NDE requirements after PWHT

[C.Hoback]

Hello all,

When performing a repair on vessel or piping requiring post weld heat treat and the existing pressure containing welds are included in the heat treatment, does all the existing weldments require volumetric testing?

This question has come up several times and I always get mixed opinions. Anytime I stress relieve a part I like to perform NDE as the heat input may open up defects in the weldment.

However, on older equipment, this can bring up additional issues since the acceptance criteria was not as stringent as the current codes.

Also, my understanding is I can evaluate the defect to the original fabrication code but we do not always have that luxury with piping and the weld would need to be evaluated to the current code. This would likely cause additional repairs be made.

All feedback would be appreciated!

 

[goutam_freelance]

I see no requirements other than 'metal outside the soak band shall be protected such that temperature gradients are not harmful'. With such protection there may not be requirement of additional NDE.
But in case the temperature gradients are significant, some NDE should be done in the affected zone (in my opinion).

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[r6155]

1) PWHT and NDE depends of service (low temperature, lethal,...etc.), material and wall thickness.
2) 100% Visual examinations before and after PWHT
3) Hardness test before and after PWHT
4) All defects shall be repaired and NDE.

Regards

 

[weldstan]

NBIC would only require volumetric tessting on the repair welds for vessels under its governance but you may wish to perform more NDE on some adjacent welds. Normally local PWHT would be performed on the repair.

 

[DekDee]

C.Hoback,
Not sure if this is applicable to your situation but thought I would share.
I spent 4 years as a radiographer and my boss warned me many times to do everything we could to not include original welds in new radiographs.
If we picked up part or all of any existing weld with defects the client would not be impressed.
The weld may have been in service for 20 years but that means nothing - if we picked it up by mistake we have to evaluate and sentence with the current code as you noted.
There is an interpretation in B31.3 that if my memory serves me correctly states that if you repair a weld on a spool and the spool gets re-PWHT it is only the repair weld that needs NDT post PWHT.
On R&R at the moment so on my return will try and locate it.
Cheers,
Shane

 

[r6155]

@ DekDee
Your boss was wrong. A radiographer never decides the location where the RT is performed. The inspector decides.

Regards

 

[DekDee]

r6155,
I think you have misunderstood my post.
The client has requested 1 x new weld be radiographed.
The film is put on incorrectly and an adjacent circ weld (possibly 20 years old) has been captured on the film as well.
Both welds must be interpreted and sentenced and the client will be most unhappy if a repair is called in a weld that was never requested to be shot.
Regards,
Shane

 

[r6155]

Shane, thank you. Now is clear to me.

The client or the inspector must clearly indicate in the pressure vessel the location and extension of RT to be performed. This is a classic communication problem. The client must pay for his mistake.
The radiographier should require this information before performing the RT. The radiographier must pay for his mistake.

The client should be grateful for the news of a defect discovered, if he is a serious client.

Regards

 

[C.Hoback]

Thanks for all the input! Just to give a back story on why this question came up...we had a support attachment weld that failed at a 6” elbow (fatigue crack). The elbow was equipped with flanges and operates in hydrogen service. This repair would require bake out and post weld heat treat. Due to the configuration, the old circ welds would see heat during PWHT and the line is approximately 30 years old. Since time was not on our side we decided to just fabricate a new flanged elbow to eliminate the risk of opening up old defects. I think this saved us time in the long run. Especially if unplanned defects were found.

Thanks again!

 

[r6155]

C.Hoback
Very well !

Regards