Forge trouble

B

bubbyh

Active Member
Hello, i am wanting some info on my burner for my propane forge. I have made a basic venturi style with plumbing pieces etc. I just cant get the steel to welding temp. I used a 20lb propane bottle for the body and lined with 2" kaowool then topped that with refractory. It insulates well but i would like to know if you should have a in-line shutoff valve between the burner and the tank and what kind of regulator?? Hi pressure or low??

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How big is the venturi burner? 3/4"? 1"? x how long? How big is the "bell" of the venturi?

Part of the issue may be the fact that you are using 2" of kawool. Contrary to popular thinking, 2" of kawool does not provide better insulation in a forge application then 1". I know that sounds wrong, but its not. Compared to 1" of #8 density kawool, 2" requires more fuel to achieve and maintain the same temp versus 1" kawool. Kawool (or any other blanket type refractory) is designed to absorb a specific amount of heat before it starts reflecting.... 1" absorbs less heat before it starts reflecting, and reflects more heat then 2".......which is why 2" requires more fuel to achieve and maintain the same temp when compared to 1".

OK, that being said, some more specifics are needed to help you solve the issues.....a pic with description would go a long way. It could be any number of things, from the configuration of the forge/burner, to the size of propane tank that provides fuel to your forge.

Concerning the shut-off, personally on all my forges, I have a ball valve where my propane pipe comes into my shop (in your case that would equate to at the tank, then an adjustable regulator (0-30psi), and then a propane needle valve that provides adjustability/shut-off capability just before the fuel nipple that goes into the burner. There are so many different parameters from company to company calling a regulator "hi" or "low" pressure, that its really impossible to just say "get a hi pressure" or "get a low pressure" regulator.
 
EdCaffreyMS said:
How big is the venturi burner? 3/4"? 1"? x how long? How big is the "bell" of the venturi?

Part of the issue may be the fact that you are using 2" of kawool. Contrary to popular thinking, 2" of kawool does not provide better insulation in a forge application then 1". I know that sounds wrong, but its not. Compared to 1" of #8 density kawool, 2" requires more fuel to achieve and maintain the same temp versus 1" kawool. Kawool (or any other blanket type refractory) is designed to absorb a specific amount of heat before it starts reflecting.... 1" absorbs less heat before it starts reflecting, and reflects more heat then 2".......which is why 2" requires more fuel to achieve and maintain the same temp when compared to 1".

OK, that being said, some more specifics are needed to help you solve the issues.....a pic with description would go a long way. It could be any number of things, from the configuration of the forge/burner, to the size of propane tank that provides fuel to your forge.

Concerning the shut-off, personally on all my forges, I have a ball valve where my propane pipe comes into my shop (in your case that would equate to at the tank, then an adjustable regulator (0-30psi), and then a propane needle valve that provides adjustability/shut-off capability just before the fuel nipple that goes into the burner. There are so many different parameters from company to company calling a regulator "hi" or "low" pressure, that its really impossible to just say "get a hi pressure" or "get a low pressure" regulator.
Click to expand...
Very helpful, i will take some pics of my setup ed.
962077d786872edd9ecb88ec23bb2386.jpg
741a4c75b40c463c78ca4cb3f43415df.jpg

It is a 3/4" pipe 8 inches long with 1" to 3/4 inch reducer on top as u can see in pics. I bought the regulator at tsc and it just said "high pressure" so i bought it, lol. It will get the steel hot enough to forge but not enough to try some damascus and such, very frustrating!! Ive tried everything, so ive been using the coal forge outside in the snow and that sucks, as it is 20 degrees here in ohio!! Any help is very much appreciated!

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It's been a few years since I built my forge, but it is similar to yours. It's a little larger propane tank, with two burners, of similar design. The following are a few things that come to mind:
A pressure gauge would be good, so you could see how much pressure you are running. If there isn't any port on that regulator to install a gauge, I would add a TEE fitting right after the regulator.
Where did you get the plan for the burner? Did they specify how big of a forge chamber that burner would be suitable for?
I assume that the brass 1/4 inch pipe that runs through the bell reducer has been drilled with a specified drill size to act as an orifice. ?-if so, it could be that it is not tuned or aimed the best it could be. Or possibly a next-size larger orifice would be an option. I 'tuned' my burners outside of the forge, clamped in the vise, prior to putting them in the forge. As I remember, that made it easier to center the flame.
These are some things I would check into or try.
Good Luck with it,
Bill
 
Thanks bill, i used a #60 drill bit for the orifice and i have lined it up to the best of my abilities. I watched a video on youtube for the burner and it is a ron reil style i believe? It works, its just not getting as hot as i would have hoped. Maybe 2 burners would help?

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Morning Bubby!

