bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on Failure Behavior of Two-Elbow Piping System Models Made of the Simulation Material Under Excessive Seismic Loads
Authors: Nakamura Izumi , Kasahara Naoto
Published: October 2020

To investigate the failure behavior of piping systems under excessive seismic loads, shaking table tests on piping system models made of a simulation material have been executed. The simulation material adopted in the experiment was lead-antimony (Pb-Sb) alloy. The piping system model was composed of two elbows made of Pb-Sb alloy, one additional mass, and two fixed anchors. Input motions were sinusoidal wave. The failure modes of the piping system were examined by varying the additional mass and frequency of the input sinusoidal wave.

Through the excitation tests, the failure mode which was named as “ratchet and subsequent collapse” was obtained successfully. The result which was classified as “no failure after 500 cycles” was also obtained. It was found that the occurrence of the failure depended on the ratio of the input frequency to the specimen’s natural frequency, and the ratio of additional mass weight to the limit mass weight. Though the effect of higher modes on the failure behavior was necessary to be more investigated, it seemed that the tendency of dominant failure behavior was similar to that of the single-elbow specimen investigated in the previous study.

Moreover, it was confirmed that the experimental approach to use a simulation material was applicable for piping system model with multiple elbows.
Cracking Behavior of a Decommissioned Material in Light Water Reactor Environment
Authors: Chen Y. , Alexandreanu B. , Rao A. S.
Published: October 2020

The performance of structural materials is critical for the safe and economic operation of light water reactors. During power operation, reactor core internal materials are exposed to aggressive corrosive coolant environment, vigorous thermal/mechanical loading, and intensive neutron irradiation. Such severe service conditions can activate and enhance a wide range of degradation processes, leading to deteriorated material properties and service performance. To ensure the structural integrity and functionality of nuclear reactor components, material degradation and damage mechanisms must be understood and managed adequately. It has been recognized that there are knowledge and data gaps in the existing information and technical bases for long-term operation and aging management. In particular, post-irradiation data on fracture toughness and crack growth rate are lacking. In this work, irradiated materials harvested from a decommissioned reactor are studied for their cracking susceptibility and fracture resistance as a function of irradiation dose. The materials are a Type 304 stainless steel sectioned from the baffle plates of a pressurized water reactor after 38 years of service. Miniature compact-tension specimens about 6.5-mm thick are machined from these materials with different levels of irradiation damage, ranging from < 1 to ∼50 dpa depending on the original locations with respect to the reactor core. Crack growth rate and fracture toughness J-R curve tests are performed in a low-corrosion-potential environment at ∼315°C. All samples behave similarly under cyclic loading, and no deteriorated corrosion fatigue behavior can been seen in the test environment. Under constant loads, most of samples show no elevated crack growth rates, suggesting an adequate stress corrosion cracking resistance for these irradiated samples in the test environment. An unstable cracking behavior was observed occasionally where step-wise crack advances upon load increases can be seen. The effect of neutron irradiation is evident on fracture toughness. With the increasing dose, the J-R curve declined constantly, and became very shallow at high doses. It is evident that this baffle plate material has been severely embrittled by neutron irradiation. In addition, an unexpected fully IG morphology has been observed for the all high-dose samples fractured at room temperature in air atmosphere. The occurrence of this brittle fracture in the absence of aggressive environment confirmed a high degree of embrittlement of this material resulting from its service exposure to neutron irradiation.
Finger Flange Designs on Cast Equipment
Authors: Shitole Bhaskar , Heinrichs Cynthia
Published: October 2020

Piping systems connecting critical equipment such as pumps with non-standard flanges should be designed so that all components have compatible strength. One such non-standard flange design is the so-called finger flange, used on the discharge flanges of large pumps. A finger flange uses slots instead of holes for the bolts. This design is common for certain types of equipment in use today, such as large slurry and water pumps.

In this study, finite element analysis is used to model a finger flange bolted to a standard ASME B16.5 weldneck flange and understand the areas of weakness in the overall joint. Seating stresses caused by bolt load are calculated as well as stresses experienced by the joint during operation with additional pressure applied. Stresses are compared for the region of highest stress at the junction of the hub to the pipe shell. Various aspects of the geometry are modified to evaluate the effect on flange stress.

