Track-4-Ben-Verhagen - Validation of ASME 31G and RSTRENG

VALIDATON OF THE ASME B31G AND RSTRENG

METHODOLOGIES FOR THE DETERMINATION OF THE

BURST PRESSURE OF CORRODED PIPES IN API 5L X70 / EN

10208-2 L485

Frédéric Dewint, AIBFrédéric Dewint, AIB--Vinçotte InternationalVinçotte International

33rdrd ASME India Oil & Gas Pipeline Conference, 2011, February 3ASME India Oil & Gas Pipeline Conference, 2011, February 3--5, Goa, India5, Goa, India

CONTENTS

• OBJECTIVES OF THE STUDY

• FAILURE PRESSURE ACCORDING ASME B31G AND RSTRENG

• TEST PROGRAM

- Burst tests

- Strain gauge measurements

- Calculations in accordance with ASME B31G and RSTRENG

- Linear and Nonlinear Finite Element Calculations

• CONCLUSIONS

VALIDATION OF THE ASME B31G AND THE RSTRENG VALIDATION OF THE ASME B31G AND THE RSTRENG

METHODOLOGIES FOR PIPE MATERIAL X70 / L485METHODOLOGIES FOR PIPE MATERIAL X70 / L485



REMARK

The study was performed in collaboration between

AIB-Vinçotte International (www.vincotte.com)

Fluxys (www.fluxys.com)

Labo Soete of the Ghent University (www.tribology-fatigue.ugent.be)



OBJECTIVES OF THE STUDY

• Validate ASME B31G and RSTRENG methodologies on pipe in X70 / L485 material with supplementary requirements related to :

- ratio yield strength / tensile strength

- impact testing at –20°C

• Demonstrate the real safety margin of corroded high pressure gaspipelines in X70 / L485 against bursting under internal pressureloading.

• Assess the capability of Finite Element calculations for predicting the failure pressure of corroded pipes and in a further step thefailure pressure of corroded fitings.



ASME B31G & RSTRENG

• The ASME B31G and RSTRENG methodologies are used for the determination of the remaining strength of externally corroded pipe subjected to internal pressure loading.

• Both methodologies modelize defects by their depth d and by their length L in the longitudinal direction. The defect width w is not considered explicitly in the calculation.

• RSTRENG allows to take into account more accurately the corrosion defect geometry.



LIMITATIONS

• Limited to corrosion on weldable pipeline steels categorized as carbon steels or high strength low alloy steels.

• Do not apply to welds except to corrosion anomalies in submerged arc seam welds.

• Defects caused by mechanical damage, such as gouges and grooves, are prohibited.

• Limited to anomalies having depths lower than 80 percent of the wall thickness.

• Limited to defects which have relatively smooth contours and cause low stress concentrations (e.g. electrolytic or galvanic corrosion, loss of wall thickness due to erosion).

• Only internal pressure loading is considered.



ASME B31G CALCULATION METHOD

failure pressure is Pfail = 2 x Sfail x t / D with :

D : diameter of the pipe

t : wall thickness of the pipe

Sfail : failure stress = S (1-A/Ao)/[1-(A/Ao)(MT-1)]

S : flow stress = 1.1 SMYS

A : defect area in the longitudinal plane through the wall thickness ; B31G considers A = (2/3) d L

Ao : is L t

MT : two-term Folias factor ; f(L, Dt)

L : axial extent of the defect

d : maximum defect depth



RSTRENG CALCULATION METHOD

failure pressure is Pfail = 2 x Sfail x t / D with :

D : diameter of the pipe

t : wall thickness of the pipe

Sfail : failure stress = S (1-A/Ao)/[1-(A/Ao)(MT-1)]

S : flow stress = SMYS + 10 ksi = SMYS + 69 MPa

A : defect area in the longitudinal plane through the wall thickness ; if no detailed analysis, i.e. : 0.85 d L

Ao : is L t

MT : three-term Folias factor ; f(L, Dt)

L : axial extent of the defect

d : maximum defect depth



TEST PROGRAM

• To demonstrate the validity of the ASME B31G and RSTRENG methodologies for pipe material X70/L485, a test program was defined by Vinçotte in collaboration with Fluxys and the Laboratory Soete of Ghent University :

- burst testing of the test pieces with artificial defects

- comparison with failure pressure from ASME B31G & RSTRENG

- comparison with failure pressure calculated by finite element method

- comparison of strain gauge measurements with the strains from finite element calculations



TEST PIECE PARAMETERS



TEST PIECE 4 drawing



Strain gauges installation



Strain gauges installation



TEST PIECE 1 tensile test results



TEST PIECE 1 impact test results – 2 o’ clock



3D model



TP1 : DN600 tactual = 11.3 mm Pdesign = 80 bar

Defect 3 : L = 210 mm d = 4.1 mm w = 100* mm

Actual Burst Pressure : 214 Bar

ASME B31G : 166 bar RSTRENG : 164 bar FEM-NL : 175 bar




Defect 2 : L = 200 mm d = 6.8 mm w = 128 mm

Actual Burst Pressure : 150 bar
















RESULTS



Strain Gauge Measurement Results



Comparison strain gauge measurements / FEM



Test Piece 2 - defect 1 / Von Mises stresses

TP4 defect 1 - Von Mises strain : max. 1.1% at 75 bar



TP4 defect 1 - Von Mises strain : max. 1.8% at 82.5 bar



TP4 defect 1 - Von Mises strain : max. 3.2% at 90 bar



TP4 defect 1 - Von Mises strain : max. 5.1% at 97.5 bar



TP4 defect 1 - Von Mises strain : max. 23 % at 105 bar





CONCLUSIONS

• The failure pressures calculated with ASME B31G and RSTRENG method are conservative values compared with the actual bursting pressure values.

• The failure pressures calculated with the nonlinear FEM method are conservative values compared with the actual bursting pressure values.

• The failure pressures calculated with the linear FEM method are too conservative in order to be useful for practice.

• The correspondence between the strain gauge measurements and the FEM calculated strains was good in the range were measurements were possible.

• Corroded pipe in X70 / L485, as ordered in Belgian practice, has large safety margin against bursting under internal pressure.

Questions & Answers



Documents

Track-4-Ben-Verhagen - Validation of ASME 31G and RSTRENG