bluuebunny/crossref_metadata_2025 huggingface dataset:
Firing Tests of Biocoal
Authors: Mody Jaisen , Saveliev Roman , Bar-Ziv Ezra , Perelman Miron
Published: November 2014

As part of PGE-EBC-MTU collaboration of the testing program to fire up to 100% of biocoal in the 600 MW Boardman boiler we produced samples from the seven biomass feedstock: Arundo Donax (AD), wheat waste, corn waste, woody hybrid poplar, and bark from hybrid poplar, woody pine, and bark from pine. The various samples of biocoal were tested in a combustion chamber with the following results: (1) Biocoal was fired and burned providing temperature and gas concentration profiles similar to coal. (2) NOx emission from all biocoal originating from any type of biomass feedstock was found to be significantly lower than that from coal burning. (3) SOx emissions was found to correlate directly to sulfur content in the plant minerals, which is very small for all types of biomass tested. (4) Fouling was quite low for all biocoal tested, such that it can be handled with an optimized water cannons procedure. (5) Minerals in the biocoal were found to segregate from the carbon particles which means that slagging propensity can be predicted by the common slagging indices. (6) Carbon cycle analysis revealed significant reduction of CO2 when using these biomass feedstock types, particularly the bark types.
Thermodynamic Analysis of Solid Oxide Fuel Cell and Gas Turbine Hybrid System Fueled With Gasified Biomass
Authors: Lv Xiaojing , Geng Xiaoru , Weng Yiwu
Published: November 2014

In this work, the detailed model of a high temperature Solid Oxide Fuel Cell (SOFC) and Gas Turbine (GT) hybrid system was established by using MATLAB/Simulink platform, based on the equations of mass and energy balance and thermodynamic characteristics, with the consideration of various polarization losses and fuel cell heat loss. Influence of different biomass gases on the hybrid system performance was studied. Results show that the electrical efficiency could reach up to over 50% with four types of gasified biomass, higher than other hybrid power system using biomass gases. Biomass gases from different sources have different composition and calorific value, which significantly affect the hybrid system performance. The system output power and efficiency fueled with wood chip gas are higher than the system fueled with other three types of fuel. Restricted by compressor surge safety zone, the adjustable range of biomass gas fuel flow rate is small. The speed of the gas turbine has a significant impact on the hybrid system parameters such as output power and efficiency. When the rotational speed of the gas turbine is lower than the rated value, the hybrid system performance parameters change significantly, on the contrary, the hybrid system performance parameters change slightly.
Emerging Challenges and Design Strategies for SCR Systems
Authors: Czarnecki Larry , Oliveira Paulo
Published: November 2014

Selective Catalytic Reduction has been well demonstrated as an effective technology for reducing NOx emissions from coal-fired utility boilers. Emerging environmental regulations can have an impact on the traditional design and operation of an SCR system.

Increasing demands on SCR emission reduction performance affects the design of many of the SCR components aside from the catalyst bed. Obtaining an optimal distribution of ammonia reagent in the flue gas stream is a primary requirement for high performance levels. This requirement must be balanced with limited space availability, all while obtaining both robust operation and minimal operating costs. Addressing these issues has led to the development of a variety of ammonia injection and distribution methods. Gas mixer designs, such as the IsoSwirl™ mixer, offer a means to obtain high levels of NOx removal while addressing problematic conditions and featuring simple ammonia delivery systems. Ammonia injection methods may utilize either traditional, vapor-phase techniques or the direct injection of an aqueous ammonia supply which avoids ammonia vaporizer requirements.
Modeling of Superheater Operation in a Steam Boiler
Authors: Trojan Marcin , Taler Dawid , Taler Jan , Dzierwa Piotr
Published: November 2014

A numerical method for modeling actual steam superheaters is presented. The finite volume method was used to determine flue gas, tube wall and steam temperature. The numerical technique presented in the paper can especially be used for modeling boiler superheaters with a complex tube arrangement when detail information on the tube wall temperature distribution is needed. The method of modeling the superheater can be used both in the design, performance as well as in upgrading the superheaters. If the steam temperature at the outlet of the superheater is too low or too high, the designed outlet temperature can be achieved by changing a flow arrangement of the superheater. For example, the impact of the change of the counter to parallel flow or to mixed flow can be easily assessed. The presented method of modeling is a useful tool in analyzing the impact of the internal scales or outer ash fouling on the superheater operating conditions. Both ash deposits at the external and scales at the internal surfaces of the tubes contribute to the reduction of the steam temperature at the outlet of the superheater. Furthermore, scale deposits on the inner surface of the tubes cause a significant temperature rise and may lead to the tube damage. The higher temperature of the flue gas over a part of parallel superheater tubes increases the steam temperature and decreases steam mass flow rate through the tubes with excessive heating. This results in an additional increase in the steam temperature at the outlet of the superheater.
Consideration of the Environmental Impact of Wet vs Dry Cooling for Combined Cycle Power Plants
Authors: Howell A. G.
Published: November 2014

