Burners 101

[Mikey98118]

It is is to go back to the previous page a read the discussion that this is about.

[G-son]

Another thing I think is worth mentioning when talking about length vs. diameter (or jet size vs diameter): The inside diameter of the schedule 40 pipe is not the same as the diameter it is called. Supposedly they started out at the advertised size, but were later changed to thinner wall, and as the outside had to remain the same size for threads to fit the inside became larger.
Generally not an issue if you just paint by numbers and use the same kind of supplies, if you on the other hand use other kinds of pipe/tubing rated in actual size it might throw you off quite a bit.

An interesting side effect, more relevant to the diameter vs. length discussion, is that as the advertised vs actual diameter is different for different pipe sizes, the actual diameter vs. length ratio will differ too. For example, if you make two "8x length" burners, one ½" and one 1" you'll ofcourse have them 4" and 8" long. But as the ½" is really 0.622" diameter the actual length ratio is 4" / 0.622 = 6.43, while the 1" pipe is 1.049, making the ratio 8" / 1.049 = 7.63. 

[Mikey98118]

A pipe chart has been overdue on this thread

Viewers need to remember to double the wall thickness, in order to subtract the right amount from the outside diameter, when figuring out how large a gas jet orifice to use.

[Mikey98118]

Extruder nozzles

Bertie Bassett came up with the idea of using extruder nozzles for 3D printers as gas jet orifices on miniature burners; they can be purchased cheaply of eBay, and are already threaded; they are quite similar to gas jets for natural gas equipment. The important difference is that they come is capillary tube orifice diameters.

 

 

[Frosty]

On 8/28/2019 at 1:51 AM, Mikey98118 said:

A pipe chart has been overdue on this thread

Viewers need to remember to double the wall thickness, in order to subtract the right amount from the outside diameter, when figuring out how large a gas jet orifice to use.

OR just start using the radius of the pipe and skip the confusion. This is a major sticking point for people trying to line a gas forge. The volume of the fire chamber is THE determining number when planning the rest but folk keep thinking in Diameter so they have to double the thickness of blanket and hard refractory layers and subtract from the overall diameter. This is just asking to confuse things.

Just think in radius and the confusion goes away.  Seriously you have to calculate the area of the cylinder's cross section and that is Pi r sq. You have to calculate with pi anyway, just do it from the start. Hmmm?

Frosty The Lucky.

[Mikey98118]

Ceramic flame retention nozzle fittings

The hotter burners get the closer we come to needing refractory burner blocks, or multiple flame nozzles, which have a lot in common with ceramic burner blocks; piping gas into either kind of flame nozzle is pretty simple. However a refractory version of a flame retention nozzle, for the familiar single flame burner presents different problems, starting with a whole lot tougher ceramic (with is closed to being solved); it also requires a lot slicker metal to ceramic joint system, which is a long way from being solved. Any suggestions out there?

Metals and refractories have very different amounts of expansion when heated. On the plus side, a ceramic flame retention nozzle sits outside of a burner's mixing tube. And the mixing tube is cooled somewhat by the incoming cold air/gas mixture.

All that is needed for an upward facing burner is some compressed ceramic fiber between to flame nozzle and mixing tube to keep them centered and parallel, and a sliide-over ring on the mixing tube to keep the nozzle from sliding down, and changing the amount of over hang of the nozzle beyond the mixing tube.

For downward facing burners, things become more complicated.

[Mikey98118]

More about extruder nozzles

My extruder nozzles from eBay are due to arrive in a couple more days. Thanks are due to Bertie Bassett for his post on the subject. My interest in them is the same as the interest in MIG contact tips for larger burners: low cost, accessibility, and convenience. Although, it will probably be necessary to buy a thread gauge 

Why settle for this shape, instead of using capillary tube? friction loses don't just add in smaller diameters than are available from MIG tips; they multiply. Being a perfectionist, I don't mind dealing with such complications, but most people want practical answers  

On top of the fussiness encountered in dealing with tubing of capillary tube, there is the problem of cleaning tiny jet orifices of tar and wax buildup from propane fuel; its a lot harder in a tube shape than from a hole. As always, circumstances alters cases. 

[Mikey98118]

Ribbon burners and natural gas

All flames release heat, and are therefore exothermic. In an endothermic reaction heat is absorbed. Methane flames are rated in the same ballpark as propane, because fuel gas flames are measured just beyond the flame tip. However, methane has an endothermic reaction shortly after combustion as some of the byproducts of combustion recombine, creating water vapor. This is why natural gas (nearly pure methane) takes about one-third longer than any other fuel in the LPG family (ex. propane, and butane) to heat up a work piece.

This is still another reason to use fan-blown burners with natural gas, but it is also a very good reason to choose ribbon burners with natural gas, because the lower rate of atmosphere exchange is going to be more important with NG than with propane.

