-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.
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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. |