How to stop piping corrosion
How to stop piping corrosion
(OP)
Hi all,
I work in the modular construction industry, where we sometimes have a chilled water system incorporated into the design. Before construction, we treat the piping with a corrosion inhibitor which is water soluble.
There was a requirement by a customer to do the flushing of piping before shipping the modules to the site, however after the flushing, the water-soluble inhibitor was removed, and since the system was not immediately filled with water, the corrosion started to appear. I talked with a representative from one corrosion inhibitor company who suggested filling the system with inhibitors in a vapor state or filling the system with a mixture of water and inhibitor. How do you usually deal with this sort of matter?
I work in the modular construction industry, where we sometimes have a chilled water system incorporated into the design. Before construction, we treat the piping with a corrosion inhibitor which is water soluble.
There was a requirement by a customer to do the flushing of piping before shipping the modules to the site, however after the flushing, the water-soluble inhibitor was removed, and since the system was not immediately filled with water, the corrosion started to appear. I talked with a representative from one corrosion inhibitor company who suggested filling the system with inhibitors in a vapor state or filling the system with a mixture of water and inhibitor. How do you usually deal with this sort of matter?
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RE: How to stop piping corrosion
MJCronin
Sr. Process Engineer
RE: How to stop piping corrosion
RE: How to stop piping corrosion
Didn't the customer have this requirement also?
Yes, it will need to be acid cleaned before any inhibitor can help slow the pitting.
But once pits form the best you can hope for is to slow them down.
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P.E. Metallurgy, consulting work welcomed
RE: How to stop piping corrosion
I am not a corrosion expert, but the corrosion started to appear (surface undergoing coloration to orange at some places), but at that point, I didn't observe pittings.
I have read Lay-Up procedures with inert gas could be used to protect piping from corrosion after hydro test/flushing. Would such a procedure where the piping is drained and refilled with nitrogen on pressure higher than atmospheric pressure be sufficient, even though there would be some water inside? I assume the nitrogen would push the oxygen outside the system and the only oxygen present in the piping would be the one dissolved in the leftover water so there would be less corrosion?
RE: How to stop piping corrosion
Typically you blow hot dry air for a while and then do the Nitrogen fill.
My guess is that if you cleaned some of the most rusted areas and looked with magnification you would see the start of pitting.
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P.E. Metallurgy, consulting work welcomed
RE: How to stop piping corrosion
I see. I assume that hor air drying duration would depend on atmospheric conditions and probably could last long. Are there some common conditions that are required to say that the pipe is dry?
Thinking out loud, would it also make sense to circulate the air through installation and have some sort of desiccant dehumidifier which could take out the moisture from that circulated air?
RE: How to stop piping corrosion
RE: How to stop piping corrosion
RE: How to stop piping corrosion
Once the outlet RH stops dropping you can then look for ways to dry the inlet air (such as desiccants on the intake before heating).
Then finishing with Nitrogen until the exit dew point is low enough.
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P.E. Metallurgy, consulting work welcomed
RE: How to stop piping corrosion