Burners 101

[Mikey98118]

                                                                                 Multi-flame burner nozzlees

No discussion of flame retention nozzles would be complete without including multi-flame burner heads; the most popular choice of homemade multi-lame burner heads are ribbon burners, which consist of a brick shaped refractory block obtaining a large number of flame holes; this is trapped within a steel plenum chamber, which is screwed unto a burner’s mixing tube. Ribbon burners have become another “well-worn path.” However, ribbon burners are not necessarily the best path, as they are all large.

    What other multi-flame burner heads are there to choose from? Well, there is the Giberson 2" Mini-Square Giberson Head; an all ceramic plenum chamber and flame nozzle, which is designed to be screwed directly unto a burner's mixing tube (that ends in a pipe thread); this smaller size head has been around for several years. On the other hand, there are some guys who have made flame retention nozzles from a pipe reducer fitting, with a drilled stainless steel face plate; this creates multiple small flames. Giberson's ceramic burner heads are an extreme refinment, while pipe reducer fittings with drilled face plates are pretty basic; but, they both work the same way; creating multiple tiny flames, which slow down far faster than single large flames can; this allows exhaust speeds to be no greater than what is needed to expend the combustion gases; this keeps heat retention at maximum, since the greatest heat loss in this equipment is out the exhaust port.

    Giberson ceramic burner heads will outlast any stainless steel flame retention nozzles—only if handled carefully; these heads were invented to heat glass furnaces, which have slow ramp up speeds and long heating cycles. Use in a forge must be coupled with added care. If you just ramp up the heat in your forge as fast as possible, a broken burner head will be the result.

    Multi-flame retention nozzles, made from pipe reducer fittings will eventually oxidize away, when mounted in heating equipment; how long that takes, depends on the materials used in both the pipe fitting and its drilled face plate; you are best off to use stainless steel for both parts, and for the socket sets screws that hold the face plate in position within the pipe reducer. The face plate takes the most wear from high heat oxidation, and must be stainless steel. The end of the pipe reducer receives less where from oxidation, and should be stainless steel. The socket set screws will oxidize in place within a few heats, if they are made of mild steel; so they must be made of stainless steel, since the plate while probably need to be replaced every few months, when used daily.

    The thicker the face plate the longer it lasts, but the thicker the plate the more work it is to drill. You will want a think enough plate to rest stabile against the pipe fitting’s wall, trapped in place with the set screws. So, a 3/16” to ¼” thick plate, or flat bar should be your choice, to build this part from.

    Most of us do not have a lathe, so how do we shape the inside of the threaded pipe reducer to cradle the face plate in? Well, we use the internal thread as a handy guide; it provides all the indications needed to limit both depth and diameter of the face plate’s pocket, correctly enough to do for this purpose, when free hand grinding a pocket with a rotary stone, or wheel, in a rotary tool or die grinder.

Rotary wheels ? Yes, aluminum oxide rotary grinding wheels kits, which come in two or three different grit grades, and are made to mount on 1/8” rotary spindles, are available through Amazon.com for about $7. The best feature of these wheels is that they are much more durable than wheel shaped rotary stones, because rotary stones are all inclined to break at their weakest point; this is where they are glued to the steel spindles. There are many grades of quality among rotary stones, depending on the material contained in their grit, and how they are glued together; but all of them have this same weak point. After you pay for the finest Dremel stone made of silicon Carbide, only to have its head break off just as easilly as the cheapest aluminum oxide stone, you will instantly understand to point of rotary wheels!   

[Mikey98118]

Note: Cast refractory burner heads (such as Giberson’s) appear to use Greencast 97 refractory (use rated to 3400°F), which gives a smoother casting than Kast-O-lite 30, even with vibration, but is nowhere near as crack resistant as the Kast-O-lite product. Greencast 97L, with alumina spheres included in its mixture (use rated to 3300°F), if combined with vibration during casting, might prove the key to a far better refractory block, than either one of the other choices.

[Mikey98118]

Note: Be careful not to mistake polishing wheels, which use silicone as their binding material, and very fine grit, with hard grinding wheels.

[Mikey98118]

Mixing tube sizes

The first thing you must decide about your burner is what size it will be. Home-built burner sizes are based on schedule #40 pipe sizes (or its equivalent inside diameters in round tubing) which are used as the burner’s mixing tube. These burners were built from fractional water pipe for many years (and many still are). So, it is handy to know what actual inside diameters these nominal pipe sizes have, since it is the inside diameter, you are trying to match with the right gas orifice diameter.

