Burners 101

[twigg]

7 hours ago, Mikey98118 said:

Like most of my generation, I totally rejected various new math, or new anything else that "those stinking teachers"  tried to fob off on students back in the sixties

I hear ya. Studying physics has forced all kinds of "new math" units on me (I remember hearing a joke where a physicist gives the age of their child in units of inverse electron-volts), but when I'm actually doing things in the real world I always find myself using imperial units. I just assumed that Marc meant millimeters because it made more sense. If the 0.001" lip was 20% then that'd make it a 0.005" mixing tube ID, and that sounds like crazy talk.

Deimos, I had a research internship in Innsbruck a few years back, and the folks running the machine shop there would grumble whenever I walked into the shop for that very reason. I think it was the lens tube attachment I asked them for with imperial threads that had to be single-pointed, that was probably what did it

The one nice thing about grad school is the software gravy train. Solidworks for $100/year! Now if only they'd give me the time to use it... Also, it's going to be rough when I finally get done with school and have to start over with a new package, but that's the whole marketing scheme

[Horseman1]

Hello everyone,

So I've completed my forge build and started my burners. One burner stays on with no issues but the other one has a flame back up into the mixing tube and sputters with small flames coming out of the air intakes.

I am running 2 1/2in burners at 4.5in apart, my interior dimensions are 4.5Hx4Wx13.5L, if my math is correct I'm at 243cu. My burners are both dropped into the forge at roughly 3/16in.

I've tried increasing and decreasing my fuel pressure from 5psi up to 10 and back down to 3psi. The sputter at 10psi is much faster at this point with less flame out the intakes. The one burner continues burning just fine.

Any ideas on what is causing this?

Some pictures below.

[Buzzkill]

There are a few possibilities.  If it were me I'd start by trying to narrow down those possibilities.  First off I'd want to know if the problem was in the supply line(s) or in the burner itself.  To check for that you can swap the supply lines going to your two burners.  Change nothing else.  If the problem moves to the other burner then a big portion of the problem is in the supply line.  If the problem remains with the original malfunctioning burner then we can focus on the burner(s).

What you are describing is usually the result of either a restriction in the gas flow (supply line or in the burner) or poor alignment of the jet compared to the mixing tube.  It's also possible that back pressure from the functioning burner is interfering with the performance of the other one.  That can be determined by firing the burners one at a time to see if the problem persists.

A likely culprit is debris in the gas line, or in the mig tip, that is impeding gas flow.  A tiny piece of dirt, metal, teflon tape, etc. is all it takes.  Another potential culprit is a burr at the end of the mig tip which is causing the gas to disperse as it exits rather than form a stream.  A torch tip cleaner can be used to ensure the orifice is clear of burrs and debris.

[Horseman1]

Sounds simple enough. Thank you for your time in giving me these ideas to think about as I go through my trouble shooting process. I'll let you know how it goes.

 Thanks,

Phil

[Mikey98118]

What Buzzkill said to watch for was good and prudent general advice; I hope it works out to be the problem here. Unfortunately you did too good a job on those burners for me have much beleif that this is your problem. Shutting down the ''good" burner, and using the problem child will tell you if that is your problem, one way or the other.

It is quite usual for two burners, built as identically as we can manage to be unequal. In a high back pressure situation, the stronger burner will interfere with the weaker one. I think that this is your situation. Furthermore, you built the forge too good as well. You kept the distance prudently away from the ends. BUT... in doing so, probably too close together. You might get some relief by canting the burners toward the openings.

I fear that you will be dissatisfied with half measures, and will end up needing to build two smaller burners. Here's hoping I'm wrong.

 

[Horseman1]

I certainly hope you're wrong. I have looked over a few things that are/could be problematic. First one is a problem, and that is that I have a small fuel leak in the line that goes to the problem burner. Second is that my mig tips are both completely flat and could have burred edges. Third is that I may have some crud in the burner from when I put the burner into the forge it scraped the interior wall so could have some brick pieces in it.

I will be sorting this out later this evening and will get back to you all about what the issue was or if I figured it out at all.

 

[Frosty]

Sound advice Buzz. 

4.5" spacing with the ports on the Ts parallel rather than in line shouldn't be robbing each other's intake air but maybe. With a flat top it'd be simple to place a barrier between them to double check. 

That's for the next round of tests though. Follow Buzz's suggestions.

