Separator seems to work - but dust all over

[hankh]

Well, I built my Thein separator, using a 69 liter/18 gal. fiber drum with a lever-lock ring. I've attached it to my Bosch 4000 TS with 2" flexible tubing and a 1150 W (220Volt) shop vac on the other side. The vac comes with a 36 mm (internal) diamater hose. I had to improvise the connection between the vac hose and the 2" connector to the DC and at that point the internal diameter goes down to 25 mm. No chance of an air leak. Initially seemed to work great. I don't have any way to measure how much dust stays in the drum and how much goes to the vac - but it seems like there is alot in the drum and not much in the vac. BUT, today, after not much use at all, I find that dust is spewing all over the place - coming back at me from the saw and over the top - in addition to what does go into the drum. Also looks like there is more dust in the vac. I tried to compare on my hand the suction directly from the vac and then from the DC - didn't feel any difference (for whatever that sophisticated scientific test is worth).
Any ideas what is wrong here?

[phil (admin)]

Is it possible you have a large cutoff piece clogging the hose somewhere?  This same thing recently happened to me and I found a larger cutoff had become stuck in the hose right before the separator and had substantially reduced my airflow.

[alan m]

if it worked before then the design is ok.
its probably either a leak or blockage.
empty both the vac and seperater and run  it for a while to make sure it is letting more through.
small slivers often wedge inside my vac hoses. tablesaws are notorious for bits like that.
if the pipes are clear you must have a leak.

[hankh]

I check the lines - no blockages and I don't find leaks.
Could it have something to do with the air flow speed and volume ratio? If so, how do I check that?

[alan m]

its hard to tell from the pic but to me it looks like your inlet is aim too much towards the wall of the seperater.
by hitting the wall hard you can slow the dust down too much or bounce it towards the outlet.
i would also remove the rubber seal , it might create turbulance
the baffel plate looks like 3/4 " oak faced mdf.
i would chamfer the bottom edge to reduce the thickness at the slot.
i would lower the baffel down as far as posible on those threaded rods. moreheight should mean better seperation

[phil (admin)]

I hadn't noticed the part where you said there is a 25mm bottleneck.  That is only 1".  That is very restrictive.

Also, how are those fittings attached to the lid?  It looks like you used a steel top and attached the fittings, are you sure there are no leaks there?

[hankh]

I suspect that the 1" connector might be at least part of the problem.  I am looking for a better solution athat will leave me the 1-1/2" of the the vac hose.

The fittings go through rubber seals which are air-tight. That shouldn't be a problem,  but I will re-check. That goes to Alan's suggestion about the seals - can't really remove them.

I will lower the baffle, can probably go down about an inch wtihout replacing the rods.   I will adjust the direction of the inlet. Should I increase the distance between the outlet fitting and the baffle?

the baffle is just under 1/2" (10 mm). It is some synthetic product, not sure if it is MDF.  With this thickness, do you still recommend chamfering the bottom edge?

thanks for your help.

[tvman44]

I have read on here the thinner the better for the baffle, I used 1/8" Masonite (hard board). :)  But then if it once worked fine then something has changed & I doubt the thickness of the baffle did.

[alan m]

i would still chamfer the baffel.

the seal i would remove is in the end of the inlet bend

i didnt cop the 25mm restriction part.
thats definetly hurting the performance.

but these would have been there when it worked

[hankh]

I followed all suggestions (except removing the seal - still not sure what that refers to) - cleared the 25 mm bottleneck (hose now goes from 50 mm to 35 mm),lowered the baffle, corrected the angle of the inlet, chamfered the edge of the drop slot. A small improvement (I think), but problem not solved. Any other ideas?

[alan m]

you should have chamfered the bottom of the baffel. (sorry should have been more specific)
maybe it can be fliped over

the seal probably isnt a major problem.


i think your problem is sealing
there could be air getting in between the top and the drum or around the 2 pipes.
i dont trust those seals to be perfect especially with a vacum on them.
i would silicone caulk up around them

[Schreck]

...except removing the seal - still not sure what that refers to...

I think Alan is referring to the rubber gasket inside the hub of the inlet.  This would cause unwanted turbulence.

[hankh]

I'm thinking that the problem is not in the separator. I attached the shop vac directly to the saw, first removing the filter, eliminating that as a potential source of blockage. I sealed with silicon the connections between the vac hose and the the 2" hose that connect to the dust outlet of the saw and and between the hose and the saw. Still got dust coming at me above and below the table. I've read that the exhaust system on the Bosch 4000 is not very good. Does anyone know about that? Could that be a contributing factor? Could the vac simply not be strong enough (although it does seem to meet specs that I've seen on this forum)? Any other ideas?

Alan - I thought about which side to chamfer before doing so. My idea was that the slope was to help move the dust down into the drum.  Guess I was wrong.  What is the advantage in chamfering the bottom?

[alan m]

i think the general consensus is that you want a very thin edge there. having the chamfer on the bottom means a very definitive point between above and below. you want the dust to go down adn stay down.  having the chamfer on the top would make it easier for the dust to come back up


what kind of saw is it.

maybe a pic of the whole sytem might find the problem

[hankh]

I discovered some small defects (leaks) in my 2" hosing. Between replacing that and probably replacing the baffle to something thinner, I have some revisions to make. I'll get back online afterwards and let you know if the problem is solved or if I have to keep looking. Thanks for your patience and help so far.