EPRI-Steam Turbine Generator Notes

Mechanical Hydraulic Control System Maintenance Guide in ProgressTurbine mechanical hydraulic control (MHC) systems are still in wide use today on units that are 30–50 years old. These are inherently reliable control systems, but they require knowledge of the expected wear characteristics of mechanical components and system setup procedures. Work force changes by plants and equipment suppliers have reduced the level of expertise that can be applied to adequately maintaining and troubleshooting MHC systems. In response to these issues, early this year, work began on completion of an MHC system maintenance guide. The report will be completed by March 2009.

continued on page 2

This technical report will detail basic MHC operation, inspection, setup, troubleshooting, and maintenance. It will help new systems engineers become familiar with the problems and corrective actions needed to keep MHC-related unavailability low. The intent of the report is to cover the MHC devices for the General Electric (GE) fossil and Westinghouse fossil steam turbine valve applications.

ContentsUpgrade to Guide for On-Line Testing and Monitoring of Turbine Generators .................................................................................. 2Shutdown Protection of Steam Turbines Using Dehumidifi ed Air ............. 3Advanced Labyrinth Seal Project ...................................................... 3Additions to Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections ............................ 4EPRI Turbine-Generator Program Holds 2007 Steam Turbine-Generator Workshop/Vendor Expo and Summer 2007 Users Group Meeting ....... 6EPRI Turbine-Generator Users Group Holds Winter 2008 Workshop/Meeting in San Diego ................................................................... 6Tracking Laser Coordinate Measurement System Application Project Completed .................................................................................. 7Boiler/Reactor Feedpump Turbine Rotor End-of-Life Project .................... 7The Effect of Organics/Amines on Turbine Performance ....................... 7Turbine and Generator Compliance to NERC Standards Interest Group Workshop ................................................................................... 8Evaluation of Low-Pressure Turbine Stator Coatings to Reduce Erosion on Rotor Blades ............................................................................ 8Reference Book for Steam Turbine-Generator Products ......................... 8Generator High-Voltage Bushing Installation Guide .............................. 9Non-Intrusive Methods to Validate NERC Standards: Steam Turbine Frequency Response (MOD-027)................................................... 10Inspection Criteria for Generator Rotors Subjected to Abnormal Negative Sequence Current .......................................................... 10New Turbine-Generator Projects Delivered in 2007 ...........................11Fifth EPRI Turbine-Generator Program Technology Transfer Workshop and Summer 2008 TGUG Meeting ................................................12Productivity Improvement Expert Reviews 2008 .................................12Improving the Financial Risk of an Aging Turbine-Generator Fleet ..........12Steam Turbine Valve Actuator Condition Assessment Guide .................13Valve Metallurgy Guides for U.S. and International Turbine Units...........14Additions to the Turbine-Generator Preventive Maintenance Database ...................................................................................15Evaluation of Electrohydraulic Control Fluid ......................................15Steam Turbine Bolting Maintenance Guide .......................................16Looking Forward: Program 65 and NSTI ..........................................17Stress Corrosion Cracking and Corrosion Fatigue Workshop to Be Held .....................................................................................182009 European TGUG Workshop and Meeting ...............................18

2008 Boiler and Reactor Feed Pump Turbine (B/RFPT) Workshop ........18

Turbine-Generator Supplemental Projects ..........................................19

Determination of β Parameter for 12% Cr Turbine Blades Using Fatigue Sensor Technology ............................................................21

Axial Entry Disk Blade Attachment NDE Performance Demonstration .....21

Guide for Inspection of Low-Pressure Turbine Blades .......................... 22Optimization of Fatigue Sensor Measurement for Curved Blade Surfaces .................................................................................... 22Upcoming Events ........................................................................ 23Program Staff ............................................................................. 23Steam Turbine Blade Failure Root Cause Analysis Guide .................... 23

July 2008 Fossil and Nuclear Steam Turbine-Generators

Typical Cam Shaft/Roller MHC System Controls

Steam Turbine-Generator Notes 2 July 2008

Steam Turbine-Generator Notes Is published by the Electric Power Research Institute's (EPRI's) Fossil and Nuclear Steam Turbine-Generator Program

1300 W.T. Harris Blvd., Charlotte, NC 28262, fax 704.595.2867 NSTI/Program 65 Contact: Alan Grunsky, 704.595.2056, [email protected]

Because just six nuclear units in the world still employ these types of turbine control systems (as opposed to the more modern electrohydraulic control systems), the initial report will contain only limited information about nuclear units. As the project progresses, we will investigate the possibility of adding more nuclear MHC information to the final report. Including nuclear information greatly expands the original scope of the project.

The current outline of most of the information to be included in the report is as follows:

1. Technical Description. This section will include a general description of the GE, Westinghouse 300#, and Westinghouse 150# MHC systems, with an emphasis on front standard (pedestal) components, lube oil tank components specifically related to control functions (but excluding the lube oil system itself ), valve hydraulic cabinet components, and mid-standard components. The components included are as follows:a. For GE units: speed/load changer, load limiter, speed

governor, secondary speed relay, acceleration relay, secondary pilot valve, linkages, cutout governor, initial pressure regulator, stop valve bypass valve controller, intercept valve (IV) speed governor, IV dashpot breakdown link, overspeed trip, backup overspeed trip, main stop valve/reheat stop valve trip devices, trip anticipator, test devices, vacuum trip, thrust bearing trip device, electrical trip interface, steam seal regulator, main shaft oil pump, and control rotor (gear on a few units)

b. For Westinghouse (150# and 300#) units: speed/load changer, auxiliary governor, load limit valve, oil impeller, throttle pressure regulator, governor emergency trip valve, throttle valve controller, throttle valve servomotor, overspeed trip valve, trip manifold, main oil pump, control valve (CV) servomotor, IV servomotor, multiple orifices and check valve, and control rotor

Mechanical Hydraulic Control System Maintenance Guide in Progress

continued from page 1

2. Inspection. This section will include inspection criteria for the GE and Westinghouse turbine control devices. Copies of data sheets used to record measurements and condition will be included. The criteria for inspecting the controls system will be given. Included will be common adjustments, such as setting (measuring) regulation, CV crack point, and overspeed set points.

3. Maintenance. The maintenance section will include preventive and corrective maintenance tasks for the GE and Westinghouse turbine control devices. Applicable procedures for disassembly, repair, and reassembly of the components will be included, and any special tooling will be listed. Any safety considerations for working on the control devices will be given. Included will be references to partial upgrades or modifications that have typically been performed.

4. Post-Maintenance Commissioning. This section will describe activities required to set up and perform pre-operational checks on the controls system prior to starting the unit following a major outage, whether or not major work was performed on the controls system.

5. Troubleshooting. This section will include a guide to troubleshooting operational problems. Common operational problems, symptoms, causes, and solutions will be included.

For more information on this project, contact Alan Grunsky, 704.595.2056, [email protected].

Upgrade to Guide for On-Line Testing and Monitoring of Turbine GeneratorsThe EPRI report Guide for On-Line Testing and Monitoring of Turbine Generators (1006861), released in 2002, provides information about failure mechanisms for all major generator manufacturers and identifies the most appropriate on-line detection systems.

The objectives of the project are to add guidance for off-line testing and to refine the assignment of appropriate failure mechanisms by including age and duty cycle of the generator. The report will be available no later than December 31, 2008.

For more information, contact Jan Stein, 650.855.2390, [email protected].


Shutdown Protection of Steam Turbines Using Dehumidifi ed Air EPRI’s Program 88 (Heat Recovery Steam Generators), Program 64 (Boiler and Turbine Steam and Cycle Chemistry), Program 65 (Steam Turbines, Generators, and Balance-of-Plant), and the Nuclear Steam Turbine-Generator Initiative released a report on the use of dehumidified air in protecting steam turbines during shutdown. The report, published March 2008, is Shutdown Protection of Steam Turbines Using Dehumidified Air (1014195).

