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fungusmuncher
rabbit chaser



Registered: 03/07/09
Posts: 1,068
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Re: So you're building a flowhood? [Re: mushpunx]
#26724767 - 06/06/20 06:27 PM (3 years, 8 months ago) |
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Having a hard time wrapping my head around this, will this filter work? https://www.amazon.com/gp/product/B074KMNZW3/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 ; I just don't want to buy it and not be able to match a fan. I asked the seller about a flow rate chart but haven't heard back yet.
edit: I found some info on the companies website that says "125 fpm @ 1.0 in w.g". So at 100 fpm would it be .8 in w.g? So would I need a fan that blows 400cfm @ 1.2 in w.g with the prefilter included? I don't even know if this makes sense, not making much to me. Any help would be appreciated, don't know if I should grab one before they are gone.
Edited by fungusmuncher (06/06/20 08:15 PM)
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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That will work in a pinch 
125fpm is fine, just as long as it's 100fpm minimum and not unreasonably high like 500fpm or something, ballpark is fine. Grab that filter up and add .4SP for the prefilter if you're using a standard 1" thick furnace filter. If your prefilter doesn't have a label with it's SP just look it up on their site if you want to be more accurate.
I don't know what it would be at 100fpm because I don't have the chart so just assume 1.4"SP @ ~400+CFM will do.
Edited by Stipe-n Cap (06/06/20 10:27 PM)
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fungusmuncher
rabbit chaser



Registered: 03/07/09
Posts: 1,068
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Re: So you're building a flowhood? [Re: Stipe-n Cap]
#26725789 - 06/07/20 07:07 AM (3 years, 8 months ago) |
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Thanks for the help, it's starting to make sense I think. I noticed a previous buyer posted a picture of the spec sticker. It says Resistance: .7 in w.g. Test Flow: 500cfm.
So does that mean that when 500cfm is pushed through the filter the static pressure is .7 in w.g?
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Re: So you're building a flowhood? [Re: Stipe-n Cap]
#26725929 - 06/07/20 08:37 AM (3 years, 8 months ago) |
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I see many of people buying the 12 inch deep filter and thinking they'll get laminar flow.
Anyone trying to achieve laminar flow should buy the 6 inch deep filter.
The 12 inch deep filter has half the resistance as the 6 inch.
3 inch deep filter has twice the resistance as the 6 inch.
The 6 inch with the right blower you can achieve the 1.0 inch of static pressure in the plenum area of your flow hood. Without this pressure the air will not exit your filter at the same parallel velocity therefore the resultant would be turbulent air that could vortex contaminates into your work area..
GO FOR THE FLOW.. THINK LAMINAR
my two cents...
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fungusmuncher
rabbit chaser



Registered: 03/07/09
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Re: So you're building a flowhood? [Re: micelio]
#26725984 - 06/07/20 09:06 AM (3 years, 8 months ago) |
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The filter I was looking at is 5 7/8 thick. Just trying to figure out the numbers to match a blower.
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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This Is the blower you need. It's a little over size but that's a good thing. You can control the airspeed by restricting the airflow at the intake of the filter with wax coated cardboard or sheet metal.
https://www.grainger.com/product/DAYTON-OEM-Blower-1TDU2
Dayton 1TDU2 This Is the blower Fungi Perfecti supplies with their 2x2x5.8 laminar flow hood.
I assume It's the 2'x2' your looking at?
E-bay has this blower.. https://www.ebay.com/itm/NEW-Dayton-1TDU2-Blower/293602809265?hash=item445c1755b1:g:ucIAAOSwPGNe2Uah
Edited by micelio (06/07/20 09:37 AM)
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fungusmuncher
rabbit chaser



