Operating procedures for vacuum box furnace
1. Set the temperature rise and fall curve. The temperature rise rate shall not be higher than 10 ℃ / min and the temperature drop rate shall be lower than 15 ℃ / min.
2. Clean the environment.
3. When using the tubular furnace every week, check that the oil line of the mechanical pump is above the marking line, remove the covers at both ends, and clean the corundum furnace tube with a vacuum cleaner.
4. Push the sample boat into the middle of the rigid tube and furnace (constant temperature length 10cm).
5. Plug two insulated furnace plugs so that the end of the second furnace plug is flush with the side of the furnace body.
6. Install the gas furnace flange and confirm that the gasket falls into the groove.
Ⅰ. When hydrogen is used as working gas
（1）. Connect the hydrogen gas circuit, use soapy water to detect the leakage at each joint and confirm that there is no gas leakage.
（2）. Confirm that all valves are closed.
（3）. Turn the knob clockwise to open the pressure reducing valve at the outlet of the hydrogen cylinder slowly, and turn the knob counterclockwise to open the pressure reducing valve at the outlet of the hydrogen cylinder
（4）. Turn on the power supply of the mechanical pump, open the outlet valve of the tubular furnace and the two valves on the gas path of the mechanical pump, and pump for 5 minutes.
（5）. Close the two valves on the gas path of the mechanical pump, close the outlet valve of the tubular furnace, and shut down the mechanical pump.
（6）. Open the upper air circuit control valve counterclockwise so that the arrow points to the “on” position.
（7）. Adjust the flowmeter knob counterclockwise to make the indication at 20ml / min.
（8）. Turn the knob counterclockwise to open the inlet valve of the tubular furnace until the barometer reads zero.
（9）. Open the inlet valve of the vacuum tube furnace and the red outlet valve on the hydrogen gas path.
（10）. The heating of the tubular furnace can only be started after ten minutes of hydrogen. Before heating, adjust the flowmeter knob counterclockwise to make the speed of bubbles in the conical bottle 2 / s.