bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Analyses of Incidents on Oil and Gas Pipelines Based on Comparing Different Pipeline Incident Databases
Authors: Shan Ke , Shuai Jian
Published: October 2017

Pipelines are regarded as one of the most practical and economical modes for transporting dangerous and combustible substances, such as oil and gas. However, the use of historical failure data in qualitative risk assessment of oil and gas pipelines is unusual due to lack of data or incomplete information. The pipeline incident database (PID) provides valuable information for researchers to identify potential threats of oil and gas pipeline systems, and catty out effective risk assessment. In this study, pipeline failure statistics such as pipeline classifications, incident definitions, failure causes and failure frequencies from the United States, Canada, Europe and United Kingdom are compared. Failure frequency of oil and gas pipelines for different kinds of primary failure causes are estimated from the statistical analysis of the mileage, pipe-related incident, and failure cause data collected by each PID. Although above-mentioned databases are established by pipeline operators in developed countries, the statistical analyses of incidents on oil and gas pipelines based on comparing different pipeline incident databases can benefit the quantitative risk assessment of pipeline systems also in some developing countries where pipeline incident database haven’t been established.
On Categorization of Seismic Load As Primary or Secondary
Authors: Labbé Pierre B.
Published: October 2017

The concept of primary/secondary categorization is first recalled and generalized for its application to an elastic-plastic oscillator subjected to a seismic load. Categorizing the seismic load requires calculating the input level associated to the oscillator ultimate capacity and compare it to the level associated to the plastic yield. In order to resolve this non-linear dynamic problem, it is assumed that the non-linear oscillator behaves like a linear equivalent oscillator, with an effective stiffness (or frequency) and an effective damping. However, as it is not a priori possible to predict the equivalent stiffness and damping, a wide range of possibilities is systematically considered. The input motion is represented by its conventional response spectrum.

It turns out that key parameters for categorization are i) the “effective stiffness factor” (varying from 0 for perfect damage behaviour to 1 for elastic-perfectly plastic) and the slope of the response spectrum in the vicinity of the natural frequency of the oscillator. Effective damping and spectrum sensitivity to damping play a second order role. A formula is presented that enables to calculate the primary part of a seismically induced stress as a function of both the oscillator and input spectrum features. The formula is also presented in the form of an abacus.

The actual “effective stiffness factor” of different piping systems is derived from outputs of experimental research programs carried out in the past in USA and Japan and still ongoing in India. It appears that even when experiencing large plastic strains under beyond design input motions, the observed effective frequency of piping systems is very close to their natural frequency, decreasing only by a few percents. These observations enable to calculate an effective stiffness factor value around 0.9 and lead to the conclusion that the seismic load, or the seismically induced inertial seismic strains, should basically be regarded as secondary in the sense of the definition adopted here.
Upper Shelf Energy Prediction Model for Irradiated Reactor Vessel Steels
Authors: Ogawa Takuya , Hall J. Brian , Mays Benjamin E. , Hardin Timothy C.
Published: October 2017

Current USA regulations in 10 CFR 50, Appendices G & H ensure adequate fracture toughness and provide for the monitoring of radiation embrittlement of the ferritic components of the reactor pressure vessel (RV). Regulatory Guide (RG) 1.99, Rev. 2 provides guidance on acceptable methods for predicting the effects of neutron irradiation in order to meet the requirements of Appendix G. Specifically, RG 1.99, Rev. 2 provides an embrittlement prediction model for Charpy transition temperature shift (TTS) and a prediction model for decreased Charpy upper shelf energy (USE). The prediction model for USE decrease has remained unchanged since introduction of RG 1.99 in 1975. The objective of this study is to present new USE prediction model(s) developed using an international light water reactor database similar to the effort behind the recently-updated ASTM E900-15 TTS prediction model. A database of ASME and similar specification USE decrease information was developed from USA and select international light water reactor surveillance capsule data, including the latest surveillance capsule fluence, irradiation temperature, material chemistry and other information. The USE database has more than 1,500 USE change measurements of irradiated RV steels. Several best estimation models to predict irradiated USE of materials were developed based on data fitting. Two types of best estimation models were investigated; one model type uses the ASTM E900-15 predicted TTS as a primary input parameter, while the other does not, so that a USE prediction could be made independently of the ASTM E900-15 TTS prediction. By using the ASTM E900-15 TTS as a primary input, the models of the first type implicitly considered the embrittlement mechanisms of matrix damage and copper rich precipitation. In the non-TTS models, the effect of copper was expressed by a hyperbolic tangent curve that has both an upper value and lower value in order to consider the effect of copper saturation. Associated standard deviations as a function of predicted USE were also established so that bounding predictions could be made. Bounding models from each type that conservatively predict irradiated USE by bounding at least 95% of the USE decrease data in the database were identified. These bounding models are estimated to have relatively low impact on the number of USA plants that are projected to have RV steels that drop below 50 ft-lbs (68 J) relative to RG 1.99, Rev. 2. Finally, a non-TTS model was selected as the recommended model, because it does not require calculation of TTS by ASTM E900-15 and thus is simpler to implement.
Seismic Qualification of Piping Systems by Detailed Inelastic Response Analysis: Part 4 — Second Round Benchmark Analyses With Stainless Steel Piping Component Test
Authors: Watakabe Tomoyoshi , Nakamura Izumi , Otani Akihito , Morishita Masaki , Shibutani Tadahiro , Shiratori Masaki
Published: October 2017

