Radial clearance between the sleeve bore and the carrier pipe outside diameter (annular gap, each side).
When P ≥ 690 bar, allowable stress S is taken from Table K-1 (B31.3-2024, SI) for the selected material at design temperature Tmax (table in °C, stress in MPa; converted to bar for Eq. (34a): 1 MPa = 10 bar).
When P < 690 bar, allowable stress S is taken from Table A-1 (B31.3-2024, SI) for the selected material at design temperature Tmax (table in °C, stress in MPa; converted to bar for Chapter II: 1 MPa = 10 bar).
Default 0.4 matches ASME B31.3 Table 304.1.1 for ferritic steels at ≤ 482 °C (≤ 900 °F). At higher temperatures, Y increases—edit per your edition.
Defaults per Totalenergies wall-thickness sheet: 12.5% for sleeve D < 457.2 mm (NPS < 18"), 8.0% for D ≥ 457.2 mm. Formula: trequired = tcalculated / (1 − f).
Default 0.80 — typical for sleeve welds without 100% RT (per B31.3 joint efficiency for the assumed category). Use 1.00 only when full NDE (e.g. 100% RT) applies.