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Burners 101


Mikey98118

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On 10/8/2017 at 11:49 AM, Frosty said:

Don't worry Mike I'm not bashful. I haven't been saying much here because most of what I'm seeing is contrary to what I thought was right a while ago so I'm watching, thinking and reevaluating. I jump in when I actually have something to say.

The same thing has happened to me over the last three years on IFI. Considering all the cheeky guys who are coming up with excellent new burner and forge designs, it's just as well for both of us. :D After we had established our "Truths," it is disconcerting to have others turn over our apple carts and make us scramble madly to pick up the fruit scattered all over the pavement. I like it!

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  • 2 weeks later...
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Flame retention nozzles

I have occasionally seen flame retention nozzles work much better than they had any right to, according to everything I "knew; and this remains so to this day. When I started playing around with burners, tapered nozzles of one in twelve (1:12) amount of increase in diameter where the best around; but they didn't have enough draw to suit everyone.

Next came stepped nozzles, which had plenty of draw; too much for weaker burner designs.

Meanwhile, some people were quite content with threaded reducers as flame nozzles.

The latest nozzles have short tapers at their ends, and work just fine on SOME burners, and tolerably well on others; they are easily found on the Web.

A version of taper nozzle halfway between the classic 1:12  taper and the "horn rim" taper can be made with the help of a Bull pin as a form. I have seen several examples of such nozzles creating excellent flames on mediocre burners.

At present, the only conclusion I can reach is to let the nozzle fit the burner's mixture flow.

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Flame length changes in the forge

why should you worry about flame impingement from a 3" flame in a much larger forge? Flame length on a high speed 3/4" gas burner should end up about 3" long at 20 PSI, when running out in the shop or in the first few minutes in a forge, BUT, after the forge heats up to yellow incandescence, the flame will pale to a blue-white glow, and lengthen up to ten to twelve inches; and that is still only the visible effects. You can still count on superheated oxygen molecules to impact surfaces further on.

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Note that, will the flame is not obviously unstable, as in snuffing out easily, it has an exaggerated tendency to  run from lean to rich as its gas input is varied. Even a short funnel shape or pipe reducer fitting mounted at the burner's air opening should cancel that problem.

 

3” mini angle grinder:

 

What makes this 280-watt tool so surprisingly strong is that it runs from 220V, instead of the much weaker 110V circuits: https://www.ebay.com/itm/220V-Angle-Grinder-Polishing-Machine-Cutting-Machine-280W-3-Inch-Angle-Grinder/281462089757?epid=2135458581&hash=item418872a81d:g:z8AAAOSwAHZUNKXy

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"What makes this 280-watt tool so surprisingly strong is that it runs from 220V, instead of the much weaker 110V circuits:"

 

Electrical power is measured in watts: 

volts times amps equals watts

double the voltage at half the amps equals the same watts. 

Much of Europe runs on 220-240 volt wall power.

Doubtless that unit was manufactured for that market.

People who live where wall power is 120 volts would be well advised to stick to 120 volt angle grinders most of which are  rated at 400-700 watts.

Bob

 

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You have a valid point about how much more handy 110 power circuits are to find, except for in a modern garage. I'm not suggesting them as part of a general toolkit, but as a big help in building burners, forges, and shop stands. I will add to your objections that the disks can also become hard to find once you run out (nowhere near as hard as they were two years back though).

Furthermore, although my units came with accessories that allow them to become powerful right angle rotary tools, I made no mention of it, because these are only being sold as grinders, so those accessories may no longer be included. Finally, you could object that there are other 3" and even 2" angle grinders on the market...for $150 and up; I have both kinds. So getting back to a workable. affordable tool to help beginners build things like Mikey burners easily, more safely, and much more cheaply; they have free choice, and I welcome your objections. Let everything be made as clear as possible :)

My single Freshman circuit theory class was twenty years ago, but you seemed to have left out impedance, and how much torque it robs something like an electrical motor when you double it along with AC line voltage. I already have two of these tools; they are far stronger than their wattage would suggest; in fact, I consider their torque to reach the maximum SAFE limits for delicate handwork (like cutting rectangular air openings in a pipe). If you watch that video again, that should be made very clear by how fast that 3" disk makes castle cuts through the pipe.

I also wouldn't advice using gloves when running these tools; you need a firm grip.

 

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I mention them for a specific purpose; as to heating, I have never used one hard enough to cause any. Let the tool match the task.

It would be hard to beat the standard 4-1/2" angle grinder for general shop work, but I wouldn't even consider using one to cut out rectangular air openings on a 1/2"  or 3/8" burner. On the over hand, the average rotary tool is underpowered at the same task. Rotary tools who aren't underpowered become hazardous in use because they tend to jump out of the user's hands when their cutting disks jam.

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5 hours ago, ThomasPowers said:

HOWEVER heating due to resistance goes down with the higher voltage systems as they pull 1/2 as many amps and it's the amps that cause resistive heating!  Right RJS?

Not necessarily,  in a motor that can be reconfigured to run on 230 volts  the field windings that were connected in parallel are reconfigured in series so a 115 volt motor that drew 15 amps and was splitting it between the two parallel winding inside (7.5 amps each) when reconfigured for 230 volts now drives the same 7.5 amps through both windings which are now in series. 

W = V * A

W = V  * V / R

W = I * I * R

In English:

Watts  equals  current times voltage

Watts  equals Voltage squared divided  by resistance

Watts  equals  current squared times resistance

Heating would be caused by the inefficiency of the motor  (resistance in the motor windings, eddy currents in the laminations etc.)

