bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of an Eddy Current Inspection of Brass Tubes in a Surface Condenser to Provide a Condition Assessment
Authors: Gowatski Shawn , Mitchell Tim
Published: July 2009

A Borelex, Inc. Power Plant in Ashland, Maine had a need to evaluate their Surface Condenser. The unit had 27 tubes that were previously plugged. The unit had steam impingement troubles in the past and the plant wanted to focus the inspection in this area. The condenser contains 6,084 tubes that are 7/8″ OD, 0.049″ wall, 303″ long, admiralty brass. The plant decided to use the Eddy Current Technique (ECT) to inspect 600 tubes. The condenser uses local river water. TesTex told the plant the unit could be inspected and a color-coded tube sheet map showing the results could be completed in one shift. The contractor arrived at the plant at 7 am. The crew went through the usual plant indoctrination and safety training. Testing on the condenser using an Air-Assist System, the contractor was able to inspect the 600 tubes, perform analysis, and present a color-coded tube sheet map by 5 pm. A total of nine tubes showed wall thinning greater than 60%, which were recommended for plugging. The preliminary report provided listed the flaw locations and whether the defects were located on the I.D. or O.D. of the tube. In addition to this inspection, the plant also performed a hydro-pressure test to find any additional tube leaks. A few more tube leaks were found in areas that were not inspected with eddy current. These leaks along with the 9 tubes recommended for plugging were plugged. Prior to this inspection the plant felt the issues with the condenser were leaks in the joint between the tube and the tubesheet, where the tube has been rolled. The inspection showed the most severe wall losses found were on the O.D. of the tubes at various locations along the length of the tube. The tubes with wall losses less than 60% showed I.D. thinning at various places along the length of the tube. The effects of the tube plugging were that the water chemistry is better than ever and the vacuum pressure is higher than before.
The Case for Combining Pump Maintenance and Systematic Upgrading
Authors: Bloch Heinz P. , Bluse Robert , Steiger James
Published: July 2009

Virtually, all industrial machinery requires periodic maintenance for dependable long-term operation. In fact, the very term “maintenance” is defined as keeping machines in the as-designed or as-purchased and manufactured condition. At issue is whether the equipment owner’s profitability objectives are best served by “maintaining only”, or by judiciously combining maintenance and upgrading tasks. Assuming the answer favors combining maintenance and upgrading, the question arises whether an intelligent and well thought-out combination of maintenance and upgrading should be entrusted only to the original equipment manufacturer (OEM), or if qualified non-OEMs should be considered also. The co-authors would like to offer their answer to the question. Experience shows that a highly qualified independent rebuild shop with demonstrated capabilities and experienced personnel can offer high-quality upgrades that improve both uptime and efficiency. Such a shop can do so consistent with current system performance requirements. With the considerable consolidations in the pump industry, the distinct possibility exists that the OEM is not able to offer the same engineering competence he previously had and that independent shops should be considered. This presentation deals with a case study and details where such upgrading was being planned, implemented, and verified to have had the desired results. It further explains the role played by competent pump rebuild shops (we chose to call them “CPRS”) in these important endeavors. Our work supports the premise that rebuilding a vintage process pump to original OEM specifications makes no sense, given current pump rebuilding technology and changes to the system performance that occur over time. We find compelling reasons to systematically upgrade the efficiency and potential run length of large centrifugal pumps. Of course, this upgrading must be pre-planned and then carried out during a future maintenance outage.
Is Your Power Plant Headed for a HILP? How to Avoid, Detect or Mitigate High Impact–Low Probability (HILP) Events
Authors: Richwine Robert R. , Stallard G. Scott , Curley G. Michael
Published: July 2009

In recent years some power companies have instituted programs aimed at reducing or eliminating their power plants’ unreliability caused by abnormal events that occur infrequently but result in extended unplanned outages when they do occur, i.e. High Impact–Low Probability events (HILPs). HILPs include catastrophic events such as turbine water induction, boiler explosions, generator winding failures, etc. Many of these successful programs have relied on the detailed reliability data contained in the North American Electric Reliability Corporation’s (NERC) Generating Availability Data System (GADS) that contains data collected over the past 25 years from 5000+ generating units in North America. Using this data, these companies have been able to 1) benchmark their fleet’s unreliability due to HILPs against their North American peers, 2) prioritize their peer group’s susceptibility to various HILP modes and 3) use root cause data contained within the NERC-GADS data base to help identify and evaluate ways to proactively prevent, detect and/or mitigate the consequences of HILP events. This paper will describe the methods used in these successful programs in sufficient detail to enable others to adopt the techniques for application at their own generating plants.
Degradation in Turbo Machinery
Authors: Westcott John C. , Penna Lawrence A.
Published: July 2009