The slots were found to have minimal effect on flange stress. Increasing the wall thickness reduces the stress in the finger flange. Bolting the finger flange to a thicker standard flange increases the stress in the finger flange. Uneven bolting was simulated by tightening a bolt and leaving the surrounding bolts loose. In this situation the finger flange experienced significantly higher stress than a standard flange exposed to the same uneven load. Gasket stress and displacement were similar between a finger flange joint and a standard joint.
Effect of Glaze Composition on the Corrosion Resistance of Glass Lining of Glass-Lined Pressure Vessels
Authors: Xu Jin-Sha , Tang Chen-Huai , Chen Yi , Ren Fa-Cai , Si Jun , Ding Ju , Zhang Pu-Gen , Yang Yu-Qing , Du Yan-Nan , Han Shou-Peng
Published: October 2020

Glass-lined pressure vessels are widely used in various corrosion conditions because of their excellent corrosion resistance. Under the same firing process condition, the corrosion-resistant properties of glass-lined vessels are largely dependent upon the glaze composition. In this paper, three kinds of glazes were selected to study the corrosion resistance to acid and alkali of the glass lining. Based on the glaze composition analysis, the corrosion quantity and the micromorphology observations of the corroded surfaces, the effect of glaze composition on the corrosion resistance to acid and alkali of glass lining was discussed. The results showed that the corrosion resistance of glass lining was mainly to the content of SiO2 and the continuity level of [SiO4] skeleton in glass network structure. The higher continuity level of [SiO4] skeleton led to the better physicochemical properties of the glass lining. The addition of the acid resistant oxide TiO2 improved the acid resistance of glass lining. The proper addition of ZrO2 improved the corrosion resistance to acid and alkali. There were two reasons, one of which was that the joining of Zr4+ into the glass network improved the structural integrity, and the other was that the reaction of Zr4+ with OH− produced Zr(OH)4 on the glass lining occurred and formed a shielding lining against alkali when glass lining was in the alkaline condition.
Application of Nonlinear Parameters Predictive Model Based on LS-SVM in Pipeline of Mixed Transportation
Authors: Li Xue , Shi Lei
Published: October 2020

In order to meet the refinery’s requirements on the properties of raw materials, improve the hydraulic stability of pipeline transporting process, and reduce the energy consumption, it’s necessary to mix up different crude oils transported in pipeline. The traditional method to obtain the physical properties of mixed crude oil, especially the nonlinear parameters such as viscosity and pour point, is experiment test or empirical formula, but the disadvantage is the heavy workload or limited use conditions. In this paper, a nonlinear parameters prediction model based on LS-SVM is put forward for transporting mixed crude oil in pipeline. The modeling method of the nonlinear parameters prediction based on LS-SVM : 1 normalize the different batch sample data; 2 the kernel function of SVM is Gaussian RBF; 3 regress coefficients by genetic algorithm; 4 train parameters and then obtain the nonlinear parameters prediction model. The nonlinear parameters prediction model based on LS-SVM has superiority in aspects of reliability, modeling efficiency, universality and adaptability. It can adapt to the dynamic requirements of refinery on crude oil properties, make full use of the accumulated mixed crude oils’ physical properties and their mixing ratio. The prediction accuracy of non-linear parameters model can be improved continuously. And then, the rationality and efficiency of online mixed transportation in pipeline can be improved effectively.
Elephant Foot Buckling Analysis of Large Unanchored Oil Storage Tanks With Tapered Shells Subjected to Foundation Settlement
Authors: Shi Lei , Wang Xiaolin , Chang Liang , Li Xue
Published: October 2020

This paper presents an numerical study on a large unanchored open-topped steel tank. The buckling behaviors of the tank are analyzed using the finite element computer package ANSYS by means of nonlinear stabilization algorithm. The effects of foundation harmonic settlement on the elephant foot buckling strength of large unanchored open-topped oil storage tanks with tapered shells under axial compression are explored by numerical modeling. Various items of actual geometrical structure which involve concrete ringwall foundation of tank, unanchored bottom with slope, shell tapering from the base to the top, wind girders and supports, top angles, stiffening rings and support plates are presented thoroughly in the non-symmetrical 3D finite element model. Geometric nonlinearity, nonlinear boundary conditions and elastic plastic material of Ramberg-Osgood model are involved simultaneously in simulate course. The obtained solutions are displayed graphically for selected values of system parameters: harmonic settlement amplitude, harmonic number, and critical buckling stress of axially compressed oil tank. The results will provide insights into the relationship between foundation harmonic settlement and buckling strength of the large cylinders.
Diagnosis of Corrosion Processes in Nuclear Power Plants Secondary Piping Structures
Authors: Manjunatha Koushik A. , Mack Andrea , Agarwal Vivek , Koester David , Adams Douglas
Published: October 2020

The current aging management plans of passive structures in nuclear power plants (NPPs) are based on preventative maintenance strategies. These strategies involve periodic, manual inspection of passive structures using nondestructive examination (NDE) techniques. This manual approach is prone to errors and contributes to high operation and maintenance costs, making it cost prohibitive. To address these concerns, a transition from the current preventive maintenance strategy to a condition-based maintenance strategy is needed. The research presented in this paper develops a condition-based maintenance capability to detect corrosion in secondary piping structures in NPPs. To achieve this, a data-driven methodology is developed and validated for detecting surrogate corrosion processes in piping structures. A scaled-down experimental test bed is developed to evaluate the corrosion process in secondary piping in NPPs. The experimental test bed is instrumented with tri-axial accelerometers. The data collected under different operating conditions is processed using the Hilbert-Huang Transformation. Distributional features of phase information among the accelerometers were used as features in support vector machine (SVM) and least absolute shrinkage and selection operator (LASSO) logistic regression methodologies to detect changes in the pipe condition from its baseline state. SVM classification accuracy averaged 99% for all models. LASSO classification accuracy averaged 99% for all models using the accelerometer data from the X-direction.
Evaluating the Performance of Engineered Enclosures for Piping Repairs
Authors: Halligan Troy , Vyvial Brent , Rodery Clay , Thistlethwaite Adam , Subramanian Kannan
Published: October 2020

