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Separators and Canister Filters - more harm than good?

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Forum topic by GrizzlyBagWorks posted 10-03-2017 07:14 PM 3197 views 0 times favorited 28 replies Add to Favorites Watch
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GrizzlyBagWorks

77 posts in 1374 days


10-03-2017 07:14 PM

I recently sold my Harbor Freight 2hp collector with Thein baffle and Wynn 35a cartridge after I realized how much better my friends stock Delta 50-760 (1-micron felt bag) performed. Side by side the difference was dramatic. I’ve seen the fan curves and knew the Delta 50-760 already had a leg up but once the separator was factored in on my HF unit the difference was pretty shocking.

BUT…I did have a leg up on him in terms of filtration. I boasted how the 35A filters 99.9% down to .5 after it’s ‘seasoned’. Problem is, I’m only capturing maybe 60% of what his system was. Meanwhile all that uncaptured dust is just floating around the shop. Ya, the filtration is better at my dust collector but if I’m capturing less air because of the air flow restrictions introduced by my 2-stage setup am I really better off? I’m starting to think not.

Are we making a mistake recommending these 2-stage/canister filter setups? I feel like for these lower powered dust collectors (sub 3hp) people would be better off trying to maximize airflow and reduce static pressure loss. Of course those 30 micron fabric bags have to go but 1 micron felt bags can be had for cheap.

Seems like the better approach would be to use a 1 micron felt bag (they are much easier to keep clean) then take the money saved from the filter/separator and buy an air filter like a Jet AFS-1000 that is actively scrubbing the air. Use a mask while actively cutting, then let the cleaner run for 15 minutes or so before you remove it.

Curious to hear your guys’ thoughts on this.


28 replies so far

View crank49's profile

crank49

4022 posts in 2754 days


#1 posted 10-03-2017 07:57 PM

I’ve been telling folks on here that adding a Thein baffle or a cyclone in front of the HF, or any other small single stage collector was killing the performance for over 2 years. I finally got tired of being ignored and just said to hell with it. Not my problem. I am an engineer and have designed cyclones and bag and cartridge filter systems for 40 years. They don’t want to listen, fine.

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crank49

4022 posts in 2754 days


#2 posted 10-03-2017 07:59 PM

By the way, the HF collector is not a bad machine and if the cartridge install is done properly it is a better machine.

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ArtMann

633 posts in 599 days


#3 posted 10-03-2017 08:02 PM

I own a 50-760. I absolutely do not agree with you that felt bags are easier than cartridge filters to keep clean. They are called “shaker” bags because you are supposed to be able to shake them in place to release excess dust that is clogging the filter. If you actually do that, you should be wearing a heavy duty respirator to keep from filling your lungs from the dense cloud of dust that inevitably happens. When I remove the bag to clean it, I always wear a respirator and plan on showering and changing clothes because the process is so messy. If you don’t clean the bag often, it will clog up and reduce the air flow to an unusable level. The reason I started using a Super Dust Deputy is to increase average air flow while reducing the frequency of cleaning. It worked for me.

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Fred Hargis

4646 posts in 2276 days


#4 posted 10-03-2017 09:31 PM

There are bags, and then there are bags. High quality felt bags like those form AFF are “singed” on the inside (fuzzies removed). They claim that this allows the dust cake to only build to a certain level…that which is needed for the most effective filtration. Beyond that, the excess cake is said to fall off. I had AFF bags for a while and I believe that is the way they work from my experience. I guess I would size the smaller DCs for separators at the 2 HP level with a 12” impeller (that would exclude the HF model) as the starting point. As for the ambient air cleaner, I am a big believer in them. But not for personal health, if the dust gets to the cleaner it’s already in your lungs.

-- Our village hasn't lost it's idiot, he was elected to congress.

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GrizzlyBagWorks

77 posts in 1374 days


#5 posted 10-04-2017 01:01 AM

Crank, keep up the good fight! I don’t think there are enough people discouraging these types of setups. I know I’ve been part of the problem. I posted a video a few years ago on my setup HF setup to youtube that has 130,000+ views. How many of them built the same system I don’t know but I’ve seen dozens and dozens of the same design on youtube. I think I might have to do an update.

I think the HF could be a great machine but it definitely needs a filter upgrade and with a 9.8” impeller it could see quite an improvement with a 12” swap.

Art, I agree on the headache of cleaning the bags but have you seen the inside of canister filters? The Wynn has hundreds of pleats. The pleats just get packed with dust so you have to hit them with compressed air, beat on them for ages or remove them entirely and take a leaf blower. Just vacuuming the inner surface isn’t enough.

My understanding is that that Super Dust Deputy doesn’t create that much of a static pressure loss, especially compared to a thein baffle so perhaps it’s worth it just to keep the filter cleaner. My understanding though is that is still lets the majority of really fine dust by. If that’s the case then perhaps you’re better off with a vortex type separate after the blower which has less impact on CFM. Bag changes won’t be as convenient but you’ll have greater CFM and less static pressure loss as a trade off.

View TungOil's profile

TungOil

668 posts in 278 days


#6 posted 10-04-2017 02:51 AM



I ve been telling folks on here that adding a Thein baffle or a cyclone in front of the HF, or any other small single stage collector was killing the performance for over 2 years. I finally got tired of being ignored and just said to hell with it. Not my problem. I am an engineer and have designed cyclones and bag and cartridge filter systems for 40 years. They don t want to listen, fine.

