bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Fracture Mechanics Parameters Under Displacement-Controlled Elastic Plastic Fatigue Conditions
Authors: Tokiyoshi Takumi , Igari Toshihide , Takao Nobuyuki , Kanaya Akihiro
Published: August 2008

Accurate prediction of the residual life of components under long-term service is urgently needed due to requirements for the reduction of the maintenance costs of thermal power plants. Quantitative prediction of crack growth under displacement-controlled conditions such as thermal fatigue is a key to the fulfillment of this need. In a previous paper, the present authors proposed a simplified prediction method of fracture mechanics parameters such as J and C* of a perforated plate under thermal fatigue, on the basis of the reference stress approach under displacement-controlled conditions. In this paper, the fracture mechanics parameters of a CCT specimen and structural models of CrMoV cast steel under displacement-controlled conditions were numerically and experimenttally examined on the basis of the proposed method. The ratio of the elastic and the inelastic crack opening displacement, as well as the ratio of the elastic and the inelastic load point displacement, was used to correlate the fracture mechanics parameters in the elastic and inelastic region. As a result of the study, the proposed method based on displacement was found to be insensitive to small variation in the predicted results of macroscopic load in comparison with the original reference stress method, and is considered to be applicable to displacement-controlled conditions such as thermal fatigue.
Technical Bases for Alternative Stress Evaluation Criteria in Japan Based on Partial Inelastic Analyses
Authors: Asada Seiji , Okamoto Asao , Nishiguchi Isoharu , Aoki Mitsuru , Asada Yasuhide
Published: August 2008

An Alternative Stress Evaluation Criteria suitable for Finite Element Analysis using inelastic analysis has been developed. The Alternative Criteria prescribes evaluations for Primary Loads, Cyclic Loads and Fatigue. Collapse load analysis is used for the evaluation of Primary Loads. The evaluation for Cyclic Loads consists of Shakedown Evaluation and Thermal Ratchet Evaluation. The 2xY method is applied to Simplified Elastic-Plastic Analysis in Fatigue Evaluation. In this paper, the major technical bases of these evaluations are described.
Influence of Crack Orientation and Crosshead Speed on the Fracture Toughness of PVC Pipe Materials
Authors: El-Bagory T. M. , El-Fadaly M. S. , Younan M. Y. A. , Abdel-Latif L. A.
Published: August 2008

In many modern engineering application designers and manufactures of Polyvinyl chloride (PVC) pipes are interested in the evaluation of fracture toughness under several operation conditions. The aim of the present work is to investigate the fracture toughness of commercial amorphous thermoplastic PVC materials used in pipes applications. The experimental work is carried out using three different specimens types: Taper Double Cantilever Beam (TDCB), Three Point Bend (TPB), and Compact Tension (CT). Tests are conducted on specimens with thickness (17,20,22, and 26 mm), longitudinal and transverse extrusion orientations, at different crosshead speeds (50–500 mm/min) to calculate the fracture toughness of PVC pipe materials. The experimental work has revealed that the crosshead speed has a significant effect on the fracture toughness at low speed rates. This effect, however, becomes insignificant at high rates since, the fracture behavior becomes brittle. The stress intensity factor KQ is approximately the same in both longitudinal and transverse orientations. The fracture toughness decreases as the specimen thickness increases.
Effect of Mechanical Loading on the Performance of Piezolelectric Transducer for the Health Monitoring of Composite Pressure Vessels
Authors: Kusaka Takayuki , Qing Peter X. , Chang Fu-Kuo
Published: August 2008

The performance of PZT (Piezoelectric Lead Zirconate Titanate) transducer was investigated under static tensile loading using a layered actuator/sensor network (SMART Layer). The performance of PZT transducer remained unchanged when the applied strain did not exceed the static failure strain of PZT, whereas the degradation of the performance obviously occurred when the applied strain exceeded the static failure strain of PZT. Also, the performance of PZT transducer depended not on the materials of the host structure but on the thermal residual strain induced during the cure cycle. Microscopic observation showed that the degradation of the performance is a consequence of the interfacial debonding between the PZT and copper layer.
Proposal for the Implementation of Elevated Temperature Design Fatigue Curve for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V Steels
Authors: Takehana Tatsumi , Sano Takeru , Terada Susumu , Kobayashi Hideo
Published: August 2008

