Failure Pressure Research Articles

Influence of Casing Eccentricity on the Mechanical Integrity of Cement Sheaths in Fractured Wells.

During the fracturing process of oil and gas wells, casing eccentricity directly affects the mechanical integrity of cement sheaths, but the law and degree of influence are not clear at present, and there are no measures to address the influence of casing eccentricity on the mechanical integrity of cement sheaths. This paper took the lead in developing a set of experimental devices for cement sheath integrity. A comparative experimental study on the mechanical integrity of cement sheaths was carried out for the first time under casing concentric and eccentric conditions, and the influence of casing eccentricity on the mechanical integrity of cement sheaths in fractured wells of the Wushi 17-2 oilfield was also investigated. The numerical simulation method was used to perform stress analysis on cement sheaths of fractured wells under casing concentric and eccentric conditions. The influences of casing wall thickness, cement sheath thickness, the elastic modulus of cement sheath, and formation on radial stress of the cement sheath were analyzed, and the mechanical integrity safeguard or remedy measures of the cement sheath under the casing eccentric condition were proposed for the first time. The results show that casing eccentricity can easily lead to stress concentration at the narrow edge of the cement sheath. Under the condition of the same strength of the cement sheath, the integrity of the cement sheath is more likely to fail under the casing eccentric condition. The tensile failure cracks are concentrated at the narrow edge of the cement sheath. With the increase in casing eccentricity, the stress at the narrow edge of the cement sheath increased, the critical failure pressure of the cement sheath decreased, and the failure pressure of cement sheath integrity decreased by 17.72% at a casing eccentricity of 33% compared within a casing eccentricity of 0%. Improving the casing center degree, increasing the casing wall thickness and cement sheath thickness, and reducing the elastic modulus of the cement sheath can minimize the stress of the cement sheath and prevent mechanical integrity failure. This study is helpful to evaluate the mechanical integrity of the cement sheath in fractured wells accurately and can provide a technical reference for optimizing the casing center degree.

Study on hazards from high-pressure on-board type III hydrogen tank in fire scenario: Consequences and response behaviours

Exploration of thermal performances of composite high-pressure hydrogen storage tank under fire exposure were critical issues to reduce the risk of tank rupture. Three bonfire tests of type III tanks of 210 L-35 MPa with full compressed hydrogen were exposed to a pool fire to study the response behaviours in fire scenarios. Detailed data on the tank wall temperature and inner pressure were presented in this work. Prototype bonfire tests for the type III tank indicated the failure pressure limits amounted to 41.1–41.8 MPa (average 41.4 MPa). Two consequences (rupture and hydrogen blowdown) will be caused when the inner pressure beyond this limits in fire scenario. The loading-bearing capacity of the tank reduced nearly 3 times under the prescribed fire condition when compared to its average burst pressure of 123.5 MPa conducted from the hydraulic burst test. Results also shown that fire resistance rating (FRR, time to rupture) of the three tanks were 784, 666, and 596, respectively. The FRR got shorter when the tank was exposed in the engulfing fire in advance at hydrogen blowdown case.

Multiresolution analysis and deep learning for corroded pipeline failure assessment

The assessment of the safety of corroded pipelines is considered a vital task in the oil and gas industry. This research aims to develop an efficient system to accurately predict the burst pressure of corroded pipelines with complex corrosion profiles through hybrid models using multiresolution analysis, numerical analysis and meta-models. The work addresses the parametrization of real corrosion shapes and its use as input to a neural network system that can predict the burst pressure accurately and quickly. Ultrasonic inspections provide the thicknesses in the corrosion area and with that data the river-bottom profile (rbp) can be constructed. A set of scripts creates finite element models from the rbp, which are then subjected to non-linear analyses to determine the failure pressure. In this work, the Finite Element models and analysis procedure are validated against experimental tests and are compared to semi-empirical assessment methods. A discrete wavelet transform is performed for the parametrization of the remaining thicknesses and it is used as a filter bank to reduce the amount of data that describes the defect. The coefficients obtained from the wavelet transform are used as inputs to feed a neural network to provide a quick evaluation of the failure pressure. This neural network is trained with the results of finite element analyses performed on synthetic models built with statistical properties similar to those of real corrosion defects The results from the neural networks are obtained very fast and accurate for all cases presented in this work.

