Pipe Support Spacing: Maximum Span Tables
Pipe support spacing defines the maximum distance between two consecutive pipe supports. Correct spacing prevents excessive deflection, overstress, and sagging in horizontal piping runs. The maximum allowable span depends on pipe size, material, wall thickness, insulation weight, fluid density, and operating temperature.
The primary references for pipe support spacing are MSS SP-69 (Pipe Hangers and Supports - Selection and Application), ASME B31.3 (Process Piping), and ASME B31.1 (Power Piping). Project-specific stress analysis may override tabulated values.
How to Determine Support Spacing
- Identify pipe parameters: Nominal size, schedule, material, and operating temperature.
- Calculate line weight: Sum of pipe weight, fluid weight, and insulation weight per unit length (kg/m or lb/ft).
- Select span from tables: Use MSS SP-69 suggested spans as a starting point.
- Check deflection: Maximum midspan deflection is typically limited to 2.5 mm (0.1 in.) for process piping.
- Check bending stress: Ensure bending stress from span loading does not exceed allowable stress per ASME B31.3.
- Adjust for vertical runs: Vertical pipe supports (riser clamps) follow different spacing rules based on buckling rather than deflection.
Maximum Span Table: Carbon Steel Pipe (Water-Filled, Uninsulated)
| Nominal Pipe Size | Std. Wall (Sch 40) Span | Heavier Wall (Sch 80) Span |
|---|---|---|
| 1 in. (DN 25) | 2.1 m (7 ft) | 2.4 m (8 ft) |
| 2 in. (DN 50) | 3.0 m (10 ft) | 3.4 m (11 ft) |
| 3 in. (DN 80) | 3.7 m (12 ft) | 3.7 m (12 ft) |
| 4 in. (DN 100) | 4.3 m (14 ft) | 4.3 m (14 ft) |
| 6 in. (DN 150) | 5.2 m (17 ft) | 5.2 m (17 ft) |
| 8 in. (DN 200) | 5.8 m (19 ft) | 5.8 m (19 ft) |
| 10 in. (DN 250) | 6.4 m (21 ft) | 6.4 m (21 ft) |
| 12 in. (DN 300) | 7.0 m (23 ft) | 7.0 m (23 ft) |
| 16 in. (DN 400) | 7.9 m (26 ft) | 7.9 m (26 ft) |
| 20 in. (DN 500) | 8.8 m (29 ft) | 8.8 m (29 ft) |
| 24 in. (DN 600) | 9.4 m (31 ft) | 9.4 m (31 ft) |
Key Factors Affecting Span
- Insulation thickness: Heavy insulation (e.g., 100 mm calcium silicate) adds significant weight and reduces the allowable span by 10-20%.
- Elevated temperature: At temperatures above 400 deg C, material creep becomes a factor. Reduce spans per engineering judgment or use creep-adjusted allowable stresses.
- Concentrated loads: Valves, in-line instruments, and flanged joints act as concentrated loads. Place supports within 600 mm (2 ft) of heavy valves.
- Vibration service: Piping subject to vibration (e.g., near reciprocating compressors) requires shorter spans and additional restraints.
Span Formula (Simplified)
For a simply supported beam with uniform load:
L = sqrt(8 * S * Z / w)
Where:
- L = maximum span (mm or in.)
- S = allowable bending stress (typically 15.8 MPa / 2,300 psi for support spacing calculations)
- Z = section modulus of pipe (mm3 or in.3)
- w = total unit weight of line (N/mm or lb/in.)
For deflection-limited spans: L = (384 * E * I * delta / 5w)^(1/4), where delta is the allowable midspan deflection (typically 2.5 mm).
Support spacing is verified as part of piping stress analysis and inspection during the detailed engineering phase.
Leave a Comment
Have a question or feedback? Send us a message.