2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels have been used extensively as materials for elevated temperature and high-pressure hydro-processing reactors. These steels have both of high strength at elevated temperature and high resistance against elevated temperature hydrogen attack due to the addition of vanadium. The operating temperature of these reactors is between 800 and 900deg.F. The fatigue evaluations of these reactors per ASME Sec. VIII Div.2 and Div.3 can’t be performed in spite of demand for fatigue analysis because the temperature limit of design fatigue curve in ASME Sec. VIII Div.2 and Div.3 for carbon and low alloy steels is 700deg.F. Results of load and strain controlled fatigue tests conducted over the temperature range from room temperature to 932deg.F (500deg.C) are reported for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels. These data were compared with data for 2-1/4Cr-1Mo steels available from the literatures. The fatigue strength for a 2-1/4Cr-1Mo-V steel in high cycle region is higher than that for 2-1/4Cr-1Mo steels and in low cycle region is lower. The fatigue strength for a 3Cr-1Mo-V steel is almost same as that for 2-1/4Cr-1Mo-V steels. Therefore an elevated temperature design fatigue curve for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels is newly proposed. It is found from the case study that the different fatigue life can be predicted by using different mean stress correction procedure.
Recent Trends of HIP Equipment Technology in Japan
Authors: Fujikawa Takao , Manabe Yasuo , Yoneda Makoto , Kofune Shigeo , Nakai Tomomitsu
Published: August 2008

The progress of HIP (Hot Isostatic Pressing) is discussed from both the historical viewpoint and its future potential. HIP is now recognized as a useful method to obtain products with isotropic properties and high density. It is used in the manufacture of high integrity castings, various PM products and ceramic components. Especially in Japan these resultant natures have attracted attention from ceramic researchers, because HIP can compensate for the lack of reliability due to residual porosity formed in the sintering stage. P/M High speed tool steel billets, alumina cutting tool inserts, soft ferrite for magnetic recording heads all have been produced by the HIP process. Research activities are now expanding into so-called nano-technology areas such as Si-wafer processing and nano-level sensors. Entering the 21st century, however, a sluggish economy and environmental friendliness are producing strong demand for further development of smaller and lighter products with higher mechanical or electronic properties. In addition to these, the requirement for the higher productivity to reduce processing cost is intensifying, thus the developmental works on HIP equipment technology are being focussed on the improvement of its productivity as well as application to novel processing areas.
Fatigue Crack Growth in Thick-Walled Cylinders With Straight-Fronted Cracks
Authors: Kendall David P.
Published: August 2008

This paper presents the results of a comparison of fatigue crack growth in pressurized, thick-walled cylinders containing initial, straight-fronted cracks. These cracks are at the bore surface and are in the radial-longitudinal plane. The crack growth is determined from stress intensity factors calculated by the method in Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code. It is also determined from stress intensity factors calculated by a method proposed by Andrasic and Parker in 1984. In spite of the very large difference between the values of stress intensity factor calculated by the two methods for deep cracks, there is little difference between the fatigue crack growth determined by the two methods.
Control of Pulsations and Vibrations in Hypercompressors for LDPE Plants
Authors: Giacomelli Enzo , Passeri Marco , Zagli Fabrizio , Generosi Stefano
Published: August 2008

Always growing capacities, size of machines and performance requirements and often changing plant layout arrangement, determine a continuous challenge for designers of machines and plants. For hyper compressors and connected piping system, the goals of safety and reliability can be achieved only with a deep analysis of all operating conditions to determine pulsations and vibration effects. Innovative methods of simulation, modeling and technologies improve the possibility to evaluate piping and compressor behavior, allowing to obtain the efficiency and a smooth and safe plant operation.
FE Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction
Authors: Jiang Wei , Yahiaoui Kadda , Wang Chang J. , Hall Frank R. , Laoui Tahar
Published: August 2008

This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of 3D temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.
Stress/Fluid Pressure Waves in Radially Expanded Solid Tube
Authors: Karrech A. , Seibi A. C. , Pervez T. , Al-Hiddabi S.
Published: August 2008

Solid Expandable Tubular (SET) Technology is receiving a widespread use in the oil industry nowadays. This technology is essentially a down-hole cold working process consisting of expanding a solid tube by drawing a mandrel through it either mechanically or hydraulically. The hydraulic expansion requires a high back pressure to move the mandrel forward, which leads to a sudden release (pop-out) of the mandrel towards the end of the process due to the stored elastic energy within the tube-fluid system. This sudden release results in axial and radial vibrations accompanied with stress and pressure waves propagating through the three mediums (inner and outer fluids and expanded tube). In the present paper, a mathematical model describing the dynamics of the three mediums has been developed. A specific case of a 127 mm tube in a 340 mm borehole with fluids of different properties inside and outside the tube was considered. The coupling effect describing the fluid-structure interaction resulted in modifications of the waves speeds and frequencies as compared to uncoupled solutions. The study also focused on the effects of stress and fluid pressure waves on the structural integrity of the expanded tube. It was noticed that the maximum vibration occurs at the free end of the tube. In addition, the model identified potential locations along the tube, which may experience collapse.
A Fuzzy Approach for Determining a Feasible Point in a Constrained Problem
Authors: Marler R. Timothy , Yang Jingzhou , Rao S. S.
Published: August 2008

