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ASME B31.8 Gas Pipeline Wall Thickness

Calculate ASME B31.8 gas pipeline wall thickness from hoop stress for onshore and offshore pipelines.

Select the appropriate line pipe schedule (ASME or ISO etc), and stress table (API, ASME or DNV), or use the user defined options. Pipe pressure can either be calculated from elevation, or user defined. For metal pipeline the pressure design thickness equals the nominal wall thickness minus the corrosion allowance. Fabrication tolerance is ignored. The wall thickness should be checked for all pipeline elevations. A wall thickness should be specified which is greater than or equal to the maximum calculated wall thickness (usually by selecting the next highest schedule thickness). Use the Result Plot option to plot the calculated wall thickness versus elevation, and the hoop stress versus elevation for the specified wall thickness.

Reference : ANSI/ASME B31.8 : Gas Transmission And Distribution Piping Systems (2018)

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CALCULATOR : ASME B31.8 Section 841.1 Pipeline Wall Thickness From Hoop Stress (Onshore) [FREE]   ±

Calculate steel pipe wall thickness from hoop stress for onshore pipelines (ASME B31.8 section 841.1). Wall thickness may be calculated for either user defined outside diameter (constant OD pipe), or user defined inside diameter (constant ID pipe).

Design factors are taken from table 841.1.6-2 (stress design factor), table 841.1.7-1 (longitudinal joint factor), and 841.1.8-1 (temperature derating factor. The corrosion allowance should include all allowances (erosion, corrosion, and mechanical).

The wall thickness should be calculated for the maximum pressure which may occur at any point on the pipeline, accounting for elevation and variations in fluid density. The maximum pressure usually occurs at the lowest point on the pipeline or pipeline section.

Tool Input

  • plitype : Internal Pressure Type
    • Priu : User Defined Reference Internal Pressure
    • Pliu : User Defined Local Internal Pressure
    • ρf : Internal Fluid Density
    • Zr : Reference Elevation
    • Zl : Local Elevation
  • syutype : Line Pipe Stress Type
  • mattype : Material Type
    • SMYSu : User Defined Specified Minimum Yield Stress
  • efactype : Weld Joint Quality Factor Type
    • Eu : User Defined Quality Factor
  • tfactype : Temperature Derating Factor Type
    • Td : Design Temperature
    • Tu : User Defined Temperature Derating Factor
  • loctype : Location Class
    • Fu : User Defined Design Stress Factor
  • pipetype : Pipe Section Type
  • satype : Allowable Stress Type
    • Sau : User Defined Allowable Stress
  • schdtype : Line Pipe Schedule Type
  • diamtype : Pipe Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
  • calctype : Wall Thickness Equation Type
  • walltype : Wall Thickness Calculation Type
  • ta : Corrosion Allowance

Tool Output

  • D : Pipe Outside Diameter
  • D/tn : Pipe Diameter Over Wall Thickness Ratio
  • E : Weld Joint Factor
  • F : Design Stress Factor
  • PR : Rated Pressure
  • Pli : Internal Fluid Pressure
  • SEFT : Allowable Stress
  • SMYS : Yield Stress
  • Sh : Pipe Hoop Stress
  • Sh/Sa : Hoop Stress Over Allowable Stress Ratio
  • T : Temperature Reduction Factor
  • d : Pipe Inside Diameter
  • t : Pipe Pressure Containment Wall Thickness
  • tn : Pipe Nominal Wall Thickness

CALCULATOR : ASME B31.8 Section A842.2 Pipeline Wall Thickness From Hoop Stress (Offshore) [FREE]   ±

Calculate steel pipe wall thickness from hoop stress for offshore pipelines and platform piping (ASME B31.8 section A842.2). Wall thickness may be calculated for either user defined outside diameter (constant OD pipe), or user defined inside diameter (constant ID pipe).

The design factors are taken from table A842.2.2-1 (design stress factors), and table 841.1.8-1 (temperature derating factor). The corrosion allowance should include all allowances (erosion, corrosion, and mechanical).

For subsea pipeline sections The internal and external pressure should be calculated from the design pressure and the elevation so that the local delta static pressure across the pipe wall is a maximum. For platform risers the maximum local delta pressure generally occurs at LAT (Lowest Astronomical Tide including surge) in the splash zone. For subsea pipeline sections the maximum local delta pressure generally occurs at the highest elevation in that section.

