Pipeline Axial Load

Calculate pipeline restrained and unrestrained external or global axial load and wall load from temperature and pressure for multi layer pipelines.

The internal pressure is assumed to be zero during installation. The external pressure is assumed to be constant during installation and operation (submerged pipeline).

The first inside layer is the pipe wall. Select the pipe wall thickness and diameter from the pipe schedule. Enter all inside layers. The Young's modulus should be set to zero for inside layers which do not contribute to the axial load. Change the number of layers on the setup page. The axial load is calculated using the thick wall formula (API RP 1111 and DNVGL ST F101). Loads are positive in tension, and negative in compression.

Nominal pipe diameter and wall thickness should normally be used for axial load calculations. Pipe wall stress is calculated for the line pipe layer.

Tool Input

• pletype : External Pressure Type
  • Peu : User Defined External Pressure
• syutype : Stress Table Type
• mattype : Yield Stress Type
  • SMYSu : User Defined Specified Minimum Yield Stress
• schdtype : Line Pipe Schedule Type
• diamtype : Line Pipe Diameter Type
  • ODu : User Defined Outside Diameter
  • IDu : User Defined Inside Diameter
• wtntype : Line Pipe Wall Thickness Type
  • tnu : User Defined Wall Thickness
• sectype : Pipe Section Properties Type
  • EAu : User Defined Pipe E x A
  • EAαu : User Defined Pipe E x A x alpha
  • νu : User Defined Pipe Poisson's Ratio
• loadtype : Axial Load Type
  • Fgu : User Defined Global Axial Load
  • Fwu : User Defined Pipe Wall Axial Load
• WTi : Pipe Liner Wall Thickness
• Ei : Pipe And Liner Elastic Modulus
• αi : Pipe And Liner Thermal Expansion Coefficient
• νi : Pipe And Liner Poisson's Ratio
• Fd : Design Factor
• Pi : Internal Pressure
• Td : Design Temperature
• Tin : Installation Temperature
• Fin : Installation Load

Tool Output

• εw : Pipe Wall Axial Strain
• ν : Pipe Poisson's Ratio
• EA : E x A
• EAα : Pipe E x A x alpha
• Fg : Global Or External Axial Load
• Fw : Pipe Wall Axial Load
• IID : Pipe Inside Diameter Including Liner
• OD : Pipe Outside Diameter
• OD/tn : Pipe Diameter Over Wall Thickness Ratio
• Pe : External Pressure
• SMYS : Specified Minimum Yield Stress
• Sd : Allowable Stress
• Sw : Pipe Wall Axial Stress
• Sw/Sd : Axial Stress Over Allowable Stress Ratio
• tn : Line Pipe Thickness

Calculate offshore pipeline local stationary internal pressure and external pressure from elevation using Bernoulli's equation.

The local internal pressure is calculated from the reference pressure and relative elevation. The external pressure is calculated from the water depth. The internal fluid density is assumed constant.

Tool Input

• pletype : External Pressure Type
  • Pleu : User Defined Local External Pressure
• plitype : Internal Pressure Type
  • Priu : User Defined Reference Internal Pressure
  • Pliu : User Defined Local Internal Pressure
• ρf : Internal Fluid Density
• ρe : External Fluid Density
• Zr : Reference Elevation Relative To Datum
• Zl : Local Elevation Relative To Datum
• Zs : Surface Elevation Relative To Datum

Tool Output

• ΔPl : Pressure Difference Across Pipe Wall
• Δz : Local Elevation Relative To Reference Elevation
• Ple : External Pressure
• Pli : Internal Pressure At Local Elevation
• Pri : Internal Pressure At Reference Elevation
• wd : Water Depth

Calculate pipeline SMYS, SMTS and allowable stress SE and SEF from pipe stress tables.

The allowable stress is calculated by multiplying the SMYS times the quality factor E and the design factor F. The quality factor is used to account for casting quality, or longitudinal weld joint quality. The design factor is used to account for design risks (for pipelines requiring a high level of safety use a low design factor). Temperature derating is not included.

Select one of the API, ASME or DNV stress table options. The API stress values are taken from API 5L tables 6 and 7 (note the API 5L X series is superseded). The ASME stress values are taken from ASME B31.3 process piping table A-1M. The DNV stress values are taken from DNVGL ST F101 submarine pipelines, tables 7-5 and 7-11.

Use the Result Table option to display the stress values for the selected stress table (click the Result Table button, and then click the make table button).

Tool Input

• syutype : Stress Table Type
• mattype : Material Type
  • SMYSu : User Defined Specified Minimum Yield Stress
  • SMTSu : User Defined Specified Minimum Tensile Stress
• efactype : Quality Factor Type
  • Eu : User Defined Quality Factor
• ffactype : Design Factor Type
  • Fu : User Defined Design Factor

Tool Output

• E : Quality Factor Or Joint Factor
• EF : Design Factor (E x F)
• F : Stress Factor
• SEF : Allowable Stress
• SMTS : Specified Minimum Tensile Stress
• SMYS : Specified Minimum Yield Stress

Calculate typical line pipe elastic modulus, shear modulus, bulk modulus, density, and thermal expansion coefficient.

The table values of Poisson ratio and bulk modulus are calculated from the elastic modulus and shear modulus. Project specific data should be used if it is available. Use the Result Table option to display a table of properties versus material type.

Tool Input

• modptype : Material Type
  • Eu : User Defined Elastic Modulus
  • Gu : User Defined Shear Modulus
  • Ku : User Defined Bulk Modulus
  • νu : User Defined Poisson Ratio
  • ρu : User Defined Density
  • αu : User Defined Thermal Expansion Coefficient

Tool Output

• α : Thermal Expansion Coefficient
• ν : Poisson Ratio
• ρ : Density
• E : Elastic Modulus
• G : Shear Modulus
• K : Bulk Modulus