- crank49

+1. It takes energy to change the direction of matter in motion, that energy has to come from somewhere. No escaping physics.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View d38's profile

d38

23 posts in 45 days


#7 posted 10-04-2017 04:34 AM

Great timing for this post, since I’m real close to ordering a SDD and canister filter to convert my new Grizzly 2hp DC into a two stage.
Maybe its best to simply replace the upper bag with a custom made American Fabric Filter. I have 10’ ceilings, so room to go way taller than factory. An AFF bag would be better filtering with a lower micron than the Grizz factory, and larger for better airflow.
Then take the money saved and buy a large (or 2 small) whole room air cleaners.
Is this a better plan to collect as much dust as possible at the source, and keep it in the DC?

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crank49

4022 posts in 2754 days


#8 posted 10-04-2017 04:46 AM


I ve been telling folks on here that adding a Thein baffle or a cyclone in front of the HF, or any other small single stage collector was killing the performance for over 2 years. I finally got tired of being ignored and just said to hell with it. Not my problem. I am an engineer and have designed cyclones and bag and cartridge filter systems for 40 years. They don t want to listen, fine.

- crank49

+1. It takes energy to change the direction of matter in motion, that energy has to come from somewhere. No escaping physics.

- TungOil


Yes, the fan laws will get you every time.
1. CFM is directly proportional to fan speed.
2. Pressure varies by the square of the fan speed.
3. HP varies by the cube of the pressure change.
So, if you double the pressure you will have 1/8 of the CFM.
Just physics.

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Manitario

2506 posts in 2666 days


#9 posted 10-04-2017 06:08 AM

I think the problem is not the HF collectors or really any of the smaller DC, it is that we expect too much of them. Cartridge filters are great, and we should be aiming to filter the outgoing air better than the typical filtration provided by bags. As well, we all want a cyclone or pre-separator to keep the filter clean…however a small DC with a small impeller just can’t provide meaningful DC with such restriction on the outflow (cartridge filter) and on the inflow (cyclone or pre-separator). And then we further restrict the inflow by running long lengths of 4” pipe…

Not everyone can afford a 3 or more hp DC with an appropriately sized impeller. A $200 HF DC can be great (or any of the other smaller single stage DC if you accept their limitations; they don’t have the power or capacity to handle a cyclone or pre-separator like a Thein baffle or a highly restrictive cartridge filter or being connected a duct system but with portable setup and frequent filter cleanings it will do a reasonable job.

-- Sometimes the creative process requires foul language. -- Charles Neil

View Bill White's profile

Bill White

4769 posts in 3743 days


#10 posted 10-04-2017 01:18 PM

I have the felted bags (2) from Highland on my HF collector. Don’t need anything else.
Bill

-- bill@magraphics.us

View brtech's profile

brtech

991 posts in 2705 days


#11 posted 10-04-2017 01:56 PM

I am one of the inveterate castigators of separators on HF DCs. I’ve probably commented on 40 threads that adding a separator to an HF is a bad idea. I believe that the airflow through the cannister is BETTER than the bag, and I thought I’ve seen a test that confirmed that. I know my airflow increased when I upgraded by bag to the Wynn, but that was with a relatively new bag and a brand new Wynn. With the recommended cake, I think it is better also.

The insertion loss of any of the separators is significant. The work I’ve seen implies the Thein and the DD are about the same as far as insertion loss goes, but I don’t recall an actual test under realistic conditions.

Manitario, I think the Wynn 35A is a fairly decent cartridge filter, and there are few filters which have less resistance with adequate filtering capability than the Wynn. I’ve seen worse filters, but not better ones. Do you know of a filter that is less restrictive than the Wynn while still having adequate filtering for the HF DC?

I’ll always agree that more HP and bigger impellers really are required to get all the fines. I believe Pentz’ numbers.

View ArtMann's profile

ArtMann

633 posts in 599 days


#12 posted 10-04-2017 03:11 PM

I had a chance to compare the HF dust collector with the Delta 50-760 directly and unmodified when a friend bought the HF used in good condition. Don’t get misled by the horsepower fantasy. The Delta outperforms the HF by a huge margin. I don’t have the ability to compare directly now but from my recollection, the Delta with the SDD modification moves more air than the HF without it. HF may be a good buy and I might buy one for a special situation, but it isn’t a good performer compared to other machines of similar size.

View clin's profile

clin

730 posts in 779 days


#13 posted 10-04-2017 04:01 PM

There are several variables here and you’d really need to compare 2-stage vs 1-stage using the same blower. Though arguable, when designing a system, the blower should be optimized for the overall design.

The HF units are known to be low power and I think it’s a mistake to use it’s performance with a separator as the basis for general conclusions concerning single and 2-stage systems.

Don’t get me wrong, I think the OP has a point, but like most optimization problems, there’s no simple answer that says this is always the best approach. But perhaps for lower power DC systems it would make sense to chose inconvenience (cleaning a single stage filter bag often) for the higher airflow. However, I wouldn’t give up on filtering fine particles with the DC.

-- Clin

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shipwright

7717 posts in 2581 days


#14 posted 10-04-2017 09:37 PM

This is a good read for anyone thinking about HF dustcollector improvements.
http://studiograyhouse.com/harbor-freight-dust-collector-mod/

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

View Redoak49's profile

Redoak49

2794 posts in 1771 days


#15 posted 10-04-2017 11:16 PM

I would love to see the actual costs for replacing the impeller, cartridge filter and dust deputy.

Also, it would be helpful to see actual performance data.

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