Estimation of Burst Pressure of PVC Pipe Using Average Shear Stress Yield Criterion: Experimental and Numerical Studies

Polyvinyl chloride (PVC) pipes have been extensively applied in water supply network fields. Understanding the mechanical properties and burst pressure of PVC pipes is necessary because a large number of pipes rupture due to excessive internal water pressure. In this paper, a practical approach based on the average shear stress yield (ASSY) criterion was proposed to assess the PVC pipe burst pressure. In addition, the PVC uniaxial tensile tests and the pipe burst tests were carried out to determine the material characteristic parameters and burst pressure of the PVC pipe. Furthermore, a finite element analysis (FEA) of PVC burst pressure was also performed based on the tangent intersection (TI) method to validate the proposed method and experimental results. Moreover, the impact of material parameters and pipe size, such as the strain hardening exponent and standard dimension ratio (SDR) on bursting pressure, were investigated. The comparison with the proposed theoretical model and the experimental and FEA results shows that the burst pressure derived from ASSY was consistent with the experimental data, with a relative error ranging from −2.76% to 2.65%, which is more accurate compared to other yield criteria. The burst pressure obtained by the ASSY approach declined with the increase of the hardening exponent n and increased with the increase of SDR. Therefore, the burst pressure solution-based ASSY proposed in this paper is an adequately suitable and precise predictive tool for assessing the failure pressure of PVC pipes.

Effect of statistical scatter in the elastic properties on the predictability of first ply failure of a polymer composite pressure vessel

Statistical variations in the elastic properties of composites are unavoidable. This work is concerned with the assessment of the probabilistic first ply failure of pressure vessel in response to the variations of elastic properties of T700 carbon/epoxy composite among the published literature. Initially, deterministic failure pressure is estimated using Finite Element Analysis software ANSYS. The uncertainties with respect to elastic properties are quantified by using Statistical software MINITAB. Then, the probability design system platform in ANSYS software has been utilized to perform probabilistic failure analysis by Monte Carlo simulations. The statistical results in terms of the mean and standard deviation of first ply failure pressure are computed. The probabilistic first ply failure pressure range determined is within 3 limits with 99.997% confidence level. It is helpful to the designers to assess the factor of safety in the case of anticipated variations in properties.

Mineralocorticoid receptor antagonists use in patients with heart failure and impaired renal function.

AimsImpaired renal function is a major contributor to the low proportion of mineralocorticoid receptor antagonist (MRA) treatment in patients with heart failure with reduced ejection fraction (HFrEF). Our aims were to investigate the impact of MRA treatment on all-cause mortality and worsening renal function (WRF) in patients with HFrEF and moderately impaired renal function.MethodsRetrospective data between 2010–2018 on HFrEF patients from a single-centre hospital with estimated glomerular renal function (eGFR) < 60 ml/min/1.73 m2 were analysed. WRF was defined as a decline of by eGFR ≥ 20%.Results416 patients were included, 131 patients on MRA and 285 without MRA, mean age was 77 years (SD ± 9) and 82 years (SD ± 9), respectively. Median follow-up was 2 years. 128 patients (32%) experienced WRF, 25% in the MRA group and 30% in patients without MRA (p = 0.293). In multivariable analysis, hospitalization for heart failure and systolic blood pressure were associated with WRF (p = 0.015 and p = <0.001), but not use of MRA (p = 0.421). MRA treatment had no impact on the risk of adjusted all-cause mortality (HR 0.93; 95% CI, 0.66–1.32 p = 0.685). WRF was associated with increased adjusted risk of all-cause mortality (HR 1.43; 95% CI, 1.07–1.89 p = 0.014). Use of MRA did not increase the adjusted overall risk of mortality even when experiencing WRF (HR 1.15; 95% CI, 0.81–1.63 p = 0.422).ConclusionIn this cohort of elderly HFrEF patients with moderately impaired renal function, MRA did not increase risk for WRF or all-cause mortality.

Visual echocardiographic scoring system of the left ventricular filling pressure and outcomes of heart failure with preserved ejection fraction.

