Oven maintenance

Purification principle and fault analysis of the hot air circulating oven
1  cleaning principle of the hot air circulating oven

box for the temperature control of GCD-123 a smart computer temperature control and PLC control system, signal acquisition using Platinum resistance temperature, enlarged compared with the setting of temperature controllers PID control signals, and PLC programmable output control signals to control a solid state relay SSR conduction, solid state relay control heater, heating the box in dehumidification stage. When the temperature reaches the set value, the PID temperature controller output PLC,PLC output control signal control signal for time relays KT, which began holding time and close the air inlet and exhaust butterfly valve. By PID control of electric heating constant opening and closing, box in the hot air circulating heat sterilization phase. When the heat sterilization time reaches the set value, the relay output signal to the full closed to PLC,PLC electric heating, open water cooling electromagnetic valve to make it suck-in-conduction and box in the cooling phase. When the temperature inside the box falling ≤ 40 ℃, the temperature controller output control the output signal to the PLC,PLC off hot-air circulation fans, program end of drying cycle. TEED 12,001 k overtemperature alarm temperature sensor output signal control PLC runs throughout the program, platinum resistance PT100 signals to the alarm temperature controller compare with the over temperature alarm set point, when the actual temperature value is lower than the set value, the output control signal to the PLC,PLC program to work correctly. When the actual temperature exceeds the set value, the output control signal off to PLC,PLC to run the program. Over-temperature alarm set value is usually higher than the set temperature value.

2  fault analysis and solving method of purifying hot air circulating oven

2.1  symptom description

closed circulation oven air switch, follow the operating instructions set the oven temperature 250 c, overtemperature alarm temperature 260 ° c, holding time after 1h, start the autorun program, oven circulation fans, into the wind machine, butterfly valves, heating indicator light lit in sequence, indicates that a program is operating normally. Heat after running 2.5h, the temperature is still not up to the set value, if heated for too long, it will cause a fragile glass containers to be heated, bad bottles increased. Meanwhile, energy waste, increase power consumption. And oven work cycle longer, resulting in normal production posts under the two-class system can finish the process, almost missed production process planning and increase the cost of production. Normal full box temperature from room temperature has been heated to 250 ° c 2.5h,1 work you need cycle takes about 6h.

failure analysis of 2.2 

check the oven first differential pressure gauges, determine whether the wind speed in the oven properly. Learn cycle the oven is heated place is too crowded, high temperature and high efficiency filter is blocked, air flow adjustment plate was changed, after eliminating these causes, and then determines whether the circulation fan failure, causing hot air circulation air circulation is not good, hot air cannot be normal. Second Circuit theory analysis of the symptom and the oven, the oven heats, that GCD-123 a intelligent computer-controlled temperature output signal correctly, PLC input/output signal is normal.

2.3  fault detection and exclusion

after the above fault analysis, it can be concluded that the control signal and adjustable parts are normal, then we check from the following aspects. First of all check the GCD-123 a PID parameters of intelligent computer-controlled temperature instrument and see if people misuse, resulting in changes of setting parameters, thus making the system appear abnormal. PID parameters directly affect system accuracy, control system design is the core content. Through the appropriate PID parameters PID control process can be controlled according to the system's characteristics using the proportional, integral, differential system control quantity is calculated, the corresponding output response characteristics, control systems to achieve satisfactory results. Recover PID parameter setting. Second detection of circulating fan operation is normal, the direction is correct. If the reverse fan or fan load is too big and slow speed, will affect the air circulation is not clear.

     when the fan turns, can power any two phases of the fan switch; when the fan speed is too slow, check should be viewed from two aspects: (1) electrical supply voltage is normal, there is no default or a winding circuit breaker. (2) has no mechanical sweep, vibration, bearing bore overheating, damaged, loose fan blades to clean the tank shell, and so on. Can be excluded for specific situations. Testing solid state relay and again whether the heater has a local circuit breaker. Solid state relays (SOLIDSTATERELAYS), abbreviated as 'SSR "is a made up entirely of solid state electronic components of new switch device, which uses electronic components (such as switching transistor, TRIAC semiconductor devices) switching can be achieved non-contact non-sparking purposes of connect and disconnect the circuit, also known as" contactless switch. " SSR succeeded in achieving a weak signal (Vsr) high voltage (output load voltage) control. SSR virtual connection or after conducting local 380V power supply missing phase circuit breaker, heater not all heating, treatment methods is the repair or replacement of the solid state relay. Local circuit breaker heater, also will bring the heat can't all work to cause heating process is too slow. Repair or replace the heater. Failure handling well. Closed circulation oven air switch, in accordance with the operating instructions of the oven run its programs, 2.5h warming, oven reaches the set temperature, time relays start running, insulation of the oven into the intermittent heating and sterilization phases. Insulation 1h oven started cooling, 2.3h throughout the drying cycle after the program has finished running, fully satisfy the oven's technical parameters and process parameters.

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