GMAW Welding for B31.3 2

[AWH]

Can anyone comment on whether or not if GMAW welding is permitted for use in B31.3? Our company has WPS & PQR (for P#1 and P#8) on file approved for ASME Section IX. The WPS and PQR was approved by a CWI.

 

[Bamend]

B31.3 references the requirements of Section IX and does not prohibit GMAW. Your Section IX procedures should be OK as long as the qualified joint designs and other essential variables meet the requirements of the B31.3 application, you have good confidence in the current skill level of the welders with the specific GMAW procedure, and you have selected the appropriate NDE methods relative to the types of weld flaws that may be present and the service requirements

 

[moltenmetal]

GMAW, properly qualified, would be fine after the root. As a root pass it might be a little more troublesome to get sound manual welds that pass RT. But it is done- some automatic "robotic" pipe welding machines use GMAW for the entire weld.

 

[gtaw]

GMAW has a dark cloud over it because there are four possible modes of metal transfer, each with different operating characteristics.

ASME Section IX has certain restrictions on the short circuitig mode of metal transfer that limits the thickness range for which you are qualified.

Short circuiting transfer produces rather limited heat input, thus prone to fusion type discontinuities unless the welder is properly trained and close attention to cleaning, joint preparation, and welding parameters are controlled.

The contractor must be aware of the limitations and which mode of metal transfer is being used.

Best regards - Al