bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Simplification for the Surface Process System in Oilfields
Authors: Liang Yongtu , Wang Bohong , Zheng Jianqin , Lei Tiantian , Zhang Xin , Zhang Haoran
Published: November 2019

Continuous development of oilfields fosters a growing need for the simplification of oilfield surface process systems (SPSs) to reduce operating and management costs. Wells, testing stations, transferring stations, and central processing facilities are the main facilities in an SPS; pipelines are used to connect these stations. In this system, production radius (PR) is an important index to determine which transferring station can a testing station be linked to. Different simplification plans will lead to different operating and management costs in the following production period. Therefore, the simplification plan should be carefully designed to minimize cost and facilitate management. This paper proposes an optimization method for the simplification of SPSs in oilfields. First, an evaluation model is developed based on fuzzy analytical hierarchy process (FAHP) to select the transferring stations that need to be decommissioned. Second, hydraulic and thermal calculations are performed to get the data for the calculation of PRs. Third, the PRs, including oil gathering radius, water flooding radius, and hot water washing radius are computed to determine the linkage between the transferring stations and the testing stations. Finally, a construction plan is obtained for new pipelines of the testing stations. A case study is conducted to verify the effectiveness of this method. The results show that this method is suitable for the simplification of SPSs in oilfields.
Burst Strength of Glass Fiber Reinforced Polyethylene Pipes With Delamination Defect
Authors: Ni Zhenlei , Shi Jianfeng , Zheng Jinyang
Published: November 2019

Glass fiber reinforced polyethylene pipes (GFRPs) are increasingly utilized in the oil and gas transportation industries because of their various benefits. Delamination is one of the most common defects in GFRPs during manufacturing and service, which can affect their mechanical properties. This paper focused on the influence of delamination on short-term burst strength of GFRPs. The GFRPs specimens were 100mm-inner diameter and reinforced by 12 layers of ± 55° cross winding glass fiber tapes. Firstly, artificial delamination of different widths were designed and put into the specimens. Then, the short-term burst tests were carried out. Meanwhile, finite element models were established to predict the burst pressures and the numerical results were in good agreement with that of test results. The results showed that the widths and axial locations of delamination defects had significant influence on the burst pressure and stress distribution, which could lead to a premature burst failure of GFRPs during service. The deformation of GFRPs close to the defect region was also analyzed and the failure mechanism of GFRPs containing defects was discussed in detail.
Decay of Excitation Load From Heat Recovery Steam Generators (HRSG) to Attached Piping System As a Function of Pipe Supports Locations
Authors: Appiah Emmanuel , Gawande Kshitij
Published: November 2019

Construction of combined cycle gas turbine (CCGT) plants, which are combination of a simple cycle gas turbine (Brayton cycle) and a steam power cycle (Rankine cycle), have increased in recent years due to their high efficiency, low emissions, relative compact size, and minimal delivery time, among other advantages. One key component of CCGT is a heat recovery steam generator (HRSG). The HRSG is basically a heat exchanger composed of a series of preheaters (economizers), evaporator, reheaters, and superheaters. Combustion gas from gas turbine is used as an energy source for steam generation in the HRSG. Due to high mass flowrate of combustion turbine exhausts gas and injection of water to reduce NOx contents, high vibration and severe noise are created. The noise induces acoustic resonance in the HRSG duct cavities. The high vibration together with the acoustic resonance creates large forces. These forces have been attributed to excitation mechanisms including fluid elastic instability, random turbulence excitation, and periodic wake shedding. Some of the forces are transmitted to the attached pipes. Integrity of the piping system to withstand the forces depends on rigid and variable pipe supports. It is therefore paramount to determine the load induced into the supports to design them adequately. The purpose of this paper is to provide relative magnitude of loads experienced at various pipe supports as a function of distance from the HRSG (load decay). This knowledge is expected to help support designers to optimize material allocation to ensure pipe system integrity at optimum cost.
Study of Thermal Distribution in the Shock Suppressors (Snubbers) due to Heat Induced by High Frequency Vibrations
Authors: Mayes Alex , Gawande Kshitij P.
Published: November 2019

Hydraulic shock suppressors (snubbers) are used in dynamic restraints to prevent piping systems and equipment from occasional loads such as turbine trips, sudden valve closures, and seismic events. An occasional load can be defined as an impact load where forces and moments are applied over very short periods of time. The current study is a continuation of a published study on snubbers experiencing high frequency vibrations. The previous study concluded that snubbers should not be used in high frequency vibratory environments due to deterioration in the quality of hydraulic fluid and an increase in wear on snubber components. The present study takes a closer look at heat energy added to the system due to such high frequency vibrations. The power delivered by a typical vibration observed in an industrial piping system is calculated and assumed to enter into the snubber fluid as heat. This is modeled using a thermal finite element simulation and the resulting thermal distribution pattern, within the snubber body, is produced. Also, a separate analysis is performed in order to get a thermal distribution pattern on a snubber due to an increase in the environmental temperature. This distribution pattern is then compared with the one obtained from an internal heat source. The study is performed using computational methods in conjunction with analytical methods to determine if heat energy is the main cause of snubber fluid deterioration.
Ductility and Fatigue Strength Loss of a Hydrogen-Charged 316L Austenitic Stainless Steel
Authors: Baek Un Bong , Nguyen Thanh Tuan , Nahm Seung Hoon , Ryu Kwon Sang
Published: November 2019