This guidance report provides a methodology by which fossil and nuclear plant personnel can assess application of dehumidified air for shutdown protection of steam turbines in new and existing units alike. Consistent with EPRI’s guiding principles for shutdown protection, the comprehensive approach considers shutdown protection requirements of other components.

For more information on this project, contact Jim Mathews, 704.595.2044, [email protected], or Alan Grunsky, 704.595.2056, [email protected].

A Dehumidifi cation System

Advanced Labyrinth Seal Project The overall research goal of this project is to define a labyrinth seal configuration (knife shape, spacing, rotor surface features, materials, and so on) that reliably restricts leakage flow over a long period and is tolerant of typical mid-span shaft lateral vibration amplitudes. The knowledge gained from this research includes detailed information on the effect of various combinations of labyrinth design parameters on leakage performance. In addition, an advanced analysis methodology will be tried and reported. Two major drivers in today’s generation industry are 1) increased reliability/reduced downtime and 2) increased thermal performance. Both will be positively affected by this project.

For additional project information, contact Gary Golden, 865.218.8111, [email protected].


Additions to Guidelines for Reducing the Time and Cost of Turbine- Generator Maintenance Overhauls and Inspections

Over a period of more than seven years, the EPRI Turbine-Generator (TG) Program accumulated information that can assist utilities/plants with TG maintenance. This information is contained in the seven-volume set Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls. In 2007, new material was added to Volume 2, Repair Procedures, and Volume 4, Blade and Rotor Procurement Specifications.

Any company that is currently in a multi-year (at least three years) contractual commitment to Program 65 can order the entire seven volumes as a four-CD set. If you meet this requirement, you can order the 2007 EPRI product 1014134. This four-CD set is also available to Nuclear Steam Turbine Initiative funders.

Companies that are funding the TG Program on an annual basis (regardless of the number of consecutive years of funding) cannot order 1014134, but the additions for 2007 have been compiled into one supplemental document—EPRI report 1016387—that you can order. This supplement, combined with the seven-volume set from 2006, is equivalent to the full and current set of Guidelines.

The general content of each volume is as follows:

CD 1•

Volume 1: General Practices

The first volume presents general –

practices for each of the fundamental maintenance activities that are usually associated with an outage: TG condition assessment (in-service), pre-outage planning and bidding, unit shutdown procedures, disassembly and recording clearances, foreign material exclusion (FME) process information, TG condition assessment (off-line), oil flushing, rotor alignment

and balancing, pre-startup checks, and post-outage activities. Volume 1 also contains, as appendices, a sample TG outage report, more than 150 sample data sheets, and a TG FME program/process guidance document.

Volume 2: Repair Procedures

The second volume provides detailed –

repair procedures to guide the pre-bid, inspection, disassembly, and repair of critical turbine and generator components. Examples of these procedures are bearing spin-casting/repuddling, diaphragm and nozzle block partition repair, blade tenon repair, hydrogen seal repair, horizontal joint casing repair, main steam stop valve cap repair, generator hydrogen seal inspection/repair, alterrex inspection/maintenance, inspection/testing/re-wedging generator stators, and collector ring/brush rigging maintenance.

Volume 3: Balancing and Alignment Specifications

The third volume contains –

comprehensive alignment and balancing primers and high- and low-speed balancing procedures for turbines, generators, and exciters.

Volume 4: Blade and Rotor Procurement Specifications

The fourth volume provides detailed –

specifications for the procurement of turbine buckets, to include blade frequency testing and tuning guidance, high-pressure/intermediate-pressure/low-pressure (HP/IP/LP) fossil rotors, HP/LP nuclear rotors, generator rotor rewind, a new generator rotor, generator stator rewind, new generator

stator, generator excitation system, turbine insulation, complete turbine outage services, and turbine bolting.

Volume 5: Turbine Directory and Database

The fifth volume presents a directory –

and database of large (>75 megawatts electric) turbines that operate with last-stage buckets of 23 inches (58 centimeters) or longer. The list now contains U.S. and international units. Presented in this database are original turbine manufacturers and their equipment designations and plant/unit status (as of 2001). To further assist users of this directory in identifying operators who might have units that share common features, the data are sorted and presented by L-0 bucket length and the manufacturer’s design designation (where this could be identified). Included are plants/units that have been shut down and plants/units that have been cancelled. A table listing North American and international units that have completed major component replacements/modifications is also included.

CD 2•

Volume 6: HP/IP Blade/Disk Design and Inspection Specifications

The sixth volume presents blade/ –

disk design audit and inspection procedures for HP and IP steam turbine blades/disks. This information aids turbine maintenance personnel in assessing solid particle erosion, high-cycle fatigue (HCF), low-cycle fatigue (LCF), and creep rupture damage to HP and IP blading.

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Additions to Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections


CD 3•

Volume 7: LP Blade/Disk Design and Inspection Specifications

The seventh volume presents blade/ –

disk design audit and inspection procedures for LP blades/disks. This information aids turbine maintenance personnel in assessing stress corrosion cracking (SCC), HCF, and LCF damage to LP blading.

CD 4•

TGAlign and TGAlign-SI Computer Programs and User Manuals

TGAlign software (available in –

English-unit and SI-unit versions) is a robust computer program that determines the optimum coupling alignment for a TG rotor system, thereby reducing the outage time for steam TGs.

The utility technical advisory group (TAG) met in early 2007 through a web cast, and the TAG decided what would be added to the Guidelines CDs. The following additions were made to the seven-volume set in 2007:

Addition to Volume 2: •

“Collector Ring, Commutator, –

Brush and Brush Holder Rigging Maintenance Manual” as a new Section 8.13

Additions to Volume 4:•

Specifications for purchasing a –

generator excitation system (new Section 10) and an example of a generator excitation system procurement request for quote (RFQ) as a new Appendix G

Specifications for purchasing new –

turbine bolting as a new Section 11 and an example of a turbine bolting procurement RFQ

A new Appendix K, to supplement –

the existing purchase specifications for turbine blading that appear in Section 1, titled “Guidelines for Blade Frequency Testing and Tuning Acceptance”

The TAG met again by web cast in March 2008 to discuss potential additions. The following information will be added to the Guidelines CD set in 2008 based on budget constraints and availability of the information:

Best practices for hydrogen seal •installation and long-term preventive maintenance for hydrogen seals

Best practices for optimizing TG •rotor centerline alignment

Recutting a Worn-Out Helical Groove

Boiler/reactor feedpump turbine •(B/RFPT) blading purchase specification and sample RFQ

Parametric analysis of TG •vibration on bearing life

Guidelines for purchasing a •complete B/RFPT unit

A list of original equipment •manufacturer service bulletins and technical information/advisory letters

A grit-blasting procedure •

For more information on Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections, contact Alan Grunsky, 704.595.2056, [email protected]. You can also ask Alan about becoming a multi-year funder of Program 65 or about your company’s current participation level.


EPRI Turbine-Generator Program Holds 2007 Steam Turbine-Generator Workshop/Vendor Expo and Summer 2007 Users Group Meeting

10th Steam Turbine-Generator Workshop and Vendor Exposition

On August 13–15, 2007, the EPRI Turbine-Generator (TG) Program held its 10th Steam Turbine-Generator Workshop and Vendor Exposition at the JW Marriott Desert Ridge Resort & Spa in Phoenix, Arizona. Although the temperature reached 110°F (43°C) almost every day, the meeting was a huge success, with more than 250 attendees at the three-day workshop and 48 vendors participating in the vendor expo that was held Monday and Tuesday evenings.