Some studies concerning ultimate strength of piping under seismic loads concluded that there is a large design margin until failure, even if the stress calculated based on the current design method does not satisfy design criteria. To provide a more rational seismic design, a new Code Case for seismic design of piping is now under development in the framework of JSME Nuclear Codes and Standards. The Code Case incorporates a dynamic elastic-plastic analysis procedure by employing finite element analysis as an alternative to the current design analysis method of elastic assumption. To confirm the applicability of inelastic response analysis, benchmark analyses have been conducted. In the first round benchmark, a carbon steel elbow analysis was performed. In this report, a second round benchmark with a stainless steel elbow and tee is introduced. The second benchmark aims to establish an analysis procedure for stainless steel piping and tee piping of complicated shapes. The second benchmark results provided a practical analysis method for stainless steel piping, and the Code Case was expanded so that it could be applied not only to carbon steel piping but also to stainless steel piping. The second benchmark also challenged analyses of a tee having complicated geometry. These results provide some important knowledge, and they will be included in the Code Case.
Design Guidelines for Dynamic Stability of Tainter Gates
Authors: Anami Keiko , Ishii Noriaki , Knisely Charles W. , Oku Tatsuya
Published: October 2017

To ensure the long-term safe operation of newly constructed Tainter gates, methods of analysis and design criteria are needed in the design stage to assure the dynamic stability of any new Tainter gate. For this purpose, the present study provides a detailed procedure for the dynamic design of Tainter gates that can be applied to preliminary designs by gate engineers to assure the dynamic stability of their gate designs. The dynamic stability of the gate can be determined using the natural vibration characteristics ascertained by finite element method (FEM) analysis, reasonable values of actual structure damping actually measured by the field vibration tests, and theoretical analysis of the coupled-mode self-excited vibration that has been previously established by authors. The procedure and the important points of each step are detailed in an example determination of the dynamic stability of a practical Tainter gate.
GA-Optimized Fuzzy State Space Model of Multi Degree Freedom Structure Under Seismic Excitation
Authors: Pham Huu Thang , Sone Akira , Miura Nanako
Published: October 2017

Active structural control has drawn significant attention in recent decades. In this paper, the problem of active vibration control of multi-degree-freedom structures is considered. Fuzzy logic controller combined with the genetic algorithm (GA) is designed to optimize the parameters of active tuned mass damper (ATMD) for the best results in reduction of the building response under earthquake excitation. The advantage of the fuzzy logic approach is the ability to handle the non-linear behavior of the system. Non-linear behavior of the soil is modeled in the dynamics of the structural system with nonlinear hysteric restoring forces. The building structure with eleven stories is modeled as a 2D frame, which uses tuned mass damper subsystems mounted on the top of the building. A structural system was simulated against the ground motion of the destructive earthquakes. The time history of the story displacements and accelerations, the control voltages and forces, and the frequency responses of both the uncontrolled and the controlled structures are shown in the end of this study. The performance of designed fuzzy logic control is checked using the changing mass parameters of each story and the results are discussed. The comparison between the proposed control and TMD passive control shows that the proposed fuzzy logic controller has great potential in active structural control.
Influence of Nonhomogeneous Microstructure of Multi-Pass Weld Metal on Creep Behavior of Cross-Weld Specimen Based on Finite Element Method
Authors: Yang Bin , Xuan Fu-Zhen
Published: October 2017

Creep analysis of cross-weld specimen was conducted by numerical method, with the influence of nonhomogeneous microstructure of multi-pass weld metal included. Finite element models were established: one is a 3D simplified model with weld metal considered as homogeneous material, and the other two are 2D and 3D multi-pass models, in which weld metal is composed of columnar grain zone, equiaxed grain zone and recrystallized grain zone. The creep life and maximum damage location predicted by the above models were compared with each other and the effects of the configuration of welding passes, energy input and welding speed were also mentioned. Results indicated that the influence of the nonhomogeneous microstructure of multi-pass weld metal is not obvious at high stress level, while it becomes more remarkable with the decrease of the stress. The creep life of weldment can be extended with intervened arrangement of welding passes. Lower welding speed and energy input may be a candidate option to improve creep properties of weldment.
Investigation on Method of Elasto-Plastic Analysis for Piping System Made of Stainless Steel: Secondary Benchmark Analysis
Authors: Arai Masashi , Kojima Nobuyuki , Kabaya Takuro , Hirouchi Satoru , Bando Masatsugu
Published: October 2017

This paper provides investigation on method of elasto-plastic analysis for practical seismic design of nuclear piping system made of austenitic stainless steel. Our policy for the evaluation is that material properties used in the benchmark analyses are based on Japanese standard in nuclear design. The result of the first phase of this benchmark analysis intended for carbon steel piping systems has been provided in ASME PVP2016-63186[1].

