Cyclone restriction?

[Martin Wasner]

Anybody know of what kind of restriction or loss of airflow there is from adding a cyclone into a system? Is it a linear or compounding problem? As in maybe it's 2% loss on 2000cfm fan, but more like 4% on a 5000cfm fan? <---- completely made up numbers btw.

I'm asking because I'm debating about adding a cyclone in front of my pull through baghouse at some point, but it might make more sense to just sell the whole works and start over with completely separate and independent components.

[Doug Garson]

See my post in the general woodworking and power tools section on "airflow hoses and dust collectors". Pressure drop across a cyclone will vary as the square of the flow so double the flow would result in four times the pressure drop.
I see the thread I referred to has been moved to this shop section

[David Kumm]

You need to design a system from the ground up. A cyclone needs to be designed to separate best within a certain cfm and inlet velocity range. The design and the velocity will in part determine the pressure drop of the unit, typically 2-6" SP. The resulting cfm loss needs to be compensated for unless you are running a larger than needed impeller and motor. The filters need to be sized correctly as well. Adding a cyclone to a direct bagger helps with the clean up but may reduce the effectiveness of the system overall. Dave

[glenn bradley]

As David says, adding a cyclone (or anything for that matter) in front of a blower that is not designed for that load will result in sub-optimal performance. Throwing blue-sky numbers around I quickly looked up a 3HP cyclone and 3HP bagger from the same maker. The bagger is rated at 2320 CFM where the cyclone is rated at 1654 CFM. I gave up on my pre-seperator on a previous system because it just hit the performance too hard for my purposes. A dust collection system is a chain and any weak link can bring you down.

[Jim Becker]

See my post in the general woodworking and power tools section on "airflow hoses and dust collectors". Pressure drop across a cyclone will vary as the square of the flow so double the flow would result in four times the pressure drop.

That thread was actually moved here to Workshops where dust collection topics, with few exceptions, are handled.

Jim
Forum Moderator

----

OP, cyclones do have some level of impact on system performance, but a properly designed cyclone system will do a great job. What you might want to do is talk to a dust collection specialty house, such as Oneida or one of the other industrial concerns that do the same, and get their engineering take on the impact of adding it to your larger existing system versus replacement. This really is an engineering situation.

[Martin Wasner]

You need to design a system from the ground up. A cyclone needs to be designed to separate best within a certain cfm and inlet velocity range. The design and the velocity will in part determine the pressure drop of the unit, typically 2-6" SP. The resulting cfm loss needs to be compensated for unless you are running a larger than needed impeller and motor. The filters need to be sized correctly as well. Adding a cyclone to a direct bagger helps with the clean up but may reduce the effectiveness of the system overall. Dave

I kinda figured as much. I was just kicking the idea around so I thought I'd float it out and see what others said. I'd be nice to have the buffer of the cyclone to hold material when need be.

When you say "the filters need to be sized correctly", do you mean they just need to be adequate for the cfm, or is there harm in over sizing the amount of filter material? I ask because I've been kicking around the idea of building my own filter setup using pleated filters instead of socks. Push the air through from the outside in through the filters. I've got an idea for cleaning the filters using a spinning nozzle instead of pulse jet.

If I had the budget to do it from scratch, I'd do everything separate units. Out of the building, through a cyclone, to the fan, through the filters, back into the building. I'd also set it up so I could dump the air from the fan straight to the outdoors during the non-climate controlled months.

[James Gunning]

You can't have too large a filter area. The larger the surface area, the less the back pressure from the filter. Ideally, venting the blower/cyclone directly to the atmosphere is best, but comes with considerations like make-up air and combustion products. Your separate components idea would work as long as you can keep the ducting connecting them very short. Each inch of duct adds static pressure loss. That and space requirements is the reason commercial cyclone units are built close coupled instead of as individual components spread out and tied together with ducting.

[Alan Schaffter]

Anybody know of what kind of restriction or loss of airflow there is from adding a cyclone into a system? Is it a linear or compounding problem? As in maybe it's 2% loss on 2000cfm fan, but more like 4% on a 5000cfm fan? <---- completely made up numbers btw.

I'm asking because I'm debating about adding a cyclone in front of my pull through baghouse at some point, but it might make more sense to just sell the whole works and start over with completely separate and independent components.

First, it is not linear- it affects that point on the fan curve where your system operates. It really depends on your system- CFM, SP, diam. ducting, etc. and the cyclone size and design- ClearVue vs Oneida vs JDS (and other short cone clones: JDS, Laguna, Jet, etc.). I'm probably wrong here- memory is not what it used to be- but I think Bill Pentz tested a few- 2" - 2.5" of SP for ClearVue and 4+" for a DIY baffle separator. To see how it affects your system you need to add that to duct/fitting loss and use that data with the fan curve.

[Martin Wasner]

That and space requirements is the reason commercial cyclone units are built close coupled instead of as individual components spread out and tied together with ducting.

Closely placed, but still separate units. If something goes down, it's nice being able to get at things quickly and as really as possible. Right now my motor is almost 17' in the air, if I need to pull it, it'll be a problem.
I don't know what it weighs, but even if I could split the fan in the dust collector, I'm not carrying probably 300# down a ladder. I should look and see if there's lift points in it. I should also look and see if the forklift can access it.

The other thought I had was having a platform welded up to hold a cyclone and just removing the motor and fan from the baghouse and putting a blower in between them.

Or, just call Donaldson and see what it'd cost to upgrade everything.

[James Gunning]

Martin,

It sounds like you have a differing set-up from most of the folks posting here. I assume you have a large commercial installation that uses a blower to push the dust to a bag house. Given the size, if you intend to use a cyclone, you probably need to consult one of the companies that build large cyclones. Oneida is the only one that springs to mind that builds cyclones for both hobbyist and larger commercial installations. I know Torit and others serve the commercial segment.