Ammonia Piping Failure Analysis

An international food processing company observed corrosion of their aging High-Pressure Liquid ammonia piping on a long run from the engine room to the processing plant so CEI^TM was hired to perform an engineering analysis and calculations to determine the safe operating pressure of the damaged piping. Non-destructive testing was done by a 3^rd party to obtain data on the extent of corrosion and CEI^TM utilized this data for a pipe strength analysis based on ANSI / ASHRAE STANDARD 15 and ASME B31.5. System P&ID’s, piping material and owner operating parameters were reviewed in detail for the analysis which determined that, at the worst point of measured corrosion, the piping had a 67.1% reduction in overall pressure rating. However, CEI^TM reviewed the P&ID’s and noted that the system was operated with safety relief valves set to release at 250 psig which meant that the maximum allowable operating pressure (MAOP) was well below the safe limit of the corroded piping and the risk of failure was minimal. CEI^TM made a number of recommendations to assist the owner with continuing to monitor the situation and mitigate risk.