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Kako
Stranger
Registered: 01/22/12
Posts: 5
Last seen: 10 years, 5 months
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Flow Hood Calculations Question
#15703598 - 01/22/12 06:55 PM (12 years, 11 months ago) |
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Hey guys. With the help of a friend and these forums, I have my first PF Tek batch going. What I would like to do is create a flow hood to make our future batches and grain transfers (when we get into that) easier and cleaner.
I've been looking through the forums and online for filters and blowers and would just like someone to go over the math and my choices with me. I'm interested in a 18"x24" Hepa filter. Not too small or too big I believe and should cover plenty of surface area while not being too short either.
I'm thinking of getting the 18 x 24 x 5-7/8 (99.99% HEPA wood) from: http://www.filtera-b2b.com/businessfilters/hepa.htm
I don't know what the difference between the wood or metal frame filter is except in the price, $123.66 vs $173.02. If it's absolutely necessary to get metal, I will if there's a good enough reason.
Looking at its specifications which is located here: http://www.filtera-b2b.com/businessfilters/PDFfiles/HEPABrochure09072004.pdf it has a static pressure of roughly 250Pascals.
Using the information on this page, I found the area of my filter which is 2ftx1.5ft = 3ft^2. Now that I know that I found the required air speed of my filter which is (100 ft/min)*(3ft^2) = 300ft^3/min = 300cfm.
If I decide to use a prefilter also, the combined static pressure of the Hepa and prefilter will be roughly 1 + .2 = 1.2. So the blower must deliver 300cfm( 300cfm * 1.7 = 510m^3/hr) of air at a static pressure of 1.2".
Now that I know that information, and if that's correct, I can start looking for blowers. This is what's been the overwhelming part for me, finding the right blower. I took a look at Grainger but it looks like I'm going to be dropping upwards of $200 for the blower alone. The tech specs at the Grainger page don't show the static pressure above .8 for most of the blowers so I'm having to guess which one would likely suffice by looking at it's strength at .7 or .8 and hoping the fan cfm output will still be reasonable at 1.2.
Here are some blowers that I've found: http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT8 http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT9 http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT4 http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT5 http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDU1
Ontop of those, you have the ones from www.businesslights.com which would cost me half the price of fans from above but as someone elegantly said on these forums, the valuline fans are the McDonalds of inline fans...
Like I said, I'm a little overwhelmed from the choices. Hopefully I can have this ordered in the next couple of days. All I ask is if someone can go over my math and choices and tell me if I'm on the right path. Thanks for all the help you've given already!
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DrCrumbs
Alpha Blue


Registered: 10/25/11
Posts: 1,619
Loc: Gili Trawangan
Last seen: 5 years, 2 months
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Re: Flow Hood Calculations Question [Re: Kako]
#15703899 - 01/22/12 07:41 PM (12 years, 11 months ago) |
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so cool
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: Kako]
#15704906 - 01/22/12 11:09 PM (12 years, 11 months ago) |
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I'm using a Grainger 1TDU2 with a 36" x 24" HEPA - those Grainger blower specs show all the psi from 0.0 to 8.0 in increments of 0.1. You should be able to get a decent enough interpolation of what the CFM for any given blower will be at 1.2 psi by creating a graph from the given data for the blower and projecting a smooth curve through it.
I decided to get a blower which delivered more than what was necessary according to the calculations and to use a solid state speed controller to get it exactly right using the flame test. This also lets me crank it up to max in order to scrub the air in the room for an hour or two, and then just throttle it down for the laminar work.
I really like the heavy duty aluminum frame around the filter, wood does have pores which contams can hide in, but you could always put a good sealer on it to make it non-porous.
While making mine I trimmed the heavy plastic bag that the filter came in and taped it down along the edges on both sides in order to keep dust out of the filter during construction, then just removed it before closing the cabinet up.
Good luck - you'll love having a flow hood!
Edited by psychotropical (01/22/12 11:42 PM)
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Big_Sexy
LoveMonger



Registered: 10/04/11
Posts: 602
Last seen: 12 years, 22 days
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Quote:
psychotropical said: I'm using a Grainger 1TDU2 with a 36" x 24" HEPA - those Grainger blower specs show all the psi from 0.0 to 8.0 in increments of 0.1. You should be able to get a decent enough interpolation of what the CFM for any given blower will be at 1.2 psi by creating a graph from the given data for the blower and projecting a smooth curve through it.
I decided to get a blower which delivered more than what was necessary according to the calculations and to use a solid state speed controller to get it exactly right using the flame test. This also lets me crank it up to max in order to scrub the air in the room for an hour or two, and then just throttle it down for the laminar work.
I really like the heavy duty aluminum frame around the filter, wood does have pores which contams can hide in, but you could always put a good sealer on it to make it non-porous.
While making mine I trimmed the heavy plastic bag that the filter came in and taped it down along the edges on both sides in order to keep dust out of the filter during construction, then just removed it before closing the cabinet up.
Good luck - you'll love having a flow hood!

