Thread: Thein Top Hat seperator

What sort of blower is it - it may not generate enough pressure to move much air.

Separators, filters, machines and ducting all consume pressure so there may be none left to move much air/dust.

The first thing would be to measure the static pressure it can pull using a manometer and that will tell you what you can add and still move air.
Instructions on how to build and use a manometer are available in this forum

If you can do it, Venting a DC outside a shed is the best thing you can do with a DC.

Assuming you can vent outside then adding a separator will reduce your flow which means more dust won't be captured at source.

Thanks Bob great advice as always mate, with the current 1.6kw blower (large bouncy castle one) it does indeed move a lot of air but I'll do as you suggested and whip up a quick manometer, Ill dig up the guide of the forum or just ask my friend Google. I've done some testing and it does seem to pull and filter a good size pile of chips and only ever intend to be using it on one machine at a time, the duct runs will be quiet short as my shed is only 6 x 3 and will have all my machine in a horizontal run so no real hard 90 bends, I have a heap of 90mm pipe and connections laying about though I intend on upgrading to at least 150mm as soon as I can.

I think venting outside of the shed is my preferred route as well and out of interest I'm going to mount some black matt cardboard to a board and place that on a 45 to the exhaust stream just to see over time if there is any notable build up on it.

The top hat is pretty large and to be honest it cost me next to nothing to build as its made from part I had laying around including a half sheet of MDF so even if it fails I had fun building it, all but the bending of 4mm MDF into a circle felt like I was bending a CD just when it shatters. Top hat is very solid and if it needs a larger blower then at least I know in principle the design works. I'll post up some pics when I build the bin as I want to give a wooden keg style a go, I know I can buy a metal trash bin but where is the fun in that.

Out of interest using water what sort of value range and I looking for Bob?

Damien

Originally Posted by skara

Out of interest using water what sort of value range and I looking for Bob?

The generic 1HP DC typically generates 6" of water column pressure but the small filter/bag needs at least 3" to push air through it so that leaves very little left over to move air
A generic 2HP should generate about 8" of WC and the larger filter bag soaks up around 1.5" of pressure
A 3HP twin bag should generate about 8-10" and the filter bags should soak up around 0.75"

A chip collector can soak up considerable pressure and reduce flow which is why I don't recommend any sort of chip collector on a DC.
Yes they do keep filters clean but that is in part because they don't collect as much fine dust as they would if they were not attached.

Without being too rude, 90mm ducting is VERY restrictive, The MAX flow rates a 90 mm duct can generate under normal DC pressures is about 300 CFM
Add a chip collector and a machine and you'll be down to 200 CFM i.e. near useless for fine dust.

Thanks again Bob,

I've had a look through the forum and can see many suggestions to do static testing though I haven't come across the actual instructions. With static testing do I need to obstruct the blower intake completely and place one end of the gauge into that obstruction?

Nope be as rude as ya want I'm the hack here, yeah I was pretty sure using 90 was going to be a bad idea I just had it lying about, If you can give me some more info on static testing or suggest a site Ill do that then work from there regarding duct runs.

Thanks

Originally Posted by skara

Thanks again Bob,

I've had a look through the forum and can see many suggestions to do static testing though I haven't come across the actual instructions. With static testing do I need to obstruct the blower intake completely and place one end of the gauge into that obstruction?

Nope be as rude as ya want I'm the hack here, yeah I was pretty sure using 90 was going to be a bad idea I just had it lying about, If you can give me some more info on static testing or suggest a site Ill do that then work from there regarding duct runs.

Thanks

Yep completely seal off the intake and put one arm of the manometer into the intake, run the fan and measure the height difference of the water column.

Is the fan a squirrel cage fan or proper impeller.
If it's a squirrel cage fanlike the one on the picture below then it's not even worth testing for DC work.
They can generate 6" of water column but the have the wrong fan curve and cannot sustain the flow under resistance.
Squirrel cage fans can move a lot of air so are good for venting but near useless for dust collection.
This is the one I have on my welding and spray booth.

No its not a squirrel cage its an impeller so all good on that one, the fact that its designed to keep a large bouncy castle inflated is what made me think it might be a usable in this application, its tempting to go into the shed and do a quick test not but im pretty sure the teenage kids that are a meter from it might take issue. I've actually used a manometer as a spirit level a few times when levelling out my shed and other large objects. Very accurate over large distances.

More tomorrow

OK so I have done a static test and I'm getting only about 700cfm using the chart you posted in another forum. Now that might actually be a little higher as what I have done due to there not being a an actual attachment to the inlet of the blower (150cm inlet) is build a square box and fixed that to the side temporarily though it might be leaking the tiniest amount of air. What I intend on doing if it looks usable it to take the shroud off and fix a air tight flange with a 150 mm opening, take off the plastic grill which is probable a little restriction and replace that with a metal one and then refit the shroud, Might help might not. The point is this is intended as a "better then what I currently have" solution until I can afford a pro job and also be a fun project. I've enjoyed building the top hat and I think it has come out looking pretty clean and seems to work very well.

with that Bob do you think its powerful enough to work with?

Cheer

Originally Posted by skara

OK so I have done a static test and I'm getting only about 700cfm using the chart you posted in another forum. Now that might actually be a little higher as what I have done due to there not being a an actual attachment to the inlet of the blower (150cm inlet) is build a square box and fixed that to the side temporarily though it might be leaking the tiniest amount of air. What I intend on doing if it looks usable it to take the shroud off and fix a air tight flange with a 150 mm opening, take off the plastic grill which is probable a little restriction and replace that with a metal one and then refit the shroud, Might help might not. The point is this is intended as a "better then what I currently have" solution until I can afford a pro job and also be a fun project. I've enjoyed building the top hat and I think it has come out looking pretty clean and seems to work very well.

with that Bob do you think its powerful enough to work with?

Cheer

What was the actual pressure?
What diameter is the impeller?
Can you take a photo of the impeller - even a partial phot will help
What RPM is the motor?
Whatever the case it will make a fair ventilator.

Originally Posted by BobL

What was the actual pressure?
What diameter is the impeller?
Can you take a photo of the impeller - even a partial phot will help
What RPM is the motor?
Whatever the case it will make a fair ventilator.

SP = 3.7in
impeller Diameter 14in
photo attached
RPM = No idea lost count at about 20rpm

20150414_181319[1].jpg

Originally Posted by skara

SP = 3.7in
impeller Diameter 14in
photo attached
RPM = No idea lost count at about 20rpm

20150414_181319[1].jpg

Thanks for the info.

The pressure is just too low to do anything with this impeller.

It looks like a very basic shallow, straight-vaned impeller and the loose fit design looks commensurate with the low pressure and will be unlikely to sustain flow under back pressure.

If you get to keep it I would use it as a shed ventilator of fume/welding/spray booth fan.

While various cyclones can be pretty efficient, there will always bee some blow by...... in particular if the air velocity in the cyclone drops below the efficient level..then the blow by can be considerable.

I would always recommend some sort of post filtering with a cyclone ...... if you are just discharging outside...yeh it can make a mess and may even blow back into the shed.

cheers