Start from the gasket stress you want and work back to bolt stress and torque, the way PCC-1 Appendix O recommends. Pick a B16.5 flange to fill the bolt count and size, then enter the gasket dimensions. Values are for reference; confirm against the current edition of the governing standard. Send us your bolting list for a quote or call (281) 581-0176.
Related: Nut Factor (K) Guide · Flange Tightening Pass Table · Torque Calculator (Beta) · All technical docs
Method (PCC-1 App O-3)
- Gasket area Ag = π/4 (GOD² − GID²), where GOD is the smaller of the sealing element OD and the raised face OD, and GID is the larger of the sealing element ID and the flange seating ID (O-1.3).
- Bolt stress Sb = SgT × Ag / (nb × Ab), with Ab the bolt root area.
- Torque T = K × D × Sb × Ab / 12, with D the nominal bolt diameter in inches (ft-lb), rounded up to the next 5 ft-lb.
- Keep Sb above a minimum (typically 20–35 ksi) and below a maximum (typically 40–70% of bolt yield) (O-4.1).
Why not one stress for every flange?
PCC-1 O-1.1 notes that one bolt stress for all joints (for example 50 ksi) can leave some gaskets under-compressed and can yield stainless bolts or small flanges. Working from the gasket target gives each joint the load it needs.
Limits of this tool
It does not check flange stress or gasket crush limits, which App O-4 adds. Get gasket stress targets from your gasket manufacturer, and nut factor from tests or the Nut Factor (K) Guide.