Mikey98118

                                                                                Cleaning gas orifices

Propane comes in widely varying quality from different sources, but even the best of it is not perfectly clean (we aren’t talking about triple refined butane lighter fuel here). The waxes and tars that all commercial propane contains, can plug small orifices on MIG contact tips, and the even the smaller orifices of 3D printer nozzles; ruining burner performance, while rapidly increasing pressures on gas hose and gas fittings to full cylinder pressure, unless a proper regulator—not just a needle valve—is employed. Poor quality “bargain” propane can form tar balls quite rapidly.

    It then becomes necessary to shut down and clean the burner by poking the tar ball out of its gas jet with a set of torch tip cleaners (or piano wire for very small orifices), and blowing it back out through the larger diameter gas tube with air pressure; canned air is fine for this if you do not own a compressor.

How likely is this problem to happen? The answer has more to do with gas orifice diameter than propane quality. I only know of one instance of low quality propane plunging a MIG tip orifice (with an a 0.031" through hole. On the other hand, small commercial propane torch-heads, which depends on tiny gas orifices to work, are commonly plugged shut with two or three 16 oz. canisters of propane.

To be fair, a Mr volcano single burner forge is a pretty good example of that progress.

This is because the vaporization temperature of propane is –44°F. As the propane is bled off from the fuel cylinder, it creates a refrigeration affect, which cools the remaining propane in the tank. Ambient air warms up that propane by conduction through the cylinder's wall; this is why tanks that are low on propane freeze over much quicker than full tanks, even on a warm day; it is also why people gang two tanks together, thus doubling the amount of wall area, and delaying that fow tank freezing problem, while keeping cylidner sizes small enough to deal with easily

Also, hotter burners in more efficient forges greatly reduce the amount of propane per hour being consumed. Over the last twenty-four years I have noticed a steady decline in readers asking your question, as burner and forge designs have improved (hint, hint).

Covering the Satanite with Plistix is a very good idea.

The low ambient temperature will not prevent you from forging; it will cause a smaller cylinder to frost over faster, if the cylinder is kept outside, where it belongs. If the cylinder is used indoors, which I discourage, how fast a five-gallon cylinder will become covered in frost will depend on how warm your shop gets.

So what is bad about the cylinder frosting over? No, it does not necessarily mean that your burner will shut down; at least not right away. What will happen first is that the gas orifice will start spitting out bits of frozen fuel with the fuel vapor, and will start faltering. Eventually, the burner will cut out, until the cylinder wall can warm up a little bit.

                                                                          Square mixing tubes?

so there was a discussion going on in another thread over the merits of a forge that featured a square tube as part of its burner; this is not the first time burners with square mixing tubes have come up. I have never seen such a burner in action, and am not inclined to prejudge its performance. But two questions popped into my head about its choice. In the first place, why use a square tube, rather than pipe or round tube? The answer came just as fast; it was all someone had. Anyone who ever spent time working ornamental iron will not find that surprising.

The second question is what would I have none, if I was working in such a shop, knowing what I do about burner design? And again the answer was just as quick; twist the mixing tube.

Some of you might have fun with the idea.

3 hours ago, bbderoff said:

 

 

 

 

 

I would suggest 2.5 times the mixing tube diameter; this will get the flame close to perfect. Such a flame is easy to fine tune for anything from oxidizing to reducing by adjusting the amount of the flame retention nozzle's overhang past the end of the mixing tube, a slight increase or decrease in the size of the gas orifice, or an adjustable choke plate at the air entrance.

Inline gas tubes have two advantages over cross pipes, whether those pipes only have drilled holes for gas orifices; even if they have MIG contact tips or 3D printer nozzles in threaded holes in the pipe, they still lack those two adantages, which are:

(1) the added length of the gas tube helps accelerate the fuel gas that exits through the gas orifice; the strength of this gas jet is the motor that energizes air induction into the burner's mixing tube.

(2) The ability to move the end of the gas orifice back and forth, to find its sweet spot, where it will induce the most air into the burner per pound of gas pressure, or which can be moved to a further distance from the mixing tube's entrance, to soften the flame, when desired.

Cannot a flame be softened by moving the flame retention nozzle's end a little further from the end of the mixing tube? Yup; but it is very difficult to find tune that softening with the flame retention nozzle, compared to just moving the gas orifice. Also, using the gas orifice does not require taking the burner out of the forge.