In secondary benchmark analysis, analytical investigations focused on austenitic stainless steel piping were conducted. These analysis objects are two vibrating tests (model 1: piping containing an elbow, model 2:piping containing a tee). The elasto-plastic characteristic based on bilinear plasticity model based on the draft code case of JSME (Japan Society of Mechanical Engineers) was used in analyses. Additionally, analyses using the elasto-plastic characteristic which made yield point and 2nd modulus as a parameter were also carried out.

For the model 1, the maximum strain estimated by elasto-plastic analysis using the elasto-plastic characteristics of stainless steel material determined as proposed by the draft code case of JSME agreed well, but on the safe side, with the experiment. However, this is not the case for the model 2: the maximum strain estimated using the same elasto-plastic characteristics was underestimated compared with the experiment. However, for both the models 1 and 2, the elasto-plastic behavior of the piping systems estimated by this analysis was approximately the same between the analysis with the material’s elasto-plastic characteristics approximated by bilinear plasticity modeling proposed by the draft code case of JSME and that approximated by the same bilinear plasticity modeling but with different setting of yield point and 2nd modulus values of the material.

A possible cause of the underestimate that occurred in the model 2 is, according to the shape data of the tee, that the wall thickness of the tee is so large that its connection with the main and branch pipes has a large, step-like change in thickness, as opposed to the model that was designed without referencing the shape data. Another possible cause of this underestimate is coarse meshes of elements of the model. In order to improve analytical accuracy, it is necessary to add a method for modeling tee joints to the draft code case. To this end, a database of the shape of tee joints should be developed in cooperation with the manufacturers so that an optimum modeling method can be developed.

As mentioned above, according to the result of elasto-plastic analyses for the model 1 (piping containing an elbow) and model 2 (piping containing a tee), it is necessary to develop a modeling method for tee joints. It is likely possible to directly use the elasto-plastic characteristics of carbon steel for the purpose of analyzing a piping of stainless steel.
Features Testing of Stud Material Under Low Constraint Ductile Tearing
Authors: James P. , Jackson M. , Birkett P. , Madew C.
Published: October 2017

Defect tolerance assessments are carried out to support the demonstration of structural integrity for high integrity components such as nuclear reactor pressure vessels. These assessments often consider surface-breaking defects and assess Stress Intensity Factors (SIFs) at both the surface and deepest points. This can be problematic when there is a high stress at the surface, for example due to the stress concentration at the root of a screw thread. In the past this has led to the development of complex and costly 3D finite element analyses to calculate more accurate SIFs, and still resulting in small apparent limiting defect sizes based on initiation at the surface point.

Analysis has been carried out along with supporting materials testing, to demonstrate that the increased SIF at the surface point is offset by a reduction in crack-tip constraint, such that the material exhibits a higher apparent fracture toughness. This enables a more simplistic assessment which reduces the effective SIF at the surface such that only the SIF at the deepest point needs to be considered. This then leads to larger calculated limiting defect sizes. This in turn leads to a more robust demonstration of structural integrity, as the limiting defect sizes are consistent with the capability of non-destructive examination techniques.

The high SIF at the surface location, and the concomitant reduction in crack-tip constraint, meant that it was not possible to demonstrate the material response with conventional tests, such as those using shallow-notched bend specimens. Instead it was necessary to develop modified specimens in which semielliptical defects were introduced into a geometry which replicated the notch acuity at the root of a screw thread. These feature tests were used to demonstrate the principle, prior to testing with more conventional specimens to fit more accurately the parameters required to represent the material response in a defect tolerance assessment.

Margins in defect tolerance assessments are usually measured against the initiation of tearing, even though the final failure for the material may occur at a higher load following stable crack extension. This work measured and assessed the benefit of reduced crack-tip constraint on both the point of initiation and on the development of the tearing resistance curve. This demonstrated that the effect of constraint was valid with tearing for this material and that there was additional margin available beyond the onset of tearing. The feature test geometry also provided evidence of the tearing behaviour at the surface and deepest points of a surrogate component under representative loading.

This paper provides an overview of the range of tests performed and the post-test interpretation performed in order to provide the R6 α and k constraint parameters.
Fracture Mechanics at Elevated Loading Rates in the Ductile to Brittle Transition Region
Authors: Mayer Uwe , Reichert Thomas , Tlatlik Johannes
Published: October 2017

The rate-dependent reference temperature T0,x characterizes the fracture toughness of ferritic steels at the onset of cleavage. Fracture toughness values KJc,d were determined according to the Annex A1 of ASTM E1921 [1] which refers to the high rate annexes A14 and A17 of ASTM E1820 [2].

