fume hood venting system

[samuel-a]

This is the "new" :mrgreen: design of the vent.
Since the suction (veturi effect) on the last design was created far from the pipe opening (hood side), i bearly got any suction and at the moment i do not have 200-500 CFM blower at my disposal.
Instead, i improvised a contraption to hold togather 3 48V fans (CFM unknown) that blow inside the pipe. Air flow is reduced with an old soft drink bottle that had a great funnel like shape, i cut the bottom from it and fitted inside the "T' connection as illustrated in my picture.

With the PSU i can feed either 5V or 12V to the fans, 5V is when i'm gone or there no reactions going on and doors are closed.
12V is good enough to work a reaction with one door open and still don't smell anything.
I guess if i could feed them the full 48V each it will suck everything without a problem... the only major disadvantage to this arrangement is th noise...



I understand this is not ideal setup, but at least the fans are away from any corrosive fume/gasses and i do not expect them to fail.
Hope this might halp somone else

 

[texan]

Looks like the draft would work better if the exhaust from the hood itself was of a smaller diameter than the blower arrangement. Wouldn't this create a lower pressure that would suck fumes from the hood more effeciently.

Texan

 

[cjfeath]

I have a safety question on fume hoods.

Is it safe to tie your venting into your exhaust for your furnace and water heater? Is there any sort of combustion or circulation concerns with doing this?

 

[glondor]

Think about the chemicals you will be venting and ask yourself what is the worst that can happen.....Nox fumes in the furnace? Acid in the water heater? Forced air whole house poisoning? Don't do it. Dedicated proper vent please.

 

[Barren Realms 007]

I have a safety question on fume hoods.

Is it safe to tie your venting into your exhaust for your furnace and water heater? Is there any sort of combustion or circulation concerns with doing this?

With most heaters having forced air for the vent it is no longer a good idea to have the vents tied together. And it is a VERY BAD idea to try and use the same vent to exhaust refininning fumes.

 

[Harold_V]

Is it safe to tie your venting into your exhaust for your furnace and water heater?

Absolutely not! Not under any condition, nor for any reason. Carbon monoxide poisoning is a real possibility, to say nothing of the corrosive tendencies of fumes from the hood.

Harold

 

[eeTHr]

If two fans are used in parallel, when one fails, air from the working one will flow backwards out the failed one, unless you have a means to block it off.

 

[Barren Realms 007]

I also forgot to mention that the interior pipe of the vent is aluminum and will not stand up to the fumes.

 

[cjfeath]

Did not think so, but thought I would ask. Limited Space and was trying to find a spot for lab. Thanks for the replies all.

 

[ericrm]

This is the "new" :mrgreen: design of the vent.
Since the suction (veturi effect) on the last design was created far from the pipe opening (hood side), i bearly got any suction and at the moment i do not have 200-500 CFM blower at my disposal.
Instead, i improvised a contraption to hold togather 3 48V fans (CFM unknown) that blow inside the pipe. Air flow is reduced with an old soft drink bottle that had a great funnel like shape, i cut the bottom from it and fitted inside the "T' connection as illustrated in my picture.

With the PSU i can feed either 5V or 12V to the fans, 5V is when i'm gone or there no reactions going on and doors are closed.
12V is good enough to work a reaction with one door open and still don't smell anything.
I guess if i could feed them the full 48V each it will suck everything without a problem... the only major disadvantage to this arrangement is th noise...


I understand this is not ideal setup, but at least the fans are away from any corrosive fume/gasses and i do not expect them to fail.
Hope this might halp somone else

i the picture of samuel i have put in red a section of it setup , do someone know how to calculate the proportion of that thing so i can choose the desired size of the opening in the fume hood?

edit i aslo wondering ,in the use of one of those system could you... could you create a vaccum (unvolontary) in the room that would be stronger than the vacuum in the fume hood?

 

[samuel-a]

Eric

I suppose it could be theoretically pre calculated... but i have no idea.
An air flow meter is needed to get actual readings from the intake. From that, considering the pipe diameter you could calculate the actual suction cfm your system is producing.

 

[kjavanb123]

Hi,

I am trying to build a fume hood venturi system following the post by 4metals, I used a 100-liter bucket, cut the partion of it to place a door, and used a large funnle to place on top which is attached to a T connection, to serve as fume hood,


Attach to blower is a paper cup that I cut the bottom of it, and also glue to it a piece of paper rolled up to be used as venturi pipe,


Now when I test this system, I tried to simulate fumes by lighting toilet paper and leave them in a pot, placed about 25 cm under the T connection inside the fume hood, it sucks all the fumes out but as soon as I attach the gray pipe to a vertical pipe which is the same height as fume hood and is submerged to 100-liter barrel filled with water, I get positive pressure at T connection hole.

The pipe submerged in water has 8 holes drilled on it.

Should I increase the lentgh of gray pipe attached to T connection before attaching it to the scrubb pipe?

Regards
Kj

 

[4metals]

The use of a venturi style exhaust is only to suck air out of the hood, not to power suction through a scrubber. If you use the venturi setup you made to exhaust just the hood you should be OK as the burning of paper to generate smoke to test it confirmed. The power for the scrubber is an entirely different and second system you need to add.