    Actual Imperial (fractional) pipe diameters are larger than their nominal pipe sizes, both outside and inside. If you choose tubing instead, it will seldom be an exact match with schedule #40 pipe sizes, so choose a little larger inside diameter, when possible (rather than a little smaller), for your burner’s mixing tube. Imported stainless-steel tube can be a handy alternative to fractional tube in the smaller sizes, and is more likely to match up well with most stainless-steel funnel shapes. Imported cast stainless steel pipe, while being advertised in inches on Amazon.com, are nearly all made to metric dimensions; not fractional, no matter what their online advertisements claim.

 Pipe dimensions:                    

(A) 1/8” schedule #40 pipe is 0.405” O.D. x 0.270” I.D.      10x8mm tube (0.390” O.D. x 0.312” I.D.). The burner’s flame retention nozzle size is 0.493” I.D; this is sufficient to heat 22 cubic inches on naturally aspirated burners. Turn-down range for this burner size i 1,875 to 18,750 BTU per hour, when burning propane, and 2,494 to 24,937 BTU per hour when burning propylene. It would take two of these burners to heat even a two-brick forge on propane.                                                                                

(B) 1/4” schedule #40 pipe is 0.540” O.D. x 0.364” I.D.      12x10mm tube (0.468” O.D. x 0.390” I.D.) tube. The 1/4” burner’s nozzle is 0.622” I.D.; this is sufficient to heat 44 cubic inches on naturally aspirated burners. Turn-down range for this burner size is 2,500 to 25,000 BTU per hour, when burning propane, and 3,750 to 37,500 BTU per hour, when burning propylene. Two of these burners will easily heat a coffee-can or one gallon paint can forge to welding temperatures. A single burner this size must be perfectly made, in a properly designed forge to reach welding temperatures.                                                                                                                                                   

(C) 3/8” schedule #40 pipe is 0.675” O.D. x 0.493” I.D.       14x12mm tube (0.546” O.D. x 0.468” I.D. tube. The 3/8” burner’s nozzle is 0.824” I.D.; this is sufficient to heat 88 cubic inches on naturally aspirated burners. Turn-down range for this burner size is 5,000 to 50,00 BTU per hour, when burning propane, and 7,500 to 75,000 BTU per hour, when burning propylene.  Two of these burners will easily heat a non-refillable two gallon refrigerant or helium cylinder forge to welding temperatures. A single burner this size must be perfectly made, in a properly designed forge to reach welding temperatures.                                                                                                 

(D) 1/2” schedule #40 pipe is 0.840” O.D. x 0.622” I.D.     18x16mm tube 0.702” O.D. x 0.624”) I.D.) tube. The 1/2” burner’s nozzle is 1.049” I.D.; this is sufficient to heat 175 cubic inches on naturally aspirated burners. Nearly 5/8” actual inside diameter. Turn-down range for this burner size is 10,000 to 100,000 BTU per hour, when burning propane, and 15,000 to 150,00 BTU per hour, when burning propylene.  Two of these burners will easily heat a five-gallon paint can, or used propane cylinder, forge to welding temperatures. A single burner this size must be perfectly made, in a properly designed forge to reach welding temperatures.                                                

(E) 3/4” schedule #40 pipe is 1.050” O.D. x 0.824” I.D. (imported cast stainless pipe is 1.026” O.D. x 0.831” I.D.). 20mm pipe nipples and couplers are 0.78” The 3/4” burner’s nozzle is 1.315” I.D.; this is sufficient to heat 350 cubic inches on naturally aspirated burners.  0.075” larger than ¾” diameter. Turn-down range for this burner size is 20,000 to 200,00 BTU per hour, when burning propane, and 30,000 to 300,000 BTU per hour, when burning propylene. Two of these burners will easily heat a five-gallon paint can, or used propane cylinder, forge to welding temperatures. A single burner this size must be perfectly made, in a properly designed forge to reach welding temperatures.                                            

(F) 1” schedule #40 pipe is 1.315” O.D. x 1.049” I.D.  1” schedule #10 pipe’s outside diameter is 1.315” by 1.109” inside diameter; this is sufficient to heat 700 cubic inches on naturally aspirated burners. Single or multiple one-inch burners are used in commercial forges, and  pottery kilns.

Note: “Sufficient to heat” means that it can raise a properly built forge interior of those cubic inches to welding heat, or bronze, in a properly built casting furnace, to pouring temperatures. Are these figures legitimate? In fact, they are under stated; not over reaching.

[Mikey98118]

 

So, it would be reasonable to ask just how good a burner qualifies for these figures? We are not discussing some perfect burner, with a compact neutral flame (even though I'm a notorious picky-butt). All the burner needed to reach these goals, is what was considered a good burner a quarter-century ago. If the burner can put out a good enough flame to not have any tinge of green in it, and not produce an exit flame from the equipment exhaust opening, it will be good enough to succeed, so long as the the equipment is properly made. Even a 40/60 flame will do the job; that is forty percent primary flame to sixty percent secondary flame.

