Gas forge out of propane tank

[Nanafalke]

Hey,

a few weeks ago, I started building my first gas forge. I live in Germany and we got those 11kg propane tanks that make a good shell for the forge. For the isolation I use ceramic fibre and fire cement. Of course I used a respirator while working with the fibre. 

Here are some pictures: 

And a little stand:

Yesterday I isolated the tank:

I shaped the interior room oval, I read, that this shape has it's advantages in the Forges 101 thread. If I would build it again, I would probably have moved the burner hole a bit further to the opening, because I put more material in the backside. Now I let it dry 2 - 3 weeks and then I will weld two u-profiles to the front to be able to close the opening with a firebrick and two pipes to the side for a workpiece holder. 

Feedback is highly appreciated

Best wishes

[Exo313]

Someone is going to jump on the words "fire cement" before long, given that in the US and Canada we have a range of products in the fireplace mortar/cement category that are less than ideal for forge lining. 

That said, I'm curious to know what you used, given that product availability is likely different in your area?

[Mikey98118]

If you used refractory mortar/cement, it isn't too late to overlay it with a light coat of castable refractory or Plistex, etc. Basically, mortar/cement isn't able to deal with direct flame impingement. That said, what's done is done, and you should just move forward.

You are wrong about moving the burner closer to the exhaust opening; it is common to see forges with the burner close to this opening; that doesn't make it right; it just means we get tired of pointing this out. Intentionally or not, you put the burner in the right place; don't move it.

[Jackdawg]

Looking very nice.

What are you going to use it for? Finding yourself a firebrick or two to sit inside as a floor that your stock can sit on can be helpful to make the lining last longer. Also acts as a sacrificial floor if your going to use borax. I made a flat spot in mine to support a fire brick, but have not got around to getting one,the flat floor is doing okay, but definitely starting to powder up where I scrape and scratch it with the stock going in and out.

[WayneCoeArtistBlacksmith]

Too late but check out the Build a Gas Forge attachment at the Forge Supplies page on my web-site.  You can fine the url and other contact info on my profile here.  I prefer e-mails.

Let me know if I can help you.

Wayne.

[Nanafalke]

Thanks a lot for your feedback  

21 hours ago, Exo313 said:

That said, I'm curious to know what you used, given that product availability is likely different in your area?

19 hours ago, Mikey98118 said:

 Basically, mortar/cement isn't able to deal with direct flame impingement. 

I used [commercial link removed]. The website is in german, but to sum up, the cement is used in blast furnaces, able to withstand 1600 C (2912 F) and can store heat. 

The cement is recommended by many people from german blacksmithing forums, so I have high hopes that it will work as expected. 

19 hours ago, Mikey98118 said:

You are wrong about moving the burner closer to the exhaust opening; it is common to see forges with the burner close to this opening; that doesn't make it right; it just means we get tired of pointing this out. Intentionally or not, you put the burner in the right place; don't move it.

Good to know, thanks  . True, all images of forges I saw so far either put the burner in the middle or closer to the opening.

I intentionally put the burner in the middle of the forge, but because I did reduce the size, the burner moved back in respect to the interior room, unintentionally. 

18 hours ago, Jackdawg said:

Looking very nice.

What are you going to use it for? Finding yourself a firebrick or two to sit inside as a floor that your stock can sit on can be helpful to make the lining last longer. Also acts as a sacrificial floor if your going to use borax.

 

 Thanks .Im planning to forge blades and tools (tongs), maybe axes one day, damascus steel would also be interesting. Yeah, definitly using a firebrick for the floor, especially when forging damascus. 

14 hours ago, WayneCoeArtistBlacksmith said:

Too late but check out the Build a Gas Forge attachment at the Forge Supplies page on my web-site. 

Going to take a look, thanks  .

 

I tried running my new burner, but sadly, it doesn't get enough oxygen. Probably have to enlarge the air intake. 

 

Best wishes

 

Edited May 20, 2018 by Mod34
Commercial link removed per TOS

[Nanafalke]

Hey,

after studying for some class tests, I finally had time again to work on the forge. 

I tested my burner in the forge and the flame seems to rotate pretty good: 

 

 

Sadly, my burner design doesn't burn hot enough as you can see here:

 

So I replaced the 1mm nozzle from the gas torch with a 0.6mm mig tip and that already worked better. Then I removed the shroud and just put the nozzle in the pipe, fixed by two screws: 

That resulted in this flame: 

In the beginning it is burning at 0.2 bars (3 psi) and then I increase the pressure to 1 bars (14.5 psi). 

Do you think it is burning right in the last video? 

Thanks alot

Best wishes 

 

[Nanafalke]

Hey,

I think I will take a few shots at night when I have time again, so the flame is more clearly visible. 

Best wishes 

[Mikey98118]

I don't see a second video; only a photo. The flame in the photo isn't as good as that kind of burner should produce, but it is good enough to run a forge. I would say that your main problem is the burner's flame retention nozzle. Go to Hybridburners.com to see the burner design closest to yours, and then pay close attention to the flame retention nozzles you should be imitating.

