# Fume hood design suggestions



## autumnwillow (Feb 25, 2016)

I will be building this hood tomorrow, any suggestions would be welcome. Forgive my poor drawing.

It will all be made of marine plywood and sliding glass.
It will have an external scrubber for semi-closed reaction vessels similar 4metal's design.
The fume hood will also have its own scrubber made from 4" pvc tubes, a minor one just for the fumes escaping when removing the semi-closed reaction reactor.
I would also be building a sealed housing for the vacuum pump then its exhaust would connect to the fume hood's minor scrubber.

I am still thinking what would be the best paint to use. An exterior latex paint or epoxy paint.
Testing the scrubber, correct me if I am wrong but I would put a piece of soft iron in the exhaust port of the scrubber and this piece should not corrode.


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## autumnwillow (Feb 25, 2016)

I would like to put transparent hoses to see the gases flowing, but I wonder if these hoses would stand against the fumes.


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## philddreamer (Feb 25, 2016)

I also built mine following 4metals design:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=85&t=23107&p=242564&hilit=fume+hood#p242564

Phil


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## autumnwillow (Mar 8, 2016)

Almost done!


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## Anonymous (Mar 8, 2016)

Looks great. How are you going to pull the required volume of air through that though?


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## autumnwillow (Mar 8, 2016)

I have a 5cfm vacuum pump so I think that should suffice. If it doesn't suck fumes I would just have to reduce the length of the pipe


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## g_axelsson (Mar 10, 2016)

Those filters with their thin pipes and a vacuum pump might handle the fumes from digesters, vacuum filters or boiling flasks, but it is not even close to handle the flow from a fume hood to keep fumes from exiting through the large opening in the front when you are working in it.

Göran


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## autumnwillow (Mar 11, 2016)

g_axelsson said:


> Those filters with their thin pipes and a vacuum pump might handle the fumes from digesters, vacuum filters or boiling flasks, but it is not even close to handle the flow from a fume hood to keep fumes from exiting through the large opening in the front when you are working in it.
> 
> Göran



There will be 2 sliding glass in front. The fumes from the hood will go to a mini scrubber unit, this is just for the tiny fumes escaping. I will always use the vacuum setup for all the nitric / ar digestions.


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## g_axelsson (Mar 12, 2016)

Thanks for the clarification, the next guy reading this thread might not realize that the scrubber on the floor is only for fumes extracted directly from the process and not for the main vent of fumes from the hood.

Looking good so far. 8) 

Göran


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## Smack (Mar 12, 2016)

Just at a glance, a hood that size would require 350 to 400 cfm. 5 cfm is nothing and you will find that out on your first nitric digestion.


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## autumnwillow (Mar 25, 2016)

Well, those pipes had leaks. I guess it was during its transportation. Too many leaks that I decided to just cut away what I could save.

I ordered 4L filtering flasks instead and will be using pvc pipes again but this time the connection between two filtering flasks will be hoses so as to avoid the pvc pipes from moving.

Phil, how are your hoses holding up to ar/nitric fumes? Do you replace them every now and then or can they survive the fumes?


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## autumnwillow (Apr 12, 2016)

Almost there but.. my vacuum pump was too strong or the liquid level was too high that it sucked the caustic solution into the vacuum pump. I already have drained the pump and put some more oil in. I'll drain it again tomorrow, put another oil. Run for 2 minutes. Drain and new oil again. If this doesn't work then I'm off to buying a lower rated vacuum pump. (caustic and oil makes soap, it was soapy.)

If all goes well, I would have to build a bleeder valve. 

The aluminum ducting is temporary. As I am having a hard time deciding where to place things. I will just have to check on it every time. I will either replace them with PVC ducting or PVC pipes.

Question, if H202 degrades with light, how do you determine if there is still h202 available? Do you dose concentrated amounts of h202 or do you dilute them?
As for the caustic solution, am I correct that it is all a matter of pH level?


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## Anonymous (Apr 12, 2016)

Wait up. Why are you using Aluminium?


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## autumnwillow (Apr 12, 2016)

PVC ducting is hard to find in my country. I would have to probably order it online from other countries. PVC pipes at 6 inches will be hard to lay at its current state. Again this is temporary. I will change it as soon as I see signs of corrosion.

If my pump works tomorrow, I'll probably try to dissolve [stt]10g of inquarted gold and see how it goes.[/stt] _It would be better if I just put all the inquarted gold in a beaker, then add very small amounts of nitric acid, see how the scrubber goes, adjusting the relief valve of the vacuum pump._


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## Barren Realms 007 (Apr 12, 2016)

autumnwillow said:


> PVC ducting is hard to find in my country. I would have to probably order it online from other countries. PVC pipes at 6 inches will be hard to lay at its current state. Again this is temporary. I will change it as soon as I see signs of corrosion.
> 
> If my pump works tomorrow, I'll probably try to dissolve 10g of inquarted gold and see how it goes.



What kind of pipe is used there for plumbing drain system in buildings?


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## autumnwillow (Apr 12, 2016)

Barren Realms 007 said:


> What kind of pipe is used there for plumbing drain system in buildings?



