gas forge burner question

Gday all,
is there any advantage or disadvantage to using a blown burner over a
venturi or atmospheric type?
I trying to decide which type to build, I know I know, build both and
test.... :-)
Rusty_iron
Reply to
Rusty_iron
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Hi Rusty,
Both have their up side.
The venturi or naturally aspirated are portable, and can be taken anywhere you can carry a gas bottle.
Blown requires an extra air source, whether delivered by hand or by an electric motor.
Some say that you can't get the temperature to forge weld with a naturally aspirated burner... bollocks to that, it can be done.
The forced air burner in theory can get hotter than a venturi style, but I find that propane without air is enough for me. I smelt bronze also with a naturally aspirated burner. I don't think I could smelt wootz, but I have an experiment in the pipeline (thanks to an earlier post :-) )
It really depends on the size of your firebox and if the flames from the burner are forming a vortex.
Give me the details of the forge it's going into (if it's going into a forge at all that is). Is it for a forge application?
Regards Charles
Rusty_ir> Gday all,
Reply to
Chilla
The one I've heard is the force air type is easier to get up and running the first day. ;)
I wonder if that's really true if the naturally asprirated type is designed and ran at optimum? It's still just air and propane... unless they are talking some sort of pressurized setup?
Rust, got a little blower? Brand new ones ain't exactly cheap and the small ones I've found at the scrap yard lately were all 240v.
I missed that post somehow. :/
There's some sort of limit to propane's heat, especially diluted with air. It'll be interesting what you can do with it. :)
Hmmm... if you're down-under my voltage problem may not effect you?
The scrap yard's always got lots of little blowers in old central heat type furnaces, a good scrapyard will let you remove them and sell them to you for scrap metal prices. :)
Alvin in AZ
Reply to
alvinj
"bollocks to that" is exactly correct. I've done a lot of pattern welding with a venturi burner, no problem. I don't know if forced air would have been faster, I've never forged with a forced air burner. Preheating the air would definitely be faster, but I've never tried that either.
Regards,
Adam Smith Midland, Ontario, Canada
Reply to
Adam Smith
Let's see :
1. when you have a 3000 degree power cord for the blower 2. when you have to force more air than is reasonable 3. when you never have to be away from a wall plug.
Actually either way works just fine. Just be careful with the blower and power. Having a venturi it simply requires a gas source.
Might be nice to have it both ways - two torches. One for local work and another for use when you haul it over to charlies or to the club meet or ..... Sometimes those places are at the edge of a mountain where some ore is located, or other fun job.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member
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Rusty_ir> Gday all,
Reply to
Martin H. Eastburn
Charles, I've aquired some lengths of pipe, 10 & 12 inches in diameter, I'm going to put 2 1 inch layers of Kaowool, and coat it with ITC 100HT. pipe is currently 18 inches long but I may cut that down. I plan to build a smaller unit from the left over kaowool - its 7.2m*0.61m so there should be plenty left over from building 2 forges - to use for small stuff. I plan to put a fire brick in the bottom. As I have not constructed them yet, I'm still sorting details - like burner type - I don't know the exact volume.
Yes I know thats a fairly large forge, but i wanted a large unit to accomodate some larger work. I was thinking if i put 2 burners in, I could just use a firebrick or 2 to cut the internal size, and only run the front burner. Ok so perhaps I'm kidding myself or my thinking is faulty, I don't know yet. Thats why I'm asking.
Is there some rule or guide as to the number of burners per area within the forge?
Rusty_iron
Reply to
Rusty_iron
Alvin, central heaters are in short supply here in subtropical Queensland - Brisbane. But we have plenty of airconditioners, so perhaps I can get one from there.
Please post all your 240v units to Chilla and I, we use 240v here, like the British :-)
I have a nice new blower I got off the shelf while I was OS about 2 years ago, cost $20 pacific peso's. Wish I'd got a couple of them :-)
I have power to my smithy, and a handcranked blower if I need it. Portability would be nice and thats a good selling point. Thanks for the idea, its important, I'd not considered it. DOH!!!!! :-)
Rusty_iron
Reply to
Rusty_iron
Mitre 10 has a Fathers day special a 1 hp dust extractor for $99 AUD, just use it to blow instead of suck (I don't know about you guys, but I've got a dirty mind and this somehow sounds filthy :-) ).
