Burn baby burn

[jsurgeson]

Thought I would post a short video of my latest freon tank based
forge and 1" burner.

I am really looking for comments from the experts on the quality of
the burn with regards the ability to weld, you will notice my temp
indicator shows 950 odd deg C, that is after 10 - 15 mins at 10psi

[maddog]

Great little forge. The pyrometer sensor is on the cold side of the forge and the temp there is just below welding heat. With a little coaxing you should be welding. With that size burner and that pressure, you may be overdriving the chamber. There seems to be a cold spot in the center where the flame hits the wall on the right. It might get hotter if you dropped the gas pressure. I'm guessing that you left the front wide open to give a view of the burn in the chamber. Blocking up the front some to reflect back the radiant heat and also make the combustion gas do more than one half turn before it exits, it should get xxxx hot everywhere. Is this an early firing? I find forges get quite a bit hotter after a couple three firings, especially if they are coated with ITC100. Should be a great forge. I love propane tank forges.

[jsurgeson]

Cheers maddog

Good observation, correct were the flame hits the opposite wall there is a circular
cold spot. The thermocouple when pushed in so it is in about 3/4 way across only reads
about 80 degC higher, so I think i am still short.

I am going to also do a 3/4" burner version as I think the 1" as you say is
overdriving it a bit, will play with pressures a bit as you suggest.

Left front open as I thought that was the standard design of the freon tank forge,
are you suggesting a temporary block while heating to temp, or to rather not cut the
front port as big in the first place?

Yes it is only the 3rd 15 min burn.

We don' get ITC100 here in SA but have an equivalent product that I have used.

Thanks for the observations and comments :D

[maddog]

At forging temperature, the main factor in heat transfer is radiative. Meaning the forge sheds heat in the form of light at a tremendous rate. That big opening is draining a huge amount of heat from the little forge. You need to set up a barrier of fire brick, for instance, to reflect back the heat. It doesnt have to be air tight. You can set it an inch in front of the forge mouth. You can't stop the exhaust from escaping anyway and you don't want to choke an atmospheric burner. Here are some examples.
.






It should make a very big difference.

If you have one, I think a 3/4" burner would be a better match. Though it looks like the 1"er is working okYou should get a smaller or no cold spot depending on the setting and you will be able to idle at a much lower setting. If you turn down that big burner too much, the flow in the tube will slow down to the point where it will burn back and start popping.

[pkrankow]

How is the paint on the wall behind the forge?

Nice looking kit.

Phil

[Nakedanvil - Grant Sarver]

Right on Maddog! Use the burner to heat the walls. AND don't point the burner at the work. As you can see here, the coldest spot in the forge is where the flame hits. Combustion is not yet complete, so you have unburned gas and hot oxygen and it is not as hot as the rest of the forge. That's why I like to come in tangent and let the flame swirl. Tangent is just like the outlet on most blowers.

[jsurgeson]

maddog:
Thanks I will fashion a "front door" to reduce heat loss. The 1" runs from
1 - 30 psi without burning back or popping off. However it is still not
tuned right.

Phil:
Taking strain, I can always repaint

Nakedanvil:
Not too sure how I can come in at any more of a tangent, but it still does not
seem to swirl much, any suggestions on how I would change the burner position
to achieve this?

Still have to work out how to tune it perfectly, I dont have a needle valve on
the gas, so only have pressure and not volume to adjust on gas, and air choke.

Here in SA I have been unable to find a reasonably priced one, R1000.00 ($145)
too rich for me. Cant find an industry here that uses them other than high spec
laboratories.

After some comments by a "clock maker" friend, I think I am going to have to remove
my internal flame stabilizer and go with a flare, just need to find a way to produce
one that works well looks half decent.

[Dodge]

I can appreciate this phenomenon. I did in deed find that you can actually make a forge run colder (relative term of course ) by turning up the pressure; and in my case with a forced air burner, the air supply. By accident, in an attempt to save fuel, I found I was getting steel hotter at a lower pressure. In fact I melted a piece at less than 3 psi because I wasn't paying attention LOL.
BTW, Nice forges guys!!

