Re: melting furance

ArtMetal
Bramblebush


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Posted by Rob Frink on May 08, 1999 at 20:53:16:

In Reply to: melting furance posted by mike on May 02, 1999 at 16:47:44:

Mike,

Sounds like your furnace might be like the one posted here by Jerry James. Here's the link: Aluminum Melting Furnace.

Recently I was not happy with my furnace because it seemed to take a long time to heat up. I was melting bronze and the max temp was 1950-2000 f. I revised my burner and picked up 200 degrees more.

Referring to the sketch This is similiar to my burner. It is made from automotive exhaust pipe pieces. Notice the reduced diameter where the gas line enters. I feel that this is important because reducing the diameter increases the air velocity and causes a pressure drop in the reduced section. The pressure drop in the reduced section helps "suck" gas into the burner. This means more fuel. Also the increased velocity means more turbulance for better mixing of fuel and air. After the reduced section the burner opens back up the the original dia where the fuel air mixure expands and slows down. Here is a photo of my exhuast pipe burner. . I just welded straight pipes to reducers as you can see.

Now for the most important feature. (not shown in the photo, but in the sketch) The tip of the burner tube where it enters the furnace should be reduced. I just pounded it in with a hammer. The smaller section will again accelerate the fuel/air as it enters the combustion chamber of the furnace. It's a jet! The sound from your furnace should roar as the fuel/air is injected in and swirls around the crucible. I feel that air speed is important. It helps combustion by mixing the fuel and also transfers the heat to the crucible by swirling around it.

Your burner must enter tangentially to the furnace wall and your blower must have enough pressure to force air thru the restricted burner tube. I don't think a hair dryer would have nearly enough output for this application. A small shop vac would do a much better job in my opinion. You need some sort of blast gate to adjust the amount of air flow. Listen to the furnace and adjust the fuel and the air for the maximum roar.

You should'nt have any problems melting aluminum.

I hope that I given you some ideas that will help. If you need any help, just drop me a line.

-Rob


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