Micro hardness tests may be conducted to ensure that welding does not affect the toughness of some hydrogen pipe materials. These tests can be part of the welding procedure and operator qualification process, and they can also be performed on samples from

Micro hardness tests can be performed to verify that welding does not compromise the toughness of specific hydrogen pipe materials. These tests may be included in the welding procedure and operator qualification processes, and they can also be conducted on samples from welds produced during manufacturing. Hardness testing is mandated for welding procedure qualification tests on certain materials that have acceptance criteria specified in ASME B31.12, as outlined in the table below.