So, what advantage is such a tool with 15/16" cutoff discs? Compared to a high power power rotary tool, such as a Black and Decker RTX-6 (220-watts), or a Votoer 260W(watts) rotary tool, none at all, with such a small disc. The point is that you can run them successfully in a die grinder. As disc diameters increase the added power of a medium strength die grinder rapidly comes into its own.

Nevertheless, we don't run with scissors, slap the junkyard dog, or cut with high power die grinders in our hands

On 1/7/2024 at 10:56 AM, LeeHene said:

It also used a whole lot more propane. (I'd estimate about 3x more, based on regulator adjustment and air required to balance it.)

That arrangement needs more work. You should only use a little more fuel to heat your forge up to yellow heat. Sometimes you need to just travel the well worn path, to get what you want. Look into slide-over stepped flame retention nozzles for the burner. If the there isn't sufficient room to use such a nozzle, without messing up your burner opening, build a smaller burner, and try that out. If you find that the saller burner only brings your forge up to orange heat, move the baffle wall 1" away from the exhaust opening, so that it can be closed down closer around the heating stock, without building back-pressure on the burner. Don't forget to paint the baffle wall's bricks with whatever you used on the rest of the forge interior.

The nicest part about small 12V DC motors is that they can be replaced very cheaply, when the time comes.

When I first started experimenting with axial computer fans on forced-flow burners back in 2014, the oddity of powerful motors being mounted on burners, as though they were coal forges, and then chocked back, to supply what ended up being only a whisper of useful added air, struck me as quite funny.

So much for looking for surface cutting answers by painting by the numbers, like good little boys and girls.

    The only advantage to cutting with angle grinders is their safety handles, which stick out at right angles from the tool's body. Worse is the reason for cutting with them; to save money by using a single tool for two tasks.

    Supposing we cut through all the commercial baloney, and get down to what counts; the best and safest possible performance, during various surface cutting jobs--at a sane price. Various surface cutting, and cutoff tasks call for cutoff discs from 15/16" up to 3" with corresponding speeds from 25000 to 10,000 RPM, and torque from 160-watts up to 300-watts. So what you need to start with is a  medium strength die grinder. Variable speed is no problem with a DC motor; just plug a fan speed control into its cord, and plug the controller into the wall. You will nearly always be far better off using an external controller, and leaving any speed control circuit on the tool at full speed (effectively by-passed).

    A medium power die grinder (around 400-watts) is already more power than you want; thith a full power die grinder you will not be able to lower power enough for delicate work, without turning the tool down below half-power; a big mistake if you want that tool to last!

    Next, you want to build your own safety handle to mount on the tool's neck, at a right angle, to provide the same superior grip, which is all that allows people to "ride the tiger"

Back in the early eighties Makita started marketing lighter more portable power tools; they first came out with a 5" angle grinder, and then a 4" angle grinder the following year, within a couple more years 4-1/2" angle grinders were marketed by multiple manufacturers; at first, they were all knockoffs of Makita's 4" model, with a larger spindle. The advantage was that they could spin cheaper grinding wheels than the high priced Makita 4" wheels.

In the following thirty years 4-1/2" angle grinders have come dominate the market, which is good. Unfortunately, these grinders have steadily grown more powerful, which is dangerous...if you want to use them with a cutoff disc. Today, using such a tool for surface cutting has come down to "riding the tiger."

About five years back the Chinese came out with 3" 280-watt angle grinders, which were the right size and power for surface cutting steel parts, with reasonable safety. Alas, they were 220V, with made them unpopular outside of Europe and Asia.

Then, along came 3" 12V angle grinders, which are under powered, but at least reasonably safe to use for surface cutting.

18V to 20V angle grinders have at least reduced torque back to the level of the original Makita 4" angle grinders, but are still over powered for safe surface cutting.

But, some of the latest model 18V to 20V angle grinders are variable speed; these can now be used with reasonable safety for surface cutting, by reducing them to half-speed during cutting.

Conical air entrances (funnels, pipe reducers, etc.): Why recommend thin sheet metal funnels for air entrances on linear burners? Back in the eighties, Australians started making homebuilt LPG burners (this is a mixture of liquid petroleum gases; primarily propane and butane); they mounted mild steel (butt-weld) pipe reducer fittings, on the end of pipes that they used as mixing tubes; these gave very good flow dynamics and were easy to assemble for people who could weld. Americans seem to have followed suit, as best I could determine from searching the Net during the late nineties.

