Burners 101

[Mikey98118]

If you're going to go through all the trouble to build a top-flight burner, why not construct it from stainless-steel? Because greed has pushed stainless prices into the stratosphere; that's why!

So, after giving up on my regular steel supplier of the last thirty years, I have been reduced to buying stainless-steel pipe nipples and fittings through Amazon.com. If you're willing to translate back and forth from inches to metric, S.S. tubing can be had at reasonable prices in the small diameters used in 1/2" and smaller burners. But, at 3/4" sizes and greater, forget it.

So, I was happy to find that eBay still has S.S. prices that most of us can afford.

[Greg in Maryland]

18 hours ago, Mikey98118 said:

By the way, Greg; you do have a regulator and needle valve on that burner's gas line, right?

There is an appropriate regulator and ball valve.  No needle valve.

Sequence:  1.5 inch overhang with .060 movements to lengthen the overhang.

[Mikey98118]

3 hours ago, Greg in Maryland said:

here is an appropriate regulator and ball valve.  No needle valve.

Uh-oh; If you have a ball valve near the burner end of your gas line, please take it off! Ball valves make excellent shutoff valves, but they can create havoc when placed next to a burner. you are much better off with only the regulator, than with a ball valve and regulator

On the other hand, that ball valve is an excellent quick shutoff device, when placed next to the gas cylinder; which place is it?

[Greg in Maryland]

The ball valve is at the burner end of the line.  I will take it out to see what happens.

[Mikey98118]

6 hours ago, Greg in Maryland said:

1.5 inch overhang with .060 movements to lengthen the overhang.

The flame is best at 1.5 inches of overhang, which is reassuring

[Mikey98118]

On 3/16/2023 at 7:14 PM, Mikey98118 said:

So, after giving up on my regular steel supplier of the last thirty years, I have been reduced to buying stainless-steel pipe nipples and fittings through Amazon.com. If you're willing to translate back and forth from inches to metric, S.S. tubing can be had at reasonable prices in the small diameters used in 1/2" and smaller burners. But, at 3/4" sizes and greater, forget it.

So, I was happy to find that eBay still has S.S. prices that most of us can afford.

Okay, you can buy 3/4" x 12" S.S. nipples through Amazon.com for about $16, and you can buy S.S. female couplings for around $5 to screw on the burner's front end, as a spacer ring; they are cut in half, so that further reduces their price, if you are building a pair of burners. The nipple's other end mounts brass hex reducers and hex caps. Those brass caps can be easily drilled out to just over the outside diameter of 1/8" #80 pipe nipples (to be drilled and threaded with a 1/4-27 tap for the MIG tip). The hex reducer is easily drilled in place on the pipe nipple for three equally spaced set screws (to keep the gas tube axially true to the burner body). Using these parts reduces your pipe cutting in half. The pipes are seamless cast products. So far so good, right? The fly in your ointment is that these are imported products, which vary from standard pipe dimensions; this is no problem...until it is. While all of these parts are high quality, and fit perfectly together, the outside dimension of the coupling is not standard. Instead of 1-3/8" outside diameter mine turned out to be 1.196". If you have digital calipers to check your coupling's diameter with, before ordering a short length of S.S. tubing of the right internal diameter, that will work out just fine. If you count on American S.S. to make a good match with it, not so much.

Here's the fun part: The 3/4" pipe nipple was also a little undersized at 1.060".; his is about 1/16" undersized, so standard 1" pipe will slip right over it, when you use it to make a sliding choke for the air openings

[Mikey98118]

23 hours ago, Mikey98118 said:

so standard 1" pipe will slip right over it

Typo alert! that should have read "... so standard 1-1/4" pipe will slip right over it."

[Mikey98118]

So, this means that standard pipe is going to be a little large, and ditto for tubing. What to do? A small gap of around 1/16" between the flame retention nozzle's spacer ring and its outer tube doesn't effect performance one bit. So, two rows of three each equally space socket set screws  through the outer tube and spacer ring can be used to keep the flame retention nozzle centered and axially true on the mixing tube.

[Mikey98118]

While I try for close fits between the spacer ring and mixing tube, and ring to outer tube, of flame retention nozzles; this is done just for the sake of simplicity in keeping the nozzle centered and axially true on the mixing tube.

