Materials, Welding, and Fabrication Processes
Materials and traceability
Every pressure part must be traceable from the mill certificate to the installed component. Distinguish the MTR (mill test report), the EN 10204 3.1 certificate (test results from the same cast or heat, issued by the manufacturer), and the 3.2 certificate (independent inspection and testing, countersigned by an authorized inspection body). Check specification, grade, heat number, chemistry, tensile results, impact results where required, and heat-treatment condition. Positive material identification confirms alloy identity on stainless and high-alloy parts, but it does not replace the certificate.
Welding
A WPS is the written instruction; the PQR is the record of the test that supports it; neither is a welder qualification. Under ASME Section IX, changing an essential variable requires requalification of the procedure. Welder performance qualification is limited by process, filler (F-number), base metal (P-number), position, thickness, and pipe diameter, and it lapses after a defined period of non-use (six months is the usual continuity rule). Verify consumable control: baking, holding ovens, issued quantity, returned stubs.
Fabrication
Watch forming-strain limits, weld fit-up and reinforcement, nozzle orientation, and the sequence of post-weld heat treatment and repairs. A repair made after PWHT requires re-heat treatment unless the code exempts it.
Traps and rule of thumb
Typical traps: substituting an "equivalent" grade without written concession; accepting a PQR as a welder ticket; missing heat-number reconciliation in the data book. Rule of thumb: a groove-weld coupon 1/2 in. thick qualifies thickness from about 1/16 in. up to 1 in. (2T).