Regards Charles
Reply to
Chilla
Hi Rusty,
Hmmm that's a big firebox, potentially 8 - 10 inch diameter x 14 - 16 inches long, that's going to require a lot of propane to heat up.
Let's see 352 - 503 sq inches, if you want to make that into a forge as is that will definitely require 2 burners to effectively heat it up.
I'm just thinking the only reason you'd want to heat up that amount of metal at one time is for heat treating, or the item is bulky.
What do you want to make? We might be able to design something a little more purpose built for your desired application, that wont cost a fortune to run.
There may be some rule about burners per area, but I prefer common sense.
I made the mistake of telling the blacksmith class how easy it is to set up a forge and now I have to make 5 portable modified propane tank forges. These will be able to make swords, anneal sheet for raising operations and be used as a melting furnace for non-ferrous metals.
I was tempted to buy a 7 metre roll of Kaowool, but thought I'd use up what I've got first. I did buy 10 litres of "Kaowool Rigidizer", and have found this to be an excellent product.
Anyway tell me what large item you want to make and we can design something appropriate.
Regards Charles
Reply to
Chilla
It depends on what you want the forge to do. There are ups and downs to both. I've got an old four hole Johnson that's set up for 'city gas' and forced air. It will get plenty hot enough to weld, about 3000 degrees on a cold winter day. It cranks out roughly half a million BTUs into a 24"x4"x 5" box. It has an 8" centrifugal impeller driven by a 1.5 hp electric motor at 1800 rpm.The fuel feeds into the compressor inlet through a 1/2" gas line. The upside is that I get absolute control of the atmosphere by controlling the fuel and the total air into the blower with a choke plate on the air inlet and a flow valve on the fuel. The down side is that it isn't portable. Methane, 'city gas', has more BTU potential than poopane, being a shorter chain hydrocarbon, and more reactive. Poopane has portability.
Atmospheric burners are limited in their output by several factors; fuel feed pressure, air inlet size, mixture jetting. Since air is entrained by the passage of the fuel through the venturi sectiuon, fuel pressure has a direct relation to how much air gets mixed, as well as jet size. Atmospheric burners are more 'finicky' about mixture, which has a direct beasring on flame temperature at trhe burner face. Even with a well engineered burner, you can get lass than desirable results if the box volume is not matched to the output of the burner, and this includes the design of the box exhaust as well. A fire that can't breathe won't get hot.
If portability is your more important factor, go with a venturi system that's been tuned by a professional builder, there are lots of good ones on the market. If you don't need portability, go with forced air and gain a wider range of operation parameters.
One word about forced air... don't turn your back on it until it's up to autoignite temp in the box. I've had flameouts, backfires through the compressor, hung starts, stuff like that. You'll want some sort of inline fuel interlock valve to cut the fuel flow if you lose power to the compressor. It's kinda like an early jet engine, sounds like one too. Air first, then add fuel, not the other way around.
Charly
Reply to
Charly the Bastard
Way too much air and noise if you sak me. (but you didn't ask me ;)
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(used RR signal-case blower)
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The holey screen was picked up off the ground at the scrapyard it's some sort of automotive exhaust system guard for them newfangled Cadillac;) converters.
Cut round, edges-ground all around to form an "edge" like a cold chisel, bent in one spot then screwed right into the pipe threads.
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Nothing but a stack of insulated firebricks. The darker yellow bricks are the "common, cheap and heavy" fireplace liners the others "feel like" styrofoam. Inside where you can't see it are 2 more insulated fire bricks for the "floor".
None of that stuff is prob'ly what you're needing, but shows you what's posible.
The first time I fired it up with the new insulated firebricks... tried heat treating a small O1 knife blade I didn't see the steel go through its "arrest point" so kept heating the knife blade. The O1 blade got so soft, it got all jiggly-n-wiggly. :)
I suppose that's hot enough for forge welding?
Search for- ron reil burner ...it's prob'ly the best way to go anyway?
Alvin in AZ
Reply to
alvinj
Good summary. My additions: 1.What Charly said about exhaust with a venturi forge is certainly true. But what this also means is that every time you move a firebrick around to close off the front door a little, you have screwed up the mixture somewhat. Many people don't realize the impact this can have.