On Monday morning, two pre-workshop/vendor expo workshops were conducted. One was a tutorial on boiler/reactor feedpump turbine design, and the topic of the second was generator core testing.

Multiple sessions were conducted in parallel over the three days, with the following topics discussed:

Steam turbines•

Nondestructive evaluation for TGs•

Generator on-line monitoring and condition assessment•

Generator core, rotor ground, and stator •cooling water leak monitoring

Generator upgrades and maintenance•

Steam turbine R&D•

Generator rotor turns and grid disturbance detection•

Use of monitoring data •

Summer Turbine-Generator Users Group Meeting

The summer 2007 Turbine-Generator Users Group (TGUG) meeting was held August 16–17 in conjunction with the 10th Steam Turbine-Generator Workshop at the same hotel in Phoenix, Arizona. On Thursday evening, an additional session was conducted. This was the Generator Clip-to-Strand TGUG working group, led by Tom Phelan of Constellation Energy; the session had approximately 25 attendees.

All information shared during the week’s meeting/workshop can be viewed on the EPRI web site through the following address: http://www.epri.com/tgug/pastmeetings.html.

For additional information on the EPRI TG Program or the TGUG and its activities, contact Alan Grunsky, 704.595.2056, [email protected].

EPRI Turbine-Generator Users Group Holds Winter 2008 Workshop/Meeting in San DiegoThe 17th Turbine-Generator Users Group (TGUG) meeting was held in San Diego, California, at the Marriott Mission Valley Hotel on January 23–25, 2008 in conjunction with the associated workshop that took place January 21–22 at the same location.

More than 250 registrants and 30 vendors participated in the vendor fair that was held on Monday and Tuesday evenings of that week. Day 1 of the workshop was a turbine-generator (TG) combined session, “North American Electric Reliability Corporation Validation Requirements/Regulations/Issues from the Turbine-Generator Perspective.” On Tuesday, two workshop sessions were conducted; the title of the turbine session was “TG Upgrades: Planning, Procurement, and Installation,” and the generator session was “Generator Rotor Stator and Exciter Preventive Maintenance (Overhauls/ Refurbishments): Strategy Versus Retrofit or Replacement.”

On Wednesday, an evening session continued the Tuesday turbine session called “TG Upgrades: Issues and Experiences.” The session was led by Danny Chlou (Exelon) and Paul Zayicek (EPRI). Another evening session was held on Thursday night with a meeting of the Generator Clip-to-Strand TGUG working group.

All information shared during the week’s meetings/workshops can be viewed on the EPRI web site through the following address: http://www.epri.com/tgug/pastmeetings.html.

For more information, contact Alan Grunsky, 704.595.2056, [email protected].


Boiler/Reactor Feedpump Turbine Rotor End-of-Life ProjectIn an effort to address a rising number of problems with the power industry’s boiler/reactor feedpump turbines (B/RFPTs), EPRI has initiated several activities aimed at helping our members solve these issues. In 2007, a survey was taken to identify prevalent problems in the industry, and the results will be augmented by another survey. Along with this effort, EPRI is kicking off an industry B/RFPT rotor end-of-life project that will address the flow path problems that members are encountering today. We ask that you take time to participate in upcoming survey efforts or that you send this survey to someone within your utility who will.

For additional information on this project or other B/RFPT issues, contact Gary Golden, 865.218.8111, [email protected].

The Effect of Organics/Amines on Turbine Performance As the demand for power reaches critical points and the cost of electricity production rises, so does the need for better turbine efficiency. Program 65/NSTI is proceeding with the organics/amines (O/As) project to investigate the increase in performance when O/As are injected into the steam path. EPRI will monitor the difference in nucleation of steam after O/As have been injected into the steam path: specifically, the steam will pass through a converging/diverging nozzle and will be monitored for performance improvements. Results of this project will be available March 2009.


Tracking Laser Coordinate Measurement System Application Project Completed

Laser Tracker ComponentsSource: FARO Technologies, Inc. © 2007 All rights reserved

Another example of how the EPRI Turbine-Generator Program continues to explore the use of other industry technology is the publication of Tracking Laser Coordinate Measurement System Application for Turbine Outage Activities (1014136) in December 2007. The objectives of this research were to identify the turbine measurement tasks that could potentially be performed more efficiently with a tracking laser coordinate measurement system and to describe and demonstrate the basic process for using the system.

FARO Technologies, Inc. was solicited to demonstrate its laser measurement system, adapt its software system to include several sample turbine measurement data sheets, and provide detailed operating instructions for taking measurements using these selected data sheets.

This report includes a list of tasks that could possibly be performed with a tracking laser coordinate measurement system, a description of the basic process of using the system, the advantages and disadvantages of the system, and two examples of how the system can be used.

For more information on this report, contact Alan Grunsky, 704.595.2056, [email protected].


Turbine and Generator Compliance to NERC Standards Interest Group WorkshopA number of the standards approved and proposed by the North American Electric Reliability Council (NERC) directly address turbines and generators, including MOD-024 Verification of Generator Gross and Net Real Power Capability, MOD-025 Verification of Generator Gross and Net Reactive Power Capability, PRC-019 Coordination of Generator Voltage Regulator Controls with Unit Capabilities and Protection, MOD-026 Verification of Models and Data for Generator Excitation System Function, and MOD-027 Verification of Generator Unit Frequency Response. In addition, a number of standards relate to data sampling, reporting, retention, and notification between the generator owner and transmission system operator. The U.S. Energy Policy Act of August 2005 contains provisions that make compliance with NERC standards mandatory and enforceable.

An interest group to share compliance experience is being formed. DTE Energy will host the first meeting on August 21–22, 2008. The day-and-a-half-long agenda includes an educational course, case studies, and reports.

Participation is free to members of EPRI’s Generation Program 65 (Steam Turbines, Generators, and Balance-of-Plant), Program 85 (Renewables and Hydropower Generation), the Nuclear Steam Turbine Initiative, and Power Delivery and Utilization Program 40 (Grid Planning). All other EPRI members pay a $5,000 participation fee.

Engineers and technicians who perform the testing and validation, utility compliance administrators, and transmission system planners are invited to participate.

For more information, contact the EPRI Customer Assistance Center, 800.313.3774, [email protected]. EPRI’s technical contact is Jan Stein, 650.855.2390, [email protected].

Evaluation of Low-Pressure Turbine Stator Coatings to Reduce Erosion on Rotor Blades This supplemental project is investigating the potential benefits of stator surface coatings in reducing erosion damage produced by water droplets. This investigative project, which is taking place at the University of Tennessee Space Institute, involves applying hydrophobic coatings to the stator surface in order to change the characteristics of the coarse water droplets discharged from the stator trailing edge.

The cascade sections have been constructed, and the wind tunnel configuration is being put into place. A high-speed camera captures the water droplet size coming off the trailing edge of the stator blades. For comparison, there is a baseline cascade section along with cascade sections with the hydrophobic coatings.


Reference Book for Steam Turbine-Generator Products Since its inception, the EPRI Steam Turbine-Generator Program has created a multitude of reports and other products. A compilation of more than 125 product summaries that describe EPRI research performed over the past 20 years is contained in the EPRI report Description of Past Research: EPRI Fossil and Nuclear Steam Turbines and Generators—Volume 4 (1016900). The summaries are arranged by categories related to generators, steam turbines, software, Technology Innovation reports, and other related miscellaneous subject areas. Each product summary includes an abstract; a description of the report’s objective, approach, and results; and EPRI’s perspective. The report is a useful references for EPRI-member organizations that are seeking past reports on specific topics of interest. EPRI updates this report yearly to include new research reports and software.