The point of striving for a superior flame from your burner, is to reduce the area needed for complete combustion to occur within the heating equipment. But there is a lot of latitude between a perfect flame and an acceptable one

[Mikey98118]

14 minutes ago, Mikey98118 said:

 

So, it would be reasonable to ask just how good a burner qualifies for these figures? We are not discussing some perfect burner, with a compact neutral flame (even though I'm a notorious picky-butt). All the burner needed to reach these goals, is what was considered a good burner a quarter-century ago. If the burner can put out a good enough flame to not have any tinge of green in it, and not produce an exit flame from the equipment exhaust opening, it will be good enough to succeed, so long as the the equipment is properly made. Even a 40/60 flame will do the job; that is forty percent primary flame to sixty percent secondary flame.

The point of striving for a superior flame from your burner, is to reduce the area needed for complete combustion to occur within the heating equipment. But there is a lot of latitude between a perfect flame and an acceptable one

So, if all we need is more interior room to complete combustion in, and if we would rather have bigger forges anyway, its a freebee, right? WRONG! I'm telling you what you can get by with; not what is the best move. "There ain't no free lunch." The larger the forge interior the greater the area of heat loss by conduction, which requires more fuel to keep internal surface temperature sufficiently high, which bites you right in the fuel bill.

Latitude is a good thing, when you're just getting started. Efficiency is the right move in the long run.

 

[Mikey98118]

The exit hole on a Frosty "T" burner's gas orifice, faces straight toward the opening of the burner's mixing tube. Maximum air induction is obtained by filing the gas tube's MIG contact tip shorter; creating more distance between gas orifice and the opening.

The exit hole on a Mikey burner's gas orifice, faces straight toward the opening of the burner's mixing tube. But, maximum air induction is obtained by sliding the gas tube's MIG contact tip closer; creating less distance between gas orifice and the opening.

Why would apparently opposite moves create the same outcome? Because the incoming air stream flows past the gas orifice from behind in a Mikey burner. Two incoming air streams are induced into the burner from right angles to the gas orifice  in a "T" burner.

So, the method is different, but the reason why, and the outcome is the same in both kinds of burner.

 

 

The reason why being maximum air induction.

[Mikey98118]

Silver Brazing to S.S. Funnels

Being able to silver braze funnels to pipe or tube products is a great convenience. Unfortunately (even with sausage stuffing tubes included), working with what is available in the market restricts your possible repurposing selections, because the funnels that can easily be mechanically trapped within (or on) mixing tubes are very limited. Also, some funnels of superior size and/or shape have spouts that are way too small for your purposes, and must have their small ends cut off, and then be silver brazed onto the mixing tube, without benefit of a tubing in tubing joint to fill.

    Once you have the mixing tube cut to length, measure how long it and the funnel are together; Buy a long enough length of 5/16-18 threaded rod from your hardware store, (or an online source) to extend comfortably beyond both funnel and mixing tube, with room to spare for a nut and large flat washer on the tube end, and another washer or sheet metal plate to cover the funnel’s large opening. This arrangement keeps the parts trapped tightly together, in straight axial alignment. Preparation for this work starts by laying a free-flow burner’s gas assembly’s mounting plate and rivet nut, or drilling and threading a force-flow burner’s aluminum fan mounting plate, because it will be used, after lay-out and before cutting out is completed, to help hold the funnel and mixing tube in correct  position for brazing.

Using flat washers to trap the funnel and mixing tube together for silver brazing: The mounting plate can be employed, together with a rivet nut to secure the forward end of a mixing tube against a funnel, for silver brazing these two parts on free-flow burners. The funnel on smaller burners can be secured with a second washer and hex nut. Larger burners will use the rivet nut on a mounting plate cut from sheet metal on the funnel bottom, and a flat washer secured with a hex nut  over the front of the mixing tube.

Using a flat washer and aluminum plate to trap the mixing tube: Forced-flow burners use a flat washer and hex nut on a threaded rod, to trap the mixing tube against the funne. The bottom of the funnel is trapped in place with a ½” thick aluminum mounting plate, which is drilled and threaded with a 5/16-18 tap, so that it can be used, instead of a rivet-nut, to hold the threaded brass gas tube.