Results of extensive dynamic fracture toughness experiments at various loading rates, temperatures, specimen types and sizes revealed shortcomings in the transferability of the shape of the Master Curve under quasi-static conditions to elevated loading rates. In particular, the quasi-static Master Curve predicts lower fracture toughness values towards higher temperatures than experimentally observed under dynamic loading causing a steeper Master Curve shape.

Fractographic examinations proved the relevance of local crack arrest under dynamic loading conditions, which is consistent with the view of the parallelism of dynamic fracture probability and probability of arrest.
Validation of Fatigue Models for ERW Seam Weld Cracking
Authors: Young Bruce A. , Olson Richard J. , O’Brian Jennifer M.
Published: October 2017

In response to the National Transportation Safety Board (NTSB) Recommendation P-09-1, the Department of Transportation (DOT) Pipeline and Hazardous Material Safety Administration (PHMSA) initiated a comprehensive study to identify actions that could be implemented by pipeline operators to significantly reduce longitudinal seam failures in electric resistance weld (ERW) pipe. As part of the project, Task 4 in Phase II was designed to validate existing failure prediction models and, where gaps exist, refine or develop these models needed to assess and quantify defect severity for cold welds, hook cracks, and selective seam weld corrosion (SSWC) (the primary ERW/Flash Weld seam threats) for failure subject to loadings that develop both during hydrotests and in service. These models would then be used to develop software to support integrity management of seam welds with enough flexibility to benefit from the experience gained during this project.

The purpose of this paper is to review the models used for fatigue crack growth rate (FCGR) calculations. Both the Willenborg Model, which is used to incorporate the retardation of crack growth after an overload occurs (such as a hydrostatic test in a pipeline), and the Walker Model, which is used to account for variation in stress ratio during the operation of a structure (i.e. pressure cycles in a liquid pipeline), will be discussed. Laboratory fatigue crack growth rate test results on several grades of pipe will be used to generate the constants employed in these models.

The reports generated during the course of the project are publicly available and are located on the following PHMSA website: http://primis.phmsa.dot.gov/matrix/PriHome.rdm?pri=390.
An Assessment of the Safety Factors and Uncertainties in the Fatigue Rules of the RCC-M Code Through the Benchmark With the EN-13445-3 Standard
Authors: Métais Thomas , Courtin Stéphan , Triay Manuela , Billon François , Duranton Pascal , Briot Rudy , Bridier Florent , Gourdin Cédric , Luciani Jean-Pascal
Published: October 2017

The RCC-M code [1] is a well recognized international code and provides rules for the design and the construction of mechanical equipment for pressurized water reactors. It is used today for the nuclear industry exclusively, in countries such as France, South Africa and China and it is the basis for the design of the UK EPR to be built in Hinkley Point. The RCC-M code’s fatigue rules emanate from the ASME Boiler and Pressure Vessel Code and are hence very similar, albeit they have evolved in their own way over time to include some R&D results and other evolutions. These rules are published by AFCEN which involves a wide range of international organizations from the nuclear industry such as Apave, Areva, Bureau Veritas, CEA, DCNS, EDF, EDF Energy, ONET-MHI, Rolls-Royce and Westinghouse.

The EN-13445-3 [2] is a European standard which is mostly in use today in the conventional industry. Its fatigue rules are a compilation of rules from various national European codes, such as the German AD-Merkblatt, the British Standards, the Eurocodes for civil works and the French CODAP. The rules for fatigue are compiled in Chapters 17 and 18 of EN-13445-3 and have been the result of the work of contributors from major European organizations from the nuclear, oil and gas, chemical and mechanical industries: these include, among others, Areva, the Linde Group, CETIM, TÜV, and the TWI (The Welding Institute).

Since the beginning of 2015, AFCEN has created a technical Working Group (WG) on the topic of fatigue with the objective of identifying the Safety Factors and Uncertainties in Fatigue analyses (SFUF) and of potentially proposing improvements in the existing fatigue rules of the code. Nevertheless, the explicit quantification of safety factors and uncertainties in fatigue is an extremely difficult task to perform for fatigue analyses without a comparison to the operating experience or in relation to another code or standard. Historically, the approach of the code in fatigue has indeed been to add conservatism at each step of the analyses which has resulted in a difficult quantification of the overall safety margin in the analyses.

To fulfill its mission, the working group has deemed necessary to lead a benchmark with the EN-13445-3 standard given its wide use through other industries. Two cases were identified: either the comparison with EN-13445-3 is possible and in this case, the identification of safety factors and uncertainties is performed in relation to this standard; either the comparison is not possible, in which case the overall conservatism of the RCC-M code is evaluated in relation with operating experience, test results, literature, etc...