For more information, contact Alan Grunsky, 704.595.2056, [email protected].


Generator High-Voltage Bushing Installation Guide It is not uncommon for bushings to be 50 years old. During major outages, the bushings are inspected, and depending on their condition, they can be repaired or refurbished. Eventually, the old bushings will need to be replaced, and proper installation of generator bushings is essential to safe operation of the unit. The bolted connection between the lead box and the bushing flange must be gas-tight in order to prevent pressurized hydrogen from escaping from the generator.

The objective of this project is to produce a comprehensive report on the installation of generator high-voltage bushings. The report will address the following issues:

Bolted connection design, including the following topics: •

Bolt torque versus gasket seating stress requirements –

Bolt material selection versus bolt torque requirements –

Magnetic versus non-magnetic bolting –

Impact of lubricated versus unlubricated bolts –

Gasket material selection versus bolt torque requirements –

Terminal plate material versus bolt torque –

and bolt material considerations

The impact of sealants on gasket sealing –

The impact of bushing flange and terminal plate surface –

finish and preparation on gasket sealing characteristics

Bolt engagement design considerations in the –

flange-to-terminal-plate interface

Torque application methods (tooling) –

Bolt locking methods –

Inspection requirements and testing before and after installation –

Handling to prevent corrosion or accidental cracks and breakage –

Maintenance check intervals and installation –

Proper bolting of the flexible links to isophase bus conductors –

Original equipment manufacturer (OEM) design and •installation, including the following topics:

ABB, General Electric, and Siemens/Westinghouse/Haefely –

Bushing cooling systems (air, water, and oil), –

differences, and assembly/disassembly methods

Pressure-testing of oil- and water-cooled bushings –

Deterioration and possible methods of repair, •including the following topics:

Porcelain versus alternative insulators –

Refurbished bushings –

Leak-checking methods –

Sealants –

A list of OEM technical information letters, –

service bulletins, and notices

Removal and installation, including the following topics: •

Area preparation –

Work area egress –

Rigging and handling the weights of the bushings, current –

transformers, and neutral/isolated phase bus duct enclosures

Foreign material exclusion considerations –

Tools and tool staging –

Proper handling of high-voltage bushings –

during removal and installation

Electrical field testing of the replacement –

bushing; high-potential (Hipot) testing

Mechanical (for example, pressure) field –

testing of the replacement bushing

The amount of contact required on the connection –

between the bushing and generator lead

Termination taping –

Replacement criteria and spares, including the following topics:•

Inspection frequency and scope –

Replacement criteria –

When to keep spares and how many to keep –

Recommendation for reinspection and bolt –

re-tightening intervals

Storage requirement (for example, vertical storage) –

The report will be available no later than December 31, 2008.


Sealants


Non-Intrusive Methods to Validate NERC Standards: Steam Turbine Frequency Response (MOD-027)

Inspection Criteria for Generator Rotors Subjected to Abnormal Negative Sequence Current

Negative sequence heating of the rotor is induced by three things: asynchronous operation of the rotor, such as motoring; phase unbalance in the stator winding caused by unsymmetrical loads or faults; and harmonic currents introduced in the grid by, for example, static frequency converters.

The objective of this multi-year project is to define the level of negative sequence current that will warrant rotor inspection for damage to the forging, retaining rings, and rotor wedges. The EPRI report Negative Sequence Effects on Generator Rotors (1014910), published in 2007, provides easy-to-use models for estimating the tooth and wedge temperature during a negative sequence fault.

In 2008, work will continue on estimating heating of teeth, pole face, and retaining ring shrink fit and on the heating effects experienced during rotor motoring. Toshiba has agreed to validate this work by

comparing it to the results obtained by full-blown analysis. Formulas and flow charts required for development of inspection criteria software will also be developed. User-friendly software will be developed in 2009.


MOD-027 requires the generator operator to verify the generator unit frequency response (that is, the megawatt response of the unit to deviations in system frequency) for use in models for reliability studies. Each North American Electric Reliability Council (NERC) region must maintain procedures for the verification of frequency response, including the following:

The response time, to be modeled up to 30 seconds for steam units•

The verified manufacturer and type of turbine speed governor •controls

The verified model for each turbine speed governor control with •any associated dead band, gains, time constants, and limits

In 2007, three utilities funded a supplemental project to derive generator, excitation system, and governor parameters from off-line and on-line tests (see EPRI report 1015241, Power Plant Modeling and Parameter Derivation for Power System Studies). The Power Plant Parameter Derivation (PPPD) software allows engineers to derive parameters for standard (that is, Institute of Electrical and Electronics Engineers) generator and exciter models and for combustion turbine governor models.

The objective of this project is to extend the PPPD software to calculate steam turbine parameters from staged tests and system disturbances

(for example, loss of a major generator that results in system frequency deviations) that are automatically captured during ambient monitoring. The primary objective is to investigate and prove whether ambient monitoring can be used to capture disturbance data and thus be used with automated software to fit the parameters of the turbine-governor model for large steam turbines.

The project includes the following tasks:1. Model and method development for large steam turbines2. A staged test of a large steam turbine at a host utility3. Ambient monitoring for system events at a host utility (for the

same unit tested in Task 2)4. A comparison of models developed by both methods5. Presentation at the Generation Advisory Meeting 6. Publication of the final report7. Delivery of prototype software to the EPRI Software

Engineering Team8. Workshop9. Software release in 2009

The report will be available no later than December 31, 2008.



New Turbine-Generator Projects Delivered in 2007

Guide for Stator Winding Coil Insulation Repair Report 1014909

Sometimes stator winding insulation is damaged from mechanical impact during operation; more frequently, however, the insulation is mechanically damaged during wedge replacement or rewinding. Under certain circumstances, it is possible to repair the stator coils and bars in situ without having to replace the coils. This report, a CD, provides guidance about when such localized damage can be reliably repaired and outlines the basic repair methodology.

Guide for Rotating Machine Stator Winding Hipot Testing Report 1014908

High-potential (Hipot) withstand testing, which indicates whether the stator winding insulation in a generator is fit for service, is a standard factory acceptance test for a new machine. The same test can be used on an existing generator to assess the machine’s condition. EPRI surveyed owners of generating facilities about Hipot testing on existing machines. This report answers questions raised during the survey, including when to test, the type of test to perform, and the proper test voltage.

Generator Control Testing to Certify Reactive Power Capability, Excitation System Functions, and Frequency Response Report 1014911

Accurate simulation models of power system equipment are beneficial to all power system participants: such models maximize equipment availability, minimize losses,

avoid interruptions, and protect equipment. This report summarizes various methods of obtaining the model data and describes the benefits and drawbacks of each.

Negative Sequence Effects on Generator Rotors Report 1014910

See p. 10 for article.

Steam Turbine Blade Failure Root Cause Analysis Guide Report 1014137


Boresonic Inspection Primer Report 1014140

Turbine rotor reliability and remaining life prediction are areas of concern for utilities that are interested in component life extension and longer inspection outage intervals. Boresonic inspection of the highly stressed rotor bore area provides the nondestructive inspection data that are among the inputs used in determining rotor operability and remaining life. Determination of the boresonic system’s performance is essential in establishing confidence levels for the boresonic data. The EPRI report Boresonic Inspection Primer (1014140) provides guidance on evaluating performance of boresonic inspection systems as well as guidance in the evaluation and selection of boresonic inspection providers.

Inspection and Damage Assess-ment of Turbine Casing Cracks Report 1014138

This report presents guidance on determining run/repair/retire options for cracked casings. Nondestructive evaluation techniques and

metallurgical evaluation for the assessment of cracking are addressed. Considerations to make when deciding when to initiate a crack repair—repair methods for turbine casing cracks include mechanical methods and weld repair—as well as the conditions that preclude repair are also described. Utility experiences with repair methods are documented.