    First lay the aluminum plate out in a square, which is 1” wider and longer than the outside dimensions of the axial fan. Then, scribe lines are from corner to corner, in both directions to establish the plate’s center. A prick punch is used to mark where the lines cross, and a circle is scribed, using dividers; the circle is equal to the funnel opening—never more; although it can be smaller. If you are going to use a hole saw to cut the center hole, go ahead, and cut into the plate ¼” deep at this time, since you while not be able to use the saw’s pilot bit to keep it centered, after drilling out the hole to screw in a 5/16-18 threaded rod. Afterwards the existing trench in the plate will end the need to use the saw’s ¼” pilot bit.  At this point the pilot hole is drilled and threaded, to screw a 5/16-18 threaded rod through, so that this part can be temporarily employed as an aid for braze work. If you are going to use a line of holes, the divider is narrowed 3/16”, and a 3/8” smaller inner scribed circle is also made, before drilling and threading a 5/16-18  hole.

    The mounting plate can be used “as is” on free-flow burners. Forced-flow burner fan ½” thick aluminum mounting plates are first laid out in a square, which is 1” wider and longer than the outside dimensions of the axial fan. Then, scribe lines are scribed corner to corner in both directions to establish the plate’s center. A prick punch is used to mark where the lines cross, and a circle is scribed, using dividers; the circle is equal to the funnel opening—never larger, although it can be smaller. If you are going to use a hole saw to cut the center hole, go ahead, and cut into the plate ¼” deep at this time, since you while not be able to use the saw’s pilot bit to keep it centered, after enlarging the hole to screw a 5/16” threaded rod into. Afterwards the existing trench in the plate will end the need to use the saw’s ¼” pilot bit. At this point the pilot hole is drilled and threaded, to pass a 5/16-18 threaded rod through, so that it can be temporarily employed as an aid for braze work.

    If you are going to use a line of holes, instead of a hole saw, or jigsaw to get rid of the center of the plate, the divider is narrowed 3/16”, and a 3/8” smaller inner scribed circle is also made, before drilling and threading a 5/16-18 threaded center hole.

Note: It is vital that the center hole be drilled perpendicular to the aluminum plate. Otherwise, the funnel will not remain axially true to the mixing tube during silver brazing.

     A brazing assembly consisting of the 5/16-18 threaded rod is used, along with the aluminum mounting plate, mixing tube, aluminum plate, plus a nut and washer, is used to hold the funnel and mixing tube in line while they are being joined. The funnel and mixing tube are held tightly together and axially true for silver brazing this way.

    Before placing the mixing tube against the funnel, check both tubing ends to see if one is cut more squarely; that is the one to place against the funnel; this assures a good match up with the funnel, and should be used for the joined end; the other end, which you might have to cut to length, must be double checked with a square, and power sanded to a reasonable proximity to perpendicular with its axis. How close is close enough? Without a lathe you will not even approach perfection; nor do you need to. Double checking your work with a square will bring you more than close enough for your needs, because the flat washer allows a little play in the parts.

    The mixing tube must be ground to mate up closely to the funnel’s taper; this is very important for easy whetting of the silver braze alloy into the tube/funnel joint. 60 grit wet/dry sandpaper can be attached to the funnel with double sided tape (sticky on both sides), to finish shaping the tube end exactly to it, and the mixing tube is turned back and forth on it.

    Next, the end of the funnel must be scribed, to mark where it meets the tube’s end; use the dividers to measure the length of the internally beveled area on the tube’s end, and then a mark a second line 1/8” further up the funnel wall than that. Cut the end of the funnel away at the second line. The 1/8” the excess material is ground away after the joint os silver brazed. You want to leave enough excess funnel wall  to catch any excess filler alloy, while the filler completely covers the joined area.  After brazing, the joint must be cleaned, and the rest of the excess material must be ground or power sanded back even with the inside surface of the mixing tube.

    It takes a minimum of 53% silver content for filler alloys to be effective when silver-brazing stainless steel parts, and those are difficult to find. However, 56% and higher silver content brazing alloys are easily available on the open market, and will work better on stainless to stainless, or stainless to mild steel joints; they have the lowest temperature flow range (around 1200°F; 649°C), and best wetting characteristics. High silver content filler alloys are the only ones that are going to work well on S.S funnels.

Procedure for joining thicker mild or stainless-steel coupling or mixing tube to thin S.S. funnel: Both tube and funnel are cleaned, scoured and fluxed before being secured tightly together with fender washers, etc., on a carriage bolt or length of all-thread, and placed on a level surface. Using a propane or propylene torch with a brush flame, mostly heat the thicker tube with the primary flame at least ¼” away from the parts. Only allow the secondary outer flame envelope to touch the part surfaces.

    Pass the flame back and forth along the joint. Once the flux indicates the correct temperature has been reached (black flux by bubbling; white flux by bubbling and turning clear), dip the filler onto the joint area, and heat the drop or so of silver braze filler with the torch, while allowing the flame to also heat the funnel a little bit; as you again pass the flame back and forth, the heated joint will suck the filler in, spreading it along the joint. Turn the parts to expose an area beside the one you just finished, and repeat this process, over and over until the entire joint is filled.