Combined cycle power plants fueled with natural gas have been increasingly preferred by regulatory agencies for new power generation projects, compared with traditional coal-fired plants. With growing concerns about water resource availability and the environmental impact of wet cooling systems, there has been an increasing trend for new combined cycle projects to incorporate dry cooling, often as a mandate for regulatory approval of the project. There appears to be little consideration given to the impact of less efficient dry cooling systems on unit efficiency, and particularly on increased fuel requirements and therefore carbon dioxide (CO2) emissions for a given power generating output. The trade-off between reduction of water use and increased fuel requirements with dry cooling should be included as part of the decision on the selection of cooling systems for new fossil plant construction.
Low Emissions, Renewable, Dispatchable Power Generation Using Ethanol/Natural Gas Blends
Authors: Holton Maclain M. , Klassen Michael S. , Eskin Leo D. , Joklik Richard J. , Roby Richard J.
Published: November 2014

Nearly all states now have renewable portfolio standards (RPS) requiring electricity suppliers to produce a certain fraction of their electricity using renewable sources. Many renewable energy technologies have been developed to contribute to RPS requirements, but these technologies lack the advantage of being a dispatchable source which would give a grid operator the ability to quickly augment power output on demand. Gas turbines burning biofuels can meet the need of being dispatchable while using renewable fuels. However, traditional combustion of liquid fuels would not meet the pollution levels of modern dry, low emission (DLE) gas turbines burning natural gas without extensive back-end clean-up. A Lean, Premixed, Prevaporized (LPP) combustion technology has been developed to vaporize liquid ethanol and blend it with natural gas creating a mixture which can be burned in practically any combustion device in place of ordinary natural gas. The LPP technology delivers a clean-burning gas which is able to fuel a gas turbine engine with no alterations made to the combustor hardware. Further, the fraction of ethanol blended in the LPP gas can be quickly modulated to maintain the supplier’s overall renewable quotient to balance fluctuations in power output of less reliable renewable power sources such as wind and solar. The LPP technology has successfully demonstrated over 1,000 hours of dispatchable power generation on a 30 kW Capstone C30 microturbine using vaporized liquid fuels. The full range of fuel mixtures ranging from 100% methane with no ethanol addition to 100% ethanol with no methane addition have been burned in the demonstration engine. Emissions from ethanol/natural gas mixtures have been comparable to baseline natural gas emissions of 3 ppm NOx and 30 ppm CO. Waste heat from the combustor exhaust is recovered in an indirect heat exchanger and is used to vaporize the ethanol as it is blended with natural gas. This design allows for startup on natural gas and blending of vaporized ethanol once the heat exchanger has reached its operating temperature.
Zone Based Control of Building Air Conditioning Systems Through Temperature Monitoring and Control
Authors: Patil Rakesh M. , Keeli Anupama , Shi Di , Sharma Ratnesh
Published: November 2014

In this paper, a zone based temperature monitoring and control system is presented to reduce Air Conditioning (A/C) usage in commercial buildings. Reducing Heating, Ventilation and Air-Conditioning (HVAC) energy usage is a topic of immense interest as HVAC energy consumption represents up to 40% of energy usage in the US and worldwide. Our approach to reducing A/C usage is based on two unique features — extensive monitoring and zone based control. First, multiple temperature sensors are deployed in the building/room of interest to provide an improved temperature picture without the need for a system model. Second, a zone based control approach is developed which is based on flexible definition of zones and results in a generic scalable solution that can be applied to buildings of different sizes and configuration. Our control approach results in efficient A/C operation through extensive monitoring and localized control. In addition, the approach provides redundancy to isolate unforeseen issues such as communication issues to the particular zones. The proposed monitoring and control approach is deployed in telecom base stations and retail stores to highlight the generic nature and scalability of the approach. The energy saving potential and secondary benefits such as flexible localized operation of our unique zone-based control is highlighted in the results. Though the savings vary from 15% to 35% depending on the local conditions and the buildings under consideration our approach is shown to reduce A/C usage in all cases.
Transient Analysis of a High Pressure Seal Injection System Under Startup Conditions
Authors: Washington DeVon A. , Reiss LeRoy N.
Published: November 2014

This study examines the transient behavior of a seal injection system, for four boiler circulating water pumps, in an effort to optimize seal flush rates under startup conditions. During startup, seal injection supply water experiences a large increase in pressure, going from 1.8–26.2 MPa. This large increase in supply pressure presents a challenge in maintaining the desired differential pressure across the seals, and hence the optimum seal flush rate. Overshoot of the control valve position can result in starving the seals of seal water. Delayed responses expose the seals to excessively large differential pressures.