Steam Turbine On-Line Blade Condition Assessment Report 1014143

This report evaluates commercially available and emerging technology for on-line condition assessment of large steam turbine blades, with concentration on technologies that can detect changes in blade vibrational characteristics associated with propagating cracks. Finite element modeling and analysis in combination with fracture analysis was used to assess the effects of crack propagation on measurable L-0 blade characteristics. Provided in the report are recommendations for appropriate monitoring technologies that are based on the analyses. Industry experience with currently available on-line blade monitoring technology is included.

Steam Turbine Bolting Maintenance Guide Report 1013341


New Turbine-Generator Projects Delivered in 2007


Productivity Improvement Expert Reviews 2008Access to the Productivity Improvement Expert Reviews (PIER) web site for 2008 is limited to companies participating in this project. EPRI, its technical staff, and its expert consultants have developed this web site to provide critically evaluated information of direct value in improving the availability, efficiency, and profitability of fossil steam power plants.

Over the last 10 years, this site has become a valuable resource to generating companies by summarizing successful applications that have already proved to be of significant value to other operating units. Hundreds of critically assessed case studies are documented in the site’s pages, and this has allowed others to duplicate these successes. Additionally, the site tracks creative new ideas that are very close to broad power plant use. These current items of interest alert readers to technology on the brink of commercial application.

In critically evaluating and discussing these new advances, we look primarily backward rather than forward. This approach was the basis behind what became EPRI’s Productivity Improvement Handbook. All printed copies of the first three editions of EPRI’s Productivity Improvement Handbook for Fossil Steam Power Plants (TR-11217, TR-114910, and 1006315) quickly sold out. The contents of the third edition can be accessed instantly on this site.

In addition to the web site, hardcover annual summary reports of Productivity Improvement Case Studies are available and have found their way into operating power plants for quick reference by plant staff. Every year, members of the PIER group are able to request copies of these annual summaries for all their operating power plants, and members have found these hard copies to be a useful supplement to the web-based versions.

For more information, contact Tony Armor, EPRI Palo Alto, 650.855.2961.

Fifth EPRI Turbine-Generator Program Technology Transfer Workshop and Summer 2008 TGUG MeetingThe EPRI Turbine-Generator (TG) Program will hold its Fifth Technology Transfer Workshop and a summer Turbine-Generator Users Group (TGUG) meeting the week of August 11, 2008 in Concord, North Carolina (near Charlotte, North Carolina) at the Embassy Suites Convention Center.

The workshop will be conducted Monday and Tuesday, with three workshop tracks running in parallel. Track 1 will feature the presentations “Steam Turbine Design 101,” “Steam Turbine Performance 101,” “Steam Turbine Chemistry 101,” “Turbine Water Induction 101,” and “Turbine Life Cycle Management/Remaining Life 101.” Track 2 is the Conference on Generator Predictive Maintenance, Generator Stator Winding High-Potential Testing, and Generator DC High-Potential Ramp Testing. Track 3 will include presentations on the newly released Steam Turbine Bolting Maintenance Guide (1013341), Shutdown Protection of Steam Turbines Using Dehumidified Air (1014195), Steam Turbine Blade Failure Root Cause Analysis Guide (1014137), Inspection and Damage Assessment of Turbine Casing Cracks (1014138), and PM Basis Overview and Improved Steam Path Design Primer Guide (1014141).

The TGUG meeting will include presentations by General Electric, Siemens, Toshiba, Hitachi, Mitsubishi, and Alstom, as well as presentations on topics such as electrohydraulic control retrofits, Detroit Edison’s on-line monitoring program, and Electrobrás Termonuclear's overview of its TG program. On Thursday afternoon, the group will tour the nearby Pioneer Bearing Motor Company facilities and attend a dinner at the Lowe’s Motor Speedway hosted by Pioneer Bearing Motor Company.

Complete meeting details can be found on EPRI’s web site through the following address: http://guest.cvent.com/EVENTS/info/summary.aspx?e=9fe89618-724b-4828-8cb5-d28d0bffaaac.

For more information about the upcoming workshop or TGUG meeting, contact Alan Grunsky, 704.595.2056, [email protected].

Improving the Financial Risk of an Aging Turbine-Generator Fleet Often, economic issues cause power plant senior management to overlook critical technical issues because management simply does not understand them or because the business case has not been made properly. The objective of this project is to assemble pictorial and written material for a slide presentation to senior management (such as a manager of a nuclear fossil fuel plant—VP of Generation). The material, which will be available no later than December 31, 2008, should assist in educating utility management of the risks and economic/financial consequences of decisions relating to the operation and maintenance of their turbines and generators. The desired effect is for senior management to take into account turbine and generator technical issues when making economic decisions.



Steam Turbine Valve Actuator Condition Assessment Guide

In early 2008, work began to produce a guide on valve actuators which will complement the EPRI report Guidelines and Procedures for Turbine Valve Condition Assessments (1010211) published in 2005. The new report will provide detailed instruction on valve component inspection and assessment criteria during disassembly and specifications for proper valve reassembly clearances. Turbine Valve Actuator Condition Assessment will cover the hydraulic valve actuators for the turbine valves addressed in Guidelines and Procedures for Turbine Valve Condition Assessments.

The following steam turbine valve applications will be discussed in the report:

General Electric (GE) fossil valves: control, main •stop, reheat stop, and intercept valves

GE nuclear valves: control, stop, reheat stop, and intercept valves•

Siemens Westinghouse fossil valves: throttle, •governor, intercept, and reheat stop valves

Siemens Westinghouse nuclear valves: governor and throttle valves•

A technical advisory group (TAG) consisting of nuclear and fossil plant representatives was formed. The TAG members are as follows:

Bob Bjune, South Texas Project•

Tony Khalid, Exelon/Corporate•

Tom Kordick, Ameren/Corporate•

Mark Miller, Duke Energy/Catawba•

Jim Olson, Tennessee Valley Authority, Corporate•

Charlie Seitz, Exelon/Three Mile Island•

Vendors and manufacturers might be added to the group. The TAG will provide input and review of the report.

We plan to include the following sections in the technical report:

1. Introduction. The introduction will include a background, approach, and explanation of the organization of the report.

2. Glossary. The glossary will list the nomenclature, acronyms, and definitions used in the report.

3. Technical Description. It is expected that this section will include a general description of the mechanical/hydraulic and the electrohydraulic turbine control systems, with emphasis on the hydraulic actuator function for the steam turbine valves. The components of the hydraulic cylinder and actuator assembly for the turbine valves will be explained.

4. Inspection. It is expected that this section will include inspection criteria for GE and Siemens Westinghouse turbine valve actuators. Copies of data sheets for recording measurements and condition should be included, and the criteria for inspecting the actuators should be given.

5. Maintenance. The maintenance section will most likely include preventive and corrective maintenance tasks for GE and Siemens Westinghouse turbine valve actuators. Applicable procedures for disassembly, repair, and reassembly of the actuators should be included. This section is also likely to list any special tooling and safety considerations for working on valve actuators.

The development of the report began in April 2008, and a conference call with the TAG members occurred on May 15, 2008. A survey was sent in June 2008. Review of a first draft is planned for July 2008, with project completion scheduled for the end of this year.

For more information, contact Sharon Parker, 704.595.2164, [email protected].