Gas turbines and steam turbines start to degrade in performance when they first start running. This paper lists the causes of degradation, describes how to monitor degradation, and suggests techniques for minimizing degradation. This paper also suggests how degradation can be handled in contract language for acceptance testing. Lastly, this paper explores a special case, often misunderstood, namely how boiler operation needs to be accounted for when evaluating the effect of degradation (the loss factor) of an HP turbine in a reheat cycle.
A Case Study of Retrofitting a Demonstration Solar Energy Building
Authors: Gong Xiangyang , Kulkarni Manohar , Claridge David E.
Published: July 2009

Hydronic solar systems with copper tube collectors or vacuum glass tube collectors are commonly used thermal-solar systems. These systems run well in residential buildings or in small scales for domestic water heating. These systems can be scaled up and applied to commercial buildings. The solar energy collected by these systems can be used to drive absorption chillers in summer and heat the feed water for boiler in winter. Properly designed and installed systems can save energy by utilizing free solar energy. However, operation and maintenance do have an important impact on whether these systems truly save energy. This paper presents a technical review of a large scale hydronic solar system installed in Carbondale, Illinois and compares this system with a photovoltaic system which was proposed to retrofit the hydronic solar system in energy conversion efficiency, system components, initial cost, operation and maintenance etc.
Aging Pipe Supports: A Photographic Study
Authors: Kimball Lange E.
Published: July 2009

Pipe supports were originally intended to be low or no maintenance items. Consequently, pipe supports had become low priority items for the plant’s attention. However, as plants operate well beyond their original design life or are situated in locations that are corrosive, plants are becoming more aware that some pipe support maintenance must be expended. Short comings in the application, material, design, etc. of pipe supports are becoming more and more apparent as plants age. The effect is to impose unintended stress and loading into the equipment and piping that ultimately can become a safety or reliability issue. This is a photographic essay intended to provide graphic evidence of the types of problems that plants face with their aging pipe supports. The intention is to reenforce the need for plants to institute and maintain pipe hanger assessments as part of the total plant reliability effort.
Sensitivity Analysis and Control of Gasifier Using Recycled Carbon Dioxide Gas in Integrated Gasification Combined Cycle
Authors: Chapalamadugu Vishnu , Ydstie B. Erik
Published: July 2009

Integrated Gasification Combined Cycle (IGCC) is rapidly emerging as one of the most promising technologies in power generation and is able to meet the most stringent emissions requirements. The IGCC systems are extremely clean and much more efficient than traditional coal fired power systems. The gasifier is the heart and most complicated unit operation with high temperatures and pressure variations in the Integrated Gasification Combined Cycle (IGCC). The dynamics inside a gasifier is very rapid and it is extremely complicated to control the high temperatures inside the gasifier and the synthesis gas (H2 + CO) composition coming out of the gasifier. This paper describes a novel technique that has been developed for varying and controlling the synthesis gas compositions coming out of the gasifier and temperature inside the gasifier by carbon dioxide gas recycle to the gasifier. In order to vary the synthesis gas composition, the gasifier temperature and other key parameters, the carbon dioxide recycle gas to the gasifier is manipulated instead of varying the coal, water and oxygen mass flow rates. A sensitivity analysis on the gasifier has been completed by varying the mass flow rate of carbon dioxide recycle gas and the oxygen gas without varying the coal slurry (coal +water) mass flow rate to analyze the synthesis gas composition, temperature, char conversion and other important parameters. Using the sensitivity analysis it has been showing that enhanced controllability of the gasifier in the IGCC is possible to meet the varying demands by recycling CO2 without the need of varying the coal, water and oxygen flow rates. The method is based on the idea that different output compositions can be achieved by making the carbon in coal slurry react with as an oxidizer instead of O2 with the help of Boudouard reaction (CO2 + C → 2CO). The two-stage oxygen blown entrained flow gasifier has been modeled using Computational Fluid Dynamics (CFD) and the coal gasification process was modeled using the Discrete Phase Method implemented in the Finite Volume FLUENT® CFD software. The physical and chemical processing of the coal slurry gasification is implemented by using FLUENT® User Defined Function’s (UDF’S). These UDF’s define the mechanism through which thecoal partiticles undergo moisture release, vaporization devolatilization, char oxidation and gasification processes. One important property of the gasifier in the Integrated Gasification Combined Cycle (IGCC) is that it can simultaneously produce synthesis gas for chemical processes as well as electricity, how much is generated of each can be balanced according to market demand.
Analysis and Optimization of an Ammonia Based Transcritical Rankine Cycle for Power Generation
Authors: Sarkar Jahar , Bhattacharyya Souvik
Published: July 2009

