Radiography (RT) Before or after PWHT

[GemmellG]

My question is should code required RT be conducted before or after PWHT. My opinion is after as the weld is not complete until all of the essential variables of the WPS has been met which includes PWHT.

 

[david339933]

Try a search on the site...this has been discussed many times.

 

[GemmellG]

David thanks found what I was looking for. Will do search in the future.

 

It is not prescribed by the WPS, but by definition the WPS must align with the final condition of the equipment.
All the rules are found in the construction code.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Ron]

NDT should be done after completion of the welding and PWHT....cracking can occur during and after PWHT and should be checked.


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[weldstan]

Many ASME Codes permit final NDE before PWHT for equipment made of Carbon Steel but require final NDT after PWHT for low alloy steels.

 

[SnTMan]

Some shops prefer to do both before and after PWHT. Prevents from PWHT'ing flawed welds, then examines again after for flaws due to PWHT.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[kingnero]

I'm no expert in RT, but is it sensitive enough to detect reheat cracking (or other microcracking) ?

 

I'm no expert in RT, but is it sensitive enough to detect reheat cracking (or other microcracking) ?

RT is not good at detecting fine cracks. Furthermore, reheat cracks are frequently quite short.
Why do you suspect reheat cracking? It is typically associated with creep-resistant steels, but can happen in carbon steel.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[kingnero]

I don't suspect reheat cracking, I just find it very peculiar that RT is chosen as NDT when PWHT needs to be done.
I'd have all testing done as required by the standard(s) before PWHT, and additional testing depending on the type of defects you'd suspect after PWHT (e.g. UT for most applications, macrography for microcracks).

 

[TED7]

ISO 17635:2016 states the following "The testing should be carried out after completion of all required heat treatments."

In practice, and to ensure that PWHT time isn't wasted on a flawed weld, sample NDE can be done on sections of the weld in advance of PWHT - It depends how long your PWHT takes / costs compared to the time / cost of UT/RT

 

[weldstan]

One reason for requiring RT as the final volumetric examination is that the record (radiograph) could be reviewed by others (AI, Purchaser, etc.) at a later date and the old UT methods could not, relying on the expertise of the Level II Examiner. With modern UT methods the same cannot be said and more UT is being performed. The problem with the new methods is the ability of the AI or Purchaser's inspector to properly review the electronically stored data.

I did have one case where the data was corrupted and we had the weld seams involved re-examined. We also employed a third party, trusted Level III review the data as well as the original test calibrations, test setup, etc.