Shaker bag vs. "Cartridge" filter

[Anthony Whitesell]

The system I acquired was originally designed to use 5 6ft 12" diameter shaker bags for filtering. This may be a simple question. How do I spec a single "cartridge" style filter?

I was thinking that since the total surface area of the original bags was 2700sqin or almost 19sqft; all I need to do is identify a filter with atleast that much surface area and an inlet the same size as the blower outlet. In the world of dust collection, could this be that simple?

[Alan Schaffter]

The system I acquired was originally designed to use 5 6ft 12" diameter shaker bags for filtering. This may be a simple question. How do I spec a single "cartridge" style filter?

I was thinking that since the total surface area of the original bags was 2700sqin or almost 19sqft; all I need to do is identify a filter with atleast that much surface area and an inlet the same size as the blower outlet. In the world of dust collection, could this be that simple?

It is a little more involved than that. A good needle-felt filter will filter as well as many cartridges and will typically have better air-permeability rating.

While I don't agree with everything he says because I don't like filter bags at all, read Bob Dodge's post,#23 at this SMC thread. Also read what Bill Pentz has to say later in the thread.

Personally, I would never put an expensive cartridge on a single stage DC, they just clog too quickly and MUST have a beater bar, which reduces useful filter life. My idea of the best system is a DC with cyclone that separates out all the chips and most of the fine dust but blows the air and any remaining dust outside.

[Jamie Buxton]

Here is a page showing a bunch of cartridge filters used in woodworking dust collectors. As you can see, they have lots more surface area than those bags, and pack it into a much smaller volume.

http://www.wynnenv.com/cartridge_filters.htm

[Anthony Whitesell]

Oh goody, another thing to take into account. But how does the air permeability affect the filtration?

For a quick check/reference, all of the filters at Jamie's link have more than 140 sqft of area, more than 7x the area of my 5 bags.

As an engineer, my first guess is that it would have to do with the amount of flow the filter may pass. Such that the shaker bag's 19sqft is succifient to pass the ~1000CFM for the original system (roughly 50CFM/sqft). Thus as long as the surface area times permeability fo the new cartridge filter is higher than the CFM of the DC. I think I should be fine. The smallest sqft listed on Jamie's link was 140, so as long as the permeability is >7cfm/sqft and it is 0.5mcron or better. I think this one would work.

Based on these assumptions, I don't think I could get away with dropping from 5 to 2 bags; if the permeability rating is what I think it is. The shaker bags would probably explode. I can understand one reason for bags versus cartridge...price. The bags are cheap, but they take up so more more floor space.

Am I on the right track?

P.S. This change is not being made to a single stage but to an Oneida 2HP C950 cyclone setup.

[Phil Thien]

So five bags for filtering? That is some DC. Is it a single stage or a cyclone?

[Alan Schaffter]

Another comment about air permeability. Just because you have a lot more surface area, doesn't mean you will pass the VOLUME of air needed or that the filter will not add an unacceptable amount of static pressure resistance. Most of those cartridge filters have expanded metal shields on both sides of very closely packed filter pleats- all of which add to static pressure resistance and reduce CFM everywhere in your DC system, especially at the source where it matters!

Other than what it says in the first paragraph on the Wynn page at Jamie's link,

"As a general rule, we recommend a pair of filters for any system moving more than 700 or 800 CFM. (800 cfm corresponds to the required flow in a properly designed 6" dust collection system.)"

and in a discussion of the ASHRAE 52.2 specs, where Wynn says:

"-ASHRAE 52.2 requires a minimum face velocity of 118 fpm. This equates to over 1100 cfm on our Farr style filters! We never push these filters past about 750 cfm, and normally run them at about 500 cfm, so the 52.2 test pushes them way beyond their intended flow rating."

You will not find much data on air flow. Filtering efficiency, yes, but not air flow except some rough data points (500, 700, 750, 800 CFM- pick one), and little data on static pressure resistance. For anything more you will probably need to go to the manufacturer's web sites.

