PIPES
such as valves will suffer corrosion under where dissolved oxygen levels are high, or if ammonia is present. Brass is also prone to dezincification when pH levels are not maintained.
Keeping corrosion at bay
So how do we keep corrosion at bay? An issue that can lead to millions of pounds in repairs and lost revenue in commercial systems that have been left to fester.
Apart from good system design and installation practices, checking water condition at every stage is key. The industry standard for this task has traditionally been sampling, a process that in my view has many flaws and should not be relied on as the sole means of detecting corrosion or it’s causes.
While I’m not suggesting (for now) that sampling be done away with altogether, as a process, it is fairly prehistoric in its methodology compared with the ways other operational elements of a building are tracked in the 21st century.
Sampling can give misleading results: Sampling provides information on the constituents of the water (bacteria and chemicals) which while indicative of system health, frequently misses important indicators of system wide problems. In particular, the presence of corrosion debris such
as iron or copper oxides can be under reported if they are insoluble or adhere to the walls of pipes and other components. High levels of bacteria (e.g. SRBs and pseudomonas) on the other hand may not be a problem if they are planktonic and not forming colonies under debris or biofilms. All this leads to false positives or negatives. A ‘sample’ is not good enough: Sampling only represents a snap-shot in time. Once a sample is sent to a laboratory for analysis, it can take many days for the results to return, by which time conditions may have changed. More importantly, sampling does not identify the root causes of corrosion problems which are nearly always systemic in nature. High dissolved oxygen, which is the primary cause of corrosion, is not measured by water sampling, nor are the situations that can cause this issue (low pressure or fresh makeup water). In-line sensors connected to data acquisition systems provide the obvious solution. During handover better accuracy is crucial. FMs and maintenance teams may be left with a water system that has been given a clean bill of health, when in fact underlying issues haven’t been picked up, leaving those responsible for ongoing upkeep to foot the cost.
Consigning corrosion to history Things are changing. In fact, the latest issue
of BG29 2020 – Pre-commission Cleaning of Pipework Systems, which was published very recently, includes whole sections on corrosion monitoring; an alternative or supplement to sampling that is far more effective at stopping corrosion in its tracks.
Remote corrosion monitoring technology detects corrosion rates as well as the parameters that can lead to corrosion – pH, inhibitor levels, pressure, temperature and crucially, dissolved oxygen. Hevasure’s solution provides 24/7 results, allowing for an accurate picture of water condition – during pre-commission cleaning and ongoing operation.
Changes in condition are instantly flagged, allowing for swift reaction and a far greater chance of finding the root cause of a problem. Our aim is to consign corrosion to the history books, and by being alerted to potentially corrosive conditions and dealing with them, there is effectively no need for corrosion to take hold. Whatever material is chosen for a closed circuit system, 24/7 remote monitoring technology will protect pipework and associated components from corrosion, alerting installers and maintenance teams to the changes in condition which can lead to serious damage, while giving specifiers peace of mind that they are passing on a system that meets and delivers the brief.
www.acr-news.com
September 2020 19
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