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Salt Pot Burner Selection


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I have started work on a high temp salt pot for heat treating. I have a friend at a machine shop welding up the schedule 80 316L 4" pipe 24" long to a piece of 3/8" 316L plate. I am planning on using an old oxygen tank for body, insulated with 1" Kaowool coated with Satinite and ITC100. I plan on controlling with an Omega controller/solenoid gas valve setup.

 

The question is whether a single 3/4" T-Rex burner will be sufficient heat for this or whether I need to go with a forced air burner. I am guessing that there will be about 40 lbs of Stainless and 20 Lbs of Salt to heat up to 1400+ F. I fear it will be underpowered. I have a single T-Rex which I use in my forge which I plan to try to use at first. If it doesn't work I can go to plan B. I plan on getting Salt from Darren Ellis. I have also been looking at his burners.

 

I don't have any experience with blower type burners, only venturi style. Any recommendations on sourcing an electric blower would also be appreciated if I go that way. Thanks all. -Doug

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I'm burning a 3/4 venturi to heat essentially the same size and length of pipe. Takes about 30-40 minutes to stabilize at heat. I use a needle valve and thermocouple with an organic controller. I have all the stuff to setup a digital controller/solenoid but have never found the need to. You should be fine but there might be some bugs to work out until you're confident with the setup.

 

You should also have some method to preheat the stuff you're going to heat treat. Moisture and hot liquid salt do not play well together.

 

If you have this arranged as a vertical setup, you will also want a tapered pin, or a means to heat the salt from the top down.

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My salt bath is a bit longer, 50 inches, and I am running three burners in it and it runs great. When the salt cools the top of the solid salt is about flush with the top burner and I have not had any problems with pressure build up or a salt fountain. If you don't put a burner at the top to "prefire" the top of the tube when you first fire it up having a tapered rod like Mike said is a very wise idea. Also be sure to clean off the rod prior placing it in your salts to keep everything clean. Good luck!

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Thanks guys for the info. good safety tips. I do have a question on the tapered shaft/plug. As I understand it, the idea is to have the shaft create a hollow "pipe" in the solidified salt so that the melting salt at the bottom will not pressurize and go places it is not wanted. Does this mean that once the salt has solidified, you would remove the plug prior to heating (hence the need to taper it)? What diameter is reasonable? I am not looking forward to tapering a 24" x 1.5" steel rod by hand. 0.75" I could handle. Thoughts? Thanks. -Doug

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Doug, that is the exact purpose of the tapered plug. It doesn't seem that the salts melt so fast that a 3/4 hole would not work. The one I have seen is largish, but then the fellow that made it has a largish hammer too.

 

Make it as smooth as you can. All it will take is a couple pecks with the hammer and it should slide right out before firing the salts. Randal Graham built a fine unit that was angled 45 degrees. In that case the cooling and contracting salts form a pipe down the upper side of the tube and a tapered plug is not needed. But it is also a three burner unit and you start the top burner and add burners lower down if you need more pipe.

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One of the outside heat treaters I use has an Ajax Fireball salt bath. The bath is 28" deep and about a foot across. The burners are 3/4 up the unit but the exhaust is DOWN at the bottom. The burners are set around the circumference at a slight angle to create the swirl. I cant remember if there are 3 or 4. I'll be there monday and try to get pictures.

 

While these burners are blown, they are fairly gentle and certainly not beyond the btu's of a venturi type.

 

I've been offering to extend the unit at my expense to 34"-36" for years. They just won't be bothered YET!!

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Kerry and Mike, thanks for the info. Sorry I could not make it down to Fire & Brimstone. Sounds like you guys had a blast. Hope to see you at BGCM Blacksmith Days.

 

I have been on the fence regarding venturi vs. blown burner. I like my T-Rex but I guess I won't know if it will supply sufficient heat until I try it. Another question about the tapered plug. How much taper do you think is necessary? Would a 1" rod tapered down to 1/2" be sufficient. I think I am leaning towards having it machined rather than doing it myself. I have a friend who is friendly with a machine shop. It would be unfortunate if the rod could not be removed due to an irregular taper. I want to be safe.

 

Anyway, thanks everyone for the feedback. -Doug

Edited by Doug Seward
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