bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Behaviors of Reinforced Thermoplastic Pipe Under Combined Load
Authors: Wang Baodong , Zhang Hong , Liu Xiaoben
Published: November 2019

Reinforced thermoplastic pipe (RTP) is used in the oil and gas industry for its good flexibility, corrosion resistance and wear resistance, especially in offshore oil and gas production process. However, they are subject to internal pressure, external pressure and tension loads that are important aspects affecting the integrity and security of the flexible pipe. Their reinforced layers are designed for bearing internal pressure and tension. In this paper, the mechanical behaviors of reinforced thermoplastic pipe with 3 layers, where the reinforced layer is aramid fiber braid layers, is investigated by numerical methods. The internal pressure burst test of reinforced thermoplastic pipes was carried out to determine the burst internal pressure and failure behaviors of RTP. A finite element model that considers the material nonlinearity as well as the friction interactions between layers was created using ABAQUS. The mechanical behavior of reinforced flexible pipe subjected to internal pressure and tension load as well as its failure model was investigated in detail. Effects of the braided angle of aramid fiber braid layers were elucidated. This study can be referenced for the applications of reinforced thermoplastic pipe in marine oil and gas production.
A Calculation Method of the Load Factor and Design for Bolted Gasketed Pipe Flange Connections Under Internal Pressure
Authors: Sawa Toshiyuki , Mabuchi Toshio , Sato Koji
Published: November 2019

The contact gasket stress reduces when the bolted gasketed pipe flange connections are subjected to internal pressure. In designing the bolted connections, it is needed to predict the reduced contact gasket stress, so, it is necessary to know the load factor. However, it is difficult to estimate the value of the load factor of the connections under internal pressure. In the previous paper (2018PVP), a more simpler calculation method was proposed. However, a more accuracy for obtaining the values of the load factor is desirable using the spring constants Ktg and Kcg. In the present paper, some calculation models for the spring constants are improved. Then, the values of the load factor for JIS 10K flange connections and ASME B16 flange connections with spiral wound gaskets are shown. The values of the load factor for the above connections are in a fairy good agreement with the FEM results. Using the obtained load factor, the residual contact gasket stress and an amount of gas leakage are predicted. The obtained calculated results of the load factor and the amount of the leakage are in a fairly good agreement with FEM results, and the measured results for 24” connection. As a result, the value of the load factor for the connections with larger nominal diameter is found to be negative and it decreases as the nominal flange diameter increases. In addition, a method how to determine the bolt preload for satisfying a give allowable leak rate is demonstrated.
Evaluation of Irradiation Embrittlement of the Chinese RPV Steels
Authors: Cao Yupeng , He Yinbiao , Wang Binxi , Huang Yifeng , Li Hui , Yu Yan , Hui Hu
Published: November 2019

Reactor pressure vessel (RPV) is considered to be irreplaceable, which is the most limiting factor for the lifetime of a nuclear power plant. This paper aims to introduce our project for the evaluation of the irradiation embrittlement for the Chinese RPV forging. The forging manufactured in China was irradiated in the high fluence engineering test reactor. Tensile tests, Charpy impact tests and fracture toughness tests in terms of master curve T0 were carried out for the material subjected to different irradiation fluences. Comparison of the mechanical properties of the irradiated materials and the materials without irradiation is made. The irradiation resistance of the materials in our project is also compared with the data for the irradiated RPV steels in the literatures.
Modeling Shock and Vibration on Used Nuclear Fuel During Normal Conditions of Transportation
Authors: Klymyshyn Nicholas , Ivanusa Pavlo , Kadooka Kevin , Spitz Casey
Published: November 2019

In 2017, the United States Department of Energy (DOE) collaborated with Spanish and Korean organizations to perform a multimodal transportation test to measure shock and vibration loads imparted to used nuclear fuel (UNF) assemblies. This test used real fuel assembly components containing surrogate fuel mass to approximate the response characteristics of real, irradiated used nuclear fuel. Pacific Northwest National Laboratory was part of the test team and used the data collected during this test to validate numerical models needed to predict the response of real used nuclear fuel in other transportation configurations. This paper summarizes the modeling work and identifies lessons learned related to the modeling and analysis methodology. The modeling includes railcar dynamics using the NUCARS software code and explicit dynamic finite element modeling of used nuclear fuel cladding in LS-DYNA. The NUCARS models were validated against railcar dynamics data collected during captive track testing at the Federal Railroad Administration’s Transportation Technology Center in Pueblo, CO. The LS-DYNA models of the fuel cladding were validated against strain gage data collected throughout the test campaign. One of the key results of this work was an assessment of fuel cladding fatigue, and the methods used to calculate fatigue are detailed in this paper. The validated models and analysis methodologies described in this paper will be applied to evaluate future UNF transportation systems.
Application of Machine Learning in Pipeline Integrity Reliability
Authors: Yin Eunice , Fernandes Phil , Woo Janine , Langer Doug , Hassanien Sherif
Published: November 2019

Probabilistic analysis is becoming increasingly adopted by pipeline integrity management practices in recent years. The practice employs reliability engineering methods to address pipeline integrity and safety concerns. At present, the industry is beginning to pair reliability methods with numerical methods to estimate probabilities of failure (PoF) for individual defects, or features, in a pipeline. The effort required for this can be intensive, since it must be repeated on hundreds of thousands of features, which need to be analyzed on a regular basis. This poses a challenge for pipeline reliability engineers, given limited human and computational resources.