The susceptibility of 316L-type austenite stainless steel to hydrogen was quantified by means of SSRT results and low-cycle fatigue life measurement. Both tests were conducted in the air condition after being charged with high-pressure hydrogen gas of 10 MPa and a temperature of 300°C for 120 hours. In addition, SSRT tests in gaseous hydrogen at a pressure of 10 MPa were also performed and compared to the tests conducted in hydrogen pre-charged and as-received conditions. The 0.2% yield strength and tensile strength did not show there to be a considerable difference between hydrogen pre-charging and the as-received conditions, whereas the gaseous hydrogen condition revealed a remarkable degradation in tensile properties, especially in terms of fracture elongation. In the case of fatigue life test, a considerable influence of hydrogen pre-charging in fatigue life properties was observed in the high strain amplitude regime whereas the measured values in the low strain deformation region are consistently comparable to that in the as-received condition. Fatigue limit was not affected by hydrogen pre-charging.
Review of Tensile Strain Capacity Prediction Models for Strain-Based Design of Pipelines
Authors: Park Dong-Yeob , Gianetto James A.
Published: November 2019

In this paper, three tenile strain capacity (TSC) prediction models developed for strain-based design (SBD) of girth-welded pipelines were reviewed, together with a brief introduction of technical backgrounds of their development. Most TSC models rely on small-scale mechanical and fracture toughness measurements to estimate the TSC of pipelines. Hence, we surveyed published experimental and computational data to examine the transferability of small-scale fracture toughness measurements to large-scale pipe fractures. Lastly, some gaps and issues that were found from the review are proposed for improvement of TSC models for SBD. The critical issues found with current TSC models and SBD are (a) differences in strain measurement for full-scale pipe tests/simulations, (b) multiple crack tip opening displacement (CTOD) definitions, (c) no application of J-integral as a toughness parameter, (d) no consensus on failure criteria, and (e) inconsideration of thermal and natural strain aging effects.
Stress Intensity Factors for an Edge Crack Interacting With an Embedded Parallel Crack for a Finite Plate Under Pure Bending
Authors: Ma Qin , Perl Mordechai , Levy Cesar
Published: November 2019

Parallel cracks are often detected in components under various pressurized applications using non-destructive methods. For non-aligned parallel cracks, on-site service needs to decide whether they should be treated as coalesced cracks or separate multiple cracks for Fitness-for-Service Criteria. Such standards are very different from one another for the adjustment of multiple nonaligned cracks in existing sources. Furthermore, those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, in this study, we investigate stress intensity factors of an edge crack in a finite plate under pure bending when interacted by an imbedded parallel crack. Different criteria and standards are then used to correlate the present results in order to recommend the usage of those standards for the purpose of Fitness-for-Service and to classify the standards as either conservative or non-conservative. If H and S represent the vertical gap and horizontal separation distance between the cracks, respectively, and a2 is the length of the crack, a parametric study of parallel crack separation distance and gap on the crack stress intensity factor has been undertaken. The parallel cracks are practically located within the tensile bending stress regime only. Stress intensity factors (SIFs) have been acquired for a wide range of the normalized horizontal gap of S/a2 = 0.4∼2.0 and the normalized separation distance of H/a2 = −0.5∼2.0 between the two parallel cracks based on the principle of linear elastic fracture mechanics (LEFM). Our study indicates that certain existing standards/criteria provide results that are much more conservative than others while certain ones do not provide adequate information for application.
Effects of Welding Processes and Techniques on Mechanical and Metallurgical Properties of Dissimilar Metal Weld
Authors: Sun Dongmei (Donna) , Duan Xinjian
Published: November 2019

The dissimilar metal weld (DMW) is widely used in fabrication and manufacturing in various industries. Joining between nickel-based alloy and ferritic steel tubing and piping is commonly employed for ASME Code compliant welds for high-temperature and corrosion resistance applications.

A series of DMW samples between alloy 600 pipe and SA-106 Grade B pipe are fabricated using different welding processes, joint design and welding techniques. By detailed comparison, this paper provides insight into the effects of these different welding variables on mechanical properties (tensile properties and hardness of weld materials and heat affected zone), metallurgical properties (macro and microstructure examination) and chemistry (root pass alloying dilution etc.)