The seal injection system was modeled using PIPENET™ Vision. The model consists of a detailed replica of the seal injection system pipe network. Initial and boundary conditions were obtained from plant DCS data and pump OEM specifications. A baseline model was developed and validated using actual system response data. Extended models considered two types of control systems, manual and differential pressure-control; as well as, control valves with various flow characteristics: linear and equal percentage. Additionally, a diffuser breakdown assembly and startup control valve were also introduced as control components into the model.

Results show that the implantation of a diffuser breakdown assembly in series with the primary control valve (modified linear), in conjunction with automated controls produced a differential pressure of 436 kPa which was within the OEM specified range of differential pressures (345–690 kPa). A startup control valve used in series with the primary control valve also produced acceptable results (388 kPa). The proper design and operation of seal injection systems is vital to extending time between overhauls, thereby reducing maintenance costs. The use of the aforementioned control components in series with control valves is common for boiler feedwater regulation systems during startup; however, this is the first application known to the authors for pump seal injection systems in fossil plants. The results of the hydraulic simulation outlined in this study show this application is viable.
Thermodynamic Evaluation of a Small Wind Turbine
Authors: Gadalla Mohamed , Zafar Sayem , Ahmed Saad
Published: November 2014

A small personal use wind turbine (PWT) is studied and tested for power, exergy and energy evaluation under different operating conditions. The wind turbine incorporates non-twisted blades of 1.5 m span and 0.27 m chord, using NACA 63418 airfoil. Using the earlier test results at pitch angles of 22°, 34° and 38° between the wind speeds of 4 m/s to 7 m/s, torque produced by each blade is determined. It is desired to calculate the torque as it is difficult to measure it for a small wind turbine. Using the governing equations and available computational fluid dynamics software, the total torque on each blade is determined. The resultant torque yielded the mechanical power output of the PWT. Using the available power, energy and exergy in the air flow, corresponding efficiencies are determined. To determine the changes in energy and exergy with respect to the wind speed, wind-chill factor expression is utilized. Results are collected for a wide range of wind speeds and pitch angles. Power, energy, exergy and their corresponding efficiency is evaluated to determine the optimal use pitch angle and ambient conditions. The pitch angles of 22° and 38o yielded high efficiencies although 22° produced the higher rotational speed as compared to 38°. The result suggests better performance for continuous wind speed conditions at low pitch angles — with respect to the rotating plane. For non-continuous wind conditions, higher pitch angles appeared beneficial.
Justification for Long Distance Transmission
Authors: Smith Nathan , Pavlak Alex
Published: November 2014

Wind is always blowing somewhere. From this perspective, a logical hypothesis is that a base load generator might be created by using long distance transmission to connect distant wind farms. This paper tests that hypothesis by putting numbers to it. It is generally accepted that geographic diversity has a smoothing effect on wind fluctuations for cumulative production [1]. This paper addresses the question of whether or not geographic diversity provides system capacity as well. A scenario of interest is the interconnection of wind farms on the East Coast (PJM Interconnection) with wind farms in the Midwest (MISO, the Midcontinent Independent System Operator). Wind is characterized by the Cumulative Distribution Function (DF). Effective Load Carrying Capacity (ELCC) is a metric that defines system capacity, the load that a system can deliver at an acceptable level of reliability. This paper compares standalone wind on PJM with standalone wind on MISO and with standalone wind for interconnected PJM + MISO. A fourth comparison shows the theoretical limit, what could be achieved if wind from PJM and MISO were independent of each other. This analysis quantifies the capacity benefits of long distance transmission.
Investigation on Thermal and Kinetic Characteristics During Co-Pyrolysis of Coal and Lignocellulosic Agricultural Residue
Authors: Wu Zhiqiang , Wang Shuzhong , Zhao Jun , Chen Lin , Meng Haiyu
Published: November 2014

Co-utilization of coal and lignocellulosic biomass has the potential to reduce greenhouse gases emission from energy production. As a fundamental step of typically thermochemical co-utilization (e.g., co-combustion, co-gasification), co-pyrolysis of coal and lignocellulosic biomass has remarkable effect on the conversation of the further step. Thermal behavior and kinetic analysis are prerequisite for predicting co-pyrolysis performance and modeling co-gasification and co-combustion processes. In this paper, co-pyrolysis behavior of a Chinese bituminous coal blended with lignocellulosic agricultural residue (wheat straw collected from north of China) and model compound (cellulose) were explored via thermogravimetric analyzer. Bituminous coal and lignocellulosic agricultural residue were heated from ambient temperature to 900 °C under different heating rates (10, 20, 40 °C·min−1) with various mass mixing ratios (coal/lignocellulosic agricultural residue ratios of 100, 75/25, 50/50, 25/75 and 0). Activation energy were calculate via iso-conversional method (eg. Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Starink methods). The results indicated that pyrolysis rate of coal was accelerated by wheat straw under all mixing conditions. Cellulose promoted the pyrolysis rate of coal under equal or lesser than 50% mass ratio. Some signs about positive or passive synergistic effect were found in char yield. Char yields were lower than that calculated from individual samples for bituminous coal and wheat straw. With the increasing of cellulose mass ratio, the positive synergies on char yields were reduced, resulting in passive synergistic effect especially under higher coal/cellulose mass ratio (25/75). Nonlinearity performance was observed from the distribution of activation energy.
Performance Corrections for Steam Turbines With Multi-Pressure Condensers
Authors: Winterberger Thomas P. , Tzagkarakis Ioannis
Published: November 2014

An accurate correction methodology is essential when analyzing test data and trending performance. One of the most critical parameters for steam turbines, which can result in large corrections, is condenser back-pressure or exhaust pressure.

