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Single Pipeline Defect Modules

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CALCULATOR MODULE : ASME B31G Level 1 Defect Assessment   ±

Calculate ASME B31G level 1 corrosion defect assessment for blunt type defects.

The level 1 assessment calculates the allowable pressure from the maximum defect depth and defect length, using either the original ASME B31G method (1999), or the modified ASME B31G method. 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.

ASME B31G is suitable for blunt defects of all types, including corrosion, mechanical damage and grinding repairs etc. For crack type defects the NG-18 crack defect calculators are recommended. The effective area method can also be used for blunt defects.

Reference : ANSI/ASME B31G Manual For Determining The Remaining Strength Of Corroded Pipelines (2012)

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CALCULATOR MODULE : 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 MODULE : PRCI PR 3805 RSTRENG Level 1 0.85 RSTRENG   ±

Calculate the PR-3-805 RSTRENG level 1 (0.85 RSTRENG) corrosion defect assessment for blunt defects.

Use the level 1 caculators to calculate the allowable pressure from the maximum defect depth and the defect length using the 0.85 RSTRENG method. Pressure derating is required if the allowable pressure is less than the maximum operating pressure. The measured pipe diameter and wall thickness should be used in the calculations.

PR-3-805 RSTRENG is suitable for blunt corrosion defects and mechanical damage defects (eg from grinding). ASME B31G is also suitable for blunt defects. AGA NG-18 is suitable for crack type defects.

The calculators which include elevation can be used to include external pressure, and to calculate the allowable pressure at a reference elevation (for Example to calculate the allowable pressure at the pressure control location). Set the external pressure = 0 for dry pipelines.

For pipelines operating above 120 C the yield stress and ultimate stress should be derated. Material test data should be used if it is available. Flow stress can be calculated using either the RSTRENG equation, or the ASME equation.

Reference : PRCI, Pipeline Research Committee Project, PR-3-805, “A Modified Criterion for Evaluating the Remaining Strength of Corroded Pipe,” December 22, 1989, PRCI PR-3-805 (R-STRENG) With RSTRENG Disk.

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CALCULATOR MODULE : DNVGL RP-F101 Single Corrosion Defect   ±

Calculate DNVGL RP F101 allowable pressure for single corrosion defects.

Allowable pressure can be calculated for pressure load only for single longitudinal defects. For circumferential defects, or defects with compressive axial load use the combined pressure and compression load calculator. For circumferential defects the defect width is greater than the defect length. The allowable pressure can be calculated using either the calibrated safety factor (CSF) in section 3, or allowable stress design (ASD) in section 4. The system effect factor accounts for the measurement uncertainty when there are multiple defects of a similar size.

Reference : DNVGL-RP-F101 : Corroded Pipelines (Download from the DNVGL website)

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