A pusher disc type continuous furnace safety control method

Abstract

This application relates to the field of pusher-type continuous furnaces and discloses a safety control method for pusher-type continuous furnaces. The method includes: acquiring the operating status parameters of the pusher-type continuous furnace; aligning the real-time gas pressure and the drive current value with timestamps; calculating a first rate of change of the real-time gas pressure and a second rate of change of the drive current value within a preset time window; calculating the ratio of the difference between the first rate of change and the second rate of change to obtain a pressure misalignment; generating a first-level safety command when the pressure misalignment is greater than a first preset misalignment threshold and less than a second preset misalignment threshold; and generating a second-level safety command when the pressure misalignment is greater than or equal to the second preset misalignment threshold. Through the above technical solution, the identification of pressure fluctuations caused by normal process advancement and actual sealing leakage faults can be achieved.

Description

Technical Field

[0001] This application relates to the field of pusher-type continuous furnaces, and more particularly to a safety control method for pusher-type continuous furnaces. Background Technology

[0002] The pusher-type continuous furnace is used for heat treatment processes such as carburizing, quenching, and tempering. The furnace chamber needs to be maintained at a high temperature for a long time and filled with a flammable protective gas. The pusher mechanism pushes the workpiece tray forward step by step along the slide rail at the bottom of the furnace chamber through periodic mechanical work, accompanied by the periodic opening and closing of the inlet and outlet furnace doors.

[0003] Existing safety control schemes are centered around PLCs, setting fixed alarm thresholds for status parameters such as gas pressure, furnace door displacement, and pusher stroke. When any parameter exceeds the threshold, the power source and gas supply are cut off. However, during normal process execution, mechanical actions can cause changes in the effective volume of the furnace, resulting in instantaneous fluctuations in gas pressure. Existing static threshold judgment logic cannot distinguish between these fluctuations caused by mechanical work and actual leakage faults.

[0004] Solving this technical problem is a technical challenge that needs to be overcome by those skilled in the art. Summary of the Invention

[0005] This application provides a safety control method for a pusher-type continuous furnace to at least partially solve the above-mentioned technical problems.

[0006] To achieve the above objectives, this application provides a safety control method for a pusher-type continuous furnace, comprising:

[0007] Obtain the operating status parameters of the pusher-type continuous furnace; the operating status parameters include the drive current value of the pusher actuator during the movement process and the real-time gas pressure inside the pusher-type continuous furnace;

[0008] The real-time gas pressure and the drive current value are timestamped;

[0009] Calculate the first rate of change of the real-time gas pressure within a preset time window and the second rate of change of the drive current value within the preset time window;

[0010] The pressure misalignment is obtained by calculating the ratio of the difference between the first rate of change and the second rate of change; the pressure misalignment is used to represent the degree of disturbance of the furnace airtightness by the mechanical displacement of the pusher actuator.

[0011] When the pressure imbalance is greater than a first preset imbalance threshold and less than a second preset imbalance threshold, a first-level safety command is generated; the first-level safety command is used to control the intermediate relay to suspend the power source input of the push plate actuator and trigger an alarm signal;

[0012] When the gas pressure misalignment is greater than or equal to the second preset misalignment threshold, a second-level safety command is generated; the second-level safety command is used to control the safety module to cut off all power source inputs of the pusher-type continuous furnace and shut off the gas valve.

[0013] In this embodiment of the application, the above technical solution calculates the gas pressure misalignment based on the driving current value and the gas pressure, and transforms the degree of disturbance of mechanical displacement to the furnace seal into an index that can be graded and judged, thereby realizing the identification of gas pressure fluctuations caused by normal process progress and actual seal leakage faults; when the gas pressure misalignment falls into different ranges, two levels of safety response are triggered: alarm and emergency shutdown, respectively, so that minor abnormalities and serious leaks are handled differently, reducing the probability of falsely triggering emergency shutdown.

[0014] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the steps of a safety control method for a pusher-type continuous furnace provided in an exemplary embodiment of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0018] This application provides a safety control method for a pusher-type continuous furnace, which is applied to the safety control system of the pusher-type continuous furnace. The system mainly consists of an industrial control computer, a PLC, a safety module, an input / output module, intermediate relays, and the pusher-type continuous furnace body.

[0019] The industrial control computer is deployed on the control room console and communicates with the PLC via Ethernet. It is responsible for the display of the human-machine interface, the setting and distribution of process parameters, and the monitoring and historical storage of operating data. The PLC is deployed in the electrical control cabinet and connects to the field sensors and actuators via digital and analog I / O modules, respectively. Specifically, the analog input terminals of the PLC are connected to the current transformer of the pusher actuator drive motor, the pressure sensor inside the pusher continuous furnace, the displacement sensor of the furnace door lifting mechanism, and the distributed temperature sensors of each section of the furnace, to collect drive current values, gas pressure, door gap height values, and segmented temperature data. The PLC is also connected to the emergency stop button and the safety door switch.

[0020] The PLC is also connected to the control coil of the intermediate relay and the trigger input of the safety module. The contacts of the intermediate relay are connected in series in the power source circuit of the pusher actuator to cut off the power source input of the pusher actuator when the first-level safety command is received. The safety module is a control unit integrating the functions of a safety relay and a safety-type PLC. It is set up independently of the conventional process control PLC. Its output is connected to the coil of a three-phase AC contactor and a gas solenoid valve to cut off all power source inputs of the pusher continuous furnace and shut off the gas valve when the second-level safety command is received. The pusher continuous furnace has a feeding section and a heat preservation section arranged sequentially along its length. The inner wall of the furnace is equipped with a protective gas inlet proportional valve and a flow meter.

