ASME B31.3 Process Piping Code Changes

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Important Code Changes.  Our IRISNDT Engineering group highlights changes to the 2020 edition of ASME B31.3 Process Piping Code, to be enforced in the next year, which will impact fabricators and owners of existing piping:

Until now, weld metal deposits needed impact test qualifications at minimum design metal temperature (MDMT) of -29°C (-20°F) or lower.  In the 2020 edition, the threshold temperature has been moved to -18°C (0°F).  This change applies to most carbon steel piping in use.

Consequently, the existing piping classes with MDMT of -29°C will have to use impact tested welding procedures for new piping fabrication.  Alternatively, the design MDMT for such piping classes will need to be revised to -18°C (once the new code edition is in effect).  Note that impact testing of weld metal deposits will not be required when certain welding consumables that are certified through their classifications for low temperature service (at or below the MDMT) are used.

Why such a drastic change?  Many flange, fitting, and piping failures have happened recently due to changes in fabrication practices.  The changes are ASME’s response to reduce the failures.

In another important change, the B31.3 weld thickness qualification requirements have been harmonized with those of the ASME BPVC Section IX.  This change expands the coverage of existing impact tested welding procedures to a broader thickness range – it makes the life of fabricators, owners, and testers easier.

The ASME website has a list of the key changes (