Old buildings use galvanized iron. My office building uses PVC. Most of my wastes will be re-used in other forms of chemical reactions, as soon as they have no use or value, I will treat them first before disposal.


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## Barren Realms 007 (Apr 12, 2016)

autumnwillow said:


> Barren Realms 007 said:
> 
> 
> > What kind of pipe is used there for plumbing drain system in buildings?
> ...



Is there a supplier of the PVC pipe in your area that you can get the material from? Check with local plumbers.


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## autumnwillow (Apr 12, 2016)

Barren Realms 007 said:


> Is there a supplier of the PVC pipe in your area that you can get the material from? Check with local plumbers.



Yes there is. That orange pipe connecting the hood and the vacuum pump enclosure is actually a 6" PVC Wye. The room is very tight for 6" PVC pipes. I would have to bend them by heating or get a PVC ducting shipped from overseas.

As soon as I am able to refine in this setup, I will upgrade everything to a more proper setup. With the current aluminum ducting whether it corrodes or not, this will give me an idea whether I should put a mini scrubber for the fume hood or should I just omit it as the space is getting really tight.


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## Barren Realms 007 (Apr 12, 2016)

You should be able to run 4" to the hood you have to do the job. You can heat PVC pipe in hot water or oil to bend it if that is required. You can make a jig for 90 deg turn and heat short lengths of pipe then use glue on couplings to connect it.


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## FrugalRefiner (Apr 12, 2016)

If you choose to bend PVC, fill it with sand and cap the ends before you heat it. Don't glue the caps on; just tap them on. The tapered joint will hold them on while you bend it. When you bend it around your form, the sand will help keep it from collapsing. Once it's cooled, you can remove the caps and empty the sand.

Dave


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## autumnwillow (Apr 13, 2016)

I tested this fume hood and scrubber system today with my 500g inquarted gold (expecting about 120g yield).
The scrubber is working great! I could see the brown fumes turning to clear fumes. Thank you 4metals! 
Although I had to bring the volume down to about 3.2L because the first vessel was gaining its volume by condensation of the fumes. Speaking of condensation, I have condensations everywhere, from the reaction flask hose up to the other hoses.

I did not finish it today though as I never turned the heat up, I would go for the highest heat setting tomorrow and see how it would go.



FrugalRefiner said:


> If you choose to bend PVC, fill it with sand and cap the ends before you heat it. Don't glue the caps on; just tap them on. The tapered joint will hold them on while you bend it. When you bend it around your form, the sand will help keep it from collapsing. Once it's cooled, you can remove the caps and empty the sand.
> 
> Dave


Thank you for the advice, the concept of your advice is very similar to jewelry tube bending. I will do this as I deem necessary, but I think I would have to re-design the hood. Too many condensations everywhere and they are building up. I think it would be better if the vacuum filtration setup are located at the bottom rather than at the top of the fume hood. Also my fume hood lacks height. The 4L filtering flasks fits in there but once I attach the buchner funnel I could no longer see what is going on in the filter paper.



Barren Realms 007 said:


> You should be able to run 4" to the hood you have to do the job. You can heat PVC pipe in hot water or oil to bend it if that is required. You can make a jig for 90 deg turn and heat short lengths of pipe then use glue on couplings to connect it.


When I was designing this hood, everything was meant to be 4" as the space that I will be working on will be small. Apparently as soon as I tried to look for fans, the 4" fans where only rated at 200cfm. My hood requires at least 500cfm.


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## Anonymous (Apr 13, 2016)

Ahh now I understand what your plan was! That looks pretty good- how do you deal with the loose fumes as opposed to the ones within the sealed reactions?


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## autumnwillow (Apr 13, 2016)

No scrubbing device yet for the loose fumes outside the reactor, they simply pass those aluminum ducting that I showed. I will decide whether to add one or not as soon as the aluminum ducting corrodes which I hope will be in a very long time because very tiny fumes escape.


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## saadat68 (Nov 5, 2016)

autumnwillow said:


> No scrubbing device yet for the loose fumes outside the reactor, they simply pass those aluminum ducting that I showed. I will decide whether to add one or not as soon as the aluminum ducting corrodes which I hope will be in a very long time because very tiny fumes escape.



Hi
Can you see my post here and help me?
Your scrubber is like an image in my post. see please:
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&start=30#p261996


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## saadat68 (Nov 13, 2016)

I don't want make upper section for my hood. No problem ? :shock: 
I want make a small cube for my small work. For example 40*40*40.
It is OK?


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## 4metals (Nov 13, 2016)

The peaked section in the hood is not necessary if your blower is strong enough. Since most refining fumes rise upward from the reaction the peak, which directs fumes from all corners of the hood into the center where the exhaust blower is, allows the blower to be more effective. So in most cases you can get away with a smaller blower. Without a peaked top or an inclined internal baffle you will create "dead zones" inside the hood unless you have a powerful blower.


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## saadat68 (Nov 13, 2016)

Thanks I want to add a vacuum scrubber and a blower to my hood
I think it is better


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