[0021] During the operation of the pusher-type continuous furnace, the PLC continuously collects the drive current value and gas pressure. After timestamp alignment and change rate calculation, the gas pressure misalignment is obtained. Based on the comparison result of the misalignment and the classification threshold, the first-level safety command or the second-level safety command is output. The first-level safety command drives the intermediate relay to suspend the power source input of the pusher actuator and triggers the audible and visual alarm. The second-level safety command drives the safety module to cut off all power source input and shut off the gas valve.

[0022] This application provides a safety control method for a pusher-type continuous furnace. Please refer to [link / reference]. Figure 1 The safety control method for a pusher-type continuous furnace provided in this application includes the following steps:

[0023] Step 101: Obtain the operating status parameters of the pusher-type continuous furnace; the operating status parameters include the drive current value of the pusher actuator during movement and the gas pressure inside the pusher-type continuous furnace. Specifically, the pusher actuator is driven by a servo motor or a stepper motor, and the current signal of the motor winding is collected by a current transformer or a Hall current sensor, and the drive current value is obtained after analog-to-digital conversion; a pressure sensor is installed inside the furnace chamber of the pusher-type continuous furnace, and the gas pressure is obtained by measuring the pressure of the protective gas inside the furnace.

[0024] Step 102: Timestamp align the gas pressure and the drive current value. Specifically, since the drive current value and gas pressure are collected by different types of sensors at different sampling frequencies, the time base of the two data sources is offset; by constructing a sliding data buffer queue, the two heterogeneous data sources are unified onto the same time axis, so that the drive current value and gas pressure at the same moment are paired.

[0025] Step 103: Calculate the first rate of change of the gas pressure and the second rate of change of the drive current value within the preset time window. Specifically, the width of the preset time window is set according to the single pushing action cycle of the pusher actuator. Within this window, the rate of change of the gas pressure and the rate of change of the drive current value are calculated respectively. The first rate of change reflects the speed of fluctuation of the furnace gas pressure, and the second rate of change reflects the speed of change of the mechanical load of the pusher actuator.

[0026] Step 104: Calculate the ratio of the difference between the first rate of change and the second rate of change to obtain the pressure misalignment; the pressure misalignment is used to represent the degree of disturbance of the mechanical displacement of the pusher actuator to the furnace airtightness. Specifically, the larger the pressure misalignment, the more serious the deviation between the fluctuation of the gas pressure and the fluctuation of the drive current, that is, the mechanical displacement has caused disturbances to the furnace seal beyond the normal range.

[0027] Step 105: When the pressure imbalance exceeds a first preset imbalance threshold but is less than a second preset imbalance threshold, a first-level safety command is generated. The first-level safety command controls the intermediate relay to suspend the power input to the pusher actuator and trigger an alarm signal. Specifically, when the pressure imbalance falls within the range between the two threshold levels, it is determined that the pusher actuator is slightly stuck or the furnace seal is slightly deteriorated. At this time, a first-level safety command is generated. This command drives the intermediate relay through the PLC output to disconnect the power supply circuit of the pusher actuator motor, suspend the pusher action, and trigger the fault indicator light and buzzer on the control panel to output an audible and visual alarm signal, reminding the operator to pay attention and troubleshoot the abnormality.

[0028] Step 106: When the gas pressure imbalance is greater than or equal to the second preset imbalance threshold, a second-level safety command is generated. The second-level safety command is used to control the safety module to cut off all power source inputs to the pusher-type continuous furnace and shut off the gas valves. Specifically, when the gas pressure imbalance reaches or exceeds the second preset imbalance threshold, it is determined that there is a large-area damage and leakage in the furnace or severe sticking of the pusher. At this time, a second-level safety command is generated. This command is sent to an independent safety module, which hardwires to drive a three-phase AC contactor to disconnect all power source circuits and shut off the solenoid valves on the gas pipeline to prevent continuous leakage of combustible gas from causing a safety accident.

[0029] Through the above technical solution, the gas pressure misalignment is calculated based on the driving current value and gas pressure. The disturbance of mechanical displacement on the furnace seal is transformed into an index that can be graded and judged, thereby realizing the identification of gas pressure fluctuations caused by normal process progress and actual seal leakage faults. When the gas pressure misalignment falls into different ranges, two levels of safety response are triggered: alarm and emergency shutdown. Minor abnormalities and serious leaks are handled differently, reducing the probability of falsely triggering emergency shutdown.

[0030] In some embodiments, the operation status parameters of the pusher-type continuous furnace are obtained, the gas pressure and the drive current value are timestamped, and a first rate of change of the gas pressure and a second rate of change of the drive current value within a preset time window are calculated, including:

[0031] The driving current value is obtained by acquiring the current signal of the drive motor of the pusher actuator at a first preset sampling frequency; the gas pressure is obtained by acquiring the gas pressure signal at a second preset sampling frequency through a pressure sensor installed inside the furnace of the pusher continuous furnace.

