I. Software-Level Safety Interlocks (First Layer of Protection)

Implemented through the PLC (Programmable Logic Controller) system, real-time monitoring and logical judgment of key parameters are performed:

• Temperature Interlock: Heating cannot be started if the furnace door is not properly closed; if the furnace door is accidentally opened during heating, heating power is immediately cut off.

• Water Circuit Interlock: Monitors cooling water flow rate, pressure, and temperature. If any parameter is abnormal (e.g., flow too low, water temperature too high), an alarm is immediately triggered and heating is cut off.

• Gas Pressure/Vacuum Interlock: When furnace pressure is abnormal (too high or too low), it automatically links with the inlet valve, exhaust valve, or vacuum pump to prevent overpressure or implosion accidents.

• Electrical Interlock: Includes protection against overcurrent, overvoltage, and phase loss. Power is automatically cut off when the power cabinet door is opened.

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II. Physical-Level Safety Interlocks (Second Layer of Protection, Hardware Redundancy)

Independently set up outside the software system, a set of hardware protection devices not dependent on the PLC serves as the ultimate safety barrier:

• Electrical Contact Pressure Gauge/Flow Switch for Water Circuit: Even if the PLC's electronic sensors fail, this independent mechanical device, upon detecting abnormal water pressure or flow, can directly切断 the main circuit.

• Mechanical Explosion-Proof Valve: Installed on the furnace body, it automatically ruptures to relieve pressure when the internal pressure exceeds the physical limit, protecting the structural safety of the furnace body.

• Furnace Door Mechanical Lock and Limit Switch: Ensure that physical locking of the furnace door is a prerequisite for powering on.

III. Safety Philosophy

This design concept of combining software and hardware, with mutual backup, ensures that even if one system (such as the PLC) experiences a single point of failure, the other system can still function to put the equipment in a safe state, truly realizing the "fail-safe" principle.