Engineered enclosures for the repair of piping, often referred to as clamps, are used to restore the integrity of in-service piping components as an interim measure until the damaged components can be repaired. They are typically used in the petroleum refining and chemical process industries, nuclear and non-nuclear utilities, and other on-shore and offshore facilities in the oil and gas industry. This type of enclosure has typically been viewed as a short term repair with a limited design life. However, it is the authors’ experience that properly engineered and installed enclosures perform in a manner consistent with the design criteria covering the original piping component(s) to which they have been installed. To investigate this further, a series of tests were conducted on several engineered enclosures that had been recently removed to replace the damaged component. Tests were also conducted on several new constructed enclosures of a similar configuration and size to those that had been recently removed. An analytical approach was also performed on one such enclosure-pipe configuration to support and study the experimental results in detail. This paper presents and summarizes the tests, analyses, and results from this work. The results provide information that can benefit users, standards developers, and regulatory authorities in better understanding the considerations affecting the design life of engineered enclosures.
Comparison of 316LN Ratcheting Boundary at Room Temperature and 350 °C
Authors: Liu Caiming , Chen Xu
Published: October 2020

The ratcheting boundaries of 316LN austenitic stainless steel under room temperature and 350 °C were determined by efficiency curve method. The iso-cumulative plastic strain curves of the material were obtained through numerical interpolation method. It is indicated that the primary stress and secondary stress range increase with the increase of cumulative plastic deformation. Under the same cumulative plastic strain, the iso-cumulative plastic strain curve at 350 °C is higher than that at room temperature. The effective primary stress was introduced to obtain ratcheting boundary curves. The results show that the material at 350 °C has a higher ratcheting boundary compared with that at room temperature. It is indicated that, under equivalent stress condition, the bearing capacity of 316LN at 350 °C is stronger than that at room temperature. This is due to the dynamic strain aging of the material at high temperature. At 350 °C, the solid solution atoms and dislocations are pinned together, which leads to a strengthening effect on the material. The ratcheting boundary curves determined in this study are compared with relevant standards. The test results suggest that the material served in different environments should be checked by different ratcheting boundary curves.
Effect of Several Design Parameters on the Sealing Performance of Reactor Pressure Vessel
Authors: Zheng Liangang , Mi Xue , Shi Kaikai , Bai Xiaoming , Xie Hai , Zheng Bin , Yu Xiaohuan
Published: October 2020

In nuclear power plants, the sealing performance of reactor pressure vessel is highly related to the spring back properties of the seal ring installed between the closure head flange (upper flange) and the vessel flange (lower flange). In the finite element analysis, the sealing performance is usually described by the separation value of the upper and lower flange at the seal ring.

Considered the test results of spring back capability of seal ring in combination with a certain safety factor, the limitation of the separation between upper and lower flange at the seal ring is usually 0.2 mm. There are many design parameters, which have a huge influence on the sealing performance of pressure vessel, such as design size, material performance, bolt preload, etc.

As the reactor coolant loop is a complete, and highly relevant design system, some design parameters of pressure vessel changed may affect the whole system. Therefore, the effects of several design parameters on the sealing performance of the pressure vessel were analyzed in this paper. The results indicated that angle of the upper flange seal surface and the preload of the bolts have a big influence on the sealing performance of the pressure vessel, and they have nothing to do with the design of the whole system. The research results might guide the pressure vessel designers to optimize the pressure vessel design on improving the sealing performance.
The Influence of Multiaxial Stress Relaxation on Component Creep Damage Accumulation in Biaxial, Mixed Primary, and Secondary Loading on a Pipe
Authors: Matev Nayden , Ainsworth Robert A. , Su Meini , Stevens Mark , Jappy Alan
Published: October 2020

