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API RP 1111 Pipeline Collapse Pressure

Calculate API RP 1111 limit state pipeline external collapse pressure and propagating buckle pressure.

The external pressure should be calcuated for the maximum water depth (highest astronomical tide plus storm surge). The internal pressure should be the maximum sustainable pressure (normally zero).

Reference : API RP 1111 : Design, Construction, Operation, and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design) (2011)

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CALCULATOR : API RP 1111 Section 4.3.2 Pipeline External Collapse And Propagating Buckle Check [PLUS]   ±

Calculate pipeline collapse pressure and buckle propagation pressure from pipe wall thickness (API RP 1111 section 4.3.2).

The pipe internal pressure should be set to the maximum sustainable pressure (normally equal to zero). During installation the corrosion allowance should be ignored. If the pipe fails both the collapse pressure check and the propagating buckle check, buckle arrestors should be considered.

Tool Input

  • pletype : Local External Pressure Type
    • Pleu : User Defined Local External Pressure
  • plitype : Local Internal Pressure Type
    • Priu : User Defined Internal Pressure At Reference Elevation
    • Pliu : User Defined Internal Pressure At Local Elevation
  • 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
  • syutype : Stress Table Type
  • mattype : Yield Stress Type
    • SMYSu : User Defined Specified Minimum Yield Stress
  • tfactype : Temperature Derating Type
    • ftu : User Defined Temperature Reduction Factor
  • modptype : Pipe Material Type
    • νu : User Defined Pipe Poisson's Ratio
    • Eu : User Defined Pipe Elastic Modulus
  • walltype : Corrosion Allowance Type
  • pectype : External Collapse Factor Type
    • fou : User Defined Collapse Factor
  • peptype : Propagating Buckle Factor Type
    • fpu : User Defined Propagating Buckle Factor
  • tc : Corrosion Allowance
  • Td : Design Temperature
  • ρf : Internal Fluid Density
  • ρe : External Fluid Density
  • Zr : Reference Elevation
  • Zl : Local Elevation
  • Zs : Surface Elevation

Tool Output

  • ΔPl : Delta External Over Pressure Across Pipe Wall
  • ν : Pipe Poisson's Ratio
  • E : Pipe Elastic Modulus
  • ID : Pipe Inside Diameter
  • OD : Pipe Outside Diameter
  • OD/tn : Diameter Over Wall Thickness Ratio
  • Pc : External Collapse Pressure
  • Pca : Allowable External Collapse Pressure
  • Pce : Elastic Collapse Pressure
  • Pcy : Plastic Collapse Pressure
  • Ple : External Pressure
  • Ple/Pca : External Pressure Over Allowable Collapse Pressure Ratio (≤ 1)
  • Ple/Ppra : External Pressure Over Allowable Propagating Buckle Pressure Ratio (≤ 1)
  • Pli : Local Internal Pressure
  • Pp : Propagating Buckle Pressure
  • Ppa : Allowable Propagating Buckle Pressure
  • Sy : Temperature Derated Yield Stress
  • fo : External Collapse Factor
  • fp : Propagating Buckle Factor
  • ft : Temperature Derating Factor (ASME B31.8)
  • th : Collapse Wall Thickness
  • tn : Nominal Wall Thickness
  • wd : Water Depth

CALCULATOR : API RP 1111 Section 4.3.2 Pipeline Ovality [FREE]   ±

Calculate pipeline ovality (API RP 1111 section 4.3.2).

Out of roundness is the difference between the maximum and minimum diameter of the pipe. DNV ovality is equal to 2 x API ovality. All tolerances should be entered as positive values.

For line pipe with diameter D < 0.0603 [ m ] the out of roundness is included with the diameter tolerance. For line pipe with diameter D ≥ 0.2191 [ m] the out of roundness may also be calculated from the inside diameter.

Reference : API 5L : Specification for Line Pipe : Annex J.6 Offshore Pipeline : Table J.3 Out Of Roundness Tolerance

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
  • dntype : Pipe OD Or Pipe ID
  • pipetype : Line Pipe Type
  • toltyped : Out Of Roundness Tolerance Type
    • Dxu : User Defined Out Of Roundness Ratio
    • Dau : User Defined Out Of Roundness
    • Dmaxu : User Defined Maximum Diameter
    • Dminu : User Defined Minimum Diameter

Tool Output

  • D : Nominal Pipe Diameter
  • D/tn : Diameter Over Wall Thickness Ratio
  • Dmax : Maximum Diameter
  • Dmin : Minimum Diameter
  • ID : Nominal Inside Diameter
  • OD : Nominal Outside Diameter
  • OOR : Out Of Roundness
  • fapi : API Ovality
  • fdnv : Out Of Roundness Ratio And DNV Ovality
  • tn : Nominal Wall Thickness

CALCULATOR : API RP 1111 Section 4.3.1 Pipeline Temperature Derated Yield Stress And Tensile Stress [FREE]   ±

Calculate temperature derating factor, and derated yield stress and tensile stress from temperature (API RP 1111 section 4.3.1 and 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 : API RP 1111 Pipeline Diameter And Wall Thickness Schedule [FREE]   ±

Calculate API RP 1111 pipeline diameter and wall thickness from pipe schedule.

The pressure design thickness equals the nominal wall thickness minus the corrosion allowance. The corrosion allowance includes mechanical allowances such as threads and damage etc. Use the Result Table option display a table of pressure design wall thickness versus wall thickness for the selected diameter schedule. Fabrication tolerance is included in the design factor and 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
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