Damn man nice flow hood, what did that baby cost to build?
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: Big_Sexy]
#15706127 - 01/23/12 08:56 AM (12 years, 11 months ago) |
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Let's see... Code:
1 HEPA filter $330 (w/shipping) 1 Blower 320 (w/tax - local) 2 Sheets 1/2" Sandeply 70 1 Speed controller 33 Misc hardware, glue, silicone & paint 14 ___ $767
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Big_Sexy
LoveMonger



Registered: 10/04/11
Posts: 602
Last seen: 12 years, 22 days
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Wow that's a lot of money, youre not a very thrifty shopper
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flossabe
Curious



Registered: 12/28/11
Posts: 29
Loc: USA
Last seen: 10 years, 4 months
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Re: Flow Hood Calculations Question [Re: Big_Sexy]
#15706195 - 01/23/12 09:35 AM (12 years, 11 months ago) |
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Just so I understand the situation, you are wanting to make a sort of vent hood, such as one on a cook top, to have cleaned air passing over the work area. You are wanting to flow the air down or across the work area? Will you be venting this into a closed or open space? (like a box for closed/...anything but a box for open lol) Can you provide a schematic of what you want? Will there be any other ducting leading to or from the filter element? We will get ya set up and the wood vs. metal is just an option for how sturdy you want the filter to be and/or super high humidity low flow environments so my opinion is that wood would be fine.
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: flossabe]
#15706477 - 01/23/12 10:53 AM (12 years, 11 months ago) |
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Quote:
flossabe said: Just so I understand the situation, you are wanting to make a sort of vent hood, such as one on a cook top, to have cleaned air passing over the work area. You are wanting to flow the air down or across the work area? Will you be venting this into a closed or open space? (like a box for closed/...anything but a box for open lol) Can you provide a schematic of what you want? Will there be any other ducting leading to or from the filter element? We will get ya set up and the wood vs. metal is just an option for how sturdy you want the filter to be and/or super high humidity low flow environments so my opinion is that wood would be fine.
He's doing calculations for a laminar flow hood: Laminar Flow
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: Big_Sexy]
#15707217 - 01/23/12 02:19 PM (12 years, 11 months ago) |
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Big_Sexy said: Wow that's a lot of money, youre not a very thrifty shopper 
Lol, could be. But I intend to use this tool for many years and I never skimp on tools. The Grainger blowers have excellent reputations and warranty and the Fungi Perfecti HEPA filters are custom made specifically for mycologists - they wear well in humid environments. I used the Sandeply over regular plywood because it has a tighter density - less porosity, and the solid state controller is rated at 8amps to reduce any chance of overheating. There's a method to my madness...
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 10 months
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Quote:
The tech specs at the Grainger page don't show the static pressure above .8 for most of the blowers so I'm having to guess which one would likely suffice by looking at it's strength at .7 or .8 and hoping the fan cfm output will still be reasonable at 1.2.
Just look for a blower which delivers around 350 cfm at .8 W.G. and it will be close enough at 1.2 W.G.
I'd suggest going to a heat and air shop in your town to see if they have a scrap blower from an old furnace unit. They'll probably give it free or very cheap. Around 1/3 to 1/2 hp will get you in the neighborhood. RR
-------------------- Download Let's Grow Mushrooms
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"I've never had a failed experiment. I've only discovered 10,000 methods which do not work."
Thomas Edison
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flossabe
Curious



Registered: 12/28/11
Posts: 29
Loc: USA
Last seen: 10 years, 4 months
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Re: Flow Hood Calculations Question [Re: RogerRabbit]
#15709310 - 01/23/12 10:10 PM (12 years, 11 months ago) |
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Did you really post a link to explain laminar flow? Lol!
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: flossabe]
#15709405 - 01/23/12 10:35 PM (12 years, 11 months ago) |
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You're damned right I did.
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flossabe
Curious



