Propane tank/fueled furnace build

Usually when I get the spitting and sputtering I have to cut the gas down a little bit until it gets smooth. Looks really nice though!

 

Edit...I was unable to see the video until just now .. dont think it is too much gas in the vid...possibly not enough. You are very close though...just play around with it in small increments until you get it smooth. But I would not try to do it before getting the walls dried out thoroughly.

 

Thanks Billy. So, I guess I will not mess around with the internal flare shape anymore. I forget the propane pressure at that particular moment of the video but around 20 pounds maybe?
So, for drying now...just put a 60 or 100 watt light bulb in there and leave it on for a few days, with the lid on? Or on and off for a few days? The liner is about 2 days old? and the outer shell about 4 days old, just sitting in a heated shop.

 

Yeah...nice and slow is the way to go. I had a hard time not fooling with it while I waited ...seemed like months before the weekend finally made it.

 

Ha! I knew he would probably be on here but had no idea who it was. I thought I had heard his voice before.LOL He's been very helpful on here!

 

I did a run this morning...granted I did melt about a pound more of aluminum than the last run...with the lid off. I was able to run full pressure at about 22 psi and the furnace got red much faster. However after I hit the 15 minute mark I realized I was not getting much hotter as I should have been melting but wasnt....at 20 I turned the gas down to 10 and put the lid on. It melted at around the 25 minute mark. My conclusion is that running the gas higher in my furnace will get to a certain temp faster but after that it is better to lower it and put the lid on it. I definitely am restricted by my lid and it is a little over 3". I can not get above 12 o 13 psi with the lid on or it extinguishes the flame. My next run will be five minutes with the lid off and then lower psi on gas and put the lid on. I believe this will be my most efficient way to do it in a timely matter.

 

Also..because of the higher flame impeding on my crucible I decided to raise it an extra half inch before I ran it.

 

You may be rediscovering the principle that blowing fuel and air too fast through your furnace prevents full combustion in the furnace with the result that the furnace is acting like a pre-combustion chamber and is “cold.” Many many folks have turned up the fuel and blasted in tons (literally) of cold air in hopes of maximizing heat only to be disappointed. The air introduced into the furnace during a melt is the heaviest item heated being much heavier than the furnace and much much heavier than the crucible/metal.
Denis

 

Oooops, forgot you were naturally aspirated. Agree with Kelly above.

Denis

 

Hi All

I thought I should check in. I have not disappeared but since the furnace needed time to dry, I got into other projects. I have been active on the mill and lathe a lot so it has been good. The furnace has had a 60 watt light bulb running for over a week and half. Not sure when I will put some real heat into it. For initial heating, I have seen temps quoted like 700 (F?) for the first heat. How do you measure that? IR gun on the wall with the flame off? How long should it take to get there?.... just to give me a window...I am thinking couple of minutes but then it will cool as the heat is absorbed into the refractory, I would think...?

Then let it cool fully and do it again right after or give it a day?

I ended up with a smaller crucible than mentioned earlier in these posts. Amazon was not shipping the one I had ordered (I regretted ordering it....too big) so I was able to cancel it and have a much smaller one now. I need to make the tools to handle it yet too.

Just thought I would throw an update out there.

Take care
Shawn

 

Kelly
The hottest I saw was only 40 celsius, no where near 280 F. I did not have anything hotter at the time and did not picture it running this long. Having said that, I have not checked it for several days so if moisture was coming out, that might have countered the temp. I will see about getting a 200 W today. It is being run in a heated shop but I can do the insulation wrap if you think it is important.

Thanks
Shawn

 

I don't think you'd be throwing caution to the wind if you started a fire in there now. If you've had a light bulb in there for 10 days (incandescent, not fluorescent I hope) you've gone an awful long way in drying it out. My dryouts generally have taken the better part of a day. Do it all in one go. When you're ready start a small kindling fire, barely enough to cover the bottom, put a couple of pieces of angle iron across the open bore and set the lid on. Your just looking for gentle heat for now. Maintain that same size fire for an hour and then double your wood volume for another hour. Then double and maintain for another hour, then add a hair dryer, etc. Being able to dump your furnace periodically is helpful.
Alternatively after your initial small wood fire phase, if you have some control of your burner, insert your burner and set it low and then gradually increase its intensity for hour long periods. Your primary concern here is drying as thoroughly and slowly as possible. If you see a real lot of steam, then back off a little. By your 5th hour you should probably be running full tilt. Take it easy, but do it. Either your refractory mix will hold up or it won't. Even if you're not completely cured in this initial firing, it'll eventually get there through use.
This is basically how I've done 3 furnaces and they're all fine.

Pete

 

Hey guys

Sooo, after going great guns to get this furnace up and running, distractions set in and here we are, after a month of slow drying with the 60 watt light bulb (around 100 F), and then shutting it off for a week or so, I finally fired it up today to check out the burner. I think the burner may need an air restrictor of some sort. I played around with holding my hand over the inlet a bit and I think it will be workable. Might work on that tomorrow. I was able to get, what I think, is a nice flame but maybe you with more experience can shed some light on it for me....?

The highest temp I ran it to was about 400 F....but that temp did not last long so I think it was just the refractory surface. I only ran the flame for 30 to 60 seconds.....? Doubt I exceeded a minute. So let me know what you think. I guess the next step is to figure out a "plinth"..? Something under the crucible. Will a steel plate work? Or should I cast one out of the refractory? And I need to review heating the crucible initially...I think there were some concerns there too. Then make some crucible tools....:-O I have forgotten what I read in the last few months. I have been wrapped up in other projects but time to get this one going again.

Cheers,
Shawn


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Getting close. It's making the right sounds.
I'd close it up and let her run! You can use this time to preheat your crucible to red hot. Shut down and let cool slowly closed up in the furnace.

 

Cast a plinth with refractory, don't try a thick steel lump in there.

 

Thanks guys. I will cast the plinth today and then in a few days, heat the crucible as per Jason

How thick for the plinth? I am thinking 1" ish? or does it need to be much thicker?