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Due to the extensive use of explosive devices in military conflicts, there has been a dramatic increase in life-threatening injuries and resultant death toll caused by explosive blasts. In an attempt to better understand the blast waves and mitigate the damages caused by such blast waves, various devices/systems have been developed to replicate the field blast scenarios in laboratory conditions. The East Carolina University Advanced Blast Wave Simulator (i.e., ECU-ABWS) is one such facility that can reproduce blast waves of various shapes and profiles. The peak overpressure of a blast is the key factor that causes the greatest number of damages, and it is essentially determined by the burst pressure of the blast. Therefore, a better understanding of the effects of burst pressure on blast generation and development is strongly desired to develop safer and more effective blast mitigation technologies. In the present study, a series of experiments were carried out in the ECU-ABWS to characterize the blast waves generated under different burst pressure conditions. While the incident (side-on) pressures at multiple locations along the blast propagation direction were measured using a temporally-resolved multi-point pressure sensing system, the time-evolutions of blast wave profiles were also qualitatively revealed by using a high-speed Schlieren imaging system. The synchronization of pressure sensing and Schlieren image acquisition enables us to extract more physical details of the dynamic blast wave development under different burst pressure conditions by associating the incident pressures and shock wave morphologies. In this study, the different burst pressures were achieved by altering the thickness of the membrane separating the driver section of pressurized gas and the driven section of air at atmospheric pressure. It is found that there is a linear relationship between the burst pressure and the peak overpressure. As the burst pressure increases (by increasing the membrane thickness), more clearly defined shock wavefronts are also observed along with the peak overpressure increase.

Large diameter Sour Service Pipelines are designed for the safe and efficient transportation of production fluids containing H2S. This service condition exposes the pipe to hydrogen embrittlement mechanisms and demands a material with high Sulfide Stress Cracking (SSC) resistance, and thus, a high fracture toughness in a representative sour environment. Engineering Critical Assessment (ECA) procedures are usually employed to determine the suitability of a pipeline design, These procedures require the correct determination of the material fracture mechanical properties. Although Method D of NACE TM0177_16 [1] using DCB specimens is the currently recognized testing methodology to evaluate SSC pipe performance, other type of tests could be employed for the purpose of an ECA. In the present paper, a fracture mechanics experimental program in sour environment is presented. Parent Pipe and Weld Material of Longitudinal Submerged Arc Welded (LSAW) large diameter pipes in H2S were studied. Fracture Toughness Parameters, such K-limit from standard DCB tests and K-threshold from Single Edge Notch Tension (SENT) specimens under constant loading, are compared and discussed. Furthermore, the fracture toughness values obtained from SENT specimens in sour environment are used to estimate the burst pressure using an ECA procedure.

Compared with the steel cylinders for liquefied petroleum gas (LPG), fully-wrapped fiber reinforced cylinders with non-metallic liners (type IV cylinders) have been widely used due to their advantages of light weight, corrosion resistance, low maintenance cost and no explosion when exposed in fire. However, for the heterogeneity of raw material performances and instability of manufacturing process, the mechanical performances of type IV cylinders show a certain dispersion. Therefore, in this study, a series of burst tests and pressure cycle tests on 89 type IV LPG cylinders (26.2 L, 2.1 MPa) were conducted to examine the performances of burst pressure and number of pressure cycles, and analyze the distribution characteristics. The total length of the experimental cylinder was 465 mm, the outer diameter and the thickness of the liner was 304 mm and 2 mm, respectively. Two types of cylinders were tested, with the thickness of composite overwrap in 2 mm and 4 mm, corresponding to the designed burst pressure of 12 MPa and 15 MPa. Burst test and pressure cycle test were conducted according to the standard GB/T 15385 and GB/T 9252, respectively. Results showed that the 59 cylinders had the similar crevasses morphology along the axial wall of liners after burst tests. Burst pressure of two design types fluctuated within the range of 11.4 MPa-12.5 MPa, and 13.7 MPa-16.0 MPa, respectively. The statistical results of burst pressure showed approximately normal distribution with a standard deviation of 0.263 MPa and 0.529 MPa. Also, the number of pressure cycles of 30 cylinders were all above 12,000 with a cycle frequency no more than 15 cycles per minute. Above studies have provided a data support for the recently published Chinese association standard T/CATSI 02 003-2019.