Scott

[jsurgeson]

Did a few of the suggestions and did another trial run:

1. Removed internal flame stabilizer and fashioned flare like shape into wool
2. Closed up front and back 80% with temp wool
3. Sealed up around burner holder with wool

Result:

Just short of 1200 degC in under 10 mins, small section of shed40 1" distorted in under 5 mins
Burner will not run outside of forge anymore, dont think this is a big deal. And is a bit spluttery
below 2psi but still runs.

A few questions:

1. My choke stays 100% open, 30% - 100% make very little difference to the burn, less than 30%
flame is softer and richer (green)

2. Outside of body is hot, too hot to touch, you can see around burner holder getting red hot, is this normal?

[maddog]

10 mins to full welding heat! Looks like you are cooking with gas now!

I confess I am a bit jealous of your hi temp pyrometer. I suggest you use it to train your eye to read the colors in your forge.

I don't know about shipping to SA but needle valves are available on ebay for $20 or less. Needle valves on ebay

Like you I dont use a nozzle when the burner is in the forge. I find they just corrode away. I shape the refractory to channel the gas. If you need to use the by itself, put the flare back on.

In this setup the burner and the forge are all part of a single venturi system. The burner has to be tuned to the forge and that will depend on how you have it set up at any time. How is the front blocked off. What kind of work piece is in the forge etc.

The relationship between the choke and the combustion mix is complicated. On mine it, at 20 psi I can set the choke down to 25%. At very low pressures when the air entrainment is not as strong, I need to open the choke to get a neutral burn. I just do it by experiment and experience. When you get the exhaust looking right for a neutral burn, do fine adjustments based on the amount of scale that gets formed on the work piece. Atmospherics often burn hottest running a bit lean. I like to set mine a bit lean and then kick up that gas a notch when the work goes in, to reduce scaling.

To get a tangential alignment, your burner probably needs to point in horizonataly and perhaps slightly backwards. If you switch to a 3/4" you may have enough space to change the angle. Anyway this is a refinement. What you have now is working great.

The forge shell will get hot enough to boil water. Some configurations will get hot around the burner entrance. This is more likely if you have a tangential entry. Make sure this is not due to combustion gas backing up through the burner port and flowing into the kaowool lining. Your lining will deteriorate fast if that happens. Seal the burner tube by packing it with kaowool. It is likely that the end of the tube will start to corrode. I just consider it a consumable and replace the nipple every so often. You can coat it with ITC 100 to slow down the process.

The kaowool barrier in front is a good proof of principle but it wont last long. You need to decide on a configuration. A moveable door lined with refractory or a stack of soft firebrick or whatever. I like the firebrick because its versatile but the bricks fall apart. Any opening through which you can see directly into the forge chamber should be as kept as small as reasonably possible. Line of sight is a direct escape path for the radiation.

I find it very useful to have a firebrick porch at the mouth of forge and place the reflecting barrier on that. This allows me to lay long pieces across the forge mouth without having to thread them through the chamber. I guess if you are just doing blades this doesnt matter. I find that with the right configuration I can even do welds at the mouth. I dont often put the work into the chamber.

[jsurgeson]

Cheers maddog

Yes I am fortunate enough to know a bit about electronics, and play with PIC micros as a bit of a hobby
so put it together as a project. It is based on the Analog Device AD595 type K thermocouple amplifier
and a PIC 16F690 microprocessor. The main reason was for heat treating my blades, due to inexperience other
than non magnetic, was incapable of telling the difference between 900 and 1050 deg C, and with N690 I
believe would make a difference in the result, could be wrong, either way as you say it is a quicker more
accurate way of training your eyes. If technology makes it easier why not?

As for shipping to SA, hmmm most people wont ship to SA due to high loss rate, if they do the cost makes it
prohibitive, even then the chances of it getting lost are high.

What industries would use them a lot? I have tried the refrigeration/aircon/gas appliance but none use them.

I am going to build a similar 3/4" burner and see how that operates in this forge, I am also going to build
another body with removable front and back.

Will post some images when done

Thanks to all for help and advice. Have a great weekend, I think you guys are celebrating a special day, if
so enjoy :P