KEVOS® MAKEOS · Strength
Pipe Support Span Check (Pipe and Contents Weight, Bending Stress, Sag, Longest Span)
How far apart can the supports for this pipe be, given its weight full of liquid, the bending stress and the sag I can accept?
Check of the span between pipe supports: the section area, second moment of area and section modulus of the pipe, the weight per metre of pipe, contents and insulation, then the bending moment, stress and sag for simply supported, fixed or one-end-fixed spans under the uniform load (closed forms, the fixed cases as the beam cases tool), and the longest span that keeps both stress and sag within your limits.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Pipe outside diameter | mm | Outside diameter of the pipe. |
| Wall thickness | mm | Wall thickness (less corrosion allowance for a design check). |
| Pipe density | kg/m³ | Density of the pipe material. |
| Contents density | kg/m³ | Density of the contents (0 for empty gas lines; 1000 for water). |
| Insulation and cladding | kg/m | Mass per metre of insulation, cladding and trace heating. |
| Modulus of elasticity | GPa | Modulus of elasticity of the pipe. |
| Span | ||
| Span treated as | choice | How the span is restrained by the supports and neighbouring spans. |
| Support spacing | mm | Distance between supports. |
| Allowable bending stress | MPa | Allowable bending stress for sustained loads (often well below the material allowable, to leave room for pressure stress). |
| Largest sag | mm | Largest sag at mid-span you accept (small values avoid pockets that do not drain). |
Method and formulas
- A = π (D² − d²) ÷ 4; I = π (D⁴ − d⁴) ÷ 64; Z = 2I ÷ D; weight w = g (A ρ_pipe + π d² ρ_fluid ÷ 4 + insulation).
- Simply supported: M = wL² ÷ 8, sag = 5wL⁴ ÷ 384EI; fixed both ends and fixed–supported as the beam cases tool for a uniform load.
- Stress grows with L² and sag with L⁴, so the longest spans are L √(σ_allow ÷ σ) and L (δ_allow ÷ δ)^¼.
- Example: 7.6006 kg/m gives 9.1387 MPa and 1.4208 mm sag; the span may be up to 3,455.2 mm.
Limitations
- Straight horizontal span with uniform load; valves, flanges and branches add point loads.
- Sustained weight only; pressure, thermal and seismic stresses are separate.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Space hangers for a water or process line
- Check an existing pipe rack span
- See how insulation or a heavier fluid shortens the span
Who it is for
- Piping designers
- Plant engineers
- Mechanical contractors
What you get
- Pipe section and weight per metre
- Moment, stress and sag
- Longest span for stress and sag
Interpreting the result
- For small pipes the sag limit usually governs; for large pipes the stress does.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 234–246, 257–277. Topic reference; no source tables or recommended settings are reproduced.
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