How do you calculate pipe support span?

Pipe support span is determined by the lesser of two criteria: (1) stress-based span where bending stress must not exceed allowable limits (typically 1/3 of yield strength), and (2) deflection-based span where midspan sag must stay within limits (typically 0.1 inch or L/240). The governing span is the smaller of the two, ensuring both structural integrity and acceptable sag.

What is MSS SP-69 and how does it apply to pipe supports?

MSS SP-69 (Manufacturers Standardization Society Standard Practice 69) provides recommended pipe support spacing tables for standard weight and heavier pipes in various service conditions. It gives quick-reference maximum spans for gas, water-filled, and steam service. These values serve as industry guidelines and should be verified against project-specific stress and deflection calculations.

Why is natural frequency important for pipe support design?

Natural frequency must be checked to avoid resonance with equipment vibration sources like compressors and pumps. The recommended minimum natural frequency for pipe spans is 4 Hz. If the natural frequency falls below 4 Hz, the span should be shortened or additional supports added to raise the frequency above potential excitation sources.

What loads must be considered in pipe support span design?

Total distributed load includes: pipe weight (from NPS/schedule tables), fluid contents weight (water, oil, gas, or steam), insulation weight based on thickness and density, cladding/jacketing weight, and any concentrated loads from valves or instruments. Wind loads may also apply for outdoor installations. The total load directly affects both stress-based and deflection-based maximum spans.

Pipe Support Span Calculator | ASME B31.1, B31.3, MSS SP-69

Pipe Properties

Nominal Pipe Size (NPS)

Pipe Schedule

Pipe Material

Service Conditions

Pipe Contents

Fluid Density

lb/ft³

Operating Temperature

°F

Affects elastic modulus and allowable stress at temperature

Insulation & Additional Loads

Insulation Thickness

Insulation Density

lb/ft³

Calcium silicate: 8-14 | Mineral wool: 6-10 | Fiberglass: 3-6

Cladding / Jacketing Weight

lb/ft

Concentrated Loads (valves, instruments)

Support & Design Criteria

Support Type

Allowable Deflection

Industry practice: 0.1" or L/240. Drainage lines may require tighter limits.

Stress Design Factor

Fraction of yield strength for gravity bending. Typical: 0.33 (1/3 SMYS)

Wind Load (outdoor only)

psf

Understanding Pipe Support Spans

Two Governing Criteria
Maximum span is the lesser of: (1) stress-based limit ensuring bending stress stays below allowable, and (2) deflection-based limit preventing excessive sag between supports.

Key Factors:
Pipe size and wall thickness
Fluid density (gas vs. liquid)
Insulation and cladding weight
Support type and end conditions

Industry Practice:
MSS SP-69 provides recommended span tables. ASME B31.1 (power piping) and B31.3 (process piping) define stress limits. Natural frequency should exceed 4 Hz to avoid vibration problems near rotating equipment.

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Understand pipe support design, span tables, support types, thermal movement, and beam theory for piping

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Results

Governing Maximum Span

feet

Span (Stress-Based) -

Span (Deflection-Based) -

Governing Criterion -

Natural Frequency -

Total Distributed Load -

Bending Stress at Span -

Deflection at Span -

Support Reaction Force -

MSS SP-69 Span (reference) -

Formulas

L = min(L_stress, L_deflection)

L_stress = √(8 × S_allow × Z / w)

L_defl = (384 × E × I × δ / (5 × w))^1/4

S_allow = F × SMYS (at temperature)

w = w_pipe + w_contents + w_insulation + w_cladding

f_n = 3.13√(EIg / wL&sup4;) > 4 Hz

Standards & References

ASME B31.1
Power Piping — Allowable stress tables
ASME B31.3
Process Piping — Stress criteria for support design
MSS SP-69
Pipe Hangers & Supports — Recommended span tables
AISC Steel Construction Manual
Beam deflection and structural criteria
ASME B36.10M
Welded and Seamless Wrought Steel Pipe — Dimensional data

Engineering Notes

Stress limit: Typically 1/3 of SMYS for gravity-only bending (design factor 0.33)
Deflection limit: Industry practice 0.1" or L/240 for general service
Hydrotest: Always re-check spans for water-filled weight
Natural frequency: Must exceed 4 Hz near rotating equipment
Continuous spans: Allow approximately 22% longer stress-based and 47% longer deflection-based spans than simple spans
Thermal expansion: Provide at least one sliding support per span for axial movement

Quick Reference — MSS SP-69 Spans

2" STD, Water: 10 ft | Gas: 13 ft
4" STD, Water: 14 ft | Gas: 17 ft
6" STD, Water: 17 ft | Gas: 21 ft
8" STD, Water: 19 ft | Gas: 24 ft
12" STD, Water: 23 ft | Gas: 30 ft
16" STD, Water: 27 ft | Gas: 35 ft
24" STD, Water: 32 ft | Gas: 39 ft

Pipe Support Span Calculator

Pipe Properties

Service Conditions

Insulation & Additional Loads

Support & Design Criteria

Understanding Pipe Support Spans

📚 Learn the Theory

Results

Formulas

Standards & References

Engineering Notes

Quick Reference — MSS SP-69 Spans

Related Calculators

Bending Stress

Thermal Expansion

Pipe Weight

Hoop Stress