[0032] A sliding data buffer queue is constructed; the acquired drive current value and gas pressure are continuously stored in the sliding data buffer queue; the data stored in the sliding data buffer queue is timestamped based on the lower of the first preset sampling frequency and the second preset sampling frequency; unaligned data with timestamp differences greater than a preset tolerance are discarded, and the aligned gas pressure and drive current value are output. Specifically, the sliding data buffer queue opens a circular buffer in the PLC's data storage area, and each sensor data is written with a system clock timestamp; timestamp matching uses the data sequence corresponding to the lower sampling frequency as an anchor point, and searches for the sampling point in the data sequence of the higher sampling frequency that is closest to the anchor point timestamp; if the timestamp difference between the two exceeds a preset tolerance, the data is determined to be unreliable and discarded; the preset tolerance is determined based on the sampling period of the two sensors, and its value does not exceed half of the sampling period corresponding to the lower sampling frequency.

[0033] Within the preset time window, the difference between the current value of the gas pressure and the initial gas pressure value at the start of the preset time window is calculated, and divided by the duration of the preset time window to obtain the first rate of change; the difference between the current value of the driving current and the initial current value at the start of the preset time window is calculated, and divided by the duration of the preset time window to obtain the second rate of change. Specifically, the first rate of change is equal to the gas pressure value at the end of the window minus the gas pressure value at the start of the window, divided by the window duration; the second rate of change is equal to the current value at the end of the window minus the current value at the start of the window, divided by the window duration. This difference quotient calculation method reflects the average change trend of the parameters within the window time span, avoiding interference from single-point noise on the rate of change estimation.

[0034] The above technical solution solves the problem of data phase shift caused by inconsistent sampling frequencies of heterogeneous sensors.

[0035] In some embodiments, calculating the ratio of the difference between the first rate of change and the second rate of change to obtain barometric displacement includes:

[0036] The reference current change rate and reference pressure change rate of the pusher-type continuous furnace under standard no-load conditions are obtained. Specifically, during the calibration stage before the pusher-type continuous furnace is put into operation, the furnace is in a no-load and sealed state. The pusher actuator is operated with standard process parameters to perform no-load pushing action, and the driving current value and gas pressure are collected. The current change rate and pressure change rate are calculated for the data collected during multiple no-load pushing processes, and the average value of multiple calculation results is taken as the reference current change rate and reference pressure change rate and pre-stored in the parameter area of ​​the PLC.

[0037] Dividing the first rate of change by the reference pressure rate of change yields the first relative change ratio. Specifically, the first relative change ratio reflects the deviation factor of the gas pressure change under the current operating condition from the no-load reference; when the furnace is well sealed, the pressure fluctuation caused by mechanical propulsion is close to the no-load reference, and the first relative change ratio approaches 1.

[0038] Dividing the second rate of change by the reference current rate of change yields the second relative change ratio. Specifically, the second relative change ratio reflects the deviation factor of the change in drive current relative to the no-load reference under the current operating condition; when the pusher actuator has no abnormal jamming, the second relative change ratio also approaches 1.

[0039] The absolute difference between the first relative change ratio and the second relative change ratio is calculated as the gas pressure misalignment. Specifically, when the furnace is well-sealed and the pusher plate is not stuck, both relative change ratios are close to 1, and their absolute difference is close to 0. When the furnace leaks, the rate of change of gas pressure deviates from the no-load reference much more than the rate of change of drive current, widening the gap between the first and second relative change ratios and increasing the absolute difference. Conversely, when the pusher plate is severely stuck but the seal is intact, the rate of change of drive current increases abnormally while the rate of change of gas pressure is relatively normal, and the gap between the two ratios also increases.

[0040] The above technical solution transforms the degree of abnormal deviation between air pressure and abnormal deviation between current into a judgment index, which can identify both abnormal air pressure drop caused by seal leakage and abnormal current rise caused by mechanical jamming.

[0041] In some embodiments, the method further includes:

[0042] The door gap height is obtained by acquiring the displacement sensor signal of the furnace door lifting mechanism. Specifically, the furnace door lifting mechanism is equipped with a displacement sensor in the form of a photoelectric encoder. The output signal is converted from analog to digital to obtain the displacement of the door. When the door is fully closed, the gap height is zero. When the door is raised, the gap height increases with the displacement.

[0043] Step 402: When the height of the door gap is greater than zero and less than the preset sealing critical height, the furnace door is determined to be in the open state. Specifically, the preset sealing critical height is determined based on the structural dimensions of the furnace door sealing strip. When the height of the door gap is greater than zero but less than this critical value, it indicates that the furnace door has moved out of the fully closed position but is not yet fully open. At this time, the furnace is connected to the outside atmosphere through the door gap, and the gas pressure will fluctuate due to pressure relief, which is unrelated to leakage.

[0044] Step 403: When it is determined that the furnace door is in the open state, the first relative change ratio is set to zero and a preset current weighting amplification coefficient is obtained. Specifically, the change in gas pressure during the furnace door opening is entirely caused by pressure relief rather than sealing failure. At this time, the first relative change ratio does not contain effective leakage diagnosis information, so it is forcibly set to zero to eliminate the interference of gas pressure change. The rate of change of the driving current value can still reflect the load status of the push plate actuator. The second relative change ratio is weighted based on the current weighting amplification coefficient to make up for the problem of loss after the first relative change ratio is set to zero.

[0045] Step 404: Multiply the second relative change ratio by the current weighting amplification factor to obtain the pressure imbalance adjustment to eliminate pressure fluctuation interference caused by pressure relief during furnace door opening. Specifically, when the furnace door is open, the pressure imbalance adjustment is determined solely by the amplified relative change ratio on the current side; if the pusher actuator jams during furnace door opening, the abnormally increased drive current value will cause the second relative change ratio to deviate significantly from the no-load reference, and the pressure imbalance adjustment amplified by the current weighting amplification factor can still reflect the mechanical abnormality.

