Bob Dodge: Help with sizing fabric filters?

Re: Bob Dodge: Help with sizing fabric filters?

Kent in Emmaus, PA

>I'm not Bob, but I drove a Dodge a few times. Does that count?

Anyway, if you want a 4:1 (Blower CFM to Filter Media) ratio, you would divide the CFM by 4, not multiply. That gives 575 sq ft, which still seems high, but should at least fit in your shop. Maybe you could find a more realistic estimate of CFM from an actual test.

sizing fabric filters

JRutter

>I think you'll be doing fine if you get under 10 CFM/1 FT. That would be upsizing the filters from 150 SF to 230 SF, which is about 50% more fabric. The 15 HP system that I'm installing has a ratio of about 8:1.

-JR

DIVIDE by 4? Sheesh!!!

Dominic Greco in Richboro PA

>Thanks guys. Dividing 2300 CFM by 4 does give me a more realistic figure of 575 sq feet. Which is still a pretty big bag. But I was told on Wood's Dust Collection Forum that that 2300 CFM equates to a real world pressure and flow of about 1100 CFM @ 0" SP (using a 7" or 8" main duct). So it may be more like 275 sq ft. But that equates to (5) 30" diameter x 7 ft tall bags!

While I feel like a real dummy, I don't feel all that bad. When I asked the tech at Process Systems, he didn't know much either. I gave him that 2300x4 figure and he agreed with it! The regular "fabric filter guy" John was out to lunch at the time. Guess I should waited for him.

Thanks,

Dominic

Give Wynn Environmental a call *LINK*

Ken Garlock Collin County Texas

>Hi Dominic. When I built a filter system for my cyclone, I bought two pleated filter cartridges from Wynn Environmental. Each cartridge has 300 sqft surface area. The cartridge may not be usable in your system, but I did get a lot of good information.

At least take a look at their website,

Ken


Wynn filters

Re: Bob Dodge: Help with sizing fabric filters?

Jesper, Denmark

>Hi Dominic,

There is a simple rule for almost all dust filtration: Maximum 500 fpm (feet per minute) flow through the media.

If you drop this to 400 fpm, you significantly increase the efficiency.

So for 3400 cfm, you need 7 sq. ft. filter area. 10 sq. ft. would be better.

wow, are you sure about that?

JRutter NW WA

>That sounds like a number that would be useful for low pressure systems like a forced air furnace, but for wood dust collection I'll stick to <10 CFM per SF media...

Re: Bob Dodge: Help with sizing fabric filters? *LINK*

Bob Dodge

>Hi Dominic,

My sincere apologies for not getting back to you sooner. My computer died in late December (28th), and I'm still not yet up to speed with the new one. It has to go back to the shop again on Monday, arghhhhh!!!!

Dominic, the info you got is not appropriate for your situation. It's "partially" correct.

First of all, your dc isn't going to move anywhere near 2300 CFM. From what I recall, that "3 HP" Reliant, has a 12" impeller, so, you're only going to be pumping a max of 900-1000 CFM at your largest drops (6"). Most of the time, your filters will be seeing a lot less air than that, especially where you have a single 4" port on any of your machines. If you're using 4" pipe in conjunction with those hoods, you'll see even less airflow. 550 CFM would be very optimistic, even if you have a 6" main w/4" drops.

Now, you also have to consider the type of waste generated at your machines. You don't need anything even remotely close to 4:1 air-to-cloth ratio, if your waste is larger than 1 micron.

Just to give you a rough idea, the commercial industrial 3 HP dc's, generally go with roughly 40 sq.ft. of 16 oz. needle-felt. Those dc's are monsters compared to yours. Those things are pulling upto 1400 [email protected]" SP. I'll give you a link to an example down below. Kraemer dust-collectors, use roughly the same sizing.(39 sq.ft.) My dc is a Pyradia/Belfab 2 HP unit with a 12.5" impeller, and it has 32 sq.ft. of filter surface, and the performance, is excellent. Again, that is with a 16 oz. needle-felt.

You have to remember that these filters are a totally "different animal" compared to the cheap so-called 1-micron filters found on consumer-model dc's. It's not even close.

In the consumer-model dc's, the Delta filters are quite nice, and they too, size their filter at 41 sq.ft. for a 12" impeller dc (Delta 50-761 2 HP). If the Process filter-bags are genuine 16 oz. needle-felt, they're probably superior to the Delta filters.

My recommendation to you is, go with the tallest filters your shop ceiling-height can deal with, and over-size the diameter "if you feel it's affordable or desireable". Frankly, I'm quite certain you'll be happy with something in the 40-50 sq.ft. range.

Air-permeability with a quality 16 oz. needle-felt filter is VERY high, generally in the 55-60 CFM/sq.ft. range, so, pressure-drop is very low. I would ONLY consider going with a larger surface area if I was hooked-up to a dual-drum sanding machine, or, another machine which produces large volumes of extra-fine waste. For the average home-shop, you just don't need it. The only down-side, is that your filters may require more frequent cleaning if you produce fine-waste. Over-sizing the filters, will reduce that down-time.

Frankly, if it were me, and especially considering how inexpensive the Process filters are, I'd buy a second set as "spares". Why? Because, if I was in a situation where I was very busy, and didn't want any down-time for cleaning, I could simply install a clean set and keep going. I'd clean the dirty filters later, when it's more convenient.

The filters on my dc are the Pyradia/Belfab 16 oz. needle-felt filters, and those cost $200./ set.(Canadian) The Process filter-bags are an absolute steal at the price they're asking.

Bob


Belfab LW 3 HP DC

Thanks Bob

Dominic Greco in Richboro PA

>Bob,

Thank you for responding. I hope your having better luck with your computer! Having to start from scratch is not a lot of fun.

You wrote:

"My recommendation to you is, go with the tallest filters your shop ceiling-height can deal with, and over-size the diameter if you feel it's affordable or desirable. Frankly, I'm quite certain you'll be happy with something in the 40-50 sq.ft. range."

My idea was to have the blower discharge into a 90 degree elbow that in turn is connected to the filter bag. The bag would have no bottom, but be clamped around the mouth of a 55 gallon drum. (see diagram attached)

Looking at the spreadsheet I made up and using the flow rates you mentioned above, I can use (1) 42" dia x 4.67' tall filter bag. This which would give me roughly 50 sq. ft. of filter media. My calc is just for the cylindrical area. To get exact numbers, I need to get the areas of the conical sections above and below the cylinder. But I think it gets me in the ballpark.

See ya around,

Dominic

Re: Thanks Bob *LINK*

Bob Dodge

>Looks like the Kraemer E-Series dc's


Kraemer E-Series dc's