Effect of Operating Pressure and Dent Depth on Burst Strength of NPS30 Linepipe With Dent–Crack Defect

Abstract

Buried linepipe can be exposed to various external interferences and corrosive environment and as a result, damage in the form of dent or corrosion or crack or gouge or combination of any of these damages can form in the pipe wall. A defect combining dent and crack, often known as dent–crack defect, which may lead to a rupture or leak in the pipe wall and hence, the pipeline operator becomes concerned about the performance and safety of the pipeline. A research was recently completed at the Centre for Engineering Research in Pipelines (CERP), University of Windsor to study the influence of dent depth and operating line pressure on the pressure capacity (burst strength) of 30 in. diameter and X70 grade linepipe. This study found that the dent depth of 12% with crack depth of 4 mm or more can reduce the pressure capacity by 38%. This paper discusses the test specimens, test setup, test procedure, test results, and data obtained from finite element analyses.

Safe burst strength of a pipeline with dent–crack defect: Effect of crack depth and operating pressure

“…Also, it can be assumed that a failure occurs when the maximum equivalent plastic (MEP) strain at any integration point reaches the maximum equivalent plastic strain at rupture obtained from material tensile tests. As result, the rupture strain can be conservatively considered as unit [29,30]. In the FE model, it was assumed that a failure occurs when the Jintegral (J) at any integration point around crack tip reaches the maximum value of 1.15 J 1c which is equivalent to unite plastic strain.…”

Residual ultimate strength of offshore metallic pipelines with structural damage – a literature review

“…They might be caused by abnormal or accidental events including dropped objects, dragging anchors, fishing equipment, sinking vessels, mudslides and harsh environments such as extreme waves and currents (Bjørnøy et al 2000;DNV 2010;Abeele et al 2013;Ghaednia et al 2015b). Under these circumstances, prediction of the strength of a pipeline is a subject that has attracted the attention of many researchers such as Dyau and Kyriakides (1993), Lancaster and Palmer (1996a) (1996), Estekanchi and Vafai (1999), Bjørnøy et al (2000), Bruschi et al (2005), Vitali et al (2005), Vaziri and Estekanchi (2006), Bartolini et al (2014), Ghaednia et al (2015a), Ghaednia et al (2015b) and Rajabipour and Melchers (2015). Relevant research can not only clarify the inner mechanism of the pipeline structure failure, but also facilitates the decision-making in engineering practice when pipelines undergo structural damage.…”

“…For shallow water (water depth less than 300 m), the dominant load is internal pressure and over-internal pressure could lead to bursting (EIA 2010). The past few decades have seen considerable research such as Fu and Kirkwood (1995), Estekanchi and Vafai (1999), Loureiro et al (2001), Kim et al (2002), Benjamin and Andrade (2003), Vaziri and Estekanchi (2006), , , Ghaednia et al (2015a) and Ghaednia et al (2015b), on the bursting capacity of pipelines subjected to internal pressure. With the exploration of energy into deep water (water depth between 300 and 1500 m) or ultra-deep water (water depth greater than 3000 m), the load is gradually dominated by external hydro-static pressure and the buckling collapse could occur as a result of over-external pressure.…”

Numerical investigation of residual ultimate strength of dented metallic pipes subjected to pure bending

“…Additionally, standards such as BSI (2005) and DNV (2013) have proposed relevant information for dented pipes to guide the design. Other relevant research on dents and other types of damage can also be seen from Macdonald and Cosham (2005), Gresnigt et al (2007), Mohd et al (2014), Ghaednia et al (2015), Mohd et al (2015), Lee et al (2017), etc.…”

“…Structural damage in terms of a dent, metal loss and/or a crack on metallic pipes is unavoidable in engineering structures (Yang et al 2007;Manes et al 2012;Ghaednia et al 2015;Zhang et al 2015;. The occurrence of damage could undermine structural integrity and strength, which may induce detrimental consequences.…”