Planning a Propane forge, Have a rough plan.

[markknx]

Hey all,

I am planning up my first two forges one soil (not going to go into it here) and one propane. My plane on the propane forge is to start with a old propane tank (yes the valve has been pulled the tank rinsed twice with water and will be rinsed a could more times before cutting) I have ceramic wool on the way along with some super 3000( a pre-mixed mortar) from a friend that does refractory work for a steel mill. Should be good stuff. I will build a david Hammer type injector burner https://www.youtube.com/watch?v=VxzdqcPzXj8 I may turn my own orifice instead of using a mig tip.

Just to give more info I will be making the forge from a propane tank. with an Id about 12 " I want about 10" long so with a single burner I will have to put abut 2-1/2" of insulation inside to get the ID down to a max of 7"  (384 cubic In.) add a fire brick for the floor and I think 1 burner should be good. (fire brick should take up about 6o more inches).

Does this all seem about right so far?

Questions are should I use sodium silicate to glue the wool to the body of the forge?  Should I use a ridgidiser  On the wool or will coating it with the super 3000 mortar be good? How thick should I put the mortar on? min? max? If my friend brings 2" wool I would like to put 1/2-3/4 mortar on to bring me to my 7" target would that be to much? should it go on in layers?. I do know I will have to slowly dry it over a day or so with increasing heat.

Hope I was clear enough for you guys to see what my thinking is and if it is good. Thanks for any and all input on this matter.

Thanks, Mark

PS: No galvanized pipe will be used. This may help to I am a Ironworker by trade and have a hobby metal shop at home, Saw Mill/drill Lathe..... Forging steel is just the next logical Step in my love of working with steel. 

 

[Dodge]

This is what I do to line a round pipe (pronounced, re-purposed propane tank):

First layer is cut so as to have the ends butt snugly inside the pipe. The seam being oriented with what will be the bottom of the forge. Next, I lay in the floor; be it ceramic shelf, bricks, or cast refractory. Against the linear edge, I butt the second  layer snugly. If you get these layers cut accurately enough, no adhesive is needed to hold the wool in place. Your rigidizer will lock it in place from the inside  (Don't for get to cut your burner hole.) I then form a taper in the hole(s) and use this as my "nozzle(s)".

Hope this helps. Works for me

Scott

[markknx]

Dodge,

Yes this helps it will save me a trip to ceramic store for the sodium Silicate. Not sure if I'm getting 1" or 2" wool. I think 2" he said he thought it was 1-1/2. 1" 2" he is getting enough and it is free so I will make it work.

Thanks, Mark

[markknx]

Still waiting on ridgizer, so I can get the body of the forge built. I did get the burner built.

 

The burner with a shim between the tube and the flare. seemed a bit rich. so I removed it to let more air in.

this is the burner with everything set the same just the shim stock removed. A little lean I think but once in the burner the draw of air around the flare will be reduced.

It took about 5min. in open air to heat this spike to red heat. Not sure if all of this is good or bad. But I got fire and I got red metal that's a start.

Mark

Edited May 7, 2015 by markknx

[Frosty]

That's nice looking flame you have there. You want it a LITTLE rich, lean will cause the steel to form scale in the forge and that's not a good thing. You'll have better luck tuning the air fuel mixture at the air intake end than by allowing ANY air to leak in past the flare.

That final intake won't mix thoroughly so the flame will look good but it will be blowing 2,000f oxy rich air on your work scaling it quickly. It'll be hot but NOT the good kind of hot. You want to use the full length of the burner tube to mix the air fuel.

If you still have a choice 2 layers of 1" ceramic blanket works better than one of 2". The 1" rolls more smoothly with the fewer folds and wrinkles and the longer it'll last. It will also let you repair the refractory more easily without having to rip it all out to repair a small section.

Frosty the Lucky.

 

[timgunn1962]

If you want to run at variable temperature, adding a choke is the way to go. As Frosty says, it's much easier to control the mixture at the intake end.

If you want really fine control over the temperature/mixture, Heat-Treating blades for example, it's worth making the choke as progressively adjustable as you can. The commercial Venturi mixers usually have a screwed adjustment

[markknx]

Thanks for the input guys. It dawned on me later that I will lose that Oxy any way when I install the burner and pack ceramic blanket around it. so the shim can go back in. So would you say the top flame would work or richen it up more?

