Mikey98118

Burners 101

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A CO detector is a very good idea; it can warn you about a lack of clean air in your shop, but just as important as knowing about a problem is managing it.

Don't forget to allow some air to enter between the burner pipe and the burner portal; whether the portal is a larger pipe than the burner, or just a hole through firebrick. I have noticed lots of guys stuffing ceramic fiber into the gap between the burner and the portal opening; that is acceptable way to prevent too much secondary air entertainment, only with burners that achieve complete combustion in a single flame envelope. The bulk of burners (even those that make neutral flames) have a secondary flame envelope, which requires additional air to burn.

Caution: The air that your burner induces will mostly burn in the primary flame, leaving insufficient oxygen left over to completely burn any secondary flame. Without a secondary air source to completely combust fuel gasses, carbon monoxide will form as part of the exhaust. 

Your burner will not find air within the forge for more than a few seconds unless it is provided through the burner portal's opening, by being induced by the burner's flame. It is desirable to control the introduction of excessive secondary air, for burner efficiency, but it is utterly necessary to provide sufficient secondary air to completely burn the fuel, for safety!

If your burner can't burn its fuel completely with only the air provided through its mixing tube, THEN DO NOT STUFF CERAMIC FIBER AROUND THE BURNER. A movable washer, which can provide a variable amount of secondary air for a burner that is mounted in the forge will work fine, and can be used safely; ceramic fiber cannot in this case! 

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  Nothing stops use from using some fiber part way around the burner to reducer excess secondary air induction, but don't over do it. Watch the flame as you add fiber, to be sure you don't go too far.

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I have a two burner forge, and two welded nipples that the burner tube goes through. Th nipples are welder solid all the way around. There are three set screws that hold the tubes in place. Its a snug fit. Should I maybe drill a small hole beside the nipple to allow secondary air to enter the forge. Trying to grasp what you mean.

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If the fit between the the burner and the portal is very close, then yes; one or more small holes in the portal tube could improve the burner's flame; it all depends on how much secondary air the burner is getting versus how much additional air it needs. If you want a better answer than this, posting a flame photo of the of the burner in action would help.

Generally how much secondary air a burner requires depends strictly on how large its secondary flame is. So how do we know how much and how large to go for when drilling the holes? Start with small holes, because small can always be enlarged. How many is determined one hole at a time; running the burner after every new hole is added.

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The burner we used is a GACO MR750 kiln burner. The kilns were developed to use secondary air in a 4 burner kiln. In the forge we used an over sized burner tube to get the secondary air. Works like a charm. Since this picture we had to move the "wasp waist burner" a little further out to get more secondary air and the flame nozzle back into the refractory more.

100_1852.thumb.JPG.e2c45a68814a7619edd5ccb647300b86.JPG

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Aligning burner parts

Most burner designs are considered easier to make with threaded plumbing parts; that can be true, or far from it; depending on those parts. Cheap imported fittings are becoming the rule as steel water pipe is marginalized by plastic. Cheap fittings are often made from marred castings, which don't thread properly, producing misaligned threading in the finish part; such parts make misaligned burners, which cannot be properly tuned, and thus produce poor flames. Here are some answers to this problem:

(! ) Avoid buying threaded fittings from large generic hardware stores. They don't have a good selection of fittings, and tend to use cheap imported stock. Look for regular plumbing supply stores or HVAC supply stores, instead.

(2) Hand screw fittings and pipe together and inspect them before purchase; crooked fittings are easily spotted this way.

(3) If you must buy your fittings online consider using stainless steel instead of cast iron; stainless parts are likely to be much higher quality.

(4) The surest answer to a problem, in the end, is to avoid it in the beginning. Every threaded pipe fitting has a much higher quality butt-weld equivalent. Pipe, or better yet, steel tubing can be used in the next smaller size to the fitting's opening, slid into positions (after a little power  sanding or filing if it is oversize), and held in place with screws.

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So we see that the KISS principle normally applies, unless...

"Circumstances alters cases" (trouble getting acceptable parts), then it is modified by...

"Just don't go there."

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Valves: Facts and fiction.