Tube integrity is an important aspect for safe and reliable operation of nuclear power plant steam generators. As a U.S. industry and licensing requirement, all in-service steam generator tubes shall retain structural integrity over the full range of normal operating conditions and design basis accidents by meeting the structural integrity performance criterion (SIPC) as given in NEI 97-06. The SIPC margin shall be maintained during plant operation between tube examinations. The burst strength of tubes subjected to wall thinning will depend on the extent and mode of degradation, and the magnitude of design loads to include pressure differential across the tube wall during normal operation and postulated accident conditions. In addition, non-pressure loads that can occur during postulated accident events shall be evaluated and included in the assessment of tube integrity if determined to significantly reduce the tube burst strength. The EPRI Flaw Handbook provides burst pressure relationships for flaws which include a reduction factor that accounts for the effect of applied bending stress on circumferential degradation. However, this previous industry work was only for planar crack-like flaws and did not directly address uniform volumetric wall loss which can have both axial and circumferential extent. This paper describes a test program to determine the effect of bending loads on the burst pressure of a tube with uniform thinning over a given axial length. The uniform thinning geometry was selected since it represented a bounding case of general wall loss and is conservative for calculating a tube repair limit for volumetric degradation for a given steam generator design. Tube repair limits are required for defining an upper limit on in-service degradation for which a tube is to be removed from service. Tube repair limits are cited in the Plant Technical Specifications, which is an important part of the licensing basis.

Compact heat exchangers for supercritical CO2 (sCO2) service are often designed with external, semi-circular headers. Their design is governed by the ASME Boiler & Pressure Vessel Code (BPVC) whose equations were typically derived by following Castigliano’s Theorems. However, there are no known validation experiments to support their claims of pressure rating or burst pressure predictions nor is there much information about how and where failures occur. This work includes high pressure bursting of three semi-circular header prototypes for the validation of three aspects: (1) burst pressure predictions from the BPVC, (2) strain predictions from Finite Element Analysis (FEA), and (3) deformation from FEA. The header prototypes were designed with geometry and weld specifications from the BPVC Section VIII Division 1, a design pressure typical of sCO2 service of 3,900 psi (26.9 MPa), and were built with 316 SS. Repeating the test in triplicate allows for greater confidence in the experimental results and enables data averaging. Burst pressure predictions are compared with experimental results for accuracy assessment. The prototypes are analyzed to understand their failure mechanism and locations. Experimental strain and deformation measurements were obtained optically with Digital Image Correlation (DIC). This technique allows strain to be measured in two dimensions and even allows for deformation measurements, all without contacting the prototype. Eight cameras are used for full coverage of both headers on the prototypes. The rich data from this technique are an excellent validation source for FEA strain and deformation predictions. Experimental data and simulation predictions are compared to assess simulation accuracy.

In this paper, three-dimensional finite element models are developed to simulate full-scale burst tests of corroded pipes containing multiple naturally occurring corrosion anomalies. Both the von Mises and Tresca yield criteria and associated flow rules are employed in finite element analysis (FEA). For the Tresca criterion, the corresponding constitutive model subroutine is developed and incorporated in the FEA. The accuracy of FEA is investigated by comparing the burst pressures observed in the tests and corresponding burst pressures predicted using FEA. The implications of using the von Mises and Tresca criteria for the accuracy of the predicted burst pressure are investigated. Sensitivity analyses are also carried out to investigate the impact on the predicted burst pressure due to the mesh density in the corroded region, characterization of the geometry of the corrosion cluster and different types of element (e.g. solid and shell elements) used in FEA. The results suggest that the Tresca criterion always underestimates the burst pressure and the von Mises yield criterion predicts the burst pressure accurately. This study demonstrates the feasibility of using high-fidelity FEA and the Tresca yield criterion to simulate full-scale burst tests of corroded pipes and therefore establish a large database of burst pressure capacities of corroded pipes that can be used to develop an accurate, practical burst pressure capacity model amenable to the pipeline integrity management practice.