I don't understand all the fittings and . . . stuff on your propane supply line. How about a pic of that so we can see what's there. 

If you used teflon tape on all those joints there's probably pieces blocking your jet.  Use the paste sparingly instead, it can't tear and be blown down the line until it reaches the jet and jam. Big boogers of thread paste will cause problems so just a light wipe on the male threads ONLY and back a couple threads from the end.

Flat mig tips have no effect in a T burner, it's ONLY the inside of the oorifice where a bur will interfere. 

I doubt scraping brick, inserting the burner could leave residue in the burner. If pieces were large enough to jam it wouldn't burn at all, it'd just make plumes of yellow flames. 

What's holding all that propane supply up? I don't see a support structure and can't believe the copper tubing could support it. 

You really need to simplify things, there's no reason for all that stuff. 

Frosty The Lucky.

 

[Mikey98118]

I would be delighted to be wrong this time.

[Mikey98118]

BTW, your forge is getting so hot with only one burner, that you need to look into a heat reflective coating pretty soon.

[Horseman1]

 Well, here it goes.

I first repaired the leak. Turns out I forgot to put thread paste on that fitting, (I did use threat paste as I know teflon tape doesn't react well with propane). Still had the issue. Next I took the mig tip out and cleaned it out with the proper sized mig cleaning tool. Put it back together and it worked just fine.

Frosty, I realize that my setup is a bit unorthodox with the copper tubing and brass fittings and all that. I was doing the best I could with the supply that I have at hand. With 3 different hardware stores in close proximity to me I was unable to find the hard lines that I've seen so many people use. I currently don't have an official support for all of it, but the braided propane hose is stiff enough and the way it sits on the tank provides just enough support to take the stress off the copper lines. However, I do plan on improving this part of my design in the very near future.

I'm thinking I'll have to go to a plumbing supply place in a different area entirely to find what I need.

Check out the picture to see the burner in action and let me know what you think of its shape, color and if you think I need to do anything to make it neutral.

The top picture is of the problem burner after I got it going again.

The last picture is of all the plumbing.

[ThomasPowers]

Weld a piece of strap stock to the forge body that arcs over and supports the assembly at the upper T---you could forge a nice little Y on the end and roll the ends to hold the T.  Could even weld a slot to stick it into on the forge and so have it removable...

[Buzzkill]

Glad you got it running!  To me it looks like you still have some tweaks to do though.  It appears as though the flame is canted a bit as it enters the forge.  This could indicate either an alignment issue inside the burner or that the mixing tube is aimed so that the flame is impinging on one side of the burner port before it gets to the forge. 

You also appear to have multiple combustion envelopes in the flame.  You can probably still get a hot forge, but it's not ideal.   Mikey and Frosty are much better at analyzing flames, so hopefully they'll jump in and give their opinions.

[Mikey98118]

The flame isn't ideal,, but it is the rear flame. Once the openings are dealt with, this means that the secondary products (in this case including fuel that still needs combusting) will have the length of the forge, and the forward flame to be passed by, before exiting the forge. So, could the flame be improved? Sure; but does it need to be? He won't have a clear idea until the forge is finished. Maybe a definite yes, or maybe, not so much. Some things just end up as the convenience of the builder. Other things need to be addressed.

Chancing being wrong again, I'd still say not.

[Mikey98118]

Is this just a "sloppy" view of things? I prefer to always see perfect flames. How well this tool serves for blacksmithing is a different matter. Loads of people prefer a lightly reducing atmosphere in the forge, to keep scale formation down. So, as a practical issue it all comes down to how reducing. We must wait and see

[Frosty]

That flame doesn't look bad at all, deburring the orifice seems to be the solution to that problem. Now, pull the burners out of the forge chamber! They need to be as far OUT of the forge as possible, 1/4" past the inside of the shell is usually plenty.

The flame appears a little richer than I like but it's close enough you'll want to sneak up on the right length with sand paper, not a file nor saw. Remember to deburr the orifice every time before testing the results.

If you put the" close nipple, T, gage and valve ON THE REGULATOR, you can lose almost all the rest of the fittings hanging there. You'll need to reverse the direction of flow so the hose is already compatible. No need for more fittings to make it up. That is zero issue, none of these care which way the gas flows. Heck, you can PROBABLY lose that T completely if there's a plug on the regulator it's filling the gauge port, the gauge should go there.