In an engineering design process, it is often desirable or even necessary to find a feasible starting point before finding the actual optimal design. The identification of unapparent feasible points provides problem insight with little computational cost. In addition, some optimization algorithms either require, or function more efficiently with, an initial point that satisfies all constraints. The advantages of using an initial feasible design are especially evident with complex structural problems and with problems that involve potential safety concerns such as the design of large pressure vessels. Although some methods are available, literature concerning the development and use of feasible-point determination is scarce. In this paper, fuzzy function theory is used to develop a novel, simple, and efficient algorithm for determining a feasible point by starting with a potentially infeasible point. Each constraint is written in fuzzy form with a newly developed membership function. The resulting optimization problem is easily solved using conventional techniques. This approach is applied to structural and manufacturing problems, including the design of a general pressure vessel. When compared with an established method, the new approach is successful and more than twenty-five times faster with larger problems.
Study on Estimation Method for Seismic Safety Margin of 3D Piping System With Degradation: Establishing Elasto-Plastic Analysis Model
Authors: Mikami Akira , Udagawa Makoto , Takada Hajime
Published: August 2008

The authors have proposed an analytical model by which they can simulate the experimental results of a piping system with full circumferential 48% thinning at an elbow or two elbows. A series of elasto-plastic analyses has been carried out in order to investigate the experimental behavior of the piping system. Dynamic analyses describe the ratcheting behavior and the average amplitude of the opening-closing displacement at elbows relatively well. And then static analyses describe ratcheting and ovaling of the cross section of pipes fairy well.
Crack Opening Area for an Isolated Crack Subjected to a Symmetric Mode I Stress Distribution
Authors: Smith E.
Published: August 2008

In developing a leak-before-break case for a component in a pressurized system, a key element is an estimation of the size of through-thickness crack that will give a measurable leakage under normal operating conditions, and this requires a knowledge of the crack opening area. In this context, the paper presents a simple derivation of an expression for the crack opening area associated with an isolated crack that is subjected to a general Mode I symmetric tensile stress distribution which could arise from a combination of applied and residual stresses. The paper also presents a simple derivation of an expression for the crack opening displacement at the crack centre which, coupled with the assumption that the crack opening profile conforms to an elliptical shape, has been used as the basis for a simplified procedure for estimating the crack opening area. The resulting expressions are validated by comparing them with known results for specific stress distributions. They are also used to give new results for a cosine stress distribution.
On Bias in To Values Derived With Compact and PCVN Specimens
Authors: Sokolov Mikhail A. , Nanstad Randy K.
Published: August 2008

The Heavy-Section Steel Irradiation (HSSI) Program at Oak Ridge National Laboratory (ORNL) includes a task to investigate the bias in the reference fracture toughness transition temperature values, To, derived with the pre-cracked Charpy (PCVN) and compact specimens. The PCVN specimen, as well as any other fracture toughness specimen that can be made out of the broken Charpy specimens, may have exceptional utility for the evaluation of RPV steels. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Precracking and testing of Charpy surveillance specimens would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. However, there are a growing number of indications that there might be a bias in To values derived from PCVN and compact specimens. The present paper summarizes data from the series of experiments that use subsize specimens for evaluation of the transition fracture toughness of reactor pressure vessel (RPV) steels conducted within the HSSI Program. Two types of compact specimens and three types of three-point bend specimens from five RPV materials were used in these subsize experiments. The current results showed that To determined from PCVN specimens with width (W) to thickness (B) ratio W/B=1, on average, are lower than To determined from compact specimens with W/B=2. At the same time, three-point bend specimens with W/B=2 exhibited To values that were very similar to To values derived from compact specimens.
Comparison of Master Curve and Statistical Model Approach for Prediction of Fracture Toughness of ASTM A285 Steel
Authors: Subramanian Karthik , Duncan Andrew J.
Published: August 2008

The master curve approach was utilized to compare fracture toughness of American Society for Testing of Materials (ASTM) A285 as developed from Charpy v-notch (CVN) data and predictive statistical models. The master curves for each of the data sets were developed in accordance with American Society for Testing Materials Specification E 1921 (ASTM E1921, “Standard Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range”), as prescribed by American Petroleum Institute Recommended Practice 579 (API-579, “Fitness for Service”). The results indicate that predictive statistical models developed from compact tension test results express a lower fracture toughness distribution when compared to CVN data.
Complex Dynamic Modelling of Mobile Robot
Authors: Grepl Robert , Vlach Radek , Ondrusek Cestmir
Published: August 2008

This paper deals with the design of complex dynamic model of quadruped walking mobil robot. There is described the method of building of the numerical computational model and its simulating. Complex model consist of submodels of robotic mechanism, DC motor, gearbox model and thermal model of electrical motor. Control algorithms are also considered in model. In the paper is also discussed application of computational model directly for control of robot and also as a data generator for global and local approximation method, mainly artificial neural networks.
Fabrication, Construction, and Operation Problems for Grade 91 Fossil Power Components
Authors: Cohn Marvin J. , Henry Jeffrey F. , Nass Dan
Published: August 2008

