Principle and Fault Analysis of Purifying Hot Air Circulation Oven
1 purification hot air circulation oven working principle The temperature control of the cabinet adopts GCD-23A intelligent computer temperature control and PLC automatic control system, the temperature signal is collected with platinum resistance, and the temperature controller is compared with the set value to get the PID. The control signal, at the same time, the PLC program controller output control signal controls the solid state relay SSR to conduct, and the solid state relay controls the heater to heat, so that the cabinet is in the temperature rising and dehumidifying stage. When the temperature reaches the set value, the temperature controller outputs the PID control signal PLC, and the PLC outputs a control signal to the time relay KT to start the heat preservation timing, and at the same time, close the inlet fan and the exhaust disc valve. The electric heating is continuously opened and closed by PID control, and the box body is in the hot air circulation heat preservation and sterilization stage. When the heat preservation sterilization time reaches the set value, the time relay outputs a signal to the PLC, and the PLC outputs the full closed electric heating, and the water cooling electromagnetic valve is opened to make the suction and conduction, so that the box is in the cooling and cooling stage. When the temperature inside the box drops ≤40 °C, the temperature controller outputs a control signal to the PLC, and the PLC output turns off the hot air circulation fan, and the dry sterilization cycle program ends. TEED-2001K over-temperature alarm temperature controller output signal controls PLC's whole program operation, platinum resistance PT100 test signal to alarm temperature controller compares with over-temperature alarm setting temperature value, when the actual temperature value is lower than the set value, the output The control signal is sent to the PLC, and the PLC program runs normally. When the actual temperature value exceeds the set value, the control signal is output to the PLC, and the PLC closes the running program. Therefore, the setting value of the over temperature alarm is generally higher than the set value of the working temperature.
2 Failure analysis and solution of purifying hot air circulation oven 2.1 Description of fault phenomenon Closed loop oven air switch, according to the operating instructions of the oven, set heating temperature 250 °C, over temperature alarm temperature 260 °C, heat preservation time 1h, start its automatic operation The program, the oven's circulating fan, inlet fan, disc valve, heating and other indicators light up in sequence, indicating that the program is operating normally. After heating for 2.5h, the temperature still does not reach the set value. If the heating time is too long, the heated glass container will be brittle and the bad bottle rate will increase. At the same time, it causes energy waste and increases power consumption. As well as the long working cycle of the oven, the process can not be completed on time in the two-shift system of normal production, delaying the production process of the task and increasing the production cost. It takes 2.5 hours to heat the room temperature from room temperature to 250 °C in normal full box, and it takes about 6 hours in one working cycle.
2.2 Failure Analysis First check the oven differential pressure gauge to determine whether the wind speed in the oven is normal. Understand whether the heated items in the circulating oven are too dense, whether the high-temperature and high-efficiency filter is clogged, and whether the air volume adjusting plate is changed. After eliminating these reasons, it is judged whether the circulating fan is faulty, resulting in poor circulation of hot air circulation, hot and humid air. Can not be discharged normally. Secondly, from the fault phenomenon and the circuit principle of the oven, the oven can be heated, indicating that the output signal of the GCD-23A intelligent computer temperature controller is normal, and the PLC input and output signals are also normal.
2.3 Fault detection and elimination After the above fault analysis, it can be concluded that the control signal and the adjustable components are normal, and then we check from the following aspects. First check the PID adjustment parameters of the GCD-23A intelligent computer temperature controller to see if the human error operation causes the setting parameters to change, which causes the system to malfunction. The PID parameters directly affect the adjustment accuracy of the system and are the core content of the control system design. Through the appropriate PID parameters, the PID control can calculate the system control amount by proportional, integral and differential according to the error characteristics of the system controlled process, and obtain the corresponding output response characteristics, and the control system can achieve satisfactory control effect. Restore the normal setting value of the PID parameter. Secondly, it is checked whether the circulating fan is running normally and the steering is correct. If the fan is reversed or the fan load is too high and the speed is too slow, it will affect the hot air circulation.
When the fan is reversed, any two phases of the fan's power supply can be reversed; when the fan speed is too slow, it should be checked from two aspects: (1) Whether the power supply voltage is normal, whether there is phase loss or winding open circuit. (2) Whether there are any problems such as broom, vibration, bearing overheating, damage, loosening of the fan blades, etc. Can be excluded for specific situations. Check again if the solid state relay and heater are partially open. Solid state relay (SOLIDSTATERELAYS), abbreviated as 'SSR', is a new type of non-contact switching device composed entirely of solid-state electronic components, which utilizes the switching characteristics of electronic components such as switching transistors, semiconductor devices such as triacs. It can achieve the purpose of turning on and off the circuit without contact and non-sparking, so it is also called “contactless switchâ€. SSR successfully realizes the control of strong signal (output load voltage) by weak signal (Vsr) The partial disconnection of the SSR after the virtual connection or conduction causes the 380V power supply to be out of phase, and the heater cannot be fully heated. The treatment method is to repair or replace the solid state relay. The partial disconnection of the heater will also prevent the heating from working all the way, causing the heating process. Too slow. Repair or replace the heater. Completely handle the problem. Close the circulating oven air switch and run the program according to the operating instructions of the oven. After 2.5 hours of heating, the oven reaches the set temperature and the time relay starts timing. The oven enters the stage of insulation and sterilization of intermittent heating. After 1 hour of heat preservation, the oven starts to cool down and cools, and after 2.3 hours, the whole is dried and sterilized. The cycle program runs to the end, fully meeting the technical parameters and process parameters required by the oven.
