X-Ray after PWHT

[keens]

Are X-Rays of the Welds required after PWHT? I thought that they are required because you need to check the integrity of the welds and the properties. One of our QC guys do not think this is the case. Thanks...

 

[metengr]

NO NDT method is perfect, and the ANSI Codes and Standards committees recognize this problem, and have for many years. RT, like UT, requires skill in interpretation of film. Do flaws get missed by RT, yes, do flaws get sized improperly or misinterpreted by UT examiners, yes. Like most technical consensus committees it takes a long time to endorse or accept an alternative NDT method or change in requirements until it has been successfully proven by industry in non-Code applications or through rigorous testing demonstrations. As UT methods become more sophisticated, the Codes and Standards committees will come around from Code Cases to Code revisions.

So, let the "smart" buyer beware. Codes and Standards provide MINIMUM guidelines for NDT to assure safe operation. One can always exceed the minimum Code requirements for NDT.

 

[robsalv]

Late addition....

I'm with Metengr. Codes set minimum standards and sometimes reflect the loudest voice on the committee and not necessarily the best practice. In the petrochem plant I work in, we exceed code requirements often - due to the experience of Oil and Gas world wide.

Standards tend to lag well behind new best practices.

In the case of the original posters question, we double up NDE when PWHT is involved. On really critical vessels, we'll pay for both RT and UT of welds. Interestingly, we've not found many reworks - but I think that's more down to the welder knowing he's not going to be able to hide anything and so does a good job. [why they just don't do a good job in the first place is beyond me!]

Cheers

Rob