    As homemade linear burners gained in popularity, threaded bell reducers became popular with people who could not weld, or did not want to spend the money for thick walled butt-weld pipe reducers (meant for use in hydraulic lines). Unfortunately, threaded reducer fittings do not quite share the superior flow characteristics of butt-weld reducer fittings. Available choices of in-stock threaded reducer sizes are constantly being diminished at hardware stores (as steel water pipe continues to be marginalized by plastic pipe). Worst of all, are cheap imported pipe fittings with misaligned thread, which often end up out of axial alignment with the burner’s mixing tube; when using them, take a few minutes to screw the parts together and have a look before choosing parts.

    Thus, we come to the use of stainless steel kitchen funnels; but this is not meant to preclude other tapered shapes being used as air openings. There is a generous variety of part choices available; from butt-weld thin-walled stainless-steel pipe reducers, to sausage stuffing tubes, to kitchen funnels, icing tips, French-fry cones, etc.

    The easiest way to build a superior linear burner, is to employ a stainless-steel sausage stuffing tube (SST) as its body; then, mechanically affix a gas assembly onto its funnel flange, and a flame retention nozzle over its tube portion. With the present high prices for stainless-steel tube and pipe, this will greatly reduce your costs (along with your work load), compared to what is needed for a high-speed tube burner. Another advantage of SSTs over other part choices are that they are constructed with perfect axial alignment between funnel section and mixing tube, and with generous flanges already affixed to true right angles, to screw gas assemblies to.

    Some sausage stuffing tubes have long funnel shapes eliminate any need for fit-up and silver brazing of funnels to mixing tubes, and greatly reduce the work needed to employ them on others. Kitchen funnels, canning jar funnels and schedule #10 stainless-steel pipe reducers can also be affixed to mixing tubes with screws, but are not as easy to fasten a gas assembly’s mounting plate to. If your burner is ½” or smaller size, you will not find an easier or cheaper way to build it.

    The extra wide (1/4” to 3/8”) rims at the large openings of SSTs are called flanges; these are normally used to securely trap an SST on a sausage grinding machine. For your purpose, flanges enable easy mounting of a fender washer (or sheet metal) mounting plate, and gas tube assembly onto the funnel’s mouth (large opening), via screws, silver brazing, or silver soldering.

    Sausage stuffing tubes are long enough to make 1/4”and 3/8” pipe diameter equivalent burners, needing only a flame retention nozzle added on. Cutting back the SST tube section to between one- or two-inch lengths, and inserting it into a mixing tube, is recommended for larger burners in most cases; at other times, a smaller diameter mixing tube can be inserted within the SST instead, to create a convenient burner size. The mixing tube is placed into, or over, the SST in accordance with which position will provide the closest match with a 3:1 ratio between funnel opening and a mixing tube’s internal diameter.

Note: When a mixing tube is fitted inside the SST, you must remember to internally bevel its rear edge, to streamline mixture flow. You must also ensure a gas tight fit between the two parts, if the SST is fitted over the mixing tube; hardening thread-locker, gasket sealant, or an interference-fit can all see to this.

    Sausage stuffing tubes come in a limited number of sizes, but they can be used to construct 1/8”, 1/4”, 3/8”, 1/2”, 3/4”, and 1” burners, but not always providing the very best parts for the job in the larger burner sizes, or always at a modest price for a particular SST.

Note: “Sufficient to heat” means that it can raise a properly built forge interior of those cubic inches to welding heat, or pour in an equal size casting furnace. Are these figures legitimate? In fact, they are under stated; not over reaching. What about the optional second (larger) flame retention nozzles on fan-induced (impeller blades) burners? Whatever inside diameter is used with one of them, with the gas pressure turned up to match the fan running at full speed, can be considered as producing a flame equal to that nozzle size in a naturally aspirated burner. You can more than match the maximum output on the next larger size naturally aspirated burner.

    The number of cubic inches that can be brought to welding temperature in a properly built forge, or the number of cubic inches in a casting furnace that can b bronze casting temperatures (from a burner with a neutral flame), depends on the inside diameter of its flame retention nozzle; this is limited by the diameter of a burner’s mixing tube, in naturally aspirated burners, but nozzle diameters on fan-induced burners must be larger, when the fan is running at full power, and the fuel gas is increased to match its increased air induction, so the amount of cubic inches a fan-induced burner will sufficiently heat depends on the internal diameter of its flame retention nozzle; not on its mixing tube diameter.