Unless detailed inelastic analysis is followed, high temperature codes base creep relaxation during a dwell period within a cycle on the start-of-dwell equivalent stress. The relaxation of the equivalent stress is then taken to be governed by a uniaxial creep law for the material being considered. Elastic follow-up is also included in such calculations. With this approach, only equivalent values of stress and creep strain rate are obtained and the stress multiaxiality is therefore assumed to remain at its initial value as the stress relaxes. The stress drop is limited to a small fraction (typically 20%) of the initial equivalent stress to ensure that this assumption does not lead to significant inaccuracy. This paper reports creep relaxation results for a pipe subjected to a combination of both primary and secondary stresses. The primary stress is generated by an internal pressure and an axial load, which enable different primary biaxial loading conditions to be generated. The secondary stress is through-wall bending in nature, produced by a through-wall temperature gradient, which influences the initial biaxial stress ratio. Several parameters are varied in order to produce relaxation behaviour in the pipe with an associated elastic follow-up. The starting biaxial stress ratio, the creep law power exponent and the amount of secondary stress result in varying degrees of elastic follow-up being present. The biaxial stress ratio is generally found to change as relaxation occurs and a multiaxial ductility approach is used to evaluate the associated effect on creep damage accumulation. This is compared with the creep damage estimated by assuming relaxation is simply controlled by the equivalent stress with no change in multiaxial stress state during relaxation. It is found that significant equivalent stress drops (up to about 40% of the initial value) can be allowed without the simplified equivalent stress approach being inaccurate. The results have been compared with a number of creep damage models to ensure that the conclusions are not sensitive to the detail of the damage model.
Parameter Sensitivity Analysis of a Beam Seal Based on a New Sealing Criterion and Orthogonal Array Method
Authors: Cui Ying , Yu Yingjia
Published: October 2020

A beam seal with an elliptical groove is proposed and parameterized. Based on the stochastic grid percolation model, macroscopic and microscopic finite element analysis, a sealing performance index is developed for the beam seal, which can consider the contact bandwidth and contact pressure synthetically. Taking the sealing performance index as the objective function, the sensitivity analysis of six main structural parameters of the beam seal is carried out by using the orthogonal array method. The orthogonal experiment with six factors and two levels is used to examine the interaction between parameter. It is found that there are parameter interactions between the length of the long axis and the short axis of elliptical groove, between taper angle and inclined angle U-shaped section, and between nominal contact width of the first seal and long axis of the elliptical groove. Furthermore, the sensitivity of each parameter on the sealing performance index of the beam seal is evaluated by the orthogonal design of L81(340) and F-test. The sensible parameters for sealing performance are obtained, and the optimal structural parameters of beam seal are suggested.
Safety Assessment of Pressure Vessels in Service for More Than 20 Years
Authors: Xuedong Chen , Zhichao Fan , Jie Dong , Zhibin Ai , Mingdong Hu
Published: October 2020

In recent years, a large number of pressure vessels for the petrochemical plants built in China in the 20th century have been in service for more than 20 years. The Chinese pressure vessel safety specification TSG 21-2016 “Supervision Regulation on Safety Technology for Stationary Pressure Vessel” stipulates that if the pressure vessels without definite design lives have been in service for more than 20 years, they shall be considered to have reached the design service lives. For these pressure vessels, if they are all blindly scrapped, it will cause huge economic losses. However, if they continue to be used blindly, it may bring great safety risks. In this paper, the failure mode, mechanism and damage evolution law are analyzed through a number of failure accident investigations and experimental studies, for typical pressure vessels such as large LPG spherical tanks, pressure swing adsorbers and coke drums. The classification method of pressure vessel for the time-independent and time-dependent failure modes has been proposed. As for the pressure vessels with time-independent failure modes, the principle to determine target life, and the strategy of inspection and maintenance have been proposed. While for the time-dependent failure modes, the safety evaluation and remaining life prediction methods for the pressure vessels with and without defects have been provided. Finally, the advices on amendment to the relevant regulations on pressure vessels have been proposed. The research findings could provide guidance for rationally determining the safety grades and scientifically extending the service lives of pressure vessels.
Volumetric Damage Modeling of High Temperature Hydrogen Attack in Steel Using a Continuum Damage Mechanics Approach
Authors: Bagnoli K. E. , Cater-Cyker Z. A. , Holloman R. L. , Hay C. A. , Chavoshi S. , Nikbin K. M. , Hill L. T.
Published: October 2020

Hydrogen attack is a degradation phenomenon that affects process equipment operated at elevated temperatures in an environment containing a high hydrogen partial pressure. It has been the subject of numerous studies over the years prompted by damage discovered during routine inspections, or incidents that have occurred in service. As non-destructive evaluation (NDE) techniques have improved, damage is being detected during earlier stages where safe operation may still be possible for some time period. This work focuses on the fitness for service evaluation of equipment containing high temperature hydrogen attack (HTHA) using a continuum damage mechanics (CDM) approach. The model can be employed to assess the loss in load bearing capacity due to damage in the form of widespread micro-fissuring and voids (i.e. up to the point of macro-crack coalescence). Experimental data from literature sources have been used to develop a relationship between damage rate and operational loading conditions. The predictions are compared to field experience to illustrate key aspects of this approach.
Fabrication of Grade 91 Materials Experience in Oil and Gas Applications
Authors: Prajapati Bhadresh A. , Penso Jorge A.
Published: October 2020

A modified 9-Cr alloy was developed by Oak Ridge National Laboratory, in early 1980s, to increase high temperature capabilities of ferritic steels for superheater tubing. The material improved high temperature creep properties by controlling alloying elements and microstructure. The material was added to ASME BPVC in 1983 (thru Code Case 1943) as Grade 91. Higher yield and tensile strength, in comparison to other low-Cr alloy steels (like Grade 22), allowed for fabrication of thinner component wall thickness. This in-turn reduced susceptibility to through-wall thermal stresses during transient events. Directionally this also reduced material costs.