The use of creep strength enhanced ferritic alloys, such as Grade 91, in fossil power plants has become popular for high temperature applications. Since Grade 91 has higher stress allowables than Grade 22, a designer can specify thinner component wall thicknesses, resulting in lower through-wall thermal stresses during transient events and lower material and pipe support costs. During the past two decades, Grade 91 has been used successfully in fossil power plants. However, this alloy has had some incidents of premature failures. Case histories discuss such factors as excessively hard material, extremely soft material, overheating failures, and improper mill processing. This compilation also discusses likely root causes and solutions to avoid these potential Grade 91 problems.
Creep Stability of High Strength 9% Cr-W Ferritic Heat Resistant Tube Gr.92 After 15 Years in Service
Authors: Muraki Taro , Oghami Masahiro , Komai Nobuyoshi , Matsufuji Kosei , Katata Masaaki , Masuyama Fujimitsu , Naoi Hisashi , Fujita Toshio
Published: August 2008

High strength 9%Cr-W ferritic heat resistant steel (ASME SA213 T92, KA-STABA29) was developed as the materials for high temperature application in USC plant with a temperature at 600°C and higher pressure than 25 MPa in steam conditions. The Gr.92 contains much W, and therefore, its creep property is attained by solute dragging of W on the dislocation gliding motion and also Nb and V forms concerning MX the precipitation strengthening mechanism. This material was installed as tertiary super heater of Tobata Co-operative Thermal Power Plant, and the plant had been operated about 15 years without any trouble. In this report, stability of several properties of ex-serviced Gr.92 steel was evaluated [1,2].
Creep Failure Behavior of Creep-Strength Enhanced Ferritic Steels
Authors: Masuyama F. , Komai N.
Published: August 2008

Creep-strength enhanced ferritic steels such as Gr.92, Gr.122, Gr.23 and Gr.91 have recently been introduced for power plant applications, and some of these have experienced creep failure in boiler tubes and thick wall components after several years of operation. In order to use these steels safely in power plants, understanding of creep failure behavior is essential. In this study the creep failure of Gr.91 and Gr.92 boiler tube base metal and Type IV cracking of Gr.92, Gr.122, Gr.23 and Gr.91 welds were reproduced in test piece of actual components size. Creep failure mode was investigated, as was microstructural morphology during creep, particularly in the weldment, with discussion based on evidence of void formation and changes in the physical damage in terms of creep life.
Buckling of Composite Laminates Using Higher Order Deformation Theory
Authors: Iyengar N. G. R. , Chakraborty Arindam
Published: August 2008

Response of composite laminates under in-plane compressive or shear loadings is of interest to the analyst and designers. Since they are thin, they are prone to instability under in-plane loads. Transverse shear effects are important even for thin laminates since elastic modulus and shear modulus are independent properties. For very thick laminates neglecting transverse shear effects leads to completely erroneous results. A number of different theories have been suggested by different investigators to account for transverse shear effects. In this investigation, an attempt has been made to take into account transverse shear effects for the stability analysis of moderately thick/very thick composite laminates under in-plane compressive and shear loading using a “SIMPLE HIGHER ORDER SHEAR DEFORMATION THEORY” based on four unknown displacements instead of five which is commonly used for most of the other higher order theories. A C1 continuous shear flexible finite element based on the proposed HSDT is developed using the Hermite cubic rectangular element. The analytical results obtained have been compared with the available results in literature. Effect of various parameters like aspect ratio, thickness to side ratio, fiber orientation and material properties have been studied in detail.
Load Bearing Capacity of Through Wall Cracked Elbows: Comparison of Test Results With Calculation
Authors: Chattopadhyay J. , Dutta B. K. , Kushwaha H. S.
Published: August 2008

Integrity assessment of piping components with postulated cracks is very important for safe and reliable operation of power plants. Pipe bends or elbows are one of the very important piping components in any power plant. The existing equations of limit load of elbows have various shortcomings. Additionally, the test data on elbows are not so abundant in the literature. Against this backdrop, a comprehensive experimental and analytical program has been undertaken at Reactor Safety Division (RSD) of Bhabha Atomic Research Centre (BARC) to carry out fracture tests on through wall cracked elbows and also to propose new limit load formulas of through wall cracked elbow. The present paper describes the elbow test specimens, test set-up, test results, brief description of elastic-plastic finite element analysis, newly proposed collapse moment equations for through wall circumferentially cracked elbows and the comparison of test results with theoretical predictions.
A Method for Applying Automatic Temperature Control to the Transient Finite Element Analysis of a Pressure Vessel Undergoing Postweld Heat Treatment
Authors: Sciascia Michael
Published: August 2008

