Leak-before-break in cast iron mains: a failure analysis of a catastrophic pipe burst on Harris Street, Sydney

This article analyses the failure of a 500 mm-diameter cast iron (CI) water pipe that catastrophically fractured in Sydney in 2013. According to metallurgical analysis and finite element simulation, a longitudinal pre-existing crack initiated from the adjacent bell-joint and eventually propagated to a critical length in the pipe barrel over a certain period. There was evidence of leakage prior to the burst incident but information was inconclusive whether it was exactly from this pipe. Fatigue caused by cyclic internal pressure was considered as the predominant factor in leading to crack growth. A numerical model was developed to describe crack growth behaviour using Paris' law, and metallurgical analysis and mechanical tests were conducted to support this investigation. Based on the field evidence and simulation results, the leak-before-break approach might be applicable in CI pipes to avoid severe consequences of trunk main bursts.

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Effect of temperature on the threshold fatigue crack growth behaviour of spheroidal graphite cast iron

International Journal of Pressure Vessels and Piping ◽

10.1016/0308-0161(93)90019-p ◽

1993 ◽

Vol 54 (3) ◽

pp. 497-522 ◽

Cited By ~ 4

Author(s):

J.H. Bulloch

Keyword(s):

Fatigue Crack ◽

Cast Iron ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Effect Of Temperature ◽

Spheroidal Graphite ◽

Growth Behaviour ◽

Crack Growth Behaviour ◽

Spheroidal Graphite Cast Iron ◽

Graphite Cast Iron

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Crack Shape Development for Leak-Before-Break Analysis in Pipelines

Volume 1: Pipeline and Facilities Integrity ◽

10.1115/ipc2018-78587 ◽

2018 ◽

Author(s):

Kathy Zhang ◽

Luyao Xu ◽

James Ferguson ◽

Dennis Zadery

Keyword(s):

Crack Length ◽

Crack Growth ◽

Essential Element ◽

Critical Length ◽

Assessment Method ◽

Critical Crack ◽

Critical Crack Length ◽

Simplified Approach ◽

Pressure Cycling ◽

Leak Before Break

Surface cracks in pipelines under certain service conditions may grow due to fatigue, which is caused by pressure (cycles). The leak-before-break (LBB) assessment method is employed to avoid any catastrophic failure prior to a detectable leakage. In the LBB analysis, crack critical length is an essential element for determining the pipeline leak or rupture. The common approach regarding the evaluation of LBB is to calculate the critical crack length and through-wall length under iven pressure cycling conditions. If the critical crack length is less than the through-wall length, LBB conditions could occur and be detected if leak detection capability is high. This involves complex calculations in crack fatigue growth and could result in extensive analysis if thepipeline has a large crack population. This paper presents a simplified approach for assessing the leak-before-break of the flawed pipelines. This approach is based on industrial code API 579-1/ASME FFS-1 Fitness-For-Service. Through the investigation of effects for different parameters on crack growth, including crack initial geometry, pipeline materials, loading conditions, pipeline diameter and wall thickness, it was determined that the crack initial aspect ratio is a major factor influencing crack growth and geometry evolution. Based on these parameters, a crack fatigue growth map was developed. By comparing the behaviors of different cases, it was confirmed that the proposed method is a valid approach for the pipeline LBB analysis.

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Comparison of DBEM and FEM Crack Path Predictions with Experimental Findings for a SEN-Specimen under Anti-Plane Shear Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.129 ◽

2007 ◽

Vol 348-349 ◽

pp. 129-132 ◽

Cited By ~ 7

Author(s):

Roberto G. Citarella ◽

Friedrich G. Buchholz

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Crack Front ◽

Crack Path ◽

Shear Loading ◽

Crack Growth Behaviour ◽

3D Crack Growth ◽

Corner Points ◽

Experimental Findings

In this paper detailed results of computational 3D fatigue crack growth simulations will be presented. The simulations for the crack path assessment are based on the DBEM code BEASY, and the FEM code ADAPCRACK 3D. The specimen under investigation is a SEN-specimen subject to pure anti-plane or out-of-plane four-point shear loading. The computational 3D fracture analyses deliver variable mixed mode II and III conditions along the crack front. Special interest is taken in this mode coupling effect to be found in stress intensity factor (SIF) results along the crack front. Further interest is taken in a 3D effect which is effective in particular at and adjacent to the two crack front corner points, that is where the crack front intersects the two free side surfaces of the specimen. Exactly at these crack front corner points fatigue crack growth initiates in the experimental laboratory test specimens, and develops into two separate anti-symmetric cracks with complex shapes, somehow similar to bird wings. The computational DBEM results are found to be in good agreement with these experimental findings and with FEM results previously obtained. Consequently, also for this new case, with complex 3D crack growth behaviour of two cracks, the functionality of the proposed DBEM and FEM approaches can be stated.

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Estimation of Creep Crack Growth Properties Using Circumferential Notched Round Bar Specimen for 12CrWCoB Rotor Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.397 ◽

2005 ◽

Vol 297-300 ◽

pp. 397-402

Author(s):

Je Chang Ha ◽

Joon Hyun Lee ◽

Masaaki Tabuchi ◽

A.Toshimitsu Yokobori Jr.

Keyword(s):

Crack Growth ◽

Axial Stress ◽

Creep Crack Growth ◽

Turbine Rotor ◽

Rotor Steel ◽

Creep Ductility ◽

Crack Growth Behaviour ◽

Creep Crack ◽

Round Bar ◽

Growth Properties

Most heat resisting materials in structural components are used under multi-axial stress conditions and under such conditions ductile materials often exhibit brittle manner and low creep ductility at elevated temperature. Creep crack initiation and growth properties are also affected by multi-axial stress and it is important to evaluate these effects when laboratory data are applied to structural components. Creep crack growth tests using circumferential notched round bar specimens are a simple method to investigate multi-axial stress effects without using complicated test facilities. Creep crack growth tests have been performed using a 12CrWCoB turbine rotor steel. In order to investigate the effects of multi-axial stress on creep crack growth properties, the tests were conducted for various notch depths at 650°C. The circumferential notched round bar specimen showed brittle crack growth behaviour under multi-axial stress conditions. Creep crack growth rate was characterized in terms of the C* parameter. A 12CrWCoB turbine rotor steel has been tested using circumferential notched round bar specimens with different multi-axiality. Circumferential notched round bar specimens show increased brittle creep crack growth behaviour due to the multi-axial stress condition. Creep crack growth properties could be predicted by allowing for the decrease of creep ductility under multi-axial conditions.

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