Consequently, petrochemical industries have utilized Grade 91 in applications at Heat Recovery Steam Generation units (HRSG), Steam Methane Reformers (SMR), CO2 Boilers and as convection coils in Ethane conversion units.

Grade 91 material has complex microstructure and requires careful control of welding parameters to assure crack free welds that provide adequate creep ductility and retain creep strength at high temperatures. The current guidelines documented in API 582 and Technical Report 938 provide limited insights on success factors for weldability.

Grade 91 material use has been growing in the recent past Petrochemicals Complex and in offshore applications, at once-throw steam generators (OTSG). The aim of this paper is to share experience on welding parameters. Guidance needs be adjusted to specific projects and repair activities.
Failure Mode Effects Analysis for Section III, Division 5 Class A, High Temperature Service of a Printed Circuit Heat Exchanger
Authors: Jentz Ian , McKillop Suzanne , Keating Robert
Published: October 2020

The mission of the U.S. Department of Energy (DOE), Office of Nuclear Energy is to advance nuclear power in order to meet the nation’s energy, environmental, and energy security needs. Advanced high temperature reactor systems will require compact heat exchangers (CHX) for the next generation of nuclear reactor plant designs. A necessary step for achieving this objective is to ensure that the ASME Boiler and Pressure Vessel Code, Section III, Division 5 has rules for the construction of CHXs for nuclear service.

Given their high thermal efficiency and compactness, expanding the use of Alloy 800H diffusion bonded Printed Circuit Heat Exchangers (PCHEs) beyond their current application in Section VIII, Division 1 to the high temperature nuclear applications is of interest. The research being completed under the Department of Energy project is focused on preparing a draft Code Case for consideration by the ASME Code Committees for high temperature nuclear components which must meet the requirements of Section III, Division 5, Subsection HB (Class A), Subpart B.

Acceptance of a Code Case by the ASME Code Committees to use PCHEs in nuclear service requires a broad understanding of PCHE failure mechanisms. At the highest level, the ASME Code requirements prevent failures of structures and pressure boundaries. Historically, the approach is a process of understanding the known failure modes, such as overload failures, plastic collapse, progressive distortion (ratcheting) and fatigue, and then establishing rules for construction to preclude those failure modes in components. For Division 5 applications, attention to differential thermal expansion, creep life, and creep-fatigue must also be considered. Failure from these loadings is manifest within PCHEs both within the internal micro-channel geometry, and at substantially larger solid header and nozzle attachments. To address the adequacy of the PCHE, a Failure Mode Effects Analysis (FMEA) has been performed for standard etched channel PCHEs. This FMEA is linked to the proposed rules in the code case for compact heat exchangers in Section III, Division 5 Class A applications. The PCHE FMEA covers all design failures addressed by Section III.
Design and Analysis of a High Pressure Laboratory Vessel for Testing Well Cement
Authors: Prabhu Milind , Eliseev Ksenia , Vargas Pedro , Krener John , Nadakuditi Venkata , Sarzynski Melanie
Published: October 2020

The Steam Permeameter Cell is a laboratory-scale pressure vessel used to perform high pressure, high temperature testing on well cement slurries. Initial sizing of the concentric, two chamber vessel was based on design by rule concepts in the ASME Boiler and Pressure Vessel Code, Section VIII Division 1. However, based on the complex transient loading expected during the specified testing protocol, additional engineering design and analysis was performed to understand the effects of thermal gradients on the overall strength and fatigue performance of the vessel. The objective of the engineering assessment was to show compliance with design margins in the Code when non-listed materials are utilized in the construction.

Using detailed analytical modeling of transient, thermo-mechanical loading, the assessment demonstrated that the test vessel was safe to operate based on engineering judgement and established best practices in vessel design by analysis. Furthermore, several design modifications were identified to improve functionality and overall performance of the vessel. The Steam Permeameter Cell design had sufficient static capacity to contain the maximum allowable working pressure (MAWP) of 3,500 psig at a design temperature of 700°F, and fatigue capacity to withstand the intended test protocol over the service life.
Performance-Based Assessment of a Guyed Incinerator Stack Using Field Measurements
Authors: Farrow Kenny T. , Karmakar Jaideep , Subramanian Kannan
Published: October 2020