AimsElevated left ventricular filling pressure (LVFP) is a powerful indicator of worsening clinical outcomes in heart failure with preserved ejection fraction (HFpEF); however, detection of elevated LVFP is often challenging. This study aimed to determine the association between the newly proposed echocardiographic LVFP parameter, visually assessed time difference between the mitral valve and tricuspid valve opening (VMT) score, and clinical outcomes of HFpEF.Methods and resultsWe retrospectively investigated 310 well-differentiated HFpEF patients in stable conditions. VMT was scored from 0 to 3 using two-dimensional echocardiographic images, and VMT ≥2 was regarded as a sign of elevated LVFP. The primary endpoint was a composite of cardiac death or heart failure hospitalization during the 2 years after the echocardiographic examination. In all patients, Kaplan–Meier curves showed that VMT ≥2 (n = 54) was associated with worse outcomes than the VMT ≤1 group (n = 256) (P < 0.001). Furthermore, VMT ≥2 was associated with worse outcomes when tested in 100 HFpEF patients with atrial fibrillation (AF) (P = 0.026). In the adjusted model, VMT ≥2 was independently associated with the primary outcome (hazard ratio 2.60, 95% confidence interval 1.46–4.61; P = 0.001). Additionally, VMT scoring provided an incremental prognostic value over clinically relevant variables and diastolic function grading (χ2 10.8–16.3, P = 0.035).ConclusionsIn patients with HFpEF, the VMT score was independently and incrementally associated with adverse clinical outcomes. Moreover, it could also predict clinical outcomes in HFpEF patients with AF.

Stochastic analysis of failure pressure in reinforced thermoplastic pipes under axial loading and external pressure

Reinforced thermoplastic pipes (RTPs) are flexible composite pipes that are acknowledged as a good alternative to conventional submarine pipes. This study aims at investigating the impact of the uncertainties involved in the production process of the RTPs on the failure pressure under combined loading conditions. The stress distributions of RTPs were analyzed using the theory of the three-dimensional (3D) thick-walled cylinder method, combined with the homogenization method. Based on these results, to evaluate the failure mechanisms of RTPs, the 3D Hashin–Yeh failure criterion and the damage evolution model were adopted to establish a progressive failure model. For analyzing the influence of randomness of the related parameters on the first-ply failure (FPF) pressure as well as the final burst failure (FF) pressure of RTPs, a sufficient number of samples were generated using the Monte-Carlo method. Results of the stochastic analysis were validated using the hydraulic burst test data. The statistical evaluation of the stochastic analysis results was performed by using the Weibull probability density distribution function, and the results showed an increase in the probability of getting a lower failure pressure of RTPs than the average failure pressure (considering the randomness of production parameters).

A Review of Finite Element Analysis and Artificial Neural Networks as Failure Pressure Prediction Tools for Corroded Pipelines.

This paper discusses the capabilities of artificial neural networks (ANNs) when integrated with the finite element method (FEM) and utilized as prediction tools to predict the failure pressure of corroded pipelines. The use of conventional residual strength assessment methods has proven to produce predictions that are conservative, and this, in turn, costs companies by leading to premature maintenance and replacement. ANNs and FEM have proven to be strong failure pressure prediction tools, and they are being utilized to replace the time-consuming methods and conventional codes. FEM is widely used to evaluate the structural integrity of corroded pipelines, and the integration of ANNs into this process greatly reduces the time taken to obtain accurate results.

An Empirical Equation for Failure Pressure Prediction of High Toughness Pipeline with Interacting Corrosion Defects Subjected to Combined Loadings Based on Artificial Neural Network

Conventional pipeline corrosion assessment methods for failure pressure prediction do not account for interacting defects subjected to internal pressure and axial compressive stress. In any case, the failure pressure predictions are conservative. As such, numerical methods are required. This paper proposes an alternative to the computationally expensive numerical methods, specifically an empirical equation based on Finite Element Analysis (FEA). FEA was conducted to generate training data for an ANN after validating the method against full scale burst test results from past research. An ANN with four inputs and one output was developed. The equation was developed based on the weights and biases of an ANN model trained with failure pressure from the FEA of a high toughness pipeline for various defect spacings, defect depths, defect lengths, and axial compressive stresses. The proposed model was validated against actual burst test results for high toughness materials, with a R2 value of 0.99. Extensive parametric study was subsequently conducted to determine the effects of defect spacing, defect length, defect depth, and axial compressive stress on the failure pressure of the pipe. The results of the empirical equation are comparable to the results from numerical methods for the pipes and loadings considered in this study.

