What safety interlocks are there on the furnace door of the graphitizati"&"on furnace?

Last year, a customer from the south came to the workshop on a sweltering day to see a demonstration of the equipment. Standing in front of the furnace door, he half-jokingly said, ""Th"&"is is what I fear most. When the door opens, it's over 2000 degrees Celsius inside. Standing next to it feels like standing on a volcano!"" I patted the furnace door and said, ""Don't worry, our doors are harder to open than a bank safe deposit box, and y"&"ou simply can't open them.""

Mechanical Locking

After the furnace door is closed, the handle must be rotated to the designated position according to the prescribed procedure to lock it. Once locked, the limit swit"&"ch installed at the locking point detects this and sends a confirmation signal to the PLC. This is the starting point of the safety chain—without this signal, nothing can start.

Electrical Interlock

Before st"&"arting heating and vacuum, the PLC hard logic checks three necessary conditions:

1. Is the furnace door completely closed?
2. Is the mechanical lock locked?
3. Has the limit switch issued a confirmation signal?

Starting is only allowed if all three conditions are met simultaneously. Even if one signal is missing, the system will absolutely not start. This is hard-wired and mandatory, not software-based—even if the software has a bug, the hardware i"&"nterlock remains effective. This design concept is called **""fail-safe""**.

Live Protection

When the furnace is under positive pressure, the **furnace door cannot be opened normally**. The exhaust program must be"&" started first to reduce the furnace pressure to below a safe range before the system allows the door to be unlocked and opened.