Seasoning filters

[Rod Nikkel]

When using new canister filters (Wynn or Farr type), have people found they needed to be "seasoned" (ie. caked with dust) before they worked at the level they were supposed to? This page on the Wynn sitehttp://www.wynnenv.com/filter_efficiency.htm - third paragraph from the bottom - seems to imply that strongly. We are having problems with new Farr Hemipleat filters passing a LOT of dust through them. What have other's experiences been?

[Jerry Bruette]

Rod

I work for a company that makes as one of it's products...dust. It's a chemical concoction used in dry chemical fire extinguishers. We have several very large dust collectors around the company and yes we season the bags and cartridges in the dust collectors. On some filters we use talc and other filters season them selves with use.

These dust collectors also have as you state a "backflush" system on them. The purpose of the pulsators is to knock the dust off of the bags or cartridges into the hopper for removal. This is accomplished with a pulse of 85 psi air from the clean side of the filters. It doesn't seem to bother the "seasoning" of the filters. All of our dust collectors are monitored with a magnihelic which measures the pressure differential from the clean side of the filter to the dirty side. We must adhere to DNR and EPA discharge standards.

As long as you don't pulse or "backflush" your filters too often I think you'll be o.k.

Hope my rambling helped.:)

Jerry

[Alan Schaffter]

Jerry- aren't your filters designed to protect the environment as opposed to cleaning the air so it can be recycled to the workplace?

Seasoning will improve filtration for sure, but it reduces flow, and that reduces the CFM at the source which is what is important to woodworkers so is somewhat counter productive.

Filters are a lose-lose situation when you are creating large amounts of dust with particles from less than a micron to over 100 microns only inches from the woodworker- the better they filter the more they reduce airflow and collection at the source. The only way around this is high CFM and either discharging outside or extremely large filter area.

[Jerry Bruette]

Jerry- aren't your filters designed to protect the environment as opposed to cleaning the air so it can be recycled to the workplace?

Seasoning will improve filtration for sure, but it reduces flow, and that reduces the CFM at the source which is what is important to woodworkers so is somewhat counter productive.

Filters are a lose-lose situation when you are creating large amounts of dust with particles from less than a micron to over 100 microns only inches from the woodworker- the better they filter the more they reduce airflow and collection at the source. The only way around this is high CFM and either discharging outside or extremely large filter area.

The dust collectors I'm refering to are very high cfm and a large filter area. One of our dust collectors has over 300 bags in it and the bags are over 6 feet long and 6 inches in diameter. The fan is over 5 feet in diameter.

Our newest dust collector does recirc the air back into the plant for a huge cost savings during the winter.

[Alan Schaffter]

The dust collectors I'm referring to are very high cfm and a large filter area. One of our dust collectors has over 300 bags in it and the bags are over 6 feet long and 6 inches in diameter. The fan is over 5 feet in diameter.

Our newest dust collector does recirc the air back into the plant for a huge cost savings during the winter.

Those filters are probably in an external bag house where they are cleaned with a shaker and/or pulsed air on a regular basis. If you work the numbers 300 bags measuring 6' long by 6" in diameter works out to only about 350 sq. ft. of filter area- just a little more than one of my Farr style Wynn 9L300BLs. What kind of plant and what kind of dust? That makes a difference too. If you are cleaning the air and not trying to capture dust right at the source with that kind of filter area you can afford to "season." For a little home DC, while seasoning reduces the tendency of many bag filters to be nothing more than "dust pumps," at the same time it reduces the amount of dust collected at the intake- at the machine, right where the woodworker is breathing it. That is why I maintain for the home shop, unless you have a lot of surface area and can clean them often, trying to use most filters to recycle the air back to the shop is a lose-lose proposition.

[Jerry Bruette]

Alan

You're correct the filters are in an external bag house that is pulse cleaned on a regular basis, some bag houses are pulsed by a timer and some are pulsed using the magnahelic reading.

Maybe I'm working the numbers wrong but 3.14 x .5 x 6 = 9.42 sq. ft.per bag filter 9.42 x 300 =2826 sq.ft. total filter area.

I'm not sure if you're familiar with the dry chemical in a fire extinguisher but it's like flour, for a particle size comparison. I don't think any of it is sub micron in size.

Other than a cyclone or other device to capture the bulk of the dust and then a sub micron filter to catch the rest is there another way to clean the air in a shop? It's like Mr. Dysons ad on TV for his vacuum cleaner. The more dust you catch the more your filter plugs, the more your filter plugs the less air you move, the less air you move....well we know where this is headed.

Jerry

[Alan Schaffter]

Alan

You're correct the filters are in an external bag house that is pulse cleaned on a regular basis, some bag houses are pulsed by a timer and some are pulsed using the magnahelic reading.