This study presents the potential of ammonia as a working fluid in transcritical Rankine cycle for power generation using both high and low temperature heat sources. Higher heat capacity value and superior heat transfer properties of ammonia compared to water are the motivating factors behind its use as a working fluid. A thermodynamic analysis for the ammonia based transcritical Rankine cycle and its comparison with the water based Rankine cycle is presented. Analyses with several cycle modifications are also presented to study the thermal efficiency augmentation. It is observed that an optimum high side pressure exists for near critical operation. In case of low temperature heat sources such as solar energy or waste heat, where water based systems are not suitable, ammonia based Rankine cycle is applicable with attractive thermal efficiency, although cycle modification is not possible. The results with high temperature heat source such as boiler or nuclear reactor, where the turbine outlet is in superheated zone, show that simple ammonia systems yield lower efficiency than water, although a recompression cycle with regenerative heat exchangers exhibits higher efficiency than water. Significant thermal efficiency improvement can be achieved by increasing the high side cycle pressure. Recompression Rankine cycle can be a potential alternative with proper design measures taken to avoid toxicity and flammability.
A Study of Steam Turbine Droplet Formation, Shedding and Blade Impact
Authors: Vakili Ahmad D. , Meganathan Abraham J. , Golden Gary
Published: July 2009

Blade erosion is a serious problem in steam turbines and reduces the life of turbine, requiring periodic maintenance. A fundamental experiment is being performed to evaluate effects of certain control parameters on the droplet formation process and distribution of the shed droplets sizes. Three blade coatings include Epoxy, Teflon®, Viton®, three trailing edge geometries and a new and innovative trailing edge effect are to be experimentally studied. Measurements are to be made in a simulated stationary cascade utilizing real turbine components. The condensed liquid film and the large droplets formed on the three coated blades and one original finish blade will be optically measured. A typical cascade is modeled using Volume of Fluid with different surface properties used to model the formation and breakup of a thin water layer into droplets. Droplet distributions for the various conditions will be compared and the best surface finish and configurations will be identified. Most importantly, the reason for a successful configuration will be given, based on the measurement results.
A Model for Analysis of Integrated Gasification Combined Cycle Power Plant With Carbon Dioxide Capture
Authors: Pei Peng , Kulkarni Manohar
Published: July 2009

Integrated Gasification Combined Cycle (IGCC) is believed to be one of the most promising technologies to offer electricity and other de-carbon fuels with carbon capture requirement at a relatively low cost. With the process of carbon dioxide capture, it can also actually meet strict regulations for other pollutants emission. However, the performances can vary depending on what kinds of technologies or processes are used. This paper has developed a model and calculated by using Engineering Equation Solver (EES) program to determine and compare different available technologies and processes. There are four main components in the model: Gasification Island; Gas Cleanup Island; Carbon Dioxide Capture Island and Power Island. Among them, the different options of Gasification Island; and Carbon Dioxide Capture Island are expected to be the most effective factors to influence the performance of the plant. Therefore, different gasification processes are examined in this paper, including Shell, GE (Texaco) and Lurgi. The carbon dioxide capture processes are based on SELEXOL, a physical absorption process, because of the high partial pressure of carbon dioxide in the syngas. A process called “double-absorption” is used for capturing sulfur compounds and carbon dioxide. This paper calculated and compared the net outputs, efficiency penalties for CO2 capture part, and net plant efficiencies for different technologies and processes by using EES program. This model tries to treat the IGCC with carbon dioxide capture part as a whole thermal system, instead of just looking at the capture system alone. Different gasification technologies mentioned above will result in various paths and efficiencies of using steam and waste energy in the system. It will make reasonable use of various waste energies and steams for both mechanical and chemical processes to improve the performance of the plant, and incorporate a CO2 capture system into the design concept of the power plant.
Case Studies: Plant Performance Improvements Through the Use of Innovative Condenser Cleaning Technology and Leak Detection Inspection
Authors: Fayard Eric H.
Published: July 2009

One of the largest returns on investment a plant can make is the improved condenser performance as a result of the removal of fouling from tubes within the condenser. The financial impact of a poorly performing condenser can cost the average power station millions of dollars per year in lost revenue. Even a small increase in unit back pressure as a result of tube fouling and air in-leakage can have dramatic results. Performance engineers are continuously reevaluating their choice of cleaning technologies while implementing optimal cleaning schedules as well as air and water in-leakage surveys. With so many choices available for improvement, plant engineers must choose systems that are cost effective, safe and efficient. In addition, the technologies incorporated should have the capability to satisfy a variety of conditions. Those conditions can include: fouling types ranging from bio-films to the most tenacious calcium scale and the potential for air in-leakage from the turbine to the hotwell. As a result, operators must be well informed regarding best available technology. If the plant is nuclear powered, the systems should also provide the least risk to the personnel. This paper will review tube fouling characteristics, advances in cleaning technology and leak detection procedures related to improving overall plant performance.
Start-Up and Shut-Down Simulation of a Thermal Barrier Coated Gas Turbine Bucket Using CFD Code
Authors: Herna´ndez Rossette Alejandro , Mazur C. Zdzislaw , Mun˜oz Rodolfo , Bautista Eder
Published: July 2009

