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Recent developments in real­time monitoring have transformed the way we monitor and maintain HVAC systems after handover, leading to a significant update of BSRIA’s BG50 ‘best practice’ guidance at the end of last year. Tom O’Sullivan, head of operations for Guardian Water Treatment, explains what has changed and how FMs can improve management and maintenance practices in­line with the latest thinking, resulting in healthier buildings that use less energy and cost less to run


often mismanaged. If corrosion is allowed to take hold it can be very difficult and expensive to correct. Operational inefficiencies or failure can cause serious damage to expensive assets, with the cost of repair and downtime potentially running into the millions.


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When things go wrong, traditional methods of testing and treatment are often impractical, with maintenance access limited to outside of working hours and the risk of treatment destabilising the system. This can leave FMs in a precarious position, with a HVAC system that is unreliable or costing too much to run and little insight into how to remedy the situation effectively.


Out with the old…


Effective monitoring is critical, however, until relatively recently, the means for checking and analysing water condition within closed circuit water systems was decidedly old-fashioned, considering the role that HVAC systems play in modern commercial buildings.


In 2013, when BSRIA published its previous guide to Water Treatment for Closed Heating and Cooling Systems (BG50), water sampling and corrosion coupons were the mainstay of detecting water quality and corrosion.


However, these processes have significant shortcomings:


• Sampling only represents a snapshot in time • Results take days to return, by which time conditions may have changed • Sampling does not successfully detect for oxygen, the precursor to almost all types of corrosion


• Chemical and bacterial sampling results can be misinterpreted especially if contaminants are sessile (where they adhere to surfaces) or become sequestered.


• Corrosion coupons do not measure corrosion rates in real-time and therefore will not detect the moment limits are exceeded.


The sampling and corrosion coupons approach often went hand-in-hand with over-flushing and heavy use of chemicals, processes which in themselves can lead to pipe degradation.


The picture presented by these old school methods was incomplete – particularly as they do not detect dissolved oxygen (DO), which we now know as the root of all corrosion within closed systems – leaving problems to fester, unseen.


…in with the new


Since then, monitoring methods have moved on at great pace, most significantly the development of Hevasure’s ground-breaking remote monitoring technology in 2014. Drawing on many years of experience in the water treatment sector and fed up with seeing the same old problems with corrosion, brothers Steve and Phil Munn set out to design a system that protected commercial systems from the onset of corrosion, allowing responsible parties to act before the damage was done.


At this point, real-time data acquisition and BMS systems were well established in other areas of building management – why shouldn’t corrosion monitoring of closed systems be the same? Utilising developments in IoT technology and incorporating cloud-based data acquisition systems and high-quality sensors, it is now possible to remotely detect a wide range of parameters in real-time enabling FMs to execute more effective service interventions.


Hevasure’s intelligent monitoring system tracks corrosion indicators including DO, pressure, pH, pressure, inhibitor levels and galvanic currents. It’s unique and 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.


With the benefit of cumulative data, FMs have the benefit of accurate information and analysis at their fingertips. If critical levels are exceeded, responsible parties are immediately notified enabling swift rectification.


HVAC monitoring – the ‘best practice’ way


BSRIA has recognised this shift from manual to data driven in the latest edition of BG50, which for the first time acknowledges DO as one of the key contributing factors to corrosion in closed systems and specifies 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


24 BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2022


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.


Compared with sampling, real-time corrosion monitoring is far more accurate and instantaneous, providing a comprehensive indication of system conditions and water quality and critically, it is the only way to detect the presence of DO.


At Guardian, we’ve used real-time monitoring as part of our water treatment services since 2017. By using the Hevasure 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-flush the system back to pre-contamination condition.


Take back control


As a permanent installation, a real-time monitoring system can give maintenance team early warning of conditions likely to promote internal corrosion and provide information that will lead to more effective preventative maintenance programmes. This is the ideal scenario, firmly putting FMs back in the picture and giving the right information to enable active service interventions and informed water treatment decisions.


Alternatively, a corrosion monitoring system can be used as a one-off ‘health check’ – monitoring a system over a specific period to ensure it returns to spec following flushing, or to build an accurate picture of ongoing issues.


While BSRIA guidelines are not legally binding, the latest edition of BG50 is an important document for FMs and their teams. Alongside in- depth technical guidance on a range of water treatment techniques, it now incorporates the very latest thinking on the management and maintenance of closed-circuit water systems. With the benefit of an intelligent monitoring system, maintenance engineers can ensure buildings are performing sustainably and cost- effectively – with no hidden surprises in the pipeline.


Guardian Water Treatment has launched ‘BG50i’, an intelligent maintenance and real-time monitoring package, designed to help responsible parties, such as facilities managers and maintenance teams, meet the requirements of BSRIA’s BG50/2021.


Read the latest at: www.bsee.co.uk


losed heating and cooling systems are essential for the efficient operation of HVAC plant in large commercial buildings, but these complex systems are unfortunately


WATER TREATMENT Updates to BSRIA BG50: what’s changed in HVAC monitoring?


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