This paper aims at describing the overall work of the group and focuses more specifically on the results obtained through the benchmark with the EN-13445-3 standard.
Bayesian Analysis of Expert Elicitation Responses for Life Cycle Management Replacement Probability Estimates
Authors: Cluever Joseph , Esselman Thomas , Harvey Sam
Published: October 2017

In 2014, the Integrated Life Cycle Management (ILCM) computer code was developed through collaboration between the Electric Power Research Institute (EPRI) and Électricité de France (EDF) to provide a standard methodology to support effective decision making for the long-term management of selected station assets. In order for the ILCM program to become a standard tool in the industry, additional work was needed in the development of a Likelihood of Replacement (LoR) calculator. The LoR calculator estimates the likelihood that a component will have to be replaced due to failure or reasons other than failure, such as high maintenance cost, inability to maintain, obsolescence, and other similar reasons. Expert elicitation was chosen as the method of gathering data and opinions on component replacement probabilities.

The majority of expert elicitation techniques consist of experts giving opinions on the probability of replacement at various points in time, from which a reliability curve can be calculated. Furthermore, any failure or replacement data is subjectively incorporated in to the expert’s opinion.

The present work uses Bayesian analysis to provide an objective method for statistically combining expert opinion with failure and replacement data. This paper also describes the process of extracting a Weibull LoR curve from expert’s opinions and reported failures and replacements. The expert’s work history and answer confidence is used to assign uncertainty in their answers and calculate 5th, 50th, and 95th percentile credibility Weibull curves for the probability of replacement.
Assessment of the Influence of Central and Lateral Feed Injection Systems on the Remaining Life of Coke Drums
Authors: Vivas Gabriel A. , Moret Armando J. , Bello Roberto E. , Melian Luis M. , Carmona Jose R.
Published: October 2017

Coke drums are thin walled pressure vessels that are subjected to severe thermal cyclic operation, which causes low cycle thermal fatigue. Because of that, they are considered as the vessels with the highest failure rate in a refinery according to API survey conducted in1996.

In the last decade, a new technology in bottom blocking valve systems for coke drums has been introduced which induces a change in the traditional center feeding system to lateral feeding system; basically with the main goal to increase operators safety. Taking into account the mechanical integrity and remaining life of coke drums, the central feeding system has traditionally been considered as the best option, however; this hypothesis has not been fully demonstrated.

Two central fed coke drums were heavily instrumented with strain gauges and thermocouples in bulged zones identified after performing a bulge severity analysis (BSA). Thermocouple arrays and several strain gauges were installed in eight specific locations of the drums. This instrumentation was installed three months before installing bottom blocking valves in the drums, and consequently, changing their feeding system to lateral. A statistical analysis was performed using 40 thermal cycles of the two coke drums with central feeding system and 120 thermal cycles of the same coke drums after changing to lateral feeding system. The usage factor was estimated for each cycle considering the axial stress amplitude and a fatigue strength reduction factor of 2 for the ASME S-N design curve Fig. KD-320.2. Finally, the remaining life was estimated for each instrumented zone taking into consideration that the coke drums would have the same cumulative damage in the future.

The results show that average remaining life at instrumented zones (considering all locations) of one coke drum increased when the lateral feeding system was introduced; while the average remaining life at instrumented zones for the second coke drum remained practically unchanged after the lateral feeding system was put in to service.
Verification of the EPP Code Case for Strain Limits Evaluations by Inelastic Analysis Method
Authors: Messner Mark C. , Sham T.-L. , Jetter Robert I.
Published: October 2017

An ASME Section III Division 5 code case, N-861, for the evaluation of strain limits based on the elastic-perfectly plastic (EPP) methodology has recently been published. A key feature of the EPP methodology is the application of the EPP finite element analysis method with a pseudo yield stress to bound component response under elevated temperature cyclic service. The simplified inelastic approach in Division 5, Appendix HBB-T that is based on the elastic analysis results is not applicable at the elevated temperature range where creep and plasticity cannot be distinguished and unified viscoplastic model is required to describe the deformation behavior. The EPP strain limits code case overcomes such limitations. It also has the distinct advantage that stress classification, which is required by the simplified inelastic approach, is not needed. Thus, it is ideally suited for modern-day finite element technology. The conservatism of the EPP strain limits code case was verified for some simple geometries. In this paper, a viscoplastic constitutive model calibrated to the experimental data for 316H stainless steel is used to conduct a full inelastic analysis. The calculated strain accumulation is compared with that obtained from using the EPP code case approach.
A Case Study of a Cooling Pipe for a Pre-Cooler Used in a 70-MPa Hydrogen Station
Authors: Okazaki Saburo , Matsunaga Hisao , Hamada Shigeru , Nakamura Masami , Itoga Hisatake , Matsuoka Saburo
Published: October 2017