Frosty that is good new about the Blanket because 1" is what I got from my friend so that is perfect news. I did get most of the rest of the stuff for the body of the furnace today, now time is not there. the end holes are cut in the tank and ready I just have to make a base and tool rest. knock a hole in for the burner and line it. Maybe by next weekend I can give it a run.

timgunn, not sure I could add a screwed adjustable choke to this style. You got a plan? a slide choke would be real easy. the orifice is a mig tip(.025) so switching that is also an option. sliding the orifice back also seed to enrich the flame the flame. but not sure what is good bad better worst. Very new to this stuff.

Thanks again guys

Mark

[Charles R. Stevens]

I have seen a nice set up that is a fire brick tablle (brick set on 1" insolation) and an arched body (1/2 a pipe section) tho my gasser is a cylinder this arched forge seems to work great

[Frosty]

What's the burner tube diameter? A 0.025 jet is ballpark right for a 12" dia tube but be WAY too lean in a 3/4" tube.

The use of sodium silicate and colloidal silica in his refractory liners is the one issue Dave and I disagreed on. He designed his based on glass furnace and silicates are darned susceptible to hot caustics such as forge welding fluxes.

I really like his method of making his burner, it doesn't rely on special tools and maintains good alignment. Alignment of the jet and burner tube is as critical to proper function as jet size.

A properly built naturally aspirated burner needs no choke, the air fuel ratio curve is a nearly straight line. You just need to follow the ratios. From what I can see your build looks good so all you need are the ratios.

Frosty the [place witticism here]

[timgunn1962]

A nut or tapped lug on the slide-choke sleeve and a clearance-drilled lug on the burner tube with a long setscrew retained by a nyloc nut  would probably be the way I'd go for a progressive choke. I do have to confess to cheating by using a commercial gas mixer (and consider it about the best 35 pounds, around 55 bucks, I've spent in years) I did spend quite a lot of time experimenting with the jet sizes, but the clever bits were all worked out by someone much cleverer than me a long time ago.

I disagree with Frosty somewhat about the need for a choke. Nothing fundamental: more a result of different circumstances, I imagine.

He's right in that no choke should be needed to run. The A/F curve is also pretty close to linear.

For blacksmithing, which I assume is Frosty's thing, there should probably be no real need for a choke. Within quite wide limits, you can control forge temperature just on gas pressure. If you want to do different things at different flame temperatures, you can build forges optimized for each thing and fit burners optimized for the job in hand. The T-burners are cheap enough to make.

I suspect Frosty in Alaska has less of a space consideration than I do, living here on a small, densely-populated island, making the multiple-forge option viable for him.

From a bladesmithing stance, having a choke gives precise control over temperature/mixture for Heat Treating. You certainly can get the temperature control with a simpler burner, but this usually means controlling flame temperature on excess air (usually secondary air) and limits the atmosphere to the Oxidizing range. With a good Venturi burner, I can set a temperature and hold it indefinitely within a couple of degrees C (3 degF). The range I can run at is around 750 to 1500 degC, 1382 to 2732 degF, or perhaps a little wider.

As very much a beginner to smithing, I do not have the ability to judge temperature to any degree of accuracy by eye. Given that I am colorblind, it seems wise to assume I never will and not waste time trying to learn, so I use a thermocouple. When forging, being able to set the forge temperature to something that will not ruin the steel if I let my attention wander for a minute or two is very useful to me, but being able to go screaming hot if needed is also useful. I don't have the space for multiple forges, so need to ensure that the one I have will do everything I want. The choke makes it easy.

Basically, the jet size is tuned to give maximum temperature with the choke fully open. Closing down the choke then reduces temperature. Importantly, it is a progressive effect.

[Frosty]

Let me get this straight Tim. You assume I have how many forges? You shouldn't assume other's have to live under your limitations.

Your forge is a combination of commercial gas mixer and what else? You manually adjust the choke to control it to hold at +/- 3F temperature? +/- 3F!? Oh give me a break! For alloys that critical pros in AERO SPACE use professional heat treaters.

The more I read and reread your last post the more I realize I'm just playing silly buggers replying to you.

