New Forge Build - First Fire

[Zacl79]

Hi all, long time lurker/reader of this forum. 

Some great information in here. It's been invaluable in my forge design/build. 

I have finally completed my forge build, dried it and fired it up to heat some steel. 

Inner forge dimensions 7"Wx16"Lx4.5"H - 500cub inches. Floor and roof have 3" kaowool (rigidized) and then 1/4" refractory cement. Sides are 2.5" insulation bricks. 

Have two 1" venturi burners, 0.03" mig tips. 12" burner tubes. Flare (Stainless) are set back into the roof by around 1". 

I dont known what pressure I'm running at, but it gets hot and fast.I had this up to around 1100C in about 4mins. And that was measuring with thermocouple at front of forge

Likely some tuning needed for efficiency and playing around with establishing a stable temp.

One question I do have is that I appreciate the shell will get hot (conduction and convection) as will the burner tubes, particularly when air flow is reduced. 

I have some gas pipe sealant (dope) connecting the lines at the top of the venturi. Aftert about 45mins operating I noticed the pipe dope was slightly browning and the ball valves and lines were hot to touch. Not burning hot, but noticeable. What do others use for pipe dope in areas where things may get hot?

I know this is a consequence of a vertical burner, if I have my time again I might got with some inclined burners. I do suspect I had my forge running waaaay to hot, but don't want anything that's unsafe in the longer forging sessions. 

Any thoughts?

 

 

 

 

[GeoffroyBelgium]

I let the specialist answer your questions and wish you wonderful forging work with this forge.

Geo

 

[George N. M.]

Welcome aboard from 7500' in SE Wyoming.  Glad to have you.

If you put you general location in your profile we can give better aswers to many questions which may be geography dependent.  This is a world wide forum and for all we know you could be in Lapland, Tasmania or Kansas.

Why do you not have a valve with a pressure dial in your supply line?  They are reasonably cheap, easily available, and are necessary for tuning your forge.  If you are not using propane and are hooked up to a domestic natural gas line that raises a number of different questions.  Natural gas is usually supplied at fairly low pressures (about 4 psi IIRC).

I'll let the propane forge gurus address any other issues.  However, I will take a guess that you might be operating at too low a pressure and the gas is not cooling the components as well as it could to prevent heat from traveling up the pipes from the flame area.  That is only a SWAG and the more knowledgable can confirm or deny it.

"By hammer and hand all arts do stand."

[Frosty]

Welcome aboard Zac, glad to have you. If you put your general location in the header you'll have a better chance of meeting up with members living within visiting distance. Who'd burner plans did you follow?

Your burners strike me as designed by someone on the internet who didn't understand how they actually work. There are instructions for a few different proven burner designs in the Iforge gas forge section. 

The common convention for burner size = mixing tube diameter. The basic ratios are based on the diameter of the narrowest part of the mixing tube, (Throat) where the intake connects to the mixing tube. The long time (hundreds of years) ratios are. mixing tube length = 8x throat diameter though it CAN go as high as 9x. The intake ports 2x the area of the tube though 2.5x is a good number.

The primary jet dia. for a 3/4" burner works well between 0.030" and 0.035", a 1" burner works well with a 0.045" jet. 

There are two basic types of propane burner, linear inducers where the combustion air intake is in line with the mixing tube, like yours. The other basic type is a Jet Ejector, commonly called an Ejector which has the combustion air ports at 90* to the mixing tube. Examples being Mikey's "Porter series of burners", The "Side Arm" burners and the "T" burner. 

A 0.030" jet in an ejector typically requires a choke to tune for a neutral flame. I tinkered the T burner to bur neutrally with a 0.035" jet and once tuned burn in a relatively flat curve from lowest to highest stable propane pressure.

A 1" burner should have a mixing tube 8" long, a linear intake bell of 1" x 3" and a 0.040" mig tip gas jet. 