Small stainless steel tube is the simplest choice to work with for any tubing part (although schedule #40 stainless steel pipe nipples purchased online might be cheaper); and stainless steel is the choice that is demanded for at least the outer tube of a burner’s slide-over stepped flame retention nozzle. Online prices are set by the desire for profit, and regulated only by competition from other profiteers. Therefore, you might as well end up with stainless steel parts, because you will a premium price, whether you choose a premium part or not.

    Thicker stainless steel millimeter tubing (2mm or more), needed for flame retention nozzle outer tubes, become pricy in 14mm sizes and up. So, you will find it cheaper to switch to stainless steel fractional tubing or pipe for such parts. When changing from millimeter to fractional tubing, you will be unlikely to match up a fractional outer tube with the nozzle’s spacer ring, and then the ring with the mixing tube for a sliding fit. So, it is good to know that up to a 1/8” gap between outer tube and spacer ring, is easily tolerated by the burner.  You can make the parts fit by slitting the spacer ring, and only drilling the outer tube for socket set screws. Under sized rings can be sprung open, and over sized rings can be compressed to fit into the outer tube.

Mixing tube lengths of naturally aspirated high-speed burners should be nine times the inside diameter of the tube. Mixing tube lengths of fan-induced burners should be fourteen times the inside diameter of the tube, unless internal fins are placed within the mixing tube’s end, to stop mixture swirl. These lengths are rules-of-thumb, for best overall performance; they can be adjusted to suite performance in particular circumstances. If a burner of either kind is primarily used as a hand torch, lengthening the mixing tube will provide a smoother flame for silver brazing. Shortening the tube will make harder shorter flames to help use up oxygen before the flame can impinge on parts that are being heated in a forge. Lengthen a mixing tube no more than twenty percent, and slowly cut it back, while observing the flame, for best results. Shorten mixing tubes less than ten percent of length, and shorten further while watching the flame, for best results.

Note: “Sufficient to heat” means that it can raise a properly built forge interior of those cubic inches to welding heat, or pour in an equal size casting furnace. Are these figures legitimate? In fact, they are under stated; not over reaching. What about the optional second (larger) flame retention nozzles on fan-induced (impeller blades) burners? Whatever inside diameter is used with one of them, with the gas pressure turned up to match the fan running at full speed, can be considered as producing a flame equal to that nozzle size in a naturally aspirated burner. You can more than match the maximum output on the next larger size naturally aspirated burner.

    The number of cubic inches that can be brought to welding temperature in a properly built forge, or the number of cubic inches in a casting furnace that can b bronze casting temperatures (from a burner with a neutral flame), depends on the inside diameter of its flame retention nozzle; this is limited by the diameter of a burner’s mixing tube, in naturally aspirated burners, but nozzle diameters on fan-induced burners must be larger, when the fan is running at full power, and the fuel gas is increased to match its increased air induction, so the amount of cubic inches a fan-induced burner will sufficiently heat depends on the internal diameter of its flame retention nozzle; not on its mixing tube diameter.

                                                                                     Burner sizes

The first thing you must decide about your burner is what size it is going to be. Home-built burner sizes are given according to schedule #40 pipe sizes (or its equivalent inside diameters in round tubing) that is used as the burner’s mixing tube. These burners were built from fractional pipe for many years (and most 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 in a gas orifice diameter, and to whatever you use for a conical air entrance.

    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 pipe, so choose a little larger inside diameter, when possible (rather than a little smaller), for your burner’s mixing tube, or the flame retention nozzle’s spacer ring, and outer 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.

       Schedule #40 pipe dimensions:                    Metric

(A) 1/8” pipe is 0.405” O.D. x 0.270” I.D.      10x8mm (0.390” O.D. x 0.312” I.D.) tube. The burner’s nozzle size is 0.493” I.D; this is sufficient to heat 22 cubic inches on naturally aspirated burners.                                                  

(B) 1/4” pipe is 0.540” O.D. x 0.364” I.D.      12x10mm (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.

(C) 3/8” pipe is 0.675” O.D. x 0.493” I.D.       14x12mm (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.

(D) 1/2” pipe is 0.840” O.D. x 0.622” I.D.     18x16mm 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.

(E) 3/4” pipe is 1.050” O.D. x 0.824” I.D.      20mm pipe nipples sand 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.                     