[0046] Through the above technical solution, during the normal process stage of the furnace door's periodic opening and closing, by identifying the door's opening status and eliminating interference signals from the gas pressure side, the gas pressure fluctuations caused by furnace door depressurization are prevented from being misjudged as sealing leakage faults; the current weighting amplification coefficient enables the identification of mechanical jamming faults through abnormal changes in the drive current value even when the gas pressure diagnostic dimension is missing, ensuring the continuity of safety monitoring during furnace door opening.

[0047] In some embodiments, the operating status parameters further include the furnace temperature inside the pusher-type continuous furnace, and the method further includes:

[0048] The rate of change of the furnace temperature within the preset time window is calculated. Specifically, the furnace temperature is acquired by a thermocouple or resistance temperature detector (RTD) sensor. The difference between the current temperature value and the temperature value at the beginning of the preset time window is calculated to obtain the rate of change of temperature. The rate of change of temperature reflects the changing trend of the furnace heat load. The rate of change of temperature is relatively high in the heating section of the carburizing process and close to zero in the holding section.

[0049] The gas pressure is compensated based on the temperature change rate to obtain the aerodynamic pressure deviation. Specifically, when the furnace temperature changes, according to the ideal gas law, the pressure of the enclosed gas inside the furnace will change with the temperature. This pressure change caused by the thermodynamic effect is unrelated to sealing leakage and needs to be subtracted from the measured change in gas pressure.

[0050] The pressure shift caused by thermal expansion is obtained by calculating the product of the temperature change rate and the gas expansion constant. Specifically, the gas expansion constant is calculated and determined based on the furnace volume, the type of protective gas, and the initial operating parameters. This constant reflects the amount of gas pressure change caused by a unit temperature change rate. The product of the temperature change rate and the gas expansion constant is the contribution of the thermodynamic effect to the gas pressure within a preset time window. The gas expansion constant mentioned here can be obtained by solving the rated operating parameters according to the ideal gas law, and it is a coefficient characterizing the pressure change caused by the temperature change of the protective gas in the furnace under isochoric conditions.

[0051] Calculate the total pressure difference between the gas pressure at the current timestamp and the gas pressure at the beginning of the preset time window. Specifically, the total pressure difference is the gas pressure at the end of the window minus the gas pressure at the beginning of the window, including both pressure shifts caused by thermal expansion and pressure changes caused by leakage or mechanical disturbances.

[0052] The remaining difference obtained by subtracting the pressure offset from the total pressure difference is the aerodynamic pressure deviation. Specifically, the aerodynamic pressure deviation is equal to the total pressure difference minus the thermal expansion pressure offset, that is, the net pressure change after removing thermodynamic effects from the measured pressure change; this deviation only reflects abnormal pressure changes caused by seal leakage or mechanical disturbance, eliminating the interference of temperature changes on pressure.

[0053] The difference between the current value of the gas pressure and the initial gas pressure value at the start of the preset time window is replaced by the aerodynamic pressure deviation. Specifically, in the subsequent calculation of the first rate of change, the original difference in gas pressure is no longer used, but is replaced by the aerodynamic pressure deviation. The first rate of change reflects the rate of change of net gas pressure after temperature compensation.

[0054] The first rate of change after compensation is calculated by dividing the aerodynamic pressure deviation by the time span of the preset time window. Specifically, the first rate of change after compensation is equal to the aerodynamic pressure deviation divided by the window duration. This rate of change has eliminated the influence of temperature effects and can more accurately reflect the true changes in the furnace sealing state.

[0055] In one implementation, the gas expansion constant is calibrated through multiple heating and cooling cycles, and the average value of the ratio of temperature change rate to gas pressure change in each experiment is taken.

[0056] By subtracting the pressure deviation caused by thermal expansion due to temperature changes, the aerodynamic pressure deviation that only reflects sealing leakage or mechanical disturbance is obtained, thus eliminating the interference of thermodynamic effects on pressure loss during furnace heating and cooling. The pressure loss is calculated using the compensated first rate of change, which can accurately identify sealing abnormalities in process sections with large temperature changes.

[0057] In some embodiments, the operating status parameters further include the protective gas makeup flow rate of the pusher-type continuous furnace; before calculating the first rate of change and the second rate of change, the method further includes:

[0058] The flow rate count value of the protective gas inlet proportional valve is read, and the flow rate count value is integrally calculated by performing a definite integral operation on the flow rate count value within the preset time window to obtain the flow rate integral value. Specifically, a flow meter is installed on the protective gas inlet proportional valve pipeline, and the PLC reads the flow rate count value at a fixed period. Within the preset time window, the flow rate sampling sequence is numerically integrated, and the product of the flow rate value at each sampling point and the sampling period is accumulated to obtain the total amount of protective gas flowing into the furnace within the time window, i.e., the flow rate integral value.

[0059] Obtain the factory-preset no-load furnace volume constant and standard ambient atmospheric pressure constant. Specifically, the no-load furnace volume constant is obtained through geometric measurement or gas filling calibration when the equipment leaves the factory, and represents the volume of the enclosed space inside the furnace; the standard ambient atmospheric pressure constant is taken as the standard atmospheric pressure value, used to convert the flow volume into pressure increment.