Frosty

 

[markknx]

Frosty, the burner is 3/4. I have .030 and .035 tips on hand I will try a .030 and see what I get. I am assuming I want to see a bit more orange in the flame with a darker blue. Is this correct? When you say follow  the ratios you do mean more or less in this case change the orifice to a size that provides a good flame and let the oxy take care of it's self?

The lining will have a 1/8" coat of refractory cement (super 3000) how will this handle flux?

timgunn, What I am not following from you is that all videos I have seen where a choke is used the choke is tuned and then left alone. Heat is then changed by either a needle valve or the regulator. Choking down for heat control seem like it would also give a carbonizing flame (rich) I am by no means a HVAC guy but this just seems like it would be the case. Also if you are using a thermocoupler to control heat why would you need the choke. the flame would be on or off no adjustment would be needed. Or am I misunderstanding your use of the thermocouple?

I took the pressure down to 1.5 psi and the flame looked pretty much the same just smaller, any thing below that and the flame is not steady. At 1.5 psi choking only made the flame sputter and die with little or no effect at lesser amounts of choke. the above photos were with 10-15 psi.

I really think this is a well designed burner that is keeping the flame consistent at a wide range of pressure. But I know little of these things.

Mark

 

 

[Frosty]

The ratios for a proper air fuel mix in the induction devices we use for naturally aspirated burners is based on the "throat" diameter. The throat is the narrowest cross section after the air intake. This is typically the beginning of the burner tube or where the pipe nipple screws into the T in a T or "Side Arm" or the bell in a linear like an EZ burner. The ratios are as follows. The length of the tube is 8-9 x the throat dia. The jet sets back 1/2 the throat diameter from the throat and the air intake cross sectional area is approx 2x the throat area. The jet setback is the starting point. In home made burners the easiest way to tune them is to move the jet in or out from the throat. The farther back the more air induced, the closer the less.

This applies to a home made burner be it a lineal or an ejector type induction device. They have zero to do with a gun burner of course. The output ratio to the forge volume follows reasonably closely unless you really push the output velocity.

A choke's only purpose is to adjust the air fuel ratio from oxidizing to neutral or slightly rich. If you build the burner properly it's unnecessary. Using a mig contact tip for the primary jet came about because I'm too lazy to keep removing the gas supply to drill a slightly larger hole. I had no idea they produce such a nice linear gas flow to the gas output. Mike Porter makes good use of the feature in his ejector burner. I just like them because they make rough tuning the ratio a matter of changing tips till the flame is close enough to fine tune.

I fine tune by trimming the mig tip. The farther from the throat the more intake air it will induce. If it's too lean use a large tip dia OR open it up with torch tip files. Files work better than drill bits.

How I mount my jets came about because I couldn't get 1/8" scd. 80 pipe without special ordering it so I adapted what I could find. If you can buy scd. 80 1/8" pipe USE IT instead of my Micky mouse!  It's ID is just right to tap for 1/4"-28 sae fine OR chase and tap for the metric mig tips. Buy the drill bits and taps where you get the mig tips. Chasing and tapping mig guns is NORMAL MAINTENANCE, they have the tools on the shelf.

Yes Mark your flame is shaped well so the mig tip is aligned properly with the tube. You've done a good job building your burner it just needs tuning. Try the 0.030" and see how the flame looks and sounds. Right now your burner sounds what I call "breathy" It sounds hissy, might even whistle. The 0.030" tip will make it roar. The 0.035" jet will make it roar uncomfortably loudly like it should.

The primary flame zone is the light blue opaque flame in the center of the burner/torch. It will tighten up into a shorter more conical shape and lose the feather with more fuel in the mix.

The secondary zone is the darker blue more transparent flame surrounding the primary which will become shorter and tighter to the primary as the ratio becomes closer to neutral. It is the air:fuel that is unburned immediately and is consumed as it mixes in the lower pressure higher temperature of the secondary zone and is NORMAL even with oxy fuel torches.

The "tertiary" or third zone is the fuel that is unburned because there isn't enough oxy induced in the burner through the air intakes of the burner itself. Your burner doesn't have a tertiary zone because it's too lean so the excess oxygen is consumed by forming scale on the steel in the forge or returning to the air you're breathing.