(F) 1” pipe is 1.315” O.D. x 1.049” I.D.          25mm pipe nipples and couplers are 0.975” The 1” burner’s nozzle is 1.61” I.D.; this is sufficient to heat 700 cubic inches on naturally aspirated burners.

Be advised that imported cast stainless steel pipe fittings are very likely to be metric; not fractional (Imperial), no matter what their online advertisements state.

I did, Frosty. And if they bring this back stuff five years from now, I'll speak out against it then, too. We don't need another "great debate" over nothing. Remember all the blah, blah, blah over fan blown versus naturally aspirated burners?

4 minutes ago, Mikey98118 said:

his back stuff five

That's what I get for getting hot about something

The Bauer 20v 3" cutoff tool (available from Harbor Freight Tools for $50 (but the battery is another $50); this is a burlier version of the 12V 3” angle grinders (whether they are called grinders or saws depends on their primary use; they can all be used for both tasks). You trade handiness on delicate tasks for increased power; This is one of the latest models of stronger 3” tools. DeWalt, Works, and other brands are also selling 20V 3” cordless saws.

    What then is the point of this particular tool? After all, there must be a point to it, if competing brands are proliferating, right? Not necessarily. Lots of power tools are popular for a while, but don’t last the test of time; I don’t think these will either. their point is supposed to be sufficient power to be considered a practical workman’s tool, but light and handy for cutting. While it is considered hard to make an angle grinder too powerful (a view I totally disagree with), it is easy to make a saw overpowered and unsafe; this is because of the danger of severe kickbacks from overpowered hand-held saws. But high torque hand-held saws have been used for over seventy years. Yes, for cutting wood--not steel. The difference is positioning. If you plunge cut steel with a chop-saw, it can be done safely. If you put a friction blade on a circular saw, you can only cut steel safely, so long as you keep its shoe (the flat rectangular metal base) flat upon the work surface. But surface cutting is done free hand; this tends to create kickback. During this kind of cutting, too much torque in your tool is likely to be paid for with your blood. 18V to 20V motor are as strong as you want to try, when surface cutting.

18V and 20V angle grinders can be a good choice for general cutting jobs on sheet metal, but not for making interior cuts for rectangular air openings in pipe and tubing; use 12V 3” angle grinders, or 15/16” discs in rotary tools for such delicate work. Cutting pipes, tubes, and angle to length, or cutting empty cylinders for equipment shells, is what these grinders are best at. So, why not use 120V angle grinders for these tasks? The race to market ever stronger grinders is the problem. 280-watts on a 3” cutoff disc, or 350-watts to spin a 4-1/2” cutoff disc should be the limit for safety. Obviously, a 7.5 amp angle grinder is complete overkill for surface cutting. Cordless grinders are about half the torque of 120V grinders. Furthermore, the latest 18V and 20V grinders feature speed control; allowing you to drop them down to two-thirds input, which is just about as close to perfect for cutting on sheet metal as you can get.

On 12/21/2023 at 5:33 PM, Mikey98118 said:

From mini 12V angle grinders to rotary tools

 

Going on with this discussion, I got a Phalanx 12V rotary tool for Christmas; its motor has lots of torque, and you can get replacement batteries for it for $20. All of these manufacturers insure that their tools will not accept a different OEM's battery, worse luck. But, at least they are available for this brand.

Kast-O-lite 30 Li is, for very good reasons, the most popular castable refractory on the market. Therefore, ALWAYS do a word search to find the best offers near you. One seller will be offering five-pounds of it for $45 while another seller offers five- pounds for $17. 78. Look before you leap, or pay sucker tax. This product is even sold at Home Depot.  Kast-O-lite 30 is a light weight, semi-insulating, high-alumina refractory that is resistant to cracking from thermal stress, and use rated to 3000°F; it is suitable for use as a primary flame face layer, and be cast in two layers with a secondary outer layer mixed with one third Perlite, to increase its insulation value. What if you live somewhere that forces you to pay high taxes and ridiculous shipping fees to import the refractory? Simply choose a local high-alumina castable refractory, and add silica or alumina bubbles (little hollow spheres) to suit. One kind of spheres or the other should be available from suppliers of cement; they are used to reduce weight in cement structures.

 

Zircar Ceramics’ Bubble Alumina (not to be confused with alumina bubbles) is an extremely low-density insulating castable refractory consisting, principally, of high-purity alumina spheres, in a high-purity alumina cement binder, which is use rated to 3317°F (1825°C). Obviously, this refractory constitutes the best possible insulation, needing only the thinnest of flame face covering over it.