For complex finite element problems it is often desirable to prescribe boundary conditions that are difficult to quantify. The analysis of a pressure vessel undergoing postweld heat treatment (PWHT) is an example of such a problem. The PWHT process is governed by Code rules, but the temperature and gradient requirements they impose are not sufficient to precisely describe the complete vessel temperature profile. The imposition of such a profile in the analysis results in uncertainty and errors. A suitable but difficult approach is to specify heater power instead of temperatures, letting the solver determine the temperature profile. Unfortunately, the individual heater power levels necessary to meet the Code requirements are usually not known in advance. Determining the power levels necessary is particularly difficult if a transient solution is required. A means of actively controlling the heaters during the FEA solution is requirement for this approach. A simple and adaptive control algorithm was incorporated into the FEA solver via its scripting capability. Heat flux boundary conditions (heater power) were applied instead of transient temperature boundary conditions. Heater power levels were optimized to achieve predetermined time/temperature goals as the solution proceeded. The algorithm described was successfully applied to a pressure vessel PWHT with 14 zones of control. The approach may be adapted to other problems and boundary conditions.
Clarifying the Gray Area Between FEA, Code and Experience Based Design
Authors: Mair David , Florizone Don
Published: August 2008

Finite Element Analysis (FEA) codes have become increasingly more user-friendly prompting greater use in pressure equipment design and analysis. One just has to observe the number of papers published in the field of pressure vessel and piping which are based on FEA studies to realize that FEA plays a very significant role. Despite the seemingly unlimited potential of FEA to analyze pressure equipment, it is not always suited to certain applications and in fact can have many drawbacks. This paper draws on the experience of the authors to present examples of where FEA is particularly well suited and other examples of where it is not cost effective and therefore not recommended. It is the intention that this will help identify those classes of analysis where FEA has merit in pursing. Guidance and words of caution are also provided about the use of FEA to assist in ensuring that the results can be relied upon.
On the Performance of a Commercial Finite Element Code in Multi-Pass Welding Simulation
Authors: Katsareas Dimitrios Elias , Ohms Carsten , Youtsos Anastasius George
Published: August 2008

Despite the development of a number of in-house finite element codes for welding simulation and residual stress prediction, industry focuses on commercial software due to their robustness, ease of use, better convergence characteristics and the fact that residual stress analysis procedures based on them can be readily transferred to industrial applications. In the present paper the ANSYS finite element code in conjunction with the “birth & death of elements” technique, is used for the analysis of dissimilar metal pipe welds, common in primary coolant piping of nuclear power plants. Multi-pass, double V, butt welds of welded panels are also investigated, in an attempt to evaluate the method and establish the degree of model detail and complexity necessary to obtain satisfactory results, which in turn will lead to a golden rule between computational cost and practically accurate predictions. In all the individual cases under investigation, predicted residual stress and/or strain fields are compared with measurement data obtained from the literature. It is deduced that the proposed method, applied through a commercial finite element code, is simple in implementation and cost effective regarding model complexity and analysis time. The accuracy of predicted residual stresses/strains, when compared to measurements, depends largely on the availability and accuracy of welding heat input data.
Reduction in Stresses Shown in Piping Programs in Large Diameter Pipe Branch Connections by Applying Flexibilities Computed by Shell Finite Element Analysis
Authors: Robleto Robert A.
Published: August 2008

When designing branch connections in low pressure large diameter piping systems as in Figure 1, thicker is not always better. The flexibility factors in ASME B31.3 1 for branch connections do not assist the designer in taking credit for flexibility that may exist in a large diameter intersection. Since the stress intensification factors (SIFs) are relatively high for large diameter piping, many stub-in branch connections will require a pad to meet the code displacement stress limits. In an ASME B31.3 Piping analysis the stiffness of the branch connections is considered to be as stiff as a straight piece of pipe modeled as a beam. This is a simplifying assumption that can lead to expensive conservatism for the component and possibly non-conservatism for nearby equipment especially when large diameter pipe is considered. Branch connection flexibility is often negligible when compared with piping flexibility of straight pipe perpendicular to the deflection and bends which can ovalize under in-plane bending moments. However, studies at KBR show branch connections in large diameter pipe can contribute significant flexibility to a close coupled piping system.
Comparison of Limit Load, Linear and Nonlinear FE Analyses of Stresses in a Large Nozzle-to-Shell Diameter Ratio Application
Authors: Porter Michael A. , Massey Steven R. , Martens Dennis H.
Published: August 2008

