bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamic Considerations in the Thermodynamic Analysis of Organic Rankine Cycles
Authors: Mondejar Maria E. , Thern Marcus , Genrup Magnus
Published: November 2014

Due to the increasing interest of producing power from renewable and non-conventional resources, organic Rankine cycles are finding their place in today’s thermal energy mix. The main influencers on the efficiency of an organic Rankine cycle are the working fluid and the expander. Therefore most of the research done up to date turns around the selection of the best performance working media and the optimization of the expansion unit design. However, few studies consider the interaction of the working fluids in the turbine design, and how this fact can affect the overall thermodynamic cycle analysis. In this work we aim at including the aerodynamic behavior of the working fluids and their effect on the turbine efficiency in the thermodynamic analysis of an organic Rankine cycle. To that end, we proposed a method for the estimation of the characteristics of an axial in-flow turbine in an organic Rankine cycle simulation model. The code developed for the characterization of the turbine behavior under the working fluid properties evaluated the irreversibilities associated to the aerodynamic losses in the turbine. The organic Rankine cycle was analyzed by using IPSEpro process simulator. A set of candidate working fluids composed of selected organofluorines and organochlorines was chosen for the analysis. The thermophysical properties of the fluids were estimated with the equations of state implemented in Refprop. Results on the energy and exergy overall performances of the cycle were analyzed for a case study with standard source and sink temperatures. For each fluid the number of stages and geometry of the turbine were optimized. It was observed that some working fluids that could initially be considered as advantageous from a thermodynamic point of view, had an unfavorable impact on the turbine efficiency, thus increasing the irreversibilities of the cycle. We concluded that if the influence of the working fluid on the turbine performance is underestimated, the real performance of the organic Rankine cycle could show unexpected deviations from the theoretical results.
Ocean Thermal Energy Conversion (OTEC) as Base Load Renewable Power
Authors: Shapiro Laurence J.
Published: November 2014

Ocean Thermal Energy Conversion (OTEC) is a form of renewable solar energy that has the capability to provide 24 hour base load, dispatchable power to electrical systems. This is a major advantage over solar PV and wind, which are intermittent and can have significant adverse effects on grid stability once penetration exceeds 10% of grid capacity. This paper describes OTEC technology, suitable areas for implementation, current levels of technology development, regulatory barriers, problems posed by intermittent power generation as well as how it is differentiated from intermittent renewable technologies and can enhance grid stability. The discussion of the OTEC technology will include the underlying thermodynamics, critical heat transfer requirements and efficiency issues associated with low temperature Rankine Cycle applications. The discussion of suitable areas for implementation will include required ocean temperatures, ocean topography, current fuel dependence and regulatory issues to be addressed. The discussion of problems posed by intermittent power generation on networks will include transient response of grids to sudden changes in production as well as ramp rate requirements as solar PV comes on and off line on a daily cycle. OTEC, as a base load generation source, will be discussed in terms of market factors and reserve requirements.
Model Based Performance Correction Methodology — A Case Study
Authors: Zuniga Koldo , Schmitt Thomas P. , Clement Herve , Balaco Joao
Published: November 2014

Correction curves are of great importance in the performance evaluation of heavy duty gas turbines (HDGT). They provide the means by which to translate performance test results from test conditions to the rated conditions. The correction factors are usually calculated using the original equipment manufacturer (OEM) gas turbine thermal model (a.k.a. cycle deck), varying one parameter at a time throughout a given range of interest. For some parameters bi-variate effects are considered when the associated secondary performance effect of another variable is significant. Although this traditional approach has been widely accepted by the industry, has offered a simple and transparent means of correcting test results, and has provided a reasonably accurate correction methodology for gas turbines with conventional control systems, it neglects the associated interdependence of each correction parameter from the remaining parameters. Also, its inherently static nature is not well suited for today’s modern gas turbine control systems employing integral gas turbine aero-thermal models in the control system that continuously adapt the turbine’s operating parameters to the “as running” aero-thermal component performance characteristics.

Accordingly, the most accurate means by which to correct the measured performance from test conditions to the guarantee conditions is by use of Model-Based Performance Corrections, in agreement with the current PTC-22 and ISO 2314, although not commonly used or accepted within the industry.