There is a persistent idea that has circulated for years that when gas rated ball valves are used in a partially open position, they will quickly wear out; that could be true about ball valves used on water mains; it could even be true about ball valves used with full cylinder pressure. But partially opening a ball valve on a regulated system at 15 to thirty PSI? Well, perhaps; how many decades do you plan to wait for it to happen?

On the other hand, using a ball valve to regulate gas flow can get awkward; trying to fine tune a burner that way? Ball valves are used to open and close flow; they can be used to regulate it, but not with precision. Needle valves are designed to regulate flow; good ones can also completely stop flow, but are not designed for that, and will slowly start to leak flow even when fully closed, as their seats wear.

I have used ball valves to regulate flow, to a limited extent, in a burner idler system. Employing a ball valve, instead of a needle valve allowed the idler assembly to be much more compact. Who wants a big idler assembly on a mini-forge? Nevertheless, it was a trade off between fine control and compact size. It is true that the assembly cost was less, and it was much simpler to find parts for and build...

But what is saved by employing a ball valve to regulate gas flow to a burner? For a few dollars difference in the price between a ball valve and a needle valve are we going to sacrifice the fine control needed for proper tuning?

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21 hours ago, Mikey98118 said:

But partially opening a ball valve on a regulated system at 15 to thirty PSI? Well, perhaps; how many decades do you plan to wait for it to happen

Actually it can happen a lot faster than you expect.  If the ball valve is being used for metering it may have to be closed so far that the gas velocity in proximity to the ball can get very high.  Since the propane vapor coming off the tank is not in perfect gaseous state, some microscopic liquid droplets can get passed with the vapor.  This can lead to what is called "wire-drawing" in the control valve world.  The abrasion to the valve seat and ball from this high velocity liquid can ruin the isolation capability of the valve.  Admittedly it is less a problem for ball valves used on propane than it is for, say, gate valves used for steam, but as you say, why chance it.

The other down side to using a ball valve for metering is that the adjustment is quite difficult, as you clearly noted.  You can close the valve pretty far without making a major change in the downstream pressure.  That is where true metering valves, like needle valves and pressure regulators show their real colors.  If you do decide to use a ball valve for metering, attempt to gain some "valve authority" by reducing the valve size below that of the line feeding the forge.

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After Frosty's talk of lower velocity, my experiments headed a little different direction.  

I only had a minute to play with it when finished so this was a quick picture before any tuning.  Forgive the back drop again.

356802125_flamever6.thumb.jpg.0799e02edc14154df95ca8199dd64796.jpg

I will post more images when I have time to experiment with tubes/tips/pressures and tune it.

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Latticino,

I enjoyed your post a lot; it contributed greatly to the discussion. I would only like to refine my remarks by saying that, so far, I have never run propane through any hose without installing a regulator at the cylinder first; it is possible to do so legally as nearly all fuel hoses are rated to about 250 PSI, bought just because we can do a thing legally, doesn't mean it's wise. So both needle and ball valves are only dealing with 30 PSI and down; typically at 12 to 15 PSI. The lower the line pressure the lower the gas velocity through the valve. Also, the lower the line pressure the farther a ball valve can be opened with the same effect.

You are totally right on the money about ice (or liquid?) particles in the propane, as it leaves the cylinder, doing more to deteriorate a valve. Around 2006 I went round and round with some guys who objected to my descibing LPG fuels as "vapors," rather than true gases; the argument started over the same problem you pointed out. Having had a big interest in small burners "which need small gas orifices) from the beginning, ice and liquid particles in propane systems jumped onto my radar early. The safety regulations in most communities that require propane cylinders to be kept outdoors, and OSHA regulations encourage businesses to keep flammable gases at least twenty feet away from ignition sources. So, I started using twin torch hose that come in 20 ft. lengths, decades before ever building a forge. Such long hoses tend to warm up the gas enough to get rid of ice or liquid particles from the cylinder, whether they are stretched out flat, or coiled in a warm shop.

Again, I agree with your points. And while "circumstances alters cases," it does the reader no good if we don't mention them:)

Thank you for jogging my memory, and please keep bringing up these very important points.

