Winter Cooling Tower Maintenance Guide
Winter cooling tower maintenance requires first determining the operational status of the equipment: whether it will continue to operate or undergo seasonal shutdown. The maintenance logic differs significantly between the two states—the focus during operation is on antifreeze protection to ensure functioning, while the focus during shutdown is on drainage and corrosion prevention.
I. Continued Operation in Winter: Antifreeze is the Priority
If the cooling tower must continue to run during the winter (such as for process cooling or data center scenarios), antifreeze measures can be established from the following four levels.
1. Circulating Water Medium Level
Using antifreeze is a relatively reliable anti-freezing method. Ethylene glycol or propylene glycol solutions can be added to the internal circulation medium of the closed-circuit cooling tower's coils, which lowers the freezing temperature. Please note: the higher the concentration of the antifreeze, the better the anti-freezing effect, but the thermal conductivity will decrease, so calculations must be made in advance during model selection. If there is a system leak, makeup water will dilute the antifreeze concentration, requiring regular freezing point testing.
2. Operating Parameters Level
The outlet water temperature should not be too low. During winter operation, it is recommended to maintain an outlet water temperature of no less than 6°C; the higher the water temperature, the lower the risk of freezing. At the same time, avoid partial bypass modes—when adjusting capacity through a bypass, the volume of water flowing through the coils decreases, and uneven water distribution will cause localized freezing. Fan control must prevent over-cooling. When using variable frequency drives, the minimum speed is recommended to be set at about 50% of the rated speed to prevent internal wind speeds from becoming too low and causing freezing due to the fan running at low speeds for a long time. When multiple cooling towers are connected in parallel, the air volume of each tower should be balanced and controlled; excessive air volume in a single tower may cause local super-cooling in that tower.
3. Equipment Accessories Level
Before winter operation, it should be confirmed that the following accessories are working properly: Basin heaters are used to prevent the collection basin from freezing, but note that they cannot protect external water pipes and pump pipelines; Motor space heaters should be turned on when the fan is shut down for more than 24 hours to expel condensed water vapor from the windings; Electronic water level controllers are more reliable than traditional mechanical float valves, as mechanical floats are prone to freezing and jamming at low temperatures; Vibration cut-off switches can automatically shut down the fan when severe vibrations occur due to icing, preventing damage to the drive system. Makeup water pipes, overflow pipes, and drain pipes need heat tracing and insulation, and all connection points at and below the water level also need to be covered.
4. Daily Inspection Level
Inspection frequencies should be increased in winter, focusing on whether ice formation is appearing on air inlets, fan blades, and coil surfaces. If ice is found, do not manually knock or shovel it off; let the ice melt naturally or adopt gentle methods such as hot water ice melting. Manual de-icing may damage fan blades and coils, and falling ice blocks pose personnel safety risks.
II. Seasonal Shutdown: Draining, Cleaning, and Protection
If the cooling tower is completely shut down for the winter, the maintenance focus shifts to thorough draining and corrosion prevention.
1. Draining the System
Simply opening the drain valve is often not enough. Residual water may remain in pipe bends and low-lying areas, and when it freezes, the expansion in volume can crack pipelines and coils. It is recommended to use compressed air to purge coils and pipelines to ensure internal dryness. For closed-circuit towers, nitrogen charging protection can be considered if the coils are shut down for more than 1 month.
