www. refrigerationandaircon. co. za RACA Journal I July 2025 15
Associations associated with using borehole water in general. When borehole water, often containing higher levels of iron, is exposed to air in open dams, the iron oxidises and precipitates out, potentially causing fouling and other issues in the downstream systems.
Returning to cooling systems, De Jager points out variations in dosing system configurations based on specific needs. For systems with multiple towers sharing common lines and isolation valves, they
Addressing the problem of biological growth, de Jager advocates for the use of biocides implement dosing on the common line over chlorine or chlorine derivatives. to ensure continuous chemical treatment severe scaling potential. In such cases, diluting the sample is regardless of which tower is operational. He presents an example of a control panel with two diaphragm pumps, catering to such scenarios, sometimes alongside a peristaltic pump for specific dosing requirements.
The discussion then turns to the connectivity controller in more detail. De Jager emphasises the added benefit of these controllers displaying the water temperature, providing an immediate indication of potential system anomalies. Furthermore, he explains the integration capabilities with BMS systems via a 4-20 milliamp signal, allowing for remote monitoring of conductivity levels. The controllers also feature dual relay outputs. The primary output typically controls the bleed-down valve, while the secondary output can be programmed to trigger alarms( visual or within the BMS) if the conductivity deviates from the set parameters, either going too high or, unexpectedly, too low. This low conductivity alarm can indicate issues like excessive bleed-off or a significant influx of dilution water.
Addressing a question about the pink colourant, phenolphthalein, De Jager confirms its use in closed-loop systems as a visual indicator of both pH and potential leaks. He also clarifies that while some nitrite-based products are pre-coloured pink, Procontrol uses a powdered nitrite and adds the colourant separately. This choice is primarily logistical, as a single 25kg bag of their powder is equivalent to multiple bulky liquid containers.
De Jager stresses that the continuous evaporation in cooling towers leads to a concentration of dissolved salts and minerals. Even with relatively clean make-up water( e. g. 80 μS in Cape Town), the conductivity can escalate significantly over time. He recounts instances where conductivity levels were so high that the water exhibited a slight yellowish tinge, a clear indicator of
necessary to even measure the conductivity.
Responding to a question about alternative biocides like chlorine dioxide, de Jager firmly advises against their use in cooling towers. He emphasises that chiller manufacturers would likely void warranties if chloride levels are elevated. Chlorine, being a potent oxidiser, is corrosive to the metallic components of cooling systems, leading to paint degradation and eventual rusting.
ADDRESSING IRON ISSUES AND EMBRACING PROACTIVE WATER TREATMENT STRATEGIES In the final segment of his technical talk, De Jager tackles specific water quality challenges, particularly the presence of iron, and reiterates the long-term benefits and costeffectiveness of implementing comprehensive water treatment programmes. He also emphasises the importance of understanding make-up water sources and adhering to equipment manufacturer specifications.
Responding to a question about treating systems with high iron content, De Jager first stresses the importance of identifying the source of the iron, especially in closed-loop chilled water systems where make-up water additions should be minimal. The primary solution involves a thorough drain and flush process, repeated until the water runs clear. Once the iron-laden water is removed, the system is refilled and treated with the standard nitrite-based corrosion inhibitor, along with
“ De Jager stresses that the continuous evaporation in cooling towers leads to a concentration of dissolved salts and minerals.”
Image by Freepic. diller / Freepik
www. refrigerationandaircon. co. za RACA Journal I July 2025 15