The hose should make up directly to the brass T that makes your manifold, if not, use only ONE fitting to connect them. Take the T to the store with you so you don't have to guess. Propane hose fittings are standard size you can check one at the store and write it down. A REAL plumbing store will have bins of brass fittings. I've been to Ukiah I'm sure there are plumbing suppliers, check the HVAC section for suitable fittings.  

If you like the needle valves, no problem but you can remove the close nipples and elbows from the T and make them up directly. 

You can GENTLY bend the copper tubing right to the side of the forge to secure it and use a simple clamp to the table to hold the weight of the hose. 

One of the issues with having excess weight hanging off burners is it tends to knock the jets out of alignment and alignment is critical. 

It's looking good so far, you're down to trimming her sails so to speak.

Frosty The Lucky.

[Horseman1]

Awesome suggestions guys thank you! I'll be sure to come back to the forum once I've supported things.

[Mikey98118]

Nobody brought it up yet, but one of the best features about using soft refrigeration tubing, is the loops Frosty always uses in his; I think that eases a multitude of these kind of issues... just a thought.

[Horseman1]

That is a really good idea, I never thought of that. Thanks Mikey.

[Mikey98118]

On 3/11/2021 at 12:56 PM, Frosty said:

The flame appears a little richer than I like but it's close enough you'll want to sneak up on the right length with sand paper, not a file nor saw. Remember to deburr the orifice every time before testing the results.

It is interesting that you are using the same solution to tuning smaller burners that I am, considering how different the rate of flow in our burners is. I think that points to something important, but can't think what is must be.

[Horseman1]

So here's the forge after making some adjustments to the fuel lines adding a fuel line support. I felt comfortable enough at this point to add a coat of high temp engine paint.

Also included a picture of the burners running with the adjustment that Friday made mention of.

[Frosty]

2 hours ago, Mikey98118 said:

It is interesting that you are using the same solution to tuning smaller burners that I am, considering how different the rate of flow in our burners is. I think that points to something important, but can't think what is must be.

I liked your solution better than mine so I adopted it. I don't sand jets at home but it requires a higher level of shop skills to trim them in the drill press with a jewelers file. I actually have instrumentation I can put on the drill table and measure the change in 0.0001" increments. Dad gave me his instruments when he retired. You literally have to hold the file just SO or the bur will roll the orifice closed almost like crimping it. It looks like you used a pipe cutter on it. You have to brute force it open if you get it wrong. I know, I scrapped a few mig tips getting it right.

It's just too difficult to explain and I'm not going to do how to videos when there's a perfectly workable method that doesn't take explanation, only a LITTLE clarification occasionally. 

Anyway, that's how we came to be making the same recommendation to the public. I do my best to keep my ego on green pastures and not let it interfere with results. When someone comes up with a better way I'm all over it. Even YOU the loyal opposition. 

Frosty The Lucky.

[Mikey98118]

I think we came up with the same limitation with different tools. Namely that pure copper is a little too malleable at times.

Horseman1

This will probably sound weird, but your burner flame is no less reducing, but is nevertheless improved. How can that be? I can see the change, and recognize it as right next door finished.

[Horseman1]

What should I do then to improve the quality of flame?

[Mikey98118]

Frosty will have to answer that.

[Frosty]

Phil pulled the burners farther out of the chamber, the change in flame shape is the result of the burner port acting like a step nozzle. 

You did pull them back, right Phil? 

Now is time to start fine tuning the burners by trimming the mig tips a LITTLE at a time. A little sanding, debur with the tip file and test. I suggest you shut one burner off and tune them one at a time. 

I break the copper tubing off and unscrew the fitting WITH the mig tip in place. It's too  much hassle trying to remove the mig tip while the fitting is in the T and reinstalling it WILL damage the threads eventually, I usually cross threaded them by the 3rd. time. I used a piece of plastic tubing on a screw driver that fit reasonably tightly over the mig tip as an extractor tool I could feel to use but it didn't matter, I still hosed the threads.

Sorry for the stroll down memory lane but it's maybe useful back story and might save you trying something that doesn't work very well.

Removing the fitting is another reason I like thread paste, it makes a good lube so the threads last long enough to get it adjusted. 

Say Mike: Do you have a pic of a good flame you can include here for a reference? It'll save Phil time, if he has to ask our opinion every time he trims one he'll be at this way longer than necessary. 

Frosty The Lucky.