GREAT Ventilation idea.....

[robinbrown]

Ok,, This is quick, inexpensive and stainless steal!
BRILLANT!
http://www.glassartists.org/Gal693_glass_studio.asp

People amaze me sometimes!!!!!!!!!!
:grin:
Robin

[Dale M.]

aaah.... Don't think it stainless steel.... Garbage cans usually tend to be galvanised (Zink coated) iron/steel. Unusual concept, it probably works, same ventialtion calculation rules need to be alpplied though...

http://www.glassartists.org/Images/FullSize/000002000/Img2641_studio_003.jpg

Dale

[robinbrown]

Dale,,
This may be dumb, but does the hood need to be steel or sheet metal of some sort?
Can the toxic fumes be "absorbed"?

Thanks,
Robin

I should have known not stainless steal... EXPENSIVE trash can huh?

[Dale M.]

For practical safety (non flammable) and structural considerations "metallic" hoods and ducting is really the best way to go.

Certainly there are other materials that will work, but one has to consider the limitations of the materials as to flammability, melting point, ease of construction when trying to create a efficient system.

Most materials will not absorb any harmful gases, there is the possibility for deposit of heavy metals and other contaminants on surfaces on inside of components of ventilation systems though.

Dale


.

[lbjvg]

Its not clear to me that the face velocity would be adequate unless there was a very powerful motor on the fan.

- Jim

[Dale M.]

Its not clear to me that the face velocity would be adequate unless there was a very powerful motor on the fan.

- Jim

Its not clear to me what your comment is referring to!.

Just for giggles, if diameter of garbage can is 2ft (24 inches) the surface area (face) is about 3.2 sqft. If you apply the 100cfm per sqft rule, it only requires a 300-350 cfm fan/flow to maintain a nominal face velocity. Being that fan is not visible, its hard to determine how large fan may be.

Dale

[BillBrach]

I kinda agree with Jim. Although it may pass the 100 CFM/sq. ft. rule, I don't think the collection AREA is big enough. Usually, a standard range hood is not big enough, and this can's face surface area is less than that.

But, it would be very easy to add a sheet metal "lip", sort of like the bill on a baseball cap, all the way around it, or at least around the front half.

And to answer the question about metal, no it does not have to be made out of metal as long as whatever material is used doesn't get too hot. The smaller hobby torches like a HH or a Nortel Minor, or GTT Bobcat, or even a GTT Lynx would work fine with a box made out of even wood, or foil faced foam board.

Personally, I'd prefer to see an oversized wooden hood than an undersized metal one !!

[MikeAurelius]

Face velocity needs to be about 2500 feet per minute.

Using Dale's approximation of 350 CFM, the face velocity is 1782 FPM (this is all supposition mind you).

Assuming that the duct diameter is 6", and a total run of 20 feet, the total system static pressure is about .2" (again supposition).

A 500 CFM fan will bring the face velocity up to 2500 FPM.

[Dale M.]

I have to agree with Bill that the efficiency of collection area is quite lacking. But it shows what a bit of ingenuity can do to make up a ventilation system...

Actually enclosed fan and vent duct look pretty good, now coupled with a better hood it could be the "cats meow".

Dale

[Dale M.]

Face velocity needs to be about 2500 feet per minute.

Using Dale's approximation of 350 CFM, the face velocity is 1782 FPM (this is all supposition mind you).

Assuming that the duct diameter is 6", and a total run of 20 feet, the total system static pressure is about .2" (again supposition).

A 500 CFM fan will bring the face velocity up to 2500 FPM.

Mike.... Where do you come up with the figure that "FACE VELOCITY needs to be 2500"....

Some clarification and reference to your source information would be helpful!

Dale

[MikeAurelius]

It's in the white paper on AGF Technical forum, "Static Pressure 101"

It's the ACGIH recommendation for face velocity.

In part:

Another important factor to designing the correct exhaust system is the flow rate or Velocity.

Low velocity air movement will not convey fumes or particulates. High velocity air movement is very noisy. Somewhere between the two is a delicate balance between moving fumes and particulates and noise.

