Furnace experts??? Burning in burner tube

I have a Lenox furnace that has been cleaned and inspected this fall by a heating contractor. The furnace has 4 burners. One burner tube was making rumbling noise and the flame was larger. Upon further inspection we found that the gas was actually burning inside the tube an inch or two back from the orifice. Found a small hole and crack which the technician said to have welded up. He assumed that would fix it. After welding the hole up the burner tube still burns back into the tube. Burners are made from sheet metal formed and spot welded. Burners are not corroded or worn out. I did find a place where three spot welds have failed and the sheet metal is wider where the gas comes through. I have included a picture. Gap is on the lower right side of the burner tube. Could this wide place be allowing the flame to jump into the tube itself? If so I will just pull it back together and put some spot welds on it. Thanks.

I have never heard of field welding a burner.

X 2. When I was in the business that repair could potentially burn your house down. Burning back can be wrong pressure,orifice and other conditions , maybe even a cracked heat exchanger that when the blower comes on it pushes the gas back into the burner.From the looks of the rust the furnace should be replace or get new burners at the minimum after checking the heat exchanger. Might want a different company look at it.

Burning inside the burner can be caused from low gas pressure.

But since only one persists in doing it, I would look for a problem with that jet. Could be something partially blocking it, the hole is drilled small or damaged. Try disassembling the gas manifold and cleaning it. Note the position of each jet, try switching the jets around, see if the problem follows the jet.

Try switching the position of the burner, see if the problem follows the burner.

When the burner tube that was burning back inside was found it was switched from the right side of the furnace to the left side of the furnace to confirm that it was the burner. The problem followed with the switch. The orifices were not moved. Actually the burners are not rusty or corroded. All of the orifices were cleaned by the furnace professional and the gas pressure down stream of the gas valve was checked and verified correct. The background in the picture with the burner is a marble counter top if that is what you are confusing for corrosion. After researching the internet one common problem that can cause burn back into the burner tube is to big of a gap where the gas comes out. The sheet metal type burners are more prone to this over a cast iron burner. Where the three spot welds are broken the gap is probably double. The gap being on the end of burner tube near the orifice probably compounds the problem. I will push that metal back together to specification and tack it tight with the wire welder. Thanks.

"common problem that can cause burn back into the burner tube is too big of a gap where the gas comes out"

YES, exactly, you have it figured out.

"Miner's safety lamps" of old worked on the same principle.

The flame on one side of a screen or perforated metal tube couldn't pass through the small holes to light the flammable or explosive mixture on the other side.

The metal acts as a heat sink and keeps the heat of the flame on one side from passing through and lighting the "gas" on the other side.

"Sir Humphry Davy successfully tested his prototype safe lamp at Hebburn colliery, Tyne and Wear, in early January 1816.

Davy found that flame could not pass through the small apertures in fine gauze meaning the flame inside the gauze would not ignite the gas in the atmosphere outside the lamp. Davy was one of the most celebrated scientists of his day and his discovery, based on scientific principles, became the foundation for most flame-safety lamps that followed."

Here's a link to ONE "read" on the subject...
Gs furnace burner tubes operate on the same principle

Don't think I would call your guy a furnace professional. You don't weld up furnace parts. Sure you can, even a heat exchanger can be welded but it just isn't done. A professional would have ordered a new one.

GET SOMEBODY THAT KNOWS FURNACES,otherwise you might be examining your insurance policy. Not trying to be rude or mean but thats why replacement parts are made.
If that furnace guy was good he would condemmed it till he put new burner in. Sorry but thats the fact

I think welding on a burner tube makes as much sense as welding a compressor tank. It might work initially until it causes bigger problems. I would start by replacing that part.

Oh you guys are just a bunch of worry warts. Nothing bad is going to happen because he's a good person with good intentions!

Aren't you the same guys who complain about "parts changers?" Nobody fixes anything anymore? Well, he's FIXING it, not just changing parts!

I had that problem with a gas furnace converted to propane. I reworked it several times after third attempt by "professional" to fix it. Nothing I could do was effective. That and starting up with a BANG when fuel ignited. Nothing I tried solved that problem either. We're happy with our new 96% furnace, and fuel usage is down.

The lp heater in our hunting shack has been burning in the venturi off & on for 40 years or more. It has cast iron burners which have been cleaned often. It is getting worse to the point my son thinks we should get a different heater. Now I wonder if a piece of screen would help?

Read everyone's replays. I work with both nat. and LP gas on commercial cooking equipment. Goes from a little range top to ovens the size of a mini van. I am guessing you have LP gas??. That LP gas is almost twice as heavy as natural gas and it actually flows like a liquid along the ground when cold. In ALL of the burner systems I have worked on never- ever- ever have tried to fix a burner. Something tells me you are talking about a plentum or heat exchanger? Buy a NEW furnace!!! Those 96% units are great. I have one on natural gas. Clean the filters and change the batteries in the Tstat. Natural gas is the same specific gravity as air and mixes well. Like I said LP is almost twice as heavy and doesn't like to redally mix with air. Something sounds so FISHY with your guys repair. I would get someone else to come in. Going back to LP. The burners have air shutters on them and for LP they need to be almost wide open as where natural gas they are a little more than 1/3 open. LP has a lot more BTU.content than nat. gas but it is also fussyer. Also for giggles take a look on the builders plate. See if the original build was for nat. Or lp gas. You could have the wrong orifice jets and that can mess up ignition too. Your description sounds like not enough air flow into the burner. There are just so many little tweaks with this equipment. Get another guy to look . This is just one of the certifications you need to work on commercial equipment and they pound it into you about messing with LP.

Going even deeper into this. Another problem he might be having. Poor exhaust draft and he can be getting floating flames or partial combustion. That is why I said that there are just so many "tweeks" in this stuff. This guy should add maybe an extension on his chimney. Even a couple of feet can do the trick. The top of a chimney should be at least three or four feet above the peak of your roof. A good service tech can take five or six years to get component. Here are two of the tools that you must have. By the way that drill set works Fantastic when doing carb work. Not a cheap set either. List is $200.oo and Ebay they are around 120 if you find a deal. Found the yellow jacket at a flea market for 8 bucks. Guy had no clue what it was for.

Your little story is the same reason Eagle safety cans have that bronze screen in the fill neck. The screen cools the flame front and stops combustion. Even those good old WWII Blitz cans had screens in the end of those goose neck fillers. They do act as a filter screen but that is NOT what they are originally there for. The principal of those safety lamps is mind boggling the first time you see one.

Barney .....your statement should read .... "He THINKS he's fixing it" ...... big difference !!!

Lenox Furnaces have warrantys If it is ~10 years old, it may be out of warranty. If not replace it. Welding up the burner is like welding a brake caliper. Nope. Jim