MANUFACTURING OF SANDWICH PANELS AND ITS VERIFICATION BY NUMERICAL SIMULATION

This paper deals with the manufacturing of a parallel hydroformed sandwich panel, which is used as a reinforcement for solar panels. The forming process can cause excessive thinning and cracking. Therefore, PAM-STAMP software is used for the analysis of defects. The outputs of the numerical simulation provide information, such as failure pressure, critical areas or limiting deformations. The comparison of the numerical simulation with the experimentally obtained data is created for the validation of these outputs. The comparative criteria are the failure pressure, the crack zone, and the thickness distribution. Subsequently, the results can be used for a design optimization of the sandwich panel.

Evaluation of the Creep Rupture Behavior of Alloy 690 Steam Generator Tubes Considering the Pressure Ramp Rate

Abstract Steam generator tubes are among the main components that form the pressure boundary of a nuclear power plant and studies of ruptures of steam generator (SG) tubes are important because they can ensure the safety of a nuclear power plant in case of a severe accident. The materials used previously for SG tubes around the world have been replaced and will be replaced by Alloy 690 given its improved corrosion resistance relative to that of Alloy 600. However, studies of the high-temperature creep and creep-rupture characteristics of SG tubes made of Alloy 690 are insufficient compared to those focusing on Alloy 600. In this study, several creep tests were conducted using half-tube shape specimens of the Alloy 690 material at temperatures ranging from 650 °C to 850 °C and stresses in the range of 30–350 MPa, with failure times to creep rupture ranging from 3 h to 870 h. Based on the creep test results, creep life predictions were then made using the well-known Larson–Miller parameter (LMP) method. Steam generator tube rupture tests were also conducted under the conditions of a constant temperature and pressure ramp using SG tube specimens. As the pressure ramp rate increases, the failure behavior changes due to the rapid change in strain near the crack tip. The rupture test equipment was designed and manufactured to simulate the transient state (rapid temperature and pressure changes) in the event of a severe accident condition. After the rupture test, the damage to the SG tubes was predicted using a creep rupture model and a flow stress model. A modified creep rupture model for Alloy 690 SG tube material is proposed based on the experimental results. A correction factor of 1.7 in the modified creep rupture model was derived for the Alloy 690 material. The predicted failure pressure was in good agreement with the experimental failure pressure.

The Impact of Glucocorticoid Therapy on Guideline-Directed Medical Treatment Titration in Patients Hospitalized for Heart Failure with Low Blood Pressure: A Retrospective Study.

BackgroundPositive inotropic and renal protective actions of glucocorticoids have been observed clinically. Therefore, glucocorticoids may be used in patients with heart failure and low blood pressure (HF-LBP).MethodsThe medical records of 144 consecutive patients with HF-LBP who received glucocorticoids as an adjunctive treatment to facilitate the up-titration of β-blocker and angiotensin-converting enzyme inhibitor were reviewed.ResultsAfter four weeks of treatment, the metoprolol and captopril (or equivalent) dosages were progressively and consistently increased from 25 (interquartile range [IQR] = 12.5–75 mg/day) to 100 mg/day (IQR = 50–178.8 mg/day) and from 0 (IQR = 0–25 mg/day) to 12.5 mg/day (IQR = 0–50 mg/day), respectively. There was a remarkable beneficial hemodynamic response to the glucocorticoid treatment signified by an increase in blood pressure and decrease in heart rate. The average heart rate decreased by 6 beat per minute (bpm) (0.5–16 bpm), and the mean arterial blood pressure increased from 74.06 ± 7.81 to 78.85 ± 7.91 mmHg. We also observed an improvement in renal function and an increased diuretic response following glucocorticoid treatment. As a result, the left ventricular ejection fraction increased from 28.92 ± 8.06% to 33.86 ± 8.76%, and the diuretic response increased from 776.7 mL/40 mg furosemide (IQR = 133.8–2000 mL) to 4000 mL/40 mg furosemide on day 28 (IQR = 2200–5925 mL).ConclusionThe use of glucocorticoid treatment to maintain hemodynamic and renal functional targets when titrating guideline-directed medical treatment in patients with HF-LBP may be safe, effective, and feasible.

