replace a single 5 micron bag with two 1 micron bags on a HF unit

[OLDCHIP]

Hello All,

I have a few questions regarding filter bags on a standard HF unit that came with a 5 micron bag on top, and a plastic bag in the lower position.  I have the JPThien duct collector upstream of the HF unit. 

Because Phil's tool works so well, after a few hours of cutting and some sanding, I have less than one cup of dust in the plastic bag.  I didn't do a real good job of cleaning the plastic bag out before placing Phil's collector in service so, I'm sure that most of that dust was the result of use before adding Phil's collector.  And, I do measure several inches in the dust collector bucket and this proves that the Thien collector works.

I would like to upgrade to 1 micron bag on top (20x33).  Is there any reason (other than cost) that I should not replace the plastic bag (20x36) on the bottom with second 1 micron bag?  My reasoning is that because I'm going to a filter that is significantly finer, I should increase the filter surface area so that the air flow rate is not reduced (i.e. increase backpressure by changing to a single 1 micron bag).

Looking at Highland, Klinspor's, & WoodTek, their filter bag prices range from near 30 to 65$ each bag (price includes shipping).  Is there any consensus that any of these suppliers (or another of the many other providers) provide a better product as compared to their peers?

Many thanks for your thoughts,
Paul

[phil (admin)]

I don't have a lot of experience with the felt bags, but I imagine two would be about twice as good as one, when it comes to CFM.

[RonS]

Put a Wynn filter on the top and keep the plastic bag on the bottom, You can see this setup on a lot of HF DC on Phil's  site.

Go to Wynn's website and see how to do it.

http://www.wynnenv.com/35A_series_cartridge_kit.htm

[OLDCHIP]

Ron,

I like the look of that Wynn filter idea and will pursue it.  The microns are likely better from the start.  Cleaning should be simpler (puff some air backwards thru it, or build their "pleat beater" device).  Probably more than twice the filter area as compared to the 2 felt bag idea that I started with.  Cost looks to be a tad more compared to less expensive bags, but is more than competitive when compared to higher quality felt bags.  Many good reasons to put one on the unit.   I'd probably come out ahead with one of these.  Assuming that the installation is as simple as it looks, this will be a good move for the long haul.

Many thaks for your suggestion,
Paul

[DarthVader]

installation is simple on wynn cartridge filters with the hf unit. ive had mine for a couple years now, still works very well.

on a side note, what about a 1 micron bag on the bottom with a wynn on top? would that further increase flow over the plastic?

[alan m]

if you put a bad filter on the bottom and a good one on the top all the air will take the leaste resistance and go through the bottom bad filter

[DarthVader]

ahh...makes sense

[OLDCHIP]

I purchased the 'upscale' Wynn 35A filter; it should arrive Wednesday 23 Jan.  Spoke with Mr. Dick Wynn, he says they sell many 35A units for the HF dust collectors.  This particular one has about 270 sq ft of filter area; the smallest sq ft on the 35A is 100; compare to about 30 or 35 sq ft on a felt bag.  He said that even though the spun bond filter is 'washable', he does not recommended to get the wood fibers wet as they would get rock hard like cement.  To clean it, you can use a palm sander on top of the filter can on it's side to vibrate the dust loose, or shop vac it from the inside, or blow compressed air backwards thru it; the fine dust falls to the plastic bag, then dispose of it.  He thought that installation might take as long as 15 or 20 minutes; pretty straight forward.  It ought to be a long lived filter at the rate I use it (say, 10 or 15 or so hours each week).   In the end, I spent about 50$ more than I had anticipated, but given that it is a 0.3 micron filter, I'll feel better about it; it will also have less back pressure than the pair of 1 micron felt bags (more sq ft by a factor of about 9). 

Then, I did a test with the current 5 micron bag.  After dumping out Phil's collector to get heavier chunks, I added some belt sander dust; total volume was more than a gallon, but less than 1.5 gallons.  I force fed the collector and the HF unit using the original 5 micron felt bag.  As expected, the heavy stuff stayed in Phil's collector, and some of the very fine dust went thru to the plastic bag on the HF unit.  To be fair, this was really a seriously biased test designed to choke the system out; I doubt that anyone would generate that volume in the 4.009 seconds (sic) it took to suck it into the system.  The unexpected upshot of this is that there was enough back pressure generated by the 5 micron felt bag that some of the fine dust was forced out of the air pump discharge flange (just before the spiral plastic hose).  This is good to know because it suggests the possibility that at least on the HF units, the discharge  flange (horizontal one with a rectangular neoprene gasket) should probably be sealed at time of assembly.

Forgive me as I'll be slightly bold here because I see this as a health issue, so, pride aside:  it might be that any unit (regardless of the paint color har-har) that looks similar to the HF unit, should have that horizontal discharge flange siliconed simply because it is a joint that can be subject to vagaries of different bolt torques, flange irregularities, and could see back pressure as the filter becomes coated with dust, etc.  I need to repeat the choke test and prove system integrity before using the wynn 35A and I also need to validate the  suction flange joint as well.

To seal the discharge flange it took me about 15 minutes and a squirt of (Permatex Blue) silicone.  I'm thinking that if I did not figure out the 'leak' before adding such a fine filter, I might never have known.  Yah, I will continue to use the respirator until I get real confident in this system.

I think that with Phil's collector in series with the improved HF unit complete with Wynn 35A filter on top, and the plastic bag on the bottom, all will be about as well as can be.  I will do a second 'choke test' before and after I install the Wynn filter to prove system integrity.  And, of course, I'll repost when it is together and also provide any observations reagrding dust leakages, etc. 

My next bright idea is to make a differential pressure gauge using a column of water as an indicator of when it is time to clean the (felt / paper / poly ) filter elements...way too much time on my hands...

Thanks one and all!

[phil (admin)]

Sealing those joints is a very good idea.  I often use electrical tape (the plastic stuff) to seal joints.  A few wraps back and forth is all it takes.  And if I want to remove it I can do so and it rarely leaves much residue.