Maybe I'm working the numbers wrong but 3.14 x .5 x 6 = 9.42 sq. ft.per bag filter 9.42 x 300 =2826 sq.ft. total filter area.

I'm not sure if you're familiar with the dry chemical in a fire extinguisher but it's like flour, for a particle size comparison. I don't think any of it is sub micron in size.

Other than a cyclone or other device to capture the bulk of the dust and then a sub micron filter to catch the rest is there another way to clean the air in a shop? It's like Mr. Dysons ad on TV for his vacuum cleaner. The more dust you catch the more your filter plugs, the more your filter plugs the less air you move, the less air you move....well we know where this is headed.

Jerry

oops you are right! I was only off by a factor of 8! :D

The various dry chemicals were chosen because they are inert and very fine so blanket and smother the burning object - just what you would want IF you wanted to season a filter. I've heard of folks using corn starch too. There was even an article in FWW or one of the other WW magazines that recommended this procedure!!!

There is no way I know to collect the volume of air needed to limit dust escaping and expanding from the source machine, carry it along duct work, and filter it so it can be returned to the shop other than by using massive amounts of filter capacity . . . if you want to return the air to your shop. If you are just removing small amounts of ambient fine dust and don't need CFM at the source, electrostatic and HEPA filters work pretty well.

The best option to maintain max CFM at the source is to separate out the bulk and discharge outside with no filter. You pay an energy penalty, but it is not bad in a small shop if you don't run the DC continuously. The air being pumped out has just a small fraction (1/1000) of the thermal mass as the shop and its contents.

Even a Dyson passes some fine dust- just no one has challenged them on it. The Dyson works fairly well because it operates in generally a benign environment. Its mini-cyclones have higher velocity and better separation of small/light dust, the dust is stationary so it doesn't need to collect a large volume and catch dust being hurled into the air by a saw/planer/sander, etc., and doesn't have the SP overhead of ductwork. When we moved to our new house- I went with a centralvac that is in the garge- most standard vacs, either have terrible suction after the filter bag clogs or are dust pumps.

A few manufacturers over the years tried to sell water separator vacs- they obviously never used a straw to blow smoke into a glass of water- a lot of the smoke stays in the air bubbles until they burst at the surface and escape. The dust that was collected in the water made a muddy mess that was worse than filter bags to clean! :eek:

[Rod Nikkel]

Alan, while filtering may be a lose-lose deal (and we agree), at -40 degrees, the biggest loss is heat and dollars to reheat. We own a Clear Vue, and at 1400+ CFM, it will totally replace the air in our shop in less than 4 minutes, and because this is our business, it runs 4 - 7 hours a day in the winter. I know it forms a "racetrack" from the open window to the machine being suctioned, but since that is where we are working, it gets pretty darn cold! So we work outside as much as possible in the summer and vent outside from the large machines, but have to use filters in the winter. We use a large sander a lot as well as a carbide carving disc on a side grinder in a special "dirty room" (6 x 8) made for that purpose even more. I believe we make a lot of fine dust with these compared to what is commonly made by a hobby woodworker.
We have had a system with 2 of the old style Camfill Farr filters with the air flowing inside to out like the Clear Vue and other DCs suggest. The problem is with the amount of fine dust we make and the difficulty and time spent cleaning in the inside of the filters. We decided to build a box where we can filter the air outside to in, the way they were meant to work, which would make cleaning much easier and more efficient. We have also figured out a way to back flush, not as the professionals do, but simply by hooking up the outflow of the cyclone (making sure it is only sucking CLEAN air) to the outflow side of the filters one at a time while blocking the other one. The normal inflow tube to our filter box will be temporarily hooked up to our outside vent. We figured that if we put a few minutes of air from the cyclone "backwards" through the filters once a month, that would do a much more efficient job cleaning them than we do with a compressor and vacuum. We hope that most of the dust will vent outside. Anything else we can vacuum from the inside of the box, and then connect it to run normally again. Comments on our idea?
Anyway, we can't use our old filters because they are very dirty on the inside now, so we bought the new, improved model from Camfill Farr, and are getting horrible readings through the filters. It has had about an hour max collecting from the bandsaw (readings over 2000 of the 1 micron via our Dylos meter) before we switched to venting back outside, and about 5 minutes testing from the grinder in the dirty room (readings over 12,000 which tells you the relative amount of fine dust produced).
So, our question is - has anyone tested the Wynn or Farr filters when they were brand new? Do they pass more dust than their literature claims until they are "seasoned" or did we just happen to get two defective filters? Or is there another answer we haven't thought of?