The implementation of Model-based Corrections is presented for the Case Study of a GE 9FA gas turbine upgrade project, with an advanced model-based control system that accommodated a multitude of operating boundaries. Unique plant operating restrictions, coupled with its focus on partial load heat rate, presented a perfect scenario to employ Model-Based Performance Corrections.
Ten Years of California Distributed Combined Heat and Power: Living Up to Expectations
Authors: Marin William , Simons George , Scheuermann Kurt , O’Kelly Myles
Published: November 2014

In the last 20 years, emerging technologies such as fuel cells and microturbines have contributed to growth in the market for combined heat and power (CHP) in small-scale (5–5,000 kW) applications. Numerous studies utilizing performance assumptions have explored the theoretical potential for distributed CHP to save energy and reduce greenhouse gas (GHG) emissions, however actual performance may differ from expectations. Incentive programs in several states are beginning to yield information about actual (as opposed to potential) performance of small-scale CHP. This paper leverages over ten years of metered data from more than 500 different projects rebated by one such program: California’s Self Generation Incentive Program (SGIP). The population of projects includes established technologies (internal combustion engines, gas turbines) as well as emerging technologies. Performance measures examined include efficiencies, utilization, and GHG emissions impacts. A variety of Federal and State policies seek to increase the amount of small-scale distributed CHP in the coming years. It is imperative that knowledge about actual performance gleaned from metered data collected during the past decade be shared widely so that CHP’s potential to reduce energy consumption and GHG emissions is actually realized in the future.
Spectral Mismatch Correlated With Air Mass Under Varying Clear Sky Conditions for Photovoltaic Facilities With Crystalline-Silicon Modules: Solar Spectral Effects — An EPC Contractor’s Perspective
Authors: Johnston Paul
Published: November 2014

Photovoltaic utility-scale grid-connected power generation facilities have performance guarantee bases that often include a reference solar spectrum. EPC contractors are obligated to correct tested performance for solar spectrum, as is done for irradiance and cell temperature, to judge whether contractual performance guarantees have been satisfied. Air mass correlated with solar spectral irradiance offers a convenient way of accomplishing this. This paper offers an improvement in the versatility and accuracy of accounting for spectral effects in this manner. The effects on the spectral composition by atmospheric constituents, like aerosols and water vapor, are investigated. Spectral mismatch curves are derived that characterize the responses of the PV modules and the irradiance measurement device to both the estimated test and the reference solar spectra. Comparison of several supplier performance curves and spectral mismatch curves reveals significant discrepancies. An improvement in accuracy is proposed by the use of supplier spectral response data and estimated solar spectral profiles. Correcting for spectral effects has minimal impact at air mass values near the 1.5 reference value, but grows in significance with increasing air mass. Greater precision in accounting for solar spectral effects on PV plant performance is expected as this segment of the power generation industry matures. This paper proposes a methodology that addresses this expectation.
Improve Boiler Reliability With Unit Specific Strategic Planning
Authors: Hamblin-Smoske Pamela
Published: November 2014

Boiler tube failures remain the leading cause of lost availability in power boilers across global markets. The need for strategic planning in regard to inspections, preventative maintenance and targeted replacements has never been greater. Identifying the root problem(s) is essential and must be properly managed for continued safety, reliability and availability.

The process associated with integrating a boiler management program can be viewed as an insurmountable obstacle for many utility operators and owners. In many cases, the cookie cutter approach that is often used results in insufficient reliability recovery. However, using modern technology and tactics to strategically manage and properly identify specific operating and design conditions has proven exceedingly successful in reducing a unit’s forced outage rate [EFOR].

Specific challenges plants are faced with include the reduction of onsite engineers, aging workforces and equipment, and the need to remain competitive in a challenging global energy market. Plant managers are routinely faced with the complex task of determining the current condition of their equipment, forecasting outage budgets and schedules, and performing risk assessments. Additionally, insurance companies are increasingly requiring inspection and maintenance records that are not always up-to-date or readily available. The solutions to reducing the EFOR of a unit involves taking a comprehensive approach to boiler management utilizing unit specific operational training, advanced data management, and strategic inspection, maintenance and replacement prioritization. Implementing this comprehensive approach has awarded millions in savings for plant managers that have adopted this strategy. Implementing a unit specific, target driven, and strategic plan enables utility owners and operators to succeed in today’s competitive market by increasing the unit’s reliability and availability without sacrificing safety or environmental standards.

Thielsch Engineering, Inc. developed a program titled: 4-SYTE System Strategy that is currently utilized in more than 60 power plants within the United States and Canada. Unit specific strategic planning is necessary for all facilities that rely on these critical components. Advanced technology must be adopted by all energy producers to ensure they remain competitive and profitable.
Automatic Fault Location on Distribution Networks Using Synchronized Voltage Phasor Measurement Units
Authors: Lee Jonathan
Published: November 2014

Automatic fault location on the distribution system is a necessity for a resilient grid with fast service restoration after an outage. Motivated by the development of low cost synchronized voltage phasor measurement units (PMUs) for the distribution system, this paper describes how PMU data during a fault event can be used to accurately locate faults on the primary distribution system. Rather than requiring many specialized line sensors to enable fault location, the proposed approach leverages a PMU data stream that can be used for a variety of applications, making it easier to justify the investment in fault location. The accuracy of existing automatic fault location techniques are dependent either on dense deployments of line sensors or unrealistically accurate models of system loads. This paper demonstrates how synchronized voltage measurements enable sufficiently accurate fault location with relatively few instrumentation devices and relatively low fidelity system models. The IEEE 123 bus distribution feeder is examined as a test case, and the proposed algorithm is demonstrated to be robust to variations in total load and uncertainty in the response of loads to voltage sags during a sample set of varied fault conditions.
Soot Formation Reaction Effect in Modeling Thermal Partial Oxidation of Jet-A
Authors: Scenna Richard , Gupta Ashwani K.
Published: November 2014