In the meantime, machine learning applications in many industries have grown significantly due to advancements in algorithms and raw computing power. With massive amounts of raw data available from inline inspection (ILI) tools, and artificial data available through simulation techniques, pipeline integrity reliability becomes a promising field in which to apply machine learning technology to fast-track PoF estimation. Since a large population of reported features have low PoFs and pose low risk to integrity and safety, they can be safely screened out using fast machine learning models to free up engineers who can be dedicated to in-depth analysis of more critical features, which could have a much larger impact on pipeline operational safety.

In this paper, two machine learning models are proposed to address the pipeline integrity reliability challenges. The regression model was able to predict features with low PoFs with 99.99% confidence. The classification model was able to conservatively predict PoFs so that no high PoF feature was misclassified as being low PoF, while correctly filtering out 99.6% of the low PoF features. The proposed approach is presented and validated through pipeline integrity simulated case studies.
Fatigue Evaluation Method for Piping System Based on Total Input Energy and One-Cycle Momentary Input Energy
Authors: Sakai Michiya , Tamura Ichiro , Matsuura Shinichi , Shimazu Ryuya , Ono Yohei , Hagiwara Yutaka
Published: November 2019

In this study, the fatigue damage evaluation of seismic loadings was proposed and applied to an elbow of a three-dimensional simple piping system. The energy evaluation method was employed, focusing on energy balance of the total input energy and energy absorption of the piping system. Moreover, the concept of one-cycle momentary input energy was used for counting the loading cycle. Fatigue damage evaluation of the piping system was performed according to the maximum response of the elbow from the experimental results. The fatigue evaluation results were compared with the shaking test results of the piping system. Moreover, they were determined to be within the factor of 2 range, and were demonstrated to be applicable.
Effect of Welding Conditions on Sheets’ Interface Properties in Friction Stir Spot Welding of Copper
Authors: Mahgoub Ahmed , Merah Neçar , Bazoune Abdelaziz
Published: November 2019

Friction Stir Spot Welding (FSSW) is a solid-state joining technique widely applied to high conductive metals. In this paper, the effects of FSSW parameters, namely, rotational speed (N), plunging rate (V) and dwell time (DT) on the joint fracture mode and fractured surface morphology were investigated using scanning electron microscopy (SEM). The effect of the abovementioned welding parameters on the microhardness profile along the sheets’ interface was also investigated to gain insight into the strength of the joint and the width of the bonding ligament. Two conditions were considered for each parameter 1200 rpm and 900 rpm for N, 60 mm/min and 20 mm/min for V, 4 and 2 seconds for DT. The welding condition 1200 rpm rotational speed, 20 mm/min plunging rate and 2 seconds dwell time showed a wider bonding ligament, relatively higher elongation, higher tensile failure load, and greater microhardness on the sheets’ interface.

Dimple surface morphology (DSM) with regular dimples along the stir zone was also observed at the abovementioned set of process parameters.
Estimating Collapse Pressure of Centralizer Subs From Machine Learning Models
Authors: Chakraborty Ishita
Published: November 2019

Centralizer subs are run in conjunction with the casing strings in the oil/gas wells to ensure that the casing is centralized while it is installed down hole. Centralizer subs are fabricated of stronger material than the casing strings and designed such that it can sustain a higher collapse pressure than the attached tubing string. A typical centralizer sub is a tube with some complex geometrical features, so the collapse pressure of a centralizer sub can only be estimated by conducting a finite element analysis or subjecting it to a collapse pressure test. Both the options are time consuming and expensive.

In this work, a machine learning based regression model is used to derive a parametric equation for calculating the collapse pressure of a centralizer sub. The data needed to train and cross validate the regression model is obtained from finite element analysis (FEA).

This machine learning based equation provides a closer estimate of the collapse pressure of the centralizer subs to the results obtained from the FEA than the existing collapse prediction equations from API RP 1111. This machine learning based estimation of collapse pressure will help in correctly predicting the collapse rating of the centralizer sub without performing FEA or testing for each individual subs.

This approach of building machine learning models from data generated from FEA can be used for analysis of other equipment as well. With the availability of past data collected/generated through years, the recent advances in machine learning can be used to save time and resources.
Impact of BFJA Training on Bolted Flange Joint Assembly Reliability
Authors: Dupre Ross
Published: November 2019

A bolted flange joint assembly is a complex mechanical device, according to ASME PCC-1. A complex mechanical device’s reliability depends on many activities being performed prior and during the assembly of the bolted flange joint assembly (BFJA) being assembled. Some of these activities being; required torque calculations; gasket material selection, fastener selection, type of flange, fastener condition, lubrication, and maybe the most important activity being the assembly of the bolted flange joint. How does one ensure the correct methods and best practices being used during the assembly of the bolted flange joint?

