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.

 

[DekDee]

metaleng123,
This is a question for your client.
Submit a repair request to them.
If this was discovered after PWHT it would be a different story but a localised repair (20 mm) prior to PWHT should be no problem.
What is the fabrication / construction code ?

 

[r6155]

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

What does ?????. Could you explain it?
Do you understand that the welder is a candidate for an award?

 

[DekDee]

Why would 1 x repair require a retest.
That is ridiculous.
You do nothing but post negative comments.
If there was a BLOCK button I would be using it right now.

 

[weldstan]

Yes the repair can be done. I have seen a number of such repairs been unsuccessful, finally requiring a complete cutout and reweld. You may have to make the repair area/length somewhat larger to effect a successful repair. I assume that you found the defect through RT before PWHT.