This doesn't argue against anything you brought up; I hope it simple adds to it :)

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4 hours ago, AnotherCurtis said:

only had a minute to play with it when finished so this was a quick picture before any tuning.

Congratulations; it is as perfect as any are/fuel flame I ever made. What has been added to make that so? Look first at the flame retention nozzle; it has gone from red-orange to bright orange. Nozzles don't get more incandescent on air/propane. On air/propylene the nozzle would be radiating lemon yellow out in the open air.

In fact, you know have to move up to thick walled nozzles, or they will probably collapse in the equipment. How thick? I use 1/8" to 5/32" on small burners, and up to 1/4" thick on large burners.

All the scrap yards in Seattle, which I used to buy stainless steel tube from, are gone. So, how to buy thick wall stainless steel without breaking the bank? Look up Onlinemetals.com. Select stainless steel; now select pipe. Yea brothers and sisters, SS ppipe is the low cost answer; and this ain't no snake oil:D

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Thanks Mikey.  

Nothing was added.  This is a different burner then the last set of flames.  I have been experimenting with different shapes to see what they did to air induction and mix.  This particular burner was trying to entrain as much air as possible with lower velocities.  As you see in the image, the velocity is still pretty high but it induces enough air that I have to close the choke most of the way.  Frosty explained the why's on the wasp waist burner and so I started to tinker with their geometry.  

I haven't had much time to tinker with it but it induces enough air with the 0.023 mig tip that I will be putting an 0.030 to see how that does.  With the 0.023 it is still pretty fast at higher pressures but it seems happy with lower pressures. 

It induces enough air that it is picky about it's pressure/choke setting but it also seems to be adjustable to a large range.  I have another end goal to produce a small output burner for a two brick forge.

I added an airfoil shape to the ribs which hold up the accelerator block thinking more spin and at lower pressures it is noticeable in the flame.  I think it adds a roar to the flame which may be instability but it seems fairly stable unless given too little choke.   It only has two narrow ribs which put it more in the linear category but it has a sliding choke like a Mikey.

Mostly I am just having fun playing with burners.  

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Latticino,

I enjoyed your post a lot; it contributed greatly to the discussion. I would only like to refine my remarks by saying that, so far I have never run propane through any hose without installing a regulator at the cylinder, so that both needle and ball valves are only dealing with 30 PSI and down; typically at 12 to 15 PSI So, effects from; the lower the line pressure the lower the gas velocity through the valve.

You are totally right on the money about ice particles in the propane, as it leaves the cylinder. Around 2006 I went round and round with some guys who objected to my calling LPG vapors, rather than true gases; it was about the same problem you pointed out. Having had a big interest in small burners, which need small gas orifices) from the beginning, ice and liquid particles in propane systems jumped onto my radar early. The safety regulations in most communities that require propane cylinders to be kept outdoor, and the

21 minutes ago, AnotherCurtis said:

I added an airfoil shape to the ribs which hold up the accelerator block thinking more spin and at lower pressures it is noticeable in the flame.  I think it adds a roar to the flame which may be instability but it seems fairly stable unless given too little choke.

When I first constructed these burners for the book, I held back a little bit on the design; as you will recall. Now that you are going for broke on this design, you might consider using a larger diameter on their flame retention nozzles; if it works, it might prove more satisfactory than using the choke; just a thought.

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I will try that.  Are you speaking of a stepped type with a larger step?  

I would like any thought, suggestion, criticism you are willing to offer.  I have plenty of burner for my forges, I did a few burners ago.  At this point I am just having fun changing things up to see what happens.  I try to educate myself and guess what will happen but being wrong is sometimes just as good as being right.

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1 hour ago, AnotherCurtis said:

will try that.  Are you speaking of a stepped type with a larger step?

Yup.

As to educating your self; that is the highest form of education :D

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With a larger step in a stepped nozzle, what is the goal?  Is it flame retention exclusively?  Better mixing?

I seem to recall you stating that stepped nozzles required higher velocities.  I can't seem to find where I read it though.  Is this true?  What happens at slower velocities with a stepped nozzle which makes them incompatible?  I have been talking to Frosty and he brought up cavitation possibly being caused by a step at higher velocities but I haven't talked to him enough to wrap my head around it all.  

