High temp salt pot build

[Saul Kokkinos-Kennedy]

So i decided to make a salt pot as my method of heat treating. Here's some quick info and pics. I will add to it later and update as i complete it.

 

It's almost done, just need to line it with ceramic wool and fix on the gas equipment and electronics.

Chimney is designed so that i can pre heat blades in it to remove any moister before going into the salt. Wheels are solid rubber so will not puncture and also have splash guards so they don't catch on fire. SS pot hangs from flange that sits on lid, and is located by 4 tabs.

Salt tube is 316L 100mm or 4" ID and 500mm or 19.5" deep.
Gas tank body is 600mm or 23.5" tall and 300mm or 12" diameter.
The chimney is 100mm * 150mm or 4" *6".
Burner is a 1" venturi.

Any thoughts or suggestions welcome.

 

 

 

[J.Arthur Loose]

Looks good. I'd be mildly worried that the hanging tube will put stress on it at temp and allow it to deform, but I always look for things that can go wrong...

 

Are you going to manually control the temp?

[Bret]

I've never made or used a salt pot. That being said I've always heard that it can be extremely dangerous to heat a cold pot too quickly from the bottom. Solid salts seal the top while pressure builds in the melting bottom...boom. I'm sure someone with far more experience than myself will chime in. Be careful though. I worked with a guy for years with some serious facial scars from these so honestly they scare the hell outta me.

 

Really cool build though nice work.

Edited October 22, 2015 by Bret

[J.Arthur Loose]

Yes, my tube is much longer and I have a secondary burner closer to the top. If you heat from the bottom you can blow up the tube, with violent results.

 

Another alternative, and law in some places in the US, is to put a tapered stainless rod into the tube when it's cooling. When heated again, the tube will conduct heat, pop itself up enough to release pressure and prevent pressure explosions. So they say.

[Saul Kokkinos-Kennedy]

Hey Arthur, yes i was mildly worried that the lid may deform due to conductive heat and the weight of the salt filled tube, so i have added a 22mm round stainless rod to the bottom that sits 5mm away from the bottom of the SS tube. Also this will be controlled by a PID and solenoid valve.

 

Bret, yes it will definitely require my full and undivided attention while operating, I think the worst part will be filling it for the first time. Still figuring out how i will bake the salts to remove any moisture prior to putting in the SS tube. Thinking i'll do it in the forge at low heat in small batches.

 

In regards to the tapered SS rod, I have a strong suspicion that the conductivity of SS is no where near high enough for it to melt the salts along its length and release itself before the salt at the bottom has expanded a dangerous amount. My plan is to place the taper in before shutting it off, and taking it out before i fire it up again.

[Saul Kokkinos-Kennedy]

Here you can see the adjustable stand i made to hang the blades in the pot for heating, and the cover that can swivel over the pot. I will use the cover when firing it up, as the salts will absorb water while not in use, which will cause some spitting as it is heating.

 

Here's the solenoid valve and needle vale for idling.

 

Inside of the body. You can see the support rod at bottom of chamber.

 

Tapered rod. The rusty piece of steel slides up and down the shaft and will be used as a form of hammer to remove the rod from the solid salt. I still need to weld a cap on the end that i will strike upwards against.

[J.Arthur Loose]

Looking good- I've never had a problem with the high temp salts (50/50 Calcium / Sodium Chloride) absorbing moisture. I have a lid that has an open vent on it, and in the Summer it gets quite humid in my shop. The low temp salts are another story, and I keep a plastic bag over the top with a good rubber band around it when not in use.

 

I like your adjustable hanging rod. I usually make a hanger out of 14 ga. wire, with a bunch of bends to hold my blades, and it would be hard to describe, but easy to draw... A hanger like yours would be great for thermo-cycling, when the salt wants to drip off the blade tip.

 

It occurs to me that I haven't posted pics of my set up with info: http://www.jloose.com/studio.html

 

Let me know how the tapered rod seems to work.

[J.Arthur Loose]

Oh, you can bake the salts dry, assuming you're using calcium chloride and sodium chloride, by putting trays of it in an oven at a low temp like 200F and then storing them in an airtight container.

 

Or do what I did, and just keep dropping small amounts into the tube, little bit by little bit, with very good ventilation and a couple layers of clothes you don't care about, because little tiny bits of new salt with ambient moisture go POP! SIZZLE! SPIT! And the fumes of the moisture with the salt will leave a little bit of rust on everything. But after they're fired up and melted... the fumes are much less oppressive. Note, however, the venturi style fume vents on my exhaust flues in the pics in the link above. They work really well, and you can watch the fumes get sucked up and away.

Edited November 14, 2015 by J.Arthur Loose

[Saul Kokkinos-Kennedy]

Thanks Arthur, good to hear you haven't had any problems with moisture absorption. I'll be using a 50/50 mix of sodium chloride and calcium chloride too. Yeah the stand was made with normalizing in mind. Cheers for the link, looks like a nice setup, I'll be looking at doing a low temp pot if this one works out well.

 

Not sure that i want to try baking the salts in the kitchen oven, think i'll try doing it in the forge on the lowest heat i can. Your venting system looks good, and i would probably try to rig up something similar, but i only plan to use the pot outside.