All large HVAC supply house's have pipe in stock in 26Ga.up to 14" diam. x 60" long. It is a common item, but if you pass though any combustible surface's it is a good idea to use the proper vent material with clearances recomended by the manufactuer.I got lucky we install many large boiler flues for mechanical contractors and was able to get twenty feet double wall positve pressure stainless steel pipe 14" id.

Thanks Otis
Ill keep the HVAC supply in mind about the pipe.
I have cut my materail to size for 12 in. pipe
Im going through a tin shed roof no wood.
Im going to try single wall black stove pipe inside & maybe galv.outside
Hope to get the hood put together Sunday.
Thanks Ron

Leah, I have a question for you. I got the impression your roof was metal too. If so, what'd you use for flashing where the hole pokes through?

Rick, the guy who helped me went to a local metal mart and bought a rubber boot. It has a square, flat base and the middle is stair stepped like a round wedding cake. You choose the size you need and cut it at that "layer" and slide it over your pipe. He cut it a size or two smaller and had to push to get it to slide over the pipe. He put some kind of sealant around the pipe under the "layer" and also all around the base. He then used screws all around the base. The rubber conforms to the ridges and flats of your roof because the base has a soft metal band around it. He said to be sure and get the right sealant for the kind of finish your roof has. It has been up for 5 or 6 years and has never leaked.

Dadgum it ! I ran out of Acetylene
I have it all welded all I need to do is cut my hole in the top and weld on a colar for my 12 in. pipe.
It will be later on in the week before I can get to town for Acetylene.

Im just learning how to cut and weld with Oxyacetylene.
How many hours should I get from a 100 cubic foot Acetylene?Im guessing what I used maybe 5 hrs. cutting & 6 hrs. welding
Runing Oxy 20 - 40 lbs. Acetylene 3-5 lbs

Oxy. is 122 cubic foot - I have 1000 lbs left in the Oxy.think that would run another 100 cubic foot Acetylene??

I had made a stand to hold my torch while burning (bad idea)- I need to shut it off when not in use even if its just to clamp or move something.
Thanks Ron

Thanks, Leah. Is the base of the rubber boot metal or rubber as well? Do you know if the rubber is high-temp or what?

Ron,

With regards to 'how many hours should I get from 100 cubic ft of Acetylene', it depends. Usually you run out of Oxygen before you run out of Acetylene if the bottles are sized the same and you're doing a lot of cutting.

For OA welding on 1/8" and thinner metals I use 5 pounds of Oxygen and 5 pounds of Acetylene and a number 1 tip. I adjust the Acetylene flame so it's just starting to feather out at the end and add oxygen until I get a neutral flame. I haven't done too much cutting or welding lately, but my tanks are almost a year old and I haven't run out of either yet.

Of course now that I said that, I'll run out just as I start on something. ;)

Ron, check out one of these gas savers for your torch. They are the flea's Knees: WeldingDepot -- Gas Saver - Oxygen / Acetylene

For my money, I keep both my oxy and actyl at 4 pounds when welding. Of course your tip size will determine your volume of gas you are using. I seem get prett good mileage out of my tanks. My tanks are the same size as yours. I weld ALOT. I refilled both in October and I at about half a tank on the fuel. The O2 I am about three quarters. The trick to gas welding is sizing your tip right for the job, and watching your operating pressures.


Phil

Like I say Im just starting
after posting was thinking about it I had used it for some other things but It sure went quick.

Ive had this torch about 7 years but have just started using it.
Ive been lucky and so glad last week I bought the book - Welding by Don Geary. Its about Oxyacetylene welding.

I thought I knew enough to learn Oxyacetylene on my own.
Ha! I did not have a clue - about all I knew was tall bottle Oxygen -short bottle Acetylene.

After reading 3/4 of the book I took soapy water and check for leaks-the conection to the bottle vavle on both were leaking Acetylene was bad. Im sure that is where my Acetylene went.

Took off regulators wiped everything off, check over the threads, cracked both bottles and replaced .

Just to be safe took off lines and did same with them,went over everything cleaning & checking fittings.Then did the soap test regulator to bottle first then the lines. Leak free

That wasnt the only dumb mistake
I did not know about Acetylene not to ever run over 15 lbs.
Or Oxygen coming in contact with oil and grease.
Its a wonder I wasnt blown to bits.
Just thought I would tell on myself -Dont do like I did, I was lucky get a book take a class learn from someone.Be Safe , or they will be scraping hambuger
off whats left of you shop walls.

I need to get some saftey stuff and a new work coat.
I was welding Sunday my old Carhart on unzipped kept smelling something.
Had goggles on and did not see the smoke until I stoped.
My coat was touching the other side where I was welding . Now I have a baseball size hole in it.
I know what burning Carhart smells like now:o
Im learnin
Ron

That looks good how and where do you mount it.
It has a pilot light flame tell me about it
Ron

I use a hose rack with a 8' hose on it, the valve is mounted with a angle iron on the side of the rack between my longer hose to the tanks. Make sure you have backflow Valves on your torches. when the lines blead down it can cause backflow problems. The nice thing is when you relight you dont have to readjust your settings.