[0060] The pressure gain is calculated by dividing the integral value of the flow rate by the unloaded furnace volume constant and multiplying it by the standard ambient atmospheric pressure constant. Specifically, the pressure gain represents the pressure increment accumulated in the furnace within a preset time window due to the replenishment action of the protective gas inlet proportional valve; this increment is entirely caused by external active gas replenishment and is unrelated to sealing leakage.

[0061] The true pressure value is obtained by subtracting the gas pressure gain from the gas pressure at the end of the preset time window. Specifically, the protective gas proportional-integral-derivative control loop increases the make-up gas flow rate when it detects a drop in furnace pressure, resulting in the measured gas pressure including a masking effect of leakage and make-up. After forcibly subtracting the gas pressure gain from the measured pressure, the true pressure value without make-up gas interference is obtained.

[0062] The current value of the gas pressure is replaced by the actual pressure value in the calculation of the first rate of change to eliminate pressure masking interference caused by external active gas replenishment. Specifically, the actual pressure value is substituted into the formula for calculating the difference quotient of the first rate of change, replacing the current value of the original gas pressure. The first rate of change reflects the rate of change of the net gas pressure in the furnace after deducting the gas replenishment effect.

[0063] By subtracting the pressure gain generated by the active gas replenishment from the protective gas proportional-integral-derivative control loop from the gas pressure, the pressure value reflecting the true state of furnace sealing is restored, eliminating the masking effect of simultaneous leakage and replenishment on leakage diagnosis and eliminating the risk of missed detection caused by gas replenishment masking.

[0064] In some embodiments, after obtaining the barometric displacement, the method further includes:

[0065] The current travel coordinates of the pusher actuator within the pusher-type continuous furnace are obtained, and the furnace section in which the current travel coordinates are located is determined. Specifically, the travel coordinates of the pusher actuator are detected by a motor encoder or a limit switch on the slide rail. According to the structural layout of the pusher-type continuous furnace, the furnace is divided into a feeding section and a heat preservation section along its length. When the current travel coordinates fall into different sections, the disturbance characteristics of mechanical displacement on the furnace gas pressure are different.

[0066] When the current travel coordinate is in the feeding section of the pusher-type continuous furnace, the first value is used as the position attenuation coefficient. Specifically, the feeding section is close to the furnace door, the furnace cross-section changes significantly and the sealing structure is relatively weak. When the pusher advances in this section, it causes strong disturbance to the furnace gas pressure. Therefore, a larger first value is used for the position attenuation coefficient to reduce sensitivity and avoid false alarms.

[0067] When the current travel coordinate is deep within the insulation section of the pusher-type continuous furnace, the second value is used as the position attenuation coefficient, wherein the first value is greater than the second value. Specifically, the furnace cross-section is stable and well-sealed deep within the insulation section, and the disturbance to gas pressure caused by the pusher's movement is relatively weak. Gas pressure anomalies of the same degree are more worthy of attention. Therefore, a smaller second value is used for the position attenuation coefficient to improve sensitivity and detect early anomalies.

[0068] The corrected pressure misalignment is obtained by multiplying the pressure misalignment by the position attenuation coefficient. Specifically, the corrected pressure misalignment is equal to the product of the pressure misalignment and the position attenuation coefficient, and the original pressure misalignment is scaled differently in different furnace sections.

[0069] The pressure misalignment is replaced by a corrected misalignment. Specifically, subsequent comparisons with the first and second preset misalignment thresholds both use the corrected misalignment, and the triggering conditions for the graded safety command are adjusted differently based on the section where the push plate is located.

[0070] Through the above technical solution, a position attenuation coefficient is introduced based on the position of the pusher actuator in the furnace to perform zoned correction of gas pressure misalignment. Sensitivity is reduced in the feeding section where mechanical disturbance is strong to suppress false alarms, while sensitivity is increased in the insulation section where mechanical disturbance is weak to enhance early fault identification capability. The response characteristics of safety monitoring are matched with the operating characteristics of each section of the furnace, thereby improving the accuracy of judgment.

[0071] In some embodiments, the step of obtaining the position attenuation coefficient further includes:

[0072] When the current travel coordinate is deep within the insulation section and the furnace temperature exceeds a preset high-temperature threshold, the temperature difference between the furnace temperature and the preset reference temperature is obtained. Specifically, the operating temperature is higher deep within the insulation section. When the furnace temperature exceeds the preset high-temperature threshold, the furnace material deforms due to thermal expansion, causing the sealing gap to deform. The correlation between mechanical displacement and air pressure fluctuation deviates from the calibration reference under normal temperature conditions. The temperature difference is equal to the current furnace temperature minus the preset reference temperature, reflecting the degree to which thermal expansion deviates from the calibration conditions. The preset high-temperature threshold mentioned here is determined based on the linear expansion coefficient of the furnace material and the sealing gap tolerance. It refers to the temperature threshold at which the thermal expansion effect of the furnace material begins to have a non-negligible impact on the sealing gap.

[0073] Based on a preset correction coefficient mapping table, the correction factor corresponding to the temperature difference value is retrieved. Specifically, the correction coefficient mapping table is pre-stored in the parameter area of ​​the PLC, and the table records the discrete correspondence between different temperature difference values ​​and correction factors; based on the currently calculated temperature difference value, the corresponding correction factor is obtained from the mapping table through linear interpolation or by looking up the nearest value.

