JPS6289820A - Method for diagnosing apparatus in continuous annealing furnace - Google Patents

Abstract

PURPOSE:To automatically and exactly diagnose deterioration of heating capacity of a heating zone and abnormalities of various sensors without troubling a person, by calculating summarized heat transfer coefft. of furnace and monitoring it. CONSTITUTION:Detection siganls of each sensor 4 in furnace, a strip (steel strip) temp. sensor 5 and a line speed sensor 6 in the heating zone 1 of furnace, density rho, width W, strip thickness (t), specific heat Cp, Stefan boltzmann constant delta of a steel strip 2 and set values from a circuit 7 for setting line pass length X of furnace are inputted to an arithmetic unit 8. Here, summarized heat transfer coefft. of furnace is calculated from a prescribed heat transfer formula. When furnace inside temp., steel strip temp in the temp. in the zone 1 are exactly detected, and heat transfer model of heating zone including emission ratio of steel strip is established, the calculation decides whether the heating zone is in stationary state or not and is carried out at the station ary state. The calculated value is stored in the unit 8 and the difference value between the value and the prescribed prestored reference value is calculated. Thus, by storing the result in a computer 9 in order, abnormal operation due to abnormalities in furnace state and each sensor, etc., can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for diagnosing equipment for a continuous annealing furnace that continuously anneales strips such as copper strips, and in particular, a method for diagnosing the deterioration of the heating capacity of the heating zone and various sensors. This system is designed to accurately diagnose abnormalities, etc.

[Conventional technology]

In the heating zone of a conventional continuous annealing furnace, the heating means (
Normally, there is no system that specifically monitors changes over time in the heating capacity of radiant tube burners (radiant tube burners). It is common to do some research.

[Problem that the invention seeks to solve]

However, in the conventional continuous annealing furnace equipment diagnosis method described above, the radiant tube and furnace body are inspected during periodic inspection work, so it takes a lot of time to inspect the radiant tube and furnace body in all heating zones. The problem was that it required a lot of effort and time.

Moreover, the presence or absence of cracks in the radiant tube can be determined by measuring the co and co□ concentrations in the furnace atmosphere gas. In other words, it is possible to detect that a crack has occurred in the radiant tube when the co, co□ concentration becomes higher than a predetermined set value. It was not possible to detect whether there was a fish or not, and in the end we had no choice but to inspect each radiant tube one by one.

Therefore, the present invention was made by focusing on the problems of the conventional method described above, and by calculating the overall heat transfer coefficient of the furnace in the operating state of the continuous annealing furnace and monitoring this, the heating capacity of the heating zone can be determined. The purpose of the present invention is to provide an equipment diagnosis method for a continuous annealing furnace that can accurately diagnose deterioration of the annealing furnace, abnormality of various sensors, etc.

[Means for solving problems]

In order to achieve the above object, the present invention provides a method in which the furnace temperature and strip temperature of the heating zone in a continuous annealing furnace are accurately detected, and a heat transfer model of the heating zone including the emissivity of the strip is established. When the heating zone is in a steady state, it is determined whether or not the heating zone is in a steady state, and when it is in a steady state,
At that time, the furnace temperature actual value, strip temperature actual value, and line speed actual value are measured respectively, and based on these, the overall heat transfer coefficient φCG of the furnace is calculated, and the overall heat transfer coefficient φ, 6
It is characterized by diagnosing deterioration of the heating capacity of the heating zone, abnormality of various sensors, etc. by monitoring changes over time.

[Effect]

In this invention, when the heating zone of the continuous annealing furnace is in a steady state, that is, when there is no change in the furnace temperature and line speed, and when the furnace exit temperature of the strip is within the allowable variation, The internal temperature actual value, strip temperature actual value, and line speed actual value are each measured, and based on these, the overall heat transfer coefficient φc6 of the furnace is calculated, and the difference value between this overall heat transfer coefficient φCG and the reference value is set as a predetermined value. If it exceeds the range, it is determined that an abnormality has occurred at the detection end of the temperature sensor, speed sensor, etc. Also, for example, the average value of the overall heat transfer coefficient φCG on a monthly basis is calculated, and this average value is calculated. When the value is below the lower limit of the predetermined setting range, it can be determined that a decrease in combustion efficiency, an increase in heat dissipated from the furnace body, etc. are occurring due to deterioration of equipment such as radiant tubes.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, reference numeral 1 denotes a heating zone that constitutes a part of a continuous annealing furnace for continuously annealing a strip 2 such as a steel strip. They are alternately wrapped around each other and transferred at a predetermined speed to be heated.