Many large fossil and all nuclear steam turbines are configured with either two or three low pressure condensing exhaust hoods. All exhaust hoods may not operate with the same condenser pressure. Factors affecting condenser pressures between hoods could include the cooling water arrangement, uneven fouling, tube plugging, air removal effectiveness, etc. The biggest impact is likely due to the cooling water arrangement. In a parallel arrangement, the condenser cooling water splits between the shells with each shell receiving an equal amount of flow at the same inlet temperature. In a series arrangement, all cooling water enters and exits the first shell before entering the next shell. In this arrangement the cooling water temperature entering the second shell is higher than the temperature entering the first shell resulting in the condensers operating at different exhaust pressures.

One common practice is to apply a single exhaust pressure correction factor based on the average exhaust pressure of all condenser shells. In cases where the differences in condenser pressure are small, this practice can provide accurate corrected turbine performance. As the difference in condenser pressures increases, the potential for introducing error in the corrected performance results also increases.

This paper will discuss the mechanism of why multi-pressure operation can result in correction errors if not modelled correctly and will also quantify the potential impact of these errors on the corrected performance results. In addition, guidance will be given on how exhaust pressure correction curves should be created and applied to most accurately model the performance of the turbine cycle when multi-pressure operation exists.
Development of Power Generation Reliability Availability and Maintainability (RAM) Programs
Authors: August J. K. , Wodka Brian
Published: November 2014

Ideal plant designs perform as intended. The goal of Reliability, Availability and Maintainability (RAM) processes is to convert designs into operational task requirements to achieve lifecycle goals. This paper discusses developing Power Generation RAM programs. Given the performance-based nature of ASME RAM standards, different approaches can be used to achieve its goals.

Improved operations and maintenance (O&M) programs offer to manage risk at lower cost. This paper introduces a risk management process to develop, maintain and use better risk-based failure management plans with an approach that is simple and clear. It predicts that software will become a more important RAM program development tool.
Shell and Plate Feedwater Heater Prototype Test
Authors: Taylor Creed , John Rhorn , Williams Jason L.
Published: November 2014

Westinghouse Electric Company and Tranter Inc. are collaborating to develop the modular, low-pressure horizontal shell and plate feedwater heater (SPFWH™) heat exchanger product. This design utilizes easily removable modules of welded heat transfer plates within a pressure vessel instead of traditional tubes as the pressure boundary and heat transfer interface between the steam and feedwater. Design advantages include improved long-term performance, inspection and maintenance access. Each SPFWH™ heat exchanger will be designed to meet all plant-specific requirements and is ASME Section VIII compliant.

A prototype SPFWH™ heat exchanger design (herein called the prototype or test unit) was fabricated and tested to validate the functionality of the design features and benchmark the correlations used to predict the performance. The test was performed in the Tranter Inc. laboratory facility using full temperature and pressure steam conditions over a broad operating range typical of low pressure feedwater heaters.

Heat transfer coefficient characteristics have been evaluated and the prototype test data shows good agreement with established empirical correlations and other industry research. These results indicate that the SPFWH™ heat exchanger design is a viable alternative to a shell-and-tube type heat exchanger due to the performance, compactness, modularity, and robustness of the new design.
CFD Simulations of Heat Recovery Steam Generators Including Tube Banks
Authors: Galindo-García Iván F. , Vázquez-Barragán Ana K. , Rossano-Román Miguel
Published: November 2014

