By Eamonn Ryan, from a TechTalk hosted by SAIRAC Cape Town Centre.
In a recent technical talk, Pieter de Jager, owner of Procontrol, a leading provider of water treatment solutions, shed light on the critical importance of effective water treatment in cooling systems. This is Part 4 of a 5-part series.
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 severe scaling potential. In such cases, diluting the sample is 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.
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 cost-effectiveness of implementing comprehensive water treatment programmes. He also emphasises the importance of understanding make-up water sources and adhering to equipment manufacturer specifications.