 Note: Make sure to buy threaded rod (AKA all-thread) that matches the size and type of  external thread on your gas tube.

    When you silver braze pipe or round tube onto a funnel, it is important to ensure a very close fit for a good braze job, leaving a gap of no more than 0.005” anywhere that you want the filler metal to flow. Take all the time you need to ensure the best possible fit between tube and funnel, that you can manage. It helps to finish the fit-up by placing sandpaper between the mixing tube and funnel, to finish matching their surfaces closely. Any convex curvature in the funnel wall will increase your work (but is likely to be well worth it). When the tube or pipe is a close fit, note how wide the area of contact has become; this is what caused all that extra work, and is also the reason why this joint will end up strong enough to serve. If your  brazed joint ends up with gaps in it, consider closing them in with silver solder.

    Grind or power sand a bevel in the end of the tube as close as possible to the funnel’s shape, and then scribe or ink an outer line where the two parts meet. Remove everything that hinders your view of the funnel area you are going to remove. Measure the widest section of the tube’s inner bevel, and add another 1/8” of distance to it; then mark points along that distance for an inner cut line. Cut away the funnel up to those points. Place the tube back on the funnel, and ink a line on the funnel where the inside surface of the tube meets it. Grind or power sand right up close to, but not touching, that line; this is to keep your finish sanding or grinding work inside the funnel to a minimum, after the brazing is finished. But, a slightly smaller opening in the funnel than the inside surface of the pipe or tube, provides a ledge to help prevent the filler metal from making a mess; it is well worth a little extra grinding or power sanding afterward, to prevent that.

    Sand or wire brush the area that you want to braze, to roughen part surfaces (promoting capillary flow), and then flux both parts; but only on the areas where you want the filler to flow. Clamp both parts together, to keep them securely trapped in position during brazing. You will have to use a silver braze alloy with at least 56% silver content, and flux meant for use on stainless-steel. 65% silver filler is even better, because the higher the percent of silver in your filler alloy the better it wets part surfaces. Wetting is the necessary first step to the filler flowing over part surfaces and into the joint.

Note: Both soldering and brazing use capillary action to move filler metal over part surfaces in the joint area; For the process to begin, filler metal must start combining with the metal on the surface layer of the part; this is called wetting. Without wetting, the filler metal will just ball up on the part surfaces, and drop off. Silver content in the filler alloy promotes wetting. Stainless-steel’s chromium content is why it requires a filler rod or wire with a high percentage of silver to promote wetting. Chromium is hard to wet, which is why 18:8 is easier to silver braze than 18:10 stainless.

Procedure for joining a thicker mild or stainless-steel mixing tube to a thinner S.S. funnel: Both tube and funnel are cleaned, scoured, and fluxed before being secured tightly together with fender washers, etc., on a carriage bolt or length of all-thread, and placed on a level surface.

    When you silver braze pipe or round tube onto a funnel, it is important to ensure a very close fit for a good braze job, leaving a gap of no more than 0.005” anywhere you want the filler metal to flow. Take all the time you need to ensure the best possible fit between tube and funnel, that you can manage. It helps to finish the fit-up by placing sandpaper between the mixing tube and funnel, to finish matching their surfaces closely. Any convex curvature in the funnel wall will increase your work (but is likely to be well worth the added effort). When the tube or pipe is a close fit, note how wide the area of contact has become; this is what caused all that extra work, and is also the reason why this joint will end up strong enough to serve. If your braze job ends up with gaps in it, consider closing them up with silver solder; this flows at much lower temperatures, so the braze job is in no danger of being ruined.

    Grind or power sand a bevel in the end of the tube as close as possible to the funnel’s shape, and then scribe or ink an outer line where the two parts meet. Remove everything that hinders your view of the funnel area you are going to remove. Measure the widest section of the tube’s inner bevel, and add 1/8” more distance to it; then mark points along that distance for an inner cut line. Cut away the funnel up to those points; this is to keep your finish sanding or grinding work inside the funnel to a minimum, after the brazing is done. But, a slightly smaller opening in the funnel than the inside surface of the pipe or tube, provides a lip to help prevent the filler metal from making a mess; it is well worth a little extra grinding or power sanding after brazing, to prevent that.

    Mount a wire brush in your rotary tool, to remove oxides and roughen the surface of the area that you want to braze, and then flux both parts; but only on the area where you want the filler to flow. Clamp all of the parts together, to keep them securely trapped in position during brazing. You will have to use a silver braze alloy with at least 56% silver content, and flux meant for use on stainless-steel. 65% silver filler is even better at whetting part surfaces.