A 1" T burner should have a 8" mixing tube and a 2" x 3.5" or 4" T and use a 0.045" to 0.050" mig tip jet. 

Making the tube longer than the ratio calls for by a LITTLE BIT won't hurt induction though it helps not a bit, as in ZERO improvement in performance. Making the tube more than 9x it's diameter begins to inhibit performance. 

If you replace the 12" tube on yours with a 8" tube and the mig tip with a 0.045" one the improvement in performance will be almost shocking.

There are step by step plans for the T burner in the forum gas burner section. You can increase or decrease the size by following the ratios and a bit of tuning.

Frosty The Lucky.

[George N. M.]

Zac, in case you didn't pick up on it, Frosty is one of our propane forge gurus.

[Irondragon Forge ClayWorks]

Welcome from the Ozark Mountains.

I don't think the pipe dope turning brown will be a problem, at least it isn't in our forge. Just to be safe when it is cold turn on the gas and check it for leaks with a little soapy water. If you do have to replace it, use some propane rated Teflon tape.

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

 

[Zacl79]

Thanks for the prompt replies already everyone. Much appreciated. 

Added my location into my profile, im waaaay down in the south pacific - New Zealand. Close to the forges of Middle Earth. 

George N MI run on a 9kg propane bottle with a high pressure regulator (up to 30psi). I did read somewhere, rightly or wrongly, the inline pressure gauges are a bit hit and miss. I do like the idea of figuring out what its all running at, even if its not hugely accurate - better than guessing i suppose!

Frosty I built off these here.

Artisan Supplies   Gas Forge Dual Large Burner Set with Hose and Regulator 130mj/hr

I couldn't justify spending up $600NZD for them. I got in contact with them and queried a few specs with them a while back and built off that. Based on my naivety, I though getting all the inlet/fuel lines another 4" (8" to 12") away from the hot area, things would be better at keeping things cooler. 

I do admit, I had some 0.03" tips lying around my shed and was too lazy/cheap to get something larger at the time I put my burners together. My rationale is that I could get everything working and fine tune things after. Ill pick up some 0.04" tips next week and swap em out. 

Getting parts like steel barrel nipples can be bloody tricky in NZ, I think I actually had to go to Australia to find some long barrel nipples. I'll see if i can track down some shorter 8" barrels. 

Irondragon Cool nice to hear. I'm still very cautious when firing up something really hot with propane, so do check all my joints with soapy water before each ignition. One day I'll get a little more comfortable working with hot things...but not too comfortable. 

Edited January 14 by Mod30
Remove @name tag & commercial link.

[Mikey98118]

Like Frosty, I don't think much of that particular burner design. However, your forge is hitting yellow heat with quite a large exhaust opening in the photo. Nor do I see signs of incomplete combustion in its exhaust gases. Furthermore, you neither mentioned painting a heat reflection coating on its interior, nor do the bricks appear to have any such coating. All things considered, I would call the obvious performance of your burners to look outstanding. There is an old saying along the line of "if it ain't broke don't fix it."

As to the pipe dope; I would replace it with gasket sealant or thread-locker that is rated up around five hundred degrees F, but then I'm kinda paranoid

[Frosty]

Another Kiwi, cool there are a few of you on the forum.

Another little Iforgeiron forum tip is to NOT use the @ tag on names, they foul up the operating system and the moderators or admins have to fix the problems. Don't be surprised if you get a note from them but don't worry they're all volunteers and the forum is quite a herd of cats to herd.

You did pretty well for how you built your burners, lots of guys do worse jobs following good directions. As a gage of performance, one well tuned 1" burner, especially with Amal mixers should be more burner than your forge really needs. That's not a criticism, just an evaluation, we can help you get them up to excellent.