Existing corrosion assessment models were developed and validated under the assumption that internal pressure was the principal driver for burst failure and that longitudinal strain levels were low. The impact of moderate to high levels of longitudinal strain on burst capacity had not been explicitly considered. This paper summarizes work performed as part of a major effort funded by the US Department of Transportation Pipeline and Hazardous Materials Safety Administration (DOT PHMSA) aimed at examining the impact of longitudinal strain on the integrity of pipelines with corrosion anomalies. This paper focuses on the burst pressure of corroded pipes under high longitudinal strains. It is known that longitudinal tensile strain does not reduce the burst pressure relative to that of pipes subjected to low longitudinal strains. Therefore, existing burst pressure models can be considered adequate when the longitudinal strain is tensile. However, longitudinal compressive strain was found to lead to a moderate reduction in burst pressure. Numerical analyses were conducted to study the effect of longitudinal compressive strain on the burst pressure of corroded pipes. A burst pressure reduction formula was developed as a function of the longitudinal compressive strain. Full-scale tests were conducted to confirm the findings of the numerical analysis. Guidelines for assessing the burst pressure of corroded pipes under high longitudinal compressive strains were developed from the outcome of numerical analysis and experimental tests. The guidelines are applicable to different types of corrosion anomalies, including circumferential grooves, longitudinal grooves and general corrosion.

At the forefront of the effort to understand and mitigate pipeline corrosion is the prediction of corrosion growth rates. It is important to understand the effect of corrosion growth estimates on integrity management decisions. An overly conservative approach results in unnecessary digs, while removing conservatism increases the potential for a missed feature to grow to a threatening size. While approaches to feature depth growth have been well-established, there has been less investigation into the growth of feature lengths. A literature review was performed on the methodologies applicable to length growth, and their performance was compared to those that only account for depth growth using a sample analysis. For pipelines with multiple in-line inspection (ILI) runs, feature or signal matching can be used to estimate the change in feature size. These rates can be used directly on individual features, averaged across pipe joints, or compiled into a statistical distribution. Alternatively, only one ILI measurement can be used and an assumption made on the age of the defect. These approaches are more commonly applied to depth growth but could be used to predict length growth as well. To compare the growth methodologies, the study used historical ILI measurements of a liquid pipeline to predict feature sizes and estimated burst pressures determined at the time of the latest ILI. The number of defects correctly predicted to have an insufficient burst pressure safety factor for safe operation was compared to the number of defects that were erroneously predicted to not meet this criterion, and those that were predicted to be safe but later found to not meet the safety factor requirement. The number of erroneously flagged defects was found to vary the most between methodologies. For the assessed data set, using the joint average rate based on feature box-matching was non-conservative on average. It was also found that incorporating length growth did not significantly affect the accuracy of the burst pressure predictions.

In this paper, the burst pressure estimation equations for steam generator tubes with multiple axial surface cracks are proposed based on the local collapse load approach concept. The proposed equations are for a single axial surface crack, two collinear axial surface cracks and two non-aligned axial surface cracks. The proposed equations are validated against experimental tube burst test results and finite element damage analysis for twin cracks. Predicted burst pressures agree well with the experimental results and FE analysis results, suggesting validity of the proposed equations to estimate burst pressures for twin axial surface cracks.

Micro- and multiscale material properties must be considered when manufacturing miniature devices, especially when considering utilizing multiscale sheet metal hydroforming processes. One of the critical considerations during the design process is the burst pressure for the sheet metal which is a limiting factor for potential hydroforming operations. In order to simplify determining tearing or rupture conditions, it is sometimes desired to use analytical methods for estimating material properties, including burst pressures, which occur shortly after material instability. Many researchers have developed approximate methods for predicting deformation during open die hydroforming based upon analytical approaches for biaxial conditions for circular and elliptical dies. Additionally, extracting material properties of sheet metal under biaxial conditions such as bulge hydroforming more closely matches forming conditions that the sheet metal will undergo for actual parts. The objective of the current research was to evaluate the analytically developed models’ ability to predict burst conditions and compare those burst results to those obtained from finite element models and experimentation. Stainless steel (annealed 0.2-mm thick AISI 304) was hydroformed in a circular open die with diameter of 11mm. Elliptical dies were also evaluated that had minor diameters of 11mm and aspect ratios down to 0.5. It was found that using the analytical method developed specifically for circular dies was a good predictor for the burst pressure while the more general analytical method for elliptical dies did not agree with either results from finite element analysis or experimental results.

