PetroStreet

We have a situation at site.

At our waste heat boiler, the weld joints in P-1 material (P.No.3) were required to be radiographed after undertaking PWHT. The weld joint is in 14" dia and 16 mm thickness. What our construction contractor did is they radiographed the weld joints before PWHT in order to just be sure about the joint clear of any repairs.
Now after about 03 months, the licensor imposed that atleast 10% of total weld joints shall be radiographed or ultrasonically tested after PWHT. In order to comply with this requirement, we used TOFD technique and found repairs in two joints out of 12 scanned.
Just to be clear we looked at the radiographs again for those welds and they were found to be OK. We decided to conduct radiography of these two joints again just to confirm whether the same joints were radiographed initially. And now we have found the results which are OK again.
The defects in both the weld joints lie near the root of the weld (sub surface and longitudinal) and they are larger than 100 mm in length. Radiography is not picking up the same.

Now what should be the recommendation, should we go for the results what UT team is providing or to rely on the radiographs? Should those defects be removed or would it be a false call of UT?

Golden Rule: When re-testing AFTER PWHT, ALWAYS use the same method as used BEFORE PWHT, otherwise its highly probable you will land yourself in the situation you are in now.

If this was ASME work was the TOFD carried out strictly in accordance with Section V Article 4 Mandatory Appendix III? If not, throw the results away so as not to get into deeper water. If yes (and I very much doubt it), whose bright idea was it to spend so much money on using a highly sensitive method to re-examine radiograph quality welds?

To sum up, dont mention the TOFD to anyone, lose all records of it, do the 10% RT, present the results to your licenser's representative and finito - job done..

Great solution. I got it.
Actually TOFD was already available at site for inspection of many other weld joints and is being done according to ASME V Article 4.

Thanks Nigel.