CFD (Computational Fluids Dynamics) simulations of HRSGs (Heat Recovery Steam Generators) can improve and optimize the performance of combined cycle power plants. For example CFD results can help to analyze the effect that different working conditions such as changes in power or fuel quality can have on the uniformity of the flow. A uniform flow is important because the tubes inside the HRSG are more susceptible to corrosion and rupture when the flow distribution is strongly nonuniform. An accurate modeling of the flow and heat transfer characteristics is paramount in order to obtain a realistic representation of the process. However, a big problem in CFD modeling of HRSGs, or any equipment with tube-and-shell heat exchangers, is the different length scales of the equipment, which vary from a few centimeters for the tubes diameter to tens of meters for the HRSG vertical height. The problem is that these different length scales would require a very large computational mesh and consequently a very expensive simulation. To overcome this problem, a common approach in CFD simulations of HRSG has been to model the tube banks following a porous media approach, where the tubes are represented by a volume with a porosity factor which gives the volume fraction of fluid within the porous region. Using this model a pressure drop and the total heat absorbed due to the presence of the solid tubes is calculated. However, due to the recent advances and relatively lower prices of computer equipment it is now possible in a relatively economical way to explicitly include the tube banks in the CFD models of HRSGs. In this study a CFD model of a HRSG is presented where the tube banks are included in the geometric model. Results using this model show the fluid flow and heat transfer between the numerous tubes. A further advantage, in contrast to the porous media model, is that the flow inside the tubes is also modeled which gives a more realistic representation of the phenomena inside the tubes.
Improving Nuclear Plant Reliability by Developing an Eddy Current Test Strategy to Identify Uncommon Condenser Tube Defects
Authors: Kocher James A. , Frazee Robert , Wolf Matthew
Published: November 2014

Eddy Current Testing (ECT) of condenser tubes is essential to maintaining good plant reliability and availability. Early identification of defects can allow for adequate remedial action and prevent forced outages caused by condenser tube leaks. The well-known catastrophic failure in the nuclear industry in Japan has not only raised concern in Japan over aging nuclear power plants, but has also raised concern over safe operations in the United States and around the world. Ongoing reliability and instability issues due to reported leaks in condensers have also been the topic for nuclear watchdogs. This focus on the nuclear plant condenser has brought to light the various levels of sophistication and capability in ECT.

In ECT, the type of defect present in a condenser tube is determined by the characteristics it presents under test. The tubes must be adequately cleaned prior to testing and some awareness or evidence of the type of defect to be uncovered should be available to the testing team. In cases where defects are discovered that are inconsistent with prior awareness further exploratory testing is common. Exploratory testing can proceed to test areas of suspected defects in the tubing, and it may result in a complete redefinition of the test procedure, inclusive of instruments, probe types and other key ECT criteria. A comprehensive knowledge of testing options and their practical application is necessary to redefine a test that will yield meaningful results and achieve the intended objective; to identify the type and extent of defect and take remedial action therefore preventing failure.

This paper addresses such a case at the South Texas Project (STP) Nuclear Power Plant where peculiar defects were undeterminable under standard ECT procedures. The defects continued to negatively impact reliability and stability at the plant until a new ECT process and test procedure were developed, demonstrated and deployed. The result achieved was accurate defect detectability and improved nuclear plant reliability.
Testing the Limits of PTC 46
Authors: Le Galudec Olivier
Published: November 2014

PTC46 — currently under revision — is now a well known Code used worldwide in the field of overall Plant testing, and methodology proved effective in a majority of cases. However, there are occasional situations where strict and direct application of the codes does not work and unconventional solution needs to be found. Author shows how nevertheless the principles set in the code allow to select a solution so that Performance test may be conducted through two examples.
Flaw Acceptance Rule of J-Groove Weld of Bottom Mounted Instrumentation Nozzle
Authors: Hojo Kiminobu , Nagoshi Yasuto , Ochi Mayumi , Miura Naoki , Kamaya Masayuki , Sera Takehiko
Published: November 2014

The rules on fitness for service for nuclear power plants of JSME are applied for flaw evaluation after detecting defects in the operating nuclear plants in Japan. The rules mainly focus on simple geometry such as straight pipes or vessels and do not provide the evaluation procedure for complex structures. The authors made a draft of flaw acceptance rule for J-groove weld of a bottom mounted instrumentation nozzle at application of the cap repair. The rule contains flaw modeling, fatigue and SCC crack growth calculation and flaw instability assessment. After detecting a defect on a J-groove weld, a flaw will be modeled in the whole of J-groove weld region because of fast SCC crack propagation in the weld region. Due to complex configuration of the evaluation location, FE analysis is needed for obtaining stress intensity factors (Ks) to calculate the crack growth and flaw instability. The proposed rule has a guidance for K calculation by FE analysis with the aim of decreasing dependence of individuals for calculation. The authors performed benchmark analyses to confirm the guidance applicability. The calculation results by three participants agreed within several percent.
Moisture Adsorption Considerations for Packaging Plutonium Oxide
Authors: Laurinat James E. , Hensel Steve J.
Published: November 2014

