RR1134 - Maintaining the integrity of process plant susceptible to high temperature hydrogen attack. Part 2: factors affecting carbon steels
Carbon steel process plant that operates with hydrogen at elevated pressure and temperature can be weakened by a phenomenon known as high temperature hydrogen attack (HTHA). Hydrogen diffuses through the steel and reacts with carbon to form methane which builds up and degrades the steel's mechanical properties. If this phenomenon is taking place and continues undetected, it can potentially lead to failure of the process plant and a major accident. A fatal fire and explosion at the Tesoro Refinery in the USA in 2010 was caused by rupture of a hydrocarbon containing heat exchanger which had been weakened by HTHA.
HSE commissioned research to give a better understanding of maintaining the integrity of process plant operating in high temperature hydrogen service susceptible to HTHA. The research is described in two reports which should be read together. Part 1, RR1113, gives an analysis of the performance limitations of ultrasonic non-destructive testing techniques when searching for the presence of HTHA, and emerging technologies that may offer improved detection. Part 2, RR1114, discusses factors affecting HTHA for carbon steels including: the safe operating pressure and temperature envelope for plant ('Nelson Curves'); steel type, welds, stress and other material factors; and equipment operating history.
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