[0074] The correction factor is multiplied by the position attenuation coefficient to obtain the temperature-compensated corrected position attenuation coefficient. Specifically, the correction factor performs a second correction on the position attenuation coefficient in the temperature dimension. When the temperature difference increases, the correction factor changes accordingly, adjusting the scaling of the position attenuation coefficient to compensate for the effect of thermal expansion on the sealing gap.

[0075] The corrected position attenuation coefficient is used to replace the original position attenuation coefficient in calculating the corrected misalignment. Specifically, when calculating the corrected misalignment, the temperature-compensated corrected position attenuation coefficient is used instead of the original position attenuation coefficient, so that the corrected misalignment can still accurately reflect the degree of sealing abnormality under high-temperature conditions.

[0076] In one implementation, the correction coefficient mapping table is recalibrated after each furnace overhaul through an unloaded heating experiment. The pusher action is performed at different steady-state temperatures, and the ratio of gas pressure fluctuation to current fluctuation is recorded. New mapping table entries are generated based on the change in the ratio.

[0077] In another implementation, when the furnace temperature is lower than the preset high temperature threshold, the correction factor is set to 1, that is, no temperature correction is applied to the position attenuation coefficient. In this case, the position attenuation coefficient only reflects the influence of spatial position.

[0078] Through the above technical solution, a correction factor is introduced into the high-temperature section deep in the middle of the insulation section to compensate for the temperature attenuation coefficient of the position, thereby eliminating the influence of the deformation of the sealing gap caused by the thermal expansion of the furnace body material on the judgment of gas pressure loss.

[0079] In some embodiments, the method further includes, prior to generating the first-level security instruction:

[0080] Read the historical pressure loss schedule set within the historical safe operating cycle. Specifically, the historical safe operating cycle refers to the normal operation record of the equipment without triggering any safety commands during the period from the last major overhaul to the present; within this cycle, the PLC continuously records the pressure loss schedule value corresponding to each push plate action, forming the historical pressure loss schedule set.

[0081] The maximum value in the historical pressure loss set is extracted as the basic benchmark value. Specifically, the maximum value in the historical pressure loss set represents the extreme upper limit of pressure loss under normal operating conditions. This value reflects the maximum disturbance of mechanical propulsion to the furnace seal under fault-free conditions. Using this value as a benchmark ensures that the threshold setting is not lower than the extreme case of normal fluctuations.

[0082] The first preset out-of-service threshold is obtained by multiplying the baseline value by a first safety factor; the second preset out-of-service threshold is obtained by multiplying the baseline value by a second safety factor greater than the first safety factor. Specifically, the first safety factor and the second safety factor are empirical constants. The value of the first safety factor is such that the first preset out-of-service threshold is slightly higher than the extreme value under normal operating conditions, and the value of the second safety factor is such that the second preset out-of-service threshold is significantly higher than the first preset out-of-service threshold. The difference between the two safety factors determines the margin between minor anomalies and serious faults. Its value is determined according to the equipment safety level requirements and process characteristics and is adjusted through trial operation verification after commissioning.

[0083] In one implementation, the historical air pressure scheduling set is updated monthly. At the end of each month, the normal operation data for that month is added to the set and the threshold is recalculated to achieve periodic iterative optimization of the threshold.

[0084] The above technical solution calculates the grading threshold based on the equipment's historical safe operation data, replacing the method of manually setting fixed thresholds. The threshold is adjusted according to changes in equipment status and process parameters. The threshold is determined by multiplying the historical maximum misoperation by a safety factor, ensuring that safety commands will not be triggered erroneously under normal operating conditions.

[0085] In some embodiments, the method further includes:

[0086] Multiple temperature sensors, distributed along the length of the furnace chamber of the pusher-type continuous furnace, acquire segmented temperature data for each segment. Specifically, a temperature sensor is installed at fixed intervals along the length of the furnace chamber, with each sensor covering one segment. The measured values ​​from each sensor are converted from analog to digital and then fed into the PLC to form temperature distribution data along the length of the furnace chamber.

[0087] The temperature difference between two adjacent segmented intervals is calculated to generate a temperature gradient distribution sequence. Specifically, the temperature difference between adjacent segmented intervals is calculated sequentially along the length of the furnace to form a temperature gradient distribution sequence; this sequence reflects the steepness of temperature change in each section of the furnace, and under normal operating conditions, the temperature gradient of each section should be consistent with the process setting curve.

[0088] When the maximum temperature difference in the temperature gradient distribution sequence exceeds a preset gradient fluctuation threshold, an early warning signal is output for localized abnormal overheating in the furnace. Specifically, when the maximum temperature difference in the temperature gradient distribution sequence exceeds the preset gradient fluctuation threshold, it indicates that there is a localized abnormal temperature rise in a certain segment, which may be caused by heating element malfunction, cooling system failure, or localized overheating of the workpiece. At this time, an early warning signal is output, displaying the location of the abnormal segment and the temperature difference on the industrial control computer interface. The preset gradient fluctuation threshold mentioned here is determined based on the allowable temperature uniformity deviation of the process.

[0089] In one implementation, the calculation results of the temperature gradient distribution sequence are displayed in the form of a heat map on the industrial computer human-machine interface, allowing operators to intuitively observe the temperature distribution in the furnace.

[0090] In another implementation, the warning signal is simultaneously pushed to the mobile terminal to remind maintenance personnel who are not near the control panel to pay attention in time.

