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 5 of a 5-part series.
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 an initial higher dose of biocide to address potential microbial growth associated with iron contamination.
For new systems or those with persistent high iron levels in the make-up water, De Jager describes the use of iron removal units installed in the fill line. These typically consist of a fibreglass vessel containing a specialised media (cationic resin, not just sand or glass) and an automated backwash system to remove the trapped iron.
Addressing the use of alternative water sources like rainwater and condensate, De Jager notes that while condensate from air conditioning units is generally of good quality, borehole water can vary significantly. He cautions that using alternative water isn’t always cheaper than municipal water. The costs associated with the necessary pre-treatment, including pumps for extraction, circulation and backwashing, as well as the ongoing maintenance and replacement of components like pH probes, can quickly add up. He advises a careful cost-benefit analysis before opting for alternative water sources, especially when municipal water is readily available. He cites a local college’s unsuccessful attempt to use canal water due to the unforeseen costs and complexities of treatment.
Regarding air-cooled systems, De Jager acknowledges that while they eliminate the need for extensive water treatment for heat rejection, they can experience issues with slime formation on the fins due to condensation and airborne dust. The solution in these cases is typically a direct application of diluted biocide to the affected areas.
A key challenge in implementing effective water treatment in closed-loop systems is accurately determining the system volume. De Jager admits that this is often an initial unknown. While installing a water meter during the initial fill is the most precise method, estimations are often necessary. He points out that while minor inaccuracies in volume estimation might not drastically affect initial chemical dosing, significant discrepancies, especially in large systems like data centres, can lead to problems. He recounts an instance where a newly built data centre filled its chilled water system with poor-quality tanker water during a drought, resulting in severe iron contamination that required the installation of large iron removal units for an extended period. Eventually, a complete drain and refill were necessary. This highlights the critical importance of using good quality make-up water from the outset.
De Jager reiterates the long-term cost savings and equipment protection afforded by proactive and automated water treatment programmes. He emphasises that while manual dosing might seem like a cheaper alternative, it often leads to inconsistencies and ultimately higher costs due to inefficiencies and potential equipment damage. The automated systems offered by Procontrol ensure precise and proportional chemical dosing, optimising treatment effectiveness and minimising waste.
The session concludes with a strong recommendation for industry professionals to upskill their knowledge in water treatment. Understanding the fundamentals and being able to identify potential water-related issues can empower technicians and protect them from liability arising from inadequate water management. De Jager encourages the audience to utilise online resources, particularly educational videos from reputable chemical companies, to further enhance their understanding of this critical aspect of HVAC and other industrial systems. The final piece of advice is a crucial reminder to always consult and adhere to the water quality specifications provided by condenser and chiller manufacturers to safeguard warranties and ensure the long-term reliable operation of the equipment.