The results obtained from the modeling of thermal partial oxidation of kerosene based Jet-A fuel are presented using one dimensional chemical modeling. Two detailed kinetic models for alkenes chemistry ranging between C8 to C16 were evaluated and compared against experimental data of thermal partial oxidation of Jet-A fuel. The key difference between these two kinetic models was the inclusion of model for soot formation reactions. Chemical modeling was performed using dodecane to represent Jet-A fuel.

The results showed that the model with soot reactions was significantly more accurate in predicting reformate products from Jet-A. In particular, the formation of carbon monoxide, methane and acetylene closely followed the experimental data with the model that included soot formation reactions. The results revealed that the soot formation reactions promoted the smaller hydrocarbons to decompose via the alternate kinetic pathways and from additional radical formation. The results also reveal that the inclusions of soot formation reactions are critical in the modeling of thermal partial oxidation of fuels for fuel reforming.
Maryland Poultry Litter Biomass Power Plant Study
Authors: Bose Prodip , Hashemian-Nik Mehdi , Clark Tony
Published: November 2014

The state of Maryland issued a Request for Proposal to solicit exportable electrical power using locally sourced poultry littler as the primary fuel. The overall goal was to promote the use of renewable energy and reduce agricultural runoff to Chesapeake Bay. POWER Engineers (POWER) was brought on to the project team by the selected development contractor to provide a preliminary level design and high level cost estimate for the feasibility study and technology investigation. POWER’s scope included:

• Preliminary engineering for boiler technology selection and sizing

• Selection of fuel handling equipment and logistics

• Providing an air emissions estimate

• Water quality and demand requirements

• Developing an engineering and construction cost estimate

POWER determined that to produce 20.4 MW of electricity and process steam, it would take roughly 60 truckloads of 100% poultry litter waste-per-day to run the plant. The bubbling fluidized bed boiler technology developed by ANDRITZ for biomass applications and fully automated fuel handling system would make this biomass plant the first-of-its-kind in the United States. POWER’s team was able to reach out into new and different areas of technology and take a new approach to biomass facility design.
Leveraging Natural Gas: Technical Considerations for the Conversion of Existing Coal-Fired Boilers
Authors: Lee Jason C. , Coyle Michael
Published: November 2014

With availability of natural gas at competitive prices and increased scrutiny of coal-fired generation, conversion of coal-fired units to natural gas-firing is a popular option to consider as an alternative to capital-intense environmental equipment upgrades or even retirement. Many owners are considering this option as a way to keep an existing plant open while meeting new and pending environmental regulations. There are many technical challenges associated with such a conversion and the owner should consider them all carefully on a case-by-case basis. This paper will present an overview of these challenges, with a focus on the steam generator and what an owner/operator needs to understand when considering conversion to natural gas-firing.

Typical effects of a conversion to natural gas-firing for a utility-scale coal-fired steam generator are discussed along with potential operational effects of such a project. A general discussion of differences in furnace and convective pass performance characteristics for the different fuels is presented along with a discussion of how these differences can translate to technical challenges in a conversion project. Typical effects on boiler efficiency and emissions as well as the most commonly required modifications are reviewed. Finally, a comprehensive review of the operational affects of the converted unit is presented.
Mixed Weibull Distribution as Best Representative of Forced Outage Distribution to be Implemented in BlockSim
Authors: Carlucci Elisa , Tognarelli Leonardo
Published: November 2014

When an RBD is required, Failure distribution and Outage distribution are requested as inputs for each block.

Should field data exist, the two distributions can be obtained by managing data in the most appropriate manner. While the Failure distribution is often a right censored data set, the outage distribution is always a time-to-failure distribution obtained through the RRX interpolation. Moreover, being the reliability approach conservative, the weibull 3P assumption is welcome, because the gamma value, in this particular circumstance, guarantees a minimum outage duration. However it has been noticed that while the 2P sometimes could be not-conservative enough, the 3P could result too much conservative with the risk of declaring a lower target than the actual one and hence with the consequence of not being commercially competitive. The proposed approach applies and develops the mixed weibull application, where each subpopulation distribution comes out from a single dataset, which represents a step forward after the traditional 2P and the more conservative 3P.
Software Based Barriers to Integration of Renewables to the Future Distribution Grid
Authors: Stewart Emma M. , Kiliccote Sila
Published: November 2014

