-Salt Tanks-

My appreciation extends to Kevin Cashen and Mike Starling
who advised me in the construction of these potentially dangerous tools. Thank you.

I have recently completed a sword-length high temp salt tank for heat-treating my blades. It is digitally controlled and gas fired. The salt tank itself is a 34" x 4" x 1/4" stainless steel tube which you can see protruding from the top of the unit on the left. I intend to upgrade to a 3/8" thick tube when I find one for a reasonable price. My salts are a 50 / 50 mix of sodium chloride and calcium chloride as suggested by Mike Starling. So far they are working satisfactorily. There is a thermowell protruding into the tank from the bottom that holds a 14" thermocouple. It measures the temperature of the tank and sends that information to the digital temperature controller.

Surrounding the stainless steel tube which holds the actual salt is a 14" diameter 3/8" thick pipe lined with Inswool and coated with an undercoat of Satanite and an overcoat of ITC-100. Satanite is a mortar refractory which is hard and stable; ITC-100 is a refractory meant for kiln walls which reflects heat very efficiently. The burners are based on Ron Reil's design. I had to use the 2" bell reducer and the Tweco Tip with an orifice of .035 to get the burners up to temp. There are two so I can heat the top of the tank first, as the salts expand greatly when they melt and using the bottom burner exclusively would create a monster pipe-bomb. Once up to temp I switch them and the bottom burner maintains the heat.

The exhaust port behind the tank is a 3" elbow that rises into the 4" stove pipe. The draft of the heating chamber gasses pulls additional air over the actual molten salts and effectively vents the fumes.

These are the in-progress controls: the gas line comes in and runs to two separate sets; the bottom one is for the unfinished low-temp tank and the top set is for the high-temp tank. Each has a 12V solenoid valve that is operated by the relay in the digital controller. Each controller runs only one device, so I will need another for the low-temp tank. I am using the Omron E5CN with the relay option which costs $131.00 from MSC Industrial Supply. With the two valves on each line I can run the tanks manually, set a high burn and a low burn or simply fuel on and fuel off. The low-temp tank may need a maintenance burner which will mean that instead of rejoining, the two separate valves will run two separate lines.