A case study was conducted on the cooling pipe of a precooler which had been used in a 70-MPa hydrogen station demonstration project. The cooling pipe consisted of a main pipe, a mechanical joint pipe and a mechanical joint. The main and mechanical joint pipes had been joined using TIG welding. Through chemical composition analysis, microstructure observation and Vickers hardness measurement, it was revealed that the main and mechanical joint pipes had been manufactured from SUS316L and that 316L was the filler metal used for TIG welding. Round-bar specimens were machined out of the main pipe in order to investigate the tensile properties of the base metal. On the other hand, both round-bar specimen without reinforcement and square-bar specimens with reinforcement were fabricated from the weld-joint. Using the three types of specimens, slow strain rate tensile tests were performed in 0.1 MPa nitrogen gas and in 115 MPa hydrogen gas at a temperature of −40 °C. Reduction of area (RA), φ, for the round base-metal specimen, the round weld-joint specimen and the square weld-joint specimen were respectively, 83.5 %, 71.3 % and 81.4 % in nitrogen gas, whereas the related values in hydrogen gas were 60.1 %, 61.3 % and 40.1 %. In other words, the RA for the three types of specimens was smaller in hydrogen gas than in nitrogen gas. Dimples were formed on the fracture surfaces of the three specimen types in nitrogen gas, whereas both dimples and quasi-cleavages were formed in hydrogen gas.
Determination of Target Bolt Tension for Flanges With Lens Gaskets
Authors: van Zyl Gys
Published: October 2017

A lens gasket is a specific type of metallic ring gasket that is usually only deployed in high pressure gas applications where a high integrity bolted flange joint is required. Lens gaskets are not common in ASME design and there are no ASME rules that guide the design of flanges with lens gaskets, nor are there ASME standards to control lens gasket specifications.

Lens gaskets present a special challenge when determining target bolt tension values for flange assembly. For calculating target bolt tension, the gasket seating width is an important parameter. With lens gaskets, the gasket seating width depends on the applied bolt tension, therefore calculation of bolt tension is by nature an iterative process. In these flange joints, the lens gasket has spherical machined surfaces that are in contact with conical gasket seats in the flanges. At low bolt tensions, gasket contact is nearly equivalent to line contact. At high bolt tensions, finite contact widths are developed, sometimes involving plastic deformation of the gasket.

This paper will present a method that was developed to determine target bolt tension for a lens gasket bolted flange. Reference will be made to European standards that address lens gaskets, and the results of finite element analysis studies that were used to validate the calculation method will be presented. The successful deployment of the outcome of this work for all the lens gasket flange joints on a plant will be discussed.
How an Experienced Fabricator Can Provide Support to Site Activities to Upgrade Existing Units to New Operational Requirements
Authors: Sabattoli Luca , Poddighe Salvatore
Published: October 2017

Some examples how an experienced fabricator can manage in-field alteration of critical equipment in order to satisfy new customer needs are presented and relevant implications evidenced.

1) Site modification of a Cr-Mo-V Reactor

A high thickness, large diameter 2.25Cr-1Mo-0.25V Hydrocracker Reactor was completed in field by performing three circumferential seams and related LPWHT. Since the Customer decided to modify the process and to add a new catalyst bed, design changes were implemented to add a new catalyst bed and a new 8” quench nozzle.

2) Rehabilitation of existing Reactor

An existing reactor no more in operation for several years was rehabilitated in field to comply with a new process unit layout (debottlenecking) to comply with current law requirements.

3) Site Assistance during schedule Turnaround activities

Reactors are designed for extended life cycle up 25 to 30 years, but severe operating conditions may require reconditioning after onsite inspection during scheduled turnaround.

Fabricator has been involved jointly with End User and Process Licensor for design changes and has responsible for the onsite execution activities.
Structural Health Monitoring for Local Damages of RC Walls Using Piezoceramic-Based Sensors Under Seismic Loading
Authors: Liao Wen-I , Jean Wen-Yu
Published: October 2017

Structural health monitoring of reinforced concrete (RC) structures under seismic loads have recently attracted dramatic attention in the earthquake engineering research community. In this study, reversed cyclic loading test of structural health monitoring of RC shear walls using piezoceramic (PZT)-based sensors are presented. The piezoceramic-based sensors called “smart aggregate (SA)”, was pre-embedded before casting of concrete and adopted for the structural health monitoring of the RC shear wall under seismic loading. Two RC walls were adopted in this test, one is the wall having damages in the boundary columns and foundation of the specimen, and the other is the wall having damages in the upper part of the wall panel. During the test, SAs embedded in the foundation were used as actuators to generate propagating waves, and the other selected SAs were used to detect the waves. By analyzing the wave response, the existence and locations of cracks and damages can be detected and the severity can be estimated. The experimental results demonstrate the sensitiveness and the effectiveness of the piezoceramic-based approach in the structural health monitoring and the identification of damage locations of shear governed concrete structures under seismic loading.
Vibration Control of Piping Systems and Structures Using Tuned Mass Dampers
Authors: Rechenberger Sven , Mair David
Published: October 2017