The future distribution grid has complex analysis needs, which may not be met with the existing processes and tools. In addition there is a growing number of measured and grid model data sources becoming available. For these sources to be useful they must be accurate, and interpreted correctly. Data accuracy is a key barrier to the growth of the future distribution grid. A key goal for California, and the United States, is increasing the renewable penetration on the distribution grid. To increase this penetration measured and modeled representations of generation must be accurate and validated, giving distribution planners and operators confidence in their performance. This study will review the current state of these software and modeling barriers and opportunities for the future distribution grid.
Capacity Control Systems of LDPE Compressors and Influence on Cylinder Valves
Authors: Giacomelli Enzo , Raggi Andrea , Giampà Antonio , Vaglini Claudio
Published: November 2014

Booster, Primary and Hyper compressors are the pieces of machinery used to reach the extremely high pressures needed for the reaction in Low-Density Polyethylene plants. Wide operating ranges are necessary due to the different products and conditions required by the process to obtain both homo and co-polymers required by the market. A suitable capacity control system has to be studied during the design phase to optimize the operation particularly for Booster and Primary compressors, that are supplying the required flow to the Hyper, then compressed to the reactor. In the latter the traditional capacity control cannot be used because of the very high pressures involved and for start-up and various preparation activities the by-pass along the reactor is the only flow regulation possibility. On the contrary, in Booster and Primary there is a wider choice of CCS, from “clearance pockets” to “variable speed drive”, from step to step-less.

This paper gives a brief overview of these systems, explains their pros and cons and examines the impact they have on valve behaviour explaining the CCS-valve interactions. In particular it focuses on the new generation of electro-mechanical step-less control systems.
High Strain Rate Constitutive Modeling of Pure Titanium Using the Taylor Impact Test
Authors: Barkey Mark E. , Ball Haleigh , Jones Stanley E. , Dong Pingsha
Published: November 2014

High strain rate mechanical properties of this material are required for the structural design of ship components for advanced naval applications. Taylor cylinder specimens were machined from pure titanium plate stock proposed for use in ship building. Since the specimens were machined from plate stock, it was assumed that the processing of the plate induced anisotropic behavior. To assure that all the effects would be captured by the tests, specimens were machined in the rolling direction, transverse direction, and 45° to the rolling direction in the plane of the plate. Indeed, distinct differences were observed in the rolling and transverse directions. Specimens in the 45° direction also showed the unsymmetrical deformation field that is associated with anisotropy. There was modest anisotropy in the thickness direction. However, the analysis of the data from the tests required corrections to accommodate this effect.

Data from these tests can be reduced using two distinct methods; a one-dimensional theory and a finite element analysis with a conventional constitutive model adjusting the free parameters until the specimen geometry is matched. While the second method usually produces excellent results, we will employ a one-dimensional analysis that was proposed several years ago by one of the authors in this paper. In order to effectively apply such a theory, very low scale specimens, in this case 0.164-inch diameter, are required. The use of such low diameter specimens demands accurate measurement of the specimen profile. The recovered specimens were measured with a laser micrometer and the results were used to find estimates of quasi-static compressive stress and compressive stress at strain rates exceeding 104/sec.

Some scatter in the data from these tests was observed. This was mostly due to some variations in the initial specimen diameter. Pure titanium presents a machining challenge for conventional equipment, when a tolerance of a thousandth of an inch is required. The scatter in Taylor cylinder data can be mitigated by conducting a large number of tests. However, in this case, many of the specimens that did not meet the criteria for success were discarded. Nevertheless, the results are very convincing.
Managing Transient Operating Conditions of Hyper Compressors
Authors: Agostini Marcello , Carcasci Cosimo , Cristofani Alessio
Published: November 2014

Special reciprocating compressors are required to reach the very high pressures necessary to feed the reactors used in LDPE plants. The working conditions of the compressors are determined by the reactor operating pressures and are considered for evaluation of the loads, torsional, pulsation and vibration conditions.

Performance and safety are key considerations and operator experience is essential for optimal and safe plant operation. Plant automation contributes to safety and optimizes process conditions.

The compressor start-up and shutdown procedures, commonly detailed in maintenance manuals, are analyzed studying the operating parameters to draw up guidelines for avoiding damage to plunger seals and keeping loads within design limits, without compromising the design performance. The multiple gas compositions of co-polymers and the fact that gas expansion can cause a reduction in temperature, need adequate consideration to avoid damage caused by polymer inside the compressor cylinders.

The paper will also give recommendations on the necessary procedures to reach the operating pressures with correct distribution of the total pressure ratio between the two stages.