A Sample Turbine Valve Hydraulic Cylinder Dimension Chart


Valve Metallurgy Guides for U.S. and International Turbine Units

The EPRI report Guidelines and Procedures for Turbine Valve Condition Assessments (1010211) was published in 2005. The U.S. and international valve metallurgy guides (in development) will complement report 1010211 and include alternative materials used on the steam turbine valves. Tennessee Valley Authority (TVA) fossil plants have had success in using different materials for their valve components, and this information could be included in the report.

Another steam turbine valve project being planned by the EPRI Fossil Materials and Repair Program (P87) was to cover the metallurgical aspect of the turbine valve materials. This project was part of a larger effort to cover the metallurgical data for the steam turbine valves, shells/casings, blades, and stationary components for U.S. and international members.

It was decided to develop one comprehensive report that would cover the metallurgical aspects of the steam turbine valve components, including the use of alternative materials, for U.S. members and another report for international members. These reports will be funded by members of EPRI programs65/NSTI and 87.

The steam turbine valves used in the United States consist of the General Electric-manufactured and Siemens Westinghouse-manufactured valves used in fossil and nuclear plants. The international turbine manufacturers include Alstom, Hitachi, Mitsubishi, Toshiba, Siemens, and Allis Chalmers.

The turbine valves to be included in the reports are the following:

Main stop/governor •

Control/throttle•

Reheat stop•

Metallurgy: microstructure, heat •treatment, and coatings

Damage mechanisms•

Life assessment•

Repairs: welding,• coatings, and heat treatment

It will be necessary to conduct extensive research into the valve materials used on the U.S. and international steam turbine valve components. A survey on valve materials will be sent to fossil and nuclear plants, manufacturers, and other valve part suppliers.

We plan to include the following sections and content in the report:

1. Introduction: background, overview of report content, glossary,

Intercept/combined reheat-intercept valves•

The steam valve components to be covered in the reports include the following:

Bushings•

Main and bypass valve disks•

Pressure seal heads•

Seats•

Stems•

The metallurgical topics to be covered for each of the components are the following:

The alloy standards/materials used •by different manufacturers, to include alternative materials

Chemical composition•

Physical properties•

Mechanical properties: yield •strength, tensile strength, hardness, fracture appearance transition temperature, and creep rupture

Wear Resistance Versus Hardness of Turbine Valve Materials (Courtesy of TVA)

continued on page 20


Additions to the Turbine-Generator Preventive Maintenance Database The Preventive Maintenance Basis Database (PMBD) serves the utility maintenance community as an essential reference for maintenance strategy task selection on common major components. The PMBD Version 2.0 software (1014971) is the most comprehensive effort undertaken to date to establish credible preventive maintenance (PM) recommendations and their supporting basis. The software’s embedded functions allow in-depth analysis in many equipment-related areas and in management of PM tasks.

The following new turbine-generator components have been added to the PMBD:

Component Name Date Added Revision #

Main turbine gland steam system with attemperator 7/1/2008 0

Main turbine gland steam system without attemperator 7/1/2008 0

Main turbine lube oil ac auxiliary startup oil pump and motor 7/1/2008 0

Main turbine lube oil bearing lift pump and motor 7/1/2008 0

Main turbine lube oil reservoir with booster pump 7/1/2008 0

Main turbine lube oil reservoir with ejectors 7/1/2008 0

The PMBD Version 2.0 software is now available to order through the EPRI Customer Assistance Center, 1.800.313.3774 or 650.855.2121 or [email protected].

For more information, contact Tiffani Teachey, 704.595.2247, [email protected].

Evaluation of Electrohydraulic Control Fluid Alternative fire-resistant hydraulic fluids have been proposed for use in power plant turbine electrohydraulic control (EHC) systems. Products based on polyol esters (POEs) (Quintolubric® fluids) and polyalkylene glycols (EcoSafe®) have been promoted as alternatives. However, the use or potential use of these alternative fluids has created some technical concerns. According to some manufacturers, the advantages of these alternative fluids include lower fluid and disposal costs, better system performance, and fewer health, safety, and environmental concerns. In order to be able to make informed and objective decisions, utility personnel are working with EPRI to perform a comparative evaluation of these alternative products and the more widely used phosphate-ester fluids.

Fluids proposed for evaluation include EcoSafe EHC (polyalkyleneglycol), Quintolubric (POEs), Griflube Biosyn® (a vegetable ester), Fyrquel® EHC (a phosphate ester), and Reolube® Turbofluid 46XC (a phosphate ester).

The utility participants of the technical advisory group have given EPRI permission to begin testing as soon as possible. The lab chosen for the work is Britain’s Health and Safety Laboratory. The following tests are being coordinated with the laboratory, and the target dates for testing fall in July and August 2008:

– Spray ignition (International Organization for Standardization [ISO] Draft International Standard [DIS] 15029-2)•

– Manifold ignition test (ISO 20823)•

– Soaked cube test•

– Wick flame resistance (ISO 14935)•

For additional information on this effort, contact Jim Sharkey, 704.595.2057, [email protected].


Steam Turbine Bolting Maintenance Guide

Work began in 2006 to develop a maintenance/metallurgy guide for steam turbine bolting.

Members of the Turbine-Generator Program have increasing concerns for high-temperature bolting in the utility industry. With the aging of steam turbines, replacement of bolting in high-temperature applications has occurred and will continue to occur as the number of thermal cycles on the bolting continues to grow. It is important to know the condition of the existing bolting and to anticipate the replacement of bolting that does not meet the criteria for continued service.

Turbine joints are normally designed to be taken apart during overhauls at 30,000 operating hours, fixed intervals with no re-tightening between overhauls. It is then assumed that the joints are reassembled using the same bolts and that up to six re-tightenings might be required during the life of a turbine. The creep relaxation of a bolt that is reused in this way must continue to meet the design requirement so that the residual stress on the bolt does not cause the applied load on the flange to fall below the steam load.

Possibly, the most important material property for high-temperature bolts is the stress relaxation strength of the bolt material. The relaxation strength is usually taken as the relaxed stress after a fixed time, nominally 10,000–30,000 hours, as a function of an initial strain level of 0.2%. This is shown in Figure 1.

In practice, a joint might experience many more than six re-tightenings if the source of the operating periods is significantly less than 30,000 hours.

In an effort to address this relaxation and many other turbine-generator bolting issues, this new Steam Turbine Bolting Maintenance Guide (1016958) contains the following information:

1. Introduction. This section covers the background and report structure and includes some summary remarks.

2. Glossary. There are 38 pages of terms and definitions.

3. Technical Description. This section includes general information on design, types of threads, bolt-tightening methods, and safety concerns.

4. Tooling and Procedures. This section describes tooling, disassembly procedures, inspection procedures, assembly procedures, and torquing assembly procedures.

5. Failure Modes. This section covers failure through the male threads, thread stripping, and other factors; damage mechanisms; and 12 case-study examples of failures.

6. Materials Selection. This section includes metallurgical information for chromium molybdenum ferritic steels, 12% chromium martensitic steels, age-hardenable steels, ASTM International A286 alloy, nickel-based alloys, and Refractalloy 26 materials.

7. Inspection, Assessment, and

Maintenance Planning. This section covers manufacturers’ recommendations, a life assessment approach, approaches to aid in selecting fasteners for destructive examination, inspection, and actions to take when a cracked fastener is found.

8. Appendices. The appendices include information on shaft coupling bolts, a maintenance procedure for tightening, a maintenance procedure for removal of broken or seized bolts or studs, metallurgical summaries, a summary of bolting information bulletins, procedures for tracking bolt operating hours and history, ultrasonic examination of studs and bolts from the bore surface, ultrasonic examination of studs and bolts from the end surface, resources,

Figure 1. Stress Relaxation



Looking Forward: Program 65 and NSTI

The projects undertaken by Program 65 (Steam Turbine-Generators and Balance-of-Plant) and the Nuclear Steam Turbine Initiative (NSTI) are a result of input from their respective advisory boards. In addition to planning for the immediate future, the advisory boards guide the development of the program in the out-years. The following is a list of suggested projects tentatively scheduled for delivery in 2009–2010 by Program 65 and NSTI.

