Common faults of vertical vacuum hot pressing furnace

09-18-2025       Author: KJ technology

During the operation of a vertical vacuum hot press furnace, various faults may occur, which can be roughly divided into four categories: abnormal temperature, abnormal vacuum degree, mechanical structure faults, and other faults. The following is a detailed introduction:

Temperature anomaly

High temperature alarm:

Possible reasons: abnormal temperature controller parameters, breakdown of solid-state relay, poor contact of thermocouple probe.

Solution: Verify the temperature controller parameters to the normal range; Measure the output resistance of the solid-state relay with a multimeter after a power outage. If it is broken down, replace it; Gently shake the thermocouple probe when powered on, and replace the probe if the temperature controller shows a large jumping amplitude.

The displayed temperature is too low to reach the set value:

Possible reasons: No output signal from the thermostat, damaged thermocouple, non powered heating tube, or circuit malfunction.

Solution: Check the temperature controller parameters and output signals; Swap the thermocouple with a normal thermostat for testing, and replace it if it is damaged; Use a test pen to test the connecting wires of the heating tube. If there is electricity, use a clamp meter to measure the current. If there is no electricity, check the circuit components one by one according to the circuit diagram.

Abnormal vacuum degree

Vacuum cannot be drawn up or is too low:

Possible reasons: insufficient vacuum source or compressed air pressure, vacuum gauge malfunction, poor sealing of furnace door, gas leakage in pipelines or pneumatic valves, and damaged sealing of thermocouple inlet.

Solution: Check if the vacuum gas source pressure is above -95KPa and if the compressed air pressure is within the range of 0.4-0.6MPa; Check the parameters against a normal vacuum gauge; Check whether the sealing rubber ring of the furnace door is damaged or deformed, and whether the door panel is stained with foreign objects; Check the position of the pipeline, pneumatic valve, thermocouple inlet, etc. If the thermocouple is replaced and the seal is damaged, re apply AB glue for sealing.

Decreased vacuum degree:

Possible reasons: reduced performance of Roots pumps or mechanical pumps, equipment leakage points, and inadequate sealing of furnace doors.

Solution: Repair or replace vacuum pump spare parts; Check whether there are leaks in the connection parts of the equipment and repair them in a timely manner; Check the sealing rubber ring of the furnace door and replace the aging or damaged sealing ring in a timely manner.

Mechanical structural failure

The door is not tightly closed:

Possible reasons: Loose hinges, deformed buckles, damaged sealing strips, and deformed door panels.

Solution: Tighten the hinges of the door; Correct or replace the buckle; Replace the sealing strip; Correct the door panel.

The fan has abnormal noise:

Possible cause: Foreign objects entering the fan impeller and loosening of screws fixing the motor.

Solution: Clean the foreign objects inside the fan wheel; Tighten the screws that fix the motor.

Pneumatic valve cannot operate:

Possible reasons: malfunction of solenoid valve, insufficient compressed air pressure, and damage to the pneumatic valve itself.

Solution: Check if the solenoid valve is working properly. If there is a malfunction, repair or replace it; Adjust the compressed air pressure to meet the working requirements; If the air pressure is normal and the solenoid valve is in good condition, replace the pneumatic valve.

Other faults

Color change of spare parts:

Possible reasons: The spare parts are blue in color and have a high water content (the spare parts are green in color).

Solution: Check the vacuum status of the vacuum furnace to ensure that it is dry inside.

Carbon addition in parts processing:

Possible reasons: The cleanliness of the heated type is low, and there is residual heat in the feeding cart that enters the cold wall of the hot chamber.

Solution: Improve the cleanliness of the heating system; Clean up the residue of the feeding cart to avoid entering the cold wall of the hot chamber.