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Pipeng Free Online Software : ASME B31.8 Wall Thickness Calculators
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Pipeng : ASME B31.8 Gas Pipelines : Pipeline Wall Thickness From Hoop Stress Calculation Module

ASME B31.8 Wall Thickness Calculators

Description : ASME B31.8 gas pipeline wall thickness from allowable hoop stress calculators.

Discussion : Calculate the wall thickness from the allowable hoop stress.

For onshore pipelines the maximum allowable operating pressure (MAOP) is used as the design pressure. The MAOP should account for changes in elevation and hence changes in static pressure along the pipleline route. For offshore pipelines allowance is made for external pressure. The maximum delta pressure across the pipe wall (the maximum difference between internal and external pressure) is used as the design pressure. For offshore platform piping the external pressure is zero and the delta pressure equals the MAOP.

The code allows for a 10% surge over pressure above MAOP. The code also allows for the linepipe manufacturing tolerance within the nominal wall thickness (for linepipe specifications referenced by the code).

References :

Calculator Tools In This Module:

CALC : Flow : Bernoulli 071 : Submerged Pipe Wall Delta Pressure From Relative Elevation : Calculator
CALC : Flow : Bernoulli 072 : Submerged Pipe Wall Delta Pressure From Fluid Height : Calculator
CALC : Pipe : Wall Thickness 012 : ASME B31.4 and ASME B31.8 Pipeline Hoop Stress Based On Nominal Wall Thickness : Calculator
CALC : Pipe : Wall Thickness 013 : ASME B31.4 and ASME B31.8 Pipeline Hoop Stress Based On Hoop Wall Thickness : Calculator
CALC : Pipe : Wall Thickness 021 : ASME B31.8 Pipe Wall Thickness - Onshore Pipeline : Calculator
CALC : Pipe : Wall Thickness 022 : ASME B31.8 Pipe Wall Thickness - Offshore Pipeline And Platform : Calculator
CALC : Pipe : Wall Thickness 023 : ASME B31.8 Pipeline SMYS Temperature Derating Factor : Calculator
CALC : Pipe : Wall Thickness 024 : ASME B31.8 Charpy V-Notch Toughness : Calculator


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Module List

CALC : Flow : Bernoulli 071 : Submerged Pipe Wall Delta Pressure From Relative Elevation : Calculator

Description : Calculate the delta static pressure across the pipe wall of a submerged pipeline from the relative elevation.

Discussion : The internal and external pressure both vary with elevation. The external fluid gauge pressure is assumed to be zero at the fluid surface. If the internal fluid is lighter than the external fluid the maximum delta pressure will occur at the highest submerged point on the pipeline. Conversely, if the internal fluid is heavier than the external fluid the maximum delta pressure will occur at the lowest point on the pipeline.

Figures :

Input Variables :

  • ρe = External Fluid Density
  • ρi = Fluid Density
  • P1 = Section 1 Fluid Gauge Pressure
  • Z1 = Point 1 Elevation Above Datum
  • Z2 = Point 2 Elevation Above Datum
  • Zs = Fluid Surface Elevation Above Datum
  • g = Standard Gravity Acceleration At Sea Level

Output Variables :

  • ΔP = Pipe Wall Delta Pressure
  • P2 = Section 2 Fluid Gauge Pressure
  • Pe = External Fluid Gauge Pressure

Calculation :

P2 = P1 + ρi g ( Z1 - Z2 )
Pe = ρe g ( Zs - Z2 )
ΔP = P2 - Pe

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CALC : Flow : Bernoulli 072 : Submerged Pipe Wall Delta Pressure From Fluid Height : Calculator

Description : Calculate the delta static pressure across the pipe wall of a submerged pipeline from the external fluid height or depth.

Discussion : The internal pressure is known. The external pressure varies with elevation. The external fluid gauge pressure is assumed to be zero at the fluid surface.

Figures :

Input Variables :

  • ρe = External Fluid Density
  • H = Section Fluid Depth Below Surface
  • P2 = Section 2 Fluid Gauge Pressure
  • g = Standard Gravity Acceleration At Sea Level

Output Variables :

  • ΔP = Pipe Wall Delta Pressure
  • Pe = External Fluid Gauge Pressure

Calculation :

Pe = ρe g H
ΔP = P2 - Pe

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CALC : Pipe : Wall Thickness 012 : ASME B31.4 and ASME B31.8 Pipeline Hoop Stress Based On Nominal Wall Thickness : Calculator

Description : Calculate the pipe wall hoop stress from the nominal wall thickness for ASME B31.4 and B31.8.

Discussion : The hoop stress calculation includes the corrosion allowance.

References :

Input Variables :

  • D = Pipe Nominal Diameter
  • P = Pipeline Design Gauge Pressure
  • tn = Pipe Nominal Wall Thickness

Output Variables :

  • S = Pipeline Hoop Stress

Calculation :

S = ( P D ) / ( 2 tn )

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CALC : Pipe : Wall Thickness 013 : ASME B31.4 and ASME B31.8 Pipeline Hoop Stress Based On Hoop Wall Thickness : Calculator

Description : Calculate the pipe wall hoop stress from the minimum wall thickness for ASME B31.4 and B31.8.

Discussion : The hoop stress is calculated for the minimum wall thickness by subtracting the corrosion allowance from the nominal wall thickness.

