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Meeting the guidance for closed water system
optimisation C
Steve Dawson from Guardian Water Treatment explains why updated BSRIA guidance will help building owners and maintenance teams look after essential HVAC pipework and associated components in a more prescriptive, robust and sustainable fashion, leading to reduced risk of corrosion, preventing costly downtime
losed heating and cooling systems are essential for the effi cient operation of HVAC plant in large commercial buildings, but these complex systems were historically often mismanaged. Recent developments in real-time
monitoring, however, have transformed the way we monitor and maintain systems, during precommission cleaning and after handover. This has led to signifi cant updates to BSRIA’s BG29 and BG50 ‘best practice’ guidance. A closed-circuit HVAC system can seem like a mystery, with no visual clues as to what is going on inside pipework and associated components until it’s too late. For years our industry relied on water sampling to determine condition, a process that is fi lled with fl aws – sampling only represents a snapshot in time, it cannot successfully determine dissolved oxygen (DO) levels and results take days in not weeks to return, by which point conditions may have changed. At every step of the chain, from precommission cleaning through to handover and ongoing maintenance, the next team along was potentially inheriting (and taking fi nancial responsibility for) a system with hidden problems that had not been identifi ed. Thanks to the development of remote closed-system monitoring, which
provides a constant and accurate picture of what’s going on inside the pipework, the days of being in the dark are well and truly over. This is refl ected in the latest iteration of BG50, BSRIA’s guide to water treatment for closed heating and cooling systems.
Data driven and DO focussed
BG50/2021 recognises the shift from manual to data driven condition monitoring. For the fi rst time, it acknowledges DO as one of the key contributing factors to corrosion in closed systems and specifi es real-time monitoring technology as the key mitigating factor. BG50/2021 states that: “The level of dissolved oxygen is the most important
factor related to corrosion, and that laboratory sampling is not suitable for testing for DO. Whilst we have always understood that oxygen causes corrosion – either directly, or indirectly as the precursor to Microbial Induced Corrosion (MIC) - until the advent of monitoring technology, there was no way to successfully detect its presence.”
Real-time monitoring is already the mainstay of other parts of a building and its services - BMS systems are well established in other areas of building management. At last, the closed, behind-the-scenes essentials of HVAC have caught up.
We use Hevasure’s intelligent monitoring system, which tracks corrosion
indicators including DO, pressure, pH, pressure, inhibitor levels and galvanic currents. Its patented sensor provides early indication of crevice corrosion; a particularly insidious form of corrosion which occurs in localised regions such as weld seams and under debris where a micro-environment can be formed. By using the unit alongside sampling and corrosion coupons, we’ve shown that
the real-time monitoring approach enables systems to be brought back within spec much more quickly, providing critical data within days compared to weeks with sampling alone. In one example, the use of real-time monitoring saved a client £200,000 by preventing the need to re-fl ush the system back to pre- contamination condition.
Real-time monitoring from the outset
BG50 focuses on water treatment from the point of handover, but real-time monitoring has its place at the precommission cleaning stage too, ensuring water systems start life in the best possible condition. BSRIA’s guide to this part of the process is BG29 which was updated in 2020 to refl ect the benefi ts of 24/7 remote monitoring. In-short, everyone in the closed-system HVAC food chain should be taking note
of real-time monitoring; the benefi ts don’t just end in cost-savings and reduced breakdown risk. A monitored system is also likely to be more sustainable, thanks to improved effi ciencies due to less system fouling, and the potential to save large volumes of water – particularly at the precommission stages. Precommission cleaning is one of the most water-wasting processes in a building’s construction. Where a true picture of condition can be achieved, fl ushing may be reduced and used only when it is necessary, rather than a reaction to a perceived but often unsubstantiated risk. This is true throughout a water systems life; we often see a heavy handed approach to fl ushing where corrosion monitoring technology isn’t utilised. Overall, with the benefi t of an intelligent monitoring system, maintenance
engineers can ensure buildings are performing at their peak, helping meet lifecycle design specifi cation, with no hidden surprises in the pipeline.
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Water treatment
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