Registered: 03/07/09
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Re: So you're building a flowhood? [Re: micelio]
#26726206 - 06/07/20 10:37 AM (3 years, 8 months ago) |
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Thanks, that is the blower that I was looking at. So would I build it then test the flow with an anemometer? Then restrict the intake until the flow is around 100fpm?
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: So you're building a flowhood? [Re: micelio]
#26726311 - 06/07/20 11:18 AM (3 years, 8 months ago) |
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Quote:
micelio said: I see many of people buying the 12 inch deep filter and thinking they'll get laminar flow.
Anyone trying to achieve laminar flow should buy the 6 inch deep filter.
The 12 inch deep filter has half the resistance as the 6 inch.
3 inch deep filter has twice the resistance as the 6 inch.
The 6 inch with the right blower you can achieve the 1.0 inch of static pressure in the plenum area of your flow hood. Without this pressure the air will not exit your filter at the same parallel velocity therefore the resultant would be turbulent air that could vortex contaminates into your work area..
GO FOR THE FLOW.. THINK LAMINAR
my two cents...
You can have laminar flow with 12", many cabinets utilize 12" filters. Are you suggesting that anything other than 6" is ineffective?
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Re: So you're building a flowhood? [Re: Stipe-n Cap]
#26726378 - 06/07/20 11:44 AM (3 years, 8 months ago) |
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You can get laminar flow with the 12 inch deep filter. remember the 12" deep has half of the resistance as of the 6" deep.
Without resistance you've never build pressure in the plenum. Resistance Is your friend.. Without pressure In the plenum the air from the blower would tract to the area of less resistance. That would result to turbulence In the work area.
12 inch deep hepa filters deliver a high rate of volume, they're good for keeping rooms supplied with sterile air like hospital and labs...
For work station flow hoods the 6 inch deep filter Is more practical.
I think you did an excellent job on this thread I am sure It'll help many of people out. I have this thread bookmarked.
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: So you're building a flowhood? [Re: micelio]
#26726395 - 06/07/20 11:52 AM (3 years, 8 months ago) |
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Yes you're right, the filter needs to generate resistance in order to build a plenum of pressurized air behind the filter to achieve uniform flow across the filters surface. Could you provide a source that clearly illustrates that the minimum requirement is 1" W.g, please.
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Re: So you're building a flowhood? [Re: Stipe-n Cap]
#26726500 - 06/07/20 12:28 PM (3 years, 8 months ago) |
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Before electronics water gauge was made out of a glass tube in the shape of a U... one end of the tube mounted inside the plenum and the other section mounted on the outside where you can get a visual of the U. The bottom of the tube was filled with water. when the plenum was pressurize the water level would rise in the tube. If It rises one inch you would have 1 inch of static pressure or 1 inch wg.
With an Anemometer you can see If your getting the same constant airspeed throughout the face of your filter and at what wg.
What is laminar air flow? Laminar airflow is defined as air moving at the same speed and in the same direction, with no or minimal cross-over of air streams (or “lamina”).
By contrast, turbulent flow creates swirls and eddies that deposit particles on surfaces randomly and unpredictably.
Edited by micelio (06/07/20 12:30 PM)
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: So you're building a flowhood? [Re: micelio]
#26726519 - 06/07/20 12:38 PM (3 years, 8 months ago) |
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Yes but but that doesn't clearly articulate that laminar flow cannot be achieved below 1"W.g. If what you're saying is that 1" of resistance is required as a minimum to create laminar flow then there must be an engineering chart to represent this. Free air is obviously insufficient but at what point has enough friction been generated to build a sufficient plenum to create uniform flow. I doubt that it's 1"w.g but the burden of proof is on you, I'd be very interested to know, not only that but that information would be valuable to this thread.
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micelio
Song of Silence


Registered: 04/22/14
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Re: So you're building a flowhood? [Re: micelio]
#26726542 - 06/07/20 12:44 PM (3 years, 8 months ago) |
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Oh..! I forgot to mention and this Is my opinion.
Laminar flow Is not like a light switch you turn and off at 1 sp./wg.
I believe you can have laminar flow at 0.8 static pressure and It just gets cleaner and more define as the pressure increases.
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: So you're building a flowhood? [Re: micelio]
#26726545 - 06/07/20 12:45 PM (3 years, 8 months ago) |
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Oh my.
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Re: So you're building a flowhood? [Re: micelio]
#26726562 - 06/07/20 12:52 PM (3 years, 8 months ago) |
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I love laminar flow..
Why Laminar Flow is AWESOME
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Quote:
fungusmuncher said: The filter I was looking at is 5 7/8 thick. Just trying to figure out the numbers to match a blower.
Thickness is irrelevant, follow the steps above and don't over think it. Thickness wasn't included in the template for a reason.
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Quote:
fungusmuncher said: Thanks, that is the blower that I was looking at. So would I build it then test the flow with an anemometer? Then restrict the intake until the flow is around 100fpm?
What allot of people do Is use a bic lighter at about 5 inches from the filter.
You want the flame to be at 45 degrees angle. If the flame blows out choke off the intake a little more..
You know It's not an exact science thing.
Some like It fast and some like It slower. It's a preference thing.
The anemometer Is not necessary.
You'll find yourself having so much fun working in front of your hood.
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fungusmuncher
rabbit chaser



Registered: 03/07/09
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Re: So you're building a flowhood? [Re: micelio]
#26731646 - 06/09/20 02:40 PM (3 years, 8 months ago) |
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Damn the 1tdu2 seems like overkill for a 24x24. I see people building a 48x24 with the same blower. The label on the filter says the resistance is .7 in w.g, with a prefilter that would make it 1.1. At 1.1 in w.g the 1tdu2 will be around 900cfm, more than double the required airflow.
Or am I looking at this wrong?
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Gan
Wielder of Narya



Registered: 08/26/19
Posts: 927
Loc: Valinor
Last seen: 6 months, 15 days
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Yo p9, you seem to know your shit about filters so you care to clear something up for me?
I just got a 24x36 HEPA from FP (got tired of looking and just bit the bullet). I asked for them to provide me with a spec sheet for the filter. Instead they either dodged the questions or didn't understand it and instead replied with this: "The recommended CFM for the 36x24 HEPA filter is 896. This is the minimum requirement for proper filtration."
What exactly does that mean? Does that mean your blower has to put out at least 896 CFM on the backside of the filter to provide proper filtration? Or does it mean something crazy like you have to have 896 CFM coming out the frontside of the filter for proper filtration? Cause of course that'd be too fast for my size filter.
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micelio
Song of Silence


Registered: 04/22/14
Posts: 1,547
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Re: So you're building a flowhood? [Re: Gan]
#26731933 - 06/09/20 04:42 PM (3 years, 8 months ago) |
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