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Chamber Volumes VS. Burners

dot The various burner models I produce each have suggested applications, and some include suggested forge chamber volumes per burner, but they are, at best, only suggestions. I am often asked how big a chamber a given burner can heat, but I have to provide a rather vague answer. The variety of sizes, types, shapes, insulation types, designs, and quality of construction, found in various forges is all but limitless, and each factor has a profound impact on thermal efficiency, and how much space a given burner can effectively heat.

dot A few of the factors are type of refractory, is there an ITC-100 coating on the interior, is there a back pressure problem due to forge doors, the installation of the burner, the shape of the chamber (round is far better than rectangular, etc. If you have a very well designed and constructed forge, have the burner properly installed, have ITC-100 coating all interior surfaces, have the right amount of exhaust volume opening, etc., you will almost certainly improve upon the numbers I provide below.

dot By "effectively heat" I mean that the forge will easily achieve forge-welding temperature, or a melting furnace will produce a melt in a reasonable time, “reasonable” being relative. Forge-welding temperature is the benchmark that all forges and burners should be rated against. There are a number of commercially produced forges that do not meet this benchmark, and therefore should not be considered for blacksmithing use. I need to add that the chamber size needs to be reasonable for shop use. A tiny burner might be able to heat a 10 cubic inch chamber to forge welding temperature, but that tiny space is not a useful volume for most shop needs. I will go through the various burners listed on my "products" page, and provide one or more suggested uses, and I will suggest chamber volumes where appropriate, but again, chamber volumes are only rough suggestions, and your particular forge may work best with more or less volume than I suggest.

3/8" Rocket Hand Torch

dot This little burner is a wonderful preheating burner to preheat metals for arc welding. It will serve well for any hand torch needs where one of the little hardware store propane torches may be too "weak in the knees" to do the job asked of it. It is excellent for temper coloring decorative forged iron, and preheating for brass highlighting. For the guy/gal who wants nothing bigger than a bean can forge, this burner will allow him/her to build a significantly larger bean can forge than a store bought propane torch can heat.

dot A useful addition to all of these burners when using them as hand torches is this simple to make angle iron handle. The size of angle iron to use will be dictated to some degree by the size of the burner tube, but generally 1” x 1/8” equal leg angle will work well. This one is shown mounted on the 3/8” Rocket Hand Torch. Besides the usual metalwork applications, Ron Reil used this one to remove all the old asphalt tile from a house he was upgrading to sell in Boise, Idaho, just one of the countless uses these torches can be put to.

rocket-with handle

1/2” Shorty Burner

dot The Shorty Burner produces an intense flame that can heat a small forge chamber such as found in the Reil Freon Tank Mini-Forge. The chamber in the Mini-Forge is roughly 125 cubic inches in volume. Ron has forged 1” x 1” square stock bar in this little forge without any problems, but admittedly, such large iron in such a tiny forge is pushing its limits. This forge would be excellent for making small hand tools like chisels, but if the need arises it can handle more than that.

dot This burner, like the Rocket Hand Torch, works well for preheating, and for brazing of small parts. It will not produce the intense heat needed in a small area to use it like an oxy-acetylene torch. No straight propane torch can produce that kind of intense localized heat. For brazing small parts it works best to place the parts on a heat retentive surface, such as a charcoal block used for jewelry soldering, or a refractory block of some sort. If the parts are placed within a contained insulated chamber, like the Reil Mini-Forge, it can braze fairly sizable parts very easily. I don’t recommend this torch for temper coloring small section forge work because it heats too quickly and may push the temper color right into the gray range before you realize the work has been overheated. Once you become experienced in adjusting this torch, you can reduce the flame intensity to a safe level to do temper coloring however. All of these burners are highly controllable, so you can do work requiring only moderate heat volumes, as well as heavy work requiring an intense torch flame.