These will also include the requirement of minimum pressure on the plunger head to maintain contact with the crosshead and avoid failure of such a brittle component.
Stress Intensity Factor Influence Coefficients for Semi-Elliptical Axial Surface Flaws for Cylindrical Components With Large Thickness to Radius Ratios
Authors: Glunt Nathan , Udyawar Anees , Ng Christopher
Published: November 2014

Flaws detected in nuclear power plant components during in-service inspections are typically evaluated based on stress intensity factor influence coefficient databases and solutions from industry standards and public literature (e.g. API-579, ASME Section XI Code, WRC-175 Bulletin, Raju-Newman, etc). For certain components in the Pressurized Water Reactor (PWR) nuclear power plants, such as Bottom Mounted Instrumentation (BMI) nozzles, the cylindrical component geometry may fall outside the applicability limits of stress intensity factor influence coefficient databases. This situation occurs where the thickness to inner radius ratios of the cylindrical geometry is greater than 1.0. Accurate stress intensity factor (SIF) solutions are essential to flaw evaluation since the SIFs are used in the determination of both the allowable flaw size and crack growth in order to determine acceptability of the detected flaw.

In this paper, stress intensity factor influence coefficients are generated based on a three-dimensional finite element analysis for axial flaws located on the inside surface and outside surface of a cylindrical component with thickness to inner radius ratios (t/Ri) of 1, 2, 4, & 6. Non-dimensional influence coefficients are determined at the deepest point of the crack front and the surface point of the flaw based on a 4th order polynomial fit for a through-wall stress profile. The influence coefficients are generated for semi-elliptical flaws with a/c ratios = 0.125 through 2; where a is depth of the elliptical flaw, and c is the half-length of the elliptical flaw. The influence coefficients developed are suitable for calculating stress intensity factors for cylindrical components with high thickness to inner radius ratios.
Wake Interference Effects for Two Surface-Mounted Finite Cylinders in a Tandem Configuration
Authors: Sumner David , Li He
Published: November 2014

The mean wake of two identical surface-mounted finite-height circular cylinders arranged in a tandem configuration was investigated in a low-speed wind tunnel using a seven-hole pressure probe. The Reynolds number was Re = 2.4×104, the cylinder aspect ratio was AR = 9, and the boundary layer thickness on the ground plane relative to the cylinder height was δ/H ≈ 0.4. Three centre-to-centre longitudinal pitch ratios of L/D = 1.125, 2, and 5 were examined, corresponding to the extended-body, reattachment, and co-shedding flow regimes, respectively. Reference measurements were also made in the wake of a single finite circular cylinder of AR = 9. For the tandem configurations, velocity measurements were made behind the downstream cylinder in two orthogonal vertical planes. Compared to the wake of the single surface-mounted finite-height circular cylinder, the mean downwash and upwash flows for the tandem cylinders, behind the downstream cylinder, were weaker, the mean recirculation zone behind the downstream cylinder was shorter, and the mean wake extended higher above the ground plane, for all three pitch ratios. Marked changes were also observed in the mean streamwise wake vortex structures, compared to the case of the single finite cylinder. For the extended-body and reattachment flow regimes, the tip vortex structures became elongated in the wall-normal direction. In the co-shedding regime, two sets of tip vortices were observed, with the second set possibly originating from the upstream cylinder.
Numerical Evaluation of Wall Thinning Profile in Separation and Union Pipe due to Flow Accelerated Corrosion
Authors: Watanabe Shun , Yoneda Kimitoshi
Published: November 2014

Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in power plants with high priority. In Japan, its management has been conducted with conservative evaluation of thinning rate and residual lifetime of the piping based on wall thickness measurements. However, noticeable case of the wall thinning occurred at separation and union pipe. In such pipe system, it is a problem to manage a section beneath reinforcing plate of T-tube pipe and a crotch of T-joint pipe; wall thickness measurement with high accuracy is difficult to conduct in the region by using ordinary ultrasonic testing devices. In this study, numerical analysis for separation and union parts of T-tube and T-joint pipes was conducted, and wall thinning profile by FAC was evaluated by calculating mass transfer coefficient and geometry factor. Based on these results, applicable wall thinning management for T-tube and T-joint pipes was considered. In the case of union flow from main and branch pipe, the wall thinning profile of T-tube showed the tendency of increase at main pipe like semielliptical region. On the other hand, noticeable profile appeared at crotch in T-joint although it was found that geometry factor of T-joint in this flow pattern was half the value of T-tube. An alternative evaluation method to previous one might be needed for such semielliptical region in T-tube and crotch in T-joint.
3D CFD Simulation of Water Hammer Through a 90° Bend: Applicability of URANS, 3D Effects and Unsteady Friction
Authors: Riedelmeier Stefan , Becker Stefan , Schlücker Eberhard
Published: November 2014

