Some Resources to Learn More about Preventing High Temperature Hydrogen Attack (HTHA)

By Jeremiah Wooten, Managing Partner at Inspectioneering. January 20, 2014

Last week we mentioned three important tips to consider when addressing high temperature hydrogen attack (HTHA). This week, we'd like to provide the reader with a few helpful resources that deal with the topic of HTHA.

What is High Temperature Hydrogen Attack?

High Temperature Hydrogen Attack is a potentially dangerous damage mechanism that can occur in process equipment that is exposed to hydrogen at elevated temperatures over time and under dry conditions, when hydrogen disassociates into nascent (atomic) hydrogen and is then driven into the steel by the temperature and pressure of the environment. That atomic hydrogen then reacts with unstable carbides in the steel to form methane gas, which then causes gas pockets to form and leads to material degradation.

In 2010, HTHA was to blame for a tragic incident at a Washington, USA refinery when the shell of a feed-effluent heat exchanger in a naphtha hydrotreating (NHT) unit ruptured, ultimately resulting in seven fatalities. Since this incident, the subject of HTHA and inspection for HTHA has been extensively discussed at well-attended meetings on the topic at NACE, API, and AFPM events, indicative of the high level of attention it has received as operators continue to struggle to understand and detect this insidious damage mechanism. Joint Industry HTHA projects have commenced and new examples of HTHA have been submitted to the API Recommended Practice (RP) 941 committee for consideration for inclusion of these new experiences in future updates of the standard.

HTHA Resources

If you are looking for more information about HTHA, there are a number of great resources available. 

  • The Inspectioneering LinkedIn Group is a resource for industry professionals to discuss asset integrity topics including HTHA. Group membership is free.
  • Inspectioneering's HTHA topic page contains hyperlinks to HTHA-related articles that have been published in Inspectioneering Journal and on
  • API RP 941 establishes practical operating limits for carbon and low alloy steels in hydrogen service at elevated temperatures and pressures.

Feel free to leave comments using the form below. Let us know where you go to learn about HTHA, damage mechanisms, and anything and everything related to corrosion and materials.

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