In 2006 I did several experiments with oversize nozzles, with up to 1/2" excess internal diameters; and found that they stabilized themselves, right up to the paint that the flame snuffed out. I never discussed them, because safety concerns overrode their possible advantages, at that time. But with increased problems in obtaining stainless-steel tubes at reasonable prices, it becomes relevant to people trying to build flame retention nozzles from odd sources, such as stainless steel dental casting casks, etc.

Also, fan-induced vortex burners use two different size flame retention nozzles, so a little leeway in fit-up of the larger nozzle should be appreciated.

[Mikey98118]

Note that this is not the same thing as an oversize nozzle shape with a thick spacer ring filling up the air gap; that gap will modify air flow into the nozzle; an oversize nozzle (built from a pipe reducer fitting, for instance) will not do so, and therefore your resultant flame won't be the same. Well, what about a sealed burner running in a forge? That can't induce air flow through the gap. But then, such a burner isn't running out in ambient air, either; back pressure in the forge stabilizes any burner's performance.

[Mikey98118]

On 3/17/2023 at 6:46 PM, Greg in Maryland said:

The ball valve is at the burner end of the line.  I will take it out to see what happens.

What happened? Inquiring minds are dying to know

[Mikey98118]

As to needle valves; they are just a luxury item, since the same job can be handled with the regulator. I like to use a needle valve at the burner, so that I can fine tune without turning away from the action

[Greg in Maryland]

No progress on removing the ball valve.  Will try something this week.

[Mikey98118]

So, since they came up as a potential problem, why did I point out that ball valves placed between the end of the gas hose, and the burner's gas tube can create trouble? Only because they have come up as creating problems a couple of times in the past, when placed that way.

However, it should be noted that their burner hoses didn't have a variable pressure regulator between the gas cylinder and the burner. But your gas hose does. The difference is that cylinder pressure can hit 150 PSI, so the ball valve can be trying to control a flow from 0-150. With the regulator mounted, that flow drops down to 0-30 PSI. So, the problems should greatly decrease.

But, your problems are minor; not major, so the ball valve still looks likely to be the culprit.

[Frosty]

The reasons I always recommend the 1/4 turn ball valve be placed on the regulator's outlet side rather than the burner is. The valve shuts off pressure to the entire circuit after the regulator. Closing the valve at the burner means the hose and fittings are under pressure from valve to tank so any leaks will be venting and a fire hazard.

Also having the shut off valve at the tank means that in a broken fitting, cut hose fire type emergency you can shut the gas off quickly from as far from the flames as possible. If you place the valve in the right position you can close it with a thrown glove.

Frosty The Lucky.

[Mikey98118]

All good points, Frosty.

[Greg in Maryland]

On 3/16/2023 at 1:07 PM, Mikey98118 said:

I would be having fun, if this were my own burner, but more care must be taken with other people's toys

I got curious and put the burner in the forge (.023 tip).  It seemed to be burn well with very little flame leaving the forge.   All your help paid off.  You could really see the adjustability of the choke to flame performance.
Observation:  it took an hour to get to 2000 degrees F @ 30psi.  The forge would get to 2200 in 30 minutes with the .035 tip but would be spitting flame out of the door.

Question:  Would the burner increase heat output if the air openings were widened and a larger tip (.025 or 030) installed?

[Frosty]

A 0.035 orifice delivers more than 2x what a 0.023 does per given pressure. So, sure if it's tuned to a neutral burn the 0.035 will be making more than 2x the heat. 

30 psi through a 0.023 jet? Sounds to me like it's blowing heat right through the forge whether there is dragon's breath or not. 

I never run higher than 12psi except through the NARB but it'll weld at 12-15psi easily and I only turn it up that high to keep the burner block cool so it doesn't burn back.

Frosty The Lucky.

[Mikey98118]

I agree With Frosty, that 30 PSI to reach full temperature in a forge is just too much pressure. When designing burners, I wasn't satisfied with anything less than proper performance at 50 PSI; this was a safety issue, only. If your forge and burner won't reach welding heat with a 0-20 PSI regulator, it is time to rethink, the forge, its burner(s) or both.

I am willing to go right on to rethinking your forge, if that is what you desire. First, I would like you to ask yourself if you are actually satisfied with your burner's performance, or if you're just tired of the hassle, and feeling impatient "to get on with the job." Either way is fine with me, because either way can be revisited later...should you have regrets. This is the beauty of building your own tools; control 

16 hours ago, Greg in Maryland said:

Question:  Would the burner increase heat output if the air openings were widened and a larger tip (.025 or 030) installed?

