Optimal Startup Procedure for Immersion Heating Furnaces

START-UP IN A COLD DRY FURNACE

1. Close the furnace.
2. Before you turn the power on:
   1. Set the heater thermocouple high limit at 1700 deg. F.
   2. Set the percentage of power to the heater at 15%.
3. Turn the power on.
4. Increase the power every 5 minuets by 5% until the temperature in the heater approaches 600 deg. F.
5. As the furnace warms up, it will be necessary to reduce the power to the heater to avoid tripping the 1700 deg. high limit. (The power off and on switching that occurs from excessive tripping of the high limit over time is detrimental to the ceramic tube and the heater wire).
6. Allow 48 hours of pre-heat before introducing metal to the furnace.

1. Reduce the power to the heaters by 10%.
2. After 15 minutes, add metal quickly to bring the level 3” above the top of the
   heaters.
3. Turn the power to 90% and continue filling the furnace.
4. Raise the heater thermocouple high limit to 1850 deg. F.
5. The metal temperature will drop considerably before it begins to rise.
   If the heater approaches the high limit at 90% power you may increase the high
   limit to 1900 deg. F.

NORMAL OPERATION

1. After determining the percent of power required to maintain the bath temperature
   (usually not more than 70%) you should limit the maximum power to 20% more
   to give adequate recovery capability.
2. A build-up on the protection tube will cause a temperature rise in the heater and
   heater failure. A spot build-up on the protection tube may cause a heater failure
   with no warning.
3. Periodic cleaning of the protection tube is recommended for long life.
4. The frequency for scraping the tubes is determined mostly by oxides from the break-down furnace and from alloy modifications.