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Ignorance is not bliss when it comes to pipework corrosion


Drawing on data collected from real-time remote monitoring systems over the past eight years, Steve Munn from Hevasure, explains some of the issues that commonly occur in HVAC pipework and how they can be prevented


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orrosion of pipework and other components is a serious issue that eff ects the majority of closed LTHW systems at some stage in their


lifetimes. If indicators are not picked up early on, small issues can turn into big problems leaving critical infrastructure vulnerable to breakdown, expensive repairs and even catastrophic failure. Over 50% of the UK’s commercial buildings have potential corrosion issues in their closed-systems – the essential pipework and plant which keeps water-based HVAC operational - according to data we have collected since 2014. Our study looked at 86 commercial buildings in the


UK over an eight-year period. A total of 1,812 issues that indicate adverse conditions were detected, many of which would have gone unchecked if sampling had been the sole means of review. For example, elevated dissolved oxygen (DO) was the most common problem, accounting for 25% alarms triggered through the monitoring systems. DO is the precursor to most types of corrosion and something that is not detected through sampling alone.


Hevasure Aquila-2


The Hevasure Aquila-2 range provides full water monitoring, detecting the parameters that can signify corrosive conditions at all stages of a water systems life – from precommission cleaning onwards.


Parameters checked for include dissolved


oxygen, make-up water fl ow, pressure and pH. The standard Hevasure Aquila-2c unit includes cloud connectivity, with alerts sent direct via SMS or text message. Hevasure Aquila-2s is a BacNet enabled


model, allowing direct connection to a BMS system with pre-set alarms, designed for high- security locations where external transmission to the cloud is prohibited. Aquila-2+ combines the functionality of 2c


and 2s, allowing remote access to data and connection to the BMS.


levels and/or good inhibition of metallic surfaces. ¡ Crevice corrosion - Crevice corrosion can occur even if general corrosion rates are low. It occurs in localised regions, such as weld seams, crimpled joints or under debris, due to diff erential aeration eff ects and is a frequent cause of pitting attack and pin-holing.


Look for the root cause


Pipework problems Routine water sampling has been widely used in commercial HVAC systems for many decades. However, the problem with this approach is that is only represents a snapshot in time and misses most of the causes of corrosion. A far more eff ective approach - and one that


is more in step with modern building services management - is to monitor the early indicators of corrosive conditions so that preventative interventions can be made, including: ¡ Dissolved Oxygen - Closed heating and chilled water systems need to be air-tight to prevent the ingress of dissolved oxygen. For a typical closed system, dissolved oxygen levels should be around 0.1 to 0.2 mg/L. ¡ Pressure – Positive (but not excessive) pressures must be maintained to prevent air being drawn-in. ¡ Temperature - This is a key parameter of any HVAC system and needs to be constantly checked to ensure it is operating at the intended level. ¡ Conductivity - For systems dosed with chemicals, conductivity is directly related to concentration. Measuring this parameter is essential to ensure that minimum thresholds are maintained, otherwise inhibitors are ineff ective, and glycols off er insuffi cient freeze protection. Conversely, over- dosing is an environmentally unacceptable and an expensive waste. ¡ pH - Must be maintained within the limits set by the chemical supplier in order to ensure metals are immune from corrosion or adequately passivated. ¡ Galvanic currents - The galvanic current is the current that fl ows between diff erent metals within a system, for example, steel and copper. Maintaining low galvanic currents is indicative of low oxygen


These parameters are early warning signs that corrosion may be about to occur and by monitoring them, FMs and building managers can identify the root-cause of a problem and take early action to prevent costly downtime and repairs. Where sampling is the main source of checking


condition, true problem solving and certainty of resolution is hard to achieve. That is one of the reasons why remote real-time monitoring is now recommended in BSRIA guides BG50/2021 – Water Treatment for Closed Heating & Cooling Systems and BG29/2021 – Pre-commission Cleaning of Pipework.


The value of prevention


Our study shows that for many years, commercial buildings have been under threat from the hidden menace of corrosion. The knock-on eff ect of this vulnerability is potentially disastrous, with responsible parties (often facilities managers) open to litigation and critical HVAC systems at risk of breakdown. To mitigate this risk, FMs must understand the long-term value of prevention. Real-time HVAC monitoring technology is the


only way to prevent pipework corrosion and its associated costs. This approach also brings the added benefi ts of leaner maintenance practices, reduced need for site visits and improved sustainability, thanks to the potential to cut fl ushing requirements, optimise chemical use and increase component longevity. When it comes to pipework corrosion, ignorance


is far from bliss. FMs need a true and accurate picture of their HVAC systems to make informed and cost-eff ective choices. Hevasure has published a white paper, ‘Behind


the scenes of closed-system HVAC’ which examines its fi ndings over the past eight years and introduces the new range of corrosion monitoring technology, Aquila-2.


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Pipes, valves & fi ttings


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