It has been shown that an asymmetric joint bevel design in consideration of different heat dissipation, melting temperature of the two materials will promote good weld bead formation during the root pass welding. Different joint designs (such as with or without consumable insert) will create variations on weld dilution and Cr/Ni recovery in the root area. Other welding variables such as tungsten electrode location for root pass welding for DMW, machine Gas Tungsten Arc Welding (GTAW) using hot wire and cold wire, etc. are also discussed.
Effect of Ageing on Residual Stresses in a Girth Welded Stainless Steel 316 L Pipe
Authors: Coulthard R. J. , Mostafavi M. , Truman C. E.
Published: November 2019

Residual stresses within welded components can redistribute when exposed to high temperatures and large levels of loading. The ageing process for a specimen attempts to replicate the temperature regime experienced during typical service use of the component, redistributing stresses from the as-welded condition to post-ageing. The aim of this investigation was to study the effects of ageing on weld residual stress redistribution and to evaluate the changes in the residual stress profiles before and after the pipe had been aged.

In this investigation the through thickness residual stresses within a narrow gap girth TIG welded stainless steel 316L pipe were measured. The ageing of the pipe specimen involved heating to 400°C for 3000 hours. To measure residual stress the incremental Deep-Hole Drilling (iDHD) method was employed; two measurements were taken, once before and after ageing.

Analysis of the measured pre and post-ageing residual stresses showed a consistent reduction in the magnitude of approximately 50 MPa, corresponding to the change in the yield stress of the material at room and elevated (400°C) temperatures; the maximum residual stress, of 450 MPa, was measured at 4 mm from the external surface of the pipe.
Comparison of Fracture Assessments of Corrosion Pits Using Sharp and Blunt Notched Crack Procedures
Authors: Meek Caroline , Spence Matthew
Published: November 2019

Historically, when determining failure criteria for a cracked structure, the structure has been assessed with the crack tip assumed to be infinitely sharp. For scenarios where it can be shown that the crack tip is blunt, such as for corrosion pits, this may lead to overly pessimistic assessments which can have implications for remnant life assessments of structures.

Recent research has been carried out to evaluate structures with the crack tip as a blunt notch with a radius, and to develop a notch acuity parameter. That research led to formulae for adapting either the failure assessment curve or the failure assessment points utilising the notch acuity parameter for ferritic materials.

This paper analyses various configurations of crack and specimen geometry, crack tip notch acuity parameter and crack spacing. It takes a finite element model of a cracked structure with an infinitely sharp crack and compares the failure parameters to those of equivalent notched cracks. The comparison is completed using the formulae derived in recent literature and those determined using finite element models with the blunt notched radii at the crack tip incorporated into the model.
Investigation of the Stresses and Interaction Effects of Nozzle-Cylinder Intersections When Subject to Multiple External Loads
Authors: Bozkurt Murat , Nash David , Uzzaman Asraf
Published: November 2019

Analyzing and solving the problem of practical cylinder-cylinder pressure vessel intersections is challenging when using a finite element approach. Although numerous theoretical and finite element solutions have been developed for the cylinder-cylinder intersection problem, there remains the requirement for an updated, innovative model which takes account of all practical as-fabricated features including fillets and crotch corner ground radii. This study presents the development of a suitable model, based on the results of a parametric macro study, which is able to compare all of these operations on a single, high fidelity model. This study considers a cylindrical pressure vessel with a single nozzle connection without reinforcement plate and examines the maximum stress values in the nozzle-shell intersection area (crotch corner) under the various loads applied to the nozzle. Additionally, internal pressure and external load actions on the nozzle, including effects of circumferential, torsional, and longitudinal moments are compared using a suitable finite element approach. Furthermore, equations and solutions for external loads in spherical and cylindrical shells are given in WRC Bulletins 107 and 537. Therefore, comparisons with the results obtained from these are made for validation purposes and the overall impact of the new as-built approach is presented.
Integrity Assessment of Cables Under Postulated Electrical Fire Accidents in a Zero-Power Research Reactor
Authors: Jyung Jae-Min , Chang Yoon-Suk
Published: November 2019

Fire protection and appropriate management are important to ensure security of nuclear facilities alike other industries. While relevant hazard analyses have been successfully carried out for commercial reactors, based on recently strengthened IAEA guideline and national standards, examination of research reactors is also required. The objective of this study is to represent integrity assessment of safety related cables connected to operating console in the control room of a zero-power research reactor. Two postulated electrical fire scenarios were identified among diverse accident causes and systematically analyzed by two numerical softwares with different turbulence models. Both polyvinyl chloride and cross-linked polyethylene were selected, respectively, as the representatives of various thermoplastic and thermoset cable materials. As results, temperature and heat flux profiles of the cables were calculated. Their maximum values were compared with the corresponding damage criteria, of which details and key findings will be discussed.
Property Degradation and Residual Life Assessment of Service Exposed Reformer Tubes
Authors: Han Zhiyuan , Xie Guoshan , Cao Luowei , Wang Likun , Sun Guohao
Published: November 2019