ASME STS-1 provides guidelines for the design, fabrication, and erection of steel stacks, however there are no specific guidelines for the assessment of guyed steel stacks already in service. For example, drift (i.e., displacement) acceptance criteria are only provided for initial installation. Furthermore, existing literature regarding the proper re-tensioning of guy wires is scarce or nonexistent. This procedure is particularly important for stacks that experience significant thermal growth. This effect is further exacerbated by differential wind cooling effects on both the guy wires and on the stack itself. This paper investigates the effect of guy wire spacing, position, tension pattern, and operating and shutdown tension settings on the structural response of a guyed steel stack. Field thermography readings, ultrasonic testing (UT) thickness data, guy wire tension measurements, and laser scans are used to refine a finite element model of the stack. Using elastic-plastic nonlinear “pushover” analyses based on API 579 – 1 Level 3 fitness-for-service methodology and FEMA 356 rehabilitation guidelines, a performance-based methodology resulting in a “watch circle” approach for lateral displacement is provided to guide fitness-for-service assessments and mitigation implementation. Example application of this methodology and recommendations regarding guy wire tensioning are provided for an incinerator stack with 9 guy wires (3 levels – 3 guy wire configuration).
Experimental Study on Excitation of Heat Exchanger Tubes Based on Turbulence Power Spectrum
Authors: Wang Yuqi , Tian Ce , Guo Kai , Zhu Guorui , Tan Wei
Published: October 2020

In the steam generator, anti-vibration bars are often provided to support the tube bundle. Due to the non-linearity of the support, the fluid-solid coupling simulation of large-scale tube bundles supported by the anti-vibration bars will bring great trouble. In order to solve this problem, this paper conducts experiments on the heat exchange tube based on the turbulent power spectrum to generate the excitation force. By changing the support form, the force of the lift and the direction of the drag and the ratio of the force, the excitation of the heat exchanger tube is researched. The results of the displacement response, the contact force and friction force distribution, and the contact angle distribution provide reference for the subsequent model simplification. Experiments show that the contact rate increases with the increase of the excitation force, and the contact force and the friction force increase with the increase of the excitation force. When the heat exchange tube contacts with the anti-vibration bars, the contact angle is mostly less than 45°, more than 50% of the contact angle is less than 45°. The work rate of the tube at the edge is greater than the work rate of the tube in the center.
Rank Predictions of Internal Corrosion of Gathering Pipelines in a Natural Gas Field With a Multi-Kernel SVM Method
Authors: Li Yuejiao , Zeng Weiguo , Li Xiufeng , Ren Fajun , Hu Haijun
Published: October 2020

Internal CO2/H2S corrosion of gathering pipelines is a serious problem in natural gas plant. It is important for field engineers to assess the corrosion degree and control corrosion risk. A multi-kernel support-vector-machine (SVM) method is presented to rank internal corrosion of gathering pipelines according to the NACE RP-0775-91 standard. By considering the nonlinear indivisibility between data, we combined three kinds of kernels (linear kernel, polynomial kernel, and Gaussian kernel) into a multi-kernel SVM to rank the internal CO2/H2S corrosion of gathering pipelines. The method was applied to a natural gas field in northwest China. Corrosion data were collected and analyzed. The prediction accuracy of the multi-kernel SVM method for ranking CO2/H2S corrosion was 66%, which is higher than the results of the single-kernel SVM methods (linear kernel, polynomial kernel and Gaussian kernel), whose prediction accuracies are 50%, 48% and 54% respectively. These findings could help field engineers rank corrosion and reduce the corrosion risk.
Seismic Test Results of the Main Steam Isolation Valve for Japanese Boiling Water Reactor Nuclear Power Plants
Authors: Itabashi Hideaki , Tsutsumi Yoshitaka , Nishino Koji , Kumagai Shin
Published: October 2020

The functional requirements of Main Steam Isolation Valves (MSIVs) provided in the Boiling Water Reactor (BWR) nuclear power plants in Japan have been previously evaluated via seismic tests and so forth. However, since the response acceleration has increased in line with a recent reassessment of standard earthquake ground motions, it is necessary to evaluate seismic operability with respect to high acceleration. In addition, from the viewpoint of equipment fragility in seismic PRA, it is necessary to determine practical seismic operability limits.

We used a resonant shaking table in the Central Research Institute of the Electric Power Industry (CRIEPI), which is capable of seismic tests at acceleration levels previously unachievable, and in seismic tests carried out on an MSIV, we obtained results confirming that validated seismic operability was possible even at response accelerations as high as 15 × 9.8 m/s2.