Education. Educating not only the assemblers but also the engineers, supervisors, foreman, etc. By educating more than just the assemblers we can create a proper culture to ensure BFJA reliability. We can quantify increased BFJA reliability spurred from education by using surveys completed by the assemblers who have gone through the training.
Defining the How and When to Execute Single Stud Replacement (SSR) of Bolted Flanged Joints
Authors: Rodery Clay D. , Hamilton Scott , Ferguson Neil , Jung Gonghyun
Published: November 2019

Single Stud Replacement (SSR), or as currently known in ASME PCC-2 as “Hot Bolting” is the removal and replacement of studs on a bolted joint on a one at a time basis in a predetermined sequence. One of the key aspects in the successful execution of this activity is the determination of the appropriate maximum pressure governing the operation. The guidance currently provided in ASME PCC-2 is somewhat arbitrary and vague, and some clearer definition of a technical basis in this area would be valuable to industry in terms of both productivity and safety.

To provide additional clarity to this activity, a Task Group within the ASME Post Construction Subcommittee on Flanged Joint Assembly is redrafting the article detailing procedures for Single Stud Replacement. This paper discusses the work and focuses on the task of determining and documenting a technical basis for setting the limits (e.g., maximum pressure, effects of external moments, etc.) to safely execute a Single Stud Replacement operation.
Longitudinal Seam Welded Piping Assessment in Refinery Reformer Units
Authors: Dalal Mitul , Penso Jorge , Dewees Dave , Brown Robert
Published: November 2019

Creep is progressive deformation of material over an extended period when exposed to elevated temperature and stresses below the yield strength. Poor Creep ductility and cracking can be a problem above 900 °F (482°C) in the HAZ of low alloy (Cr-Mo) steel. High stress areas, including supports, hangers and fittings are more vulnerable to cracking. Creep cracking has occurred in longitudinal pipe welds with excessive peaking or welds with poor quality. Numerous incidents of cracking in low alloy (Cr-Mo) steel have been reported in the power industry and in refineries with major concern in longitudinal seam welds as well as highly stressed welds in reactors-heaters interconnecting piping. This paper presents the results of an assessment performed on reactors-heaters interconnecting piping in a catalytic reformer unit with a maximum operating temperature of about 950 °F (510 °C) at 250 psig (1.7 MPa) (> 40 years in-service). Comprehensive inspection including visual, dye penetrant testing, thickness measurements and peaking measurements have been performed. Phased Array Ultrasonic Testing (PAUT) was utilized to detect crack-like defects and flaws. Detailed pipe stress analysis and finite element analyses (FEA) were also performed.
Proving Pipelines Safety Through Integration of Non-ILI to ILI Integrity Programs
Authors: Ibrahim Mahmoud , Hassanien Sherif , Lamborn Lyndon , Hubert Yvan
Published: November 2019

The integrity of transmission oil pipelines are often managed through in-line inspections (ILI) at regular intervals. For the last two decades, such ILI-based integrity programs along with excavations and field non-destructive testing (NDE) have proven their effectiveness in terms of reliability. In a few cases, some pipes contain; for example, a unique cracking mechanism exhibited by short, deep axial cracks located in the vicinity of girth welds. These attributes pose sizing difficulties for ultrasonic crack ILI tools. Accordingly, operators may lean on supplemental integrity activities to prove the safety of the pipelines such as; but not limited to, hydrostatic testing, laboratory testing of cut-outs, qualitative ranking of features, borehole leak detection analysis, Just-Missed-Flaw (JMF) or Just Surviving Flaw (JSF) analysis, discharge and/or point pressure restrictions, and/or a mix between all the previous techniques. Moreover, it is the operators’ responsibility to evaluate the risk associated with their integrity plans. Hence, it is important to be able to analyze the reliability of such integrity activities quantitatively. This paper presents an event-tree approach which can augment standard ILI or hydrostatic test results and probabilistic analysis with non-ILI integrity measures under one umbrella. In this approach, the likelihood of failure for both leak and rupture modes can be comprehensively estimated. The event tree approach is used herein as an inductive analytical diagram in which failure events are analyzed using Boolean logic to examine a chronological series of subsequent integrity actions and consequences. The proposed approach is also designed to capture subject matter experts’ opinion into the analysis as part of the integrity management program. The work discusses a real practical application along with verification and validation elements of the proposed integrated approach.
Role of Constraint in Specimen Geometries When Evaluating Fracture Toughness/Material Fracture Resistance for a Surface-Flawed Elbow
Authors: Kalyanam S. , Wilkowski G. , Brust F. W. , Hioe Y. , Punch E.
Published: November 2019

