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AGA NG18 Level 1 Defect Assessment

Calculate AGA NG-18 level 1 crack defect assessment.

The level 1 assessment calculates the allowable pressure from the maximum defect depth and defect length. Pressure derating is required if the allowable pressure is less than the maximum operating pressure.

The flow stress can be calculated as either 1.1 x SMYS, SMYS + 69 MPa, or 1/2 (SMYS + SMTS). For pipelines operating at high temperature, the SMYS and SMTS should be derated.

For submerged pipelines, or to calculate the allowable pressure at a reference elevation, use the level 1 calculator including elevation. The allowable local pressure is calculated including external pressure (use the external pressure = 0 for dry pipelines). The allowable reference pressure is calculated from the local allowable pressure, and the relative elevation.

AGA NG-18 is suitable for crack defects. For blunt defects including corrosion, mechanical damage and grinding repairs etc the ASME B31G or RSTRENG calculators are recommended.

Reference : AGA Pipeline Research Committee NG-18 Report 204 Ductile Fracture Properties of Selected Linepipe Steels

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CALCULATOR : AGA NG-18 Level 1 Crack Defect Assessment [FREE]   ±

Calculate AGA NG-18 level 1 crack defect allowable pressure from the crack length and maximum crack depth.

Elevation is ignored. The external pressure is assumed equal to zero. :Use the level 2 assessment for defects which have failed the level 1 assessment.

Tool Input

  • schdtype : Schedule Type
  • diamtype : Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tu : User Defined Wall Thickness
  • syutype : Stress Table Type
  • mattype : Material Type
    • SMYSu : User Defined Specified Minimum Yield Stress
    • SMTSu : User Defined Specified Minimum Tensile Stress
  • sflowtype : Flow Stress Type
    • Su : User Defined Flow Stress
  • sfactype : Safety Factor Type
    • SFu : User Defined Safety Factor
  • caxtype : Charpy Specimen Cross Section Area Type
    • Au : User Defined Cross Section Area
  • L : Defect Length
  • d : Defect Depth
  • E : Elastic or Young's Modulus E
  • CVN : Charpy V-Notch Absorbed Energy

Tool Output

  • Cx : Charpy Specimen Cross Section Area
  • ID : Pipe Inside Diameter
  • M : Defect z Value
  • OD : Pipe Outside Diameter
  • Pa : Maximum Allowable Pressure
  • Pb : Burst Pressure
  • Pf : Failure Pressure
  • S : Flow Stress
  • SF : Safety Factor
  • SMTS : Specified Minimum Tensile Stress
  • SMTS/SMYS : Tensile Stress Over Yield Stress Ratio
  • SMYS : Specified Minimum Yield Stress
  • Z : Defect Z Factor
  • Zc : Defect Z C Factor
  • Zf : Defect Z F Factor
  • ZoZ : Defect Z Ratio Factor
  • d/t : Defect Depth Over Wall Thickness Ratio
  • t : Pipe Wall Thickness
  • tmin : Minimum Remaining Wall Thickness

CALCULATOR : AGA NG-18 Level 1 Crack Defect Assessment Including Elevation [PLUS]   ±

Calculate AGA NG-18 level 1 crack defect local allowable pressure and reference allowable pressure from the crack length, maximum crack depth and elevation. The local allowable pressure includes the external pressure (set the external pressure to zero for dry pipelines). The allowable reference pressure is calculated from the local allowable pressure and the elevation.

Use the level 2 assessment for defects which have failed the level 1 assessment.

Tool Input

  • schdtype : Schedule Type
  • diamtype : Diameter Type
    • ODu : User Defined Outside Diameter
    • IDu : User Defined Inside Diameter
  • wtntype : Wall Thickness Type
    • tu : User Defined Wall Thickness
  • plitype : MOP Pressure Type
    • ρf : Internal Fluid Density
    • Zr : Reference Elevation Relative To Datum
    • Zl : Local Elevation Relative To Datum
  • pletype : External Pressure Type
    • Pleu : User Defined Local External Pressure
    • ρe : External Fluid Density
    • Zs : Surface Elevation Relative To Datum
  • syutype : Stress Table Type
  • mattype : Material Type
    • SMYSu : User Defined Specified Minimum Yield Stress
    • SMTSu : User Defined Specified Minimum Tensile Stress
  • sflowtype : Flow Stress Type
    • Su : User Defined Flow Stress
  • sfactype : Safety Factor Type
    • SFu : User Defined Safety Factor
  • caxtype : Charpy Specimen Cross Section Area Type
    • Au : User Defined Cross Section Area
  • L : Defect Length
  • d : Defect Depth
  • E : Elastic or Young's Modulus E
  • CVN : Charpy V-Notch Absorbed Energy

Tool Output

  • Cx : Charpy Specimen Cross Section Area
  • ID : Pipe Inside Diameter
  • M : Defect z Value
  • OD : Pipe Outside Diameter
  • Pb : Burst Pressure
  • Pf : Failure Pressure At Local Elevation
  • Pla : Allowable Pressure Local Elevation
  • Ple : External Pressure At Local Elevation
  • Pra : Allowable Pressuure At Reference Elevation
  • S : Flow Stress
  • SF : Safety Factor
  • SMTS : Specified Minimum Tensile Stress
  • SMTS/SMYS : Tensile Stress Over Yield Stress Ratio
  • SMYS : Specified Minimum Yield Stress
  • Z : Defect Z Factor
  • Zc : Defect Z C Factor
  • Zf : Defect Z F Factor
  • ZoZ : Defect Z Ratio Factor
  • d/t : Defect Depth Over Wall Thickness Ratio
  • t : Pipe Wall Thickness
  • tmin : Minimum Remaining Wall Thickness

CALCULATOR : AGA NG-18 Minimum Charpy Fracture Toughness [FREE]   ±

Calculate AGA NG-18 minimum required Charpy V notch energy (CVN).

