How to deal with the failure of the hot air circulation oven?

The hot air circulation oven uses electricity as the heat source, and uses a low-noise and high-temperature-resistant axial flow fan to heat the air in a convective manner to the heat exchanger. The hot air layer flows through the baking tray to transfer heat with the material. The thermal circulation oven adopts the 100-level purification hot air circulation laminar flow purification technology, equipped with computer automatic control system, temperature control technology, reliable sterilization and drying, low noise of the whole machine, stable operation, and realizes automatic constant temperature control and fully enclosed and full cycle operation , in full compliance with the requirements of pharmaceutical GMP production specifications.

Fault Analysis and Solution of Hot Air Circulation Oven

1. Description of fault phenomenon

Closed cycle oven air switch, according to the operation manual of the oven, set the heating temperature to 250°C, the over-temperature alarm temperature to 260°C, and after 1 hour of holding time, start its automatic operation program, the oven's circulation fan, intake fan, disc valve, heating, etc. The lights will come on in sequence to indicate that the program is running properly. After 2.5 hours of heating operation, the temperature still cannot reach the set value. If the heating time is too long, the heated glass container will be fragile and the rate of broken bottles will increase. Simultaneously, cause energy waste, power consumption increases. And the working cycle of the oven is lengthened, so that the process link cannot be completed on time under the two-shift system of normal production positions, the process plan of the production task is almost missed, and the production cost is increased. It takes 2.5 hours to heat the temperature from room temperature to 250°C when the container is full, and a working cycle takes about 6 hours.

2. Failure analysis

First check the differential pressure gauge of the oven to determine whether the wind speed in the hot air circulation oven is normal. Find out whether the heated items in the hot air circulation oven are too densely placed, whether the high-temperature efficiency filter is clogged, and whether the air volume adjustment plate has been changed. After eliminating these reasons, judge whether there is a fault in the circulating fan, resulting in poor circulation of hot air circulation, damp heat Air cannot be vented properly. Secondly, from the analysis of the fault phenomenon and the circuit principle of the oven, the hot air circulation oven can be heated, indicating that the output signal of the GCD-23A intelligent computer temperature controller is normal, and the input and output signals of the PLC are also normal.

3. Fault detection and troubleshooting

After the above fault analysis, it can be concluded that the control signal and 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 there is a human error operation, resulting in the change of the setting parameters, which makes the system abnormal. PID parameters directly affect the adjustment accuracy of the system, and are the core content of the control system design. Through appropriate PID parameters, PID control can calculate the system control quantity by using proportion, integral and differential according to the error characteristics of the controlled process of the system, obtain the corresponding output response characteristics, and control the system to achieve a satisfactory control effect. Restore the normal setting value of PID parameter. Secondly, check whether the circulating fan is running normally and whether the steering is correct. If the fan is reversed or the fan load is too large and the speed is too slow, it will affect the hot air circulation. When the fan is reversed, any two phases of the power supply of the fan can be reversed; when the fan speed is too slow, it should be checked from two aspects:

(1) Electrically, whether the power supply voltage is normal, whether there is a phase loss or winding open circuit.

(2) Whether there are mechanical failures such as bore sweeping, vibration, bearing overheating, damage, loose fan blades and rubbing the box shell. Exclusions may be made on a case-by-case basis. Check again for partial breaks in the solid state relay and heater. Solid State Relay (SOLIDSTATERELAYS), abbreviated as "SSR", is a new type of non-contact switching device composed entirely of solid-state electronic components. It can achieve the purpose of connecting and disconnecting the circuit without contact and spark, so it is also called "contactless switch". The SSR has successfully realized the control of the weak signal (Vsr) to the strong current (the load voltage at the output terminal). SSR virtual connection or partial open circuit after conduction causes 380V power supply to lose phase, and the heater cannot be fully heated. The solution is to repair or replace the solid state relay. And the partial circuit breaker of the heater will also make the heating unable to work at all, causing the heating process to be too slow. Repair or replace heater. Completely deal with the failure problem. The air switch of the closed cycle oven runs its program according to the operation manual of the oven. After 2.5 hours of heating, the oven reaches the set temperature, the time relay starts timing, and the oven enters the heat preservation and sterilization stage of intermittent heating. After 1 hour of heat preservation, the hot air circulation oven starts to cool down, and after 2.3 hours, the entire drying and sterilization cycle program ends, which fully meets the technical and process parameter requirements provided by the oven.