Reformer furnaces are widely used in a hydrogen plant to obtain hydrogen from hydrocarbon. The radiantt coils tubes are the most critical components of a reformer furnace, which can be heated up to 850 °C or higher temperature for long time during service. The failure of tubes usually happened before the designed life due to over-heating or unexpected damage, which usually leads to unplanned shutdown of plant and great losses. Thus, it is important to assess the damage conditions and residual life of furnace tubes. This study is an attempt to investigate the property degradation and residual life for service exposed reformer tubes of a hydrogen reformer furnace after 6 years service. Microstructural and mechanical experiments were carried out to reveal the property degradation, included optical observations, scanning electron microscope (SEM) observations, room temperature tensile tests, high temperature tensile tests, and stress rupture tests. Finite element analysis was also used to investigated the influence factors on the stress of tubes. The residual life of furnace tube was estimated based on these experimental and simulation results.
Experimental Studies on Discharge Characteristics of the Typical Thermally-Activated Pressure Relief Device Used for High-Pressure Hydrogen Storage Cylinder in Different Fire Conditions
Authors: Bo Ke , Zheng Jinyang , Gu Chunlin , Zhao Baodi , Huang Qianghua , Liao Binbin
Published: November 2019

Thermally-activated pressure relief devices (TPRD) with glass bulbs or fusible alloy are applied to high-pressure hydrogen storage cylinders (HHSC), in order to release hydrogen gas from the cylinder in fire accidents. In this paper, cylinders with different TPRDs were tested in two groups using different bonfire test methods. In group A, the fire was set exactly under the TPRD. While in group B, the fire was set 80 mm beside the TPRD. The result shows that TPRDs with glass bulb and fusible alloy acted in a similar way when the fire was under the cylinder and the TPRD. However, they acted in a quite different way when the fire was only under the cylinder and beside the TPRD. In group A, hydrogen was released continuously from TPRD both for glass bulb and fusible alloy. In group B, hydrogen was released continuously from the TPRD using glass bulb which was similar to the group A. However, for TPRDs using a fusible alloy, hydrogen was released in several stages taking much more time. The results are instructive for the design and selection of TPRDs on HHSC.
Elastoplastic Solution and Limit Load Analysis of Orthotropic Cylindrical Shell Subjected to Internal Pressure
Authors: Zhao Yujie , Xu Min , Li Chunxiao , Zhou Binbin , He Xiaohua , Zhou Changyu
Published: November 2019

Cylindrical shell structure is widely used in pressure vessels. In this paper, the orthotropic cylindrical shell structure is analyzed based on the theory of elastoplastic mechanics and the Hill48 yield criterion, the elastoplastic limit load expression of the orthotropic cylindrical shell and the corresponding three-dimensional stress formulas at different stages are obtained. The effect of the radius ratio and the yield strength ratio on the elastic limit load and plastic limit load of the cylindrical shell are also discussed. Finally, the orthotropic cylindrical shell structure is simulated by finite element method, the numerical results verify the correctness of the analytical solutions.
Development of New Design Fatigue Curves in Japan: Discussion of Crack Growth Behavior in Large-Scale Fatigue Tests of Carbon and Low-Alloy Steel Plates
Authors: Takanashi Masahiro , Ueda Hiroshi , Saito Toshiyuki , Ogawa Takuya , Hayashi Kentaro
Published: November 2019

In Japan, the Design Fatigue Curve (DFC) Phase 1 and Phase 2 subcommittees, which are a part of the Atomic Energy Research Committee of the Japan Welding Engineering Society, have proposed new design fatigue curves and fatigue analysis methods for carbon, low-alloy, and austenitic stainless steels. To confirm the validity of the proposed design fatigue curves, a Japanese utility collaborative project was launched, and the authors conducted fully reversed four-point bending fatigue tests for large-scale specimens of carbon steel and low-alloy steel plates. Subsequently, in a previous paper (PVP2018-84456), the authors reported that the fatigue lives determined by the best-fit curve proposed by the DFC subcommittee corresponded to those of approximately 1.5–7.0-mm-deep crack initiation in large-scale specimens.

In this study, the fatigue crack initiation and propagation behavior observed in large-scale specimens was investigated by using a plastic replica and beach mark method. Similar to the case of small-sized specimens, in the large-scale specimens, multiple fatigue cracks initiated at an early stage of testing, and propagated with coalescence to penetrate the specimen width. However, no fatigue cracks were detected at the design fatigue life. Approximately 100-μm-long cracks were observed, albeit only after the specimen was subjected to a number of cycles that corresponded to approximately 3.5 times the design fatigue life.

According to NUREG/CR-6909 Rev.1, the crack depths in small-sized round bar specimens at the fatigue lives, which are defined by 25%-stress-drop cycles, are reported to be approximately 3 mm. The results of the large-scale tests indicated that regardless of the specimen size, nearly the same phenomenon occurred on the specimen surface until approximately 3–4-mm-deep crack initiated. The size effect was mainly caused by the stress gradient. The finite element analysis indicated that the stress gradient in the large-scale specimen was gentle owing to the large thickness of the specimen, and the stress in the vicinity of the surface was considered to be uniform. In conclusion, the size effect was not apparent. As the same conclusion can be applied to considerably larger actual components, designers do not need to consider the size effect when designing pressure vessels or piping by using the design fatigue curve determined based on small-sized specimens.
Consideration of Thermal Embrittlement in Alloy 316H for Advanced Non-Light Water Reactor Applications
Authors: Ren Weiju , Lin Lianshan
Published: November 2019

To construct advanced non-light water reactors (ANLWRs) operating in the temperature range above that for the traditional light water reactors (LWRs), Alloy 316H is one of the candidate materials because of its inexpensiveness, significant service experience, and qualification for nuclear applications by the American Society of Mechanical Engineers (ASME). However, during the life span at temperatures expected for the ANLWRs, the alloy is likely to experience thermal embrittlement that has not been a concern for the traditional LWRs. To prepare for the development, the possibility of adverse thermal embrittlement effects on Alloy 316H performance in the ANLWRs must be evaluated and a technical basis regarding thermal embrittlement, if necessary, must be established for structural integrity analysis to provide reasonable assurance of adequate nuclear safety protection.