The fracture behavior of a circumferential surface crack in an elbow was evaluated using past data from the International Piping Integrity Research Group (IPIRG-2) Experiment 2-4. The elbow tested was nominal 16-inch diameter Schedule 100 TP304 material, which was solution-annealed after final fabrication. The elbow was loaded with an in-plane-closing bending moment and internal pressure of 15.51 MPa (2,250 psig) at 288 C (550 F). The surface crack was 180-degrees on the ID surface and centered on the extrados, but after fatigue precracking the depth was variable and the greatest was at about 45-degrees from the extrados. FE analysis of the IPIRG-2 elbow test was conducted with a state-of-the-art and precise 3D FE mesh (including variable surface crack depth, variable thickness, and initial elbow ovalization). The flaw depth for the single-edge notch tension (SENT) tests was selected to be equivalent to the deepest point in the elbow specimen crack front that provided the largest J-value in the elbow experiment, i.e., ao/W = 0.68. Comparison of the J-value for initiation (Ji) and crack-tip-opening displacement (CTODi) at crack initiation suggested that there was a slight difference in constraint between an identical depth SENT specimen (a/W = 0.68 with the same L-R orientation as the surface crack in the pipe) and an elbow with a circumferential surface crack (a/t = 0.68) [Ji was 0.368 MN/m, (2.1 ksi-inch) in the SENT tests, while it was 0.490 MN-m (2.8 ksi-inch) in the elbow test]. The more significant finding in this work was that the compact tension (C(T)) test Ji-value was much higher at 1.086 MN/m (6.2 ksi-inch) or ∼3 times higher. The elbow to SENT to C(T) specimen comparison illustrates very large differences in constraint between these geometries. From past work by several researchers it was determined that the constraint in C(T) specimens gives Ji-values that agree well with a circumferential through-wall crack in a straight pipe, but this difference with surface-cracked elbow or pipe is envisaged to be new information to the international research community. Additionally, from state-of-the-art FE analysis of the 180-degree surface-cracked elbow test it was found that the maximum J-value occurs at a position that was about 45-degree away from the extrados location. This trend showed that caution should be exercised when selecting the crack locations for elbow integrity evaluation, since for shorter flaw lengths it may be more critical to consider a crack that is closer to the 45-degrees from the extrados, which could be true for fracture as well as stress corrosion cracking (SCC) elbow evaluations.
Simulations of Fully-Flexible Fuel Bundle Response due to Turbulence Excitation
Authors: Elbanhawy Osama , Hassan Marwan , Mohany Atef
Published: November 2019

This work presents a numerical model for a fully-flexible CANDU fuel bundle to predict the vibration response due to turbulence excitation. The model includes 37 fuel elements and two endplates. The contact between system components such as fuel-to-fuel and fuel-to-pressure tube is modeled using the single point contact method (SPC). A range of flow velocities was examined, and the associated impact forces and work rates were calculated. In addition, the stresses on the endplates due to vibration of the fuel elements were predicted.
Extension of Weighted Stress Intensity Factor Rate (WKR) Method to Characterisation of Varying Temperature and Loading Rate in Plant Realistic Waveform Fatigue Crack Growth Calculations
Authors: Currie Chris , Mann Jonathan , Gill Peter , Leary Daniel , Wright Keith
Published: November 2019

The reference Fatigue Crack Growth (FCG) rate behaviour for austenitic stainless steel in a deaerated Pressurised Water Reactor (PWR) environment is provided in ASME Section XI Code Case N-809. This FCG law is dependent on load ratio and environmental factors in terms of a defined temperature and rise time.

Previous papers by Emslie et al (PVP2016-63497 and PVP2017-65645) demonstrate that environmental FCG rate enhancement is significantly better characterised by Stress Intensity Factor (K) rate than by rise time. It also demonstrates that K rate effects are increasingly important towards the top of the load cycle (ie. closer to the maximum K) and provides the Weighted Stress Intensity Factor Rate (WKR) method to account for both effects under isothermal loading conditions.

This paper extends the WKR method to include varying temperature during the loading waveform, so that both complex K and varying temperature waveform FCG rates can be predicted. A substantial body of validation test data of standard compact tension specimens under such loading is provided in support of the presented method. Further testing is proposed to enable validation suitable for future inclusion of the proposed method within Code Case N-809.
Nut-Factor Variation on Coated High-Strength Steel Fasteners After Cycling Torquing
Authors: Rosas Omar , Garcia Atahualpa Oscar , Hernandez Jose , Girault Carlos , Oldiges Donald
Published: November 2019

This study presents recent research results on the Nut-Factor of coatings applied to high-strength steel threaded fasteners mainly used in the Oil and Gas industry. PTFE coatings are commonly used to protect B7 grade material from corrosion within the industrial marketplace; however, most coatings applied to threaded fasteners do not offer a consistent tightening and they are affected by torquing during assembly. This results in an inconsistent Nut-Factor and accuracy of the provided nut-factor is not only inconsistent but also lower than most published values. The lack of consistency in the engagement produces variations in the load when torque is applied, the same torque will produce different loads depending on the surface conditions of the threads, which changes every time the fastener is re-used. Therefore, the aim of this study is to provide data on the nut-factor of coated threaded fasteners after assembly/disassembly cycles and the use of different lubricants. Torque cycles were applied to threaded fasteners with different coatings, Nickel-Cobalt electroplating, Zinc undercoat with PTFE topcoat and TSA with PTFE topcoat. The nut-factor was calculated before and after commercial lubricants were applied. Nickel-Cobalt electroplating showed an outstanding performance compared to the other tested coatings since it offered the highest nut-factor consistency. This study summarizes the optimal operational conditions for lubricants and materials and how these conditions affect the nut-factor and thread engagement.
Outline of the Recent Consolidated Revision of EN13445-3, Clause 18 and Related Annexes: Detailed Assessment of Fatigue Life
Authors: Rudolph Jürgen , Baylac Guy , Trieglaff Ralf , Gawlick Rüdiger , Krämer Michael , Simonet Yves , Triay Manuela
Published: November 2019

