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I'm sure Frosty will have plenty more detail, but there are a few fairly obvious issues here:

  1. flame is lifting off the burner outlet, therefore the air gas mixture is moving at a higher velocity than the flame can burn.  Can be any of the following: too much gas pressure, too large a propane orifice, too much air entrained (mig tip not the right length), burner outlet too small (add flare, multiport burner, or flame retention nozzle)
  2. Don't see either a regulator or 1/4 turn propane safety valve in your gas train.  Without the former you can't adjust the pressure effectively, without the latter you can't shut off the gas in an emergency
  3. Alignment of orifice is critical for a stable, high quality flame.  I'd dump that one or use it for experimentation on improving the gas inlet mounting with a locking slide of some sort.
  4. At times you can get a flame to be more stable closer to the burner outlet after the forge interior heats up a bit.  Try candling at a lower pressure for a few minutes before turning it up to full bore.

Just suggestions from my experience with gas forges.  Remember to change only one thing at a time and check results.

Good luck and be safe.

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Agreed with all suggestions. I have an adjustable regulator and cut off at the tank. As I stated these burners are not tuned and I know one is misaligned. Pictures are merely to demonstrate the difference between flames. The brick pile is my test bed. Just want to share my failures in a visual way.. And, as always thanks your advise is valuable info in stuff I did not think about yet

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Frosty   

Not bad Maarten good enough to tune. First point is how you have your gas hose attached. The wall of a pipe T isn't thick enough for the threaded section to hold a brass fitting very securely so you can't have that much hose hanging from it and keep the jet aligned. This is another reason I like copper tubing for the final connection. I don't move the burners without taking the gas lines off either and sometimes find I've bumped the jet anyway. You can adjust alignment by GENTLY prying with a small screw driver or similar. Remember GENTLY.

The flame is too rich and the pressure looks to be too high in the pic. A too rich flame blows off the end of a burner easily so in this case it isn't necessarily an indication of too much pressure. Neither is a problem once you get the jet trimmed. Remember trim and test in small increments. Once you have the ratio right you'll find you have a surprising range of pressures it'll work at.

Frosty The Lucky.

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I will start trimming the tips tonight, more pictures to follow. I f I cannot get a stable flame with the misaligned one I will not use it as Latticino suggests (it is off center but still points straight into the mixing tube) . pressure is between 0.5 and 0.9 bar so around 7 to 12 psi. I will make sure to support the hose during testing.

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Gas pipes for saddle mounted linear burners

A 6" long schedule #80 1/8" pipe nipple, that is cut in half, is the most convenient form of burner gas pipe in the USA, because of the pipe thread left ready  for mounting pipe connections to. If you have British or European parts available, you would simply recalculate the inside and outside diameters needed on the gas pipe.

Also, by stopping the outside thread short of the end with the MIG tip, you gain more leeway in gas pipe diameters.

There are some European MIG tips available, with small threaded ends.

Finally,  silver braze alloys, common solders, or thread locker, can be used to seal threaded parts together, so pipe thread need not be used at all. What parts you use is only a matter of convenience.

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On 9/5/2017 at 11:31 AM, Latticino said:

'm sure Frosty will have plenty more detail, but there are a few fairly obvious issues here:

Thanks, Latticino,

Thosefour excellent points for anyone trying to tune any kind of gas burner to keep in mind.

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Glenn   

It was suggested that a post be copied to this thread for informational purposes. 

 

I'm planning on building a small gas forge with a single burner and would really appreciate some advice.  Ideally I'd like to use a propane torch as the burner but I'm struggling with working out which one will work best. Would something like this be suitable? 

torch.jpg

Like I said, advice really appreciated. 

======

Reply by Timgunn1962

Assuming from the link that you are in the UK, I would not advise using a torch unless you have (or need to buy) one anyway.

The Sievert stuff is quality, but it's worth checking whether the burner on that one is brass, steel or stainless steel.  There's a pretty good chance that brass will become a dribbly mess when trying to get useful forge temperatures.

You can buy a 1/2" long-Venturi Amal Atmospheric Injector (a commercial Venturi mixer) for around £50 delivered. Either the 354/12BLV (with a 60 jet) or 354/12PLV (with a 70 jet) will work. If you are mainly working hot, with welding the priority, the 60 jet is probably best. The 70 jet might be slightly better if precise temperature control down at Heat-Treating temperatures is important to you.

You'll also want a 6" (or longer) 1/2" pipe nipple for the burner. The injector incorporates a 1-in-12 tapered section and you don't usually need anything else on the end in a forge.  

You'll need a regulator, hose and fittings to get you into the 1/4" BSPF port in the injector. A gauge is optional and will fit in the other 1/4" port in the injector if you want to use one. The regulator should be a 0-30PSI (0-2 bar: adequate) or 0-60 PSI (0-4 bar: overkill).

Don't get a 0.5 bar-minimum (8 PSI) regulator, they are horrible to use in a forge.

