Class Locations (3)

Class Locations (3)

Criticality: High
Progress: Not Addressed
Score: 40
DOT Relevance: 192.5

Description of Key Area

Class location comprises a portion of Subpart A (General) of 49 CFR 192. Class location refers to the distance a structure must be located from the pipeline. A class location unit is defined in 49 CFR 192 as an on-shore area that extends 220 yards on either side of the centerline of any continuous 1-mile length of pipeline.

Discussion of Criticality

The parameters for class location are based on natural gas considerations. The underlying definition of class location must be redefined for hydrogen.

Discussion of Progress

The current plans of the ASME B31.12 hydrogen task group call for using only the location class 3 and 4 to maintain a classification designation familiar to pipeline operators and designers. This will increase the level of conservatism in the design of new lines and require more frequent inspections in the integrity management process. The ASME B31.12 hydrogen task group is also reviewing a new DOT report, TTO13, entitled Potential Impact Radius Formulae for Flammable Gasses Other Than Natural Gas, June 2005. If the task group agrees with the report results, it will change the potential impact area equation for radius of impact calculations and use this in conjunction with ASME B31.8S (equation 1 in ASME B31.8S, section 3.2).


The ASME effort should be monitored and its recommendations assessed for potential incorporation by reference into the federal code.