Key Inspection Points and Fault Handling Guidelines for Air-Cooled Fans

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Key Points for Inspecting Air-Cooled Fans and Guidelines for Fault Handling

I. Key Points for Systematic Inspection

Inspection of the Transmission System
(1) Belt Inspection
Visual inspection: Check for cracks, peeling, cracking, hardening, or other signs of aging on the belt surface; also check for wear particles in the pulley grooves.
Tension measurement: Use a dedicated tension gauge or the thumb-pressure method (an ideal displacement of 10–15 mm when pressing is sufficient).
Further inspection: Use a ruler to ensure that the deviation between the two pulley surfaces does not exceed 1 mm per 100 mm of wheel spacing.

Inspection of the Fan Itself
(1) Monitoring of Operating Conditions
Vibration detection: Use a vibration meter to measure the vibration levels at the bearing seats; these should typically be ≤4.5 mm/s (RMS value).
Noise monitoring: Use a sound level meter; abnormal noise levels (>85 dB) require further investigation.
Blade inspection: When the fan is shut down, check for cracks or deformation in the blades; the thickness of dust accumulation should not exceed 1/3 of the blade’s thickness.
(2) Lubrication System
Oil level check: The oil level indicated by the oil sight glass should be between 1/2 and 2/3 of the capacity; for grease-lubricated bearings, the filling amount should be between 1/3 and 1/2 of the bearing cavity.
Oil quality analysis: Regular samples should be taken for testing; if the water content exceeds 0.1% or the acid value exceeds 1.5 mgKOH/g, the oil needs to be replaced.
Lubrication schedule: For continuously operating equipment, lubricant should be replenished every 2000 hours; in high-temperature environments, this interval should be reduced to 1000 hours.

Inspection of the Motor System
(1) Electrical Parameters
Three-phase current imbalance should be <10%, and the temperature rise should not exceed the limits specified for the insulation grade (Grade B: ≤80 K).
Insulation resistance: Measured using a 500 V megohmmeter, it should be >1 MΩ (for new equipment, it should be >5 MΩ).
(2) Mechanical Condition
Bearing temperature: Rolling bearings should not exceed 95°C, while sliding bearings should not exceed 80°C.

Safety Protection Inspection
The mesh size of protective covers should be ≤10 mm, with a distance of ≥50 mm from any hazardous areas.
The emergency stop device should be tested monthly, with a response time of <2 seconds.
Grounding resistance should be ≤4 Ω, while the grounding resistance of lightning protection devices should be ≤10 Ω.

II. Diagnosis and Handling of Typical Faults

Mechanical Faults
(1) Bearing Faults
Fault characteristics: Spectrum analysis shows prominent first harmonics and other harmonics, along with an increase in temperature.
Handling procedures:
① After shutting down the fan, manually rotate it to check for any sticking.
② When replacing bearings, pay attention to the orientation of the bearing cages; fill 30% of the space with lubricant beforehand.
③ Perform dynamic balancing to ensure that the residual imbalance is ≤1.6 mm/s.
(2) Blade Faults
Dynamic balancing: Use an on-site dynamic balancer to correct imbalances; the remaining imbalance should be ≤G6.3 level.
Mechanical damage: If there are cracks or breaks in the blades, they must be replaced immediately. Electrical faults: (1) Winding faults – Diagnosis method: DC resistance test; three-phase deviation should be <2%, and the polarization index should be ≥2.0. Repair steps: Vacuum impregnation treatment; drying temperature for F-class insulation is 155±5°C. (2) Power supply faults – Protection settings: Thermal relay setting value = 1.05–1.2 times the rated current. Voltage monitoring: Install smart meters to record voltage fluctuations; transient fluctuations should be ≤±10%. System faults: (1) Insufficient air flow – Troubleshooting steps: ① Measure the sealing performance of the static pressure box (air leakage rate <5%). ② Adjust the blade angles within the range of ±5°. (2) Abnormal vibration – Diagnosis process: ① Bearing failure or damage. ② Blade damage or loss of dynamic balance. III. Recommendations for preventive maintenance: Maintain an equipment health record; keep daily records of operating parameters; manage lubrication records on a quarterly basis; develop annual maintenance plans; implement smart monitoring solutions by installing online vibration monitoring systems and infrared thermal imaging devices for regular inspections. For spare parts, maintain a stock of 3 months’ worth of key components such as bearings and belt drives; the replacement cycle for wear-prone parts is 1–2 years for belts and 3 years for coupling elastomers. It is recommended to use an equipment management system to facilitate digital operation and maintenance. For special operating conditions, the maintenance parameters must be adjusted according to the manufacturer’s technical manual.