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Blown burners, the care and feeding


Geoff Keyes
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It sounds like you are starting to burn your steel.  Maybe you might want to cut things back just a tad and see how it still welds.  My experience, little that it is, is that forge welding will eat up your gas.

Doug

HELP...I'm a twenty year old trapped in the body of an old man!!!

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I'd dial back the air, then the fuel.  Sparks mean too much air.  And yeah, maybe a smaller burner tube too.  350ci isn't that big.  That said, two solid days of welding will drink a full 100lb tank.

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Thanks for the quick suggestions.

 

The sparks came after the third fold and the weld wasn't really taking, so I went a little overboard with it. But I'll try backing off a little bit the next time I'm at it, and if it still seems high I'll probably give a smaller tube a shot.

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Simple equation. More heat takes more fuel + getting hot faster takes more fuel = running hotter and faster takes more fuel. 

But, what's already been said, if you are throwing sparks you are running too hot with too much air.

This actually points out something, as a venturi guy, that I believe. A blown burner is not automatically more fuel efficient than a venturi. There are so many variables that it would take an expensive testing lab and a lot of time testing both designs until they were both optimized, in forges optimized for each type in order to find ANY significant difference. Without that testing IMO it is a matter of initial building issues, tuning, and personal preference, rather than any empirical choice.  With the variables involved in all of our various forges it's more a matter of what the individual THINKS they're getting and their motives for the choice. If it keeps people forging then it's all good anyway. 

 

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  • 7 months later...

I have had a forge of the same design for several years now. I used to be able to get clean welds with it but I cannot anymore due to an oxidizing atmosphere. I've re-lined it with new kaowool and castable  refractory. Idk what the deal is. Does anyone know how to prevent an oxidizing atmosphere?

Thanks, Chris

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Rich-en your mixture, when it's oxidizing there isn't enough fuel in the mix for a neutral

environment...........feed it some more beans, or cut some air flow.................;)

Edited by Clifford Brewer

If ya can't be good don't git caught  !!                                        People who say stuff can't be done need to

                                                                                                        git the hell outta the way of people who do stuff   !!!

Show me a man who is called an expert by his peers         

And I will show you a good man to listen to ......

Show me a man who calls himself an expert

and I will show you an egotistical asshole...............!!

 

                             

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Make sure you have a decent amount of dragon breath from the mouth of the forge. This is a good indicator of a neutral or slightly reducing atmosphere. And if your running low on fuel I wouldn't even attempt a weld. But too much flame from The mouth of the forge and your just dumping carbon monoxide in the room.

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  • 2 years later...

This might be a dumb question… and I apologize if it is. 

 

This is a burner I bought a while back when I was just using a simple brick forge for heat treat. Currently building a new forge with a blown burner. 
If I were to use this line and regulator for the propane tank attachment, would I be able to attach that to the needle valve? Or maybe I could somehow use that part I’ve circled in red as that’s what the hose connects to? 
 

Sorry, I don’t know anything about all of the fittings and connections being used. 

FAA4AD45-123A-4324-AC61-05D22A66249A.jpeg

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Having spent FAR too much time replacing all of the fittings on my copies of that circled item... Learn From My Fail :)

 

That is a 3/8" 90 degree male NPT to 3/8" male flare elbow.

 

NPT is what most of us would consider a "normal" pipe - slightly tapered so it gets tighter as you go, but otherwise looks straight. 

 

Flare is that weird beveled thing.

 

I would strongly recommend you get a parts list from someone who's figured out the easier way to do it or you run a high risk of spending a lot more money than you intended and end up with a bucket of oddly shaped brass parts that you will very likely never use again.  Wayne keeps nudging you for a reason ;) If I'd have known about his site, I would have donated less money to various suppliers of brass parts.

 

But if you want a steampunk forge, you can adapt that thing you circled in red - there is a certain fun look to what you get at the end. It did take a lot of soapy water and re-tightening to get it right, though. (and one stupid valve put the wrong way by mistake *sigh*)

 

steampunk.jpg

 

Edited by Ted Stocksdale
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Ted's right, that's a flare fitting, and to use one properly you need a flare tool for copper line.

 

That said, your current regulator and hose should screw right into your needle valve.  If said needle valve is what connects the gas line to the burner tube, you're now good to go.  Blown burners are great because there's no need for tiny orifices, aligning gas jets, and so on. Just dump gas into the tube and away you go! Most folks just use 1/4" to 1/8" copper refrigeration or brake line with a compression fitting like on a refrigerator icemaker line.  You will also want a 1/4-turn WOG-rated ball valve between the forge and the regulator.  This is a safety thing, since if something goes wrong you just slap the handle closed and boom!  No boom. ;)

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Thanks guys, I was trying to come up with a way of saying what you just said, except I would have used a bunch more words and still been not as clear.

Geoff

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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Thanks Alan! I appreciate the tip on the ball valve. I’m overly cautious with all of this because I have a somewhat irrational fear of explosions. Not quite a phobia.. but enough to make me cautious and somewhat nervous of building my own burner. Anyway, I appreciate any additional safety tips.
 

The more I read, the more I’m starting to appreciate the simplicity of a blown burner. It makes me feel more confident building one. 
 

 

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You're taking pressurized flammable gas, lighting it on fire, and then supercharging it.  No shame in being careful.  It's even ok to be slightly afraid (aka terrified) the first couple times you light it up!

Edited by Alex Middleton
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2 minutes ago, Alex Middleton said:

 It's even ok to be slightly afraid (aka terrified) the first couple times you light it up!

 

Actually, it's when you stop being slightly intimidated to light it that you should start to worry.

-Brian

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  • 5 months later...

Just converted from a venturi to blown and woah buddy, it made a huge difference in the temp I'm getting.  I was able to get steal up to melting with ease.  (May or may not have been intentional.:unsure:)  Looks like I'll be relining the forge this weekend.

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I'm glade that worked out for you.  Post a picture of your setup, please, as a help to the next guy.

 

g

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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  • 4 weeks later...

Here's what the set-up looks like.  I used a blower that I got from a grooming salon that went out of business and did things a little different due to power access.  

My burners started life as Zoeller sidearms and I just removed the mig tips and plumbed the air right into them.  There's an air dump just before where the line splits that has an added boon of giving me a great place to stand when I get a little too warm.

IMG_20211023_083744232.jpgspan widgepan widget

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On 5/27/2018 at 8:33 PM, Alan Longmire said:

I'd dial back the air, then the fuel.  Sparks mean too much air.  And yeah, maybe a smaller burner tube too.  350ci isn't that big.  That said, two solid days of welding will drink a full 100lb tank.

 

I have now used my new forge enough to be able to calculate, we have tanks which are 33 kg or in your units round 72 pounds.  That actually was enough for two solid days of welding or in my calculations of 15 hours where I didnt attempted to spare fuel.  I have put a choke into the gas line, drilled 2,5 mm.  My thinking = original double T rex forge had injectors from 1 mm mig tips.  2 holes 1 mm diameter are about 6X less than  one 2,5 mm.  When I was welding I was cranking them 1,5 bar or almost 2 bars. Now I register about 0,4-0,5 bar on my ventil against that choke, that is 6Xless through area six times as big when I run the forge white hot. It makes it easy to set up the gas, when I actually have readable pressure.  However, this forge can litrally melt the billet and ruin it, the old one was always little too cold, because the jet flames were actually ventilating the heat out of the oven. 

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