I looked over the pictures you posted, and a couple of things jumped right out at me. First is the burner..... my rule of thumb for a venturi burner is a minimum 2.5 to 1 size ratio...meaning that the "bell" should be AT LEAST 2.5X larger then the burner pipe. In this case you have a 3/4" pipe, which means the "bell" should be AT LEAST 2". A burner will operate with something like you have, but is severely limited in it's output. In order for a venturi to produce the level of heat you need for welding requires more fuel and oxygen then your current configuration is capable of. What I believe you're going to need is a 2" or larger "bell reducer', and you're likely going to have to increase the orfice size to at least a #53.... or larger. Even with those modifications, its likely going to require 10-15psi of fuel pressure, and possibly more. This often creates problem for folks who use the small (20lb) propane tanks/cylinder for their fuel supply. Usually at the psi you need for welding heat with a venturi causes the small volume tanks to freeze up by the time they are 1/2 empty.

Another thing that I would change on the forge is the position of the burner. In my opinion it should be on more of a tagent...... like this....


The whole idea of using a round design for a forge is to create a "swirling" flame inside the forge......this helps eliminate hot spots, and more evenly heats not only the forge, but the work piece too.

There are number of "ways" you can come at this situation, but having been at this for many years, I believe that if a person is going to "weld" with a forge, trying to do so with a venturi burner is just making things hard on yourself. IF you think that forge welding is going to be part of your routine, and you're only going to have one forge, my suggestion is to build a forge with a blown burner. You can dial it back for general forge work, but it makes things much simpler and easier when you require welding temps.

Personally, I have dedicated forges for both general forging (a venturi burner model), and for welding (a blown burner model). Again, in my opinion, if a person is only going to have one forge, and they even THINK they are going to want to forge weld, then that forge should be one with a blown burner design......something like.....



Hope thats helpful!
 
Bubby-Your build looks good, clean, well done. Maybe adding a burner or even adapting to a blower is your answer.
I also noticed, as Ed said: the smaller bell reducer. Mine has a 3/4 inch pipe for the burner and a 1 1/2 inch bell reducer at the air intake. And even that is less than what Ed recommends. I also have a flared 1" pipe at the discharge end of the burner.
I also noticed the angle of entry being less than mine. My burner enters at an angle probably between where yours and Ed's are- probably almost angleas Ed;s picture- to get a swirl of the flame. My forge is about 18 inches long and 12"wide (OD) 2" of kaowool and coated with metricote. It has no problem getting to weld temperatures. The problem I am having now is I don't have a choke on the air intake and seem to be running a somewhat oxidizing flame. I think, with my very limited experience, that I am creating too much scale. So, I'm going to add choke plates to the intakes and see what that does for me.
Anyway back to yours- I think I would try a larger bell reducer, or adding another burner, go all out and convert to a forced draft type.
But it would also drive me nuts not knowing for sure how much pressure I'm actually working with - so either way would add a gauge to the regulator.
Bill
 
Bill....... without changing anything else on your burner, its very likely that the oxidizing issue can be solved with a slightly larger orifice.....doing so will allow for a bit more volume of fuel. You MIGHT have to bump the pressure up very slightly, but otherwise with keeping all other things as they are, I suspect you can solve the oxidizing atmosphere issue. What a lot of folks don't understand about venturi burners is that the sizes of the burner pipe, the "bell reducer", and the orifice all need to be "balanced" for the particular size forge you're using the burner in. The fuel pressure coming out of the orifice is what creates a vacuum, which draws air into the "Bell reducer"......and all the aspects have a bearing..... orifice size, fuel pressure, and the amount of atmosphere that can in drawn into the "bell reducer".
 
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Thank you very much bill and ed!! I will try a bigger bell reduer first with maybe a slightly larger orfice as you both stated. If i cant get it lined out, at least it still can be used as a everyday small forge as it has no problem getting to forge temps. I could use it for regular forging and maybe start building a new forge as u both mentioned with a forced air setup for when i want to weld. I also failed to mention that I use a 100lb cylinder to power this. I also posted another thread on my coal forge i have made and is is totally new to me but very hot!!! No problem with weld temps in it, lol. Once again, this is why i joined this group, because of fellars like yourselves, so that being said, thanks again

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Good luck with it Bubby- at least you have your coal forge (just kinda cold out there tho?!) I know I sound like a broken record, but if it were me, I would still put a gauge on your forge to know what pressure you are actually getting out of that mystery regulator. It may not be causing a problem, but at least then you would know for sure.
I don't want to hijack this thread, but Ed- thx. I have been working on a damascus billet with my son (first time) and it seems that I'm getting an awful lot of surface scale. One concern is that the billet is getting considerably smaller- I assume from either too hot of temperatures causing the steel/carbon to actually be burning away- or from the flame being too oxidizing. I'm thinking I should be more focused on getting hot enough, but not too hot. I forgot to try touching the steel with a thin rod. Do you ever do that? -or does your experienced eye just tell you how hot is just right for a weld?
I'm going to add a few layers of 1095 and 15n20 to get the mass back. I think I will still add choke plates to the burners to experiment with, but I will also order some drill bits that are a step up from what I have.
Thx,
Bill
 
Its all good bill, i learn from everyones posts! Nothing but helpful

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I may have missed it but did anyone mention a nozzle flare? My venture burner wouldn't get hot without one. It's also part of the fine tuning.
 
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