The analyses address a nominal 62-inch diameter nozzle in a nominal 124-inch diameter shell with a reinforcement pad. The nozzle is in a channel of a heat exchanger. This results in stiffening of the shell (adjacent to the nozzle) by the tube sheet and the channel head. The results of a WRC 297 analysis, linear elastic analysis, limit load analysis and plastic analysis are compared. The finite element analyses were accomplished utilizing commercial software and typical modeling techniques. As there is significant variance in the results derived with the different methodologies, the authors discuss the comparison of the results.
Slip Blinds at Higher Pressures
Authors: Taagepera Jaan , La Bounty Don
Published: August 2008

When maintaining equipment or piping, it must be isolated to assure a safe working environment. Separating flange pairs and inserting a blind flange against the process side prevents hazardous substances from entering the work area. Slip blinds are often used for this type of service. Slip blinds, however, are generally limited to low pressure service since at excessive pressures the blind will become dished and may leak or become impossible to remove. In this paper, slip blinds of various sizes were hydrostatically tested to determine their deformation as a function of pressure. Nonlinear finite element analysis was used to determine the theoretical deformation of slip blinds. The goal of the testing and FEA was to determine the pressure required to permanently deform a 1/4” thick slip blind by one half its thickness.
Design and Analysis of Open Rack LNG Vaporizer
Authors: Hisada Norihiro , Sekiguchi Masaru
Published: August 2008

The dominating LNG Vaporizer is the Open Rack Vaporizer, which uses seawater for the heat source. This Vaporizer is designed to exchange heat between LNG of −160°C and seawater of ambient temperature, thus resulting in phenomena such as the vaporization of LNG inside heat exchanger tubes and the icing of seawater on the external surface of the heat exchanger tubes, which brings about difficulties in the thermal design. Since the ORV is the heat exchanger that makes a significant difference in temperature and needs a rapid startup or shutdown, appropriate considerations should be given to thermal stress. In this connection, through a variety of tests or analysis by the finite element method, highly endurable structures have been established. The thermal design method making it possible to design best-suited shapes (e.g. sizes and internal/external surface shapes) of the heat exchanger tubes through the use of numerical analysis and the thermal stress design of ORV is introduced hereunder.
Ultimate Capacity of Pressurized 90 Deg Elbows Under Bending
Authors: Karamanos S. A. , Tsouvalas D. , Gresnigt A. M.
Published: August 2008

In this paper the response of internally pressurized pipe elbows under bending loads (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the ultimate capacity of 90 deg elbows, focusing on the failure mode (buckling or flattening) and the maximum bending strength. The effects of moderate pressure levels on the ultimate moment and the failure mode are examined extensively.
Recent Design Approaches of Large Bore Piping Exeeding 100 of Ratio D/T
Authors: Mabuchi Toshio , Shinohara Masataka
Published: August 2008

Integration and scale up of utility facilities tend to use large bore pipes which are thinner than ever to reach an optimum design. The size range of pipe from 50” to 120” in diameter and ratio of diameter to thickness (D/t) ranges from 100 to 215 are chosen for the optimum design. These size ranges are outside the scope of conventional standards such as ASME piping codes and pipe fitting codes. They are treated in a limited manner in the design guide or manual such as provided by AWWA[1]. However these conventional codes shall be paid much attention when extrapolating the design methods beyond the limitation of conventional methods especially for large bore piping. Also as the detailed analysis methods assure reliable operation, the current design method by using Finite Element Analysis (FEA) has been proposed. It is applied to deal with piping design for the large bore piping in recent overseas projects, such as for the layout of piping, stress concentration on pipe fittings, optimum saddle configurations, and special heavy duty anchor.
Reliability Testing of Pressure Relief Valves
Authors: Gross Robert E.
Published: August 2008

Following a brief description of pressure relief valves, this paper presents as-found set point test results for pressure relief valves that have been in process or utility system service. The paper examines the reliability of the relief valve to open at set pressure as a function of several key parameters, including time in service, fluid, size, and valve design (vendor). Although it may be that steam and water service valves are affected adversely by service conditions, this analysis is focused primarily on clean air/gas service. The probable correlation between fluid cleanliness and reliability is not being made, but will be considered in future studies. Valves that discharge outside allowable ASME tolerances are evaluated to determine possible causes of the deviation. Three failure case studies are presented. A final summary of test results indicates that valve reliability is not a strong function of time in service for the one-to-five year operating periods investigated. Additionally, this data set indicates that less than one percent (0.96%) of all valves pop tested at greater than 1.4 times tag set pressure.
An Iterative Approach for the Treatment of Nonlinear Supports in the Dynamic Analysis of Piping Systems
Authors: Dweib Ahmed H.
Published: August 2008

