The success of aluminium casting depends on the implementation of accurate temperature control through the smelting and casting process. The dissipation of heat must be uniform at all points of the final product.
Temperature control is achieved through the application of water, which influences the aluminium material structure, the microstructure and the surface of the metal. The quality of the cooling water directly affects the quality of the cast aluminium.
The water is required to have consistent conductivity between 1 800 and 2 000 µS/cm (TDS 1 260 – 1 400 mg/l) and chlorides approximating 600 mg/l. Metal cracking results when the conductivity is out of range.
When Watercare Innovations was given the opportunity to manage the cooling water quality at an aluminium smelter, the client was experiencing product cracking and rejection directly resulting from the sub-optimal cooling stage of manufacture. White deposits were forming on the finished metal surface, negatively impacting the market value of the product.
We worked with the client’s technical team to improve the quality of the water used to cool the aluminium moulds and reduce the incidents of product rejection.
Visible difference in cooling water quality
Real-time remote monitoring to manage cooling water treatment
The cooling water system is 1,3 ML. At the time that we took over the control of the system, the TDS was in excess of 8 000 mg/l and chlorides were over 1 000 mg/l. The water was treated with chlorine gas for microbial control.
Before implementing the water treatment programme, our team physically cleaned the hot and cold wells, as well as the cooling tower sump and other retention dams.
A fully automated conductivity controller was installed and linked to WaterBizz, Watercare Innovations’ in-house IT platform. This enabled remote, real-time monitoring of the water’s pH and conductivity by both our site representative and the customer.
Both Watercare Innovations and the customer communicate daily on the observed trends. Immediate corrective action is implemented when the parameters are out of specification.
Chemical treatment programme to control cooling water quality
The chemical water treatment programme incorporates our antiscalant CT 9190 and a microbial control programme incorporating a combination of oxidising and non-oxidising biocides together with a bio-dispersant.
An immediate improvement in the consistency of the water quality and, consequently, aluminium product quality, was achieved just by improving conductivity control.
The antiscalant dispersed inorganic deposits formed in the cooling tower, improving the cooling efficiency across the tower and reducing operational costs associated with cast cooling. The consistency of the aluminium product quality improved significantly with reduced product reworks and rejection.
Our biocide treatment programme has proven to be more cost-effective than the continuous application of chlorine gas, even though it is more complex in terms of the product combination. The combination of products and optimum dosage regime has reduced the microbial counts of the cooling water, contributing to improved water quality.
Less downtime and improved product quality
In conclusion, optimally managing the cooling water quality to the plant’s required specifications has decreased the level of production downtime and maintenance, and improved the consistency of the cast aluminium product quality. The customer has realised an improved market value for their product and significant operational cost savings.