Thread: Another boring DC question - Cyclone & DC Setup - Air Straightener

Two things I can see immediately

1) As soon as you have 4" ducting anywhere in a DE system it matters very little what size ducting is used elsewhere - the 4" acts like a rate limiting step so 425CFM is the max flow no matter what else is used.

3) Using an SSD with the air spinning in the correct direction will rob a further 20-25% of the flow so you will be then down to ~350 CFM or about a factor of 3 less than the minimum requirement for fine dust control.
Air spinning in the wrong direction will drop the flow even further
Yes they do keep filters cleaner for longer but what's the point if a significant proportion of the fine dust is never captured and being left behind in the shed?

The best flow that can be achieved with a standard 2HP is using the modification to the input and output of the Generic 2HP impeller as per the sticky at the top of this forum.
With a pleated filter up to 925CFM cam be obtained provided
- 6" ducting is used through out
- no chip collector or small cyclones are included
- machine ports are opened up to avail themselves of the flow - if you are not prepared to do this then don't bother with the rest

Yes you will have to keep your filters clean but it shouldn't be too bad as you have a pleated filter.

The problem with your particular model of the 2HP is the fixed size of the impeller outlet (~5") which limits the flow to less than 800 CFM.
The other 2HP DC have a rectangular equivalent that is is almost 6" which is how they can get the greater flow.
Major metal working surgery could be used to open that up your impeller outlet but that is really for you to determine

Thanks BobL.

Some very blunt but informative points which I was hoping for. I had know idea how much loss would be introduced by the inclusion of a cyclone.

It looks like I have some work ahead of me.

Thanks again for taking the time to respond.

Cheers Pal.

Trav

Originally Posted by TBM1

Thanks BobL.

Some very blunt but informative points which I was hoping for. I had know idea how much loss would be introduced by the inclusion of a cyclone.

Sorry if I sounded a little blunt.
Hope you can work something out.

Having never looked inside of a SDD, have you confirmed that the exit from the cyclone is in fact directional.
I have a a ClearVue CV1800 and an original CV Mini, so can see the activity in cyclone body.
Both of these cyclones have length of straight tubing positioned in the center of the vortex, leading to the exit. The air stream is forced to abruptly change direction as it moves to the fan.
You can confirm this with Oneida, but I doubt that the direction of fan spin has little effect on the performance of this device. It is designed for and used in hundreds, if not thousands of configurations just like yours.
As well, you appear to have enough straight hose between your SDD and fan to level out any turbulence in the air stream. Replacing as much flex hose as you can with smooth walled pipe will gain some benefit. You have 3 floppy elbow in your setup.

As Bob notes, you can only do so much with 4" runs. If you have come across Bill Pentz site, find his static calculator. Enter you system components as configured for 4, 5 and 6" sytems. The differences sre amazing.
If you are getting dust in your waste bin and little carry over into your filter, then I would suggest your system is doing the best it can.
Don

Hi Don,

Thank you for the feedback. The SDD is quite simplistic in design even though quite effective. The exit pipe being 6 inch just goes straight into the body of the cyclone but I have not taken a measurement of that length.

The impeller housing inlet is 6 inch but unfortunately the outlet to the filter is only 5 and from what I have seen, it is going to be major surgery (as BobL states) to open this up. That said, I still intend to replace all my 4 inch lines with 6inch/150mm PVC pipe with 45 degree bends. I got pricing from a plumbing supplier and it actually works out to be approx. $13 per meter of solid pipe compared to $32 per meter of the flex tubing that most wood working suppliers sell which sold me on the upgrade. It's the fittings that make the transition an expensive one! The is a perfect example of do it once and do it right. It is just a shame that I never knew about sizing or the basic principles when I first set up my system so now I have about $500 worth of 100mm stuff I am stuck with.

I am going to lower the impeller which is going to shorten the 6 inch hose that connects the SDD to the motor slightly but this is so I can get a straighter connection point between the impeller outlet and the filter/collection bag housing.
I should have installed the filter and bag first then lined up my motor to suit but lesson learned.

Hopefully I will see a benefit going to the larger pipe work even though its hard to run tests without any testing equipment, but I am now a little more educated on what to look for in my overall DC system to remove possible choke points on the dust collection. Now that BobL raised the fact the SDD does choke the system somewhat I tested that by simply putting my hand over inlet of the SDD when running. I also just turned the DC on briefly without the SDD and the suction from the 6 inch hose that connects the two was huge. I never realized how much the SDD inline with my equipment would affected the CFM as it does but it is definitely worth having for the sake of separation and clogging filters IMO.


In regards to any bypass, I don't have a workshop full of gear ATM but the usual, TS, Thicknesser, SAWs etc. and what ends up in the bag is the smallest fines almost like talcum powder that just sits in the bottom. Everything else (other than the nasty stuff we can't see but try to capture) ends up in the collection tub so it is performing reasonably well.

I have just put the pleated filter on so I haven't had a chance to see whether this also helps with airflow and performance. If I were in a position to, I would have built a separate shed to house the DC but for now it will have to remain in the workshop.

Thanks again. I respect everyone's opinion on this forum.