The updated include data for modern steels and account for hydrogen partial pressure up to 100 MPa. Selection guidelines:
Carbon steels are most susceptible due to their high cementite content (Fe₃C). Typical operating limits per API 941 for carbon steel: approximately 220°C at 3.5 MPa H₂ partial pressure. Above 260°C, rapid attack occurs. Attack manifests as: htri crack
Some older API inspection guidelines and internal company standards still use “HTRI-type cracking” to describe shallow, non-stress-oriented HTHA. This has caused confusion: some engineers mistakenly believe “HTRI cracks” occur only at weld toes or under certain heat transfer conditions, whereas HTHA occurs uniformly in susceptible microstructures regardless of heat flux. The updated include data for modern steels and