You want just a LITTLE bit of a tertiary flame. Just a little bit of orange in the dragon's breath exiting the forge doors is perfect. Be aware this means it's making MORE CO Carbon Monoxide and it's BAD for you. good ventilation is a must any time you're burning anything but when you're burning a Rich flame CO production is higher and more dangerous. Good ventilation is a mantra you should live using a forge of any kind. a propane forge especially. Adjusting for a little orange in the dragon's breath might be the place for a choke but like you said, once set you don't mess with the choke.

Lets' hope that is more clear than long winded. I've gone on so long here partly because I'd like you to know I actually KNOW what I'm talking about.

Frosty the . . .

[ThomasPowers]

Frosty I change the atmosphere in my propane forged based on what I am doing; how do you change the tuning on the fly with your system?

[Frosty]

I don't. A slightly reducing forge atmosphere suits everything I do. You do much more varied work than I do. How much do you adjust the atmosphere? All the way to oxidizing? If so for what?

I've found a neutral flame tends to allow spots in the chamber where outside air is drawn in and makes scale zones. Keeping it on the rich side eliminates scale. My original 1" T ran so rich it would reduce scale and rust in the forge. WAY too rich, my gums would start buzzing if I stood down wind from it for very long.

When I was tweaking the current T burner build I got a couple that ran lean, choking them was a PITA and usually involved aluminum foil or a little Kaowool in the air intakes.

Using the slide and set screw method for the jet holder pipe would be an easy fast way to tune on the fly though I'd prefer a vernier so using a swivel fitting for the supply line/hose and threaded pipe and luck nut for the holder would give much finer control.

[timgunn1962]

My apologies Frosty. I don't know how many forges you have, or need.

Markknx, you seem to be referring to heat and temperature as if they are the same thing. I'm afraid I do not find it easy to explain the difference, but there definitely is one. I think it's probably worth reading up on if you find it at all unclear.

Choking the burner does indeed cause the flame to go rich. It also causes the flame temperature to drop.

The flame temperature depends on 2 things: the amount of heat energy being released and the amount of "stuff" being heated by that heat energy.

It seems fairly easy to understand that there will be a fuel:air mixture at which all of the gas burns with all of the oxygen in the air, leaving no unburnt gas and no unburnt Oxygen. This ratio is called the stoichiometric ratio and is different for different fuel gases. Simplifying slightly, the stoichiometric ratio will also give the highest flame temperature. This is because all the heat energy goes into the smallest possible amount of "stuff". 

If we lean off the mixture from Stoichiometric, the energy release is still the same: all the gas has been burnt with the same amount of Oxygen as before, but there has been extra air drawn in and run through the burner. This extra air is intimately mixed with the gas and combustion air, so absorbs some of the heat energy released during combustion. With the same heat energy and more "stuff" to heat (the original "stuff" plus the extra air), the temperature rise will be lower and the flame will burn cooler.

Conversely, if we start at stoichiometric and add extra gas, the gas cannot contribute anything to the combustion process in the forge because there is no extra Oxygen for it to burn with. The extra gas therefore acts simply as extra "stuff", absorbing some of the heat energy and reducing the flame temperature.

Of course, once the hot gas gets out of the forge and finds the extra Oxygen, it burns with it. This is the "dragons breath". Because this second burn happens outside the forge, it is not helpful to us in terms of heat input to the workpiece.

There is another term that is useful when describing combustion, and it is "adiabatic". It describes a system where there is no energy exchange between the system and its surroundings. This is one of those concepts, like perfect insulation, that is unachievable in real-world situations, but helps in understanding what is going on.

There is a website,  http://elearning.cerfacs.fr/combustion/tools/adiabaticflametemperature/index.php, that has a tool for calculating the adiabatic flame temperatures of gases burning with air at different air:fuel ratios. Propane has the formula C3H8. The Equivalence Ratio is relative to the stoichiometric ratio for the particular gas being used; 1 is stoichiometric. .5 would be with only half the stoichiometric air supply. 2 would be with twice the stoichiometric air supply. I ran the numbers for Propane at a range of Air:Fuel ratios and charted the results. The graph was broadly in line with what I expected from having spent time working with gas burners, but had never seen numbers for. The top curve is temperature in Fahrenheit, the bottom one is in Centigrade.

I try to tune my burners to give about their highest flame temperature with the choke fully open. The actual temperature achieved in the real world will be something less than the graph: "my" curve will be lower, but its shape will be similar. By reducing the choke opening, it is then possible to follow the curve down to the left until the desired temperature is reached.