Compliance with DOE-STD-3013, Stabilization, Packaging, and Storage of Plutonium-Bearing Materials, requires plutonium oxide to be stabilized at high temperatures such that the material is non-reactive and has less than 0.5% wt. moisture adsorption [1]. Since plutonium oxide is known to readily adsorb moisture, compliance with the standard requires a sample of oxide material to be measured for moisture adsorption. The measurement is typically performed using thermogravimetric analysis (TGA). The sample must be representative of the actual oxide material in order for the TGA measurement to be valid. Obtaining a representative sample from an oxide powder container may be done using a core sampler or a grab sample method that accounts for potential spatial distribution of the oxides. A further complication with moisture sampling is that the plutonium oxide typically continues to adsorb moisture from the glove box ambient air for many hours or even days until equilibrium is reached. In typical oxide material handling operations, the material, both product and sample, is canned and bagged out prior to reaching a moisture level in equilibrium with the ambient relative humidity. In fact, given the strict moisture requirement for DOE-STD-3013 compliance, it is highly undesirable to allow for equilibrium moisture adsorption to be achieved. Given the dynamic nature of moisture adsorption, a technical basis for obtaining a representative sample is important for DOE-STD-3013 compliance. The technical basis not only includes how the sample is obtained, but more importantly, must account for all handling once the sample is physically separated from the product. This paper provides an analytical basis for moisture adsorption to define handling controls that assures a representative oxide sample is obtained.
Challenges and Opportunities for Structural Health Monitoring in PVP Applications
Authors: Giurgiutiu Victor
Published: November 2014

This paper discusses the challenges and opportunities of using structural health monitoring (SHM) concepts and technologies in pressure vessels and piping (PVP) applications. The research into monitoring of structural health has experienced a dramatic increase in the last decade due to at least two factors. On the one hand, our industrial installations, aircraft fleets, civil infrastructure, etc. are becoming increasingly aged and require more and more maintenance costly actions and repairs. This process could be greatly improved if scheduled maintenance were augmented or even replaced by continuous monitoring that would limit costly inspections and maintenance actions to being done only when needed; and (b) the advent of advanced technologies, e.g., active materials based sensors, actuators, and transducers as well as advanced data acquisition, data processing, and data mining technologies that enable the practical implementation of the SHM concepts.

To date, the SHM research has been mainly performed for the aerospace, defense, and civil infrastructure applications and some interesting proof-of-concept results have been demonstrated. Very little research, if at all, has been done on using the SHM concepts in PVP applications. The reason for this situation may be that PVP applications may be more challenging than the other applications in which SHM concepts have been tried so far. The present paper explores this topic and highlight (a) the challenges that have to be overcome in order to develop SHM for PVP applications; and (b) the opportunities that exist for using SHM in PVP applications. The paper starts with a review of the main SHM concepts and technologies. Then, the paper identifies the challenges that would exist if these SHM concepts and technologies were to be applied the PVP applications. Finally, the paper discusses the opportunities for applying SHM to PVP applications forward. The paper ends with conclusions and suggestions for further work.
Real-Time Hybrid Simulation of Viscous Dampers for Seismic Hazard Mitigation
Authors: Chen Cheng , Valdovinos Jose , Pong Wenshen
Published: November 2014

Laboratory experiments play a critical role in earthquake engineering research for seismic safety evaluation of civil engineering structures. Real-time hybrid simulation provides a viable alternative for shake table testing to evaluate seismic performances of structures with rate-dependent seismic devices. Servo-hydraulic actuators play a vital role in a real-time hybrid simulation to maintain the boundary condition between the analytical and experimental substructures. Compensation of actuator delay is critical to minimize synchronization error from actuator delay and to achieve a successful real-time hybrid simulation. Research on how actuator delay can affect the real-time hybrid simulation involving viscous fluid damper is presented in this study. It is demonstrated that although the viscous fluid damper can help stabilize the real-time hybrid simulation with actuator delay, the experimental results need to be interpreted appropriately to evaluate the performance of viscous fluid damper for seismic hazard mitigation.
Crack Initiation and Propagation Clad Pipe Girth Weld Flaws
Authors: Carlucci Antonio , Bonora Nicola , Ruggiero Andrew , Iannitti Gianluca , Testa Gabriel
Published: November 2014

At present, design standards and prescriptions do not provide specific design routes to perform engineering criticality assessment (ECA) of bimetallic girth welds. Although the authors has shown the possibility to implement ECA in accordance with available prescriptions of such flawed weld joint following the equivalent material method (EMM), when dealing with ductile crack initiation and propagation — as a result of the large scale yielding occurring at the crack tip for high fracture toughness material operating in the brittle-ductile transition region — fracture mechanics concepts such as JIc or critical CTOD may breakdown. In this work, the possibility to accurately determine the condition for ductile crack growth initiation and propagation in bi-metallic girth weld flaws using continuum damage mechanics is shown. Here, the base metal as well as the clad and the weld metal have been characterized to determine damage model parameters. Successively, the geometry transferability of model parameters has been validated. Finally, the model has been used to predict crack initiation for two bi-material interface circumferential crack configurations.
Modeling and Simulation of Creep Crack Growth in High Chromium Steels
Authors: Bonora Nicola , Esposito Luca , Dichiaro Simone , Folgarait Paolo
Published: November 2014