Projects Planned for 2009–2010 by Program 65 and NTSI

Title of Report or Activity Year of Delivery Project Manager

11th Steam Turbine-Generator Workshop and Vendor Exposition 2009 Paul Zayicek

Demonstration of Laser Cleaning on Steam Path Components 2009 Sharon Parker

Development of EPRI Integrated Stress Corrosion Cracking and Corrosion Fatigue Damage Life Prediction Code 2009

EHC Fluid FC3 Monitor Study Demo 2009 Jim Sharkey

Fatigue Sensor Reference Specimens 2009 Paul Zayicek

Flowpath Analysis for Steam Turbines CBT Module 2009 Gary Golden

Foam Cleaning of Valve Internals to Remove Oxide Buildup 2009 Sharon Parker

Implantation of Cracks in Blade Attachment Mockups 2009 Paul Zayicek

Inspection Criteria for Generator Rotors Subjected to Abnormal Negative Sequence Current Software 2009 Jan Stein

International Update to Metallurgical Guide for Turbine Rotors and Disks 2009 John Shingledecker

International Valve Metallurgy Guide 2009 Sharon Parker

Mitigating Actions During Major Turbine-Generator Events 2009 Gary Golden

Non-Intrusive Methods to Verify NERC Standards 2009 Jan Stein

Steam Deposit Effect on Thermal Performance 2009 Gary Golden

Turbine-Generator Auxiliary System Maintenance Guides, Volume 5 2009 Alan Grunsky

Blade Vibration Monitoring 2009–2010 Paul Zayicek

Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance and Overhauls 2009–2010 Alan Grunsky

International Turbine Valve Condition Assessment 2009–2010 Sharon Parker

Low-Pressure Rim Life CBT Module 2009–2010

Low-Pressure Rim Life Software 2009–2010 Paul Zayicek

Maintenance Management of Electronic Components 2009–2010 Sharon Parker

SAFER-PC 2009–2010 Paul Zayicek

SAFER-PC CBT Module 2009–2010 Paul Zayicek

Turbine-Generator Preventive Maintenance Database Module Additions 2009–2010 Tiffani Teachey

Turbine Valve Actuator Condition Assessment for International Steam Valves 2009–2010 Sharon Parker

Integrating Generator On-Line Monitors 2010 Jan Stein

Sixth Technology Transfer Workshop 2010 Paul Zayicek


Stress Corrosion Cracking and Corrosion Fatigue Workshop to Be HeldEPRI will hold a stress corrosion cracking (SCC) and corrosion fatigue (CF) workshop October 1–3, 2008, at the Gaylord Opryland Hotel in Nashville, Tennessee. This workshop, the focus of which will be mitigation strategies, will encompass past experiences and the SCC/CF that plants are currently dealing with. Also to be discussed is low-pressure turbine disk rim life issues and the associated EPRI computer program. There will be a roundtable to discuss issues brought by attendees; attendees should e-mail roundtable topics prior to the workshop to streamline the process of creating the roundtable agenda and to allow more time for discussion. Additional agenda items can be added as more abstracts are received.

All technical correspondence regarding this workshop should be sent to Gary Golden, [email protected].

2009 European TGUG Workshop and Meeting

2008 Boiler and Reactor Feed Pump Turbine (B/RFPT) WorkshopProgram 65 and NSTI will hold a B/RFPT Workshop November 18th, 19th, and half day on the 20th at the Nashville Marriot Hotel at Vanderbilt University.

Those that should attend are Turbine Engineers, System Engineers, Maintenance Scheduling and Procurement Staff and those that deal with the boiler or reactor feed pump turbines.

This workshop is for both the fossil and nuclear industries and will address the industries growing B/RFPT concerns. The topics will include: Valves and Controls, Controls Upgrades, Rotor and Cylinder end of life, Purchasing and Replacement, Operation and Lay-up, Impact of steam path upgrades, Couplings (various designs, capabilities, and alignment processes), Auxiliary Systems (lube oil, steam seals, etc.), TSI, Balancing, Coatings and finally a discussion of generators and maintenance lessons learned.

Please come prepared to discuss with the other attendees your specific experiences relative to the previously mentioned topics. This activity will occur during a roundtable discussion period of the workshop.

To participate as a presenter, contact Gary Golden, 865.218.8111, [email protected].

The EPRI Turbine Generator User Group (TGUG) is currently in the planning stages of conducting a workshop and vendor exposition for European utilities in Madrid, Spain, from June 8th-12th, 2009. The Madrid hotel has yet to be determined. Both EPRI member and non-member European nuclear and fossil utility representatives are encouraged to attend, and U.S./North American TGUG members are also invited to participate. Updates will be available as soon as more details are finalized.

For additional information, contact Alan Grunsky, [email protected]


Turbine-Generator Supplemental Projects

Experimental Measurement of a Fatigued Section of a Turbine Blade

Demonstration of Fatigue Sensor Technology for Steam Turbine Blades

Blade failures are a common reason for unplanned outages related to steam turbines. The damage associated with failure of large low-pressure blades can be extensive and costly. Many nondestructive inspection methods and technologies exist to provide detection of cracking that has already occurred. However, standard nondestructive

inspection technologies are not able to predict cracking before it occurs. Fatigue sensor technology has been qualitatively proven as a technology for identification of fatigue damage accumulation and life consumption. This EPRI supplemental project provides quantitative benchmarking of this technology using fatigue test specimens of Jethete material to provide a detailed quantification of the fatigue damage measurements and its uncertainty using existing technology. This quantitative benchmarking will provide an important basis for interpretation of the results of field tests on turbine blades. Uniaxial and flexural fatigue specimens have been subjected to interrupted testing and periodic measurement using fatigue sensor technology to develop β parameters for determination of accumulated fatigue damage.

For more information on this activity, contact Paul Zayicek, 704.595.2154, [email protected].

Detection of Shaft Keyway Cracking Under the Coupling on General Electric Co. Generator Rotors

Generator shaft keyway cracking has been experienced in two nuclear four-pole generators. The cracking initiated in the inboard side of the shaft keyway as a result of fretting fatigue. The resulting crack propagated toward the journal area, apparently driven by torsional loading based on the crack orientation. Originally, the original equipment manufacturer (OEM) did not have a nondestructive inspection technique for detection of shaft keyway cracking under the coupling. The OEM suggested a liquid penetrant and visual inspection of the shaft area adjacent to the keyway for detection of cracks once they have propagated from under the coupling. The weakness of this approach is that it identifies cracking late in the damage process, leaving the utility with an emergency repair scenario. Detection of cracking in the early stages of propagation would allow utilities an opportunity to return to service, monitor growth, and effectively plan and prepare for a subsequent repair outage.

The EPRI supplemental project “Detection of Shaft Keyway Cracking Under the Coupling on General Electric Co. Generator Rotors” includes development of a linear phased array ultrasonic inspection technique for the detection of cracking in the generator rotor shaft keyway area under the shrunk-on coupling. This technique can be used without disassembling the coupling, thereby enabling timely

Torsional Cracking in the Shaft Keyway of a Four-Pole Nuclear Generator Rotor



Turbine-Generator Supplemental Projects


inspection with minimal impact on unit availability. Linear phased array ultrasonic technology allows steering of the ultrasonic energy by phasing of the individual probe elements. Because of this feature, it is feasible to inspect the inboard portion of the shaft keyway by conducting the inspection from the accessible shaft surface adjacent to the inboard side of the shaft keyway. Mathematical modeling efforts of this inspection application using EPRI technology indicate

that this approach is viable. Verification of the modeling work will be completed on a full-scale mockup using a variety of manmade targets. The flaw detection and sizing capabilities of the developed technique will also be evaluated on the mockup. Retired generator rotor segments are being used for the full-size mockup.