The European Pressure Vessel Standard EN 13445 (harmonized Standard acc. to PED 2014/68/EU) provides in its Part 3 (Design) a simplified method for fatigue assessment (Clause 17) and a detailed method of fatigue assessment (Clause 18). While the new revision of Clause 17 has already been adopted, Clause 18 “Detailed Assessment of Fatigue Life” is now available as a consolidated revision in inquiry phase. This major and comprehensive revision has been developed within the framework of the European working group CEN/TC 54/WG 53 – Design methods and constitutes a crucial step towards a modern and user-friendly engineering fatigue assessment method. The overall structure and amendments of Clause 18 are to be presented. All these amendments aim at a significant increase in user friendliness and clear guidelines for application. The following items are to be mentioned in that context:

• Fatigue assessment of welded components based on structural stress and structural hot-spot stress approaches,

• Detailed guidelines for determining relevant stresses and stress ranges,

• Cycle counting proposals in the context of the fatigue assessment method including a critical plane approach.

The fatigue assessment of welded components is separated from the fatigue assessment of un-welded parts as it has already been done in previous versions with respective methodological differences. Stress analyses for clause 18 are usually based on detailed finite element analyses (FEA). As an essential amendment for the user, the determination of structural stress ranges for the fatigue assessment of welds is further detailed in a new appropriate annex.

Different applicable methods for the determination of structural stresses are explained in connection with the requirements of the finite element models and analyses. The cycle counting issue is comprehensively treated in the context of different design and operation situations (design transients, operational stress-time-histories). The description is detailed towards a critical plane approach. Detailed proposals for implementation in an algorithmic programming framework are given making the described methods ready to use.
New Leakage Requirements for ASME B16.20 and Current Generation Spiral Wound Gaskets
Authors: Bausman Anita , Waterland Jerry , Reid Dan
Published: November 2019

The ASME B16.20 Metallic Gaskets for Pipe Flanges standard was extensively revised in 2017 [1]. One of the significant changes is the introduction of maximum permissible leakage rate. This marks a landmark introduction of an actual leakage performance criterion into ASME B16.20, a most welcome advance. A common maximum permissible leakage rate of 0.0137 mg/s-m (7.67E−10 lb/s-in) is specified for all sizes and pressure classes of finished spiral wound gaskets, that is, including the windings and any or no gauge rings for that particular gasket. Test conditions are defined — ambient temperature and calibration gas with a known methane concentration and flow rate of 1 L/min. The test pressure is defined by the pressure class: 20 bar (290 psi) for Class 150 and 40 bar (580 psi) for Class 300 and above. The qualification parameters listed in B16.20-2017 include prescribed gasket seating stress targets which also vary by pressure class. These gasket seating stress requirements are defined as 35 MPa (5,000 psi) for Class 150, 56 MPa (8,000 psi) for Class 300 and Class 400, and 70 MPa (10,000 psi) for Class 600 and above. Three questions will be explored in this paper. First, to what tightness does the new B16.20 spiral wound gasket leakage rate criterion correspond? Second, do current generation spiral wound gaskets meet this criterion? Several commercially available spiral wound gaskets will be analyzed and compared to the new B16.20 requirements. Leak rates and tightness at the new B16.20 performance qualification test conditions can be determined using publicly available, published Room Temperature Tightness (ROTT) test constants for these gaskets. Finally, an exploration of Assembly Tightness compared to Operating Tightness for a selection of spiral wound gaskets will be presented and compared to the new B16.20 Performance Testing requirements. This exploration of the new maximum leakage performance criterion in ASME B16.20-2017 will help to familiarize the end user with a valuable new aspect of this gasket standard as well as how the current generation of spiral wound gaskets meets that criterion using publicly available ROTT performance data.
Engineering J Estimates for Spent Fuel Canisters Under Combined Mechanical and Welding Residual Stresses
Authors: Lee Hyun-Jae , Kim Yun-Jae , Lam Poh-Sang , Sindelar Robert L.
Published: November 2019

This paper compares engineering J estimates for Spent Fuel Canisters (SFCs) under combined mechanical and welding residual stress (WRS) with finite element (FE) results. Engineering J estimates are based on reference stress method provided in the R6 procedure considering interaction between primary and secondary stresses using the V-factor. It is found that residual stress should be considered in fracture assessment and the R6 estimates are reasonably conservative compared to FE analysis results.
Bolted High Pressure Girth Flange Connections
Authors: Hantsch Christoph
Published: November 2019