In this paper, current technical basis for nuclear applications of Alloy 316H deterioration from thermal aging is briefly introduced. The likelihood of adverse thermal embrittlement effects on Alloy 316H performance is evaluated through historical data on microstructural and mechanical property evolution. Characterization of thermal embrittlement is then discussed, followed by a review of predictive models and trend curves for alloy embrittlement. Based on the review and evaluation, technical gaps for addressing thermal embrittlement issues are identified and gap-filling actions are recommended for establishing a technical basis to enable adequate consideration of thermal embrittlement in Alloy 316H applications to the ANLWRs.
Design and Material Selection for Acoustic Isolated Pipe Supports
Authors: Eijgenhuijsen Menno , Masand Girish
Published: November 2019

Health, Safety and Environmental (HSE) Reports prepared for the detailed design phase of facilities in the Oil & Gas or Petrochemical industry often recommend the application of acoustic (noise) insulation at specific pipe sections. Those recommendations include the use of acoustic isolation material at pipe support locations, refer Fig.1. The aim for using acoustic isolation supports is to limit noise being transmitted to the supporting structures and surrounding environment. High noise levels may be flow induced due to the presence of various equipment restrictions and discontinuities in gas and steam piping. Specific material requirements and adequate guidelines for designing effective acoustic isolation supports are generally not provided in abovementioned HSE reports and project specifications. The purpose of this paper is to create an awareness of the importance to carry out design of acoustic isolation supports based on proper engineering and to start this activity at an early stage in a project. This paper describes the basic theory of acoustic isolation and specific considerations in the design of pipe supports to minimize transmission of noise to underlying support structures while being effective to carry the piping loads. The paper also briefly describes a test method to determine the dynamic stiffness for isolation material, an important property to assess whether a material can be used for effective isolation. The paper ends with a comparison of properties for some materials and their effectiveness when used to isolate noise.
Pathway to Evaluate Printed Circuit Heat Exchanger Based on Simplified Elastic-Perfectly Plastic Analysis Methodology for High Temperature Nuclear Service
Authors: Devi Urmi , Morrison Machel , Hassan Tasnim
Published: November 2019

Printed Circuit Heat Exchangers (PCHEs) are well-suited for Very High Temperature Reactors (VHTRs) due to high compactness and efficiency for heat transfer. The design of PCHE must be robust enough to withstand possible failure caused by cyclic loading during high temperature operation. The current rules in ASME Code Section III Division 5 to evaluate strain limits and creep-fatigue damage based on elastic analysis method have been deemed infeasible at temperatures above 650°C. Hence, these rules are inapplicable for temperatures ranging from 760–950°C for VHTRs. A full inelastic analysis method with complex constitutive material description as an alternative, on the other hand, is time consuming; hence impracticable. Therefore, the simplified Elastic-Perfectly Plastic (EPP) analysis methodology is used as a solution in ASME Code Section III Division 5. The current literature, however, lacks any study on the performance evaluation of PCHE through EPP analysis. To address these issues, this study initiates the pathway of EPP evaluation of an actual size PCHE starting with elastic orthotropic analysis in the global scale. Subsequently, preliminary planning for analyzing intermediate and local submodels are provided to determine channel level responses to evaluate PCHE performance against strain limits and creep-fatigue damage using Code Case-N861 and N862 respectively.
Vibration Design of Amine Regenerator Tower and its Piping System
Authors: Park Jae-Yeol , Chae Minsung
Published: November 2019

Fluid induced vibration in high-elevation tower and its piping system is examined with on-site measurement, numerical simulation, and analytical model. In this article, Amine regeneration tower in gas separation plant is subjected to investigation since significant vibration in both tower and its piping system prevents the normal operation especially with increased loading capacity. Measurement in frequency domain for inlet piping system shows single dominant peak as well as small peaks in low frequency range. In search of solution, analytical study with computational fluid dynamics model is conducted to reduce fluid velocity which results in decreased dynamic force in both piping system and regeneration tower and reduces the fluid-induced vibration associated with slug flow. Based on the fluid dynamics study, piping modification is designed and applied to the piping system and tower and vibration improvement is achieved as expected.
Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 4 — Proposal of Optimal Combination Method for Disc Spring Units and Newly Friction Model for Sliding Elements
Authors: Fukasawa Tsuyoshi , Okamura Shigeki , Somaki Takahiro , Miyagawa Takayuki , Uchita Masato , Yamamoto Tomohiko , Watakabe Tomoyoshi , Fujita Satoshi
Published: November 2019

