Cooling tower cleaning

A cooling tower is a device for lowering the temperature of water in an air conditioning network by evaporative cooling in which the water is showered into a space through which atmospheric air circulates.

The efficiency of this heat transfer system can be reduced in a number of ways:

• The dissolved chemicals in water basins can over time form a hard layer of scale in the system;
• Sludge can accumulate in the bottom of cooling tower basins promoting micro-organism growth;
• The continuous passage of water over the metallic surfaces of the tower system can cause corrosion;
• Micro-organisms and other organic matter can grow in the tower basins fouling the system as well as a potential health risk to people.

With these points in mind it is imperative that regular cleaning and maintenance takes place in order to increase the longevity of the cooling tower system. The Building Act 1991 states cooling tower systems in use should be inspected at least monthly, as part of its regular maintenance program, and be cleaned, when necessary.

Cleaning should include the physical cleaning of the cooling tower and the disinfecting and draining of the entire cooling water system. Unless approved otherwise the cleaning interval should not exceed 6 months.

All internal wetted surfaces of cooling towers, particularly the sumps, anti-splash mats and fill should be cleaned in accordance with the supplier?s instructions. Due care shall be taken to ensure the lower structure and components are not damaged during the cleaning operation.

Cooling towers should be operated and maintained using the following procedures:

• Inspected at least monthly as part of the regular maintenance routine;
• Cleaned regularly as necessary but at intervals not exceeding six months;
• Flushed and cleaned before start up if only used seasonally;
• All internal wetted surfaces, particularly the sump and fill, cleaned by high pressure water, steam or other effective method;
• The operating conditions of the system operating pumps and cooling tower fans should be reviewed. Reducing the system operating water temperatures to the lowest practicable value improves control of micro-organisms (Legionella spp.) and improves operating efficiency.