Duct pipe at inlet

[Flintshooter]

After a couple of years of wanting to upgrade its looking like I might actually be able to swing it financially in the not too distant future.
I spent quite a bit of time yesterday on Bill Pentz’s website trying to find what he wrote about the importance of the upward slanted inlet. I know that I read it years ago but I can’t find it now.
Here’s the problem. I want to use a 55 gallon drum and whether I install inside or outside the actual duct is going to have to go level in a hurry. An outside install would gain me close to a foot because the ground drops more on that side of the building but even there I won’t be able to get the cyclone inlet low enough to allow much of an upward slant to the duct work.
How critical is it for the duct pipe to slant up from the inlet for an appreciable (or any) distance?

 

[McRabbet]

Ideally, you want at least a five foot straight section of pipe before any turn into the balance of your duct work -- a Fernco adapter (rubber coupler with band clamps) will allow a subtle curve at that point. If you cannot position the cyclone inlet low enough to allow for the needed rise, you could tilt the cyclone so the inlet entry duct is more horizontal. You can also shorten the inlet straight run, but that will create more turbulence and a slight reduction in separation efficiency.

 

[Flintshooter]

By mounting it outside I can get the five feet but immediately after that five feet it is goin to have to angle slightly downward and then angle again to get the duct in the shop parallel to the ceiling

 

[Curly1]

The two slight angles won't have much overall effect on the flows but if you do as McRabbet suggested, mount the cyclone itself on an angle, the inlet pipe will be horizontal and you won't have any angles in the main duct. If outside then the bottom of the cyclone will be a little further from the wall than the top and the duct from the cyclone will have a longer straight run to the first wye/elbow in the run. The ClearVue cyclone does not have to be perfectly vertical to function correctly despite many believing it does.

Pete

 

[Flintshooter]

Okay, I understand tilting the cyclone to make the inlet level. What I don’t understand is why, if that doesn’t have any effect on the function of the cyclone (regardless of the angle the actual unit is mounted at) the intake on the cyclone is tilted up to begin with.

 

[McRabbet]

Angled ductwork coming to the inlet ramp will cause turbulence and disrupt the flow through the inlet ramp, while tilting the cyclone won't cause turbulence in the main body of the cyclone, thus separation will remain very good. Most CV1800 cyclones are 99.9% efficient or better.

 

[Curly1]

Okay, I understand tilting the cyclone to make the inlet level. What I don’t understand is why, if that doesn’t have any effect on the function of the cyclone (regardless of the angle the actual unit is mounted at) the intake on the cyclone is tilted up to begin with.

The inlet is tilted so the incoming air is forced into a downward spiral, throwing the dust against the walls towards the collection bin. It relies on centripetal force to separate. With a straight in entry the flow is more turbulent since the "fresh" air is colliding with the air already spinning inside before it works its way down. The separation isn't as efficient.

Pete