Nalla,
Technically VT is an NDT process. Last I knew, nothing was destroyed when VT was done. Now, AWS does not refer to it as VT but Visual Examination as the 'VT' goes with ASNT Visual terminology. But they are all the same thing. In the process of completing our jobs it is seen as a separate process from NDT when that term is used primarily to indicate the application of MT, UT, PT, RT, etc. But it is still 'TECHNICALLY' an NDT process.
Yes, as Henry said, it is to be done prior to the balance of NDT processes. But, there will be some fine lines within individual Job Specifications that may alter the order of inspections as well as who is doing what. In my case, many times we are tasked with doing all 'NDT' as the contractor either does not have the properly qualified personnel and/or there has been arrangements made that it only happens once and that is by the TPI company so that it is done by those the EOR/customer has hired and trusts to do the job. Often, this means it gets done without true VT by either QC or QA prior to the NDT.
The problem with that is that if there are visual discontinuities which are rejectable and the UT has been done but now some welding takes place to correct the other defects then in my opinion the UT must be done again. Who knows what you just put in the finished weld that may make a difference on it's structural integrity.
Are you "violating" the code? Yes...and No. The engineer can change, delete, add to, modify the code in any way he chooses. If he has signed off on this procedure then No...and Yes. Clear as mud right?
In a perfect world VT should ALWAYS take place prior to NDT. In an unperfect world it still should, but doesn't always and doesn't necessarily have to. If the NDT tech is also the CWI, then obviously he can do both at the same time and mark corrections prior to doing the UT, for example, and then come back when corrections are completed. If he isn't dual qualified or maybe just restricted by contract from doing both CWI and NDT then the CWI should go look at what is going on when they call for NDT on a member.
Is there an AWS Official Interpretation? Not that I remember but I will take a look through them, and so should you. They are easily available on the AWS Website and aws.org and then go to the correct NEW button. I'll have to find it. Used to know exactly where it was. I find the new site pretty easy, just have to forget everything I had in my mind from the old one because I keep trying to find things the same way.
He Is In Control, Have a Great Day, Brent