welding defect acceptance criteria

[abangbikerz]

first of all i would like to say i still have a very little knowledge about asme codes. does any of the asme book contain an acceptance criteria for welding defects especially the one detected using ultrasonic or xray. does the ndt man has the full right to accept or reject certain defects based on his own decision. in my workplace all of the UT personnel reject or accept any defect based on their own feeling. if there is an acceptance criteria in the code book. any decision must be made based on these codes. ndt man just locate and find defects. am i right??

 

[weldtek]

Yes the ASME B & PV Codes ( Sec VIII) provide accept/reject criteria. For Div 1 see UW 51 for Full RT, UW 52 for Spot RT, App 4 for rounded indications, App 12 for UT. Btw, see App 6 for MT and App 8 for PT. If by chance you're doing Div 2 work the accept / reject criteria is in Sec 7 of that Code book.

 

[gtaw]

Every construction/fabrication code or standard I have worked with provides acceptance criteria for the NDT methods specified. The acceptance criteria may be provided by the fabrication document by referencing a different standard, but never the less, it is provided.

In my humble opinion it should never be the inspector that makes the decision regarding establishing an acceptance criteria. Establishing acceptance criteria, i.e., establishing the size, length, nature, etc. of the discontinuity that is acceptable or rejected, is the engineer's responsibility. Generally the engineer is more knowledgeable about the magnitude of the stresses, the nature of the stresses, the influence of the discontinuity, mechanical properties of the materials of construction, operating environment, etc.than the inspector. Rarely does the inspector have that information, nor do most inspectors have the education or experience to use the information if it were provided.

There are those occasions where the item being tested does not fall under the auspices of an existing standard. In those cases the inspector may be requested to provide the engineer with some input, but the responsibility for establishing the acceptance criteria used for the inspection should remain with the engineer.

An inspector that makes up the acceptance criteria “on the fly” is someone that should viewed with suspicion and caution.


Best regards - Al

 

[metengr]

does the ndt man has the full right to accept or reject certain defects based on his own decision. in my workplace all of the UT personnel reject or accept any defect based on their own feeling

No. NDT personnel are not qualified to establish acceptance criteria.

 

[abangbikerz]

thanks for the info. i will dig further. its just happen to be that im confronting a UT man about making a decision.