Boilers and pressure vessels are heavily used in numerous industrial plants, and damaged equipment in the plants is often detected by visual inspection or non-destructive inspection techniques. The most common type of damage is wall thinning due to corrosion under insulation (CUI) or flow-accelerated corrosion (FAC), or both. Any damaged equipment must be repaired or replaced as necessary as soon as possible after damage has been detected. Moreover, optimization of the time required to replace damaged equipment by evaluating the load carrying capacity of boilers and pressure vessels with wall thinning is expected by engineers in the chemical industrial field. In the present study, finite element analysis (FEA) is used to evaluate the load carrying capacity in T-joints with wall thinning. Burst pressure is a measure of the load carrying capacity in T-joints with wall thinning. The T-joints subjected to burst testing are carbon steel tubes for pressure service STPG370 (JIS G3454). The burst pressure is investigated by comparing the results of burst testing with the results of FEA. Moreover, the maximum allowable working pressure (MAWP) of T-joints with wall thinning is calculated, and the safety margin for the burst pressure is investigated. The burst pressure in T-joints with wall thinning can be estimated the safety side using FEA regardless of whether the model is a shell model or a solid model. The MAWP is 2.6 MPa and has a safety margin 7.5 for burst pressure. Moreover, the MAWP is assessed the as a safety side, although the evaluation is too conservative for the burst pressure.

Reinforced thermoplastic pipe (RTP), which basically consists of thermoplastic matrix and reinforced layers, has many advantages such as good flexibility, corrosion resistance and long service life. It has been used in oil and gas transportation pipeline industry for several decades, but generally has either low working pressure or small piping size which limits its application range. Recently, a new type of RTP with high design pressure of 6.9 MPa and large outside diameter of 490 mm was manufactured to substitute traditional metallic piping for long distance oil and gas transportation. In this paper, mechanical properties of such RTP, which is composed of four layers’ cross helically wound steel wires in the middle and two layers’ high density polyethylene (HDPE) inside and outside, are studied. Firstly, a multi-layer model was proposed to analyze the stress-strain relationship for the complex reinforcement structure considering the elasticity of both steel wires and HDPE. Further, an analytical procedure was developed to predict the short-term burst pressure (STBP) of high pressure RTP by taking the nonuniformity of reinforced steel wires into consideration. The practical position and nonuniformity of reinforced steel wires were measured by ultrasonic phased array technique. Then, short-term burst tests were conducted to validate the proposed model. Hoop strains at different internal pressures were measured and a good agreement with theoretical results was obtained, which verifies the effectiveness of the presented model. Finally, some differences of analytical and experimental techniques for STBP between normal RTP and RTP with large diameter and high design pressure were further discussed.

The increasing use of flexible pipes in subsea with high pressure/high temperature brings about much more challenges. Although there has been a simple prediction method for burst pressure, a more comprehensive prediction of the ultimate strength of flexible pipe subjected to internal pressure is essential for the safe use of flexible pipe under complex environments in terms of different failure modes. In this paper, based on the principle of virtual work, a theoretical model for stresses and deformations of the pipe under the short-term internal pressure have been developed and the obtained results have been compared with the ones from the FEM which is used to simulate the pipe under increasing internal pressure using ABAQUS. And the mechanical properties of two kinds of armor layers have been studied comprehensively considering different boundary conditions. The results and FEA models can be useful for the design of flexible pipes. Finally, the failure prediction of a complete model is discussed.Copyright © 2016 by ASME

