ASME B31.3, process piping, pipe wall thickness, Lorenz equation, allowable stress

Description
Built on the ASME B31.3 Lorenz thick-wall equation (t = PD / (2(SEW+PY))), designed specifically for process piping wall-thickness verification. Three KPI cards up top — wall-thickness Pass/Fail, governing max support span, and external collapse pressure rating — give you the verdict before you dig into the calculation trail underneath.

The recurring headache with B31.3 is always the allowable stress: it's temperature- and material-specific, buried in a copyrighted Appendix A table that no calculator is legally allowed to just reprint. This tool solves that honestly instead of ignoring it. It auto-calculates a Basic Allowable Stress from your pipe grade's public SMYS and tensile-strength data, applying the exact general rule B31.3 itself states in para 302.3.2 — the lesser of one-third the tensile strength or two-thirds the yield strength. That gives you a solid, defensible ambient/moderate-temperature number with zero manual lookup, plus a manual override cell the moment you're working in the creep range or need an exact Appendix A value for elevated-temperature service.

The Y coefficient (thick-wall correction) and weld strength reduction factor W are both selectable from dropdowns covering the common ferritic/austenitic steel and temperature categories in Table 304.1.1, with manual override available for anything outside the standard list.

Every formula is shown as clean, readable, native Excel text — zero pasted screenshots, zero hidden hardcoded numbers. Built for process engineers who need a fast, transparent second check on wall thickness during FEED or detailed design, not a replacement for final sign-off by a certified/PE engineer against your own current copy of the code.