     When using an air-fuel flame, mostly heat the thicker tube with the primary flame at least ¼” away from the parts. Only allow the secondary outer flame envelope to touch the part surfaces. Oxy-fuel flames should not touch the part surfaces at all. With high-speed air-fuel burners, which can be tuned to a single flame envelope; keep the end of the flame tip ¼” away from part surfaces.

    Pass the flame back and forth along the joint. Once the flux indicates the correct temperature has been reached (black flux by bubbling; white flux by bubbling and then turning clear), touch the filler on the joint area, and heat a  drop or so of silver braze filler with the torch, while allowing the flame to also heat the funnel a little bit; as you again pass the flame back and forth over it, the heated joint area will suck most of the filler in, spreading it along the joint. Turn the parts to expose an area beside the one you just finished, and repeat this process, over and over until the entire joint is filled.

 

[Mikey98118]

Ignition, tuning, and shut-down of Linear Burners

These burners are designed to produce high-speed flames, using elevated pressures through small gas orifices. When you hear Somone bragging about their equipment running on one or two PSI gas pressure; that is because their burner’s gas orifice has a much larger hole. There is no free lunch.

    A popping sound can be made by even a minor gas leak between the a MIG contact tip's thread and the gas pipe—on some high-speed burner designs. Liquid dish-washing detergent in water can be spread on the suspected joint, the gas turned on, and the orifice covered with a finger, to make a soap bubble test for a gas leak at this spot

    These are hand-built burners; their performance will vary. Some burners might be a little touchy while cold, when you tune them out in the open air; once mounted in equipment, they are far less sensitive; even when cold.

Warning: These burners are designed to use LPG fuel gas (propane, butane, propylene) and various LPG mixtures only. Never burn acetylene or hydrogen fuel in these burners; neither gas can be safely employed in any equipment that is not specifically designed for it. Pure hydrogen will embrittle some metals, when hydrogen atoms are absorbed into them, causing cracking. Oxyhydrogen torches are specially made to burn this gas safely. Acetylene reacts with some  powder metallurgy formed metals, such as copper, zinc, and silver, to form explosive and shock sensitive acetylide compounds. Therefore, oxyacetylene torches are specially constructed, with this danger in mind.

    MAPP fuel gas stopped being produced in 2008, when its last plant was switched over to full propylene production. But other MPS fuels (various mixtures of methylacetylene and propadiene gases, mixed with propane, and/or butane, and/or butadiene), are still available outside the U.S.A. Before morning its loss, know that MAPP fuel gas claimed to be a whole fifty degrees Fahrenheit hotter burning than propylene fuel gas, in return for high shipping fees and insurance premiums, because it contained about fifteen percent acetylene in its composition; a losing proposition.

Caution: Be careful to decrease the gas flow when switching from propane to propylene fuel inside forges and furnaces; it can easily overheat the equipment too much for standard refractory materials, and are likely to melt a stainless steel flame nozzle right off the end of your burner. Propylene is easier to manage, when these burners are being used as torches, in the open air. You need to combine propylene fuel use with a large dose of common sense. You do not need a full third hotter temperature inside your equipment, but rather a gentle bump of a hundred degrees or two, will usually do the trick.

Practice lighting the burner several times outdoors, in a shaded area (propane flames become invisible in bright sunlight). You need to play with the burner for a few minutes, moving that hot nozzle back and forth on the burner’s mixing tube, to produce the sharpest possible flame. I like to leave the long part of an Allen wrench in one of the rear socket set screws, with the screw kept just barely snug, for easy unlocking and movement without burning fingers during this phase of tuning. Place the nozzle’s end so that it is 1/8 longer than the inside diameter the flame retention nozzle, beyond the end of the mixing tube. The right amount of overhang will be somewhere between his point and 1/8” shorter.

    Turn the gas flow on just a little way, and ignite the burner, immediately turning the gas pressure up high enough to blow any internal flame forward from the mixing tube, into the flame retention nozzle. Otherwise, the flame will continue to “burn back” into the mixing tube (until the gas pressure is finally increased), rapidly overheating the burner. In case of overheating, you must shut the burner down and allow it to cool sufficiently, before reigniting it. Once the flame retention nozzle is heated enough for its stainless steel to start turning colors (like a chrome exhaust pipe), open the gas valve up as high as desired. It will take very little practice to know how much to open the gas valve for a flawless burner start up, in the open air. Starting the burner within equipment is usually no bother.

    You Want to see a light blue flame, with a single wave front, no white inner flame behind the wave front, and little to no outer flame envelope (secondary flame) beyond the primary wave front. The outer edge of the flame is called its “envelope”; its forward edge is also known as the wave front. Why would the whole outer edge of the flame be called an envelope? Because gas flames burn from their outer edges, inward.