When I build burners I avoid the long piece of pipe with gas hose hanging on it connected to the top. All that weight and leverage tends to knock jet alignment off center but that may not be an issue with Amal mixers, I've ever used one. I avoid high temps on my gas supply circuit by using copper tubing from the burner to the gas manifold. Copper tubing doesn't care about hot exhaust gasses or flame escaping from the burner mounts, copper won't fail below 2,000f. Of course you don't want to pre-heat propane that much it'd be igniting as soon as it left the gas jet.

Anyway, the copper tubing is flame proof and is not only light so as to not effect jet alignment it can help support the burners. The burners in my too large shop forge are not attached to the forge, they literally just stand on the top of the shell. I cut and welded 14ga steel flanges to the burner flares. Visualize large washers, maybe 2.5" - 3" wide. The copper tubing steadies the burners so they don't tip but allows them to move with heat expansion of the forge shell. I'll put a pic below.

Pressure gages aren't necessary, with a little practice you can hear when psi is right. IMHO the best purpose of gages is for repeatability of temperatures in the forge. For example you don't always need welding heat but have a forging temp that works best for you. etc. Looking at the gage while adjusting burner output is fast and easy compared to waiting to see if it's the right temp by letting the forge temp stabilize. 

Mike brings up a good point about putting a coat of refractory armor on the forge's interior surfaces, (Flame Face) especially if you plan on doing any forge welding. Forge welding fluxes almost all contain borax, molten borax is caustic in the extreme at welding temps and dissolves fire brick or Kaowool like boiling water on a sugar cube. Then need armor or you'll be replacing your liner frequently. Rigidizing the ceramic refractory blanket (Kaowool) is VERY important both to make it more durable and most importantly to mitigate the health hazards the airborne vitrified fibers are to your lungs. Think mesothelioma type hazard but worse, your body can't flush them out. The sharp little needles perforate the aviola in your lungs and don't dissolve. 

Anyway, rigidizing is a good start but the next step is giving your forge a high temperature, high alumina hard inner liner, Flame face. It does a couple highly valuable things for you. First (IMHO) is high temp armor protecting the very fragile ceramic blanket and pretty delicate soft insulating firebrick. Second is performance enhancement. Typically they are not good conductors of heat so the energy it absorbs from the flame isn't conducted to the insulating (secondary) liner very well. Soooo, the flame face layer just keeps getting hotter until it reaches the same temperature as the flame itself. The main way it can shed heat is via IR radiation back into the forge chamber. Sure it's radiating outwards into the insulating layers but the IR can't radiate very far. 

You don't need or want a thick layer of hard refractory but a little thicker on the floor is a good idea to provide added armor and a heat sink to transfer energy to your work. By a little thicker, it is 3/8" on my forge's floor and closer to 1/4" on the rest. 

Lastly and I think, the real performance booster is a good high alumina kiln wash. These go on like thick latex paint, they can be painted on with a brush, spritzed on with a spray bottle, etc.  I don't know if my preferred product, "Plistex" is available to you but you'll find a comparable product at ceramic/pottery supplies in the kiln supply listing. It's used in pottery kilns to prevent clays and glazes from bonding to the kiln furniture and in addition re-radiate heat back into the kiln. The last is what we're really after in a forge.

Kiln washes also fire coffee cup hard, providing a last layer of armor to your forge interior. Kiln washes are very high temp and stay hard while radiating IR back where you need it. 

Frosty The Lucky.

[Zacl79]

Hi all, just an update. 

I put an inline pressure gauge in this weekend and also swapped out the mig tips to 0.04". 

Still haven't sourced anything shorter than the 12" mixing tube, but happy to see how things go at the moment. 

I fired it up today, started at 5 psi to see how things went. Was pleased that it was again up to temperature quickly and seemed to be holding a more stable temp. Had it running steady at around 1100C for hour and a half. The outside of the forge and burning tubes were much cooler this time round. 

Managed to beat down a knife good enough. 

Next thing, i will aim to give the inside a wash as mentioned above. 

Thanks everyone for the advice thus far. 

 

[Frosty]