Estimation of economic life of 0Cr25A15 electric heating body for high temperature resistance furnace

High-temperature resistance furnace with 0Cr25A15 electric heating body economic life calculation bookmark0 paragraph Weihua Hou Yingjie Table 1 use time quarter 1234567 failure times 24371711 month average number 0.671.3811.672.3323.67 maintenance cost month for industrial high-temperature resistance furnace electric heater, 0Cr25A15 due to resistance The utility model has the advantages of high rate, small temperature coefficient of resistance, high surface power allowable, high temperature oxidation resistance, strong corrosion resistance against sulfur and anti-carbon hydrogen atmosphere, and the like, and is widely used. However, the material has the disadvantages of poor cold workability, brittle hardness, and high strength drop at high temperatures, making its service life difficult to predict, resulting in premature or late replacement of the electric heater. Since the electric heating body is generally about 10* of the whole furnace cost, it is very important to correctly predict the economic life of the whole furnace to reduce maintenance costs and improve economic efficiency.

Taking the economic life measurement of 0Cr25A15 electric heating body used in 350kW step-type quenching heating resistance furnace of Kunming Leaf Spring Co., Ltd. as an example, the method and argument of economic life measurement of 0Cr25A15 electric heating body for general high-temperature resistance furnace are proposed.

Working mode: continuous operation for 24 hours; installation position of electric heating body at least continuous working: bottom surface of furnace, wall on both sides and end wall of furnace.

Electric heating body winding method: strip corrugated shape.

Statistical analysis of the failure of the 0Cr25A15 electric heater during use is performed in units of 3 months. Seen from the fault-time curve, the failure performance basically conforms to the mechanical failure law. Early failures were mainly affected by manufacturing quality. After 2.5 years of use, the frequency of failure of the electric heaters increased significantly. The main reason is that the electric heating body working at high temperature causes the conductive cross-sectional area of ​​the electric heating body to decrease due to high-temperature oxidation, and the unit surface power increases to cause a failure.

Due to the accumulation of scale on the bottom surface of the furnace, the electric heater is short-circuited, causing an increase in local resistance and a high-temperature circuit.

The electric heating body breaking part and the electric heating body and the extraction rod are repaired and repaired many times, and local grain coarseness is formed in the welding area, the resistivity is changed, the reliability is lowered, and the failure rate is remarkably increased.

The total cost of the furnace electric heater is 138,000 yuan.

Among them: the material cost of 12.25 million yuan is 350kg of electric heating material, the material price is calculated according to the current market price of 35 yuan/kg); the auxiliary material fee is 350 yuan including welding rod, connecting plate, etc.); the working time fee is 480 yuan, and the replacement is required for four people. , completed in 3 days).

Among them: the empty furnace heating fee of 560 yuan after each maintenance, the furnace temperature rises to the normal working temperature for 4h, the electricity price is calculated according to 0.4 yuan / kW * h); the working hour fee is 40 yuan; the material fee is 40 yuan.

Depreciation of electric heaters. According to the calculation of 5 years, the monthly depreciation fee is based on the above calculations. The comparison table between the net value of electric heating body and maintenance cost is shown in Table 1).

It can be seen from Table 1 that after the two-and-a-half-year use of the electric heater used in the furnace, the common fault of the automatic transmission of the automobile, Wu Ruiqi Xiahui Wu Zhenduo, with the rapid development of the modern automobile manufacturing industry, the technology of the new automobile transmission has also produced The series is profoundly changing. The automatic transmission makes the shifting more precise and smooth, which not only improves the engine's power performance and fuel economy, but also makes the operation more comfortable and satisfactory, but the accompanying automatic transmission system failure also occurs.

Automatic transmission failures are often caused by hydraulic system failures, degraded engine operating conditions, and low supply voltages.

Diagnosing these faults begins with checking the hydraulic fluid level and the quality of the oil. First check the AFT liquid level, check the scale of the oil on the scale in the cold, warm and hot state while ensuring that the vehicle is parked horizontally. If the liquid level is too low, the air will enter the oil pump and combine with the oil, resulting in oil. Liquid separation, oil pressure is difficult to establish, even if the oil pressure is barely established, it will cause the gear shift due to too low. Air entering the pressure regulator also causes the regulator's valve to hum when adjusting the pump pressure. If the liquid level is too high, the oil will also decompose, causing foam, overheating or oxidation. The above problems will cause various valves, clutches and servos to malfunction. The leakage of oil from the transmission vents is a reliable basis for foam in the oil. According to statistics, 90% of transmission failures are caused by oil damage and oxidation. Check the contents of the oil sump and find light deposits. These black impurities usually come from the clutch and brake components. The magnet can be used to determine whether the particle powder in the precipitate is steel or aluminum. If it is steel powder, it means that there is severe wear or damage inside the transmission; if it is aluminum powder, it can be judged that the hydraulic clutch blade is worn.

The monthly maintenance cost has exceeded the net value, so its economic life is 2.5 years.

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