    When the flame retention nozzle has too much overhang, the flame will soften; a secondary flame will form and grow. Shorten the amount of overhang until the secondary flame disappears; at this point your burner has a neutral flame. Now, shorten the overhang more, and watch the flame color turn darker blue; it has left the neutral flame and is becoming ever leaner (oxidizing); with some burners, the flame will snuff out almost immediately, instead. Other burners can create a highly oxidizing flame before it is snuffed. Lengthen the overhang again until the secondary flame starts to appear, and adjust the nozzle back to just where the secondary flame nearly vanishes; that is where you want to keep the overhang; lightly tighten screws.  When the nozzle starts turning incandescent, lightly tighten the screws again.

    If the flame is leaning off center, shut the burner down, and let it cool off. First, check to see if the gas orifice is axially true to the gas tube; if the problem is in the MIG contact tip, this soft copper part can simply be bent into alignment. If the orifice is a brass 3D printer nozzle, unscrew it, and sand the end of the gas tube to square its face up with the gas tube. If the gas tube turns out is out of alignment, hook up the burner up to a water hose, and turn on the faucet, to see exactly where the stream is canted. Loosen the screws on the gas assembly’s mounting plate, one at a time and place a bit of tape, etc. between the mounting plate and funnel’s flange to see where and how thick a flat washer needs to be inserted to align the flow of the gas jet.

Use the square or calibers to make sure the tube is centered. Use the square’s blade, to compare it with the mixing tube, to ascertain that the flame retention nozzle is centered and in axial alignment the burner's mixing tube.

    Use your digital caliper to measure all the way around the rear edge of the flame retention nozzle, to assure that it is centered on the burner’s mixing tube; then just snug the rear set screws in that position. Next, use its straight edge, all around the nozzle to check that it is parallel to the mixing tube; adjust the three forward set screws, until it is, and then tighten them again. Now, tighten the rear set screws. This method allows you to ensure that the nozzle is positioned parallel and centered on the mixing tube, without changing the amount of its overhang. Ignite the burner and visually check its flame, to assure that it is running true; not canted. When the nozzle is incandescent, tighten all six set screws, again

    The end of your gas orifice should be “in the ball part” for position, somewhere between 3/8” ¼” away from the mixing tube’s opening, but each burner’s gas assembly has a slightly different sweet spot. Move the gas assembly’s tip back and forth to find it. At the best spot, your burner should roar the loudest. In any case, do not let the tip get closer than 1/4” to the mixing tube opening, or further away than 3/8”. If you think your burner runs better at some other distance—you are simply kidding yourself.

    So, if you do not see any difference in the look of the flame, but only in its sound, what difference does this task make in burner performance? When you hit the sweet spot, your burner’s gas jet draws in (induces) the maximum amount of air, at every gas pressure level. So, you will always be able produce the best performance with the end of its gas orifice positioned at the sweet spot.

    Do not be surprised or concerned by thin yellow, orange, or red streaks in the flame, which can develop after the nozzle heats up sufficiently, or immediately, if you did not clean all debris from within the burner’s gas assembly; they are caused by a reaction between the superheated oxygen and the and the stainless-steel of the flame retention nozzle (much more prominently from #304 stainless alloy than from #316), and by any other burning metal debris. Streaks from copper or brass debris, will burn green.

    Heated gas rises, and so, the burner’s exhaust will enter your burner’s air intake if the burner is held near enough to the vertical down facing position, destabilizing the flame (this is unlikely to happen, unless the burner is connected to hose; otherwise, a fuel canister will probably dump liquid fuel into the burner before you reach that point, causing even worse problems). Practice bringing the burner to this position and then backing it off, until you feel confident of your understanding.

[Mikey98118]

                               Today's gas assemblies for today's linear burners

Air flow into a burner’s opening can be forced through mechanical means (a fan or air compressor), or induced by the low-pressure area created with a fuel gas stream (Bernoulli’s Principle). As the air that is passed through a linear burner’s cone shaped air opening, it gets spun. Swirling air does the best job of mixing with a fuel gas for the least drag on mixture flow. If you want complete combustion in your burner’s flame, that takes good fuel air mixing. Thus, pipe reducers became the air entrances of choice on early burner designs, and are still the favorite choice today.

    About half of those deigns plumbed the fuel gas, in what we call cross pipes: their advantage was that they could be used to feed multiple burners. The other half of forge deigns plumbed each burner straight down the burner’s air entrance, but most of them were hold rigidly in one position. Movable gas pipes, with gas orifices that could be placed exactly at the right distance from the entrance to a burner’s mixing tube, was the next logical improvement.