There's a guy on youtube who is much less of a geek than I am and his video probably explains things better than I can:

 

 

Another youtube video showing a quick-and-dirty HT forge in use heat-treating O1 steel. The blade was put in with the forge at 700 degC (1292 degF) and ramped up to 816 degC (1500.8 degF) solely on the air adjustment. Because of the ramp-up, the temperature was not as accurately set as would have been the case if it had been set at Austenitizing temperature before putting in the workpiece.

Gas pressure was at 20 PSI throughout. I'm sure many will be thinking "woah, that's crap: my forge welds at 5 PSI", but the gas jet in the video is only .020" (I have measured mig tips for .023" wire at .029"; over twice the area of the jet used in the video), the chamber volume is around 900 cu in, there is only  1" of insulation and the desire for even heating trumped the desire for economy.

 

 

The very fine control shown in the videos is only really needed for heat treatment. If you don't need it, great.

However, if having the ability to set a welding temperature when you want to weld, or a forging temperature (with the scaling-reduction that comes with the rich flame) when you want to forge seems like it might be useful to you, a simpler sliding choke will get the job done for very little extra effort over a chokeless burner build.

I've concentrated on Heat-treat because it's where the control comes into its own, but the basic principles apply to more conventional forging applications as well.

Using the same 1/2" burner as shown in the second video in another quick-and dirty forge, this one about 150 cu in and with 2" of insulation, the temperature range available at 20 PSI was from below 800 degC (1472 decF) to 1346 degC (2455 degF). Increasing the gas pressure above 20 PSI took the temperature over the 1400 degC (2550 degF) rating of the kaowool lining and I chickened out.

http://i667.photobucket.com/albums/vv31/timmgunn1962/25L Receiver Forge and Amal Burner/P3150901_zps5c60625a.jpg

http://i667.photobucket.com/albums/vv31/timmgunn1962/25L Receiver Forge and Amal Burner/P3150903_zps8c9f9f36.jpg

http://i667.photobucket.com/albums/vv31/timmgunn1962/25L Receiver Forge and Amal Burner/P3150906_zpsdbf72604.jpg

http://i667.photobucket.com/albums/vv31/timmgunn1962/25L Receiver Forge and Amal Burner/P3150908_zpsbf9fe7d6.jpg

http://i667.photobucket.com/albums/vv31/timmgunn1962/25L Receiver Forge and Amal Burner/P3150910_zps6ff4abbc.jpg

 

 

 

 

[markknx]

Thanks guys, that was a lot of info. now I have to let my brain cool down. All in all it seems I am to lean. So adding fuel would seem the answer. I get that a choke can be used to adjust the A/F ratio. But as far as temperature in the furnace wouldn't turning the regulator up or down to produce a larger or smaller flame take care of this? As I said before, the flame shape and color stayed pretty much the same at 2-20 psi. this leads me to believe that if I add more fuel I should still be able to keep a consistent flame over these ranges. But also as I have stated I am very new to all this so what do I know. But for sure I need to change the ratio to richer.

Frost yes the furnace will go outside should have good ventilation. But thanks for the tip.I will look for these feature in the flame as I tune. tip files are a good idea. my tip holder does slide so I have that also I can tune with.

Keep in mind I am so new to this NASA could build my furnace and I would not get perfect work. So as long as I get the flame, it is hot enough, does not oxidize the steel I will be in good shape to start. from there I am sure the fine tuning will come with time. One more thing to think about I get a full range of weather here in that the air can be so dry you can create an electrical storm pulling a blanket from a sheet, or so humid your close feel wet as soon as you leave the house. A 20%-30% change can happen in hours. so being micro tuned may be an issue. : >).

I will report back after I make some adjustments.

Thanks again guys for your time and info.

Mark  

 

[ThomasPowers]

I once ran my forge all the way up to gosh almighty that's oxidizing! and used it to create an extremely heavy scale layer on a dragon door knocker I was forging from some 1" sq stock.  When I chipped it off it left the dragon's hide rough and pebbly---what I was hoping for.  But in general when I'm heating 1.5" mild sq stock I go for a "perfect burn" to get the most heat and when I'm doing blades I go for a reducing atmosphere. And then there is always adjustment for wind conditions. I tend to not close up the shop any when using the gasser indoors until the wind starts blowing tools off the anvils. (and sometimes not even then...)

