ASME B31.8 Pipeline Span Design for Unrestrained Piping
Beam theory, pipe section properties, and ASME B31.8 span design criteria
| Simply Supported: | δ = 5wL⁴/(384EI) |
| Fixed-Fixed: | δ = wL⁴/(384EI) |
| Fixed-Pinned: | δ = wL⁴/(185EI) |
| Cantilever: | δ = wL⁴/(8EI) |
This calculator evaluates bending stress and deflection for above-ground (unrestrained) pipeline spans per ASME B31.8 §833.6. Combined longitudinal stress from pressure and bending must not exceed 0.75 × SMYS × T.
The industry-standard deflection limit for pipeline spans is L/240, where L is the span length. The calculator checks this criterion along with the ASME B31.8 combined stress limit.
Fixed-Fixed supports provide the lowest stress and deflection but require moment-resisting connections. Pinned-Pinned is more conservative and easier to detail. The calculator supports Fixed, Pinned, and Free end conditions.
The calculator considers pipe self-weight, additional uniform loads (insulation, ice), point loads, and internal pressure. Longitudinal pressure stress is combined with bending stress per ASME B31.8 §833.6.