The ferrite determination shall be performed prior to PWHT (if applicable) using either a suitably calibrated magnetic instrument in accordance with AWS A4.2 or by chemical analysis of the weld metal using the WRC-1992 diagram. Each pressure-retaining weld shall be subject to one check per weld for mechanized/automatic welding processes, and a minimum of one check per 18in (450mm) of weld for manual or semiautomatic welding processes.