The inside of the furnace of the heating zone 1 is divided into a plurality of i zones (not shown), and a furnace temperature sensor 4 for detecting the furnace temperature T 2 i is provided for each zone. A strip temperature sensor 5 detects the temperature Ts of the strip 2 at
Further, a line speed sensor 6 for detecting the transfer speed (line speed) of the strip 2 is provided on the inlet side of the heating zone l.

Then, each furnace temperature sensor 4, strip temperature sensor 5
and the detection signal of the line speed sensor 6, the density ρ9 of the strip 2, the width W, the plate thickness t, and the specific heat Cp.

The Stefan Boltzmann constant σ and each setting value from a setting circuit 7 for setting the line path length X of the furnace are supplied to an arithmetic unit 8.

This calculation device 8 is composed of, for example, a microcomputer, and calculates the overall heat transfer coefficient φca of the furnace according to the following heat transfer equation (1) that is established in the heating zone 1 of the continuous annealing furnace based on each of the detection signals and set values. calculate.

・・・・・・・・・・・・(1) Here, ρ is the density of strip 2, Cp is the specific heat of the strip, t is the thickness of the strip, ■ is the line speed, Tz
is the furnace temperature and Ts is the strip temperature.

σ is the Stefan Boltzmann constant, and X is the line path length of the furnace.

In addition, the strip temperature T at the entrance of heating zone 1 of the continuous annealing furnace
Assuming that s is room temperature (20℃), and ρ=7 8 5 0
kg/m', W=1000mm,
t=o, 4u+.

V = 350m/min, φCG = 0.32
7 kcal/m”m1n('C)', Tz
= 820°C, X = 210m, σ = 4.88, and Cp varies depending on the strip temperature and carbon content, but is, for example, 0.112 kcal/kg at 0 to 50°C.

The temperature increase curve of the strip 2 in the furnace calculated based on equation (1) at 700 to 750° C. and 0.264 kcal/kg is shown in FIG.

As is clear from this Figure 2, heating zone 1 of the continuous annealing furnace
The temperature of the strip 2 gradually increases hyperbolically from the inlet to the outlet, reaching the target temperature (approximately 700° C.) near the outlet.

In addition, in order to accurately determine the overall heat transfer coefficient φCG in the calculation device 8, there must be no change in the line speed V and furnace temperature Tz, and the furnace outlet temperature Ts of the strip 2 must be within a preset allowable range. It is determined whether or not the furnace is in a steady state (stable state), and if the determination result is in an unsteady state, the overall heat transfer coefficient φCG is not calculated,
Only when in a steady state, the detection value V of each sensor at that time
, Tz, Ts and predetermined set value P+ W+ t+
The overall heat transfer coefficient φ is calculated by back calculating the above equation (1) based on Cpr σ+X. G, is calculated and stored in the memory within the arithmetic unit 8.

Next, the overall heat transfer coefficient φCG stored in this memory
m and a predetermined reference value φC that is also stored in advance in the memory.
A difference value D (=φCG+++−φCGO) with respect to GO is calculated, and the calculation result is output to, for example, the computer 9 and stored in the memory within the computer 9. Here, the overall heat transfer coefficient φCG,
The reference value φCGO is accurately calculated based on equation (1) immediately after new installation or major remodeling of the heating zone 1 of the continuous annealing furnace, and this is stored in the memory in the arithmetic unit 8.

In this way, the overall heat transfer coefficient φC in steady state
By sequentially storing the difference value between the heat transfer coefficient and the reference value φCGO in the computer 9, changes in the difference value due to fluctuations in the overall heat transfer coefficient φCGm can cause changes in the furnace status and abnormalities at the detection end of each sensor, etc. The resulting abnormal operation can be detected.

That is, for example, the reference value φ of the overall heat transfer coefficient. ,.

is 0.28, and the difference value from the actually calculated overall heat transfer coefficient φCGM varies by ±0.02, the temperature Ts of the strip 2 at the outlet side of the heating zone 1 changes by ±1
This will have an effect of 0°C.