The minimum Charpy energy can be calculated using either the AISI (American Iron and Steel Institute), BCL (Battelle Columbus Labs), BGC (British Gas Corporation), or BSC (British Steel Corporation) methods.

Reference : ANSI/ASME B31.8 : Gas Transmission And Distribution Piping Systems : section 841.1

Tool Input

  • cvntype : Charpy Energy Calculation Type
  • D : Nominal Outside Diameter
  • t : Nominal Wall Thickness
  • S : Hoop Stress

Tool Output

  • CVN : Charpy V Notch Energy
CALCULATOR : AGA NG-18 Level 0 Critical Defect Length And Fracture Toughness [FREE]   ±

Calculate AGA NG-18 level 0 critical defect length and minimum required fracture toughness from flow stress and hoop stress (AS 2885.1). `
`The critical defect length is calculated using the Folias factor Mt. The required fracture toughness and Charpy V notch energy to prevent fracture are calculated from the initiation defect length. The inititation defect length is normally taken as 80% - 90% of the critical defect length.

Reference : Australian Standard AS 2885.1 : Pipelines - Gas And Liquid Petroleum Part 1 : Design And Construction

Tool Input

  • 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 : Fabrication Tolerance Type
    • xu : User Defined Negative Wall Thickness Fraction
    • Hu : User Defined Negative Wall Thickness Allowance
  • modptype : Pipe Material Type
    • Eu : User Defined Pipe Elastic Modulus
  • idltype : Inititation Defect Length Type
    • Fiu : User Defined Initiation Defect Length Factor
    • IDLu : User Defined Initiation Defect Length
  • G : Corrosion Allowance
  • Sf : Flow Stress
  • Sh : Hoop Stress
  • Ac : Charpy Test Piece Fracture Area

Tool Output

  • CDL : Critical Defect Length
  • CVG : Convergence Factor
  • CVN : Charpy V Notch Fracture Energy
  • E : Young's Modulus
  • H : Wall Thickness Fabrication Allowance
  • ID : Pipe Inside Diameter
  • IDL : Inititation Defect Length (< CDL)
  • Mt : Folias Factor
  • OD : Pipe Outside Diameter
  • OD/tn : Pipe Diameter Over Wall Thickness Ratio
  • Sf/Sh : Flow Stress Over Hoop Stress Ratio (> 1)
  • tm : Minimum Fabrication Wall Thickness
  • tn : Nominal Wall Thickness
  • tw : Pressure Design Wall Thickness
  • xf : Wall Thickness Fabrication Fraction
CALCULATOR : AGA NG-18 Derated Yield Stress And Tensile Stress [FREE]   ±

Calculate the derated yield stress, ultimate stress and flow stress for steel pipelines operating above 120 C for AGA NG-18.

Derating is calculated according to ASME B31.8. The derating factors are valid upto 232 C (450 F) only. For temperatures above 232 C (450 F) use material specific data. The derating factor is assumed to be valid for yield stress and tensile stress.

Reference : ANSI/ASME B31.8 : Gas Transmission And Distribution Piping Systems : section 841.1 table 841.1.8-1

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 : AGA NG-18 Pipe Diameter And Wall Thickness Schedule [FREE]   ±

Calculate pipe nominal wall thickness and diameter for AGA NG-18.

The nominal pipe diameter and wall thickness or the measured pipe diameter and wall thickness can be used for the AGA NG-18 checks.

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
  • ttoltype : Wall Thickness Fabrication Tolerance Type
    • txu : User Defined Negative Wall Thickness Fraction
    • tfu : User Defined Negative Wall Thickness Allowance
  • c : Wall Thickness Corrosion Allowance

Tool Output

  • ID : Nominal Inside Diameter
  • OD : Nominal Outside Diameter
  • OD/tn : Diameter Over Wall Thickness Ratio
  • tf : Wall Thickness Fabrication Allowance
  • tm : Minimum Wall Thickness
  • tn : Nominal Wall Thickness
  • tp : Pressure Design Wall Thickness
  • tx : Wall Thickness Fabrication Fraction
CALCULATOR : AGA NG-18 Pipe Diameter From Circumference [FREE]   ±

Calculate pipe outside diameter from circumference, or pipe circumference from outside diameter for AGA NG-18.

Use either the nominal pipe diameter and wall thickness, or the measured pipe diameter and wall thickness for the AGA NG-18 checks.

Tool Input

  • odtype : Pipe Outside Diameter Measurement Type
    • ODu : Measured Outside Diameter
    • OCu : Measured Outside Circumference

Tool Output

  • OC : Pipe Outside Circumference
  • OD : Pipe Outside Diameter
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