[Alan Schaffter]

There was a big thread (a big pi_ _ ing contest) here a few years ago, involving Bill Pentz, Robert Witter (Pres. of Oneida), Ed Morgano (ClearVue), Rick Wynn (Wynn Environmental) and I believe maybe Shiraz Balolia (Pres. Grizzly) and others. The issue was filter specs, testing and testing standards, and manufacturer's claims. Though I don't think anything was ever resolved, it sure points out there is a lot of uncertainty about filter performance.

I am wondering if you don't have damaged or poorly manufactured filters. There are two areas where a new filter can leak. One of course is if there is damage to the pleats, the other at each end of the pleats. Typically manufacturers seal the ends of the pleats by potting them is some latex like material. If the ends of the pleats are not properly sealed the filter will leak.

Another issue is filter design- some will not handle CFM, despite a large amount of filter area. Again, it is the lose-lose situation- if the filter is designed to trap the smallest of particles, it physically can't pass the same volume of air a filter with larger holes can with the same sq. footage of media. There is no magic in filters- air passes through tiny holes that dust can't, so when dust starts to collect in the filter, flow decreases. All filters except electrostatic ones need to be cleaned or replaced regularly- there is no way around it. That keeps the industry going- in my little town we have Camfil-Farr, Flanders, and Stanadyne factories! And cleaning (especially compressed air) often damages the filter media to the point where it is less effective stopping the fine dust.

Are you sure the high particle readings from your Dylos are caused by the filters and not ducting leading to the filters or by dust escaping from the machines themselves? The Dylos is really sensitive and is affected by any source of dust, including latent dust on surfaces which has been disturbed. I intentionally don't have a Dylos- I don't want to know what it will likely tell me! :eek: I set up my system the best I could and the best my budget would permit. It does no good to know how good or bad it is working at this point.

Something you might consider- it won't be cheap and it may be a bit awkward, but have you thought about continuing to discharge outside, but providing a source of outside take-up air at (almost connected to) each machine, for at least the heavy dust producers? Instead of pumping heated air outside you would be drawing outside air in and pumping it back out again. A bad source of take-up air can really reduce collection efficiency- remember, the CFM must be allowed end to end, and that includes the building. Think what would happen in a very well sealed small building if a DC were to discharge outside- theoretically you could have zero flow!

I clean my filters using a smaller version of what you described. Since I have two filters in parallel, I remove one and install a blank-out over the hole. Then I mount the filter on a base which I connect to the DC for reverse flow through the filter.

http://www.ncwoodworker.net/pp/data/1329/medium/P10100502.JPG

http://www.ncwoodworker.net/pp/data/1329/medium/P6290033.JPG

http://www.ncwoodworker.net/pp/data/1329/medium/P6290034.JPG

[Rod Nikkel]

The readings have been taken with the meter held right in the air stream from the filters. The reading in the rest of the shop was much lower at the time. It is coming from the filters.
Maybe I should just have paid more attention to the graph on this page: http://www.wynnenv.com/filter_efficiency.htm (http://www.wynnenv.com/filter_efficiency.htm) It is for the Wynn filters, but if I am reading it right, they will pass about 50% of the 1 micron dust when first used (scary) and that decreases for a few "loadings". I wonder what they consider a loading?
When we first started our cyclone, we were upgrading from the old 1 HP bag thing and 2" of sawdust on the floor from the side grinder so we thought it was doing wonderfully well right from the start. Now I wonder. We didn't get the Dylos till the filters had been used for a year or more, so the readings would have been much lower then.
Still wondering, has any one else tested new filters to see what they pass through?

[Jerry Bruette]

[QUOTE=Alan Schaffter;1551955]they obviously never used a straw to blow smoke into a glass of water- a lot of the smoke stays in the air bubbles until they burst at the surface and escape.[/QUOTE

Sounds like another piece of equipment for relaxing but not woodworking.:)

[Jerry Bruette]

Rod

If heat loss from your shop is a major concern is it possible to set up a air exchanger that would recover some of the heat?
I have a air to air heat exchanger in my house for controlling the humidity in the winter without out pumping all the heat outside.

Jerry

[Rod Nikkel]

I'm not trying to be argumentative. I understand what you are saying and agree. We vent outside whenever we can and this new system will make switching much easier, and we work outside whenever we can, as the attached picture shows. It wasn't set up - he was working there! We live in northern Alberta. We have long and cold winters. Say 65 degree F for a shop temp. Winter temperatures down to -40F or below, but usually at least below 10, commonly below 0 for weeks at a time. Fifty five to 105 degree F temperature difference. Total volume of air exchange comparable to total volume of shop air every 4 minutes. We really DO need to filter in the winter!!!
This is why we need filters that WORK, and what we are trying to figure out is: Will these filters work eventually, once they are "seasoned" or are they defective. Has anyone tested new filters to see if they pass a lot of dust, and how long does it take to get them working as advertised?