Besides metallic lens ring gaskets for piping applications the high-pressure processes for LDPE production also require gaskets for bolted girth flange connections. A typical application is the 380 bar (5500 psi) head to tubesheet connection of a recycle gas cooler for the LDPE production process. The most common gasket types for this application are either solid ring or spring energized seals. During startup of an LDPE tube-reactor severe ethylene leaks occurred even though the flanged connection had successfully passed the hydrotest at the fabrication shop. A detailed investigation supported by the exchanger fabricator, gasket manufacturer and LDPE process licensor found that connections having line contact stress need to be treated differently from commonly known surface pressure based flat gasket connections. In this paper the author explains the basic considerations for leak tight flange design using spring energized gaskets supported by FEA based root cause leak investigation results. Conclusions are drawn about the appropriate limits for deflection of flanges as compared to results using bolted flat gasket types like Kammprofile gaskets.
Leak Rates Through Complex Crack Paths: Update on the Latest Developments From the European Project ATLAS+
Authors: Gill Peter , Nicak Tomas , Daniels Brian , Obermeier Florian
Published: November 2019

Leak-before-Break assessments require a reliable method to obtain leakage rates from narrow cracks. The ability to predict leakage accurately is crucial to the overall success of Leak-before-Break arguments as the detection capability and limiting crack size are often very small. This can make it difficult to achieve the desired margin between limiting defect size and the crack size required for detectable leakage. The resulting narrow flow paths (< 0.1mm) relative to the wall thickness (> 10mm) necessitates the use of complex thermodynamic and friction models in the leak rate calculation.

A method to calculate leakage rates through complex paths was presented in PVP2015-45468 using an ordinary differential equation (ODE) for Mach number. This model was developed to account for crack opening displacements that vary non-linearly through the wall of a pipe. This situation typically arises when there is a through wall crack at a weld, where significant residual stresses are present. This paper considers an FEA model of a plate with a weld residual stress (WRS) profile applied. The WRS is prescribed with nodal displacements, and the COD is calculated from post processing of the elastic stress analysis solution. This results in a COD function in terms of the distance through the wall, which can then be used in the leak rate calculation. Comparisons are made with the R6 methodology recommended software DAFTCAT and the benefits of using the ODE method are discussed.

In collaboration with Framatome, Germany, a test case based on the previous European project STYLE was considered. The test case involves a Type 316L Stainless Steel pipe with a girth weld, and the FEA model includes postulated through wall defects at the weld interface to assess crack opening displacements. This model will be used to extract crack opening displacements and calculate leak rates using various methods. Two phase flow will be considered for this test case as the pipe geometry is very relevant to PWRs.
Evaluation of the Effect of Internal Pressure and Flaw Size on the Tensile Strain Capacity of X42 Vintage Pipeline Using Damage Plasticity Model in Extended Finite Element Method (XFEM)
Authors: Agbo Sylvester , Lin Meng , Ameli Iman , Imanpour Ali , Duan Da-Ming , Cheng J. J. Roger , Adeeb Samer
Published: November 2019

Pipelines subjected to displacement-controlled loading such as ground movement may experience significant longitudinal strain. This can potentially impact pipeline structural capacity and their leak-tight integrity. Reliable calibration of the tensile strain capacity (TSC) of pipelines plays a critical role in strain-based design (SBD) methods. Recent studies were focused mostly on high toughness modern pipelines, while limited research was performed on lower-grade vintage pipelines. However, a significant percentage of energy resources in North America is still being transported in vintage pipelines. Eight full-scale pressurized four-point bending tests were previously conducted on X42, NPS 22 vintage pipes with 12.7 mm wall thickness to investigate the effect of internal pressure and flaw size on TSC. The pipes were subjected to 80% and 30% specified minimum yield strength (SMYS) internal pressures with different girth weld flaw sizes machined at the girth weld center line. This paper evaluates the TSC of X42 vintage pipeline by utilizing ductile fracture mechanics models using damage plasticity models in ABAQUS extended finite element method (XFEM). The damage parameters required for simulating crack initiation and propagation in X42 vintage pipeline are calibrated numerically by comparing the numerical models with the full-scale test results. With the appropriate damage parameters, the numerical model can reasonably reproduce the full-scale experimental test results and can be used to carry out parametric analysis to characterize the effect of internal pressure and flaw size on TSC of X42 vintage pipes.
Stress Intensity Factors for Layered Pressure Vessel Inner Layer Through Cracks
Authors: Hobbs Joel R.
Published: November 2019

A difficulty encountered when performing Fitness-for-Service assessments for layered pressure vessels (LPVs) is the lack of stress intensity factor solution in literature that produce accurate results for inner layer longitudinal through cracks. Using surrogate solutions such as a through crack in a plate or cylinder produce results that can be overly conservative especially for longer cracks. This is largely due to the ability of a layered pressure vessel to redistribute hoop load to other layers, the restricted radial movement of the cracked layer, and the friction forces applied in the cracked region.

To understand this problem, a parametric finite element model (FEM) generator was developed that is capable of producing layered pressure vessel models with inner layer through cracks. The results from the FEMs were used to create a dataset of inner layer through crack stress intensity factors (Ki) for layered pressure vessels corresponding to variations of internal pressure, radius, layer thicknesses, friction factor, and crack length. The elastic modulus of the material also has an effect on Ki but, for this dataset, the elastic modulus was fixed at the typical value for steel – 29,500 ksi (203 GPa).

