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

[travis mayne]

Hi guys,


Feeling a bit dejected at the moment. Basically, started to re configure my Super Dust deputy and Carbatec 2HP DC to make some more room in the workshop. To start, I won't pretend to understand all the physics that come into play when designing a truly efficient DC system. I understand the usual stuff like 6 inch over 4 inch line and minimal bends in lines that don't have 90 degree elbows etc. etc. to maximize efficiency.
All I want is to minimize dust that is created and spread around my workshop not to have a 100% dust free environment which is unrealistic. I have a room air filter and I also use PPE which is the most important and cheapest piece of equipment you can own.
I have had the SSD and DC for a while now but I have now removed the impeller from the rolling base and made my system into a more vertical/tower configuration as per the attached image that is separated by approx. 500mm of 6 inch tubing. Whilst doing this I actual took more notice of the inlet on the SDD and the rotation marking on the impeller. Again, I am not that experienced with DC systems but this did grab my attention so what did I do, I resorted to good 'ol Google to research whether this would impact on performance and I seem to have opened Pandora's box.
I am trying to consolidate everything here from I have read to get a better understanding of what to do now and ask for some better informed guidance. Hopefully this may also help others that find themselves in the same situation.


In summary, the SDD has been designed to spin the moving air CCW and I never really took any notice of this when I first connected up by DC system as i just connected everything together and thought "yeah it seems to work ok". The rotation of my impeller is going the opposite direction and from what I have read this is bad. The motor will draw more current as it is now working harder to rotate the spinning air from the cyclone to the impeller. This in turn creates turbulence, introduces major SP and massive drops in overall CFM.


It appears I have limited options as I can not afford to by a new Cyclone or a different motor at this time.


I looks like I can either:
1. Leave it the way it is and put up with the current suction I have at my machines (hoping I don't damage the motor)
2. Put the actual DC back together. Some guys have said that introducing a longer length of hose between the impeller and cyclone removes/minimises the issue that is created by coupling the motor directly to the top of the cyclone. Not sure how accurate this is?
3. Install some sort of air straightener into the pipework between the cyclone and motor to neutralize the spinning air even though this still creates a small amount of suction loss


If I go with option 3 I can't find enough information on this other than to either using a cluster of plastic tubing or a cross formation made from sheet metal to accomplish this (I have attached my interpretation of this). I was hoping that some forum members have done this and and can provide some feedback as I am lost with all the science and figures that seem to be circulating around.


I.e. How have people done this? What was the length of the tubing? Where does it get inserted? How is it fixed inside the cyclone or pipe work etc.


PhilT & Retired2 seems to have a wealth of knowledge on this topic so I would appreciate any feedback you may have on this (recycled) topic as I am a little lost


Thanks in advance.


Cheers


Trav
Oz.

[Michael W. Clark]

Yes, you have to break the spinning vortex if the fan is rotating opposite the cyclone rotation. Either of your vortex breakers will work shown in photo 3, but the cross is less prone to plugging if you were to get bypass.

The other option is to turn the fan horizontal and come out of the side of the vertical hose. The right turn will break the vortex too.

Industrial cyclones use a horizontal scroll outlet which may be difficult for you to build. A tee will be a major improvement over what you have.

FYI, you don't need all flex on the outlet or inlet, use a short piece to isolate the fan and cyclone. Make the rest out of rigid ducting. Minimize flex on the inlet too.

Mike

[travis mayne]

Hi Mike,

Thanks you for taking the time to reply, it is much appreciated.

I was thinking of doing something like in the attached which I thinking what you are suggesting about creating a horizontal tee? This orientation would basically reflect how the dusty looked prior to me pulling it apart and mounting it in a tower fashion.

I might experiment with the vortex breaker as you call it. I am just not sure how long to make it and how to fix it internally.

Thanks again

Trav.

[Michael W. Clark]

You want a hard tee, not an elbow like you have it shown. The vortex will go around the elbow, although it will likely weaken some.

Do a 6x6x6 tee in metal or pvc. Cap the top and come off on the branch side of the tee. You can probably rotate the tee and your Jet DC downstream so you can shoot strait into the jet and eliminate those bends in the hose.

[Jim Andrew]

I picked up a dustkop cyclone, and it has a "x" in the tube to stop the rotation. It is made of sheet metal, and just welded at the top, and goes down the tube, so appears if you were to make an "x" from metal, that would fit in your pipe, that would stop the rotation. The X in the dustkop is about 2' long. That virtual X in the lower right of your pic is what I refer to. It does not have to fit tightly in your pipe, just slide in, and fasten on one end only.

[Steve Peterson]

I don't see any reason that the connection between the SDD and the blower would need to be the same size as the inlet. Most of the dust has already been removed, so there is no longer a minimum air velocity to maintain. This opens up more options.

Here are my thoughts:

The primary purpose of the separation is to prevent any air disturbance inside the SDD. This helps prevent the dirty incoming air from mixing with the clean outgoing air.

Anything that happens to the air after it leaves the SDD will not affect the separation.

The air will be spinning CCW (viewed from above) inside the SDD and it will switch to CW at the blower. The air will be turbulent, but not spinning in the middle section of the tube.

I think that an air straightener would only be useful in the middle 1/3 of the tube. It will add turbulence if it starts right at the SDD because the air will need to quickly switch from CCW to no rotation while it is still inside the SDD.

I believe that the best option is to skip the air straightener and just put a large connection between the SDD and the blower. The primary function is to let the air switch directions after it leaves the SDD without adding much resistance. Bigger is better in this case. A section of 8" pipe would be good. You can also just make an 8" or larger box.

Steve

[Peter Aeschliman]

Travis, thanks for posting this!! I have wondered whether my setup was backwards (grizzly 3hp motor and blower on an ebay cyclone). Being the knucklehead I am, I assumed that since the outlet from the DC was on the same side as the inlet to the cyclone, that they were spinning in the same direction.

I didn't really stop to think of it, but now I realize I have the same problem as you do. I was wondering my my dust collection got significantly worse when I switched from my 4-bagger to my cyclone. I used the same motor, impeller, and ducting, except I started exhausting outside. I assumed that removing the filters would make up for the normal CFM loss of installing a cyclone, so I was bummed when I got it all set up and noticed much less suction than before.

I briefly wondered about the rotation issue, so I read a bit about air straighteners and ran into the same issues with getting straight (no pun intended) answers as you did.

In my case, I think I'm going to just use this as an excuse to upgrade. Unfortunately I don't have the ceiling height in my basement shop to add an air straightener or a longer duct between the cyclone and the impeller...

[travis mayne]

Thanks for the feedback guys. It is much appreciated and I take on board everything that you have taken the item to respond with. It is always daunting when there is so much information and opinions which can and do differ which makes it hard for the uneducated to filter through and make the correct decision. I know that sometimes it comes down to trial and error but without a basic understanding of the fundamentals (regardless of the topic) you can find yourself going in circles (no pun intended here either) or actually throwing more money at something that can easily be fixed with some knowledge. I know this is an old topic that I was shy about recycling but it has been difficult to find a good starting point.

Jim,

Do you have a photo of your cyclone setup and air straightener by chance?

Thanks again.