The authors proposed a newly three-dimensional isolation system, consisting of a rubber bearing, vertical oil dampers and disc spring units, to reduce the seismic response in the vertical direction as well as horizontal direction. This isolation system is employed with a number of disc spring units to provide the vertical restoring force to the superstructure. The disc spring units are combined by three disc springs in parallels and they are are stacked in six serials. The vertical restoring force has susceptible to the variation forces for the individual disc springs because the disc spring units are combined in the six serials. The The purpose of this paper is to present two kinds of proposal to improve the quality control of our isolation system and the prediction accuracy of seismic response. The first is to create the the optimal combination method for the disc spring units using the meta-heuristic algorithm to minimize the variation of vertical vertical restoring force. The proposed optimal method was verified through the result of static loading tests using the 72 disc springs which have the half dimensions to full scale. The second is to create a newly analytical model for the friction force caused by polymeric materials. The proposed analytical model was verified by comparing the loading test results. Moreover, the seismic isolation performances were clarified by the seismic response analysis that consider the vertical restoring force of the disc spring units which were combined using the optimal method and the friction force of sliding elements which were modeled by the proposed friction model. This analytical result revealed that our isolation system can reduce the seismic response not only for the high frequency components but also the low frequency ones.
Proposal for Improving Insulation Installation Practice for Superheated Steam Line
Authors: Kanamaru Shinichiro , Qian Shaoxiang , Yamada Yoshinori
Published: November 2019

Insulation is widely used in process plants to reduce heat loss of process fluids in piping and pressure vessels. However, insulation is often not installed around Normally No Flow (NNF) line pipe. In a refinery plant, a steam leak incident happened due to a through-wall crack, which was found around the connection between an insulated superheated steam line with insulation and an uninsulated safety valve line. The through-wall crack was identified to be a fatigue crack initiated at the inner surface by fractography. An unsteady Computational Fluid Dynamics (CFD) analysis was performed to identify mechanism of the through-wall crack initiation. Based on the observation of fractography and the CFD analysis, it is inferred that the through-wall crack was induced by a high cycle thermal fatigue phenomenon, so-called thermal striping, due to incomplete mixing of hot and cold fluids. Many thermal striping incidents in nuclear plants and process plants have been reported. In view of the above fact, it is suggested that conventional insulation installation practice for NNF line pipe, in particular superheated steam line, may cause cracks due to thermal striping around the connection between main superheated steam pipe and branch dead-end leg. In this paper, a convenient guideline for insulation installation is proposed for a dead-end leg of superheated steam line to prevent cracks caused by thermal striping. The guideline can be used to judge the necessity of insulation installation, based on degree of superheat of steam.
Simplified SCC Simulation Considering Growth Arrest at Fusion Line of Weld
Authors: Okada Hiroshi , Kamaya Masayuki , Yusa Yasunori
Published: November 2019

The authors have carried out a series of developments on methods to perform natural crack propagation analysis in last several years. This paper describes the results of SCC (stress corrosion cracking) growth analyses under some assumptions on the growth behaviors and assumed stress distributions. The SCC growth was assumed to initiate in the weld metal and to be arrested at the fusion line of weld. Although it is possible to model a realistic configuration of weld, it may take a large amount of modeling and computational cost. Thus, an appropriate simplification for the SCC growth prediction is demanded. Hence, two kinds of welds were considered in the present investigation. One had a realistic configuration. The other was a simplified one whose volume of the weld metal had a rectangular shape. Thus, a further simplification was made such that the cracks were assumed to be rectangular in their shapes. SCC growth analyses were performed by finite element based crack propagation simulation software using a remeshing technique that was developed and has been updated by the authors. The paper describes the method of crack propagation analysis briefly and presents the results of the SCC growth analyses. Some discussions on the simplification of the SCC propagation analysis are presented. Then, it is concluded that an appropriate use of rectangular shaped crack may give a conservative prediction on the SCC growth prediction.
The Strain Concentration of High Strength Girth Weld Subjected to Tensile Displacement
Authors: Shuai Jian , Zhang Yinhui , Lv Zhiyang , Shuai Yaodong
Published: November 2019

High grade pipelines have been the majority in China since the beginning of this century. Some pipelines in mountainous area and other places experienced the ground movement because of geohazards and the disturb of construction activities. The strain capacity is important to keep pipelines subjected to tensile displacement in safe. However, the strain capacity does not depend on the pipe body but on the girth weld because the girth weld is always non-homogeneous. The strain concentration may happen where material yields in advance. Therefore, the strength matching of the girth weld towards pipe body can greatly affects strain capacity of pipelines. Generally, girth weld is designed to over-matching to prevent the strain concentration. However, in pipeline engineering, actual strength of pipe body may be much higher than the specified minimum yield stress, leading the girth weld to be under-matching in fact. In addition, even in over-matching girth weld, there may be softening zone in HAZ. In this paper, the tensile tests of X80 girth weld were performed. Local constitutive relations at the weld, pipe body and HAZ were obtained by using the whole field strain on the specimens. The experiment showed under-matching in the specimen. Based on the results of local constitutive properties of the specimen, the finite element model of X80 pipeline girth weld subjected to tensile strain and inner pressure was established. It demonstrated that strain concentration happened in weld area in under-matching girth weld and softening zone in over-matching girth weld. Inner pressure has an impact on strain concentration in a case that strain exceed the certain limit.
Repair of High Temperature Flue Gas Line in Fluid Catalytic Cracking (FCC) Service
Authors: Chiluvuri Siva Kumar , Adusumilli Yeswanth Kumar , Penso Jorge
Published: November 2019