The seismic operability results obtained for this MSIV will be applied to a fragility analysis of seismic PRA.
Subsea Flanges, Comparison Between Conventional API 6A Type 6BX Flange and SPO Compact Flange Designs
Authors: Lutkiewicz Przemyslaw , Robertson David , Lee Sam (Kwok Lun)
Published: October 2020

The API flange design is a well-known commonly used solution. The flange concept was developed in late 1920s and 1930s by Waters and Taylor. The design methodology of the flange was published in 1937[1], well known as the “Taylor Forge method”. This is still the basis of the present ASME flange calculation. The design is based on the simple elastic principles and linear stress analysis/calculations. The conventional flange type dimensions are described in API 6A [2] and analyzed in API 6AF [3] and 6AF2 [4]. On the other hand, the Compact Flange concept was presented first by Webjørn in 1989 VCF joint [5]. It is based on plastic theory equations and plastic collapse capacity. In 1989 the initial concept was adopted by the Steel Product Offshore (SPO) company for oil industry by equipping flange with HX seal ring for raiser and subsea use. After that a topside budget version (with simpler IX seal ring) was prepared by SPO and presented on PVP 2002 conference [6][7][8]. The Compact Standardized and simplified flange design with IX seal ring is defined and described in ISO-27509 [9]. As for today, along ASME B.16.5 [10] pressure classes range, SPO CF 5K, 10K, 15K and 20K rating flange classes were designed and are in use. The main advantages for CF design are reliability, low weight/compact dimensions and static behavior compared to the conventional design. The design is already well known and commonly uses for European region (mostly Norway). Despite its benefits, CF is still rare outside Europe region. A comparison between those two different concepts will be presented in this paper followed by the examples and Finite Element Analysis (FEA). In case of FEA the Compact Flange design is more suited to the plastic collapse analysis than to elastic stress evaluation as it is for API, therefore comparison between different FEA approaches will be studied in addition.
Strain Control Correction for Fatigue Testing in LWR Environments
Authors: Vankeerberghen Marc , Mclennan Alec , Simonovski Igor , Barrera German , Arrieta Gomez Sergio , Ernestova Miroslava , Platts Norman , Scibetta Marc , Twite Marius
Published: October 2020

During strain-controlled fatigue testing of solid bar specimens in a LWR environment within an autoclave, it is common practice to avoid the use of a gauge length extensometer to remove the risk of preferential corrosion and early crack nucleation from the extensometer contact points. Instead, displacement- or strain-control is applied at the specimen shoulders, where the cross-sectional area of the specimen is higher and so surface stress levels are lower. A correction factor is applied to the control waveform at the shoulder in order to achieve approximately the target waveform within the specimen gauge length.

The correction factor is generally derived from trials conducted in air by cycling samples with extensometers attached to both the shoulders and the gauge length; typically, the average ratio between the strains or the ratio at half-life in these locations is taken to be the correction factor used in testing. These calibration trials may be supplemented by Finite Element Analysis modelling of the specimens, or by other analysis of results from the calibration trials.

Within the INCEFA+ collaborative fatigue research project, a total of six organizations are performing fatigue testing in LWR environments within an autoclave. Of these, one organization is performing tests in an autoclave using extensometers attached to both the specimen shoulders and the specimen gauge length. Therefore the INCEFA+ project provides a unique opportunity to compile and compare methods of shoulder control correction used by different organizations when fatigue testing in LWR environments.

This paper presents the different methods of correcting shoulder control waveforms used by partners within the INCEFA+ project, compares the correction factors used, and assesses sensitivities of the correction factor to parameters such as specimen diameter. In addition, correction factors for air and PWR environments are compared. Conclusions are drawn and recommendations made for future fatigue testing in LWR environments within autoclaves.
An Alternative Corrosion Risk Assessment Method for Industrial Pipelines in Natural Gas Purification Plant
Authors: Wu Wei , Hu Haijun , Lv Yuhai , Zeng Weiguo , Li Xiufeng , Song Ke , Du Xinshuang
Published: October 2020

Natural gas is a kind of high-quality and low-carbon energy and its demand is increasing rapidly year by year. The natural gas produced from the gas well contains some corrosive impurities like CO2, H2S, and H2O. Therefore, the gas needs to be purified in purification plants before it can be used. In the process of purification, the impurities in the natural gas will cause corrosion to the purification equipment, especially to the industrial pipeline, which will lead to perforation and leakage of the pipeline, and even cause poisoning, fire or explosion, and other serious safety accidents. In order to ensure the safe operation of the industrial pipeline in the purification plant, it is necessary to carry out effective inspection and maintenance measures for the pipelines.

The traditional regular inspection method just inspects a certain proportion of the pipelines which are selected by on-site inspection personnel. But limited by technical level and work experience of the inspection personnel, some high-risk pipelines may be neglected. Therefore, some plants try to adopt risk-based inspection (RBI) to carry out a risk assessment and conduct a comprehensive inspection on high-risk pipelines, so as to improve inspection efficiency and reduce inspection cost. However, in practice, it was found that the pipeline risk levels are not in accordance with the actual inspection results. The reason is that the RBI method developed in the background of oil refining and chemical industry is not suitable for natural gas purification plants.