The unsteady aerodynamics and aerothermics of a first stage gas turbine bucket with thermal barrier coating (TBC) and internal cooling configuration were investigated by application of a three dimensional Navier-Stoke commercial turbomachinery oriented CFD-code. Convection and conduction were modeled for a super alloy blade with TBC. This work is the second part of the paper “Unsteady 3-d conjugated heat transfer simulation of a thermal barrier coated gas turbine bucket”, and includes the simulation of shut down cycle. The CFD simulations were configured with a mesh domain of nozzle and bucket inter-stage using real turbine parameter data as boundary condition (BC) at nozzle inlet. The BC’s were adjusted in accordance with standard start-up and shut-down diagram for a gas turbine from Takahashi work [3]. Additionally a parabolic turbine inlet temperature was set for main gas flow. The problem was launched in a minicluster of 8 HP Workstation. Reasonably good comparisons in the main flow parameters with the manufacturer data were obtained. The effects of blade TBC surface temperature changes during a start-up and shut-down cycle were simulated using the Spalart-Allmaras turbulence model. A TBC can be used either to reduce the need for blade cooling (by about 36%) increasing the turbine efficiency, while maintaining identical creep life of the substrate; and increase considerably the creep life of the blade while maintaining level of blade cooling (and therefore allowing the blade to operate at lower temperature for an identical turbine entry temperature).
Testing of a 3 MW High Speed Generator and Turbine Drive for a Hybrid Vehicle Propulsion System
Authors: Thelen Robert F. , Herbst John D. , Wardell Doug , Murphy Brian T.
Published: July 2009

The need for increased design flexibility and reduced weight and volume for electric power generation infrastructure has driven an increased interest in the use of high speed generators directly driven by gas turbine prime movers for both military and commercial power generation applications. This transition has been facilitated by the use of dc distribution and recent advances in the performance of solid state power conversion equipment, enabling designers to decouple the power generation frequency from typical 60 Hz ac loads. Operation of the generator at the turbine output speed eliminates the need for a speed reduction gearbox and can significantly increase the volumetric and gravimetric power density of the power generation system. This is particularly true for turbines in the 3 to 10 MW power range which typically operate with power turbine speeds of 7,000 to 16,000 rpm. The University of Texas at Austin, Center for Electromechanics (UT-CEM) is currently developing a 3 MW high speed generator and turbine drive system for a hybrid vehicle propulsion system as a part of the Federal Railroad Administration’s Advanced Locomotive Propulsion System (ALPS) Program. The ALPS system consists of a 3 MW turbine/alternator prime mover coupled with a 480 MJ, 2 MW flywheel energy storage system. Although designed as the prime mover for a high speed passenger locomotive, the compact turbine/alternator package is well suited for use in marine applications as an auxiliary turbine generator set or as the primary propulsion system for smaller vessels. The ALPS 3 MW high speed generator and turbine drive system were originally presented at the ASME Turbo Expo 2005 [1]. This follow-on paper presents the results of mechanical spin testing and No-Load electrical testing of the high speed generator and the Static Load testing of the generator and turbine drive system at NAVSEA (Philadelphia, PA) with a fixed resistive load. The generator has been tested to a 1.5 MW power level in the Static Load procedures and is being prepared for the final test phase to include dynamic power exchange with the flywheel.
Study on Unsteady Aerodynamic Force of Turbine Blade With Different Mass Flow
Authors: Lan Jibing , Xie Yonghui , Zhang Di
Published: July 2009

The traditional turbomachinery design systems are always based on the assumption of steady or quasi-steady flows. However, unsteady flows such as wake flow, separated flow and shedding vortices are the main factors inducing the excitation force on turbine blade which leads to high cycle fatigue failure of blade. In this paper, the three-dimensional, time dependent, Reynolds-Averaged Navier-Stokes (RANS) equations were resolved using a commercial program CFX based on finite volume method. The unsteady flow fields of three mass flow cases (design case, 110% design mass flow and 85% design mass flow) in a one-and-a-half stage axial turbine (stator/rotor/stator) were investigated in detail and then the unsteady aerodynamic force on the rotational blade was obtained. Frequencies of unsteady disturbances and excitation force factors were obtained by spectrum analysis. It can be seen clearly that the excitation factors at 110% mass flow case are larger than that at the design case. On the other side, the unsteady aerodynamic force on the rotational blade at 85% mass flow case is quite different from the design case. There are two peaks during a stator passing period and the dominate frequency of the tangential blade force is 6000Hz due to large amount of negative incidence angle. The 6000Hz component tangential aerodynamic force amplitude is 6.533N, which is 5.93 times of that at design case and 2.92 times of that at 110% mass flow case. Because of the large amplitude, the unsteady aerodynamic force at small mass flow case is necessary to be taken into account in the forced vibration analysis of blade.
Burning Unprepared “Run of Mine” Coal to Efficiently Fire a Stoker Boiler
Authors: Dumbaugh George D.
Published: July 2009

