Restrictions by back gouge technique in ASME IX

[Hollan Petersen]

Need to prepare WPS/PQR/WPQ for plate welding using GTAW process in a double v groove joint design with back gouge and I was wondering if I could weld also pipe in a single v groove design simply issuing a new WPS and using the same PQR/WPQ.

[wgadmin]

As far as the WPS/PQR are concerned, by the QW-256 it is made clear that the groove design as well as the back gouge technique are considered as nonessential welding variables and thus you don’t need a requalification. For welding of pipe, please note that a new WPS shall be issued based on the existing PQR and taking into consideration all of the relevant restrictions coming by the ASME IX (base metals, thicknesses, filler metals, etc.). Please have a look to the QW-200.1(c).

As far as the WPQ is concerned, by the QW-356 it is made clear that the deletion of the backing is an essential welding variable and since a double v groove joint is considered welding with backing, if you indent to weld pipe in a single v groove design, you have to requalify your welder.

Concluding, I would like to clarify that, even it seems strange that the WPS does not need requalification since the welder needs, it comes by the fact that ASME IX considers essential variable for procedure a change in a welding condition which will affect the mechanical properties of the weldment (QW-401.1), since it considers essential variable for performance a change in a welding condition which will affect the ability of a welder to deposit sound weld metal (QW-401.2).