6' Fume Hood

[watcher6880]

Another thing I am wondering.... I see all of the controversy surrounding the issue of using wood for framing... being that acids can be absorbed into the wood. Making it much more flammable. What if adding porcelain or ceramic tiliing to top on the hood/ workbench over the plywood would make it any safer?

 

[glondor]

I think chopping on some fiberglass may be better, but it might not be cheaper. When mine gets a rebuild I think this is what I will do. I have put a epoxy coated steel pan in the bottom of mine for now as the fire danger is very real. I would love to get a hold of a nice 1000 gal fiberglass tank and mod it to suite. I used to get dozens a year when i did demolition, crushed them and sent to land fill...If I only knew then what I know now.....

 

[watcher6880]

Thanks, I have the fiberglass fabricating and reworking experience to build my own so that is definately a route to go about... At Lowes they sell bathboard but it's not thick enough to hold as a wall...so taking the fiberglass bathboard and adding more layers of chop and matte to make it thicker might work as well. Make a few sheets to do the entire project and then saw what you need. They come in 4x8 sheets.. Also if someone doesn't want to waste all that time, they do have fiberglass shower stalls with drains (this could be modified and the tub part of the stall would be perfect). Just 'glass off the drain (flat) and then add plexiglass to the front of the hood. Just an idea. Any other ideas added to this are welcome.

 

[Noxx]

According to the document I provided, fiberglass should not be used.

They say that when it burns, it releases huge amount of noxious smoke...

 

[qst42know]

The right epoxy might be worth looking into.

http://www.epoxysystems.com/640.htm

 

[eeTHr]

Noxx---

Modified 10'' dia duct with spacers ready to accept the 12'' dia. rain cap.

From Re: Lab Hood, Ventilation & Scrubber System Design---

No airflow restricting rain caps allowed.

How does a tube over another tube keep the rain out Noxx? Can't tell if there is something else in the bigger tube to deflect the rain.

So, what is inside your 12" diameter "rain cap"?


:?:

 

[Noxx]

It's not a ''proper'' rain cap. In fact, it's just two concentric tubes.

Since rain rarely does fall straight down, the outer tube acts as a guide to drain the water outside of the air duct.

It's a bit hard for me to describe so here's a schematic:

 

[Smack]

I understand what you did. Mine exits out the roof vertically also, but I just put 3 45's on it.

 

[Barren Realms 007]

It's not a ''proper'' rain cap. In fact, it's just two concentric tubes.

Since rain rarely does fall straight down, the outer tube acts as a guide to drain the water outside of the air duct.

It's a bit hard for me to describe so here's a schematic:

Noxx, I feel you are setting yourself up for a problem. If I am looking at this correctly your 12" pipe is sealed on the top, your air circulates up to the top and then back down and out between the 10" and 12" pipe. Calculate the area of the 10" pipe and then calculate the area of the 12" pipe. Subtract the figures and see if they equal less than the area of the 10" pipe. It will not actually be a 2" space between the pipes it will be less by the thickness of the wall of your 10" pipe so your calculation will be off just a little bit.

 

[qst42know]

No you don't close the top. It's a stack within a stack type. Bad diagram you can't read the dimensions.

http://www.swcleanair.org/Forms/78-RainCapsExhaustStacks.pdf



Though I think I see a small problem with the installation. When you do get more snow on the roof ice may build up between the two pipes and break one of them.

 

[eeTHr]

...it's just two concentric tubes.

Since rain rarely does fall straight down, the outer tube acts as a guide to drain the water outside of the air duct.

Ahhhhh! Now it all makes sense! 8)

 

[eeTHr]

diagram....

http://www.swcleanair.org/Forms/78-RainCapsExhaustStacks.pdf

It would be cool to put a hex type on bottom to catch the straight down rain, and a stack in a stack type on top of it, to divert the angled rain.

 

[4metals]

In my opinion the tube within a tube type of raincaps are the best for refining. They have been around for years and I have used them often. One big plus is that the exit velocity of the fume is not inhibited by any obstructions and the exhaust blows straight up (not diverted to the side as with a typical "witches hat" raincap.

As Noxx said the amount of rainfall falling straight down is suprisingly little and the difference in length between the shorter inside pipe and the longer outside pipe can be extended to trap any rain falling at any angle greater than about 5 degrees from straight down and divert it off to the side of the main (center) pipe.

Good choice Noxx!

 

[HAuCl4]

I'm sorry to be the party-pooper, but all of this setup looks to me as extreme overkill.

 

[glondor]

RE extreme over kill..........................could you please explain a bit what you mean. I Think over all it is a great system Noxx has put together. There are a few things I would have done a bit different, but that's just my preference. So Haucl4...please tell what is over kill.

 

[HAuCl4]

So Haucl4...please tell what is over kill.

Overkill: Hunting rabbits with a nuclear weapon. Killing flies with a shotgun. Metaphor for "expensive and ineffective" at the same time.

This setup is expensive, ellaborate, complicated, and I don't believe it even scrubs the fumes before releasing into the atmosphere. All in all a very poor deployment of capital and effort. Just my opinion, of course.

When I saw the photo of the "chimney" in the roof with the snow and the cables, it became over the top for me. I just had to say something. Sorry.

Nothing personal Noxx.

 

[goldsilverpro]

So Haucl4...please tell what is over kill.

Overkill: Hunting rabbits with a nuclear weapon. Killing flies with a shotgun. Metaphor for "expensive and ineffective" at the same time.

This setup is expensive, ellaborate, complicated, and I don't believe it even scrubs the fumes before releasing into the atmosphere. All in all a very poor deployment of capital and effort. Just my opinion, of course.

When I saw the photo of the "chimney" in the roof with the snow and the cables, it became over the top for me. I just had to say something. Sorry.

Nothing personal Noxx.

HAuCl4.

Were you someone that people listened to, that would have been a cruel thing you said. Noxx built this beautiful fume hood and you knock it. Do you have any friends?

 

[HAuCl4]

Well. I consider both you and Noxx as friends as far as "online friendship" goes. I certainly do not have "enemies" in this forum or online. I just spoke my heart, and what I believe it's the truth. It's a contraption that blows fumes into the atmosphere. Maybe it's "beautiful" as fume hoods go...Not for me. I don't take back any word I wrote. Cheers.

 

[glondor]

Sooooo, What you really meant to say is in your opinion it is not complete yet with out a scrubber. In essence "underkill" for its intended use? Not trying to put words in your mouth, just trying to clarify your issue with the system.

 

[HAuCl4]

Sooooo, What you really meant to say is in your opinion it is not complete yet with out a scrubber. In essence "underkill" for its intended use? Not trying to put words in your mouth, just trying to clarify your issue with the system.

No. What I meant is what I wrote. And I do not intend to defend or explain it any further after this post. You can search for yourself in this same forum better and cheaper systems and methods for dealing with fumes. In all honesty the carpentry work looks great. It's just the cost of the blower and the deployment of the pipes, without scrubber, the main objections that I have. Cheers.