This study is intended to clarify the influence of jacket-side liquid on determining the burst pressure of a jacketed vessel subjected to deflagrations inside the vessel chamber. The influence of jacket-side liquid is modeled as either being nearly incompressible due to its high bulk modulus or sustaining a constant level of jacket chamber pressure. Employing finite element analyses, this paper reveals how jacket-side liquid compressibility affects the interaction between the vessel shell (inner wall) and jacket (outer wall) when the vessel shell is subjected to an internal deflagration. The study results indicate that simply combing the separate burst pressures of the vessel shell and jacket can result in insignificant difference in calculating the burst pressure of the jacketed vessel that is made of ductile materials and has a relatively small gap between the vessel shell and jacket.Copyright © 2015 by ASME

This paper predicts burst pressures of the steam generator tubes with multiple cracks using finite element (FE) damage analysis. Alloy 690(TT) tube (the outer diameter of 19.05 mm and the thickness of 1.07 mm) widely used in the nuclear power plant is considered in this study. Ductile failure at each element is predicted with the damage model known as ‘multi-axial fracture strain model’ as well as crack propagation is simulated by stress reduction technique in the FE analysis. Simplified ductile damage model for Alloy 690(TT) are determined using tube tensile test data and elastic-plastic FE analysis. FE damage analysis results are sensitive to the element size used in the crack propagation region. Using notched tube fracture test data, proper element size for Alloy 690(TT) is found. Single, collinear, parallel, non-aligned axial-cracks are considered in the simulations and the predicted burst pressures are compared with burst test data.Copyright © 2015 by ASME

For process safety management purposes, it is often required in industries to perform burst pressure calculations for pressurized equipment subjected to internal deflagrations. In predictions of burst pressures of vessels with short cylindrical shell sections, the stiffening effects of heads are often overlooked, which may lead to underestimated results. In this paper, a new improved method is proposed for predictions of burst pressures of thin cylindrical shells with small shell length to diameter ratios (L/D) at ambient temperature. The idea is to use the Svensson’s formula, modified by a factor that accounts for the effects of small L/D ratios, head types, and materials for more accurate predictions. Tables of such factors are developed based on study results from a series of elastic-plastic Finite Element Analyses including large displacement effect for different L/D ratios, thicknesses, materials, and head types. Some example problems are presented to validate the method.Copyright © 2015 by ASME

The ability for deterministic fracture mechanics assessments to correctly estimate the predicted burst pressure (PBP) is dependent upon the accuracy of the model as well as the assumptions made regarding mechanical properties and defect geometry. Within the assessment of defects identified through field investigation or through ILI programs, the use of extreme bounding values for all input variables can lead to unacceptably over-conservative predictions and impede the ability to achieve a target safety margin. This paper examines the effect multiple assumptions have on the bias between predicted and actual burst pressures for various kinds of defects that have caused in-service and hydrostatic pressure test failures in ERW and flash weld line pipe materials. The predicted failure pressures of defects documented within a recent U.S. Department of Transportation compendium of ERW and flash weld seam failures were analyzed using a variety of scenarios based on knowledge of key nominal parameters such as grade, outside diameter, wall thickness, and the maximum defect length and depth. The ratio of the predicted to actual failure pressure was statistically examined across the scenarios for the different defect types. Observations are made regarding the use of the PBP model in order to statistically quantify the accuracy of the model, which can be used as input for an operator to develop a process that achieves a target safety margin.

It is important to validate the accuracy of in-line inspection (ILI) tools to know how many excavations are needed to maintain the integrity of a pipeline segment. Performing sufficient excavations is important to ensure there are no defects left in the pipeline that have even a remote chance of failure. In some cases additional excavations may be necessary to ensure safety where in other cases no excavations may be necessary. This paper looks at using spatially recorded metal-loss data collected “in-the-ditch” to measure the accuracy of ILI tool results. Examples of spatial in-ditch data are laser scans for external corrosion and UT scans for internal corrosion. Spatially mapped metal loss, because all of the corrosion area is mapped, has the advantage of allowing more comparisons to be made for a given corrosion area and also allows the interaction among corrosion pits to be studied for examining burst pressure calculation accuracy. From our studies we find the depth error for shallow corrosion 10%–20% wt deep is often not representative of deeper corrosion in the same pipeline and the interaction criteria for ILI tools needs to be larger than the interaction criteria for in-ditch data. Examples are shown with these types of results, and by interpreting the results in conjunction with API 1163, certain ILI runs are shown that require no excavations where others may require additional excavations than suggested by normal +/−10% wt ILI data.Copyright © 2014 by ASME