An iterative approach for the dynamic analysis of piping systems with nonlinearities in the support system is presented. This approach of analysis is based on the use of describing functions technique to obtain quasilinear approximators for the nonlinearities. The quasilinear approximator form and parameters depend on the form and parameters of the input excitation to the system. The describing functions representation is used iteratively in a linear dynamic analysis of the system. This iterative approach can be applied to different types of dynamic analyses employed in the design of piping systems. The iterative method of analysis is presented for the analysis of piping systems with gap and dry friction nonlinearities present in the supports. This method of analysis, which can be integrated into linear elastic analysis programs, is used in a case study of the frequency response analysis of a pipeline model.
Classification of Thermal Piping Loads Using Limit Load Analysis
Authors: George Shiju V. P. , Seipp Trevor G. , Morrison Shawn W.
Published: August 2008

Equipment nozzle loads essentially originate from sustained (gravity) sources and restraint of the free thermal displacement of the attached piping. A common practice has been to assume that these thermal piping loads develop only secondary stresses. That is, a 1.5Sm [2] check on membrane stress intensities arising from thermal piping loads is typically not performed. The key assumption used in support of this approach has been that these loads decay appreciably with local shell deformation such that the associated stresses are truly self-limiting in nature. This paper illustrates that this assumption may not be appropriate in all instances. A typical pressure vessel and piping configuration is examined. In this example, the associated stresses and deformations developed due to thermal piping loads resulted in significant deformation of the shell arrangement. In static evaluations of local stresses in shells, the ASME Code only offers two classifications that may be applied to stresses resulting from thermal piping loads: primary or secondary. Given these results it may be more reasonable to treat thermal piping load membrane stresses as being primary.
Determination of Critical Temperature of Compressed Non-Asbestos Fiber Sheet Gaskets
Authors: Cipolatti Carlos F. A. , de Sousa Ana M. F. , Veiga Jose´ C. C.
Published: August 2008

Temperature and pressure limits of compressed non-asbestos gaskets have always been of interest to end users, as well as the gasket industry. Since flanges up to class 300 cover the majority of industrial applications of compressed fiber gaskets, a proposed procedure has been developed to clearly document the effect that temperature has on leak rate of the gasket at the maximum internal flange pressure. Different types of non-asbestos compressed gaskets were tested and results showed that for each material, there is a critical temperature after which leakage increases significantly.
The Reduction of Bolt Load in Bolted Flange Joints Due to Gasket Creep-Relaxation Characteristics
Authors: Kobayashi Takashi , Hamano Kota
Published: August 2008

It is known that the bolt loads of gasketed flanged joints decrease in some degree after the assembly due to the creep-relaxation characteristics of gasket. If the bolt loads are greatly reduced, the emission from flanged joints may increase and serious accidents shall occur if things come to the worst. The effect of the creep-relaxation characteristics on the bolt loads of gasketed flanged joints must be clarified. A gasketed bolted joint, in which two hollow cylinders and a gasket is tightened by a set of nut and bolt, is used to clarify the effects of the creep-relaxation characteristics of gaskets on the reduction of bolt loads in this paper. We tried to clarify the phenomena and necessary modeling and experiments were carried out. It is pointed out that the reduction of bolt load cannot be overlooked when stiffer bolts are used in gasketed joints.
Effects of Flange Rotation on the Sealing Performance of Pipe Flange Connections
Authors: Takaki Tomohiro , Satou Kouji , Yamanaka Yuki , Fukuoka Toshimichi
Published: August 2008

In the pipe flange connection with a raised face, the non-uniform gasket contact stresses in the radial direction are occurred due to the flange rotation. The gasket contact stress distributions have dominant effects on the sealing performance of the pipe flange connection. However, the leak testing of a gasket is usually performed under the uniform gasket contact stress using the rigid platen. It is very important to establish a method which predicts the leak rate from the actual pipe flange connection using the results of the leak test conducted under the ideal condition. To do so, there is a need to know the sealing performance of the actual pipe flange connection. In this study, the leakage tests and the finite element simulations are conducted for some pipe flange connections with different gasket width and different flange thickness, which might cause different flange rotation angle. The effects of the flange rotations on the sealing performance and the mechanical behavior of the pipe flange connection are examined.
Effective Bolting Up Procedure Using Finite Element Analysis and Elastic Interaction Coefficient Method
Authors: Takaki Tomohiro , Fukuoka Toshimichi
Published: August 2008

Achieving uniform bolt preloads is an important and difficult issue, when bolting up a pipe flange connection with a number of bolts. Repeated bolt-up operations are, therefore, commonly conducted to get uniform bolt loads. In this study, an effective one-pass bolting up procedure to get uniform bolt loads is proposed by using finite element analysis with elastic interaction coefficient method being incorporated. Furthermore, multi-pass bolting up procedure is also examined to avoid high initial bolt clamping forces that might be generated in the one-pass tightening. These procedures are applied to class 300 lb 20 inch flanges with solid-metal flat gasket and compressed asbestos sheet gasket. The validity of the procedures is substantiated by conducting bolting up experiment using calculated initial clamping forces.
“Harmonized” Gasket Testing
Authors: Schaaf Manfred , Schoeckle Friedrich , Bartonicek Jaroslav
Published: August 2008

