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New glovebox design questions


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#21 ernestro

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Posted 07 November 2008 - 01:38 PM

i guess i wont be off-topic if i ask
- what's the deal with a "positive" pressure glovebox? how is it used/concept?
I might be imagining it in a counter- productive way..

#22 RockyRaccoon

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Posted 07 November 2008 - 02:00 PM

the volume of air flowing into the chamber is going to equal the volume of air blowing out .

a fan blowing outward will result in a lower pressure inside the chamber than outside (negative pressure) . this will cause new air to be pulled in to equalize the pressure . in most cases , the air will be sucked in through cracks and small openings that would normally not have much air flow . in doing this , a container that would otherwise be considered sealed can become compromised .

a fan blowing inward will cause the pressure to be higher inside , and the air will escape through the same openings mentioned above . this is called positive pressure . if the incoming air is clean (if a filter is used) , positive pressure can be beneficial because the outward flow of air escaping through the cracks can prevent contamination from entering against the current .

#23 ernestro

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Posted 07 November 2008 - 02:25 PM

ahh, i missed the filter part:) :eusa_whis...changes everything
yes i dig the whole gradient thing

cause without a filter it made pretty much no sense..

have it good

#24 Ben Dover

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Posted 07 November 2008 - 04:45 PM

I would use a flow hood, but $60 for a kickass glovebox that is equivelently clean is a bit more in my price range than building a $600 flowhood. Not to say that flowhoods aren't nice. They definately are a lot easier to work at, and I still plan on building one when I have the coin to cough up for such luxuries.



I have been looking to build a flowhood soon and my supplies list is around $200

~18" x ~24" x 6" %99.99 HEPA filter ~$100
Used squirrel cage fan Free at your local HVAC company
110V 3 speed motor to replace the big ass one in the fan ~$50
4' x 8' sheet of good quality oak plywood ~$35
Screws, paint, silicone ~$15

I'll be sure to post a rundown of it when I build it, hopefully before xmas

Sorry, off topic but I thought y'all might like to know

#25 oakchild

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Posted 07 November 2008 - 07:55 PM

I have been looking to build a flowhood soon and my supplies list is around $200

~18" x ~24" x 6" %99.99 HEPA filter ~$100
Used squirrel cage fan Free at your local HVAC company
110V 3 speed motor to replace the big ass one in the fan ~$50
4' x 8' sheet of good quality oak plywood ~$35
Screws, paint, silicone ~$15

I'll be sure to post a rundown of it when I build it, hopefully before xmas

Sorry, off topic but I thought y'all might like to know


I have looked into this before. The problem I keep running into is lack of finding the "Used squirrel cage fan Free at your local HVAC company"

I have resorted to trying "Cheap squirrel cage fan" on Craigslist and Ebay. I check back periodically, but still haven't found anything that is both cheap (<=$100) and up to the task (>=600 CFM).

If you have any advice about the Free fans, shoot me a PM. I would love to know where to get one.

Blessings,
Oakchild

8-)




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