The furnace lining of a high-temperature electric furnace is essentially the wall of the furnace. It goes without saying that the furnace lining is a crucial component in a high-temperature electric furnace. Its thickness and quality significantly impact the furnace's performance. The lifespan of the furnace lining directly influences the overall lifespan of the electric furnace. How do you measure the thickness of a high-temperature electric furnace's lining? Let the editors at Star鼎 introduce you to this below.
　　

Section 1: High-Temperature Furnace Lining Thickness Inspection Method

Resistor Testing

　　
The resistance detection method involves embedding resistance elements within the furnace lining, aligning the sensor at the front with the inner surface of the lining, and then connecting them to the measurement system via wires. The resistance value of the resistance elements is related to their length. As the resistance elements synchronize with the wear of the furnace lining, the resistance changes accordingly. By measuring the electrical signal output by the elements with a corresponding measuring instrument, the remaining thickness of the furnace lining can be measured online.

2. Capacitance Testing

　　
Capacitance detection is similar to resistance methods, involving the installation of coaxial circular capacitor sensors within the furnace lining. The capacitance value corresponds to the length, allowing the thickness of the blast furnace lining to be determined by measuring the capacitance.
　　

3. Model Inference Detection

　　
Primarily utilizing thermocouples as detection elements, a thermodynamic-based mathematical model for the furnace and bottom temperatures is established. By employing software programming and numerical analysis methods, the approximate locations of the ironwater solidification line and carbon brick erosion line can be calculated.
　　

4. Ultrasonic Testing

　　
This method employs the characteristics of ultrasound propagation in solid media for detection. At a certain temperature, ultrasonic waves are introduced into the furnace lining and enter the furnace, utilizing the propagation time of the ultrasound as it reflects within the furnace lining to determine the remaining thickness of the lining.
　　

5. Multi-head thermocouple detection

　　
The multi-point thermocouple detection method involves installing multiple thermocouples of varying lengths within a protective sleeve, which is then placed inside the brick lining to be inspected. By measuring the temperature changes of each thermocouple, the erosion condition of the masonry can be inferred. When the temperatures at various points and the temperature gradients between them stabilize, as the brick lining erodes gradually to a certain area, the thermocouple at that location will be damaged, leading to abnormal temperature signals.
　　

6. Heat Flow Detection

　　
Thermal flux intensity is determined by temperature difference, thermodynamics, thermal conductivity coefficient, and furnace wall thickness. For the refractory lining of high-temperature electric furnaces, the thermal conductivity coefficient is constant. The furnace wall thickness can be obtained by temperature difference and thermal flux intensity. The main method is to install thermal flux detection sensors in the cooler parts of the lining, then cool the wall water temperature difference through the hearth, calculate the thermal flux intensity, and combine it with the temperature values measured by the thermocouples within the brick lining to determine the furnace wall thickness.
　　

7. Stress Wave Detection

　　
Stress wave signals are highly sensitive to structural defects. When stress waves propagate through a medium, they encounter discontinuities such as cracks or holes, leading to refraction, reflection, scattering, and mode conversion. Therefore, the characteristics of stress waves can be utilized to determine the thickness of the cooling wall material.
　　
The above detection of the refractory lining thickness shows that it has a certain impact on the life of the furnace and the electric furnace itself. Similarly, proper maintenance can also extend the service life of the refractory lining and the electric furnace. Let's take a look at how to maintain a high-temperature electric furnace now!
　　

Section Two: Maintenance Methods for High-Temperature Furnace Lining

　　
Before use, inspect the furnace lining. If longitudinal cracks are found in the high-temperature furnace lining, adopt a slow heating method to allow the cracks to close before melting.
　　
When horizontal cracks appear in the furnace wall, fine refractory powder can be filled into the cracks as per actual conditions, followed by adding material for melting.
　　
When the furnace bottom is eroded, it can be repaired with furnace lining material. After the repair, remember to cover it with a metal plate, then add metal furnace charge and melt it at low power for a while before switching to full power melting.
　　
4. Maintenance and care of the furnace lining should be conducted when the furnace is cold. Electric furnaces should be allowed to cool naturally or use a water cooling system; spray cooling is strictly prohibited.
　　
After the melting process is complete, the molten iron can be kept warm by adding an asbestos board over the furnace mouth to prevent cracks from forming on the furnace wall.
　　
6. Upon reactivation after a long-term shutdown, the furnace should be slowly heated to melt, which allows the minor cracks in the refractory lining to naturally heal.
　　
That concludes our explanation on how to measure the thickness of a high-temperature furnace lining. As detailed above, the methods for thickness measurement include resistance testing, capacitance testing, model inference testing, ultrasonic testing, multi-head thermocouple testing, heat flow testing, and stress wave testing. The thickness significantly affects both the furnace lining and the electric furnace, and proper maintenance is crucial during use to extend the lifespan of the furnace. Luoyang Xingding Kiln Co., Ltd. produces high-quality high-temperature furnaces and linings with diverse specifications and timely after-sales service. Feel free to call or leave a message for inquiries at any time.

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