  Again thanks and I'll keep digging away at the design.

I think it is going to be difficult to reduce the separator losses much below what my experience because it already includes the benefits of a bellmouth and air straightener.  The only real change that others have tried since I built mine is a 2H build.  Some people have said it is more efficient, but I have not seen anyone post hard data to prove it.  If I thought there were significant performance benefits to a 2H unit, I would rebuild mine even though with my Delta DC that would add quite a bit of height to the total configuration.  And of course, a 2H will be heavier although in my case that is not an issue because I drop the can rather than raising the separator in order to empty the waste.

[bobgroh]

I am still pondering and planning.  I will probably just take my best shot at building the most efficient separator that I can by gleaning all the 'best practice' from all the postings. Combine that with short runs and I might have some reasonable flow and, equally important, reasonable dust collection. Right now, I am using an old 6 gal ShopVac with a Dust Deputy (which I will keep for shop cleanup and general work) which sort of works - certainly the combo of a Thien style separator and the my little SS DC-3300 will be an improvement. It's fun just using the old grey material (I am a retired electronics engineer with a strong mechanical and analytic bent).

[BernardNaish]

Hi bobgroh.

You will not do much better than follow retired2's build in its entirety.

The only thing I might do is not build a 2H version. I might however build a 1 1/2 height version or more likely I would build a 1 1/4 height top hat. I would do so only because my machinery and the way I use it tends to produce long thin shavings that may catch at the end of the slot. This has been reported several times and I believe a narrow space beneath the inlet rectangle might well solve this problem.

I would also make the inlet transition from round to rectangular rather longer, something like three times the diameter of the round pipe.

I might also make the inlet rectangle height to width ratio such that the height is a little greater and the width a little less. Perhaps the width might be something like twice the width of the separator slot.

I have not much science to support my ideas but I am quite a good hunchman .  It seems to me that if the inlet stream is closer in size to the separation slot size then we might be better off. The trade off might be that the greater top hat volume might lose too much of the suck.

I hope you let us know you get on particularly if you can take some measurements.