B31.12 Preheat Requirement Conflict

[JasonVella]

G'Day Team,

My team is working on a hydrogen project, and we are using that latest version of B31.12 (2023).

We are using A106 Grade B carbon steel pipe (DN150 to DN200 Std Wt). The preheat table (I believe it is GR-3.5-1) lists a preheat of 10°C for this material and wall thickness.

Section GR-3.4 (d) states
"Welding shall not be performed when the temperature
of the metal surface within 305 mm (12 in.) of the
point of welding in all directions is lower than 16°C (60°F).
The work area and surfaces to be welded shall be
protected from wind and moisture conditions caused
by ice, rain, snow, and running or standing water."

This hasn't change from B31.12 (2019) when the above preheat requirement was 80°C (Table GR-3.5-1 from B31.12 2019).

Has anyone obtained clarification from ASME if this is a error as it does not make sense that the preheat table lists a value lower than the reheat requirement.

Any help would be appreciated.

 

[gwalkerb]

To me it looks like they updated Table GR-3.5-1 but missed the inconsistency with section GR-3.4 (d). You could contact ASME yourself to find out the answer, and in the meantime, just use 16C as your minimum allowable preheat temperature. Both locations define the temperatures as a minimum temperature, so 16C is fully compliant with both locations.