The last years there has been a great effort on research and development on gasket testing for bolted joints in Europe and in North America. In Europe, a new standard for the calculation of flanged joints (EN 1591) was developed by the Technical Committee TC 74 of the European Committee for Standardization (CEN). This standard requires gasket factors which must be determined in accordance to the testing standard EN 13555. In North America, the ASTM Committee F03 on Gaskets was established to implement PVRC developed gasket test procedures in the code. Since many companies are operating worldwide, there is an interest in “harmonized” gasket testing procedures to minimize the costs and to raise the effectivity of the tests performed. Several information exchange meetings on gasket constants and gasket testing have been held, and there have been many discussions concerning the difference between the European and the American test procedures. Up to now, only the test procedure for leakage tests has been “harmonized”. Although there are still some differences in detail, the European gasket constants as well as the PVRC parameter can be determined with the new definition of the test procedure, theoretically. In this paper some tests are evaluated in both ways, the results show some mismatch. More tests (with several gasket materials) are necessary to prove the reliability of this procedure.
Effect of Aging Time on Sealing Performance of Non-Asbestos Gasket at Elevated Temperature
Authors: Tsuji Hirokazu , Kitagawa Hirokazu , Kodaira Noriyoshi
Published: August 2008

Tests were concluded by a testing apparatus for ROTT/HOTT, which could continuously control the gasket temperature up to 450°C, under either the stress controlled condition or the strain controlled condition, while the conventional tests were conducted under the stress/strain mixed condition with the temperature fluctuation. The sealing performance of asbestos and non-asbestos gaskets was examined. For the non-asbestos SWG (Spiral wound gaskets) tested by the HOTT, the values of Tp at temperature 210°C and 300°C are distributed over 103∼104, while the value of Tp at 420°C is shifted to the relatively lower level of 102∼103. The non-asbestos SWG has same sealing performance as the substitute for the asbestos SWG between 210°C∼420°C. The PHOTT (Preheated Hot Operational Tightness Test, proposed in this study) is also carried out to compare the evaluation of sealing performance at 300°C with that at 210°C. The difference of sealing performance between the HOTT and the PHOTT at 300°C appears. The PHOTT is unavailable as a simplified substitutive test for the HOTT.
Measurement of Residual Stresses in a Type 316H Stainless Steel Offset Repair in a Pipe Girth Weld
Authors: Hossain S. , Truman C. E. , Smith D. J. , Bouchard P. J.
Published: August 2008

This paper presents measurements of the in-plane residual stress components through the wall of a 218mm long, 26mm deep repair weld, offset by 7mm from the centreline of a girth weld joining two type 316H stainless steel pipes approximately 37mm thick. The measurements were obtained using the deep hole drilling technique. Two locations were examined: (i) mid-length of the repair weld and (ii) the stop-end of the repair. Both measurements were taken along the girth weld centreline. The distributions and magnitudes of the measured longitudinal and transverse stress components at the two locations were very similar over the outer half of the pipe wall. Over the inner half of the pipe wall both components of stress were found to be significantly more compressive at the stop-end of the repair than at mid-length. In general, the transverse residual stresses were found to be lower than the longitudinal residual stresses at both locations. The measured stress profiles are compared with predicted residual stresses from a three dimensional finite element analysis for a similar weld repair.
3-Dimensional Repair Weld Simulations: Bead Sequencing Studies
Authors: Elcoate C. D. , Dennis R. J. , Bouchard P. J. , Smith M. C.
Published: August 2008

In current 3-dimensional multi-pass repair weld simulations each pass is generally modelled as a single continuous weld bead using either a simultaneous bead deposition or a progressive bead deposition moving heat source approach. In reality the length of typical manual metal arc (MMA) repair welds often necessitates the use of multiple weld beads for any individual pass. To investigate the modelling assumptions associated with this approximation a series of results are presented that simulate the deposition of a multi-bead, single MMA weld pass on a stainless steel flat plate. The simulations make use of a fabricated single bead weld test specimen to define the welding conditions. A number of different heat source models and bead sequencing scenarios have been investigated. These include moving heat source simulations, simultaneous bead laying methods (also called “block-dumped” methods) and combinations of the two. The work provides a useful insight into how certain modelling approximations affect weld residual stress distributions. It is concluded that moving heat source end effects are not sensitive to modelling assumptions made in weld beads remote from the stop end. However, residual stress predictions at the mid-length of a multi-bead weld pass on a flat plate are sensitive to the modelling assumptions. In particular, modelling each bead of a multi-bead weld pass can increase the stresses at mid-length relative to a simulation that deposits the whole pass in one go. One further observation made is that modelling the central bead of a multi-bead weld pass using a block-dumped technique (allowing a symmetry boundary condition to be used perpendicular to the weld bead) can result in inaccurate or misleading results.