References :

Input Variables :

  • A = Pipe Total Corrosion Allowance
  • D = Pipe Nominal Diameter
  • P = Pipeline Design Gauge Pressure
  • tn = Pipe Nominal Wall Thickness

Output Variables :

  • S = Pipeline Hoop Stress
  • t = Pipe Hoop Wall Thickness

Calculation :

t = tn - A
S = ( P D ) / ( 2 t )

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CALC : Pipe : Wall Thickness 021 : ASME B31.8 Pipe Wall Thickness - Onshore Pipeline : Calculator

Description : Calculate the ASME B31.8 wall thickness from hoop stress for onshore pipelines.

Discussion : The allowable hoop stress is calculated from the design factor and the specified minimum yield stress SMYS.

References :

Calculation Steps :

  • Wall thickness
  • ID and D over t ratio

Input Variables :

  • A = Pipe Total Corrosion Allowance
  • D = Pipe Nominal Diameter
  • E = ASME Longitudinal Weld Joint Factor
  • F1 = Pipeline Hoop Stress Factor
  • P = Pipeline Design Gauge Pressure
  • Sy = Pipeline SMYS - Specified Minimum Yield Stress
  • T = ASME B31 Temperature Derating Factor

Output Variables :

  • ID = Pipe Nominal Inside Diameter
  • dot = Pipeline Diameter Over Wall Thickness Ratio
  • t = Pipe Hoop Wall Thickness
  • tn = Pipe Nominal Wall Thickness

Calculation :

t = ( P D ) / ( 2 F1 E Sy T )
t = ( P D ) / ( 2 Sy )
tn = t + A
ID = D - 2 tn
dot = D / tn

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CALC : Pipe : Wall Thickness 022 : ASME B31.8 Pipe Wall Thickness - Offshore Pipeline And Platform : Calculator

Description : Calculate the ASME B31.8 wall thickness from hoop stress for offshore pipelines and platforms.

Discussion : Use the standard ASME B31.8 hoop stress design factors, or use a custom design factor. To use a custom design factor select custom in the zone type selct box, and enter a custom design factor. For standard zone types you do not need to enter a design factor. To plot the custom design factor you must select the custom zone type.

References :

Calculation Steps :

  • Allowable hoop stress
  • Wall thickness
  • ID and D over t ratio

Options :

  • Zone type : pipeline, platform or custom

Input Variables :

  • ΔP = Pipe Wall Delta Pressure
  • A = Pipe Total Corrosion Allowance
  • D = Pipe Nominal Diameter
  • F = Pipeline Hoop Stress Factor
  • Sy = Pipeline SMYS - Specified Minimum Yield Stress
  • T = ASME B31 Temperature Derating Factor
  • Z = Zone Type

Output Variables :

  • ID = Pipe Nominal Inside Diameter
  • S = Allowable Hoop Stress
  • dot = Pipeline Diameter Over Wall Thickness Ratio
  • t = Pipe Hoop Wall Thickness
  • tn = Pipe Nominal Wall Thickness

Calculation :

 If Z = 1 : Offshore Pipeline
  S = 0.72 Sy
 Otherwise If Z = 2 : Offshore Platform
  S = 0.5 Sy
 Otherwise If Z = 3 : Custom Factor
  S = F Sy
 End of If Block
t = ( ΔP D ) / ( S T )
t = ( ΔP D ) / ( 2 S )
tn = t + A
ID = D - 2 tn
dot = D / tn

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CALC : Pipe : Wall Thickness 023 : ASME B31.8 Pipeline SMYS Temperature Derating Factor : Calculator

Description : Calculate the ASME B31.8 temperature derating factor for pipeline design maximum temperature.

Discussion : The derating factors are valid upto 232 C (450 F) only. For temperatures above that level use material specific data.

References :

Input Variables :

  • tmax = Design Temperature

Output Variables :

  • T = ASME B31 Temperature Derating Factor

Calculation :

If tmax <= 1090 / 9
  T = 1
Otherwise
  T = 1.1453333333 - 0.0012 tmax
End of If Block

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CALC : Pipe : Wall Thickness 024 : ASME B31.8 Charpy V-Notch Toughness : Calculator

Description : Calculate the ASME B31.8 Charpy v-notch fracture toughness.

Discussion : The toughness values are valid for single phase gas pipelines only. For two phase pipelines a higher toughness energy may be required.

References :

Options :

  • Fracture toughness model : AISI American Iron And Steel Institute : BCL Battelle Columbus Laboratories : BGC British Gas Council : BSC British Steel Corporation.

Input Variables :

  • C = Charpy V Notch Type
  • D = Pipe Nominal Diameter
  • S = Pipeline Hoop Stress
  • t = Pipe Nominal Wall Thickness

Output Variables :

  • cvn = Charpy V-Notch Absorbed Energy

Calculation :

 If C = 1 : AISL American Iron And Stell Institute
  cvn = 1.146331e-11 S 3 / 2 √( D )
 Otherwise If C = 2 : BCL Battelle Columbus laboratories
  cvn = 2.829359e-15 S 2 D 1 / 3 t 1 / 3
 Otherwise If C = 3 : BGC British Gas Council
  cvn = 1.943328e-8 S D / √( t )
 Otherwise If C = 4 : BSC British Steel Corporation
  cvn = 6.681080e-16 S 2 D
 End of If Block

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