 

[Mikey98118]

.025" ???

.023" MIG contact tips (which have .031" orifices) are used for .023" welding wire; they have been around for decades. In recent years .025" MIG contact tips have become available; they are intended for the slightly larger .025" welding wire, and have .034"  orifices. The slightly larger tips are perfect for high speed 3/4" burners (ex. Mikey burners). Unfortunately, some sellers use the terms interchangeably, so before going out of your way to buy .025" MIdG tips, you need to make sure they really are. Below is an example of so called .025" tips on eBay that really aren't; they were listed as .025" tips on the title page of the as, and this explanation was given on the second page:

10 .023" Contact Tips, HTP/USAWELD P/N 1423-10. The tip on the right is the hex shaped OEM style tip, and the one on the left is the round tip we supply. You save 50% over the hex shaped tips. These .023"contact tips fit Snap-On™ 15 Series welding guns. These HTP .023" contact tips are equivalent to Snap-On™ p/n M3-T25. We are offering you 10 .023" contact tips for only $13.00!!! These tips fit .023", .024", and .025" wire.

 

[Mikey98118]

"I think of flame temperature as energy density.  Whereas BTU is energy volume."

 

so states AnotherFrankenburner, and I've never heard it put better. This fact is a lot more important then most people realize because forges can't hold energy; they only slow its loss. The smaller the forge the more efficient it is. The hotter the burner's flame the less needed to heat any given volume, and the slower fuel gas can be fed into it. So, larger burners are a losing proposition all the way around. Of course, hotter flames also raise internal surfaces to higher ranges of incandescence for increased radiant energy transfer before that expensive fuel heat is expended out of the exhaust vent.

 

[Mikey98118]

You can think of forge efficiency by picturing a water bucket with a leak; is the leak a small constant dripping, or does your bucket have a hole in it?

[Frosty]

On 9/3/2019 at 3:01 PM, Mikey98118 said:

does your bucket have a hole in it?

Yes, in the top. 

Frosty The Lucky.

[671jungle]

I also got some of them extruder nozzles. 

sizes range from .1mm-1mm excluding .7mm and .9mm. 

This is .1mm (.0039”). Orifice can barely be seen with naked eye or camera. 

Thanks for sharing the info.

[Mikey98118]

I believe that one of the canister mount propane torches has a gas orifice that small. This torch has a needle valve to adjust flow somewhat, but uses the great cylinder pressure (between 135 and 150 PSI) to force sufficient propane through its tiny orifice to create a fierce little brush flame.

[bertie_bassett]

hopefully those nozzles will be of use to you and other Mikey

im not sure if has been seen but i did post on my original thread a picture of the internals, the final orifice tube seems to be 1mm long and might be classified as a short tube orifice? i think the sharp edges should allow for a clean exit of the gas jet, thus providing a nice collimated jet rather than a spray.

that is just my thought though,i have no way of proving that.

im hoping that the smaller options will allow for a small but very hot hand torch, somthing for heating up small localised spots for brazing or just heating up bars for twisting. wont be as hot as an oxy rig but might get hot enough for most tasks?

ill have to let everyone else design and test things though, i dont know anywhere near enough to make  a decent start.

 

 

 

[G-son]

54 minutes ago, bertie_bassett said:

im hoping that the smaller options will allow for a small but very hot hand torch, somthing for heating up small localised spots for brazing or just heating up bars for twisting. wont be as hot as an oxy rig but might get hot enough for most tasks?

ill have to let everyone else design and test things though, i dont know anywhere near enough to make  a decent start.

You will indeed not get near the same temperature with a fuel/air flame as a fuel/oxygen flame, but often you don't really need the high temperature when using a hand held torch, rather the high energy output. A oxygen/acetylene flame can easily heat a small point to and far beyond the melting point of steel, which is excellent when you want to weld.
For bronze brazing or heat treating steel you often want the heat spread over a bit larger area (as fuel/air flames do, they can't be as focused), and you only need to heat the metal about half as hot as for welding, quite a bit less than that for silver brazing. So, you are fine with a "cooler" and wider flame most of the time, as long as the energy output is large enough to bring the metal up to a suitable temperature fast enough, and you don't have a problem with heat spreading to other near by areas you don't want hot. But sure, high temperatures are good, just not absolutely necessary most of the time.

I have a store bought hand held burner, using the disposable gas canisters, filled mostly with butane. Impressive for what it is, great for small silver brazing projects and has done a lot of general heating for various garage projects. Unfortunately it can just barley melt bronze brazing rod under ideal conditions, it's too small to keep up with heat escaping from the metal. The burner mixing tube is 5mm (for comparing it with other burners).