Majority of the pipeline operators manage corrosion using inline inspection (ILI). ILIs enable operators to choose which anomalies should be excavated and, on the flip side, which anomalies are safe to remain on the pipe. If the remaining anomalies grow to a critical size before the next ILI cycle there will be in-service failure. This is avoided by forecasting the growth of the measured defects appropriately and assessing them for future integrity. When an ILI is performed on a pipeline the ILI vendor reports the anomaly sizes, burst pressures and the Failure Pressure Ratios for each anomaly. Failure Pressure Ratio (FPR) for an anomaly is defined as the burst pressure divided by the Maximum allowable operation pressure (MAOP). In order to avoid ruptures, operators will excavate anomalies that have a limiting value of FPR. These limiting values are also referred to as response criteria, excavation criteria, safe failure pressure ratios, or safety factors. As the FPR depends heavily on the operating stress (or %SMYS) the limiting FPR value, below which we respond, should also depend on %SMYS. However, currently there is inconsistency in the use of response criteria in the industry. Some utilize the same response criteria for all pipe irrespective of %SMYS. This study shows that using the same limiting FPR does not provide the same level of safety for different %SMYS scenarios. It shows that the size of remaining anomalies in the lower %SMYS pipe would be significantly larger than in higher %SMYS pipe, leading to lower reliability in pipelines that have lower %SMYS. For gas pipelines, these lower %SMYS pipelines are often in higher location class pipelines with higher consequences of failure. In other words, even though the FPR value is the same for two anomalies in two different %SMYS pipes, the two anomalies would have very different probabilities of failure, where one anomaly could be safe while the other is not. This paper examines the ranges of FPR and the safe response criteria as a function of %SMYS. It examines the remaining anomaly sizes in different %SMYS pipe as allowed by current standards. The effect of the uncertainties on the response criteria due to measurement errors, material and geometric properties and model errors are also examined. It examines the response criteria in different jurisdictions. The effect of using different assessment equations, such as Modified B31G or RSTRENG, on the response criteria is also discussed. In order to obtain consistent safety, the consideration of %SMYS and consequences in defining a response criterion is discussed. Many sets of ILI data, which have pipe in different %SMYS, have been assessed in order to examine practical ranges of FPR with %SMYS. The practical implications of different response criteria are studied and discussed.

Bare shipping package containment vessels can be utilized to stage plutonium oxide at the Savannah River Site. Pressurization and subsequent release could occur due to a hypothetical facility fire. Pressurization due to adsorbed moisture on the plutonium oxide and plastic packaging materials could result in rupture of the containment vessel. The containment vessel was evaluated to determine rupture pressure when subjected to the fire conditions. The rupture pressure is compared with pressures developed due to radiolytic gas generation.Copyright © 2014 by ASME

Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions. In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube. From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.

Degraded steam generator tubing can affect its safety functions. Therefore, its integrity should be maintained for each degradation form and all detected degradation must be assessed to verify that if adequate integrity is retained. Determination of tube integrity limits includes identifying acceptable structural parameters such as flaw length, depth, and amplitude of signals. If we consider just single-cracked tubes, short and deep flaws are not likely to threaten structural integrity of tubes. But if it has multiple-cracks, we have to consider interaction effects of multiple adjacent cracks on its burst pressure. Because adjacent multiple cracks can be merged due to the crack growth then it can challenge against the structural performance limit. There are some studies on the interaction effects of adjacent cracks. However, existing works on the interaction effect consider only through-wall cracks. No study has been carried out on the interaction effects of part-through cracks. Most cracks existing in real steam generator tubing are not through-wall cracks but part-through cracks. Hence, integrity of part-through cracks is more practical issue than that of through-wall cracks. This paper presents experimental burst test results with steam generator tubing for evaluation of interaction effects with axial oriented two collinear and parallel part-through cracks. The interaction effect between two adjacent cracks disappeared when the distance exceeds about 2 mm.

