Ammonia Stress Corrosion Cracking

Last update: July 9, 2013

A form of stress corrosion cracking commonly occurring in brass tubes in cooling water service that is contaminated with ammonia due to biological growths or other contamination. This condition can also occur in carbon steel equipment, but unlike the cracking mechanism on brass which occurs in an aqueous solution, the cracking of steel equipment occurs in anhydrous ammonia.

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March 3, 2014, Greg Alvarado
The following question was posed by a member of the Inspectioneering Community: I am working in a fertilizer plant and our inspection team is very new. I was wondering if professionals in similar plants could share their knowledge related to inspection work. Please elaborate on details about the inspection function, as well as the main subjects we should focus on.

Inspectioneering Journal
By John Reynolds at Intertek
Ammonia stress corrosion cracking (SCC) has been around a long time. Most everyone has experienced it from time to time. It's not uncommon in brass tubes in cooling water service that is contaminated with ammonia due to biological growths or other contamination. Sometimes ammonia is added intentionally to process streams as a neutralizer by folks who do not know what it might do to brass tubes. Brass condenser tubes will fail brittlely when bent after they have significant ammonia stress corrosion cracking present. Eddy current inspection of brass tubulars is effective at finding ammonia cracking. Cupro-nickel alloys are usually not susceptible, and if necessary you can upgrade to austenitic stainless steels (which has it's own set of problems).

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