Common faults and solutions of box type tempering furnace

The common faults and solutions of box type tempering furnace are as follows:

1. Temperature control related faults
Not heating up
Reason for malfunction: Power supply failure (poor contact between socket and control switch), open circuit of electric furnace wire, low working voltage (excessive voltage drop in power supply line or poor contact between socket and control switch).
Solution: Adjust or replace the socket and control switch; Use a multimeter to check the electric furnace wire. If there is a broken circuit, replace it with an electric furnace wire of the same specification; Check the voltage drop of the power supply line and the contact status of sockets and control switches, and adjust or replace them if necessary.
Temperature out of control
Reason for malfunction: The thermocouple is not inserted into the furnace, the thermocouple index number is inconsistent with the temperature control instrument, and there is a problem with the compensation wire (short circuit or open circuit).
Solution: Check if the thermocouple is inserted into the furnace. If not, install it correctly; Check if the scale marks of the thermocouple are consistent with those of the temperature control instrument. If they are not consistent, adjust or replace them; Check the compensation wire, and repair or replace it promptly if there is a short circuit or open circuit.
Insufficient heating power
Reason for malfunction: low power supply voltage, three-phase power supply phase loss, aging heating element.
Solution: Check if the power supply voltage is normal. If the voltage is below the normal standard, check the power supply system and adjust it; Check if the power supply is missing phase, and if there is a phase loss, perform maintenance and adjustment on the three-phase power supply; Check if the heating element is aging or damaged, and replace it with a new one if necessary.
Abnormal temperature display
Reason for malfunction: temperature sensor malfunction (damaged or poorly connected), temperature controller malfunction, display screen malfunction (damaged or poorly connected).
Solution: Check the temperature sensor (such as thermocouple) and replace or tighten it if necessary; Check if the temperature controller is working properly, and replace or repair it if there are any issues; Check the display screen and replace or tighten it if necessary.
Large temperature fluctuations
Reason for malfunction: Thermocouple aging (after more than 2000 hours of use), solid-state relay (SSR) contact oxidation, PID parameter drift.
Solution: Replace the thermocouple; Check the oxidation status of solid-state relay contacts and use a multimeter to check if the on/off frequency is normal; Calibrate PID parameters (increasing the integration time I value can reduce oscillations).

2. Malfunctions related to furnace doors and seals
The furnace door is not tightly sealed
Reason for malfunction: Inappropriate material (sealing material not resistant to high temperature and corrosion), structural design defects, long service life (aging of sealing parts).
Solution: Replace with high-quality sealing materials; Optimize the structural design of the box furnace and add sealing parts; Regularly maintain and inspect the sealing parts of the box furnace, and replace aging seals.
Furnace door malfunction
Reason for malfunction: The brick body of the furnace door falls off (poor masonry quality, thick brick joints; high humidity at the furnace door, severe thermal expansion of the brick body; loosening of the brick body due to impact on the furnace door), the furnace door is locally oxidized and damaged (cast iron furnace door is oxidized and damaged under high temperature for a long time, welded carbon steel furnace door becomes thinner or even damaged by oxidation), the furnace door is deformed (the furnace door structure is unreasonable or its strength and stiffness are poor), the furnace door frame is deformed (there is no expansion joint left between the refractory brick and the door frame; the middle temperature is too high, causing the deformation of the welded door frame to exceed the expansion joint and deform).
Solution: Improve the quality of bricklaying for the furnace door, control the brick joints within 1.5-2mm, use refractory mortar to lay bricks, and repair any partial detachment of the furnace door bricks. If the detachment is severe, the bricks should be rebuilt; For cast iron furnace doors, if they are severely burned, they should be replaced. If they are not severely burned, the damaged parts can be leveled and repaired using the method of embedding strips. For welded furnace doors, the damaged parts can be cut off and repaired by welding and grinding; Improve the structure of the furnace door, enhance the strength and rigidity of the furnace door itself, increase the water cooling device of the furnace door, reduce the temperature of the contact surface between the furnace door and the door frame. For welded furnace doors, thermal correction should be used, and replacement should be carried out in case of severe deformation; Insert a 20mm thick aluminum silicate refractory fiber blanket at the entire pivot position between the refractory brick and the door frame, and place a layer of 10-20mm (depending on the length of the furnace) aluminum silicate or alumina ceramic fiber blanket between the arch, furnace, and rear wall. Check for short circuits and rapid temperature increases in local areas. The cast iron door frame is deformed and cannot be repaired, replaced, and the steel plate door frame is removed and corrected to increase expansion joints.

3. Circuit and power supply related faults
Trip fault
Reason for malfunction: circuit overload, short circuit between heating wire and electric furnace, insufficient capacity of power main switch, incorrect wiring of leakage protection switch installed in the main power switch box.
Solution: Check if the circuit is overloaded. If there is an overload situation, reduce the load or upgrade the circuit; Open the interior of the furnace and inspect the heating wire around it; Replace the high-capacity switch; Check the circuit and make corrections.
Unable to turn on after power on
Reason for malfunction: The power supply does not meet the specifications, the neutral wire is not connected, and the limit switch is not tightened.
Solution: Connect a power supply that meets the specifications; Connect the neutral wire; Tighten the limit switch.
The heating switch is not turned on, but the temperature still rises
Reason for malfunction: The contacts of the AC contactor are stuck together and cannot be disconnected.
Solution: Replace the contactor.

4. Malfunctions related to furnace atmosphere
Unstable atmosphere concentration and atmosphere pollution
Reason for malfunction: Failure of atmosphere control system, untimely cleaning of furnace chamber, and low gas purity.
Solution: Ensure the normal operation of the atmosphere control system and promptly replace damaged atmosphere control equipment; Regularly clean the furnace chamber to avoid the accumulation of pollutants; Use high-purity gas to reduce the possibility of atmospheric pollution.

5. Other faults
Equipment abnormal noise
Reason for malfunction: Unstable placement of workpieces in the furnace or loose furnace components.
Solution: Immediately stop the machine for inspection, readjust the position of the workpiece or tighten any loose parts.
Control system malfunction (such as non illuminating display screen, unresponsive buttons, etc.)
Reason for malfunction: Abnormal power supply and wiring of the control system.
Solution: First check if the power supply and wiring of the control system are normal, and then contact professional personnel for maintenance.