Safe and accurate methods to predict creep crack growth (CCG) are required in order to assess the reliability of power generation plants components. With advances in finite element (FE) methods, more complex models incorporating damage can be applied in the study of CCG where simple analytical solutions or approximate methods are no longer applicable. The possibility to accurately simulate CCG depends not only on the damage formulation but also on the creep model since stress relaxation, occurring in the near tip region, controls the resulting creep rate and, therefore, crack initiation and growth. In this perspective, primary and tertiary creep regimes, usually neglected in simplified creep models, plays a relevant role and need to be taken into account. In this paper, an advanced multiaxial creep model [1], which incorporates damage effects, has been used to predict CCG in P91 high chromium steel. The model parameters have been determined based on uniaxial and multiaxial (round notched bar) creep data over a wide range of stress and temperature. Successively, the creep crack growth in standard compact tension sample was predicted and compared with available experimental data.
Effect of Joint Thickness on Residual Stress in Laser / Electron Beam Welded 9Cr-1Mo(V, Nb) Ferritic / Martensitic Steel
Authors: Kumar Santosh , Bouchard Peter J. , Dey Gautam K.
Published: November 2014

Residual stresses are invariably associated with welded joints because of local dilation/contraction of material against itself as well as clamp-imposed restraints. Plate thickness provides considerable self-restraint in the case of heavy section welded joints produced by laser and electron beam welding processes and therefore, is expected to affect the relative magnitudes of the three orthogonal direct components of residual stress — longitudinal, normal and transverse to the welding direction. Computation of residual stress in high energy beam welded 9Cr-1Mo(V, Nb) steel plates, of varying thickness in the 5 mm to 80 mm range, has been carried out using finite element based software, SYSWELD, for a systematic study of the effect of the joint thickness on the relative magnitude of the three orthogonal components of stress. The results show that the distributions of residual stress components can be ranked in order of significance in the order: longitudinal, normal and then transverse. The longitudinal and the normal components of stress show similar cross-weld profiles. The magnitude of the normal component peak shows a direct correlation with the joint thickness and eventually exceeds that of the longitudinal component for an 80 mm thick joint. The results are discussed in the context of our previous residual stress measurements made by neutron diffraction on a thin section laser welded 9Cr-1Mo(V, Nb) steel plate.
Weld Residual Stress Inputs for a Probabilistic Fracture Mechanics Code
Authors: Benson Michael L. , Brust Frederick W. , Kurth Robert E. , Broussard John E.
Published: November 2014

Weld residual stress (WRS) is known to be an important driver for stress corrosion cracking. Therefore, in probabilistic Leak-Before-Break calculations for safety-related nuclear piping systems, it is necessary to offer best-estimate WRS inputs along with an informed characterization of the associated uncertainty. This paper discusses the finite element (FE) analysis work performed to develop the WRS inputs for probabilistic models used for dissimilar metal (DM) welds at pressurized water reactors (PWRs). Three different weld geometry cases were considered representing typical nuclear piping system DM welds. In accounting for modeling uncertainty, the FE results from three independent analysts for the various weld geometry cases were compared and evaluated. This paper describes the modeling strategies used to develop the best-estimate inputs and the uncertainty distributions, including approaches to eliminate unnecessary sources of uncertainty, such as inconsistent post processing.
The Advantage of Using a File Data Transfer Method in a Plant Design
Authors: Fung Michael , Fung Andy , Fung Richard H. , Fung P. K.
Published: November 2014

In general, there are two methods to pass on design information in a petrochemical plant design: the manual data key-in method and the file data transfer method. The manual data key-in method is a basic method to pass on data; but this method is time consuming to assign data in one by one fashion. The file data transfer method is a mapping file data from one program to another program under certain specific function and criteria.

This paper starts with how to use a file data transfer method to create a stress analysis model, and then proposes an approach to transfer the stress analysis result to a structural analysis program by using the Pipe Loadings Transfer Program.

In a piping design using 3D plant design software for modeling, the piping design information can be directly transferred to the stress input file by using point vectors to create a stress analysis model. The concepts of a pipe support vector and a beam vector were introduced to transfer the pipe loadings from stress analysis results to a structural analysis program.

The advantages of using a file data transfer method are simple, fast, and accurate.
Possible Improvements in Multiple Areas of API RP 581
Authors: Szidarovszky Miklós A. , Thomas Samuel M.
Published: November 2014

API RP 581 gives detailed steps and data to help perform quantitative analyses for “Risk Based Inspection” of pressurized equipment. This includes probability of failure, consequence of failure and risk assessment. Unfortunately, the use of API RP 581 in its current form can sometimes lead to incorrect estimations of both probability and consequence of failure, leading to an incorrect risk assessment of the components/equipment being analyzed.