The bottom line is you need to size your filters, whether they be bags or cartridges to the installed CFM rating of your blower (not the free air inlet CFM). If your blower was designed for a big bag house style setup, I suspect it is a high CFM unit rated at 2000 CFM but probably moving at least 1500 CFM. If you use the lower Wynn number of 500, that means you would need at least three cartridges.

If you put the DC and filters outside- I'd stick with the bags. If you put it inside I would start with two 9L300BL, but ONLY if you are using a cyclone!!! Talk to people who have single stage DC's or those with a cyclone who have had a backups and had to clean a cartridge filter- it is not a pleasant job, extremely difficult if not impossible to remove all the dust from deep in the the pleats (mechanical beaters and compressed air can damage the filter media), and can permanently reduce the CFM capacity of your filter.

Now you see the rationale behind the last statement in my previous post.

[Bill Blackburn]

So five bags for filtering? That is some DC. Is it a single stage or a cyclone?

I needs to know too

What kinda monster did you score? I've never seen a 5 bagger in operation. 3 a couple times, a 4 shown on a forum sometime back but not in use. A 5 Must be backed up by a powerful motor eh?

[Alan Schaffter]

I needs to know too

What kinda monster did you score? I've never seen a 5 bagger in operation. 3 a couple times, a 4 shown on a forum sometime back but not in use. A 5 Must be backed up by a powerful motor eh?

Sounds like a FrankenSucker. I'm not familiar with the C950 but if I were a guessing man I would say the model # means it was supposed to be rated at 950 CFM? If it is one of their original cyclones with the internal filter (worst idea in the world), maybe the previous owner pulled the filter and added his own bag farm.

Edit: Ok, I found it- it is a standalone cyclone, sold without blower or filters. It, and the whole series, look like a version of the old Wood Magazine cyclone, with different dimensions, inlet/outlet sizes, etc.

"C-950 Cyclone Separator 7" Dia. Inlet, 8" Dia. Outlet, 9" Dia. Discharge, 20" Cyclone Diameter, 48" Tall"

[Bill Blackburn]

Thanks Allan - I am getting it know. I missed the "PS" line in his second post I see now. I was trying to figure out how you knew what it was
It musta looked like an octopus in need of an arm huh. 5 bags must = true space hog too.

Only a 2hp blower? gets more interesting the more I look at it I guess.

[Anthony Whitesell]

Thanks Allan - I am getting it know. I missed the "PS" line in his second post I see now. I was trying to figure out how you knew what it was
It musta looked like an octopus in need of an arm huh. 5 bags must = true space hog too.

Only a 2hp blower? gets more interesting the more I look at it I guess.

According to the plenum design specs, the monster's head (plenum) should be 18" wide, 9-12" tall, and 7 ft long. I just don't have the space for that. Even a 3-2 design would take all the space I have for a DC and leave no room for the unit itself. Outside (either venting or mounting) is not an option for me in this house. So I was looking for information on conversion for the group with a personal motivation.

[Stephen Cherry]

How do I spec a single "cartridge" style filter?

Why not look at systems which are the same size or slightly larger than yours with a cartridge filter, and use that?

I'm an engineer also, and on my first day as an engineer, another engineer told me, "don't reinvent the wheel unless you have to; take a look at what the other guy did first".

Just a thought.

[Anthony Whitesell]

Based on all the stuff floating around about DCs and manufacturers misrepresenting the numbers, I want to double check that they did it right before I copy their mistake.

[Bill Blackburn]

based on all the stuff floating around about dcs and manufacturers misrepresenting the numbers, i want to double check that they did it right before i copy their mistake.

lmao

[Anthony Whitesell]

I'm not sure it as funny as it is sad and true.

[Jason White]

My 1-1/2HP Delta came with a huge felt bag that supposedly filters down to 1 micron. Between that and my and my ambient air cleaner, I can't imagine needing anything else (unless I build a bigger shop someday).

The system I acquired was originally designed to use 5 6ft 12" diameter shaker bags for filtering. This may be a simple question. How do I spec a single "cartridge" style filter? I was thinking that since the total surface area of the original bags was 2700sqin or almost 19sqft; all I need to do is identify a filter with atleast that much surface area and an inlet the same size as the blower outlet. In the world of dust collection, could this be that simple?