My first burner build has been a 18mm (a bit bigger than ½" pipe) linear burner with the smallest MIG tip, just because MIG tips are easy to get, and it's fed from the same kind of gas canister as above. Works great, but just as predicted the small canister just can't keep up for more than a couple of minutes at max power. That has been enough for projects like heat treating a home made jaw for a broken sheet metal shear so far, so not bad all things considered, but not really good either. (Getting bigger and better things for that one... eventually. Along with a forge.)

Now that I know I can build working burners, and that it's pretty fun doing it, I'm planning for a more sensibly sized hand held burner - something around 10mm, which will probably give around 4x the energy output of the store bought one (or so I'm guessing). A good increase, but not insanely large compared to what the gas can is supposed to be able to feed. Will probably still get a limited working time at full power before the can is too cold, but assuming it's something like 8 minutes or more (rather than 2) it's quite acceptable. Most projects for such a burner is done in a few minutes anyway, and the ones that take the most time are the ones that would benefit most from a bigger burner.

With these 3D printer nozzles there are sizes that should work for such small burners, so that makes that part of the build much simpler & cheaper. Too bad lining up all the parts gets harder instead when you build smaller things. Trying to get my hands on a small lathe to help that part of the build, would make much of it so much simpler and quicker (and cheaper). Anyway, the garage is becoming too cold now anyway, so most projects are on ice until spring. Time to search for a lathe, plan the build, and perhaps see other peoples builds using the nozzles. 

[Mikey98118]

Look back, way back, to around page 19 to see how to build the kind of torch you're thinking about.

There are some pretty neat canister-mount air/fuel torches that have come into the marketplace in the last few years; one of them is burns propane and propylene fuels. You can buy this torch for as little as $22 or more than $40...

[Mikey98118]

Sorry; I just checked, and the 1/4" canister-mount Mikey burner is on page 13.

Wow, where did the time go?

[bertie_bassett]

thanks for the help Mikey ill have to get a copy of your book so i can see a dimensioned drawing. planning on sticking with the larger propane bottles as have some hoses and a standard 'torch ' which i should be able to use the valve body/handle for control. 1/4" was about the size i was thinking.

G-son - i expect ill end up using the lathe and mill to machine such a small burner from solid, much easier to maintain concentricity. the nozzles should save on trying to drill tiny holes.

 

[Mikey98118]

That is a solid and truthful text filled with useful information; but it's dated. The smallest burner in that book is 1/2" size. You will find what information are available on my 3/8" and 1/4" burners in these pages; not in those.

[G-son]

3 hours ago, bertie_bassett said:

G-son - i expect ill end up using the lathe and mill to machine such a small burner from solid, much easier to maintain concentricity. the nozzles should save on trying to drill tiny holes.

It does indeed seem quicker and easier to make parts as you want them, rather than searching for parts and pieces that already has the more or less correct dimensions etc, at least when you have the machinery to do the job. Getting the pieces lined up straight "automatically" is a huge bonus.
You also get the option to make small changes in, say, mixing tube diameter, so you can tune the burner towards a neutral flame with the available nozzle sizes - rather than shortening or enlarging MIG tip openings with O/A welder tip cleaners, as can be done to adjust gas flow from the tips used in larger burners. Seems a bit more repeatable, if you were to build a number of identical burners - you make one prototype to find the dimensions to get it tuned right, and then just make identical copies that should work just like the first one. 

[Mikey98118]

Yes, if you have the machinery, machining a miniature burner is the way to go.

[Mikey98118]

Wasp-waist burners

Wasp-waist burners have been around for a long time. It is in discussing their designs that the term "venturi burner" became incorrectly to be applied to most naturally aspirated burner designs. To understand what such a burner is, just google "venturi."

So, are they good or bad as compared to recent homemade burner designs? The result will, as always, depend on how well they are built. Larger versions of venturi burners require metal spinning, as the most practical method of manufacture. 3D printing is making casting of smaller venturi burners practical again. Read more about these possibilities on the 3D casting. thread.

Anyone with a wood lathe can build the forms to use high alumina refractory to cold cast the forward half of a venturi, as part of the flame retention nozzle...

[G-son]

8 hours ago, Mikey98118 said:

So, are they good or bad as compared to recent homemade burner designs? The result will, as always, depend on how well they are built. 

No doubt. But what potential do they have? Are they worth messing with? There's plenty of proven designs for "straight tube" home built burners, is there so much room for improvement* over them so the extra work involved in waists is worth doing? 

*: Improvement = Changes like hotter, more efficient, or giving different flame characteristics more suitable for some specific jobs.

[Mikey98118]

The theoretical limits for air/LPG flames are all above 3600 F; until that temperature is reached there is plenty of room for improvement. On the other hand, yes there are very good burner designs already. So, which way someone answers your question depends on individual desires. I began this thread to supplement the how-to- do-it step by step knowledge my book was spreading, with more of the why to do it one way or another that would-be designers need.

Lots of people have stepped forward with their own insights, which are improving burner designs past my limits; they need a forum to speak from.