Closed Circuit Water Treatment
Just like cooling tower systems, which is an open circuit, closed circuit water loop also requires attention and maintenance. Closed circuit water treatment is often overlooked by user and decided not to carry out any treatment for the system based on the assumption that it is a closed system. Although closed circuit water system has less exposure to external influence like dust, sunlight, open space, making it less prone to scaling, sludge deposit and algae formation in the system, there is still one main concern to be taken care of, which is dissolved oxygen. Presence of present oxygen in the system will lead to localised pitting/ corrosion.
Localised pitting is often identified when there are corroded surface or cavities on the metal surface. The iron debris lost from localised corrosion will travel along the closed circuit, depositing along the way, even into equipment like boiler or chiller, affecting their efficiency or operation. Therefore, closed circuit water system often appear loaded with black debris and rust if left untreated for long time. At elevated temperature, in the case of boiler closed circuit water, will expedite the corrosion rate and lead to severe corrosion in short period of time.
The chemical used in closed circuit water treatment is mainly used to counter the present of dissolved oxygen by introducing oxidizing element into the system. The effectiveness of the chemical is determined by how complete it oxidise the dissolved oxygen into more stable and neutral compound.
The treatment programme designed for hot water circuit or chilled water circuit is the same, the only difference lies in the use of treatment chemicals as the active ingredients, which is the oxygen scavenger due to the temperature difference. The active ingredients often used in chilled water treatment is nitrite based, while in hot water treatment is sulphite based as sulphite is more thermal resistance in nature.