I remember reading on Ron Reil's website about the nanomongo burner which is stated as your design, that it had a 1:12 tapered nozzle but that it had an 1/8 inch step which was critical to the design as the burner was built with thin wall copper.  It's been up for a long time but do you recall what happened without a step?  Any idea on the why's?  Did you ultimately go with the straight stepped nozzle because it was better in some way or is it just easier to build?

The volume increase should cause the pressure to go up and the velocity down but they say that doesn't quite hold true with a venturi due to turbulence and with a large step, it seems like a violent change in volume.

I see that with a tapered nozzle, depending on velocity, the flame will settle along the length of the taper where it needs to.  With a straight stepped nozzle, I don't quite understand what is happening or why controlling the amount of over hang changes things.  Is this due to drag/turbulence?  

Admittedly, I have more experience with the tapered nozzle.  I will be building stepped nozzles of different IDs to see if I can wrap my head around what is happening.

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40 minutes ago, AnotherCurtis said:

The volume increase should cause the pressure to go up and the velocity down

Nope, the same volume of FAM filling a larger volume of space LOWERS pressure and velocity.

Latticino: I always look forward to your input on this stuff being a pro. Propane is weird stuff I finally got tired of trying to explain why it behaves more like a mist than a proper gas. It not only does strange things to valve seats not intended to handle the stuff, given time that is, but it makes it hard to get to mix with air. Another property that can add to it's mechanical erosion talents is the waxy stuff that often comes with or forms in the gas. Propane sold as fuel isn't a single gas it's a  mix of closely similar gasses. 

Bear in mind most of my propane learning is hear say. I ask questions of the HVAC guys up the road, the guys at Suburban Propane and the guys at Distribution International, used to be E.J. Bartell know fire of all kinds and have run into propane issues of all kinds. They go to school about propane, I just take advantage of their patience and ask questions.

Curtis: I believe Mike is as happy to have another burner guy aboard the guru train as I am. You're getting into this just like we did, for want of a hotter fire and the joy of tinkering. It's a good thing. :)

Frosty The Lucky.

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Wikipedia paraphrase: In the venturi, the velocity must increase because of the constriction which increases it's kinetic energy but this is balanced by a drop in pressure. The Bernoulli equation is invertible and pressure should go up when velocity goes down but expansion causes turbulence to jam up the works.  

We see lower pressure and lower velocity because this turbulence robs energy?  In our case, that a lower pressure zone is good as the higher pressure stream is happy to move to this lower pressure zone and get out of the way of new incoming FAM which allows for higher induction?  Which can also slow the FAM stream enough to prevent lifting.  That is making sense now.

The more I learn, the more I realize the wisdom of the people before us.  In this case, I am referring to the wasp waist burner but it tends to hold true in many areas.  The more I realize this, the more I realize I am just reinventing the wheel. 

Thank you for the kind words.  Guru is probably a bit generous but maybe someday.  It's easy to learn quickly when talking to people who know more.  There are a lot of those people around here.  

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As to the joy of tinkering, this is playing with fire but involves math, science and trial and error.  I can't help but enjoy it.  Years ago this process involved a stick, a campfire and constant scolding's from my parents.  

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Keeping your eye on the ball

The first few months after making my first stepped flame retention nozzle I tried some pretty far out ideas. One of them was dubbed the Piggyback burner; it was basically just a longer tube mounted outside of the burner nozzle that allowed the flame to induce more air into itself, allowing the gas pressure to be turned up higher. The piggy backed nozzle resulted in some very large flames coming from very small burners, and the ability run a variety of nozzle sizes, and therefore flame sizes, from a single burner body. The flames were of very high quality, so what's not to love, right?

You've head the expression "there ain't no free lunch?" The problem was that, when the gas pressure was turned up past a certain limit, the flame would suddenly snuff out--without warning. Talk about instability! The responsibilities, and the pitfalls in piggybacked flame retention nozzles remain; no way I'm going down that rabbit hole.