The successful burning of ROM (Run-of-Mine) Coal to efficiently fire a stoker boiler has been achieved by a new kind of vibrating grate. It has been permanently retrofitted under an existing stoker boiler at Southern Illinois University located in Carbondale. This grate has been available for productive use since June, 2007. The ROM Coal being burned is the high sulfur, bituminous, stoker type, which is 2″ (50mm) × 0″ in size, which usually varies in “fines” content from about 20 to 40%, and it has changing moisture contents that typically vary from 8 to 13%. The heat value varies from 9,000 to 12,500 BTU’s per lb.
Pulse-Width Modulation of Hydrogen Delivery for PEM Fuel Cells
Authors: Perez Aquiles , Abtahi Amir , Zilouchian Ali
Published: July 2009

Pulse-width modulation of hydrogen delivery is proposed to accomplish better performance of PEM fuel cells. By evaluating power consumption patterns and time delays associated with hydrogen and air consumption, optimal functional feedback controllers are developed. By matching the ON and OFF times for the hydrogen and oxygen supply valves, in conjunction with a system fuzzy controller (1), the power output is matched to specific load requirements. The fluid transient behavior is also monitored, to develop functional relationships between the power curve, and the fluid conditions, in order to optimize the system performance. These functions are then used to update and improve the performance of the controller.
A New Re-Fuel System to Process High Water Content Waste to Solid Fuel Using Superheated Steam
Authors: Maruyama Naoki , Tanaka Daisuke , Shimizu Toshiki
Published: July 2009

The increase of waste and the dryness of natural resources including fossil fuels have become serious problems for the sustainable development of industrial activities and our daily living. A great deal of human effort has been put into the careful use of finite resources and environmental impact reduction. The appropriate processing and the effective use of waste are really in demand in light of our social responsibility for manufacturing and energy development. In addition, the construction of a new recycle system for production is also important from the standpoint of the manufacturer’s responsibility. A procedure is being developed to process industrial and municipal wet wastes to solid fuel, called Refuse paper & plastic fuel (RPF), using superheated steam. A drying system using superheated steam is drawing much attention for use with drying high water content materials due to its high thermal efficiency. A material recycle system for processing high water content waste to solid fuel will be introduced in the present study using a demonstration system, and the optimum conditions for the system operation will be examined. The temperature and the quantity of superheated steam required for material drying are evaluated, and the energy consumption and emissions from the system are theoretically estimated and compared. The purpose of this paper is to test-operate a practical waste recycle system, and the results of this new system are compared with the results from a waste incinerator. The effectiveness of a drying system using superheated steam is shown from the standpoint of the reduction of CO2 emissions and energy consumption for the waste processing.
Generator Condition Assessment Through EMI Diagnostics
Authors: Timperley James E.
Published: July 2009

EMI (electromagnetic interference) Diagnostics is an on-line test that can detect a wide variety of defects in generators and associated electrical systems. Trending data is not necessary to develop maintenance recommendations. This paper provides examples of generators in good condition as well as some that need maintenance. Verification of generator maintenance is also presented. Photo 1 shows the preferred RFCT (radio frequency current transformer) location to collect generator data. This conduit goes from the stator winding neutral to a grounding transformer. The split core RFCT is temporally placed around the conduit while data is collected and is then removed.
Verifying Suitability for Service With EMI Diagnostics
Authors: Timperley James E.
Published: July 2009

This paper provides examples of conditions found with nuclear plant electrical equipment by the application of EMI (electromagnetic interference) Diagnostics. This is an on-line test that can detect a wide variety of defects in motors, generators, power cables transformers and isolated phase bus. There is no interruption to service and no risk to the system while data is collected. Photo 1 shows the temporary placement location of a RFCT (radio frequency current transformer) to collect EMI data from this CWP motor. Photo 2 shows the RFCT application on the generator stator grounding transformer. This is the preferred location to collect generator system data.
Gas Turbine Efficiency (GTE) Benefits of GTE Water Wash Systems
Authors: Wagner Thomas , Burke Robert J.
Published: July 2009

The desire to maintain power plant profitability, combined with current market fuel gas pricing is forcing power generation companies to constantly look for ways to keep their industrial gas turbine units operating at the highest possible efficiency. Gas Turbines Operation requires the compression of very large quantities of air that is mixed with fuel, ignited and directed into a turbine to produce torque for purposes ranging from power generation to mechanical drive of pumping systems to thrust for air craft propulsion. The compression of the air for this process typically uses 60% of the required base energy. Therefore management of the compression process efficiency is very important to maintain overall cycle efficiency. Since fouling of turbine compressors is almost unavoidable, even with modern air filter treatment, and over time results in lower efficiency and output, compressor cleaning is required to maintain gas turbine efficiency.
Changing Fossil Unit Startup Process Reduces Rotor Stresses
Authors: Jennings Craig
Published: July 2009