In most cases, the method of characteristics is used to calculate the propagation of water hammer in hydraulic systems due to the size of those pipings, although three-dimensional effects are known to occur. In order to investigate and quantify these effects, a three-dimensional computational fluid dynamics simulation of water hammer through a bend geometry was performed. For the resolution of the developing high spatial and temporal gradients an adequate mesh and suitable physical model was generated using a commercial code. The applicability of unsteady Reynolds-averaged Navier-Stokes simulation was evaluated considering the turbulent properties of the flow using results from the literature. Furthermore velocity, pressure, wall shear stress and vorticity distributions are presented. The effect of the 90° bend as three-dimensional element was identified and the impact on the flow field is presented. In the end, the annular effect is discussed. Due to the high forces of inertia in the boundary layer and the dominating viscous forces close to the wall, high velocity gradients are developing resulting in high wall shear stresses. It is shown that the viscous and turbulent transport of momentum in the radial direction reduces these velocity gradients and limits the maximum occurring wall shear stress.
Assessment of Weep Holes in Cylindrical Shell Based on Elastic-Plastic Stress Analysis Method
Authors: Chandiramani Dipak K. , Nawandar Suresh K.
Published: November 2014

In urea plant equipment, particularly those operating in the synthesis cycle, anti-corrosive liner plates are usually applied to the pressure retaining carbon steel vessel walls. Even with the correct material selection, controlled fabrication methods and maintenance, the risk of highly corrosive urea-carbamate solution leaking through these liners always exists in these equipment which might eventually damage the carbon steel walls.

Existing designs of these equipment utilizes “weep holes” to reveal such leakages. Various designs exist, but in general these weep holes are 15–20mm dia. plain openings in the vessel walls connecting the space between the liner and the vessel wall to the outside atmosphere or the leak-detect apparatus.

These equipment operate at high pressures and temperatures and therefore ASME Section VIII Division 2 is normally the preferred design and construction Code.

This Code, earlier to the publication of its Edition 2007, had provisions in it to exempt openings not exceeding certain diameters, from any reinforcement calculations. Traditionally, equipment designers have been applying this clause to seek the exemption of these weep holes from any further calculations.

However, starting with Edition 2007, this Code did away with such exemptions and has made it mandatory to assess openings of all sizes, particularly if they are in the monobloc vessels. Weep holes are no exception.

This paper discusses how the assessment of these weep holes in cylindrical shells can be carried out by applying the “Elastic-Plastic Stress Analysis Method” stipulated in Para. 5.2.4 & 5.3.3 of the ASME Section VIII Division 2 Code. This paper also provides the basis for recommending this method. In the application of this method, the subject is approached as a “shell with opening” and not as conventional “nozzle opening in the shell”.
A Comparative Study of Valve Natural Frequency Estimation Using Finite Element Analysis (FEA), Raleigh’s Principles and Laboratory Tests
Authors: Ezekoye L. Ike , Vock Preston A. , Farrell Ronald S. , Gradle Richard J.
Published: November 2014

The natural frequency of valves is an important design requirement to ensure that valves do not go into resonance during operation and consequently fail structurally or fail to perform their design and safety related functions. Besides its impact on operability, valve resonance can initiate piping vibration that could damage pipes and their supports; which is undesirable. As important as equipment natural frequency is to valve operability, one would expect that testing should be the de facto method for confirming its value. Ideally, this should be the case, however, cost considerations limit the extent to which testing is used. On the other hand, testing does have some issues with respect to accuracy such as the effect of supporting structure flexibility resulting in a conservatively lower natural frequency measurement. In addition, the multiplicity of valves in nuclear power plants with different designs, sizes and safety classes limit the use of testing to establish valve natural frequencies except when required in the equipment specifications. Frequently, valve natural frequencies are determined by analysis either using finite element techniques (FEA) or by first principles of beam and mass models; the latter being more frequently used. This paper presents the studies performed to correlate valve natural frequency test results to the results derived from analytical techniques using Raleigh’s energy principle and from finite element analysis (FEA) methods. In a previous paper on valve natural frequency [1], Ezekoye et al. presented a model for estimating valve natural frequency by incorporating mass inertia of the valve structures with the more traditional methods that are based on a lumped mass model to determine displacements. In the process, the flexibility of the extended structure (otherwise referred to as the superstructure) and the valve body itself are considered. Using limited test data, Ezekoye et al. showed that there is merit in using their enhanced analysis model. Their correlation was promising. The finite element analysis, on the other hand, is a well-established technique for solving complex structural mechanics problems and should be expected to provide reasonable results comparable to actual valve tests provided the boundary conditions provide a reasonable representation of the actual valves tested. In this paper, ANSYS Version 12.1 was used to model valve natural frequencies. Additionally, a more extensive testing of valves for natural frequency was performed in this paper than was reported in Reference 1. The results of both the FEA and the Raleigh’s principle model as presented in Ezekoye et al. are compared against the test results. By comparing the three results, strengths and weaknesses of each method become apparent. The choice of whether or not one chooses to test or perform analysis depends on the valve specification requirement and the preference of the designer.
A Load Combination Method for Seismic Design of Multi-Degree-of-Freedom Piping Systems With Friction Characteristics and Multiple Support Systems
Authors: Sone Akira , Yamauchi Tatsuya , Masuda Arata
Published: November 2014