I always found 0.023" MIG tips to be a little too small in a 3/4" burner and, (at least in Mikey burners) 0.030" tips a little too large. Thus, when  0.023" MIG tips became available it was a joy.

That should have read "Thus, when  0.025" MIG tips became available it was a joy."

However, you have a modified Hybrid burner; it might handle an  0.030" MIG tip, okay.

[Mikey98118]

I think that one of the trickiest things for people to wrap their heads around, is the adjustments in the rules, that become possible, and sometimes necessary, once changes in the burner's design changes the speed and volume of its mixture flow. Everything depends on air induction; gas pressure ranges, and orifice size, needs to match up well with how much air induction a burner's design permits.

[Mikey98118]

Finally, you should spend a little time reading through Another Frankenburner's 3D printer burner pages.

Why? Because, the modifications you made on your burner could very well edge it into the category of Naturally Aspirated Vortex Burner. One of the things that changes, is that the size of your burner's flame nozzle becomes more flexible than that of a Mikey burner's; this means that you can very likely get more out of that burner, than the limits I set down for Mikey burners. However, Another Frankenburner can do as well as I can, to help you navigate the new waters of such burners; a second viewpoint is always a good thing, and since your burner now lands somewhere between his design, and my new vortex burners, you should mine as much savvy as you can from both sources

[Greg in Maryland]

21 hours ago, Frosty said:

Frosty The Lucky.

Thank you for the feedback.  I put the .030 tip in and got to welding heat with 12-15 psi.  I lost track of time but guess it took about 45 minutes.  I think the burner will do better with more air (widening the air slots).

8 hours ago, Mikey98118 said:

I am willing to go right on to rethinking your forge, if that is what you desire. First, I would like you to ask yourself if you are actually satisfied with your burner's performance, or if you're just tired of the hassle, and feeling impatient "to get on with the job.

Mike - appreciate the continued help.  I know the final solution is a newly designed forge and burners.  However I am going to play with the hybrid burner for a little while longer.  I am going to widen the air slots to accommodate the .030 tip.  What’s the worst that can happen 

[Mikey98118]

15 hours ago, Greg in Maryland said:

 I am going to widen the air slots to accommodate the .030 tip.  What’s the worst that can happen 

So long as you leave enough width in the ribs between the burner's air lots, nothing major will go wrong. One thing that happens as burner slots widen is that the burner may not run as smoothly as before; its similar to mounting an over size engine in a small car; hot-rods are not family sedans. However, once mounted in your forge, even a hot-rod will smooth out. Back-pressure isn't always a bad thing.

So, why bring this up at all? When used as burners, there is no good reason to. However, when used as hand torches, for brazing work, a smooth flame becomes important. As we write back and forth, I try to remember all those other readers, who may have different agendas 

[Greg in Maryland]

The burner has 4 air slots that are 5/8 wide.  The ribs are approximately 9/16 wide.

I induced a light steam of air into the air slot while running the burner and it clearly reduced the unburnt fuel leaving the forge.  The temperature was holding steady before inducing the air.  The additional air started raising the temperature.  

How wide would you make the air slots for a first pass.  Also - would it be ok to widen only one instead of all 4? It would be more convenient to machine only 1.

[Mikey98118]

If the ribs are 9/16" wide, they can be thinned down to 3/8" without becoming weak; this will give you a collective air intake increase of 1/2" total. This would be the safe and sane move. I would recommend that you start with this, to see if the results are satisfactory.

If, they are not...or if you just get greedy, a further (mad scientist) move, would be to supplement this increase, by grinding the openings  longitudinal edges int bevels, and grinding the outside of each opening's other side, for for say 1-1/4" of their forward areas. So incoming air slides past a knife edge at its outer face, and its inner face slides past a knife edge too. Why only 1-1/4" their forward areas? Inducted air amounts will reduce on a gradient, from the most near the air opening's forward ends, down to the least at their rearward ends. So, past the forward most parts, you lose more rib strength than the increased air intake justifies.

It is always a temptation to sacrifice too much rib strength in the search for increased air induction; this never turns out well, which is half the reason why I reduced the number of air openings down to three. The other reason was to increase spin in the incoming air. I know that this doesn't speak to your needs, at this point, but there are others who plan to build their burners from scratch who will also read these words.