Cooling water systems acid cleaning

NOTE The view that deposition is an indicator of more widespread problems is also common to cooling water systems. As a result of the complex nature of deposits, their removal by acid or mechanical cleaning of boiler or cooling systems is not always as simple a process as may be portrayed. 

If the scale is mostly ferric oxide (FeOOH or red "rust"), a safe solvent using HEDTA and the reducing agent erythorbic acid can be used to clean cooling water systems at temperatures at or below 150°F (65°C). 

A dual cooling system is a modification of the above which maintains the cooling efficiency. The acid is first cooled by demineralized water in a closed circuit. It is in turn cooled by process water or water from a cooling tower. The heat transfer surfaces remain clean where DM water is being circulated. 

After the desired contact time, stop adding acid. Provide as heavy a bleed of water as the production process permits to remove dead slime from the cooling system. Reuse surface skimmers. Allow fresh makeup water to raise the recirculating water pH to 7.6-7.8 or so. Only move to the next stage of cleaning when the water looks clean. This may take many hours. 

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