A load combination scheme for seismic response calculation of multi-degree-of-freedom (MDOF) piping systems with friction characteristics to multiple support excitations is presented. This scheme has an advantage, such that the “response reduction factor” due to friction is taken into account by use of a stationary random vibration theory approach. Using a simple and analytical 5DOF piping system with friction characteristics to two support excitations, combination law is supplied to various friction characteristics and the maximum responses of piping is calculated. From these calculation results, it is clear that the maximum acceleration responses of piping systems calculated by the proposed scheme are reasonable compared with those by the numerical simulations.
Instrumentation Development and Validation for an Experimental Study of Steam Generator Tube Loading During Blowdown
Authors: Hamouda Ouajih , Weaver David S. , Riznic Jovica
Published: November 2014

A Main-Steam-Line-Break accident in a CANDU nuclear steam generator produces a blowdown in which all the pressurised water is boiled off in a few seconds. The resulting high transient loading on the heat exchanger tubing could lead to their rupture, resulting in the release of radioactive materials out of containment. A better understanding of this phenomenon will permit the development of improved design tools to ensure steam generator safety in the event of such an accident. The paper presents a commissioned experimental rig and instrumentation system, for which a two-phase experimental program has been developed. Using R134a as the working fluid, measurements of temperature, pressure, and tube loading, as well as simultaneous high-speed flow visualisation, have been taken at conditions simulating a full-scale operating steam generator. The experimental results will be used to develop theoretical modelling tools for single and two-phase blowdown, such that an estimate of tube loading during Main-Steam-Line Break can be predicted from initial conditions.
Stability of a Stationary Flexible Cantilevered Plate in an Axial Flow
Authors: Fujita Katsuhisa , Matsumoto Keiji
Published: November 2014

As the flexible plates, the papers in printing machines, the thin plastic and metal films, and the fluttering flag are enumerated. In this paper, the flexible plate is assumed to be stationary in an axial flow although both the stationary plate and the axially moving plate can be thought. The fluid is assumed to be treated as an ideal fluid in a subsonic domain, and the fluid pressure is calculated using the velocity potential theory. The coupled equation of motion of a flexible cantilevered plate is derived in consideration of the added mass, added damping and added stiffness, respectively. The velocity potential is obtained by assuming the unsteady axial fluid velocity to be zero at the trailing edge of a flexible cantilevered plate, neglecting the effect of a circulation. The complex eigenvalue analysis is performed for the stability analysis. In order to investigate the validity of the proposed analysis, another stability analysis is also performed by using the non-circulatory aerodynamic theory. The comparison between both solutions is investigated and discussed. Changing the velocities of a fluid and the specifications of a plate as parametric studies, the effects of these parameters on the stability of a flexible cantilevered plate are investigated.
Improvements to J-Estimation Scheme for Predicting Moment-Rotation Response of Circumferential Through-Wall Cracks in Piping
Authors: Park Jeong Soon , Olson Richard
Published: November 2014

This paper presents improvements to the LBB.ENG2 method for predicting the moment-rotation response of a circumferential through-wall cracked (TWC) pipe under combined tension and bending loads. The LBB.ENG2 method provides closed-form equations for J-integral (J) estimation using a load-displacement relationship, where the Mode I stress intensity factor (K) solution, beam differential equations, and limit load solutions are utilized for elastic and plastic displacements under a thin-shell assumption. Due to its good predictions and simplicity, LBB.ENG2 has been incorporated into the recent probabilistic fracture mechanics codes, PRO-LOCA and xLPR.

The LBB.ENG2 method, however, has a limited applicability inherited from the thin-shell assumption and the K solution. That is, it might yield an unrealistic J for a thick pipe, or very short and long cracks. In this study, improvements are made to the method, and the thin-shell assumption is revisited. First, in order to extend the applicability limit of the K solution and, hence, the limit of the LBB.ENG2 method, newly developed and more accurate K solutions are implemented in a suitable form to derive equations explicitly for prediction of the crack instability point. Second, thin-shell and thick-shell assumptions are compared and technical justification for the use of the thin-shell theory is provided. In addition, based on the LBB.ENG2 method, moment-rotation response curves of circumferential through-wall cracked pipes are generated.
Long-Term Creep Rupture Strength of Individual Heats and Restriction of Al Concentration in 304HTB and 316HTB Stainless Steels for Gen IV Application
Authors: Abe Fujio
Published: November 2014