[Frosty]

You're doing fine Mark, from the looks of it you've got the important parts right it just needs tuning.

These things aren't complicated they just require a moderate level of precision when building. It was MY bad engaging in debate with a cut and paste . . . "expert".

The NASA guy's version of a propane forge is more complicated than I think is necessary but Mr. Gunter's (I THINK it's Robb's) Sandia regenerative forge is really easy on fuel. I would like to get hold of some shuttle tiles to play with though. Fire brick doesn't stand up real well to thermal cycling and it's hard to find a sharper cold, heat, chill cycle than reentry from orbit.

The wide humidity change will effect the air fuel ratio, it'll run leaner when it's drier, there's more oxy / cu/ft. You might need the choke to keep the burn right after all.

Frosty

 

Edited May 9, 2015 by Frosty

[Frosty]

I once ran my forge all the way up to gosh almighty that's oxidizing! and used it to create an extremely heavy scale layer on a dragon door knocker I was forging from some 1" sq stock.  When I chipped it off it left the dragon's hide rough and pebbly---what I was hoping for.  But in general when I'm heating 1.5" mild sq stock I go for a "perfect burn" to get the most heat and when I'm doing blades I go for a reducing atmosphere. And then there is always adjustment for wind conditions. I tend to not close up the shop any when using the gasser indoors until the wind starts blowing tools off the anvils. (and sometimes not even then...)

​Oooh, I never thought of scale for texturing and I've been messing with 2D heads. Hmmmmm.

I'd run more neutral but the shape of my forge invites room air to be drawn in at the corners so it has oxidizing zones unless it runs a little rich. I have wind issues too.

There's a lot to be said for gun burners eh?

Frosty

[markknx]

Well guy it has taken me a while to get to this point. the body is built the wool is in and the refractory cement is on. the lining took a few days so things could dry good. However I jumped the gun on firing up the burner. (I though the refractory cement was dry but I was wrong) the refractory bubbled from steam I think. it did not bubble off the wool just split the cement into two layers. so I am giving it more dry time with a heater on it.

Can I recoat this once I get it all dry and test it out?

Mark

[Frosty]

I don't think I've ever seen refractory blister like that. Did you mix some secret mojo with it? How hot did you get it? If you got it hot enough it's as dry as it's going to get. If you ruined it such is the price of impatience. Remember the lesson when you're forging. Getting ahead of yourself has ruined more projects than any other single cause I know of.

If you have to rebuild it, forget the fancy things you thought of to "improve" proven forge liners and just stick with what works. Seriously, glopping mud no matter how good a refractory over ceramic blanket is problematical just getting it to dry without shrink checking and falling apart.

I don't recall what you used, refractory CEMENT? Cement is NOT a refractory LINER, they are two entirely different things. One is to cement bricks together in a furnace or kiln, the other is to withstand high temperatures as a fire contact surface. They are NOT interchangeable.

Frosty The Lucky.

Edited May 19, 2015 by Frosty

[markknx]

Frosty,

I used Vesuvius super #3000 Monolithic Refractory. I got it from a friend that does refractory work in a steel mill. Very true about the impatience ruining projects.

The one in the white bucket.

Mark

[markknx]

Well it burns! I need to tune it just a bit I think. seems a little rich. the flame coming out of the doors is mostly orange. If I recall Frosty said it should be blue with a little orange. Cooling down now I will clean up the burner hole a little seemed I was catching it a bit with the flame once I do that I will see what I have. If not good then, I will try sliding the orifice back a little.

Here is a vid.https://www.youtube.com/watch?v=AZrmVm6m0zU

Mark

[Frosty]

I don't know how I got the idea you were using refractory cement, maybe one of us misspoke. Ragardless that stuff should do fine. Are there instruction on the bucket for curing? It seems the Vesuvious site lists the stuff as mortar but then goes on to say it's monolithic refractory. So, I don't know enough about the stuff.

Looks to be burning nicely to me, maybe a LITTLE richer than necessary but not out of line. Just make sure you have good ventilation and I think it's ready to put to work. I'd be using it. Maybe abusing it a little to see how tough it is. The product data sheet says it's used to patch damage too so what the hey, why not.

Frosty The Lucky.