3/4” T-Rex Burner

dot This is the standard workhorse burner for use in a huge variety of applications. It will fit most commercially made forges, allowing you to replace the inefficient low temperature stock burners they come with. The rule of thumb for chamber volume is 350 cubic inches per burner, but your forge may allow more or less, depending on all the variables I listed at the top of this page. If you are converting a forge that uses two Reil or EZ burners to T-Rex Burners, you will probably be able to use one T-Rex Burner in place of two Reil or EZ Burners.

dot The T-Rex Burner can be used as a hand torch too, especially with the addition of an angle iron handle. It can do just about any kind of preheating you might require, and its amazing flame control makes even temper coloring easily within the job description of this burner. I say the least about this burner simply because it can do the most.

1” Forge & Foundry Burner

dot The 1” burner has 1.8 times the burner tube cross sectional area of the 3/4” T-Rex, so it can deliver almost double the BTUs to the work. Again, I don’t like to make statements as to just what size chamber a burner can effectively heat, but probably 600 cubic inches is reasonable, simply based on the BTU volume it can produce. Depending on all those factors at the top you may significantly exceed 600 c.i., or perhaps not achieve that large a volume.

dot This is a very good burner for foundry operations. The T-Rex is used in many home foundries, so this one will work even better. I won’t attempt to specify what size chamber or crucible any of these burner will support, simply due to the tremendous range of metal types and desired/realized melt times. If you don’t want to sit around for half a day waiting on a melt to complete when using a T-Rex in a given furnace system, this burner can greatly reduce your melt times and therefore save fuel.

dot One caution for foundry use that you should consider for all foundry applications is to mount the burner at a distance of 2 or 3 feet from the furnace, and place a fusible escape port in the bottom of the delivery pipe. That way if the crucible fails and dumps a load of molten metal in the bottom of your melting furnace, the liquid metal can flow down the pipe and out through the fusible port. A hole in the bottom of the pipe several inches in length, with a piece of paper covering it, is sufficient. It will hold in the cold burner gasses, even when a blow back occurs generally, but it will fail instantly when molten metal hits it, spilling it harmlessly out of the system...if you are working on a dry foundry safe surface, as you always should be. Remember, concrete explodes with molten metal lands on it. See more notes on Foundry use from Ron Reil.

1-1/4” Foundry & Kiln Burner

dot This is an awesome burner, which is a gross understatement. It require a large propane volume to supply it, or you will have freeze-up problems due to the fuel requirements this huge burner demands. However, for foundry use, if you are considering a less expensive 1” burner, your melt times will be so much longer by comparison that the money you save with the purchase of the 1” burner will probably be lost during your first melt. This is due to the much greater heat losses your system experiences over a prolonged melt time verses a much shorter one, especially so with the steadily increasing fuel prices. The faster you can get your metal up to pouring temperature, the less will be your thermal radiation heat loss, and the less fuel you will use.

dot I used to make some fairly specific chamber volume estimates for this burner. There is just too much variability due to the many factors that determine the heat retention/loss in a given furnace or forge chamber for me to do that any longer. This burner has 2.8 times the cross sectional area of the T-Rex, so it is putting out almost 3 times the gas volume and BTUs at a given pressure. Based on that alone you might infer that it can handle a chamber volume of close to 1000 cubic inches, which it may well do, or not. I will simply say that in a very well designed and constructed furnace or forge, the 1-1/4” burner may be able to efficiently heat a 1000 cubic inches or more, but you may experience considerably less in your particular system. If you are considering this burner, you should also consider putting the time and money into building a thermally efficient heating system to use it in. Yes, it will cost more initially to do it right, but with the large gas consumption these larger burners demand, you will save a lot of money in the long run. Cheap construction is false economy.

A Final Comment

dot I am not in the business of forge, or melting furnace, design. There are other sites that deal with that. A forge chamber and melting furnace chamber are not equal. The forge is not filled to 50%-75% of its volume the way a melting furnace usually is, so the empty volume of the melting furnace chamber that a given burner can support will be larger than the chamber volume for a forge. As you use larger burners you need larger annular space between the crucible and the furnace wall, or the back pressure will stifle the burner. You also need an increasing exhaust port opening diameter as the burner gets bigger. None of these specifics, or others, are questions I deal with. I simply make the finest propane burners obtainable anywhere, and leave it to the buyer to use the most thermally efficient design possible.


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Page Designed and Edited By: Paul Boulay
14 Mar 08
Copyright 2008