Finally, a non-dimensional model was developed and calibrated using the dataset. This allows Ki to be calculated without the need of a FEM using a closed-form equation. The results of the closed-form solution were then compared to FEM results showing accuracy was generally within 10%.
Data Analysis and Model Validation of Natural Gas Transmission Pipeline With Compressor Station
Authors: Cheng David
Published: November 2019

Data from the DCS systems provides important information about the performance and transportation efficiency of a gas pipeline with compressor stations. The pipeline performance data provides correction factors for compressors as part of the operation optimization of natural gas transmission pipelines.

This paper presents methods, procedure, and a real life example of model validation based performance analysis of gas pipeline. Statistic methods are demonstrated with real gas pipeline measurement data. The methods offer practical ways to validate the pipeline hydraulics model using the DCS data. The validated models are then used as performance analysis tools in evaluating the fundamental physical parameters and assessing the pipeline hydraulics conditions for potential issues influencing pressure drops in the pipeline such as corrosion (ID change), roughness changes, or BSW deposition.
Prediction of Structural Reliability Through an Alternative Variability-Based Methodology
Authors: Haas Kyle
Published: November 2019

Astonishing increases in computational power have fueled the engineering community’s drive to seek increasingly optimized solutions to structural design problems. Although structural optimization can be critical to achieve a practical and cost-effective design, optimization often comes at a cost to reliability. The competing goals of optimization and reliability amplify the importance of validation, verification, and uncertainty quantification efforts to achieve sufficiently reliable performance. Evaluation of a structural system’s reliability presents a practical challenge to designers given the potentially large number of permutations of conditions that may exist over the full operational lifecycle. A direct prediction of performance and the prediction’s corresponding likelihood is often achieved via deterministic analysis techniques in conjunction with Monte Carlo analysis. Such methods can be overly cumbersome and often do not provide a complete picture of the system’s global reliability due to the practical limits of performing the necessary number of analyses. At the point of incipient structural failure, the structural response becomes highly variable and sensitive to minor perturbations in conditions. This characteristic provides a powerful opportunity to determine the critical failure conditions and to assess the resulting structural reliability through an alternative, but more expedient variability-based method. Non-hierarchical clustering, proximity analysis, and the use of stability indicators are combined to identify the loci of conditions that lead to a rapid evolution of the structural response toward a failure condition. The utility of the proposed method is demonstrated through its application to a simple nonlinear dynamic single-degree-of-freedom structural model. A feedforward artificial neural network is trained from numerically-generated data to provide an expedient means of assessing the system’s behavior under perturbed conditions. In addition to the L2-norm, a new stability indicator is proposed called the “Instability Index”, which is a function of both the L2-norm and the calculated proximity to adjacent loci of conditions with differing structural response. The Instability Index provides a rapidly achieved quantitative measure of the relative stability of the system for all possible loci of conditions.
Risk Assessment for Model and Simulation Credibility Characteristics
Authors: Madry John G. , Elele James N. , Hall David H. , Turner David J.
Published: November 2019

The Department of Defense (DoD) uses the principles of risk assessment extensively throughout the acquisition process to identify, manage, and mitigate risk in many areas including software (both simulation software and software embedded in materiel systems). The approach to assessing the risks associated with using results from Models and Simulations (M&S) to influence decision-making that is described here is used by the Naval Air Systems Command (NAVAIR) 5.4H Verification, Validation, and Accreditation office.

The focus of the risk assessment is on ten specific characteristics of M&S Capability, Accuracy, and Usability that have the most potential impact on the intended uses. In this method, the characteristics of the M&S are evaluated against standard criteria, and then assigned a color-rating of Green, Yellow, or Red based on the actual data obtained from the M&S itself. A simple computation is then used to weigh the ratings of the characteristics into the likelihood of error aspect of the risk of using the M&S. A thorough understanding of the M&S and its application is a prerequisite to using this approach since the analyst is required to provide a technical justification for the rating assigned to a characteristic. Should the assigned rating for a characteristic of the M&S not be green, the analyst is required to recommend actions and/or mitigations for the M&S developer to take that would improve the rating to green.
Tri-modal speech: Audio-visual-tactile integration in speech perception
Authors: Derrick Donald , Hansmann Doreen , Theys Catherine
Published: November 2019

