As the core equipment for product reliability testing, the stable operation of the walk-in high and low temperature room directly affects the validity of the test data. When an abnormality occurs, it is necessary to quickly locate the source of the fault through systematic troubleshooting. The following is professional guidance on typical fault phenomena, causes, and solutions:
1、 Temperature control system failure
Phenomenon characteristics
The deviation between the set temperature and the actual displayed value is greater than 5 ℃, or the temperature cannot be raised/lowered
Frequent start stop of compressor accompanied by abnormal noise
Core investigation path
Refrigerant circulation circuit
Observe the degree of frosting on the dry filter. Severe frosting indicates excessive moisture and requires replacement of the filter element
Detect the values of high and low pressure gauges (R404A normal value is high pressure 1.8-2.2MPa, low pressure 0.4-0.6MPa), and if the pressure difference is too small, it indicates refrigerant leakage
Emergency response: For minor leaks, soap water can be used for leak detection before welding repair. For severe leaks, professional filling is required
Heating module malfunction
Measure the resistance value of the electric heating tube. If it deviates from the rated value by ± 10%, it needs to be replaced
Clean the oxide layer on the surface of the heating tube. Poor contact can cause local overheating and burning
PID parameter disorder
Enter the controller parameter interface and check the correspondence between SV (set value) and PV (measured value)
New settings for P (proportional), I (integral), and D (derivative) parameters. It is recommended to debug by increasing the default values by 1/4
2、 Inaccurate humidity control
Typical performance
Relative humidity fluctuation>± 5% RH, or always displaying 100% saturation state
The humidification sink produces turbid sediment
Accurate disposal plan
Water quality management
Use deionized water (conductivity<5 μ S/cm) and replace the water storage tank every week
Install a 0.22 μ m precision filter to block microbial growth channels
Dehumidification system repair
Check the frost thickness on the surface of the evaporator. If it exceeds 3mm, adjust the defrosting cycle forcibly
Verify that reversing the direction of the condenser fan will result in a decrease of over 60% in heat transfer efficiency
Humidity sensor calibration
Using a standard salt spray generator for cross validation, if the error is greater than 2% RH, it is necessary to replace sensors from brands such as Honeywell
3、 Abnormal electrical control system
Warning signs of danger
Touch screen crashes or buttons do not respond
Frequent tripping of leakage protection switch
Graded maintenance strategy
Line insulation testing
Use a 500V megohmmeter to measure the insulation resistance of the main circuit to ground, which should be>2M Ω
Focus on inspecting aging cable interfaces, especially those with bending radius less than 10 times the wire diameter
Relay contact maintenance
Disassemble the contactor coil, polish and burn the contact points with fine sandpaper, and replace them if the number of actions exceeds 100000
Re press the terminal block and control the torque at 0.6-0.8N · m to prevent virtual connection
PLC program backup
Regularly export Mitsubishi/Siemens PLC programs and establish version management files
When there is a sudden system crash, the program can be recharged through the serial port
4、 Physical structural hazards
Potential risk points
The hardening and cracking of the sealing strip of the box caused the escape of temperature and humidity
Observing the appearance of silver cracks on the window glass
Structural strengthening scheme
Sealing system regeneration
Replace the EPDM foam sealing strip and control the compression within the optimal range of 30% -50%
Silicone sealant repair joints, remove surface oil stains before curing
Reinforcement of vibrating components
Check the aging degree of the vibration damping pad of the fan every month, and replace the cracked rubber parts immediately
Tighten all M8 and above bolts with torque in accordance with GB/T 5782 standard
By establishing a four level diagnostic mechanism of "phenomenon observation → data analysis → component disassembly → system calibration", combined with preventive maintenance plans, the equipment failure rate can be reduced to below the industry average level. It is recommended to configure a dedicated toolkit (including vacuum pump, halogen leak detector, digital multimeter) and develop a standardized operation process card to ensure that each maintenance is based on evidence.