    I would suggest Plistix 900 F for a flame facing, and also as the cement binder of alumina bubbles, if you wish to mix your own bubble alumina refractory; it is use rated to 3400°F  

If you must import Plistix 900 F, choose a local high-alumina refractory; these are commonly employed in glass working equipment.   

 

On 2/26/2021 at 2:21 PM, Mod30 said:

Some of my co workers like gloves.  I don't personally as I prefer a better grip.  

This can't be overemphasized. In thirty-eight years running angle grinders, I tried using gloves just one time, and still have the scar to remember how bad an idea that was.

                                                                                    Kiln shelves

Kiln shelves are mostly considered a topic of interest to potters, because they are normally found in electric kilns. What goes on in these kilns is that heavy loads of pottery are cured at high heats for several hours; which is why high-alumina kiln furniture, including shelves, are rated by cone numbers, rather than merely use rated by temperature. The bottom line is that these shelves are engineered for maximum resistance to slumping under loads at sustained high temperatures (up to 3000 °F)—not for insulation value, which for kiln shelves is considered counterproductive. In fact, high alumina kilns are the perennial favorites of small business users despite their simi-insulating status; not because of it. The most expensive kiln shelves are nitride bonded silicon carbide, because of their high loading capacity and low shelf weights, which are important factors in a pottery kiln. Both carbon and silicon transmit heat well, but that is a plus factor—In a pottery kiln; not in a blacksmith forge or casting furnace. Fast heat transfer, combined with a maximum use temperature of 2600 °F degrees make silicon carbide a poor choice.

    Mullite kiln shelves are made by fusing magnesium and silicon together; a use temperature of 2900 °F degrees compares well with high alumina shelves; it is noted for thermal shock resistance, but high alumina shelves or very good at that also. Mullite is a poor insulator, and not as strong as high alumina, but the product is an acceptable alternative to shipping costs, if high alumina isn’t locally available.

    Half-bricks (1” thick hard fire bricks) are only acceptable for whose who’s common sense is blinded by parsimony. High-alumina kiln shelves are seven times more insulating than clay firebricks, and far tougher under loads.

    A floor made of semi-insulating high alumina refractory, over ceramic fiber insulation, is an acceptable substitute for a high alumina kiln shelf, and perhaps even more advisable if you want your floor shaped; but it is nowhere near as strong as a high-alumina kiln shelf, and therefore not removable for power brushing spilled flux from. As is often the case, once you have a look at the facts, choosing between viable alternatives can be tough. You only need to leave a little extra width in slots built into a cylinder’s front exhaust opening for the kiln shelf to rest in, and it can be slide in and out over the insulation without worry. If you want to weld in your forge, choose a kiln shelf floor; if not, choose Kast-O-lite 30 for your floor. If you like spending money on fuel, choose a half-brick.

                                                                    Fiber blanket needs rigidizer

Even the cheapest grade ceramic fiber blanket does not melt below 3200 °F. Product temperature ratings come from the level of heat that fiber products will withstand without massive shrinkage; this should illustrate the importance of locking the individual fibers in more secure positions by rigidizing; it also demystifies the seemingly magic protection conferred by a relatively thin coat of heat reflector, such as ITC-100. Ceramic fiber products need both rigidizer and finish coatings to do well in today's gas forge; this is because better burner designs and smarter forge designs create much higher internal temperatures than were common in the past.  

    Rigidizer is especially important, because if you want your insulation to last it must be prevented as much as possible from shrinking. On the other hand, between employing 2600 °F rated ceramic fiber insulation and rigidizer, you can toughen the secondary insulation layer in your forge or furnace enough so that it should stand up well to the heat that will leak past the high emission coating (AKA IR reflector) and thin hot-face layer (typically Kast-O-lite 30. Rigidizer also helps support thin seal coatings. There are products like Plistix touted as heat mirrors which make very nice surfaces on which to paint even more effective high-emission coatings.

    You do not want to use thick fiber insulation layers, which tend to ripple when placed inside of curved surfaces; instead of a single 2" thick layer of ceramic fiber, place the blanket in two 1" thick layers. Ceramic fiber blanket will easily part into thinner layers via delamination between layers. Rigidize each layer after installation, and heat cure it, before installing the next layer. Finish forming burner openings before rigidizing each layer. remember to leave them just a little oversize so that they allow the burners to be moved without suffering damage.