The changes in the energy market dispatching and pricing, have increased the need to start fossil steam turbines faster to meet demand and save fuel. Exelon worked with a consultant to optimize the start up times of their steam turbines resulting in greatly reduced start up times, increased dispatching frequency, and reduced thermal stresses on the turbines. This optimized start up process was achieved by utilization of the Valve Open Start (VOS) and Accelerated Hot Start (AHS) process. VOS utilizes condenser vacuum aligned to the steam generator to produce superheated steam at much lower temperatures and pressures than usual. This steam is drawn through the turbine to warm the unit while the boiler increases in temperature and pressure. The AHS changes the startup sequence of operations by setting up the turbine in a manner that allows the turbine to roll at precisely the time that a perfect temperature match is obtained between the main steam temperature and first stage metal temperature. The use of these processes significantly increases profitability of the units and meets all OEM criteria for unit protection and results in a reduction in rotor thermal gradient, temperature mismatch, and thermally induced vibration.
Wheel Spalling: Simulation of High Speed Wheel Slip
Authors: Cummings Scott M. , Schreiber Patricia
Published: July 2009

The Wheel Defect Prevention Research Consortium (WDPRC) conducted an analysis of the possibility of wheel spall creation under revenue service conditions when a car traverses perturbed and/or lubricated track with the brakes applied. When the brake retarding force acting on a wheelset is greater than the wheelset vertical load multiplied by the wheel/rail coefficient of friction (COF), the wheelset rotational speed will begin to decrease, because the braking force has exceeded the available wheel/rail traction. Due to its large rotational inertia, the wheelset will not immediately stop rotating. As the wheelset slows rotationally, a relative motion (slip) between the contact patch of the wheel and the rail will be introduced due to the continued forward motion of the vehicle. Any sliding action generates heat in the contact patch. If sufficient heat is generated, martensite can form and spalling problems can be initiated. However, as long as the wheelset is rotating, the contact patch is cooled by continually moving circumferentially around the wheel and the tread surface temperature is limited. A NUCARS® multi-body computer simulation model was used to determine wheel normal forces at a variety of speeds across perturbed track. The wheel slip rate was then calculated for each discreet output time step of the NUCARS model. The resulting wheel tread temperature due to the wheel slip was calculated. The predicted contact patch temperature was compared to the austenitic transformation temperature to form a prediction about whether or not martensite would be created. Based on the results of this analysis, it does appear to be possible to create martensite on the wheels of loaded cars under heavy braking while traversing track surface irregularities. However, most operating conditions would not provide the required conditions and this is probably not a major source of spalling.
Parametric Simulation of Rolling Contact Fatigue
Authors: Cummings Scott M. , Schreiber Patricia , Tournay Harry M.
Published: July 2009

Simulations of dynamic vehicle performance were used by the Wheel Defect Prevention Research Consortium (WDPRC) to explore which track and vehicle variables affect wheel fatigue life. A NUCARS® model was used to efficiently examine the effects of a multitude of parameters including wheel/rail profiles, wheel/rail lubrication, truck type, curvature, speed, and track geometry. Results from over 1,000 simulations of a loaded 1,272 kN (286,000-pound) hopper car are summarized. Rolling contact fatigue (RCF) is one way that wheels can develop treads defects. Thermal mechanical shelling (TMS) is a subset of wheel shelling in which the heat from tread braking reduces a wheel’s fatigue resistance. RCF and TMS together are estimated to account for approximately half of the total wheel tread damage problem [1]. Other types of tread damage can result from wheel slides. The work described in this paper concerns pure RCF, without regard to temperature effects or wheel slide events. Much work has been conducted in the past decade in an attempt to model the occurrence of RCF on wheels and rails. The two primary methods that have gained popularity are shakedown theory and wear model. The choice of which model to use is somewhat dependent on the type of data available, as each model has advantages and disadvantages. The wear model was selected for use in this analysis because it can account for the effect of wear on the contacting surfaces and is easily applied to simulation data in which the creep and creep force are available. The findings of the NUCARS simulations in relation to the wear model include the following: • Degree of curvature is the single most important factor in determining the amount of RCF damage to wheels; • The use of trucks (hereafter referred to as M-976) that have met the Association of American Railroads’ (AAR) M-976 Specification with properly maintained wheel and rail profiles should produce better wheel RCF life on typical routes than standard trucks; • In most curves, the low-rail wheel of the leading wheelset in each truck is most prone to RCF damage; • While the use of flange lubricators (with or without top of rail (TOR) friction control applied equally to both rails) can be beneficial in some scenarios, it should not be considered a cure-all for wheel RCF problems, and may in fact exacerbate RCF problems for AAR M-976 trucks in some instances; • Avoiding superelevation excess (operating slower than curve design speed) provides RCF benefits for wheels in cars with standard three-piece trucks; • Small track perturbations reduce the overall RCF damage to a wheel negotiating a curve.
Service Wheel Temperatures and Car Condition in Relation to Thermal Mechanical Shelling
Authors: Cummings Scott M.
Published: July 2009