Vibrations of piping systems and structures pose significant operational and commercial risks. Due to their inherently low mechanical damping, these systems exhibit resonance frequencies with high dynamic amplification factor. When subject to external forces from flow turbulences, pressure pulsation or mechanical equipment, these systems can respond with large amplitude vibration. Tuned mass dampers (TMD) provide effective means of controlling resonant vibration and offer two major advantages compared to other vibration control means: Firstly, the vibration reduction can be accurately predicted even if the forcing function remains unknown, leading to increased reliability of the proposed solution. Secondly, the need for hot work during installation can be avoided, resulting in reduced safety risks and less disruption to plant operations. Although TMDs are widely used in civil and mechanical engineering, they are not commonly considered when controlling vibrations in the piping industry. One reason for this may be the absence of industry design guidelines. This paper provides simple mathematical models for the design and analysis of TMDs using Microsoft Excel spreadsheet calculations. A method for the approximation of mechanical systems’ dynamic behavior based on site measurements or finite element analyses is described, and practical guidance for the TMD design process provided. A series of examples shows how TMDs can be optimized to provide robust control of resonant vibrations.
An Analytical Approach for Strain Analysis of Buried Steel Pipeline in Mining Subsidence Areas
Authors: Xia Mengying , Zhang Hong
Published: October 2017

Mining subsidence is one of the typical geological hazard threats for long distance oil and gas pipeline. Pipelines in subsidence areas will encounter complex load conditions, which probably will lead to rupture or local buckling failure. An analytical strain calculation model for steel pipeline in mining subsidence areas was proposed. Accuracy of the model was validated by comparing with the finite element results. Based on the proposed model, parametric study was conducted to investigate the influences of main effect factors on the pipe strain. Results show that, the maximum compressive strain occurs in the middle of the subsidence area, and the maximum tensile strain occurs on the edge of the subsidence area. Axial strain of the pipeline in the subsidence area increases with the increase of overlying strata stiffness, strike length and mining depth. But the mining thickness has a negligible effect on the axial strain. The increase of operating pressure, buried depth and pipe-soil interaction reduction factor will increase the axial strain, while a larger pipe wall thickness will induce a smaller axial strain.
Buckling Behavior of Buried High Strength Steel Pipeline Under Compression Strike-Slip Fault Movement
Authors: Liu Xiaoben , Zhang Hong , Xia Mengying , Li Meng
Published: October 2017

Active fault is the most dangerous natural hazards of buried steel pipelines, as large stress and strain induced by ground movement can lead to pipe failure, which may cause severe accidents. Based on nonlinear finite element method, local buckling behavior of buried high strength X80 steel pipelines under compression strike-slip fault was studied systematically. Accuracy of the numerical model was validated by previous full scale experimental results. A baseline analysis was performed to elucidate the local buckling phenomenon of pipe. Parametric analysis was also performed to investigate the effects of influence factors of pipe’s buckling behavior. Results shows that, when local buckling occurs, axial section force decreases abruptly. When pipe-fault intersection angle equals 135°, the maximum axial section force peaks and the critical fault displacement is the smallest. With the increase of pipe wall thickness, the maximum axial section force and the critical fault displacement increases. With the increase of pipe internal pressure, the maximum axial section force and the critical fault displacement decreases. When p = 0MPa, inward-diamond buckling occurs in the pipe. While p≥4MPa, elephant-foot buckling occurs in the pipe.
Tribological Analysis of Thermal Spray Coatings of Ni and Al2O3 With Dispersion of Solid Lubricants in Wear Modes
Authors: Christy John V. , Mourad Abdel-Hamid I. , Tiwari Sudhir
Published: October 2017

In the present work, Ni and 60 wt. % of Al2O3, as thermal spray was mixed in 2:1 proportion with entrapped solid lubricant such as PTFE and Graphite through a D-Gun on the Bakelite used as substrate. For that, the specimen was taken and cleaned properly and coated with thermal spray and solid lubricating coatings of 0.5 micrometre thickness. At elevated temperatures, NiAl2O3 a common thermal spray coating protects the solid lubricants entrapped in it and thus causes the layer to be stable and dynamic. The solid lubricants mixed in thermal spray were graphite and PTFE. These were then ultrasonically cleaned in the acetone bath. The coating is done by a duo spray pump that spurts the coating on the work piece. This pump spurting is controlled by a semi permeable membrane coated on the work piece. Coatings were tested at different air pressure, temperature and impingement angle. It was found that the degradation of coating was observed on low impingment angles and also with the reciprocating stress inputs. The Graphite and NiAl2O3 coating is found to be more stable tribologically as compared to PTFE and NiAl2O3 coating at high temperatures and pressures. Morphological analysis of coatings was also done. The coating was tested on cutting tool ends like drill bits, planar cutting tool and turning tools. Separate analysis was carried out on erosive wear, abrasive wear, temperature and pressure with varied load conditions on the coatings done on Bakelite. On all the individual tests done Graphite and NiAl2O3 mix coating was found stable.

