Welder5354,
It is actually quite involved.
No impacts - one qualified thickness range
Impacts to ASME IX - a different qualified thickness range
Impacts to B31.3 - a totally different set of thickness ranges.
A good explanation to my similar question was given by jon20013, 803056 and js55 (I think) in a previous post.
Use the search engine above and type Impact Test in Subject and Shane Feder in the Poster.
Regards,
Shane