    Which brings us to methods of holding a burner’s gas tube in position; this isn’t as simple as merely trapping it at the right depth within a pipe reducer. You also need to ensure that it is held dead center in the air opening, and axially true to it. What constitutes a practical method of mounting your burner’s gas assembly depends on what you employ as a conical shape for its air entrance.

    And here is where you run right into the problem of choice; or rather the lack there of. Pipe reducers come in limited sizes. Even more limited if you are not a forge manufacturer, who can order parts in quantity. For most individuals, the list of pipe reducer fittings, is shortened further; down to what your hardware store happens to carry. It is exceedingly hard to find reducers with greater than a two to one restriction ratios (2:1). But the acceptable restriction range for burner entrances starts at two and a half to one (2.5;1) and you are best off at three to one (3;1). Pipe reducers only became the popular air entrance choice, because they could be threaded unto a burner’s mixing tube. There is a whole world of other part choices to choose among, from kitchen funnels, to sausage stuffing tubes, etc.

However, with the change from thick-walled pipe fittings to stainless steel sheet metal parts, comes the need for a change in how gas assemblies get attached to the burner’s funnel entrance. Mounting plates, made from flat washers, will serve on burners with funnel openings up to two inch in diameters. Larger mounting plate diamaters must be cut from sheet metal. Three air entrances are cut and ground between three ribs, which are then screwed or silver brazed unto the funnel’s opening. An externally threaded brass gas tube runs through the mounting plate’s center hole, and is held there with a special nut.

Rivet nuts (AKA Rivnuts) are internally threaded hollow rivets; they are your best choice for attaching externally threaded gas tubes onto mounting plates; they are press fit in place, through deformation, like solid rivets. The main difference is that they are designed to distort easily enough that they can be trapped in place with two wrenches; they will reshape and be trapped into place, centered and perpendicular, on flat washers, or on cut out sheet metal parts. This creates a very strong joint that can be perfectly positioned on the mounting plate.

    Rivet nuts come in both 5/16-18” and M8 sizes, allowing use of  5/16” x 3/16”and 8mm by 5mm (or 4mm) brass gas tubes to be externally threaded as movable gas tubes in rivet nuts. Both tubing sizes are also thick enough to be internally threaded for MIG contact tips, or 3D printer nozzles as gas orifices. 5/16” hose couplings can then be attached to the gas tube.

[Mikey98118]

Materials needed to make a homemade rivet nut setting tool

(A)  One grade #8 (SAE standard) steel socket head cap screw or bolt, of the same thread size as the rivet nut, and at least long enough to accommodate every part on the tool, and still engage all the threads on the rivet nut. The reason to use a high strength cap screw or bolt, is that it is much tougher than a low carbon mild steel cap screw or hex bolt; extra tensile strength is best, when using a small diameter cap screw or bolt as part of your homemade rivet nut setting tool. Mild steel screws and bolts have about one-fourth the strength of high-grade screws and bolts, which are made of medium carbon content alloy steel, which has been quenched and tempered for maximum tensile strength.

(B)  Two brass flat washers, to sit between to the flange screw and the head of the high strength bolt is helpful (providing a bearing surface). The washers simply help the bolt to turn more smoothly.

C) A flange nut that is drilled out to a larger size, to freely slide over the tightening bolt’s thread (it is there to be held in place by a wrench; this prevents the rivet from being turned by the revolving bolt head (you do not want the rivet nut to start turning in the hole, while being crushed into shape).

(D)  An open-end wrench for the wrench to keep the drilled-out flange nut still, and a and a box wrench to turn the bolt or cap screw’s head with.

Drill a hole in the mounting plate that is as close to the rivet nut’s outside diameter as is feasible. A snug fit is ideal. The more gap there is between the rivet nut and the hole, the harder your job of riveting will become. The less gap there is between the rivet nut’s body and the hole it gets pushed into, the sooner it starts becoming trapped in place (and no longer able to turn under the tightening bolt).

    Slide two brass flat washers onto the bolt. Slide the drilled-out flange nut onto the bolt, with its locking side facing the rivet nut. Screw this assembly unto the rivet nut, just finger tight. Push the rivet nut into the hole in the mounting plate. Place the open-end wrench on the flange nut, and the box wrench on the tightening bolt. Turn the bolt head until the rivet nut is securely fastened onto the mounting plate, using the open-end wrench on the drilled-out flange nut to keep it from turning, too. You can find several videos of this process on the Net, with variations in nut and flat washer choices.

    Fender washers come in a limited number of center hole sizes, but it is not much work to drill or grind a fender washer’s center hole larger, to fit a rivet nut diameter. Grinding is an easy way to increase a hole in a sheet metal mounting plate, a little larger than the largest bit that can be chucked in your drill motor.