Tool Input

  • plitype : Internal Pressure Type
    • Priu : User Defined Reference Internal Pressure
    • Pliu : User Defined Local Internal Pressure
    • ρf : Internal Fluid Density
    • Zr : Reference Elevation
    • Zl : Local Elevation
  • pletype : External Pressure Type
    • Pleu : User Defined Local External Pressure
    • ρe : External Fluid Density
    • Zs : Surface Elevation
  • syutype : Line Pipe Stress Type
  • mattype : Material Type
    • SMYSu : User Defined Specified Minimum Yield Stress
  • tfactype : Temperature Derating Factor Type
    • Td : Design Temperature
    • Tu : User Defined Temperature Derating Factor
  • loctype : Location Class
    • Fu : User Defined Design Stress Factor
  • satype : Allowable Stress Type
    • Sau : User Defined Allowable Stress
  • schdtype : Line Pipe Schedule Type
  • diamtype : Pipe Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
  • calctype : Wall Thickness Equation Type
  • walltype : Wall Thickness Calculation Type
  • ta : Corrosion Allowance

Tool Output

  • ΔPl : Delta Pressure Across Pipe Wall
  • D : Pipe Outside Diameter
  • D/tn : Pipe Diameter Over Wall Thickness Ratio
  • F : Design Stress Factor
  • PR : Rated Pressure
  • Ple : External Fluid Pressure
  • Pli : Internal Fluid Pressure
  • SFT : Allowable Stress
  • SMYS : Yield Stress
  • Sh : Pipe Hoop Stress
  • Sh/Sa : Hoop Stress Over Allowable Stress Ratio
  • T : Temperature Reduction Factor
  • d : Pipe Inside Diameter
  • t : Pipe Pressure Containment Wall Thickness
  • tn : Pipe Nominal Wall Thickness

CALCULATOR : ASME B31.8 Section 842.2 Plastic Pipe Wall Thickness And Operating Pressure From Hoop Stress [FREE]   ±

Calculate plastic pipe wall thickness and design pressure from hoop stress (ASME B31.8 section 842.2). Pipe parameters may be defined from either the wall thickness, the diameter ratio, or the design pressure.

Tool Input

  • satype : Hydrostatic Design Stress Type
    • HDB : User Defined Hydrostatic Design Stress
    • Dfu : User Defined Design Stress Factor
    • Sau : User Defined Allowable Stress
  • schdtype : Pipe Schedule Type
  • diamtype : Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
    • DRu : User Defined Dimension Ratio SDR OR SIDR
  • walltype : Wall Thickness Calculation Type
  • c : Mechanical Allowance
  • P : Design Pressure

Tool Output

  • CVG : Convergence Factor
  • D : Pipe Outside Diameter
  • DR : Dimension Ratio (SDR or SIDR)
  • PR : Rated Pressure
  • S : Hydrostatic Design Stress
  • Sh : Hoop Stress (≤ S)
  • Sh/Sd : Hoop Stress Over Design Stress Ratio (≤ 1)
  • d : Pipe Inside Diameter
  • t : Pressure Design Wall Thickness
  • tn : Nominal Wall Thickness

CALCULATOR : ASME B31.8 Metal Pipe Diameter And Wall Thickness Schedule [FREE]   ±

Calculate ASME B31.8 metal pipe diameter and pressure design wall thickness from pipe schedule or user defined diameter and wall thickness (ASME B31.8 section 841.1). For ASME B31.8 the fabrication tolerance is accounted for in the design factor. The fabrication tolerance is ignored when calculating the pressure design thickness. The pressure design thickness equals the nominal thickness minus the corrosion allowance.

Select the pipe schedule (NPS or ISO), pipe diameter and wall thickness, or use the user defined option. Use the Result Table option to display the pipe schedule with nominal wall thickness and pressure design wall thickness for the selected diameter. Fabrication tolerance is ignored.

Tool Input

  • schdtype : Line Pipe Schedule Type
  • diamtype : Line Pipe Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
  • c : Wall Thickness Corrosion Allowance

Tool Output

  • ID : Nominal Inside Diameter
  • OD : Nominal Outside Diameter
  • OD/tn : Diameter Over Wall Thickness Ratio
  • tn : Nominal Wall Thickness
  • tp : Pressure Design Wall Thickness

CALCULATOR : ASME B31.8 Plastic Pipe Diameter And Wall Thickness Schedule [FREE]   ±

Calculate ASME B31.8 plastic pipe diameter and pressure design wall thickness from pipe schedule or user defined diameter and wall thickness (ASME B31.8 section 842.2).

Select the pipe schedule (NPS or ISO), pipe diameter and wall thickness, or use the user defined option. Use the Result Table option to display the results for the selected diameter. Fabrication tolerance is included.