Registered: 12/28/11
Posts: 29
Loc: USA
Last seen: 10 years, 4 months
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DOC BROWN!
Ok well I'm going to need one for naiver stokes and might as well provide differential examples for a differential control volume. I guess we can't leave out Reynolds either...
1.21Gigawats!
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Kako
Stranger

Registered: 01/22/12
Posts: 5
Last seen: 10 years, 5 months
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Re: Flow Hood Calculations Question [Re: RogerRabbit]
#15709821 - 01/24/12 12:16 AM (12 years, 11 months ago) |
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Quote:
psychotropical said: I decided to get a blower which delivered more than what was necessary according to the calculations and to use a solid state speed controller to get it exactly right using the flame test. This also lets me crank it up to max in order to scrub the air in the room for an hour or two, and then just throttle it down for the laminar work.
I really like the heavy duty aluminum frame around the filter, wood does have pores which contams can hide in, but you could always put a good sealer on it to make it non-porous.
I really like your idea of just buying a powerful motor and just scaling it back down with a controller. First question, 1TDU2 is 115/230 Volts. Does that mean it works on either voltage or it requires both voltages in order to operate? Thanks for the pics, they're always helpful and inspiring. I'll hopefully post a couple in a few of my setup too.
Quote:
RogerRabbit said: Just look for a blower which delivers around 350 cfm at .8 W.G. and it will be close enough at 1.2 W.G.
I'd suggest going to a heat and air shop in your town to see if they have a scrap blower from an old furnace unit. They'll probably give it free or very cheap. Around 1/3 to 1/2 hp will get you in the neighborhood. RR
I'm going to give that a shot tomorrow. If I don't come across anything, I want to get the shopping around part over with and starting the next phase of building it. Thanks for good advice. Who knows, maybe I'll have some luck tomorrow and save a couple of bucks.
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: Kako]
#15710777 - 01/24/12 09:12 AM (12 years, 11 months ago) |
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Yeah you can wire it up either way 115 or 230, just note the change in amps drawn for each on the specs, 'course you need a cord and controller rated to handle it.
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Fishermanj
StrangerDanger


Registered: 11/16/11
Posts: 92
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Quote:
psychotropical said: Yeah you can wire it up either way 115 or 230, just note the change in amps drawn for each on the specs, 'course you need a cord and controller rated to handle it.
Psychotropical, do you have any other in progress pictures of your flow hood you could post, like a shot from the front without the hepa in and a side shot showing your prefilter housing? Or, plans I could give to a woodworker to build? I like your design.
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psychotropical

Registered: 10/15/11
Posts: 235
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Re: Flow Hood Calculations Question [Re: Fishermanj]
#15766528 - 02/05/12 10:35 PM (12 years, 11 months ago) |
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Here's three more pics I dug up:

(There isn't one from the front but there is from the back)
There's no plan cause I just sketched it on a piece of wood and did the rest as I went, but it's not too tough to figure out if you take a look at the wood layout shot there. Basically I just made a box around the HEPA which leaves about 1/8 clearance to slide it in. I screwed the braces on so that when the HEPA slides in from the front, the braces that are securing the sides together also act as stops for the filter.
I made it so that the filter, which has a dense foam gasket on the front of it, protrudes out about an 1/8". That way when I screwed the front trim boards down around the face of the filter, it compressed the foam to make a seal. I also used silicone along the rear of the filter to seal it around the perimeter.
I made the back of the box so that it fits into the sides and is screwed onto the back braces, so it can be removed if need be.
The blower motor sits on a wood plate, and the outlet extends a little into the square hole I cut to accommodate it. As you can see, I made a wood support for the end of the motor. To fasten the blower outlet to the top, I just made a wood frame for it which is screwed to the top, and just drove 4 short sheet metal screws through the sides to fasten it. The motor outlet and the motor itself are siliconed in place to reduce vibration.
I built a frame for the motor box, fastened that to the top of the filter box, and fastened the box to that.
All the wood is glued and screwed. I used caulk and a finger to make smooth curves so they'd be easy to clean and to eliminate any cracks for mold to get a foothold in. Then I just painted it and sealed it with silicone.
Hope that helps and good luck - you'll be really glad you took the time to do it right, it's a real pleasure to work with a nice hood
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