Weld Repair metallurgical influence in Gr.91 welds

[metaleng123]

Dear eng-tips,

What would happen in an already existing HAZ after performing a weld repair?

More info:
- materials SA335 P91 and A234 WP91. After NDT was performed incomplete penetration was spotted, dimension of the pipe and cap is 355,6 x 11,13 mm so re-welding form the inside is not possible.
PQRs and WPQs were properly qualified using GTAW process.

If anyone is kind enough to offer some insight I can provide more details if necessary.

 

[r6155]

This is due to a lack of inspection at the root of the weld.
The welder has failed and a retest is required.
The defective weld is not approved.

 

[DekDee]

This is due to a lack of inspection at the root of the weld.
The welder has failed and a retest is required.
The defective weld is not approved.

?????????????
The welder has failed and a retest is required. ???????

 

[metaleng123]

Thank you for all your replies so far.

The welder has passed the required skill test and welded a PQR ( ASME IX) piece with succesful results ( both NDT and Mechanical testing).

The above mentioned defects were found during fabrication on the project. As r6155 said, the defect's root cause is lack of inspection.

Right now I'm trying to find the best approach to a weld repair. In my opinion, my two options are band saw the entire weld and re-bevel or grind the whole area where the defect is located ( about 20mm in lenght) and re-weld following the essential varables of the PQR.

As i find more info. regarding ways to appraoch HAZ cracking ( the entire Weld + HAZ cut out) I was left with the question if it's ok to re-weld over the existing HAZ.