The long-term creep rupture strength has been investigated for 9 heats of JIS SUS 304HTB (18Cr-8Ni) and for 9 heats of JIS SUS 316HTB (18Cr-12Ni-Mo) steels at 600 to 750 °C, using data in NIMS Creep Data Sheets. The heats with high Al exhibit the significant degradation in creep strength at long times. The formation of AlN and TiN during creep reduces the beneficial effect due to nitrogen. The heat-to-heat variation in time to rupture is analyzed using available nitrogen concentration Nav, which is defined as the concentration of nitrogen free from AlN and TiN, and also using nitrogen to soluble Al ratio (N/sol Al). The Nav clearly explains the observed heat-to-heat variation in time to rupture of 304HTB and 316HTB at long times. The precipitation hardening due to fine NbC carbides and the effect of small amount of Cu cause additional heat-to-heat variation in time to rupture for 304HTB at short times and for 316HTB at long times, respectively. The restriction of soluble Al concentration is proposed to be below 0.038 and 0.033 mass % for 304HTB and 316HTB, respectively, so that the creep rupture strength of 304HTB and 316HTB is larger than the ASME Sec.III-NH values for up to 300,000 h at 650 to 700 °C. At long times above 300,000 h, such as 500,000 h, the concentration of soluble Al should be further lowered.
Evaluation of Subsurface Crack Propagation Under Fatigue
Authors: Serizawa Ryosuke , Kikuchi Masanori , Yamada Shinya
Published: November 2014

There is a proximity rule to calculate residual fatigue life of components in nuclear power plants. It is easy to evaluate soundness of a structure member by using this rule. If a subsurface crack is located near free surface of the structure, this real subsurface crack is transformed to surface crack. The condition to transform subsurface crack to surface crack is defined by relationship between crack size and the distance from crack tip to free surface. However, many organizations proposed proximity rules which differ from each other. It is advisable to verify which rule is preferable in these rules by experiment, but it is difficult to introduce subsurface crack at an optional position. Therefore, numerical simulation is needed for this purpose. Especially, S-version FEM is very useful for as much as model of subsurface crack is independent of global structure, and crack growth is easily simulated.

Both subsurface and transformed surface crack growths are simulated by S-FEM. Subsurface crack grows toward free surface. When subsurface crack tip was touched to free surface, this crack was converted into surface crack by using stress intensity factor calculated at this time. In this way, crack growth behavior from subsurface to surface flaw is represented. By comparing the crack growth rate of surface to subsurface flaw with that of surface flaw transformed by each proximity rule, proximity rules can be verified by numerical simulation.

Authors had proposed the proximity rule at the ASME PVP 2013 conference [1]. However, new rule was proposed by numerical simulation only under cyclic tensile load. In addition, only two proximity rules were studied at the last conference. In this study, the number of proximity rules is increased, and this problem is simulated under other loading condition such as cyclic bending load. New proximity rule gives reasonable and conservative results in numerical simulation.
Structural Health Monitoring of a Concrete Frame Subjected to Shake Table Excitations Using Smart Aggregates
Authors: Chang Wei , Chai Juin-Fu , Liao Wen-I
Published: November 2014

Structural health monitoring of RC structures under seismic loads has recently attracted dramatic attention in the earthquake engineering research community. In this paper, a piezoceramic-based device called “smart aggregate” was used for the health monitoring of a two stories one bay RC frame structure under earthquake excitations. The RC moment frame instrumented with smart aggregates was tested using a shake table with different ground excitation intensities. The distributed piezoceramic-based smart aggregates embedded in the RC structure were used to monitor the health condition of the structure during the tests. The sensitiveness and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses.
The Residual Strength of Breathing Air Composite Cylinders Towards the End of Their Service Life: A First Assessment of a Real-Life Sample
Authors: Mair Georg W. , Scherer Florian , Scholz Irene , Schönfelder Thorsten
Published: November 2014

Emergency response units increasingly use pressure cylinders made from fibre composites for breathing air as elements of personal protective equipment (PPE). Such applications expose the composite cylinders to harsh temperature and handling conditions. At least in Europe, standards have been used for certifying PPE, which are designed and mandatory for the approval of pressure receptacles for the transport of dangerous goods. Therefore, service conditions specific to PPEs are not accounted for in these standards.

In this paper, BAM (Federal Institute for Materials Research and Testing) investigates the residual safety of a composite cylinder design at the end of their designated service life of 15 years. The cylinders (test pressure PH 450 bars; 6.8 Litres) are of one design type with aluminium liner and fully wrapped with carbon fibres, which is commonly considered a “Type III” cylinder. All cylinders were used as PPE by the Berlin fire department and randomly picked in three samples of 25 cylinders each before tested.

At BAM, the cylinder samples underwent hydraulic load cycle tests (LCT), conventional burst tests (BT) and so called slow burst tests (SBT). A concept for quantification of strength degradation already introduced by BAM was applied. This concept is based on a probabilistic assessment of the average strength and scatter of each sample of cylinders. The strength distributions of the used PPE-cylinders is shown and analysed. Some unexpected effects are shown and a refinement of the statistical assessment is introduced.