bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Improvements of Nuclear Power Plants by the Application of Longer LP Last Stage Blades and Advanced Design Techniques
Authors: Jones Mike , Crossland Robert 
Published: November 2014

Over the last decade, the Author’s company (Alstom Power) has retrofitted the steam turbines in 34 nuclear units on a diverse range of half and full-speed machines, powered by Pressurised and Boiling Water Reactors. Some of those projects have been described in other papers, with an explanation of the novel laser measurement and fast-track installation techniques that have been developed to meet the onerous demands of nuclear plants and authorities.
The ageing global nuclear fleet has suffered reduced levels of reliability and performance due to effects such as Stress Corrosion Cracking (SCC), moisture erosion and shaft line torsional faults. Alstom has developed a range of steam turbine retrofit solutions that are resistant to SCC and erosion, have extended maintenance intervals and deliver high levels of efficiency. A portfolio of rear stage blades is available, from which an optimum design can be selected to suit each project.
This paper focuses on the improvements in thermal performance and reliability of a number of recent nuclear steam turbine retrofits. It outlines the existing designs and some of the challenges faced by the plants concerning reliability, operation and efficiency and then describes the approach to addressing those issues by retrofitting with modern designs. The paper describes the blading design and the techniques which are used to evaluate exhaust performance. It will also show the methods which have been used to integrate longer Last Stage Blades into existing LP frames.
The paper concludes by presenting the experience, in terms of performance and installation, of some of the projects.
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.
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.
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.
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.
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”.
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.