Speech perception is a multi-sensory experience. Visual information enhances [Sumby and Pollack (1954). J. Acoust. Soc. Am. 25, 212–215] and interferes [McGurk and MacDonald (1976). Nature 264, 746–748] with speech perception. Similarly, tactile information, transmitted by puffs of air arriving at the skin and aligned with speech audio, alters [Gick and Derrick (2009). Nature 462, 502–504] auditory speech perception in noise. It has also been shown that aero-tactile information influences visual speech perception when an auditory signal is absent [Derrick, Bicevskis, and Gick (2019a). Front. Commun. Lang. Sci. 3(61), 1–11]. However, researchers have not yet identified the combined influence of aero-tactile, visual, and auditory information on speech perception. The effects of matching and mismatching visual and tactile speech on two-way forced-choice auditory syllable-in-noise classification tasks were tested. The results showed that both visual and tactile information altered the signal-to-noise threshold for accurate identification of auditory signals. Similar to previous studies, the visual component has a strong influence on auditory syllable-in-noise identification, as evidenced by a 28.04 dB improvement in SNR between matching and mismatching visual stimulus presentations. In comparison, the tactile component had a small influence resulting in a 1.58 dB SNR match-mismatch range. The effects of both the audio and tactile information were shown to be additive.
Comparison of four decision aids for the early diagnosis of acute coronary syndromes in the emergency department
Authors: Body Richard , Morris Niall , Reynard Charles , Collinson Paul O
Published: November 2019

Objectives

To directly compare the diagnostic accuracy of four decision aids (Troponin-only Manchester Acute Coronary Syndromes (T-MACS), History, ECG, Age, Risk factors and Troponin (HEART), Thrombolysis in Myocardial Infarction (TIMI) and Emergency Department Assessment of Chest Pain (EDACS)) used to expedite the early diagnosis of acute coronary syndromes (ACS) in the ED.

Methods

We prospectively included patients who presented to 14 EDs in England (February 2015 to June 2017) with suspected ACS within 12 hours of symptom onset. Data to enable evaluation of the T-MACS, HEART, TIMI and EDACS decision aids (without recalibration) were prospectively collected, blinded to patient outcome. We tested admission blood samples for high-sensitivity cardiac troponin I (hs-cTnI; Siemens ADVIA Centaur). Patients also underwent serial cardiac troponin testing over 3–12 hours. The target condition was an adjudicated diagnosis of acute myocardial infarction (AMI). We also evaluated the incidence of major adverse cardiac events (including death, AMI or coronary revascularisation) at 30 days. Diagnostic accuracy of each decision aid and hs-cTnI alone (using the limit of quantification cut-off, 3 ng/L) was evaluated by calculating sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).

Results

Of 999 included patients, 132 (13.2%) had AMI. C-statistics were 0.96 for T-MACS, 0.78 for HEART and 0.69 for TIMI. The sensitivities of T-MACS, HEART, TIMI, EDACS and hs-cTnI <3 ng/L for AMI were 99.2% (95% CI 95.7% to 100.0%), 91.8% (85.0% to 96.2%), 97.5% (92.9% to 99.5%), 96.2% (92.2% to 99.4%) and 99.2% (95.9% to 100.0%), respectively. The respective strategies would have ruled out 46.5%, 34.9%, 19.4%, 48.3% and 28.8% patients. PPVs for the decision aids that identify ‘high-risk’ patients were 80.4% (T-MACS), 51.9% (TIMI) and 37.2% (HEART).

Conclusions

In this study, T-MACS could rule out AMI in 46.5% patients with 99.2% sensitivity. EDACS could rule out AMI in 48.3% patients with lower sensitivity, although the difference was not statistically significant. The HEART and TIMI scores had lower diagnostic accuracy.
The effect of flavoured and non-flavoured tobacco on subjective experience, topography and toxicant exposure among waterpipe smokers
Authors: Ben Taleb Ziyad , Vargas Mayra , Ebrahimi Kalan Mohammad , Breland Alison , Eissenberg Thomas , Brown David , Maziak Wasim
Published: November 2019

Introduction

Flavoured waterpipe (WP) tobacco is a major factor in the resurgence of WP smoking and a main attractant of WP use among youth. Yet, evidence of the effects of limiting flavour on WP smoker’s experiences and exposures is limited. This study examined the impact of flavour manipulation on WP smokers’ toxicant exposure and smoking experiences.

Method

A total of 144 WP smokers attended two, 45 min ad libitum smoking sessions (flavoured vs non-flavoured tobacco) in a crossover design study. Participants completed a battery of questions assessing subjective smoking experiences. Exhaled carbon monoxide (eCO) and plasma nicotine concentrations were measured before and after the smoking sessions. Puff topography was recorded throughout the smoking sessions.

Results

Compared with the non-flavoured WP tobacco, participants reported enhanced subjective smoking measures of satisfaction and enjoyment following smoking flavoured WP tobacco (ps <0.05). Although participants spent a longer time smoking flavoured tobacco, they took on average larger puffs while smoking the non-flavoured tobacco (ps <0.05). Greater levels of eCO were recorded following the non-flavoured tobacco session (p<0.05) compared with flavoured tobacco. No significant differences were observed in plasma nicotine concentrations between the two tobacco conditions. WP harm perception was higher among participants after smoking non-flavoured WP tobacco compared with their preferred flavour (p<0.05).

Conclusion

Smoking the flavoured tobacco product was associated with enhanced subjective experiences compared with the non-flavoured, suggesting a potential role for flavour regulation in reducing WP use. Mixed results were observed for toxicants exposure in relation to smoking flavoured compared with non-flavoured products suggesting the need for a more comprehensive assessment of the effects of other tobacco constituents and additives on toxicant exposure in WP smokers.