A typical Fluid Catalytic Cracking Unit (FCCU) generates high temperature flue gas in the process of regenerating the catalyst. This flue gas is diverted to a stack after removal of catalyst fines and excess heat using a Waste Heat Recovery Unit (WHRU) or CO boiler. This flue gas line is a large diameter (1.2 m /2 m) piping and is a combination of Hot Wall (bare SS304H piping with external insulation) upstream of Orifice Chamber and Cold Wall (Carbon steel piping with internal refractory lining) for the downstream side.

In a major revamp project, large portion of flue gas line was replaced with some dimensional and design changes. A crack was noticed at the SS304H side of hot wall to cold wall transition joint downstream of Orifice Chamber after approximately 2 years in operation. The line operates around 700 °C and 0.15 Bar(g) at the location of the crack. The initial crack was measured to be approximately 250 mm to 300 mm and grew to a full circumference crack in a short time resulting in minor flue gas leaking with catalyst fines. This paper discusses the details on how the issue was addressed on site and a temporary repair (i.e. welding of a box on high temperature piping) was carried out online safely, while the unit remained in operation. Further, the paper presents the root cause assessment and design modifications implemented for hot wall to cold wall transition joint during a scheduled turnaround.
Phase Relation of Forces Between Multiple Bends
Authors: Belfroid S. P. C. , Pereboom H. , Gonzalez-Diez N. , Anantharaman A.
Published: November 2019

Multiphase flow induced vibrations are difficult to calculate. This is in part the prediction of the force frequency spectrum at a single bend, part the influence of bends on the multiphase flow behavior and therefore the prediction of the multiphase flow characteristics between bends. In this paper, the evolution of the forces between subsequent bends are discussed including the phase relations of the forces on the different bends. For annular flow, the forces between the different bends are incoherent and are more or less random. However, for stratified and especially slug flow, the forces remain coherent up to high frequencies. This means in a frequency response analysis of a piping structure, the transport velocity of the multiphase structures must be taken into account.
XFEM and Standard Fracture-Mechanics Analyses of the Reactor Pressure Vessel Gösgen Based on Thermal-Hydraulics Input Data From KWU-MIX and CFD Analyses
Authors: Mutz Alexander , Nicak Tomas , Trewin Richard , Cremer Ingo
Published: November 2019

The integrity of a reactor pressure vessel (RPV) has to be ensured throughout its entire life in accordance with the applicable regulations. Typically an assessment of the RPV against brittle failure needs to be conducted by taking into account all possible loading cases. One of the most severe loading cases, which can potentially occur during the operating time, is the loss-of-coolant accident, where cold water is injected into the RPV at operating conditions. High pressure in combination with a thermal shock of the ferritic pressure vessel wall caused by the injection of cold water leads to a considerable load at the belt-line area known as Pressurized Thermal Shock (PTS).

Usually the assessment against brittle failure is based on a deterministic fracture-mechanics analysis, in which common parameters like J-integral or stress intensity factor are employed to calculate the load path for an assumed (postulated) flaw during the PTS event. As an alternative to this standard approach a fracture mechanics assessments based on eXtended Finite Element Method (XFEM) approach can be performed.

The most important input data for the fracture-mechanics analysis is the transient thermal-hydraulics (TH) load of the RPV during the emergency cooling. Such data can be calculated by analytical fluid-mixing codes verified on experiments, such as KWU-MIX, or by numerical Computational Fluid Dynamics (CFD) tools after suitable validation. In KWU-MIX, which is the standard used for TH calculations within PTS analyses, rather conservative analytical models for the quantification of mixing and, depending on the water level, condensation processes in the downcomer (including simplified stripe and plume formations) are utilized. On the contrary, the numerical CFD tools can provide best-estimate results due to the possibility to consider more realistically the stripe and plume formations as well as the geometry of the RPV in detail.

