1.The graphite rod with good uniformity of red heat in the heating part is selected. The difference of red heat uniformity of graphite rod will affect the uniformity of furnace temperature and shorten the service life of graphite rod. In the process of usage, the red heat uniformity of the rod will gradually become worse, which will lead to the fracture of graphite rod when it’s serious.

2.The higher the service temperature, the shorter the life of graphite rod. When the surface temperature of graphite rod exceeds 1500℃, the oxidation rate is accelerated and the life span is shortened. In the process of usage, we should try to avoid too high surface temperature of the graphite rod.

3.After the graphite rod is heated in the air, the surface will form a dense silicon oxide film. The silicon oxide film becomes an anti-oxidation protective film and plays an important role in prolonging the life of the graphite rod. As the temperature of the kiln changes, the intermittent usage can lead the protective film on the surface of the graphite rod to be cracked. The rupture of the protective film leads to the weakening of the antioxidant protection, which accelerates the increase of the resistance value of the graphite rod.

In order to ensure the temperature of the kiln to be stable and meet the requirements of rapid temperature rise, the matched electrical control system shall be provided with sufficient voltage adjustment allowance. The new graphite rod can meet the design and power of the kiln at low voltage. With the continuous usage, the resistance value of the graphite rod becomes larger. Then it is necessary to increase the use voltage accordingly to meet the design and power of the kiln.

Voltage margin value: the voltage of graphite rod in the later stage of use is 1.5~1.7 times of that of the new rod. According to the difference of voltage regulation mode and connection mode, the upper limit of voltage in the later stage is usually 220V or 380V.

Adjustment mode of graphite rod power: It is suggested that the power should be adjusted by adjusting the voltage. As for the voltage adjustment mode of graphite rod, thyristor voltage regulator or voltage regulator is recommended to regulate voltage. Generally speaking, the voltage is not adjusted by changing the cycle number of the power regulator.

4.In general, the surface load density of graphite rod is obtained by the relationship between the temperature of furnace and the temperature of graphite rod surface. It is suggested that the power of graphite rod with maximum surface load density of 1/2~1/3 should be used. The higher the current added to the graphite rod, the higher the surface temperature of the graphite rod. It is recommended to use the smallest surface load density (power).

Please note that the value recorded at the cold end of the graphite rod is the current and voltage measured in the range of 1050℃±50 ℃ in the air, which might not be consistent with the actual use.

5.When continuously using graphite rod, it is hoped that the voltage can be increased slowly to maintain a long life.

Graphite rods should be kept in parallel circuit as much as possible. When the graphite rod is connected in series, the load will mainly gather on the graphite rod with high resistance, which will lead to the rapid increase of resistance and shorter life of the graphite rod.

At the same time, the matching of resistance value of graphite rod should be strengthened, that is to say, the resistance value of the same group of graphite rod should be as close as possible. Generally speaking, the deviation of resistance value of the same-group graphite rods in parallel circuit should be within 10%~15%, and the deviation of resistance of the same-group graphite rods in series circuit should be within 5%~10%. The higher the furnace temperature, the smaller the deviation of the required resistance value.

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