This coating finds much more application in pipes and pressure vessels systems. The inside bore of a pipe can be coated similarly which will smoothly transfer the abrasive sludge or fluids with much reduction on its friction coefficient.
Numerical Simulation of Seismic Risk and Loss Propagation Effects in Process Plants: An Oil Refinery Case Study
Authors: Caputo Antonio C. , Vigna Alessandro
Published: October 2017

Process plants are vulnerable to natural hazards and, in particular, to earthquakes. Nevertheless, the quantitative assessment of seismic risk of process plants is a complex task because available methodologies developed in the field of civil and nuclear engineering are not readily applicable to process plants, while technical standards and regulations do not establish any procedure for the overall seismic risk assessment of industrial process plants located in earthquake-prone areas. This paper details the results of a case study performing a seismic risk assessment of an Italian refinery having a 85,000 barrels per day production capacity, and a storage capacity of over 1,500,000 m3. The analysis has been carried out resorting to a novel quantitative methodology developed in the framework of a European Union research program (INDUSE 2 SAFETY). The method is able to systematically generate potential starting scenarios, deriving from simultaneous interactions of the earthquake with each separate equipment, and to account for propagation of effects between distinct equipment (i.e. Domino effects) keeping track of multiple simultaneous and possibly interacting chains of accidents. In the paper the methodology, already described elsewhere, is briefly resumed, and numerical results are presented showing relevant accident chains and expected economic loss, demonstrating the capabilities of the developed tool.
An Optimization Framework for Curvilinearly Stiffened Composite Pressure Vessels and Pipes
Authors: Singh Karanpreet , Zhao Wei , Kapania Rakesh K.
Published: October 2017

With improvement in innovative manufacturing technologies, e.g. automated tow-placement, it is now possible to fabricate any complex shaped structural design for practical applications. This innovative manufacturing technology allows for the fabrication of curvilinearly stiffened pressure vessels and pipes. Compared to straight stiffeners, curvilinear stiffeners have been shown to have better structural performance and weight savings under certain loading conditions. In this paper, an optimization framework for optimal structural design for curvi-linearly stiffened composite pressure vessels and pipes is presented. Non-Uniform Rational B-Spline (NURBS) curves are utilized to define curvilinear stiffeners over the surface of the pipe. An integrated tool using Python, NURBS-based Rhinoceros 3D, MSC.PATRAN and MSC.NASTRAN is implemented for performing topology optimization of curvilinearly stiffened cylindrical shells. Rhinoceros 3D is used for creating the geometry, which later can be exported to MSC.PATRAN for finite element model generation. Finally, MSC.NASTRAN is used to perform structural analysis. A hybrid optimization technique, consisting of Particle Swarm Optimization (PSO) and Gradient Based Optimization (GBO), is used for finding the optimized locations of stiffeners, optimal geometric dimensions for stiffener cross-sections and the optimal layer thickness for the composite skin. Optimization studies show that stiffener placement influences the buckling mode of the structure. Furthermore, the structural weight can be decreased by optimizing the stiffener’s cross-section and skin thickness. In this paper, a cylindrical pipe stiffened by orthogonal and curvilinear stiffeners under internal pressure and bending load is studied. It is shown that curvilinear stiffeners lead to a potential 8% weight saving in the composite laminated skin as compared to the case of using straight stiffeners.
Assessing Advanced Test Reactor Process States Using Acoustic Measurement Infrastructure
Authors: Agarwal Vivek , Smith James A.
Published: October 2017

The core of any nuclear reactor presents a particularly harsh environment for sensors and instrumentations. The reactor core also imposes challenging constraints on signal transmission from inside the reactor core to outside of the reactor vessel. In this paper, an acoustic measurement infrastructure installed at the Advanced Test Reactor (ATR), located at Idaho National Laboratory, is presented. The measurement infrastructure consists of ATR in-pile structural components, coolant, acoustic receivers, primary coolant pumps, a data-acquisition system, and signal processing algorithms. Intrinsic and cyclic acoustic signals generated by the operation of the primary coolant pumps are collected and processed. The characteristics of the intrinsic signal can indicate the process state of the ATR (such as reactor startup, reactor criticality, reactor attaining maximum power, and reactor shutdown) during operation (i.e., real-time measurement). This paper demonstrated different in acoustic signature of the ATR under different operating conditions. In particular, ATR acoustic baseline is captured during typical operation cycle and during power axial locator mechanism operation cycle. The difference in two acoustic baseline is significant and highlights salient difference that are critical in the design and development of acoustically telemetered sensors.
R5 Code Based Creep Analysis of a Thick-Wall Cylinder With Steam Film Cooling Hole Structure
Authors: Cai Zhenwei , Wang Weizhe , Hong Hui , Liu Yingzheng
Published: October 2017

The study presented here designed a steam film cooling system for the thick-wall cylinder components used in the 700°C steam E turbine power plant, and investigated temperature, thermal stress, and creep behavior of the thick-wall cylinder with the cooling hole structure. Analysis of film cooling behavior with a single cooling hole at different blowing ratios is numerically conducted to determine the design of a steam cooling system with multiple cooling holes. Boththe temperature and stress analysis of the thick-wall cylinder with either a single cooling hole or multiple cooling holes are performed for comparison. The British R5 guidance procedure is applied to assess the creep damage of the component after 200,000 h operation. Maximum creep damage dc is approximately 0.0008 at the leading edge of the cooling hole in Row 1.