The Amal burners turn down well and provide for exceptionally fine adjustment of the mixture/temperature. 

Fire bricks come in 2 main types: "Hard" and "Soft" or "insulating Fire Bricks". You'll almost certainly want IFBs. Hard bricks do not insulate to any useful degree and you'll probably need to step up to a 3/4" burner if you use them.

IFBs are not flux-resistant. Read the stickys for ways to protect them. 

Bricks are expensive to ship so we tend to get different ones over here to those in the US. My preferred IFBs for forges are marked LW23GRD. They don't seem to break up as badly with heat cycling as others I have used and, despite the 2300 degF rating, do not melt at temperatures I can readily obtain with the Amal burners. They also insulate better than anything else I have tried except the JM23s from Thermal Ceramics. I once used a JM23 to reduce the opening of a forge built from LW23GRD and the JM23 melted to a puddle. JM23s are my first choice for electric Heat-Treat ovens but I avoid them for forges.

I weld up a frame from 1" angle, rather than a sheet metal box.

I also take the burner in the side to reduce the chimney effect on the burner when the forge is shut down.

===========

Reply by Mikey98118

I recommended that burners be positioned vertical down at a tangent for the last eighteen years; this was because I liked the flame to impinge on high alumina kiln shelf floors, as the most durable position in the most energy efficient forge designs.

But circumstances alters cases. With better insulating and reflecting materials having recently become available at sane prices, it is time to turn away from the vertical down position.

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Thanks, Glenn.

In the past, thin heat rective coatings, painted on a semi-insulating high alumina refractory, was the most practical "thermal" armor," which people of modest means could find to act as a hot face over high priced ceramic fiber boards; these were use rated at only 2300 F. Now Morgan is making an equally high priced ceramic board; but one with has a higher use limit, and more mechanically sound. EDE, who lives in Texas, has has found a retail source of this board.

Morgan is also marketing a HIGHLY INSULATING, and much tougher semi- hard brick, which is use rated at 2600 F, for about the same price as the standard 2300 F bricks that we all know to fall apart under thermal cycling. Only their bricks don't; you can by them singly or is small quantities of eBay, with reasonable shipping prices, because they are very light.

Use rated 2600 F ceramic blanket remnants are starting to appear on places like eBay at reduced prices.

Veegum, bentonite clay, and bentone can all be used, in very small quantities, as a binder/plasticizer to turn zirconium silicate into very tough heat reflective coatings; they can also be used to turn zirconium silicate into a very high end refractory thermal armor; you can read more about that in recent pages on the Forges 101 thread.

But this is the burner thread, so getting back to the main point; these materials now make it practical to aim your burner in the most effective direction, without need to protect weak forge walls. 

 

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I have now seen two different people manage to make single envelope neutral HOT flames come out of burners I would not have believed capable of producing them. The first example was a modified Oliver upwind design But the second guy's burner was a true example of this burner type, with multiple round air intake holes. So I am definitely shifting my burner 'rules' from rule of thumb status to mere "it works for me" suggestions. :unsure:

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Also, in the last couple of months, photo after photo of burner flames have reinforced my impression that very minor changes to a burner can change a problem fame to a blue ribbon winner.

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Flame control

 Burner tuning, is the time when its every lack  is brought to light; that includes the lack of built-in variables:

(A) A flame retention nozzle can vary the flame widely; especially a stepped nozzle, by in effect, changing its length to width ratio (less so in tapered nozzles); this varies the speed of the air/gas mixture into the flame nozzle, while varying the mixture pressure. which helps to keep the flame from blowing right off the burner.

(B) A sliding gas assembly (gas jet in a gas tube) can also fine-tune a flame by varying how close the gas column is to the mixing tube entrance; and therefore how much air is induced into the burner, by any given gas pressure.

(C) A variable air choke is usually the best way to tune a burner's flame between fuel rich (reducing), and lean (oxidizing); on most burners, it is the only way to do so.

(D) Using a gas jet of the right orifice size for the mixing tube's inside diameter induces enough--but not too much--air into the mixing tube, to match up properly with incoming gas pressure. In most burner sizes changing out MIG contact tips for smaller or larger orifice sizes is sufficient to control this. The process can be further tweaked by mounting of capillary tubes in the tips of small burners and/or drilling and filing the holes of available MIG tips in larger burners.

In an inferior burner  (with slow mixture flow), all of these controls may be insufficient to tune the burner for a really hot flame. Conversely, in strong burners ( with fast mixture flow), every control you can get may be needed to keep the flame stable.

The smaller the burner the trickier fine flame control can be, and the more important it becomes to have as many variables built into the burner as possible.

So, the best nozzle design possible on a larger burner may end up being too much of a good thing; thus, changing to a tapered flame nozzle may end up being the best way to smooth out performance in a small burner, which has proven to be just a little too much of a good thing :rolleyes:

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