Maintenance Guide for Cooling Tower Aluminum Alloy Fan

The aluminum alloy fan blades of the cooling tower are constantly exposed to a humid, hot, salt spray and high-speed rotating environment, which makes them prone to scaling, corrosion, loosening and deformation. Dividing the maintenance work into five stages: "observation, cleaning, calibration, lubrication and storage" can systematically maintain its efficient, low-noise and safe operation.

Take a look - Inspect the appearance and detect any abnormalities. Each shift should visually inspect the surface of the fan blades for any cracks, notches or severe scratches. When operating at high speed, use a point thermometer or infrared imaging to detect the temperature difference at the blade tip. If the local hot spot exceeds the ambient temperature by 15 ℃, it indicates internal delamination or microscopic cracks, and the machine should be stopped immediately for inspection. At the same time, monitor for noise. When the wideband howling suddenly increases by more than 3 dB, it is mostly caused by the drift of the fan blade Angle or the loosening of the bolts.

Second cleaning - descaling and anti-corrosion. Although the oxide film on the surface of aluminum alloy can self-blunt, the Cl⁻ and SO₄²⁻ contained in the water vapor of the cooling tower can penetrate the film layer. Immediately after the machine stops, flush away the floating dust with low-pressure water below 60 ℃ (< 0.4MPa). For stubborn salt scale, spray in a circulating manner with 5% sulfamic acid and 0.3% corrosion inhibitor for 5 minutes, then rinse with clean water. Do not use wire brushes to avoid scratching the anodic oxide layer. If the concentration of chloride ions in the environment exceeds 50 mg/L in winter, it is recommended to spray an additional 8 µm acrylic transparent anti-corrosion paint on the surface of the fan blades, which can extend the service life of the bare material by two times.

Three Verifications - Angle and Balance. A blade Angle error greater than ±1° can cause an 8% decrease in air volume and a 5% increase in current. Three points were measured at 150mm from the leaf tip using a digital inclinometer to ensure that the Angle difference among the four leaves was no more than 0.5°. If the vibration velocity of the unit is greater than 4.5mm /s (ISO 10816-3), the fairing needs to be removed and dynamic balancing should be performed on each blade. On-site, a 1g gradient transition test weight can be attached and remeasured until the residual unbalance is less than 5g ·cm. The bolts are tightened in three levels with alternating torque increments of 10 N·m and coated with DOW 7096 anti-seizing grease to prevent electrochemical seizing.

Four runes - Shaft ends and interfaces. Although the fan blade body has no bearings, the mating surface between the hub and the main shaft conical sleeve is prone to fatigue marks due to fretting wear. Apply molybdenum disulfide spray lightly to the bonding surface every 2000 hours to reduce the micro-kinetic friction coefficient by 30%. Check the fastening nut of the cone sleeve. Its looseness is the main cause of the blade sinking and sweeping the chamber. Simultaneously check the drainage holes of the motor end cover to ensure they are unobstructed and prevent condensate water from flowing back into the hub cavity.

Five Storages - Shutdown and Storage Techniques. If the machine is shut down for more than two weeks, first run it at low speed for 10 minutes to dry the water film on the leaf surface, and then close the air inlet and outlet valves to reduce the backflow of moisture. Remove the fairing and insert an environmentally friendly desiccant bag (2 kg per cubic meter) between the wheel hub and the air duct. The moisture absorption rate is ≥ 200%, which can prevent white spots from forming on the aluminum surface. If the storage period spans winter, the bearings should be manually turned 180° every month to prevent indentation due to static load, and at the same time, check whether the blades have low-temperature brittleness cracks.

By quantifying daily, monthly and annual maintenance through the "five-step method", the service life of aluminum alloy fan blades can be extended from 5 years to 8 to 10 years, the failure rate can be reduced by 60%, and the unit can be kept operating near the designed energy efficiency point, providing a guarantee for 5% water conservation and 7% electricity conservation for the entire tower.