While the Code only references SNT-TC-1A "may be used as a guide" under 342.1, Note 1, the Inspector has ultimate responsibility for accepting the certifications mandated to be provided by the Employer.
What weldstan said. What you are typically looking for is a Level II or III certification from that NDT lab. [VERY unusual to see a L/III out in the field. L/III's certify L/I's and L/II's]
If you are the Inspector, watch out for poor quality film - can't see the required IQI Image Quality Indicator; watch out for 'over-calls' on porosity. At 1/4" wall thickness, B31.3 allows 1.5 x as much porosity as on the Sect VIII porosity chart. Waaay too common for the L/II to reject a perfectly acceptable weld, because he/she saw "a lot of porosity". Use the charts - it is simple.
hdpinsp,
On a number of occasions while working for Engineering/Construction Management companies, I was appointed the Inspector by the Owner and had final authority regarding film interpretation (in some cases the only reviewer) and I did not have Level II or III certification in RT at the time.
As a contractor installing B31.3 pipe systems, we require RT to be performed by Level II or Level III certified examiners.