Effect of autofrettage on the ultimate behavior of thick cylindrical pressure vessels

Major applications of thick cylinders are in the defense sector. Stress distributions especially under elastic-plastic conditions are more complex in thick cylinders. Though the cylinder may not be strained to ultimate in service, assessment of factor of safety is essential. Simulating elastic-plastic material behavior of cylinders using the uni-axial test data is more dependable and the finite element analysis (FEA) software has got this capability. A procedure using a suitable material model is demonstrated in this study utilizing the FEA software Ansys. The instability criterion followed in Svensson's pressure expansion relationship is used in the process of FEA. The predicted failure pressure is very close to the literature test data as well as few theories that have been highlighted. Moreover, thick cylinders are mostly subjected to autofrettage in applications like gun barrels to enhance service pressure and fatigue life. Hence it is attempted to simulate the development of residual stress due to autofrettage and its effect on the ultimate behavior on the pressure vessels. The residual stress developed is superimposed on the stresses due to internal pressure which causes the redistribution of stresses throughout the thickness. There is a marginal increase in burst pressure due to autofrettage. Though the effect could be made significant by increasing the autofrettage pressure, it gives detrimental effects on the other side by developing tensile residual stresses on the external surface. Hence, with the permissible extent of autofrettage, the effects are found to be marginal and this knowledge helps assess the safe loading limits.

An assessment of the structural relationship between determinants and implications of caste‐based endogamy in Pakistan

AbstractThis study aims to examine the socio‐economic determinants and implications of caste‐based endogamy in Punjab, the largest province of Pakistan. It also measures the structural relationship between determinants and implications of endogamy. For this cross‐sectional study, 488 respondents were randomly selected from three Punjab province districts with inclusion criteria of being married within their caste. A path modelling and multigroup analysis were conducted using partial least squares structural equation modelling (PLS‐SEM). This study has found that social pressure, casteism, and fear of exogamy failure significantly influence mate selection in Punjab, which has socio‐economic implications. Social pressure and perceived easiness of endogamy less likely contribute towards economic implications. Similarly, casteism indicated a non‐significant influence on social implications. Overall, male and female respondents shared views on endogamy influencing determinants causing socio‐economic implications. This study concludes that caste‐based endogamy has a stronghold in the cultural patterns of Punjab, Pakistan, which restricts economic mobility, deepens the marginalisation of those from lower castes, and promotes casteism at community and institutional levels. This is one of the initial studies in Pakistani Punjab assessing the structural relationship between endogamy determinants and their social and economic implications.

Randomized experimental study of two novel techniques for transanal repair of dehiscent low rectal anastomosis.

Anastomotic leak after low anterior rectal resection is a dreadful complication. Early diagnosis, prompt management of sepsis followed by closure of anastomotic defect may increase chances of anastomotic salvage. In this randomized experimental study, we evaluated two different methods of trans-anal anastomotic repair. A model of anastomotic leak was created in 42 male pigs. Laparoscopic low anterior resection was performed with anastomosis created using a circular stapler with half of the staples removed. Two days later, animals were randomized into a TAMIS (trans-anal minimally invasive surgery) repair, endoscopic suture (ENDO) or control group with no treatment (CONTROL). Signs of intraabdominal infection (IAI), macroscopic anastomotic healing and burst tests were evaluated to assess closure quality after animals were sacrificed on the ninth postoperative day. Closure was technically feasible in all 28 animals. Two animals had to be euthanized due to progressive sepsis at four and five days after endoscopic closure. Healed anastomosis with no visible defect was observed in 10/14 and 11/14 animals in TAMIS and ENDO groups, respectively, versus 2/14 in CONTROL (p < 0.05). Overall IAI rate was significantly lower in TAMIS (4/14; p = 0.006) and ENDO (5/14; p = 0.018) compared to CONTROL (12/14). Burst tests confirmed sealed closure in healed anastomosis with a median failure pressure of 190 (110-300) mmHg in TAMIS and 200 (100-300) mmHg in ENDO group (p = 0.644). In this randomized experimental study, we found that both evaluated techniques are effective in early repair of dehiscent colorectal anastomosis with a high healing rate.