2. Regarding flame-outs, etc. Some burners are more robust than others. SEE them work. See if they are fussy for the first couple of minutes. The one I use NEVER goes out unless there is an out of fuel condition. Even then, it takes many minutes of lower output before there is any danger of a flame-out. Once the forge is hot, even a temporary loss of fuel (someone steps on the hose) shouldn't be a problem because the forge should auto-re-light from the glowing insulation. Of course the safest system is one that shuts off the fuel if the pressure ever drops low, there's a drop of power, or if the heat goes down. And then the system won't resart without starting the lighting sequence from scratch, like a gas water heater.
Don't choose until you have seen both styles doing the heating the YOU want to do. Our group, the Guild of Metalsmiths is planning a "Gas Forge Clinic" to deal with this exact issue. It will be an event where the experts on both sides discuss (argue and hit eachother) why their way is the only way, and tell stories about their favorite designs. Actually, there are about a hundred different sides to this issue. The observers get to take all this in. ----We have been looking for people brave enough to head this up for about 3 years.
Pete Stanaitis ----------------------------
Charly the Bastard wrote:
Reply to
spaco
I have a single burner forge that is 8" inside diameter and 14" long. One burner is marginal, but it works. I haven't done any welding with this particular forge.
I used to have a forge with 10" ID and 24" long. It had 3 burners. This worked very nicely, worked well for pattern welded billets.
Both forges were atmospheric (Reil burners) and insulated with 2" Durablanket. I used some Satanite as a rigidizer, no ITC.
Steve
Reply to
Steve Smith
This link is busted :-( Charles
Reply to
Chilla
Ooops. :/
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Fixed. :)
Alvin in AZ
Reply to
alvinj
I mentioned the interlock because my unit feeds gas from the city main directly into the inlet of the comprrssor, and if the AC goes down there's nothing to stop a build up in the compressor housing and the manifold, other than the interlock. So far, I've been lucky, all I've lost are my eyebrows. Gas explosions can be catastrophic and deadly. Better safe than sorry, solenoid valves are cheap and reliable. Art is not worth getting blown up over. Since you mentioned low pressure conditions and someone stepping on the feed hose, I assume you're using Poopane.
Reply to
Charly the Bastard
'Compressor'? compressing the gas?
We're on a street where there is only low pressure gas (just a couple inches of water), the cost of a gas compressor and storage and compliance with all the regs was more than complying with the regs for coal.
Or are you managing welding heat with low pressure gas?
Or are you lucky enough to have a high pressure main?
- Carl
Reply to
Carl
ok I was basing my building on these plans for a start:
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I've seen pics of forges made from old gas tanks, but i don't have one to use, except one of the large size that are about 5 foot high. So based on this guys ideas I asked a mate for pipe offcuts in the 10 to 12 inch diameter.
I mentioned I intended to build a smaller unit while I was at it :-) but you are right it is a lot to heat. I've never used nor witnessed the use of a gas forge, so I only have what I've read on the net to go on. I have a coke forge that I've been using for years, and have found that extra space in the forge never goes astray, but its true I don't have to heat all of the space in the coke forge at once, which does not apply to the gas forge.
Hmmm you could make 6...... ;-) If I were you I'd make one as a demo and let them go for it, unless you are charging for each unit and making a profit out of it..... Your time is worth something.
Ok the guy at Thermal Ceramics told me it was a 7m role. He was only new there, so I ahve as yet to speak to one of their experts. What is this "Rigidizer" product? The Itc100 was recommended by a blacksmith i did a course with. Heres a pic of his setup.
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Thanks to everyone who has given me feedback, I appreciate all your comments and ideas, keep them comming.
Reply to
Rusty_iron
I've never seen that. :/
IME just the otherside of the meter and its 4 psi pressure regulator, the natural gas is like 125 psi.
Did I miss something?
Alvin in AZ ps- poopane, huh? :/ pps- well then, NASTY GAS to you! ;)
Reply to
alvinj
Wow that -whole thing- (website writing forge etc) is really cool. :)
The two bricks look like they were one brick sliced in two?
The roller is really cool.
What's "SG iron"? :)
Somehow I know it's going to be "duh, I shoulda knowed that". :/
Alvin in AZ
Reply to
alvinj

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