Fitness-For-Service (FFS) assessment using Finite Element Analysis (FEA) has been a problem in deciding yes-no which vary from evaluator to evaluator. The difference in decision making is caused by the degree of freedom in modeling a FEA model. In this study, burst pressures of pipes with local metal loss were calculated by using FEA in order to investigate the influence of thickness measurement intervals on FFS assessment. The analyzed pressures by FEA were verified by burst tests. A pipe specimen, which was thinned by corrosion under insulation in the actual plant, was used for the burst tests. Shape of the pipe specimen was measured by laser displacement meter and extracted at several types of interval. It is concluded that the analyzed pressures in various measurement intervals showed almost no difference, but were higher than the actual burst pressure of the specimen.Copyright © 2013 by ASME

Boilers and pressure vessels are heavily used in chemical industrial plants and equipment is inspected periodically for damage. The most common type of damage is wall thinning due to Flow-Accelerated Corrosion (FAC) or corrosion under insulation (CUI). Any damage must be repaired or replaced as necessary. On the other hand, optimization of the time required in order to replace damaged equipment by evaluating the load carrying capacity of pipes with wall thinning is expected in chemical industrial field. In the present study, FE analysis is used in order to evaluate the load carrying capacity in pipes with wall thinning. Burst pressure is a measure of the load carrying capacity in pipes with wall thinning. The pipes subjected to burst testing are carbon steel tubes for pressure service STPG370 (JIS G3454). The examined wall thinning is rectangular, and the eroded depth is half the pipe wall thickness. The burst pressure is investigated by comparing the results of burst testing with the results of FE analysis. Moreover, the reduced maximum allowable working pressure (MAWPr), which is calculated by fitness-for-service (FFS) assessment, and the safety margin for burst pressure are investigated. The burst pressure calculated by FEA agrees well with the test results, except for square wall thinning for circumferential angles of less than 15°. Also, the safety margin of MAWPr based on FFS-1 Part 4 is over 4.0 times for burst pressure.Copyright © 2013 by ASME

Gas pipelines with mechanical damages could affect the structural integrity and causes local stress and strain concentration. Failures in gas pipeline as leakages that could affect the supply of gas, loss of production, and environmental pollution. It is important to determine if pipelines are fitness-for-service. ASME B31G code is still widely used criterion although the assessment method is the conservative method. Further examinations are needed on the effects of material grade and pipeline shape on the burst pressure of damaged pipelines. The goal of this paper is to predict the failure pressure of mechanical damaged made of API X65 and X70 pipelines, by conducting full scale burst tests and finite element analysis (FEA). Different pipeline grades, effects of gouges, and dent depths were considered for an integrity assessment. The full scale burst tests were performed for pipelines with artificial mechanical damage. The gouge defect was made in a V-notch shape and the dented pipeline was generated using a ball shaped indenter that was pressed into the pipe. A three dimensional FEA was performed to obtain the burst pressure of a pipe with gouge and dent defects as a function of defect depth and length. A FEA was used to simulate the and externally damaged pipes under internal pressure. Failure pressure was predicted with stress based and strain based assessments by the finite element method (FEM).

In-Line Inspection (ILI) is used to prioritize metal loss conditions based on predicted failure pressure in accordance with methods prescribed in industry standards such as ASME B31G-2009. Corrosion may occur in multiple areas of metal loss that interact and may result in a lower failure pressure than if flaws were analyzed separately. The B31G standard recommends a flaw interaction criterion for ILI metal loss predictions within a longitudinal and circumferential spacing of 3 times wall thickness, but cautions that methods employed for clustering of ILI anomalies should be validated with results from direct measurements in the ditch. Recent advances in non-destructive examination (NDE) and data correlation software have enabled reliable comparisons of ILI burst pressure predictions with the results from in-ditch examination. Data correlation using pattern matching algorithms allows the consideration of detection and reporting thresholds for both ILI and field measurements, and determination of error in the calculated failure pressure prediction attributable to the flaw interaction criterion. This paper presents a case study of magnetic flux leakage ILI failure pressure predictions compared with field results obtained during excavations. The effect of interaction criterion on calculated failure pressure and the probability of an ILI measurement underestimating failure pressure have been studied. We concluded a reason failure pressure specifications do not exist for ILI measurements is because of the variety of possible interaction criteria and data thresholds that can be employed, and demonstrate herein a method for their validation.Copyright © 2012 by ASME