[0091] In some embodiments, the correction coefficient mapping table is generated through the following steps:

[0092] A historical dataset of mechanical displacement and gas pressure fluctuations at different furnace temperatures during a historical safe operating cycle is obtained. Discrete relationship nodes are extracted from this historical dataset, and correction factors corresponding to each temperature difference value are generated through fitting. A correction coefficient mapping table is constructed and pre-stored in memory. Specifically, during a historical safe operating cycle, the PLC records the mechanical displacement and corresponding gas pressure fluctuations of the pusher actuator for each pushing action at different furnace temperatures, forming a historical dataset of temperature, displacement, and gas pressure. Discrete relationship nodes for different temperature ranges are extracted from this dataset, and correction factors corresponding to each temperature difference value are generated through polynomial fitting or piecewise linear interpolation. A mapping table is constructed and written to the PLC storage area.

[0093] In some embodiments, before performing timestamp matching on the data stored in the sliding data cache queue, the method further includes:

[0094] Obtain the average fluid conduction velocity of the gas inside the pusher-type continuous furnace. Specifically, the average fluid conduction velocity is related to the gas type, furnace temperature, and pipe geometry, and can be estimated using gas dynamics formulas or obtained through field measurements during the calibration phase.

[0095] The fixed installation coordinates of the pressure sensor within the pusher-type continuous furnace are obtained, as well as the current travel coordinates of the pusher actuator. The three-dimensional straight-line distance between the fixed installation coordinates and the travel coordinates is calculated as the spatial distance. Specifically, the pressure sensor is installed at a fixed position on the inner wall of the furnace, and the travel coordinates of the pusher actuator change as the pusher advances. The three-dimensional straight-line distance between the two is calculated using the Euclidean norm of the coordinate difference, which reflects the geometric path length of the pressure wave propagating from the pusher position to the sensor position.

[0096] The aerodynamic wave delay time is calculated by dividing the spatial distance by the average fluid conduction velocity. Specifically, the aerodynamic wave delay time is equal to the spatial distance divided by the average fluid conduction velocity, representing the time required for the pressure disturbance generated by the push plate actuator to propagate to the pressure sensor; this delay time varies with the push plate stroke coordinates, and the further the push plate is from the sensor, the greater the delay.

[0097] The timestamps of the gas pressure in the sliding data buffer queue are uniformly subtracted from the pneumatic wave delay time to achieve time phase compensation between the driving current value and the gas pressure. Specifically, pressure propagation has a transmission delay, and there is a time difference between the mechanical action of the pusher actuator and the pressure sensor reading at the same moment. By shifting the gas pressure timestamp forward by the length of the pneumatic wave delay time, the driving current value and the gas pressure are aligned causally, that is, the change in mechanical load generated by the pusher actuator at a certain moment corresponds to the change in gas pressure propagated to the sensor after the delay.

[0098] The above technical solution calculates the time delay required for the gas wave to propagate from the push plate position to the pressure sensor position, and performs forward compensation on the timestamp of the gas pressure, eliminating the misalignment between the two heterogeneous data sources caused by the pressure propagation delay; the timestamp alignment after phase compensation makes the driving current value and the gas pressure change trend correspond on the time axis, avoiding false deviations between the first and second rates of change caused by the propagation delay, and improving the calculation accuracy of gas pressure misalignment.

[0099] All of the above-mentioned optional technical solutions can be combined in any way to form optional embodiments of this application, and will not be described in detail here.

[0100] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented electronically, or in a combination of computer software and electronics. Whether these functions are implemented in a software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0101] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0102] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0103] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0104] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0105] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program verification codes.

[0106] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0107] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0108] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0109] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A safety control method for a pusher-type continuous furnace, characterized in that, include: Obtain the operating status parameters of the pusher-type continuous furnace; The operating status parameters include the driving current value of the pusher actuator during movement and the real-time gas pressure inside the pusher continuous furnace. The real-time gas pressure and the drive current value are timestamped; Calculate the first rate of change of the real-time gas pressure within a preset time window and the second rate of change of the drive current value within the preset time window; The pressure misalignment is obtained by calculating the ratio of the difference between the first rate of change and the second rate of change; the pressure misalignment is used to represent the degree of disturbance of the furnace airtightness by the mechanical displacement of the pusher actuator. When the pressure imbalance is greater than a first preset imbalance threshold and less than a second preset imbalance threshold, a first-level safety command is generated; the first-level safety command is used to control the intermediate relay to suspend the power source input of the push plate actuator and trigger an alarm signal; When the gas pressure misalignment is greater than or equal to the second preset misalignment threshold, a second-level safety command is generated; the second-level safety command is used to control the safety module to cut off all power source inputs of the pusher-type continuous furnace and shut off the gas valve.

2. The method according to claim 1, characterized in that, The operating status parameters of the pusher-type continuous furnace are obtained, including: obtaining the current signal of the drive motor of the pusher actuator at a first preset sampling frequency to obtain the drive current value; and obtaining the real-time gas pressure by obtaining the gas pressure signal at a second preset sampling frequency through a pressure sensor installed inside the furnace chamber of the pusher-type continuous furnace. The real-time gas pressure and the drive current value are timestamped and aligned, including: constructing a sliding data cache queue; continuously storing the acquired drive current value and real-time gas pressure into the sliding data cache queue; using the lower of the first preset sampling frequency and the second preset sampling frequency as a benchmark, performing timestamping on the data stored in the sliding data cache queue; removing unaligned data with timestamping differences greater than a preset tolerance, and outputting the aligned real-time gas pressure and drive current value. Calculating the first rate of change of the real-time gas pressure and the second rate of change of the driving current value within the preset time window includes: within the preset time window, calculating the difference between the current value of the real-time gas pressure and the initial gas pressure value at the start of the preset time window, dividing it by the duration of the preset time window to obtain the first rate of change; calculating the difference between the current value of the driving current value and the initial current value at the start of the preset time window, dividing it by the duration of the preset time window to obtain the second rate of change.