Twenty years ago the latest thing in flame retention nozzles were tapered stainless steel tubes with threaded screws, which allowed them to slide back and forth on a burner's mixing tube to adjust the flame. The taper was quite modest; increasing tube diameter about 1/8" in 1-1/2" of length. Today you can buy flame nozzles with much more radical tapers that work just as well on their burners as the classic model did in its day, but don't try to run them on an old Ron Riel burner design; they won't work there. Nor will one of my step burners.

When you change one burner part other parts need to change as well, because they all must work together in a balanced fashion. So, when we forget balance we might build Piggyback burners in our pride, or we can allow progress to pass us by from inattention. Yup, the new radically tapered burners surprised me as well; proving its never too late to have egg on your face :rolleyes:

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Jet cleaning ain't no small deal

Three weeks after I made him a 1/2" Mikey burner, my best friend Bud called to tell me his burner wouldn't run. I asked if he had checked to see if his burner's MIG tip was clogged, and he said that wasn't possible. Bud leaves 45 minute away, but his coffee pot was always full, so...

After unscrewing the MIG tip, I inserted a wire file from a set of torch tip cleaners, and out popped a little black tar ball. Now ya gotta understand that Budd is a lot smarter than me. When I was a ship-fitter he was a lofts-man. I looked into his eyes with a straight face, and there was more goodies than Bud's coffee in my day :D

That burner had a .023" MIG contact tip for a gas jet, which means it's meant to run .023" welding wire through. The actual hole diameter is .031"; that's howitzer size compared to a .005" jet hole, which you can actually run into with with some air/fuel torches, which guys use for burners in tiny two-brick forges.

Bud purchased his propane fuel at a bargain basement dealer a couple of blocks down the road from a farm supply store. Back in those days most propane in Washington state came from a storage tank (which burned down in a big fire a few years back). The way they sold bulk propane to various dealers was from four different hose pipes stacked vertically from one another. The worst bargain basement quality came from the bottom hose. Guess where his dealer's propane came from.

A quaint story? Well here's another one. At one point I cut into a lot of used five gallon propane cylinders; some of them were quite old, but still clean inside. Others, although much newer. had tar in their bottoms. The worst of the lot seemed to be Blue Rhino brand. So, when local giant hardware stores started doing exchange cylinders, guess what brand they were?

The point here is that propane isn't like triple refined butane fuel for blue flame lighters. And bargain propane can be a whole lot worse. Do you even have a set of torch tip cleaners? Are you planning to build a two-brick forge without a clue how to go about cleaning its air/fuel torch?

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By trade, I sometimes diagnose propane systems and appliances.  On one of my jobs, I ended up finding a low supply volume at the appliances.  The supply line dropped from the tank under the floor about 12 inches, ran underneath the place for about 30 feet, and then rose out from under the floor to the appliances.  This plumbing arrangement formed a bit of a trap and I ended up finding that entire 30 foot length of 3/4 run filled with a yellow oily smelly liquid.  I suspected it was from the odorant they add to the propane.  Moral of the story, listen to Mikey.  If a 3/4 pipe can be blocked, imagine how small the orifice is in your burner.

Another thing about propane but in a different direction, propane is a refrigerant(R-290).  This is why when talking of mixing propane with air, things are brought up like vapor vs gas, mist, and droplets.  There is much more going on then spraying one simple gas into another.  Without getting too much into it, your cylinder is filled with partial liquid and partial vapor/gas at a specific balancing pressure based on it's temperature.  This balance is because the head(vapor/gas) is as saturated as it can be.  The tank supplies from the top so it is supplying this head.  Saturated gas.  Think of it like steam coming out of your tea kettle, heavily saturated gas.  As this mix gains temperature, it becomes less saturated.  Long supply lines can aid in this temperature rise.  In the land of refrigeration, the vapor is usually superheated in the evaporator to assure liquid does not make it to the compressor to cause damage.  While there are systems out there which purposefully superheat propane for combustion use, I advise strongly against it in home brew anything.  Safety first.

Funny enough, have a look at one of the ways R-290 is supplied.  Same threads even.  A bit expensive for running the portable barbeque though.  

r290.thumb.jpg.50e63e1bdaabea16d7e6b462ee672886.jpg

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