So...my plan is to construct a salt pot (someday soon, I hope) with 3 inch OD diameter stainless tube as the pot. I've looked at various plans/drawings/photos, and it seems that many folks have found using a T-Rex (or similar) burner at the bottom, with exhaust at the top is the way to go (and one can use the exhaust port to pre-heat/dry the knife before inserting into the liquid salt).
My current question (I've had many) is: how much airspace do you leave around the salt pot inside the forge? I'm going to try to put as much insulation in the walls of the forge as possible, but how much free-space around the pot does one typically leave for air to swirl/circulate to heat the pot? Has anyone out there experimented with different sized inside diameters for the forge that the pot sits in?
Right now my plan is to use an old 15" diameter propane cylinder as the shell with 3 inches of insulation all around (skim coated with satinite and painted with ITC-100). That will give me about 2.75-3 inches between the stainless tube and the walls of the forge. Is this enough? Too much?
Any advice is welcome. And thanks in advance.
Steve,
If you have not bought everything yet why not consider an electric kiln rather than propane. I think your salt pot will have a greater life expectancy if it does not have a very hot propane burner hitting it with flame. I currently have two kilns set up with salt pots (one high temp and one low temp), and a propane powered horizontal 40 inch low temp tank. My high temp tank is electric made by L&L specifically for my heat treating purpose. I have a program set into the control unit that compensates for the outside temp of the tank versus the actual salt temperature. The computerized controller allows me to have a program for each steel that I heat treat. However, my first tank was a very simple kiln with manual controls and a 24 inch height and 4 inch diameter 304 stainless salt pot. I used a probe to measure the temperature of the salt (I still do this for a reliability check) and things have worked well. Often times you can pick up a used kiln for a few hundred dollars or less. Cut a hole in the top of the kiln for the pot and you are pretty much ready to go.
My guess on air volume around the pot is about double to triple the volume of the salt pot. If you have a 3 inch diameter pot you should probably have about a nine inch diameter chamber.
Ideally, an electric type kiln with the clay that makes up the kiln and heating coils cast to the tube would be the best of all possibles. In an electric kiln the less air space the better it would seem.
Dan
Dan,
I hadn't thought of that--casting the stainless salt pot directly into an electric kiln. I just googled "electric kiln salt pot" and found a bunch of hits. The main drawback would be cost (those kilns are expensive), but over the long haul it would make up for itself if the stainless insert held up well over time. I found this evenheat online...is that about the right size?
http://evenheat-kiln.com/porcelain/rmseries/rm2-1822/
I imagine (perhaps incorrectly) that custom made kilns are more expensive. What dimensions/specifications did you figure out would work well for your custom unit from L&L? Narrow and tall would be best, I presume...
As for the propane, my plan was to have a big enough airspace so that the burner isn't hitting the tube directly, but heats the walls of the forge instead (not my idea--another ABS member advised this). That should help increase the durability of the salt pot, but not nearly to the extent as the electric kiln conduction heating method you mentioned.
Thanks for the advice--I'm going to look into these kilns. Options are always good!
Steve
Steve,
My kiln is 14 inches inside diameter. Three inch insulating firebrick and 36 inches tall. My tank is 35 inches tall inside height so that I can heat tx a sword of up to about 33 inches in blade length. The salt pot tank extends through the top of the kiln by about 2 inches but the salt when hot expands to within a couple of inches of the top. I have kaowool surrounding the top of the tank where the salt pot still exits out of the kiln.
However, my first kiln was a standard size kiln of about 22 inches. I see these pretty frequently advertised for sale. Check out a local HS or University where they teach ceramics. Frequently you can find a good kiln for 1/2 the price or less. Check out the local pottery store where they sell kiln and clay supplies. I have seen kilns for sale at $200 to $300 dollars.
Dan
