propane salt pot questions

jdm61

jdm61

itinerant metal pounder
Joined
Aug 12, 2005
Messages
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some questions for any of you maniacs who use propane fired high temp salt pots.
1. do you have corrosion issues with tools, steel, etc in the shop from the salt?
2. do you use a cone, plug, etc to make a hole in the colling salt so it won't boil over when you heatit up again?
3. How do you suspend the blades in the salt tube?
4. how many blades can you heat up in one sitting?
 
jdm61 said:
some questions for any of you maniacs who use propane fired high temp salt pots.
1. do you have corrosion issues with tools, steel, etc in the shop from the salt?
2. do you use a cone, plug, etc to make a hole in the colling salt so it won't boil over when you heatit up again?
3. How do you suspend the blades in the salt tube?
4. how many blades can you heat up in one sitting?
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I don't have corrosion issues in the shop.

I don't use a cone or anything. The salt just melts when you start it up. I do put a piece of steel plate over the top of the tube at start up to help keep the heat in and catch any little splatter. (You shouldn't have any big eruptions unless there's water trapped in there or something.)

I use steel welding rod to suspend the blades.

My tubes range between 4 1/2 and 6 inches. and I usually do 3 or 4 knife blades at a time.
 
JCaswell said:
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My tubes range between 4 1/2 and 6 inches. and I usually do 3 or 4 knife blades at a time.
Click to expand...

A question about your salt tubes, what grade SS are they? I have some 3-6" SCH40 sections that I can get my hands on. (I work for an industrial contractor and we work in a lot of petroleum refineries)
 
I use double venturi burners on my pots. I have a removable rod that cantilevers over the top about 24" above the salts. I use tie wire (for Ford owners AKA known as baling wire) to suspend the blades in the salts. My container is made of schedule 80 carbon steel pipe w/ a 3/4" thick base plate. The base plate is a 100% weld to the pipe.
I have not noticed much for corrosion in the shop. I did have it set up next to my anvil once and the top of it did develop a layer of rust about a month later but a little WD & elbow grease w/ steel wool took care of that. Now I coat the top of my equipment w/ Briwax and have seen no further rust.
 
Peldor said:
A question about your salt tubes, what grade SS are they? I have some 3-6" SCH40 sections that I can get my hands on. (I work for an industrial contractor and we work in a lot of petroleum refineries)
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My tubes are about 3/8 inch wall thickness (Don't know the schedule). I believe they were 300 series stainless (316 maybe?), It shouldn't matter, though. As Bill said, you can use plain steel tubes too. I did that on my first go round, but when I changed them after a few years, I decided to try stainless this time.

For a shorter unit (for knifes and such), I'd go with the 6-inch. For sword-length units I've found 4 1/2 to be plenty (I don't do more than 1 sword at a time, but often do knives in batches and that's just a matter of how many can fit in comfortably).

BTW, I'm running mine on natural gas the last few years --- much more convenient than schlepping tanks around!
 
JCaswell said:
My tubes are about 3/8 inch wall thickness (Don't know the schedule). I believe they were 300 series stainless (316 maybe?), It shouldn't matter, though. As Bill said, you can use plain steel tubes too. I did that on my first go round, but when I changed them after a few years, I decided to try stainless this time.

For a shorter unit (for knifes and such), I'd go with the 6-inch. For sword-length units I've found 4 1/2 to be plenty (I don't do more than 1 sword at a time, but often do knives in batches and that's just a matter of how many can fit in comfortably).

BTW, I'm running mine on natural gas the last few years --- much more convenient than schlepping tanks around!
Click to expand...

The 316 SS is what I can get and might try. I was looking at about 4"-6" diameter and about 18"-24" deep.
 
I don't know if this is correct and I hope Kevin Cashen or somebody else with a lot of salt pot experience will chime in, but I thought that I read somewhere that the low temp salts are actually more corrosive.
 
Low temp salts are pussy cats compared to high temp. I have my low temp salts in thin walled well casing and have never had any problems with them. You can leave a film of low temp on your blades and not have problems from the salts as much as the fact they they are very fond of water and will pull it right out of the air so that you blade rusts from being soaking wet all the time. The high temp will corrode a blade in minutes if you do not rinse them off and are quite nasty about it.

NaCl based high temp salts give off vapors and pop particulates on heating that are quite corrosive to metals withing 6 to 8 feet of them and I would not situate them in a finishing area of the shop. The vapors can be kept under control quite well by slight ventilation or a surface layer of silicon carbide powder that helps keep neutrality.

I used to not use the tapered rod into the high temp tube to create a vent hole, and had some tube failures that I believe this was a contributing factor. I have also had some very close calls with the lower portion going liquid before the top and am lucky to still be alive. So for the high temp salts I strongly urge the insertion of a long tapered rod before shut down so that it can be removed before reheating.

This is not at all necesarry for low temperature for as Mr. Caswell pointed out, they just simply melt at around 275F and that is it.

I suspend my stuff by wires as holding them with tongs for extended soaks is tedious.

I do not heat more than one blade at a time since I will be a bit distracted with escorting one down below Ms to pay attention to the other. I have found that leaving the other in the low temp salts above Ms while I work the other results in distortion that is harder to deal with due to some bainite formation, I also cannot abide the idea of long halts in the cooling process with untransformed austenite. If these considerations are not an issue foryou then the only other dissadvantage of "batching" the austenitizing is the ammount of rebound time the untis have to deal with when introducing largers masses to heat. Crowding the blades could result in less than even heating as well.
 
I stuck a 5/8" drill rod in the salt after it started to solidify around the edge, after my first try heating a blade with it. That seemed to do ok I guess, pulled out easily once the salt was fully solid again.

Water is a big problem. I had removed the salt (NaCl & CaCl) from the first test a while back and had it stored in a separate container - it was full of sludge from the humidity when I looked at it again. What little salt that did pop out of the tube while using it this last time left wet spots all over the concrete after a couple minutes. Being a half hour from the Gulf of Mexico does not lead to happy times with this stuff.
 
hardheart said:
I stuck a 5/8" drill rod in the salt after it started to solidify around the edge, after my first try heating a blade with it. That seemed to do ok I guess, pulled out easily once the salt was fully solid again.

Water is a big problem. I had removed the salt (NaCl & CaCl) from the first test a while back and had it stored in a separate container - it was full of sludge from the humidity when I looked at it again. What little salt that did pop out of the tube while using it this last time left wet spots all over the concrete after a couple minutes. Being a half hour from the Gulf of Mexico does not lead to happy times with this stuff.
Click to expand...

That's what I am worried about. I live just north of New Orleans and its very humid for most of the year, so humid that it makes the salt shakers in my house solid. (living less than 10 miles from Lake Pontratrain and 3 miles from the Honey Island swamp probably doesn't help either)
But I would think that you could reclaim the salt that gets wet by slowly bringing up the temperature and driving the moisture out. That is unless water+heat would cause some kind of chemical reaction that would change its properties.
 
I wrote our good friend and addiction enabler Mr. Ellis and he said that he includes a "plug" and a lid with his salt pots even though the plug may not be quite as necessary on a two burner unit.
 
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