Therefore, in normal operation, the differential value can be controlled within a control range of ±0.02, but for example, during the processing of one coil of strip 2, there is always one steady state, and the overall heat transfer coefficient Assuming that φCGm can be calculated and the calculation of the difference value can always be executed, if the condition in which the difference value exceeds the control area continues, for example, five or more times, the furnace temperature sensor 4. Strip temperature sensor5. Since it can be determined that there is a possibility that an abnormality has occurred in the detection end of the line speed sensor 6, etc., the computer 9 outputs an alarm to the alarm circuit 10 indicating that there is a possibility of an abnormality in the detection end. Alternatively, the range of ±0.04 of the difference value is set as the detection end abnormality determination area, and if there is a possibility of deviation from this area, a detection end abnormality warning is immediately output from the computer 9 to the alarm circuit 10.

In this way, abnormalities at the detection end can be diagnosed by observing changes in the difference value over a short period of time, but changes in the heating capacity of the heating zone, such as radiant tube deterioration, can occur over a long period of time. Therefore, the computer 9 calculates the monthly average value of the n difference values sequentially stored in its memory based on the following equation (2).

Then, the average value is sequentially stored in the memory of the computer 9, and the average value is, for example, the lower limit of the allowable range (-0) twice in a row.
, 02), it is determined that deterioration such as cracks has occurred in equipment such as radiant tubes, and an alarm signal is output from the computer 9 to the alarm circuit 10 to intensify inspection of these equipment. Here, we focus only on the lower limit of the allowable range because the overall heat transfer coefficient φC decreases due to a decrease in combustion efficiency due to equipment deterioration, an increase in heat dissipated from the furnace body, etc., and the differential value decreases. , this overall heat transfer coefficient φ. . By monitoring the difference between the reference value φCGm and the reference value φCGm, it is possible to diagnose whether or not the heating capacity has deteriorated due to deterioration of equipment such as the radiant tube.

In the above embodiment, a case has been described in which an alarm signal is output when the abnormality of the detection end and equipment deterioration deviate from the permissible range five times and twice in a row.
(These are not limited to these, but can be arbitrarily set depending on the equipment of the heating zone 1 of the continuous annealing furnace.

Furthermore, in the above embodiment, a case has been described in which the arithmetic unit 8 and the computer 9 are used to diagnose whether equipment deterioration in the heating zone 1 of the annealing furnace and abnormality at the detection end has occurred. However, the calculation device 8 and the computer 9 can be configured by one calculation processing device.

〔Effect of the invention〕

As explained above, according to the present invention, when the heating zone of the continuous annealing furnace is in a steady state, the overall heat transfer coefficient φ
CG is calculated by detecting the actual furnace temperature value, actual strip temperature value, and strip transfer speed, and by monitoring changes over time in this overall heat transfer coefficient φCG, equipment deterioration in the heating zone and detection end By diagnosing whether or not an abnormality has occurred, it is possible to automatically diagnose both equipment deterioration and detection end abnormalities during operation without the need for human intervention, making it easier to determine when to improve equipment. It can be used effectively, and therefore, it is possible to prevent deterioration of product quality due to abnormal operation.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between the line path length and strip temperature in the heating zone of a continuous annealing furnace, and Fig. 3 is the overall heat transfer coefficient and its standard. It is a graph showing the relationship between the difference value and time. In the figure, 1 is a heating zone of a continuous annealing furnace, 2 is a strip, 3 is a hearth roll, 4 is a furnace temperature sensor, 5 is a strip temperature sensor, 6 is a line speed sensor, 7 is a setting circuit, 8 is a calculation device, 9 is a computer, and 10 is an alarm circuit.

Claims (1)

[Claims] When the furnace temperature and strip temperature of the heating zone in a continuous annealing furnace are accurately detected, and a heat transfer model of the heating zone including the emissivity of the strip has been established, the heating zone is in a steady state. Determine whether or not there is, and when the condition is steady, measure the actual furnace temperature, strip temperature, and line speed at that time, and calculate the overall heat transfer coefficient φ_C_G of the furnace based on these. A method for diagnosing equipment for a continuous annealing furnace, characterized in that deterioration of the heating capacity of the heating zone, abnormalities of various sensors, etc. are diagnosed by monitoring changes over time in the overall heat transfer coefficient φ_C_G.