In a previous paper [1] results of standard and XFEM analyses of the RPV Gösgen 1 based on thermal-hydraulics input data from KWU-MIX were presented. This paper presents new results based on thermal-hydraulics input data from CFD. The new results are compared with those from [1] in order to show additional safety margins obtained by using thermal-hydraulics input data from CFD.
Investigation of Hydrogen Diffusion Characteristics of the Heat Affected Zone of 2.25Cr-1Mo-0.25V Steel by an Electrochemical Permeation Method
Authors: Song Xin , Han Zelin , Liu Bin , Qin Mu , Duo Yuancai , Song Yan , Cheng Guangxu
Published: November 2019

The heat affected zone (HAZ) of 2.25Cr-1Mo-0.25V welded joint is a critical part for the safety of hydrogenation reactors. Hydrogen has a significant effect on the HAZ, studying hydrogen diffusion characteristics, such as: hydrogen flux and the effective hydrogen diffusivity has a remarkable value in investigating the hydrogen-induced material degradation mechanisms. In this work, an electrochemical permeation method was applied to study the hydrogen diffusion characteristics of HAZ. Then, the metallographic microscope and a software “Image J” were used to analyze the density of grain boundaries of HAZ. The effect of the post–weld heat treatment (PWHT, i.e. annealing) on the hydrogen diffusion characteristics of HAZ was also been investigated. The results show that after PWHT, the effective hydrogen diffusivity of HAZ increases from 1.63 × 10−7cm2·s−1 to 3.68 × 10−7cm2·s−1, the hydrogen concentration decreases from 1.92 × 10−4mol·cm−3 to 1.09 × 10−4mol·cm−3, and the hydrogen trap density decreases from 3.00 × 1026m−3 to 0.76 × 1026m−3. Thus, PWHT can significantly reduce density of grain boundaries, thereby reducing the hydrogen trap density, enhancing the hydrogen diffusivity and reducing the hydrogen concentration.
Engineering Critical Assessment of Post Weld Heat Treatment for Full-Encirclement Tees Greater Than 1.25 Inches
Authors: Landreth Kolton , Li Qi , Marwaha Raghav
Published: November 2019

Full-encirclement split tee fittings for hot tapping and plugging (HT&P) wrap completely around the pipeline and are welded in place. The welded joint provides mechanical reinforcement of the pipe and branch. When full-encirclement hot tap tees are welded to pipelines 24 inches in diameter or larger, the header must often be at least 1.25 inches thick to pass the required calculations for reinforcement. This means the joint will require post weld heat treatment (PWHT) according to ASME B31.8 and CSA Z662. However, PWHT can be extremely dangerous and impractical, potentially elevating temperature to the point where material strength of the pressurized pipeline is compromised. An engineering critical assessment per ASME FFS-1/API 579 indicated PWHT may not be required for a full-encirclement hot tap tee over 1.25 inches thick. Specifically, research showed that the residual stresses developed during the welding process may not limit the design of a full-encirclement tee or lead to shorter pipeline design life. This paper illustrates how a “more rigorous analysis” per paragraph 802.2.2[b] of ASME B31.8 and paragraph 4.3.12.2 of CSA Z662 may help operators avoid the PWHT requirement. It discusses the finite element analysis (FEA) simulations researchers used to induce residual stresses in a carbon steel fitting. The residual stresses induced in the fitting were used as initial condition for plastic collapse and fatigue evaluations.
Comparison and Assessment of the Creep-Fatigue and Ratcheting Design Methods for a Reference Gen3 Molten Salt Concentrated Solar Power Receiver
Authors: Barua B. , Messner M. C. , McMurtrey M. D.
Published: November 2019

The Concentrating Solar Power (CSP) Gen3 Demonstration Roadmap has recognized Supercritical carbon dioxide (sCO2) Brayton Cycle as the best-fit power cycle as it provides thermal efficiency benefits relative to the conventional Steam-Rankine cycles. However, to enable the integration of sCO2 Brayton Power Cycle, it is necessary to increase the outlet temperature of current molten salt CSP systems from 565°C to approximately 720°C. Increasing the temperature of the salt brings significant material and engineering challenges. Creep-fatigue damage accumulation and ratcheting deformation are important design considerations for receivers operating at high temperature due to frequent transient loads caused by diurnal cycling and thermal shocks from transitions between sun and cloud cover. In this work, a reference thermomechanical model of a Gen3 CSP receiver is developed to evaluate different creep-fatigue and ratcheting design approaches identified in Section III, Division 5, of ASME Boiler and Pressure Vessel Code. The design methods are then ordered based on design margin and ease of use. Design by elastic perfectly-plastic analysis is found to be the most conservative among the methods. Elastic analysis is the easiest to perform but the design calculations are extremely complicated. In contrast, design calculations are straight forward in inelastic analysis method but it requires developing a sophisticated inelastic constitutive model describing the material behavior. Several recommendations are made for developing creep-fatigue and ratcheting design rules for CSP systems.
ATLAS+ European Project: Prediction of Large Ductile Tearing in Piping Using Local Approach
Authors: Blouin Arnaud , Marie Stéphane , Remmal Al Mahdi
Published: November 2019

In the frame of the European ATLAS+ project it was decided to evaluate if a continuum damage model can simulate a four-points beading test on a ferritic pipe (A508 type). In this paper, the theoretical background is presented. Then, based on finite elements analyses, the GTN model damage parameters are defined by simulating laboratory tests on Notched Tensile specimens and Compact Tension specimens. From that identification, experimental tests on Single Edge Notched Tensile specimens are simulated in order to verify if the previous parameters are able to describe a large ductile tearing. Finally, the four points bending test simulation is also presented.