3. The method according to claim 2, characterized in that, Calculating the ratio of the difference between the first rate of change and the second rate of change yields the barometric displacement, including: Obtain the reference current change rate and reference pressure change rate of the pusher-type continuous furnace under standard no-load conditions; Divide the first rate of change by the rate of change of the reference pressure to obtain the first relative change ratio; Divide the second rate of change by the reference current rate of change to obtain the second relative change ratio; The absolute difference between the first relative change ratio and the second relative change ratio is calculated as the pressure imbalance.

4. The method according to claim 3, characterized in that, The method further includes: The door gap height value is obtained by acquiring the displacement sensor signal of the furnace door lifting mechanism; When the height of the gap in the door is greater than zero and less than the preset sealing critical height, the furnace door is determined to be in the open state. When it is determined that the furnace door is in the open state, the first relative change ratio is set to zero and the preset current weighting amplification coefficient is obtained; The second relative change ratio is multiplied by the current weighting amplification factor and then used as the pressure misalignment to eliminate the pressure fluctuation interference caused by the opening of the furnace door to release pressure.

5. The method according to claim 4, characterized in that, The operating status parameters also include the real-time furnace temperature inside the pusher-type continuous furnace, and the method further includes: Calculate the rate of change of the real-time furnace temperature within the preset time window; Based on the temperature change rate, the real-time gas pressure is compensated and calculated to obtain the aerodynamic pressure deviation. The difference between the current value of the real-time gas pressure and the initial gas pressure value at the start of the preset time window is replaced by the aerodynamic pressure deviation. Divide the aerodynamic pressure deviation by the time span of the preset time window to calculate the first rate of change after compensation. The specific steps for obtaining the aerodynamic pressure deviation include: The pressure shift caused by thermal expansion is obtained by calculating the product of the temperature change rate and the gas expansion constant. Calculate the total pressure difference between the real-time gas pressure at the current timestamp and the real-time gas pressure at the start of the preset time window; The remaining difference obtained by subtracting the pressure offset from the total pressure difference is used as the aerodynamic pressure deviation.

6. The method according to claim 5, characterized in that, The operating status parameters also include the protective gas makeup flow rate of the pusher-type continuous furnace; before calculating the first rate of change and the second rate of change, the method further includes: Read the real-time flow count value of the protective gas intake proportional valve and perform a definite integral operation on the real-time flow count value within the preset time window to obtain the flow integral value; Obtain the factory-preset no-load furnace volume constant and standard ambient atmospheric pressure constant; The pressure gain is calculated by dividing the integral value of the flow rate by the unloaded furnace volume constant and multiplying it by the standard ambient atmospheric pressure constant. The actual pressure value is obtained by subtracting the pressure gain from the real-time gas pressure at the end of the preset time window; The current value of the real-time gas pressure is replaced by the actual pressure value to participate in the calculation of the first rate of change, so as to eliminate the gas pressure masking interference caused by external active gas replenishment.

7. The method according to claim 6, characterized in that, After obtaining the barometric displacement, the method further includes: Obtain the current travel coordinates of the pusher actuator within the pusher-type continuous furnace and determine the furnace section where the current travel coordinates are located; When the current travel coordinate is in the feeding section of the pusher continuous furnace, the first value is used as the position attenuation coefficient; When the current travel coordinate is deep in the middle of the heat preservation section of the pusher continuous furnace, the second value is used as the position attenuation coefficient, wherein the first value is greater than the second value; Multiply the pressure misalignment by the position attenuation coefficient to obtain the corrected misalignment; The pressure misalignment is replaced by a correction misalignment.

8. The method according to claim 7, characterized in that, The step of obtaining the position attenuation coefficient further includes: When the current travel coordinate is deep in the middle section of the insulation and the real-time furnace temperature is greater than the preset high temperature threshold, the temperature difference between the real-time furnace temperature and the preset reference temperature is obtained. Based on a preset correction coefficient mapping table, the correction factor corresponding to the temperature difference value is obtained by querying. Multiply the correction factor by the position attenuation coefficient to obtain the temperature-compensated corrected position attenuation coefficient; The corrected position attenuation coefficient is used to replace the position attenuation coefficient in calculating the corrected misscheduling.

9. The method according to claim 8, characterized in that, Before generating the first-level security instruction, the method further includes: Read the historical barometric scheduling set within the historical safe operating cycle; Extract the maximum value from the historical barometric displacement set as the baseline value; The first preset misscheduling threshold is obtained by multiplying the basic benchmark value by the first safety factor. The second preset misscheduling threshold is obtained by multiplying the basic benchmark value by a second security factor that is greater than the first security factor.

10. The method according to claim 9, characterized in that, The method further includes: Multiple temperature sensors, distributed along the length of the furnace chamber of the pusher-type continuous furnace, are used to acquire real-time segmented temperature data for each segmented interval. Calculate the temperature difference between two adjacent segmented intervals to generate a temperature gradient distribution sequence; When the maximum temperature difference in the temperature gradient distribution sequence exceeds a preset gradient fluctuation threshold, an early warning signal is output for local abnormal overheating in the furnace.

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