The Wheel Defect Prevention Research Consortium (WDPRC) examined data from a wayside wheel temperature detector (WTD) located near the bottom of a grade in order to explore the root causes of hot wheels and thermal mechanical shelling. Not surprisingly, the data showed that most hot wheels, defined in this paper as a wayside WTD reading of 260°C (500°F) or greater, are found in trains descending the grade (descending trains), although they can be found in trains ascending the grade (ascending trains) as well. The majority of cars with hot wheels in ascending trains have the brakes applied at all wheel locations in the car, with unreleased or partially released hand brakes as a possible cause. While relatively few descending trains (15 out of 393) had many cars with hot wheels, these trains accounted for more than 20 percent of the descending cars with hot wheels, indicating that operational improvements could substantially reduce the quantity of hot wheels. Seventy-six percent of the descending cars with hot wheels had only a single wheel at or above 260°C (500°F). While the wheels in these cars are generally at higher temperatures than the wheels of other cars in the train, there were large temperature differences between individual wheel locations. Evidence of repeated hot wheel behavior was found in about 37 percent of the group of descending cars with hot wheels and about 20 percent of individual hot wheel locations. Two different car inspections were conducted based on the WTD data. First, a “near-real-time” inspection was conducted in which cars were quickly checked for obvious problems without removing them from the train. Next, an intensive inspection/test/teardown was conducted on bad actor cars, which showed repeated hot wheel behavior. Good actor cars, which repeatedly did not show hot wheels, were also present at the inspection/test/teardown for comparison. The cause of the hot wheels was not evident for the majority of cars at both inspections, however, bad actor cars were found to have twice the historical wheelset replacement rate of good actor cars.
Brake Shoes and Thermal Mechanical Shelling
Authors: Cummings Scott M. , McCabe Tom , Gosselin Dan
Published: July 2009

The Wheel Defect Prevention Research Consortium (WDPRC) conducted a review of existing brake shoe tests to explore the combinations of brake shoe force, time, and wheel/brake shoe coefficient of friction (COF) needed to achieve the temperatures of concern for thermal mechanical shelling (TMS). Data was found involving normally expected brake shoe forces applied to a dynamometer wheel and a variety of test parameters and procedures. All temperatures were measured using a sliding thermocouple pressed lightly against the wheel tread. All testing reported involved new brake shoes that may have different COF properties from used brake shoes. Tests included brake shoe tests conducted in accordance with the Association of American Railroads (AAR) M-926 specification, constant horsepower tests, and simulated stuck brake tests. Tread conditioning brake shoes were investigated, as well as high friction composition brake shoes. Findings from these tests include the following: • Tread conditioning brake shoes produced lower wheel tread temperatures compared to high-friction composition brake shoes. The magnitude of this difference varied depending on the test conditions; • In the dynamometer test most closely simulating revenue service conditions, 37 kW (50 hp) was required to heat wheels above 316°C (600°F); • Different models of high-friction composition brake shoes produced similar wheel temperatures under the parameters of the AAR M-926 tests. The range of average wheel temperatures produced by different models of high-friction composition brake shoes was only about 28°C (50°F) at any point during the test; • Individual brake shoes of the same model usually produced consistent results with respect to wheel temperature. Two exceptions to this statement were observed in the AAR M-926 test results. In a laboratory dynamometer test involving service damaged wheels, the WDPRC was unable to produce any measurable reduction in wheel tread defect size through the application of tread conditioning brake shoes. However, four service trials of tread conditioning brake shoes showed potential benefits in using tread conditioning brake shoes to reduce the number of wheelsets removed for tread damage.
The Influence of Manufacturing Variations on a Crash Energy Management System
Authors: Mallon Philip , Perlman Benjamin , Tyrell David
Published: July 2009