Like I say Im just starting
after posting was thinking about it I had used it for some other things but It sure went quick.

Ive had this torch about 7 years but have just started using it.
Ive been lucky and so glad last week I bought the book - Welding by Don Geary. Its about Oxyacetylene welding.

I thought I knew enough to learn Oxyacetylene on my own.
Ha! I did not have a clue - about all I knew was tall bottle Oxygen -short bottle Acetylene.

After reading 3/4 of the book I took soapy water and check for leaks-the conection to the bottle vavle on both were leaking Acetylene was bad. Im sure that is where my Acetylene went.

Took off regulators wiped everything off, check over the threads, cracked both bottles and replaced .

Just to be safe took off lines and did same with them,went over everything cleaning & checking fittings.Then did the soap test regulator to bottle first then the lines. Leak free

That wasnt the only dumb mistake
I did not know about Acetylene not to ever run over 15 lbs.
Or Oxygen coming in contact with oil and grease.
Its a wonder I wasnt blown to bits.
Just thought I would tell on myself -Dont do like I did, I was lucky get a book take a class learn from someone.Be Safe , or they will be scraping hambuger
off whats left of you shop walls.

I need to get some saftey stuff and a new work coat.
I was welding Sunday my old Carhart on unzipped kept smelling something.
Had goggles on and did not see the smoke until I stoped.
My coat was touching the other side where I was welding . Now I have a baseball size hole in it.
I know what burning Carhart smells like now:o
Im learnin
Ron

Ron,
Amen, NOTHING IS BETTER THAN A HANDS ON WELDING SAFTEY CLASS!!!!

O/A IS DANGEROUS IN THE HANDS OF THE UNINFORMED, THE STUPID AND

CHILDREN.

Here is an example: http://www.thedenverchannel.com/news/6790966/detail.html?subid=22100484&qs=1;bp=t#

This was one party balloon filled with what comes out of a welding tip. click on the car pic for a closer look.

If the gas is bothering you, is it burning completely? Do you have a CO detector? Your shop may also be too tight for a chimney as well. I have been using gas since 1993, maybe that is part of my problem?!

Too tight ? That might be my problem then. I've got a round shop in the making about 20 feet accross but due to time constraints and this being canada I decided to tarp it in for the winter. I have a side draft with a 12'' stack (which I picked up from the local scrap yard for 30 cents a pound) even with the door open I have a miserable time getting it started. I gennerally wind up sticking a propane torch in the chamber to force a draft.This works well but who wants to be forced to do that. I've been considering adding more length to it. It currently stands 15 feet off the ground which is about two feet higher than the roof peak. Any feed back on this situation would be of service.

Haw-thrn

Try lighting a sheet of news paper in the mouth of the hood to start the draft before you start your fire. Another point that is often missed in the design is a smoke shelf in the hood, this lowers the back draft and improves the draw.

example:Side-Draft Flue Design

Harris torch - the one tip I have is a #3 for 1/16 plate
Harris recomend settings of 3 Oxygen - 3 Acetylene
That setting worked good on the 3/32 plate all welds were outside corners
no rod used just basic welding.

habu
I thought as you use Oxyacetyleen the voluem of gas was allways changing in the bottles- every time you shut off or during lots of use you had to reset preasures because the voluem of the fule was less?
Ill check into the backflow Valves - ive been trin to keep a little more Oxygen presure than Acetyleen doesnt that help stop back flow?
Ok maybe I read it worng I assume you need the backflow Valves for the auto shut off OK.
Bear with me trin to be safe
Ron

I took a couple pictures of the hood
My welding not the best my first time . I think Ive got good welds my beads are uneven in places, no holes. I did blow a hole in the front but filled it.It squared up pretty good. I cut it out with the torch also 3/16 mild steel.

Out of Acetyleen need to cut top out and weld colar for 12 in pipe
Hope it works
Ron

Ron

When you use the gas saver both lines shut off at the same time, if you blead off the presure in the hose down stream of the shutoff unevenly there is a chance that the gases may mix in the other hose. This is not something that i want to risk. check valves at the torch are a cheep fix that should be there anyway. you will still need to adjust your flame after a restart but not like when you shut off your valves on the tank or torch. Most times you just pick up the torch and pass it over the flame and go to work. It makes no mater if you are mixing oxy with acetyleen or acetyleen with oxy the mixture is explosive. The 7 or 8 dollars for the check valves will save your hose and your regulators in the case of a backflash and maybe a trip with flashing lights.

wouldn't a smoke shelf just obstruct the air flow? A plain old pipe with a hole in the front might have a bit less pressure, but there'd be more room for everything to flow upwards, and it would be just straight up, and easier to build too.
just my two cents.

Archie,

No, the smoke shelf causes a venturi effect increasing the velocity of the air and drawing any backdraft up the stove pipe. You will find a smoke shelf and a damper in any fireplace or wood stove from 1800 on. Check out: Forge Chimneys