Plastic collapse analysis and remaining burst strength determination are critical to a corroded pipeline in its fitness-for-service analysis and integrity assessment. For very long corrosion defects, the present authors proposed a theoretical solution for predicting the burst pressure of corroded pipe in terms of a newly developed average shear stress yield theory, and validated it using full-scale burst data for long real corrosion defects. This paper then presents a finite element analysis (FEA) procedure to determine the remaining burst pressure for a very long blunt defect. A burst failure criterion that is referred to as von Mises equivalent stress criterion is proposed first in reference to the von Mises theory. Detailed elastic-plastic FEA calculations are performed using ABAQUS for a series of corroded pipes with infinitely long defects in different widths. From the FEA results and using the proposed failure criterion, the numerical results of burst pressure are determined for the long defects. The results show that using the proposed failure criterion, the FEA simulation can accurately determine the burst pressure for corroded pipes with long defects that is consistent with the theoretical solution. The conventional assessment methods including ASME B31G, RSTRENG, PCORRC and LPC are also evaluated and discussed in comparison with the proposed theoretical solution of burst pressure for long corrosion defects.

T-pipe is one of the typical structural elements of LWR piping as well as T-joint. In the present situation, the evaluation of wall thinning for T-pipe is accomplished by assuring the sufficient strength around the opening area by using the design and construction code. This evaluation often assumes the replacement of a local wall thinning with a global wall thinning, which leads to excessively conservative prediction of burst pressures. In this study, three-dimensional finite element analysis was conducted to simulate the fracture behavior of a pressurized T-pipe test. The accuracy of the predicted burst pressures and appropriate modeling of the welded joint at the junction of the main and branch pipes were investigated. It was found that the burst pressure could be adequately predicted by applying a proper fracture criterion. Allocation of experimental tensile property of weld metal to the welded joint gave more accurate prediction; nevertheless, allocation of experimental tensile property of base metal to the welded joint enabled suitably conservative prediction.Copyright © 2012 by ASME

Tissue fusion is a method of joining tissue using heat and pressure. Several surgical tool companies have developed devices which perform tissue fusion on blood vessels in order to perform ligation of the vessel [1]. The success or failure of these devices is contingent upon the strength of the bond it creates between opposing sides of the blood vessel lumen, yet little characterization has been done to measure the strength of this interface. Previous studies have examined the strength of tissue fusion using clinically relevant metrics such as burst pressure or tearing strength, but none have explored metrics more appropriate for determining the mechanics of the actual bond, such as peel strength or shear strength [2–3]. These clinical metrics are susceptible to large variations due to tissue composition and geometry. The goal of this study is to measure the bond’s modulus and strength using standard engineering methods. The motivation of the present work is to develop a method for quantitatively measuring the strength of the bond made during tissue fusion. This method can then be applied to quantify the strength of the fusion interface between arterial tissue using other devices and aid in future evaluation and development of tissue fusion devices to maximize the bond strength.Copyright © 2012 by ASME

It is common to assess corroded line pipe using ASME B31-G, its Canadian equivalent CSA Z662 Clause 10.8.2, or more recently RSTRENG. These techniques consider only the circumferential stress in the pipe in predicting the burst pressure of corroded pipe. This paper describes the results of experiments and finite element modeling to investigate the effect of longitudinal stress on the burst pressure of pipe with isolated corrosion pits. The results are used to develop a correction factor applicable to the assessment procedures listed above.Copyright © 1998 by ASME