Crash Energy Management (CEM) systems protect passengers in the event of a train collision. A CEM system distributes crush throughout designated unoccupied crush zones of a passenger rail consist. This paper examines the influence of manufacturing variations in the CEM system on the crashworthiness of CEM passenger rail equipment. To perform effectively, a CEM system must have certain features. A coupling mechanism allows coupled cars to come together in a controlled fashion and absorb energy. A load transfer mechanism ensures that the car ends mate and maintain contact. A principal energy absorber mechanism is responsible for absorbing the vast majority of crash energy. These components function by providing an increasing force-crush characteristic when they are overloaded. The force-crush behavior can vary due to manufacturing tolerances. For the purposes of this research, the pushback coupler, the deformable anticlimber, and the primary energy absorber were the devices that performed these functions. It was confirmed in this study that the force-crush characteristic of the pushback coupler and the primary energy absorber have the greatest influence on crashworthiness performance. To represent the influence of these parameters, the average force of the pushback coupler and the average force of the primary energy absorber were examined. A cab-led passenger train impacting a standing freight consist was represented as a one-dimensional lumped-mass model. The force-crush characteristic for each coach car end was adjusted to examine the effects of variation in manufacturing. Each car end was modified independently while holding all other car ends constant. The model used in this study was designed to be comparable with a 30 mph, full-scale, train-to-train CEM test. Using crush distribution and secondary impact velocity as measures of crashworthiness, the standard CEM consist performance has a maximum crashworthiness speed limit of 40 mph. Percent total energy absorbed was used as a means of comparison between cars for each consist configuration. When energy absorption levels are decreased at any particular car end, crush tends to be drawn towards this car end. Correspondingly, when available energy levels are increased at a car end, crush is drawn away from this car end. For both cases, the overall distribution of crush has more of an effect locally and less of an effect at other coupled interfaces. This paper shows that moderate variations in crush behavior may occur due to manufacturing tolerances and have little influence on the crashworthiness performance of CEM systems.
Evaluation of Occupant Volume Strength in Conventional Passenger Railroad Equipment
Authors: Carolan Michael , Perlman Benjamin , Tyrell David
Published: July 2009

To ensure a level of occupant volume protection, passenger railway equipment operating on mainline railroads in the United States must be designed to resist an 800,000-lb compressive load applied statically along the line of draft. An alternative manner of evaluating the strength of the occupied volume is sought, which will ensure the same level of protection for occupants of the equipment as the current test, but will allow for a greater variety of equipment to be evaluated. A finite element (FE) model of the structural components of a railcar has been applied to examine the existing compressive strength test and evaluate selected alternate testing scenarios. Using simplified geometric and material properties, a generic single-level railcar model was constructed that captured the gross behaviors of the railcar without excessive processing time. When loaded, the carbody structure exhibits some single beam-like behaviors. Application of the existing 800 kip compressive load results in a significant bending moment as well as significant compressive forces. The alternative load cases examined show that a larger total compressive force may be distributed across the end structure of the railcar and result in similar stress levels throughout the structural frame as observed from application of the conventional proof load.
Development of Residual Stresses in a Railroad Wheel Through Rim Spray Heat Treatment
Authors: Dedmon Steve L. , Pilch James , Gordon Jeffrey
Published: July 2009

Understanding how residual stresses develop during a typical rim spray quench and subsequent tempering operation is a fundamental objective necessary to gain knowledge of how wheels behave when under service loads. In this study, we have used specially modified and validated ANSYS software to calculate plastic deformations as they develop during the heat treatment process. Plastic deformations, including creep, were determined to follow stages which were both dependent on time of quench and depth from the taping line. Residual stresses developed from these deformations are also discussed.
Dynamic Bearing Testing Aimed at Identifying the Root Cause of Warm Bearing Temperature Trending
Authors: Tarawneh Constantine M. , Wilson Brent M. , Cole Kevin D. , Fuentes Arturo A. , Cardenas Martin
Published: July 2009

Bearing temperature trending is an ongoing problem that is receiving considerable attention in the railroad industry. Currently, bearings that display this phenomenon are removed from service since a trended bearing exhibits similar behavior to a burn-off bearing at the end of its life. The removal and replacement of these bearings is a costly process, in addition to causing undesirable time delays. Even though this topic has received ample attention, to date, research efforts have been unable to identify the mechanism(s), or the root cause(s), of this troubling phenomenon. Motivated by the latter, the study presented here focuses on identifying the root cause of the bearing temperature trending seen in service. To this effect, eight laboratory experiments were performed using three bearings that had been removed from service due to temperature trending, along with their mates. Laboratory experiments were performed on a test rig that accommodates four Class F bearings simultaneously rotating at a speed of 536 rpm, which corresponds to a train traveling with a velocity of approximately 57 mph (91.7 km/h). The laboratory study was successful in duplicating the bearing temperature trending phenomenon seen in service, and consequently identifying the main source of this problem. Data presented will include both temperature and vibration profiles measured during normal and trending phases, along with inspection results.
A Nonlinear Multi-Field Coupling Finite Element Method for Polarization Switching in Ferroelectrics
Authors: Wang Jie , Kamlah Marc
Published: July 2009

A three-dimensional nonlinear finite element formulation for ferroelectric materials is developed based on a principle of virtual work. The formulation includes the coupling of three physical fields, namely polarization field, electric field and strain field. The developed finite element formulation is employed to investigate the polarization distribution near a flaw in a ferroelectric single crystal under mechanical loadings. It is found that the polarization switching takes place near the flaw tip if the loadings exceed a critical value. In the simulation, we do not take any prior assumptions, i.e. without any switching criterion, on the polarization switching. The polarization switching is a result of the minimization of the total energy in the simulated system.