Free post-weld heat treatment (PWHT) requirement lookup per ASME Section VIII Division 1, UCS-56 — minimum holding temperature, minimum holding time, and the general mandatory-PWHT thickness threshold for carbon and low alloy steels. Jump to how it works ↓
Post-weld heat treatment (PWHT) requirements for carbon and low alloy steel pressure vessels are defined in ASME Section VIII Division 1, paragraph UCS-56, across Tables UCS-56-1 through UCS-56-11 — one table per P-Number material grouping. Each table specifies the minimum holding temperature, the minimum holding time as a function of nominal thickness, and the thickness above which PWHT becomes mandatory by default. Select your material's P-Number and enter the nominal thickness (including corrosion allowance, per UW-40(f)) to get the applicable values instantly.
This calculator reports each Table's general default rule — the thickness threshold above which PWHT is mandatory absent any of the specific exemptions the Table's General Notes allow. Actual applicability also depends on Group Number, carbon content, whether preheat was applied, and whether PWHT is a separate service requirement under UW-2 — none of which this calculator collects as input. The full exemption conditions are listed in the results for your selected P-Number; always verify the applicable exemption against the governing Code edition and your specific joint design before omitting PWHT.