In this paper, we will highlight some of the issues that we ran across while performing an RBI analysis following the steps and methods prescribed in API RP 581, involving a level 1 consequence analysis, and suggest possible changes for future editions to remove/minimize the consequences of these issues.
A Weibull Stress Approach Incorporating the Coupling Effect of Constraint and Plastic Strain in Cleavage Fracture Toughness Predictions
Authors: Ruggieri Claudio , Dodds Robert H.
Published: November 2014

This work describes a micromechanics methodology based upon a local failure criterion incorporating the strong effects of plastic strain on cleavage fracture coupled with statistics of microcracks. A central objective is to gain some understanding on the role of plastic strain on cleavage fracture by means of a probabilistic fracture parameter and how it contributes to the cleavage failure probability. A parameter analysis is conducted to assess the general effects of plastic strain on fracture toughness correlations for conventional SE(B) specimens with varying crack size over specimen width ratios. Another objetive is to evaluate the effectiveness of the modified Weibull stress (σ̃w) model to correct effects of constraint loss in PCVN specimens which serve to determine the indexing temperature, T0, based on the Master Curve methodology. Fracture toughness testing conducted on an A285 Grade C pressure vessel steel provides the cleavage fracture resistance (Jc) data needed to estimate T0. Very detailed non-linear finite element analyses for 3-D models of plane-sided SE(B) and PCVN specimens provide the evolution of near-tip stress field with increased macroscopic load (in terms of the J-integral) to define the relationship between σ̃w and J. For the tested material, the Weibull stress methodology yields estimates for the reference temperature, T0, from small fracture specimens which are in good agreement with the corresponding estimates derived from testing of much larger crack configurations.
Understanding Welding Cost: Using Flux-Cored Arc Welding (FCAW) for Cost Reduction and Productivity Improvement
Authors: Patrick Charles W. , Newell William F.
Published: November 2014

Welding is often listed as a production operation that companies would like to reduce overall cost and improve productivity; however, most companies merely implement cost reduction programs focused on lowering welding consumable costs. Though significant and important, these associated material costs typically represent only a small percentage to the total cost, i.e., 10 to 20% (welding consumables 8 to 15% and power and equipment 2 to 5%) of the overall welding cost in a typical U.S. welding operation. To further reduce welding costs, companies need to look further. Since labor and overhead, which relates directly to productivity, represents approximately 80 to 85% of the overall cost of any given welding operation they also offer the greatest opportunities for significant cost reduction. Simply changing from Shielded Metal-Arc Welding (SMAW) to Flux-Cored Arc Welding (FCAW) can reduce labor cost and increase productivity. Due to the increased deposition efficiency and operating factor of FCAW the weld deposition rate increases thus translating into increased productivity. The increase in productivity, in turn, reduces labor cost by reducing the man-hours required for the completion of any given weld. An added benefit gained by using FCAW is that it also significantly reduces the skill level required by the welder to produce welds of equal quality. When all of these benefits are combined FCAW yields significant cost savings opportunities by reducing labor and simultaneously improving productivity.
Ductile Crack Propagation Simulation of a Cylinder With a Through-Wall Circumferential Flaw Under Excessive Cyclic Torsion Loading
Authors: Hojo Kiminobu , Watanabe Daigo , Kawabata Shinichi , Ametani Yasufumi
Published: November 2014

A lot of applications of elastic plastic FE analysis to flawed structural fracture behaviors of mode I have been investigated. On the other hand the analysis method has not been established for the case of the excessive cyclic torsion loading with mode II or III fracture. The authors tried simulating the fracture behavior of a cylinder-shaped specimen with a through-walled circumferential flaw subjected to excessive monotonic or cyclic loading by using elastic plastic FE analysis. Chaboche constitutive equation of the used FE code Abaqus was applied to estimate the elastic plastic cyclic behavior. As a result in the case of monotonic loading without crack extension, the relation of torque-rotation angle of the experiment was estimated well by the simulation. Also J-integral by the Abaqus’ function agreed with a simplified J-equation using the calculated torque-rotation angle relation. On the other hand under load controlled cyclic loading associated with ductile crack growth, the calculated torque-rotation angle relation did not agree with the experimental one because of high sensitivity of the used stress-strain curve. J-integral from Abaqus code did not increase regardless of the accumulated crack growth and plastic zone. Several simplified ΔJ calculations tried to explain the experimental ductile crack growth and it seemed that da/dN-ΔJ relation follows the Paris’ law. From these examinations an estimation procedure of the structures under excessive cyclic loading was proposed.
Valve Packing Research and Development Equipment
Authors: Veiga José C. C. , da Silva Gustavo M. , Barroso Carlos D. B. Girão , Baulch Joel
Published: November 2014

To assure a leak free scenario when a valve packing is utilized, tests have been developed in order to monitor a group of parameters when service conditions are simulated. These tests enable valve manufactures to have an improved design, and guide end users on efficient packing selection. This paper presents valve packing test devices that provide developers with tools to evaluate properties such as; installation stress, relaxation, stem torque, number of rings and thermal expansion effects. Details of each device are shown, along with typical results of each property evaluated.