    Rigidizer is colloidal silica (just fumed silica, which suspended in water) and common everyday food coloring (to allow you to visually judge how far it has penetrated); this product is easiest to dispense by spritzing after you mix up your own. But you can always pay through the nose for it, already mixed with water, from a pottery supply. I bought my fumed silica powder through eBay and got free shipping, because its weight is negligible.

    Ceramic fiber products are so porous that water runs right through them, unlike solid refractory, which must be slowly dried out, and then gently heat cured to prevent damage from a buildup of steam pressure. So, ceramic fiber can be "cured as you go," which means that nothing prevents you from slowly rotating a layer of blanket on a curved surface, like a casting furnace or tube forge, spritzing the rigidizer unto each area that is laid flat by the weight of the liquid, using your burner (turned down low and constantly moving over the wet fiber), to stiffen the blanket into permanent shape, and then moving on to the next area at your convenience. After creating a smooth stiff surface inside the structure, you can install another layer over it, the same way.

    One of the joys about completely soaking the blanket through is that both layers will bond together. Any excess rigidizer that soaks into the first layer will run right over its fiber’s surfaces by capillary action, the same as it did the first time, causing no clumping to degrade the insulating value of the outer fiber layer.

    The whole process is nearly goofproof. But, it’s still possible for a complete idiot to burn himself with the escaping steam that will be created, during firing. If you turn a high-speed burner on at maximum while holding still over one spot, it is conceivable (but quite unlikely) that you could even melt a patch of fiber.

    What keeps Murphy’s Law from messing up your efforts? First, the fiber is partly alumina, and partly silica; the aluminum oxide pretty much prevents it from melting, while the silicon oxide content bonds beautifully to the colloidal silica in the rigidizer. Secondly, the individual fibers in the blanket are very thin, which maximizes capillary action of a liquid across their surfaces. During heat curing, the colloidal silica that has wet every bit of fiber becomes a permanent vitreous outer layer on them, which creates welded joints everywhere the fibers cross each other. This glass sheathing is permanent. More rigidizer applied over it simply adds another layer after the next heat. Glass (silicon) is heavy, yet a quart jar of foamed silica (the which forms colloidal silica in water) is so light that it is obvious that the plastic container is heavier than all its content; this is because colloidal silica particles are so small that the main ingredient in the jar is air. Their tiny size is also why the powder will melt unto the ceramic fiber surfaces, this one time, at red heat. Afterward it remains solid at yellow heat. Consequently, every layer of silica sheathing on the ceramic fiber remains so thin as to leave the insulating ability of the blanket unchanged, even after repeated applications.

Note: If you do not completely dry the rigidized blanket before coating the blanket layers with sealant, it can still create a steam pressure problem, damaging the final coating. So, drill a 1/8” hole in the bottom of the equipment’s steel shell, as a pressure valve, and seep hole.

 

You can buy colloidal silica rigidizer at some pottery supply stores, but being mostly water, it is not cheap to ship from online sources; in that case you are better off to mix your own. Commercial solutions usually contain about 1100 grams of colloidal grade silica per liter of water. A liter is just over one quart (just under 34 ounces), if you want to use a kitchen measuring cup. One easily found and economical source of colloidal grade silica is fumed silica, which can be purchased from eBay, Amazon.com, and many other suppliers.

    Unlike sodium silicate, this product must be fired to take a permanent set on the ceramic fibers. Never allow this or any other colloidal solution to freeze, or it will clump together, and be ruined. On the other hand, measuring amounts is not needed. Commercial solutions commonly contain thirty percent fumed silica in solution with water. If you make your solution too thick to spritz, just add water. Too weak? Add more fumed silica. Hard to determine how well it is penetrating the ceramic blanket? Add food coloring.

Maybe a stronger solvent then alcohol?

Also, it would take a very small orifice to be too small for most torch tip cleaners, which are made for oxyacetylene torches (smaller holes than other fuels) On the other hand, oxy-natural gas torches, which were once common, have very large holes. These tips were still around twenty years back in my neck of the woods.

Good job covering all possibilities, Buzzkill. But answer number three gets my vote. As for the problem coming and going, that sounds pretty standard with a build up of wax and tar in the gas orifice. I predict that the burner will shut down completely a little further on. Sounds like he needs to poke a wire into the orifice, to see if a tar ball falls out. This is what torch tip cleaners, which are available from a local welding supplies store for a couple of bucks, is used for.