Requirements to Move Unpressured Pipe – Gas

Introduction

This application is related to maximum movement (deflection) at the end of pipe with no pressure. The greater the deflection requires a larger distance of exposed pipe to minimize the strain on the pipe.

S_{max}=\frac{(\%SMYS)}{100}(SMYS)\,[psia]

S_{max}=\frac{(\%SMYS)}{100}(SMYS)\,[psia]

Where:
𝑆_𝑚𝑎𝑥 − Maximum Stress Allowed
𝑆𝑀𝑌𝑆 − Specific Minimum Yield Strength

S_M=(\frac{\pi}{32})\frac{((D^4)-(D-2t)^4)}{D}\,[psia]

S_M=(\frac{\pi}{32})\frac{((D^4)-(D-2t)^4)}{D}\,[psia]

𝑆_𝑀 − Section Modulus
𝐷 − Nominal Outside Diameter (in)
𝑡 − Nominal Wall Thickness (in)

I=(\frac{\pi}{32})((D^4)-(D-2t)^4)

I=(\frac{\pi}{32})((D^4)-(D-2t)^4)

𝐼 − Moment of Inertial
𝐷 − Nominal Outside Diameter (in)
𝑡 − Nominal Wall Thickness (in)

L_{en}=\frac{3L_dYI}{S_{max}S_M}

L_{en}=\frac{3L_dYI}{S_{max}S_M}

𝐿_𝑑 − Maximum Deflection at Pipe End(in)
𝑌 − Young′s Modulus of Elasticity (psia)

L_p=\frac{L_{en}}{12}

L_p=\frac{L_{en}}{12}

𝐿_𝑝 − Total Exposed Pipe Requirement (ft)

L_{max}=\frac{S_{max}S_M}{L_{en}}

L_{max}=\frac{S_{max}S_M}{L_{en}}

𝐿_𝑚𝑎𝑥 − Maximum Load at the Pipe End (lbs)

M=L_{max}(L_p)\,[lb/ft]

M=L_{max}(L_p)\,[lb/ft]

Case Guide

Part 1: Create Case

Input Parameters

• Nominal Pipe Size (in): 0.625” – 48”)
• Wall Thickness (in): (0.068”- >2”)
• Pipe grade: (24000psi-80000psi) (if unknown use Grade A 24000)
• Maximum Deflection at the Pipe End (in)
• Percentage SMYS (%)

Part 2: Outputs/Reports

Results

• Maximum Stress Allowed (psi)
• Total Exposed Pipe Required (ft)
• Maximum Load at the Pipe Ends (lb)
• Section Modulus
• Moment of Inertia
• Moment (lbf-ft)

References

• ASME B31.8 – Gas Transmission and Distribution Piping Systems
• API 5L, API 5LS and API 5LX – Specification of Pipe Grade
• ASTM – Various – Weld Joint Factor
• CFR Code Part 192
• USDA-SCS Modified (Permissible Velocity of Water and Soil Erodibility)
• FHWA-HEC
• Pipeline Rules of Thumb Handbook
• Timoshenko, S – Theory of Elasticity Anchor Force

FAQ