Please help me with my burner problems

S

Steinmann

Joined
Jan 12, 2010
Messages
99
Dear all,
I am studding burners for a few days now, and I'm having no success with my burner building. I'm facing some troubles and I will be thankful if it will be possible for you to give me some advice. Please find enclosed some picture of my setup: The pipe dimensions are written on them (a bit too small...). The gas I'm using is normal cooking gas (butane?) as I don't have access to propane, which I understand is the popular one in the states.
As you can see, I use a blower; the main problem at the moment is that I can not get a stable burners flame, more a regular cooking flame (that sometimes jump out of the forge opening). There is no "dragons breath" when I ignite the burner, I mean that the flame is just not strong enough. I tried everything regarding regulating, fine tuning and so, but just can't get the burner to give a classic blue loud burner flame. Often the flame that I have tuned (after hard work...) shuts off without any reason, and often it is burning in "pulsing", i.e. pulses of regular "kitchens cooking flame" that beats out of the opening. Sometimes I can smell the gas, and I understand that it is not totally burned.
1. Is this butane gas ok or must I switch to propane?
2. Is it possible to combine a venturi system into this blower setup?
3. Shell I drop the blower idea and switch fully to venturi?
I thank you very very much in advance and appreciate your time - Michael.

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Looks like it may be too small of a fan, or the fan may be restricted too much by the adaptation to the pipe. I'd eliminate the top bell reducer, run that 1-1/4" pipe back through a 1-1/4" tee and adapt that to the gas and air, without bottle-necking the air by adapting small.

How are you regulating the gas? I don't know about butane, but with propane and natural gas a blown burner does not need a small, precision gas jet. You will need to regulate it at the tank, something more sophisticated than just a valve. It sounds like your burner is running way fuel rich, so I'd work on increasing airflow and regulating the gas. Once you have high volume airflow, then you can regulate that by putting a 1-1/4" gate valve in line or even just putting a swivel choke plate over the blower intake.

Also, I'd suggest using a 3/4" burner tube, but it looks as if your forge shell is fairly committed to the size you already have.

Your burner tube is still threaded; I'd cut the threads off evenly and then de-burr the inside of the pipe. The tube looks a bit long, anyway. The result should be a more stable flame.
 
When I saw the fan my immediate reaction was the same as Salem"s - too little air.
Try a big hair dryer or the exhaust end of a shop vac with a gate valve at the
inlet.
Also, the 1/2" pipe should be at least 3/4" like he stated.
Lastly, we can't use standard regulators with our propane rigs. We use a 0-30 lb regulator.
Not sure about butane but I imagine it's a similar deal.

Good luck
 
Thanks guys; Do you think that a ventury system will be a better solution? Or can I combine between the two?
 
I'm by no means an expert, heck I don't even play one on TV, but it looks like the gas and air aren't mixing well enough. Kind of like a faucet without a mesh, the water doesn't mix well and one side of the water is hot and the other side is cold, with a little warm spot in the middle. Most torch heads have the little jets to force the gas to mix better with air. Perhaps putting a jet after the butane valve would force it to mix better.

Your butane isn't hot enough! While it has roughly the same BTU as propane, it doesn't burn well when cold. As the pipe heats up, it should do a better job of warming the butane and giving a more even flame. How long did you run your test firing?

Of course, this may all be jibberish, but it makes sense to me from what I've read over the last couple weeks.
 
I don't know about forced air burners but venturi burners need a flared tip on the end of the burn pipe to achieve a good mix of gas and air. They also need to be tuned differently to run inside the forge than they do in the open, the impedance of the exhaust creates some back pressure in the forge that changes the tuning a bit.
 
I'm not trying to be too blunt, but, there is more wrong with that burner setup than right...at least from a usability standpoint. The obvious has already been mentioned about not enough air. That is due to the incredible restriction being placed on the blower. Next, about the blower. That is what is commonly referred to as a "shaded pole" blower. Those type blowers do not work with back pressure....and due to the restriction in that setup, I doubt your getting 1/10 of the air flow that blower is capable of...and unless you build a gradual reducer, it simply won't work for you. (Shaded pole blowers are designed for use in situations with zero back pressure.....and if/when back pressure is present, it restricts the air flow, and will often burn out the motor in a short time)

The next thing that I see that raises a red flag is how small the actual flame tube is. I'm guessing that forge body has and ID of 8-10"? For a castable forge of that size, you need at least 1 1/4" dia (and preferably larger) "burner" tube.
I don't know how to say this without sounding upity, and it's not meant that way, but why all the different sizes/types of fittings? Forge burners are all about K.I.S.S. The more you overtake the plumbing, the easier it is to stop up the drain, and generally the less efficiently they function.

Next, I would recommend operating the forge on Propane rather than butane.....Butane is far more expensive, and produces few BTUs compared to propane.

Here's my suggestion:
This is the burner on my welding forge. It's been in use for about 20 years, and works very well on about 4-5 psi of propane. Starting from the bottom....a blower designed specifically for forges (available from Blacksmiths Depot), connected to a 2" pipe flange. (This blower is designed to be used in a back pressure situation) The pipe flange is connected to a piece of 2" X 12" black iron pipe. That is connected to a 2"x1 1/2" 90 degree elbow (also black iron). The next piece (at goes into the forge) is 1 1/2" x 12" black iron pipe. The gas inlet is drilled/tapped into the section of 2" pipe near the blower.
The important parts of this design are the blower....it's designed to work with back pressure. Also, the pipe necking down from 2" to 1 1/2" at the elbow, this changes the velocity of the air/fuel mix, causing the mixture to "tumble", which achieves a better air/fuel mix before hitting combustion.
GET RID OF THE GALVANIZED STUFF! NEVER USE ANYTHING GALVANIZED ON YOUR FORGE...IT'S A SERIOUS HEALTH HAZARD
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Whatever you do, realize that your burner components need to be matched in size to your forge, and forget all the "bells and whistles" when it comes to a forge burner. Simplicity is the key to designing a trouble free, usable forge burner.
 
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Ed, I like your simplicity of design. What are you using at the burner tip for the back pressure? Do you have a baffle on the tip?
 
Hi Bruce!

The burner tip has 3" of concentric pipes inside the main 1 1/2" pipe. There is the 1 1/2" pipe, inside that is 3" of 1" pipe, inside that is 3" of 1/2" pipe, and inside that is 3" of 1/8" pipe. It helps a little with the flame pattern, but it's main function is to tone down the roar the burner produces without the concentric pipes.
 
Ed, I don't think he has as easy of access to propane as we do since he is in Isreal. He mentions "regular cooking gas" so my thought would be natural gas, perhaps. I'm glad you mentioned the concentric pipes. I was wondering if that was necessary. Would pieces of wire screen perform the same function?
 
Natural gas has even less BTUs than butane.....that would be going from bad to worse....but I suppose if a person has no alternatives......

Screen might work for the first few minutes, but because of it's light gauge, I suspect it would quickly melt away. About the only method I could figure out to attach the concentric pipes was by placing a "spacer" between them, then tack welding right at the end of each piece of pipe......stepping the tack weld outward until everything was tacked to the 1 1/2" "burner" pipe. To date, about once every 3-4 years I have to replace the 1 1/2" section of pipe because the end with the concentric pipes gets eroded away from the heat. About the time 1" or so of the burner pipe gets eroded away, the forge will really start roaring, and I know it's time to replace things.
 
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