ACGIH (as noted above) has another "Recommended Practice" that we need to look at: "Minimum Duct Velocities for Conveying Materials"

Very fine light dust : 2500 - 3000 FPM
Dry Dusts & Powders: 3000 - 4000 FPM
Average Industrial Dust: 3500 - 4000 FPM

For our purposes, as lampworkers, we should be using velocities in the range of 2500 to 3000 FPM. If you do a substantial amount of work with frit, you should consider a system that moves between 3000 and 3500 FPM.

[BillBrach]

Oh, I see how this works !! Refer those who are questioning your "theroies" to your website, where you have BANNED both of them !!

I question the 2500 FPM number. This might be correct for 'Very fine light dust' but I think it is meaningless for gas MOLECULES !!

[MikeAurelius]

Bill - you will have to take the "banning" issue up with Jerry. I had and have nothing to do with it.

Question away:

Low velocity air movement will not convey fumes or particulates. High velocity air movement is very noisy. Somewhere between the two is a delicate balance between moving fumes and particulates and noise.

If you believe that you have more experience and qualifications than the ACGIH (American Conference on Governmental Industrial Hygiene), then by all means, go ahead and make your own recommendations.

I was merely responding to Dale's question on where the number came from.

[BillBrach]

Jerry who ?? You fund the site, Jerry does what he is told by you !!

And, I have no interest in being a memebr of your site anyway, so the BANNING ISSUE above is really moot.

[MikeAurelius]

Then why bring it up, other than to try to start a ruckus?

Oh - and the site is self sustaining thanks to the contributions of its members. I haven't paid for a thing.

[Dale M.]

It's in the white paper on AGF Technical forum, "Static Pressure 101"

It's the ACGIH recommendation for face velocity.

In part:

Ahhh... I do believe your white paper to be in error.... I believe you mean a figure of 2500fpm for DUCT VELOCITY...... The accepted rule for FACE VELOCITY is 100fpm per sq.ft. of FACE (fume hood) opening.

Suggest you verify your white paper against this site.

http://www.energyusernews.com/CDA/Article_Information/Fundamentals_Item/0,2637,22007,00.html

But then again I can not verify your white paper as I also do not have access to your site to verify the validity of your "white paper"...

Dale

[BillBrach]

Dale's information that you so "graciously" corrected was ACCURATE as it stood.

[MikeAurelius]

Dale - you are absolutely correct. My response above WAS in error, It should have said DUCT velocity, not FACE velocity. I apologize to anyone who was confused by my response.

The white paper is correct however, as it does refer to duct velocity, the speed of air movement required to keep fumes and small dust particles in suspension while being moved through the ducting.

Face velocity refers to the amount of air being moved through the entire face of the hood.

Thanks Dale for calling this to my attention, I appreciate it.



Ahhh... I do believe your white paper to be in error.... I believe you mean a figure of 2500fpm for DUCT VELOCITY...... The accepted rule for FACE VELOCITY is 100fpm per sq.ft. of FACE (fume hood) opening.

Suggest you verify your white paper against this site.

http://www.energyusernews.com/CDA/Article_Information/Fundamentals_Item/0,2637,22007,00.html

But then again I can not verify your white paper as I also do not have access to your site to verify the validity of your "white paper"...

Dale

[Craftylady]

Dale - you are absolutely correct. My response above WAS in error, It should have said DUCT velocity, not FACE velocity. I apologize to anyone who was confused by my response.

The white paper is correct however, as it does refer to duct velocity, the speed of air movement required to keep fumes and small dust particles in suspension while being moved through the ducting.

Face velocity refers to the amount of air being moved through the entire face of the hood.

Thanks Dale for calling this to my attention, I appreciate it.


Mike thank you for clearing that up. I sure hope this helps out Robin. Because I know thats all that was intended to do. ;-)

[robinbrown]

OK,, I say the pissing contest is now over. All of you are very intelligent. Thanks for the information. Believe it or not this all has helped me. I'm now thinking of things I didn't before.

Have a great day,
Robin