Main: open door oven, tunnel oven, hot air circulation oven, three-dimensional mixer
2 Failure analysis and solution of purifying hot air circulation oven 2.1 Description of fault phenomenon Closed loop oven air switch, according to the operating instructions of the oven, set heating temperature 250 °C, over temperature alarm temperature 260 °C, heat preservation time 1h, start its automatic operation The program, the oven's circulating fan, inlet fan, disc valve, heating and other indicators light up in sequence, indicating that the program is operating normally. After heating for 2.5h, the temperature still does not reach the set value. If the heating time is too long, the heated glass container will be brittle and the bad bottle rate will increase. At the same time, it causes energy waste and increases power consumption. As well as the long working cycle of the oven, the process can not be completed on time in the two-shift system of normal production, delaying the production process of the task and increasing the production cost. It takes 2.5 hours to heat the room temperature from room temperature to 250 °C in normal full box, and it takes about 6 hours in one working cycle.
2.2 Failure Analysis First check the oven differential pressure gauge to determine whether the wind speed in the oven is normal. Understand whether the heated items in the circulating oven are too dense, whether the high-temperature and high-efficiency filter is clogged, and whether the air volume adjusting plate is changed. After eliminating these reasons, it is judged whether the circulating fan is faulty, resulting in poor circulation of hot air circulation, hot and humid air. Can not be discharged normally. Secondly, from the fault phenomenon and the circuit principle of the oven, the oven can be heated, indicating that the output signal of the GCD-23A intelligent computer temperature controller is normal, and the PLC input and output signals are also normal.
2.3 Fault detection and elimination After the above fault analysis, it can be concluded that the control signal and the adjustable components are normal, and then we check from the following aspects. First check the PID adjustment parameters of the GCD-23A intelligent computer temperature controller to see if the human error operation causes the setting parameters to change, which causes the system to malfunction. The PID parameters directly affect the adjustment accuracy of the system and are the core content of the control system design. Through the appropriate PID parameters, the PID control can calculate the system control amount by proportional, integral and differential according to the error characteristics of the system controlled process, and obtain the corresponding output response characteristics, and the control system can achieve satisfactory control effect. Restore the normal setting value of the PID parameter. Secondly, it is checked whether the circulating fan is running normally and the steering is correct. If the fan is reversed or the fan load is too high and the speed is too slow, it will affect the hot air circulation.
When the fan is reversed, any two phases of the fan's power supply can be reversed; when the fan speed is too slow, it should be checked from two aspects: (1) Whether the power supply voltage is normal, whether there is phase loss or winding open circuit. (2) Whether there are any problems such as broom, vibration, bearing overheating, damage, loosening of the fan blades, etc. Can be excluded for specific situations. Check again if the solid state relay and heater are partially open. Solid state relay (SOLIDSTATERELAYS), abbreviated as 'SSR', is a new type of non-contact switching device composed entirely of solid-state electronic components, which utilizes the switching characteristics of electronic components such as switching transistors, semiconductor devices such as triacs. It can achieve the purpose of turning on and off the circuit without contact and non-sparking, so it is also called “contactless switchâ€. SSR successfully realizes the control of strong signal (output load voltage) by weak signal (Vsr) The partial disconnection of the SSR after the virtual connection or conduction causes the 380V power supply to be out of phase, and the heater cannot be fully heated. The treatment method is to repair or replace the solid state relay. The partial disconnection of the heater will also prevent the heating from working all the way, causing the heating process. Too slow. Repair or replace the heater. Completely handle the problem. Close the circulating oven air switch and run the program according to the operating instructions of the oven. After 2.5 hours of heating, the oven reaches the set temperature and the time relay starts timing. The oven enters the stage of insulation and sterilization of intermittent heating. After 1 hour of heat preservation, the oven starts to cool down and cools, and after 2.3 hours, the whole is dried and sterilized. The cycle program runs to the end, fully meeting the technical parameters and process parameters required by the oven.
Main: open door oven, tunnel oven, hot air circulation oven, three-dimensional mixer
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