A question about heat/flame and melting lead

I picked up a homemade lead melter. Its nothing more than a 12" bit of pipe with a nice larger burner in it, hooked to a bit of pipe with
some corrigated steel welded to the top of it as a table.
In operation..the flame is blue for about 2" in hight, and above that its yellow and almost..almost sooty.
The top of the corregated steel, where the pot sits, is almost 3.5" above the burner..so I have almost 1.5" of yellow flame below the pot.
The pot is the same diameter as the melter..so there is little flame coming up and around, unless I crank the valve wide open. In any flow rate the flame is indeed touching the bottom of the pot. Hot enough to keep the corregated steel "top" a nice red color.
The question is...should the blue part of the flame be bearing on the bottom of the pot? All the heat is rising upwards and is striking the bottom of the melting pot..but am I losing much heat efficency this way?
In the past couple days Ive melted down about 250lbs of wheel weights and cast them into ingots with about 2 gallons of propane, so it is working well enough and melt time is only about 10 minutes from a cold start and 1/2" of lead sitting in the pot. I fire it up, fill the pot with wheel weights, go do something else, come back and flux a bit, then with a big spoon with holes drilled in it...seperate the clips that are floating on the top, mix a bit more than ladle into the ingot molds, refill with wheel weights and repeat.
The ingots will be used to fill my various 20lb electric bottom pour pots and be used for casting bullets during the cold winter evenings when the fog is thick <Grin>
The reason I ask, is that Im considering modifying this and replacing the melting pot with a nice big bull plug and a valve and spout so I dont have to use a ladle to fill my 1lb ingot molds and when I do, I can drop the bull plug down a bit into the blue flame.
Or is it simply guilding the lilly?
The current "melting pot" is nothing more than a nice heavy, thick walled aluminum "skillet" sort of thingy I had kicking around.
Curious about opinions on this. I gave $5 for it at a yard sale and I believe it was used to melt babbet in the oil patch. Had a good hose and regulator in my Stuff and dogrobbed the BBQ bottle off the BBQ.
I built one 25 yrs ago that ran on natural gas, hadbottom pour lead valve etc etc..a very good working unit and loaned it out..and the guy disappeared. As best as I can recall..the bottom of the bullplug was just about in the blue of the flame and it worked quite well for both casting bullets and keeping the shop warm.
For those that dont know what a bull plug is....
http://www.grainger.com/Grainger/JB-SMITH-Bull-Plug-4WGH2?Pid=search
http://www.grainger.com/Grainger/JB-SMITH-Bull-Plug-4WGH6?cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1
I can snag em here in the oil patch all the way to 18" or bigger diameter if I ask for a "used one that is no longer needed"
Gunner
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typed in rec.crafts.metalworking the following:

    Seems to me that it's not getting enough oxy (or too much gas) - yellow flame is incomplete combustion. Monkeying with it might be more trouble than worth.     Setting the pot down closer to the flame (or raising the burner) would at least shorten the distance between torch and metal., and the distance the heat has to travel before it does some "useful work".     OTOH, if the flame is touching the pot, there may be soot deposits (until it heats up enough to keep the soot from 'condensing' on the pot.)
    OTGH, if the set up is getting the whole pot up to red heat - fugedaboutit. -- pyotr Go not to the Net for answers, for it will tell you Yes and no. And you are a bloody fool, only an ignorant cretin would even ask the question, forty two, 47, the second door, and how many blonde lawyers does it take to change a lightbulb.
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.
You want a thin-wall pot so you don't spend eternity waiting for it to come up to melting temp. With wheel weights, I've found that remelting at least twice is a good idea, not everything gets skimmed off first time around.
yellow flame=not enough air or too much gas. Maybe it was designed for natural gas?
I get far better and more uniform bullets using a ladle, there was a piece in Handloader just recently about ladle vs. bottom-pour. When doing pistol bullets, I have 4 and 6 gang molds, very fast pouring using a ladle.
I've got any number of plumbing crucibles, best thing for melting scrap is what my dad used, an orphan dutch oven. Can do like 75 lbs of wheel weights at a whack. If anyone needs a scrap lead furnace, one of those turkey fryer/crab boiler burners works wonders. When I had several tons of wheel weights to melt, I had one of those with the dutch oven and a propane plumber's furnace with a 50 lb crucible going at the same time. Biggest problem was cooling the ingot molds down between casts.
I wouldn't use an aluminum pot for anything related to melting lead. Aluminum gets hot-short, too much risk of the bottom dropping out without warning.
Stan
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On Tue, 30 Oct 2012 15:19:13 +0000 (UTC), Gunner

Flame temperatures are pretty much the same, or the same relative to the fuel. just about the tip of the blue part of the flame is usually the hottest but depending on the flame you might want to adjust it a bit to get heat to the widest portion of the pot/crucible.
You might want to google on "forge burners" to see what others are doing on the same subject. The burners are quite easy to make.
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Cheers,
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On Tue, 30 Oct 2012 15:19:13 +0000 (UTC), Gunner

<snip>

Like the other posters said, needs more air. I made my burners with a damper on the air inlet and oversized the air. More air will probably shorten up the flame, though.
When I first started working I had a project to increase the efficiency of some natural gas calcining kilns. They were about 15' dia. x 200' long, 12-16" air pipe with 4" gas line, 3 kilns making about 270 tons/day. Gas was introduced through holes from a ring plenum welded all the way around the air line. After getting a lot of data, we shut those off and just introduced the gas in the center of the air pipe with a long radius ell. Decreased the back pressure so we got more air. Then I had the foreman rotate the 4 mixing vanes down the pipe to a 45 deg position, all the same direction, to spin the whole mess. they had been set at a low angle in opposing pairs and no one could ever remember them being moved.
The flame went from a long skinny one about 40' long to so wide it filled the shell and washed on the walls. I talked to old McClure, the foreman as we looked at it through the heat shields and asked him to rotate the vanes to a less severe angle. He said naw, he wanted to see what would happen. Well, it only took a few days and it burned out the refractory so they had to re-brick the kiln. Then we adjusted the mixing vanes to just pull the fire off the walls.
The final effect was 10% more rock through 40 year old kilns for the same amount of gas. That was a fun project.
Pete Keillor
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Pete, it probably HAS shutters on the air intake of the mixer body, and he didn't know they were adjustable... <G>
And the question about "is it (more efficient) if flame is going up the sides"??? C'mon... it might be a bit faster, if you heat the sides as well as the bottom, but more efficient?
If _any_ heat is bypassing the container, instead of being absorbed by it, how would that be more efficient?
The most efficient burner/pot combination would be where zero heat was allowed to escape up the sides. But that would also make airflow with a gas flame just a little difficult.
LLoyd
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On Wed, 31 Oct 2012 06:32:29 -0500, "Lloyd E. Sponenburgh"

The top of the device has 3/4" tall grid on which the flat bottomed pot sits..so the only exit is that 3/4" space below the pot and above the sides of the burner body. The burner itself is a good 3" below the bottom of the grid, so all the heat does to straight up, strikes the pot bottom, then spreads out the openings between the grid body.
Ill post a picture when I get back from LA later in the week.
Thanks guys!
Gunner
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On Wed, 31 Oct 2012 06:27:22 -0500, Pete Keillor

Thanks for the heads up! Ill open up the air inlet and put on an adjustable damper and see what happens
Gunner
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