Tool Input

  • schdtype : Schedule Type
  • diamtype : Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
    • DRu : User Defined Dimension Ratio SDR OR SIDR
  • ttoltype : Wall Thickness Fabrication Tolerance Type
    • xfu : User Defined Negative Wall Thickness Fraction
    • tfu : User Defined Negative Wall Thickness Allowance
  • c : Wall Thickness Mechanical Allowance

Tool Output

  • CVG : Convergence Factor
  • DR : Pipe Dimension Ratio (SDR Or SIDR)
  • ID : Nominal Inside Diameter
  • OD : Nominal Outside Diameter
  • tf : Wall Thickness Fabrication Allowance
  • tm : Minimum Wall Thickness
  • tn : Nominal Wall Thickness
  • tp : Pressure Design Wall Thickness

CALCULATOR : ASME B31.8 Pipeline Wall Thickness From Hoop Stress (General) [FREE]   ±

Calculate ASME B31.8 general pipe wall thickness from diameter and design stress.

For ASME B31.8 pipe use either the Barlows equation outside diameter option, or the Barlows equation midwall diameter option. Wall thickness tolerance is not required (use the zero wall thickness tolerance option). The corrosion allowance should include mechanical allowance (eg threads), erosion allowance and any other allowances. External pressure should be ignored for onshore pipelines (use the no external pressure option).

Tool Input

  • pletype : External Pressure Type
    • Peu : User Defined External Pressure
  • schdtype : Pipe Schedule Type
  • diamtype : Pipe Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tnu : User Defined Wall Thickness
  • ttoltype : Wall Thickness Tolerance Type
    • xfu : User Defined Negative Wall Thickness Fraction
    • tfu : User Defined Negative Wall Thickness Allowance
  • syutype : Stress Table Type
  • mattype : Yield Stress Type
    • SMYSu : User Defined Specified Minimum Yield Stress
  • sdtype : Design Stress Type (F x SMYS)
    • Fu : User Defined Design Factor
    • Sdu : User Defined Design Stress
  • walltype : Wall Thickness Calculation Type
    • Yu : User Defined ASME Y Factor
  • calctype : Wall Thickness Type
  • tc : Corrosion Allowance
  • Pi : Internal Pressure

Tool Output

  • ID : Pipe Inside Diameter
  • OD : Pipe Outside Diameter
  • OD/tn : Pipe Diameter Over Wall Thickness Ratio
  • PΔ : Pressure Difference
  • Pe : External Pressure
  • SMYS : Specified Minimum Yield Stress
  • Sd : Design Stress
  • Sh : Pipe Hoop Stress
  • Sh/Sd : Hoop Stress Over Design Stress Ratio
  • cvg : Convergence Check
  • tf : Fabrication Allowance
  • tfx : Fabrication Fraction
  • th : Hoop Stress Thickness (Pressure Containment)
  • tm : Minimum Wall Thickness
  • tn : Nominal Wall Thickness

CALCULATOR : ASME B31.8 Section 841.1 Pipeline Temperature Derated Yield Stress And Tensile Stress [FREE]   ±

Calculate temperature derating factor, and derated yield stress and tensile stress from temperature (ASME B31.8 section 841.1).

Refer to Table 841.1.8-1 for the derating factors. The derating factors are valid for steel pipe upto 232 C (450 F). For temperatures above 232 C (450 F) the derating values should be used carefully (material specific test data should be used if it is available). The derating factor is assumed to be valid for yield stress and tensile stress. Use the Result Table option to display the results for the selected stress table (API, ASME or DNV). The temperature derating factor is not valid for nickel alloy, or stainless steel.

Tool Input

  • syutype : Stress Table Type
  • mattype : Material Type
    • SMYSu : User Defined Specified Minimum Yield Stress
    • SMTSu : User Defined Specified Minimum Tensile Stress
  • tfactype : Temperature Derating Factor Type
    • Td : Design Temperature
    • Tu : User Defined Temperature Derating Factor

Tool Output

  • SMTS : Specified Minimum Tensile Stress
  • SMTS/SMYS : Tensile Stress Over Yield Stress Ratio
  • SMYS : Specified Minimum Yield Stress
  • SMYS/SMTS : Yield Stress Over Tensile Stress Ratio
  • Su : Derated Tensile Stress
  • Sy : Derated Yield Stress
  • T : Temperature Derating Factor

CALCULATOR : ASME B31.8 Section 842.2 Plastic Pipe Allowable Stress [FREE]   ±

Calculate allowable stress (SDf) for plastic piping (ASME B31.8 section 142.2).

The allowable stress equals the hydrostatic design basis (HDB) times the design factor (Df). SDf = HDB x Df.

Tool Input

  • satype : Allowable Stress Type
    • HDB : Hydrostatic Design Basis Stress
    • Dfu : User Defined Design Stress Factor
    • Sau : User Defined Allowable Stress

Tool Output

  • Sa : Allowable Stress