As long as it doesn't reach overheating temperatures  minor inefficiencies in a hand tool are of no importance since they are almost always turned off, however  overheating can let the magic smoke leak out.

When a motor of a given horsepower is rewound  or reconfigured to run on 230 vs 115 the current will be halved but the reduced current will be going through twice as much length of wire.  

A perfect motor would have no resistive component to its impedance, no friction in its bearings, and would not heat up at all (good luck finding one of those.)

 

Bob

 

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  • 2 weeks later...

Not the end of the matter

A fuel rich flame in equals dragon's breath out. On the other hand, lots of such burners heat forges up just fine. This is one of those factors, that isn't necessarily a problem. But something that needs to be understood; not just excepted on the one hand, nor worried about on the other. Dragon's breath will produce more heat in your shop, and increase pollution in its air, increasing the need to blow out old air and replace it with new air. A CO monitor becomes critical. Also, all of that dragon's breath is wasted fuel.

If you do these things, dragon's breath is an irritation; not a game stopper. There comes a point when you FEEL like you have a crisis on your hands, as you try to tune a new burner; and that is likely an overreaction. Sometimes it is better to accept half a loaf and revisit the problem later.

 

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I am thinking about worm gear drive hose clamps, I guess that is what I think of when I think about hose clamps. The problem with people like my self that don't get in to the hands on work as much as someone that does it for a living is we forget there are going to be more than one kind of most things. 

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Well, you choose the only smart choice of clamp for creating a gas-tight seal on rubber hoses placed over barbed fittings. Most hose clamps on the market are meant to be fluid-tight; not gas -tight. You are right that people want to buy a high-quality clamp too. One good clamp from an auto part store beats a whole box of marginal clamps.

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Don't despair though, worm drive hose clamps are intended to hold against pressure generally greater than you're going to push through your burners. Even if the PSI is higher on a propane hose the area is acts on makes a huge difference so a hose clamp on a 3/8" barb will hold against many times the psi than one on a 2" radiator hose. 

A good hose clamp will be fine just do NOT over tighten it! They can be sprung, the worm bending the female slots in the band making for a lose clamp. All you need do is compress the rubber in the gas line into the barbs to make it gas tight. In an emergency (and I DO MEAN EMERGENCY ONLY!)  you can seal a hose on a barb with wire and a twist stick.

I've had to do this twice on river boats that weren't well enough maintained I chartered anything from them again, ever! Made the run back to the landing with the engine cover off and one person sitting watch on the fuel line holding the fire extinguisher the whole way. 

Frosty The Lucky.

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Input flames and forge atmosphere 

One 3/4” naturally aspirated burner, which is capable of making a neutral flame, will heat 350 cubic inches of open interior volume to welding temperature in a properly insulated forge (2” thick layer of ceramic fiber or the equivalent insulation in some other form). Add an additional 70 cubic inches for a burner capable of making a neutral flame in a single flame envelope (no secondary flame). Such a flame from a burner with an entrance port set up to control secondary air from being induced into the forge by its flame, and you can add another 35 cubic inches, for a total of 455 cubic inches. Addition of a sealing coating and heat reflective coating will raise forge temperature still further and allow lower fuel gas pressure to be used to gain yellow heat.

    When looking at the flame from a really hot burner—in a cold forge—It will look much as it does out in the open air, but within moments it will lengthen and become smoother in outline, as the forge starts to superheat; it will also lighten in hue to blue-white. There will be very little to no secondary flame within the forge, even while it is cold; lesser burners will make more complicated flame envelopes, but this is the ideal.

    You need to remember that there are at least two different flames going on within the average gas forge; the flame being input by the burner, and the possible output flame leaving the forge via the exhaust opening. When smiths discuss terms like dragon's breath it is the exhaust flame they are speaking of, which is a very different animal than the incoming flames from a burner. Not that both flames aren't equally important, but they need to be treated separately for clarity.

    So, if we are speaking about the burner flame, straight blue from a total primary combustion envelope is desirable, but many older burner designs have a white inner flame ahead of a blue secondary flame, followed by a darker larger and less substantial appearing tertiary  flame of  "secondary combustion"; but by that I refer to the combustion of byproducts of the primary combustion, which is something of a fiction in this case, for the white inner flame IS actually is the primary flame envelope in this case, and the blue flame is the secondary flame envelope here, so that what is normally considered as the secondary flame envelope, in this case, is actually the third envelope. How to resolve this; just don't go there. Buy or build a good enough burner to see no white in the flame, and then tune it up well enough to have very little secondary flame.

    The next question tends to be "how dark a blue?" Different fuels give off different hues, and lean flames are always darker blue than neutral flames in any given fuel. In fact, one burner could be run so lean that the primary flame turned purple from the amount of red that excess superheated oxygen could be included in it. On the other hand, any slightest tinge of green in the flame is an unmistakable sign that it is way too fuel rich; such a flame will be pumping out dangerous amounts of carbon monoxide. The simplest way to judge a neutral flame is that it’s blue is a lighter hue, and it has very little to no secondary flame; any darkening beyond that is from too much oxygen; it is no called a lean flame.

    You can also get thin yellow and red streaks in a perfectly tuned burner's flame, due to breakdown products of oxidation from some alloys of stainless steel, mild steel, or cast iron in a flame retention nozzle. Flame nozzles of #304 stainless can put on quite a show that way; it's harmless. #316 stainless make fewer streaks.

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18 minutes ago, Mikey98118 said:

How large a ribbon burner will heat 350 cubic inches of forge interior to yellow heat is going to need to be examined by someone who is into them. This is not a challenge, but an invitation. People will want the answer.

This is one thing I'm very interested in. At some point I hope to have some good input on the subject 

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