In order to solve the problems, this paper analyzed the relationship between the influencing factors and pipeline corrosion behavior. The influencing factors include the impurity contents (CO2, H2S, H2O, and chlorides), pipeline materials (carbon steel and austenitic stainless steel), and service conditions (operating temperature, operating pressure and flow velocity). Meanwhile, the plant management status and maintenance factors were also considered as the influencing factors to pipelines. According to the analysis, a corrosion risk assessment method for the pipelines in the natural gas purification plant was developed based on fault tree and scoring method. Finally, the method was applied to the pipelines in purification plant to verify the accuracy of this method.
Thermal Fatigue Cracking due to Intermittently Flowing Drain Water in Steam Piping
Authors: Koki Saito , Tomohiro Watanabe
Published: October 2020

In a petrochemical plant, a steam leak incident happened due to a through-wall crack, which was found around the branch connection between the superheated steam pipe header and the branch pipe for the safety valve. Similar cracks had been observed in the Normally No Flow (NNF) line pipes sometimes. We decided to investigate the cause of these cracks. The crack was found along the circumferential welding line of the branch connection. According to the microfractography, the origin of the crack was internal surface of the pipe and it propagated through the thickness of the wall. Striations were observed on the fracture surface, and it showed the fatigue effect. All the NNF line pipes where the leak incidents occurred were installed upward and then connected to the horizontal pipe toward the safety valve. Infrared thermographic testing revealed that the steam drain pooled in the horizontal pipes was flowing intermittently toward the superheated steam pipe header. Cyclic thermal stress was sure to occur in the damaged area with calculation by FEM, and the cause was assumed to be thermal fatigue cracking due to intermittent dripping of drain water condensed in the NNF pipe. We decided to correct the slope of the horizontal pipe so that the drain was not pooled. Also, we checked all other NNF line pipes upwards and confirmed that there was no possibility of a similar incident due to drain in the horizontal pipe.
Effect of Peak Excitation Frequency on Seismic Fatigue Damage of Plant Pipelines
Authors: Inada Fumio , Sakai Michiya , Morita Ryo , Tamura Ichiro
Published: October 2020

In a previous report, a new method of calculating the approximate seismic cumulative fatigue damage of plant pipelines was developed, in which the sum of the cumulative absolute velocities (CAV) of the pipeline response per cycle was calculated, and the result was applied to the allowable vibration velocity described in the ASME Operation and Maintenance (O/M) code 2012. The new method provided a conservative value of cumulative fatigue damage. In this present study, a parameter showing the effect of a concentrated mass attached to the tip of a cantilever pipe was obtained as a function of the ratio of the concentrated mass to the mass of the cantilever pipe by eigenmode calculation using ABAQUS. In the previous report, the new method was based on the relative response of the pipeline, whereas in this present study, the application of the method was expanded to evaluations using the CAV of the excitation input for each cycle. We conducted the fast forward simulation of a real earthquake to determine the effect of the peak frequency change on cumulative fatigue damage, and we found that the response of cumulative fatigue damage at the peak frequency tends to decrease with increasing peak excitation frequency, which was consistent with the results obtained using the previously reported new method. Both the new method and the newly expended method are based on the ASME O/M code, and the results obtained by these methods suggest that the peak frequency tends to affect general pipelines. In the calculations, when the configuration of the pipeline is fixed and the mode shape does not change, the cumulative fatigue damage was found to decrease with increasing peak frequency of input acceleration. If the mode shape changes with the peak input acceleration frequency, then cumulative fatigue damage is affected. Moreover, if the participation factor has a larger value in a higher mode, the cumulative fatigue damage also has a larger value.
Extension of PASCAL4 Code for Probabilistic Fracture Mechanics Analysis of Reactor Pressure Vessel in Boiling Water Reactor
Authors: Lu Kai , Katsuyama Jinya , Li Yinsheng
Published: October 2020

In Japan, Japan Atomic Energy Agency has developed a probabilistic fracture mechanics (PFM) analysis code, PASCAL4, for probabilistic evaluation of reactor pressure vessels (RPVs) in pressurized water reactors (PWRs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) events. Besides severe PTS events, however, transients associated with normal operations, such as the cooldown and heatup transients associated with reactor shutdown and startup, respectively, should also be considered in the integrity assessment of RPVs in both PWRs and boiling water reactors (BWRs). With regard to a heatup transient, because temperature is at its minimum, and tensile stress at its maximum on the RPV outer surface, outer surface crack and embedded crack near the RPV outer surface should be taken into account. To extend the applicability of PASCAL4, we improved the code to include analysis functions for these cracks. The improved PASCAL4 can be used to run PFM analyses of RPVs subjected to both cooldown (including PTS) and heatup transients. In this paper, improvements made to PASCAL4 are firstly described, including the incorporated stress intensity factor solutions and the corresponding calculation methods for vessel outer surface crack and embedded crack near the outer surface. Using the improved PASCAL4, PFM analysis examples for a Japanese BWR-type model RPV subjected to thermal transients including a low temperature overpressure event and a heatup transient are presented.