Initiation mechanisms of radial drilling‐fracturing considering shale hydration and reservoir dip

AbstractRadial drilling‐fracturing is an innovative fracturing technology that achieves superior stimulation effects. This paper develops a model for radial drilling‐fracturing in shale reservoirs, which can predict fracture initiation pressure and failure mode of shale. Compared with published models, this model additionally considers shale hydration and inclinations of boreholes and reservoir. Then, the influences of 7 factors are studied and main conclusions are as follows. First, with the angle between radial borehole and formation strike increasing, matrix failure pressure declines only around 90° and 270°. Bedding tensile failure pressure ascends and then falls back. Bedding shear failure pressure rapidly descends, then reaches a plateau, and finally rebounds. A small or large angle is favorable for bedding tensile failure. Shale tends to crack with bedding shear failure under a moderate angle and with matrix failure only at 90° and 270°. Second, with the enlargement of azimuth difference between the radial borehole and main wellbore, matrix failure pressure periodically fluctuates, forming an inverted W‐shape curve. Bedding tensile failure pressure and bedding shear failure pressure both ascend, then slide downward, and finally rise again. Besides, a small azimuth difference inclines shale to bedding shear failure, and the other failure modes tend to occur when azimuth difference is around 90°. Third, pressures required for all failure modes descend as the dip of shale formation increases. However, the difference in descending rate leads to that the increase of dip angle can incline shale to bedding shear failure. Besides, pressures required for bedding tensile failure and matrix failure decline linearly with the increasing reservoir temperature. Temperature has no impact on bedding shear failure. Hence, matrix failure and bedding tensile failure are more prone to occur in the high‐temperature reservoir. The research provides a reference for field applications of radial drilling‐fracturing in the shale reservoir.

Fast and accurate prediction of failure pressure of oil and gas defective pipelines using the deep learning model

Determining the failure pressure of defective pipelines is an important part in pipeline reliability engineering, which affects the assessment of pipelines residual service life. In this work, a fast and accurate method for predicting the failure pressure of defective pipelines using the deep learning model is developed. The calculation results of ASME-B31GM, DNV, PCORRC codes and finite element method (FEM) are compared and analyzed in detail to obtain high-quality sample data. 150 groups of validated FEM simulation data and 142 groups of burst pressure test data are selected for the training and validation of deep learning model. In the training process, influences of key model parameters of deep neural network (DNN) on the prediction accuracy are investigated. Prediction results indicate that the used deep learning model can offer high prediction accuracy. In addition, the calculation of deep learning model is accelerated by at least two orders of magnitude compared with that of FEM simulations under same calculation conditions. Finally, the influence of defect sizes on pipeline failure pressure is analyzed by the DNN. This work is expected to shed a light on efficient and accurate predictions of failure pressure of oil and gas defective pipelines.

General corrosion vulnerability assessment using a Bayesian belief network model incorporating experimental corrosion data for X60 pipe steel

External corrosion is one of the leading causes of pipe failure in the oil and gas industry. In this study, a Bayesian belief network (BBN) model has been developed using corrosion rate (CR) data obtained from experimental test results and analytical burst failure models. The BBN model for CR was coupled with a time marching simulation to obtain corrosion defects and quantify failure pressure capacity. Finally, in a reliability framework, the failure pressure capacity was coupled with operating pressure to obtain the probability of failure. Furthermore, the developed BBN model was used to perform a parametric study to identify the critical parameters for the CR. The outcome of the study indicated that the proposed BBN model can be useful to integrate experimental and analytical models to derive reliability of a pipeline operating under various conditions.

Further development of the gamma exponent model for assessment of flaws in oil and gas pipelines

The Gamma Exponent Model (“GEM”) is a recently developed methodology for failure pressure prediction of flaws in oil and gas pipelines. The model has previously demonstrated applicability for the assessment of axial surface breaking (or “part wall”) cracks and localized metal loss/corrosion. This work extends the applicability of the model to circumferential surface cracks. In addition, the GEM is shown to be consistent and complementary to the log-secant model for assessment of axial through wall cracks, developed by the NG18 Committee of the Battelle Institute in the early 1970s. The ongoing development of the GEM raises some important theoretical considerations related to understanding of the stress state at the flaw tip during the failure process. The current industry models are not explicit regarding the plane stress or plane strain conditions at the flaw tip, though this has a significant effect on model development. Analysts often assume plane stress conditions, due to oil and gas pipelines typically being considered “thin wall” pipe. However, this work confirms the theory that surface cracks are subject to plane strain conditions, and the selection of fracture toughness correlations from impact energy data becomes very important. The model is validated against available laboratory, hydrotest and in-service failure data. Statistical analyses demonstrate the mathematical form of the new model is valid. Failure pressure predictions are shown to be improved over current industry models. This can have a significant effect on the reliability pipeline integrity programs and improved efficiency in the form of cost savings.