I'm finding that my burner requires me to turn up the pressure more and more as the forge gets hotter....is this normal? If I don't, the flame jumps back to inside the burner body (it's a basic pipe fitting burner with a mig tip jet)... Any input or comments would be appreciated.

Good Morning,

Probably your Propane Tank is starting to freeze up. Get a large metal pail/bucket, fill about halfway with water (or less), put Propane Tank in the water.

The water will act as a heat sink and slow down the freezing. The other cure is to join 2 Propane Tanks together by using a T-fitting. The freezing is a function of the amount of draw on the surface of the liquid Propane. Using 2 Tanks means cutting the draw on each tank in half. Less draw = less freezing.

Talk to others in your area. I know John Newman is in Hamilton. There are quite a few members of the Ontario Artist Blacksmith Association in your area.

Neil

If your tank is freezing up, then it is too small for the forge and the amount of heat you are using. Solution = get a larger tank.

This is probably just physics/chemistry at work.

In your burner tube, the gas/air mixture needs to be moving towards the forge faster than the flame-front moves through the mixture in the opposite direction.

As things get hotter, the speed of the flame-front increases.

In effect, it is normal. However, most people will get the pressure to where they know everything works pretty quickly and stay ahead of the problem.

One of the balances that needs to be found when sizing a burner is whether you can get the mixture speed up to where it needs to be in normal operation at a realistic heat input. If, to keep the burn where it should be, you have to run at a higher gas flow than you really need to run at to do the job you want to do, your burner is too big. 

Thank you, all...had forgotten about the notion of the tank freezing up....it starts after about 45 minutes of forging, so this could very well be the issue.

tim, you're comments were similar to my thoughts, that the back pressure from the hotter internal air would require more pressure, but it's topping out at 15 psi, and becoming more gas pressure than the Venturi effect can pull through the side burner.  I will try a couple of different burner sizes and see what happens.

 

There is a phenomenon called resistance to mass transfer .  Basically as the forge gets hotter the motion of the gases is more chaotic so more velocity is required to achieve the same flow. More resistance from the forge causes you to need more pressure on the gas from the jet.     .

Also check the alignment of the orifice, it could be a bit off and not a problem when cold but as mentioned when hot things can be a bit more touchy.

Absolutely thom, still trying to find a better way to deal with the wiggle factor...

Hey guys, I have a similar problem with my forge.I have a forced air burner, It was working perfectly for a couple hours of work with no problems,then one day it just started spitting and sputtering after 20 minutes or so.I have tried full bottle,changing air flow rates,higher gas pressure and it doesn't change much. I don't know what changed I haven't done anything different and I'm stumped. I should also mention that I am very new to forging iron but am loving it but I am sorely less educated about the science of burners, metals ets than you guys . I appreciate all of the knowledge on this forum,Thanks

Go have that guy right over there who lives near you take a look at it.  He can probably solve your problem in 5 minutes!

Welcome aboard David glad to have you. What Thomas is saying in his oh so diplomatic manner is you need to put your general location in the header there may be Iforge members close enough to visit and they may know exactly what's going wrong.

Anyway, there's a factor to  hot forge sputter I haven't seen mentioned. How far into the forge is your burner? If it's too far  the burner itself will get hot enough to pre-ignite the fuel air regardless how fast it's moving. There's also the intense IR radiation a reverberatory forge is designed to produce. IR radiation travels in a straight line so it can and will affect the fuel air in the tube so if the tube is getting hot too it can become a problem.

IR radiation is another good reason to NOT aim the burner perpendicular to an opposing forge wall.

After all that, if the burner is inserted more than say 1/2" into the liner you might try pulling it back.

Frosty The Lucky.

What do you mean my so dipsomaniac  manor?   Oh never mind,,,

Would you like me to make up a definition? I can get started as soon as I finish my meatloaf sandwich. Meatloaf sandwiches mmmmmmmm.

Frosty The Lucky.

That must be one heck of a sandwich lol. 4 hours later . My forge will sputter sometimes also and I'm not 100percent sure of this but I think when my building door is open the wind blowing causes mine to do weird crap. Am I imagining this? And also frosty how important is it to have a choke plate on a natural aspirated burner . I don't have one. Just figured I'd ask