The Weld Certificate That Didn't Tell the Whole Story A fabricated pressure vessel passed visual inspection, radiographic testing, and dimensional checks. The mill certificates for the base material were clean. The welder had a current qualification card. Everything looked in order, right up until the shell cracked during hydrostatic testing. The investigation traced it back to the weld procedure. The Charpy 'V' notch impact test had been performed at ambient temperature, not