Spotting the silent threat: when insulation fails and corrosion begins By Andrew Perks When do you know that the insulation has failed and there is corrosion going on at the pipework?
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INCORPORATING COLD CHAIN
Andrew Perks is a subject expert in ammonia refrigeration. Since undertaking his apprenticeship in Glasgow in the 1960s he has held positions of contracts engineer, project engineer, refrigeration design engineer, company director for a refrigeration contracting company and eventually owning his own contracting company and low temperature cold store. He is now involved in adding skills to the ammonia industry, is merSETA accredited and has written a variety of unit standards for SAQA that define the levels to be achieved in training in our industry.
Spotting the silent threat: when insulation fails and corrosion begins By Andrew Perks When do you know that the insulation has failed and there is corrosion going on at the pipework?
I
recently visited a customer in the Northern Cape who previously had an ammonia leak in one of his cold rooms. Well, the plant had been around for some time, so the question asked by the client was what I thought about the condition of the rest of the site’ s pipework. Do we do a patch job or go the‘ Full Monty’? The first reaction is“ replace it all”. However, there is cost consideration, not to mention down time. Nobody wants to take off all the insulation as they will need to replace it and who’ s to say that the pipework needs to be condemned- but the insulation most certainly would be.
While debating this, I was notified that IIAR were running a webinar on that very subject called‘ Clues and confirmation that your pipework is in jeopardy’. Now for you guys out there that are members of IIAR you will know that they have jacked up their presentations and have some interesting information available. This webinar was right on the money, and I would like to share some of the notable information with you.
The issue of corrosion on refrigeration pipework encompasses the entire plant. I know most people think it only happens under insulation, well not so. Some of the worst corrosion I have seen is on the highpressure side of the system around the condenser area. Corrosion does not exist in every instance of trapped moisture. From statistics raised in the webinar it is evident there is a level of predictability, as I will highlight later. Far too often corrosion will thrive with no external visual indications.
It was stated that an average of 25 % of pipework insulation is waterlogged, with levels fluctuating between 5 % to 89 %. No system pipework indicated the full quantity of moisture. During the IIAR study only 42 % of waterlogged insulation showed signs of the problem. So just because there is no moisture or ice on the surface of the insulation doesn’ t mean there is none beneath.
PIE CHART ' WET INSULATION '
The common cause of‘ wet insulation’ is a breakdown of the vapour barrier. This can be caused with poor consideration of expansion and contraction of pipework bearing in mind that the insulation is applied while the piping is hot, it will contract when cooled down in operation, mechanical damage caused by people walking on the pipework, poor bracketing etc. Vulnerable
28 www. coldlinkafrica. co. za COLD LINK AFRICA • July / August 2025