[Nanafalke]

Thanks for your feedback. Actually, there are 3 videos and there is no picture of the flame. Maybe you refer to the preview image of one video? 

I searched for a 3/4" burner on hybridburners.com and found this. Is the part I marked referred to the flame retention nozzle? 

 

I properly mounted the propane supply with 6 screws now and tested again.

Here are the results: 

 

If you can't see the vimeo videos, here are the links:

https://vimeo.com/272741216

https://vimeo.com/272741527

Picture of the flame, 0.2 bars

If the burner doesn't burn as hot as expected, I still can convert it to a t-burner. Just thought why not try building one with parts I already have at home. 

Best wishes

 

 

Burner at night.mp4

Burner light.mp4

[Mikey98118]

No; the flame retention nozzle (AKA nozzle) is at the forward end of the burner, and is the stainless steel part. Meantime I have seen a much worse problem on your burner; you only have a plain short MIG contact tip. You need a long tapered contact tip; this problem is aggravated by the hex nut holding the tip in place, but the right tip would probably do okay despite this other problem.

[Nanafalke]

So the flame retention nozzle is basically the flare? Or is there still a difference? 

I'm also not that happy with the current setup, if a long tapered tip doesn't improve the burner, I will just convert it to a T-Burner. 

Now I have to find those long mig tips, they are not that common here. 

Thanks a lot for your help

Best wishes 

 

 

[timgunn1962]

Several designs call for a "flare", usually with a 1-in-12 taper. This is the empirically-determined "optimum" taper for the downstream section of a classic Venturi. 

In most forges, neither a flare nor a flame retention cup is usually necessary (though they can be advantageous in some cases).

At the inlet end of the (Naturally Aspirated) burner, fast moving gas exits the jet and a low-pressure zone is created around the jet which draws in the surrounding air.

If you run a NA burner in open air, fast-moving gas/air mixture exits the burner and a low-pressure zone is created around the burner exit which draws in the surrounding air. As the burner is turned up, the flame tends to detach and go out. If you apply a flame from something else to the edge of the burner nozzle, the flame will usually light and remain attached for as long as the pilot flame is present.

If you move the same burner into a forge, the mixture still emerges from the burner and still generates a low-pressure zone, but in the closed forge there is no air to be drawn in, but there is a lot of flame. This is drawn in towards the burner nozzle and keeps the flame attached.

As I understand things, a flame retention cup works much like a forge-in-miniature, causing a donut-like ring of flame to form on the "shelf" where the diameter steps up, keeping the flame attached. I make my flame retention cups with a short length of pipe twice the size of the burner tube and odd bits of intermediate-sized pipe to fill the gap between them: loosely based on the design shown in http://amalcarb.co.uk/downloadfiles/amal/amal_gas_injectors.pdf.

I have found these retention cups work well when a burner needs to be run outside a forge.

 

[ThomasPowers]

I've always considered it a balancing act: Gas speed Vs Flame propagation speed.

 If Gas speed is slower than flame propagation speed then the flame wants to travel up into the mixing tube.  

If the gas speed is faster than the propagation speed then the flame tends to be blown off the end of the mixing tube.  

The Flare provides a graduated change in gas speed as it slows as it has greater crossectional area for the same amount of gas to travel through and so at one point you get a balance between gas speed and flame propagation speed providing a steady state and a steady burn.

[Nanafalke]

First of all, thanks a lot for your explanations. 

On 1.6.2018 at 12:31 AM, timgunn1962 said:

As I understand things, a flame retention cup works much like a forge-in-miniature, causing a donut-like ring of flame to form on the "shelf" where the diameter steps up, keeping the flame attached. I make my flame retention cups with a short length of pipe twice the size of the burner tube and odd bits of intermediate-sized pipe to fill the gap between them: loosely based on the design shown in http://amalcarb.co.uk/downloadfiles/amal/amal_gas_injectors.pdf.

I have found these retention cups work well when a burner needs to be run outside a forge.

 

The burner doesn't need to be run outside, I just did it for testing. It would probably be a good idea to put the burner in the forge and see how it performs. 

 

On 31.5.2018 at 9:51 PM, Mikey98118 said:

You need a long tapered contact tip

Sadly, I can't find those here in Germany. The only ones available are these tapered but not long ones. Not sure if they will work aswell. 

Best wishes 

 

[Mikey98118]

Okay, in the absence of the right tip, that short tip can be made to serve by increasing flow inside the gas pipe to tip interface. Change out the locale equivalent to 1/8" schedule #40 pipe to 1/8" schedule #80 pipe. The increased streamlining of gas flow at the joint will permit the shorter tip to serve.

If you also can't find the preferred gas pipe, then you can braze a heavy wall stainless steel "gauge" tube with an inside diameter of about .030" inside diameter into the tip to bring it up to the right length (1-1/2" length of bore).