For additional information on this activity, contact Paul Zayicek, 704.595.2154, [email protected].

and bolts from the bore surface, ultrasonic examination of studs and bolts from the end surface, resources, a questionnaire to utilities, turbine valve bolting information, and bolting procurement guidelines.

The report was made available through the EPRI web site on December 31, 2007, and hardcopy reports were mailed to members in March 2008. After the report’s publication, a purchase bid specification for bolting was developed and added to the EPRI report Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections, Volume 4: Turbine-Generator Component Procurement Specifications (1016346), published March 2008. This bid specification was also added as Appendix L to the Steam Turbine Bolting Maintenance Guide (1013341) to produce the Steam Turbine Bolting Maintenance Guide Revision 1 (1016958).

If you have any questions on Steam Turbine Bolting Maintenance Guide Revision 1, contact Tom Alley, 704.595.2066, [email protected].

Steam Turbine Bolting Maintenance Guide


2. Valve Bushing Materials: alloy standards (including alternative materials), chemical composition, physical properties, mechanical properties, metallurgy, damage mechanisms, life assessment, repairs

3. Main Valve and Bypass Valve Disk Materials: alloy standards (including alternative materials), chemical composition, physical properties, mechanical properties, metallurgy, damage mechanisms, life assessment, repairs

4. Valve Seat Materials: alloy standards (including alternative materials), chemical composition, physical properties, mechanical properties, metallurgy, damage mechanisms, life assessment, repairs

5. Valve Stem Materials: alloy standards (including alternative materials), chemical composition, physical properties, mechanical properties, metallurgy, damage mechanisms, life assessment, repairs

6. Pressure Seal Head Materials: alloy standards (including alternative materials), chemical composition, physical properties, mechanical properties, metallurgy, damage mechanisms, life assessment, repairs

7. References

8. Appendices

Work began on the U.S. report in April 2008, with a first draft expected October 2008. The final report on U.S. valves should be completed in the first quarter of 2009.

For the international report, vendors are being solicited for development. It is anticipated that the international report will be completed at the end of 2009.

For more information, contact Sharon Parker, 704.595.2164, [email protected].

Valve Metallurgy Guides for U.S. and International Turbine Units



Determination of β Parameter for 12% Cr Turbine Blades Using Fatigue Sensor TechnologyThe EPRI supplemental project “Demonstration of Fatigue Sensor Technology for Steam Turbine Blades” explored emerging technology for nondestructively measuring the fatigue life consumption of turbine blades using ultrasonic waves. Application of fatigue sensor technology for in-service turbine blades can reduce the risk of in-service failures, make measurements of consumed fatigue life without removing blades from the rotor, and optimize timing for blade row replacement. The original supplemental project was based on measurement of Jethete blades to establish β parameters for subsequent field deployment. This project, an extension of previous work, will determine β parameters for the 12% Cr family of turbine blades and establish consumed fatigue life for subsequent field deployment.


Axial Entry Disk Blade Attachment NDE Performance DemonstrationThe estimation of remaining rotor life and the rotor repair or replacement strategies associated with disk blade attachment cracking on low-pressure (LP) steam turbine rotors consumes significant resources. Reliable ultrasonic inspection methods for the detection of stress corrosion cracking in the steam turbine disk blade attachment area are essential to the rotor run/repair/replace decision-making process. EPRI will conduct an axial entry blade attachment performance nondestructive examination (NDE) for commercial vendors that offer this inspection service. The performance demonstration will be based on detection of manmade targets in two retired-from-service Westinghouse LP rotor disks with axial entry disk blade attachment geometry. EPRI previously conducted a performance demonstration activity for flaw sizing and detection of targets in tangential entry disk blade attachment geometries: the results were published in the report Phased Array Performance Demonstration for Blade Attachment Inspection (1011677).

The axial entry disk blade attachment NDE performance demonstration is a natural extension of the previous demonstration activity. The project is divided into two segments. In Year 1, we will develop mockups and a demonstration protocol, solicit commercial inspection vendors to participate, and facilitate vendor data acquisition. In Year 2, we will analyze vendor data and produce the final report, summarizing test methodology and the inspection performance results.


A Cracked Axial Entry Disk Blade Attachment


Guide for Inspection of Low-Pressure Turbine BladesPeriodic inspection of low-pressure (LP) turbine blades is essential for early detection of cracking or other damage that will adversely affect blade performance or cause damage to the unit as a result of blade failure. Comprehensive inspection of the turbine blade includes the airfoil, blade root, tie wires, and tenons, as appropriate, for a variety of blade designs. Multiple nondestructive examination (NDE) techniques are available for the detection and sizing of blade flaws. NDE techniques include visual inspection, ultrasonic inspection, magnetic particle inspection, eddy current inspection, and liquid penetrant inspection. Emerging NDE techniques, such as fatigue sensor technology, are also being evaluated for this inspection application.

The complex geometries of LP turbine blades can present a challenge when developing ultrasonic inspection strategies, especially for the blade root. Commercial modeling software programs allow for assessment of ultrasonic energy propagation and inspection coverage, resulting in improved inspection efficiency and more accurate interpretation of the inspection results.

The deliverable from this project will be an EPRI report providing guidance for the inspection of LP turbine blades.

For more information on this activity, contact Paul Zayicek, 704.595.2154, [email protected] Fracture of Blade Root in Service

Optimization of Fatigue Sensor Measurement for Curved Blade SurfacesFatigue sensor technology is a nondestructive examination (NDE) method for the determination of life consumption for components at risk of fatigue. Microstructural damage in metals caused by fatigue are usually related to the accumulation of various types of dislocation structures. Dislocation dipole densities increase as the fatigue damage accumulates, until a microcrack is initiated. The correlation between low-level ultrasonic sound signature and the fatigue life consumed is based on spectral analysis of the sound energy from these dislocations in the metal. Fatigue sensor technology can identify these low-level ultrasonic sound signatures and help to determine the fatigue damage accumulated in steam turbine blades.

Existing fatigue sensor measurement technology is adequate for quantitative benchmarking using prepared fatigue specimens. However, opportunities exist for optimizing the fatigue sensor measurement process for turbine blade applications to address the effects of the curved blade airfoil and the surface roughness that will be encountered during in-service inspection. Several tasks have been considered; these include alternative probe configurations and wave modes, alternative coupling schemes, and alternative wave analysis schemes. The current strategy is to explore pulse-echo probes (single-measurement probes) as an alternative to the current pitch-catch arrangement (a two-probe configuration requiring access to both sides of the specimen to be measured). We will also explore electromagnetic acoustic transducer (EMAT) technology. EMAT generates and receives ultrasonic waves without the need to contact the material in which the acoustic waves are traveling. This removes the bond effects that are encountered with contact ultrasonic measurement technology.



Program Staff

Fossil and Nuclear Steam Turbine-Generator Program

Gary Golden Performance, Testing, B/RFPT 865.387.5309, [email protected]

Alan Grunsky Operations and Maintenance 704.595.2056, [email protected]

Sharon Parker Turbine Auxiliaries 704.595.2164, [email protected]

Linda Parrish Senior Administrative Assistant 704.595.2061, [email protected]

John Shingledecker Materials 704.595.2120, [email protected]

Jan Stein Electrical Equipment, Generators 650.855.2390, [email protected]

Paul Zayicek NDE, Condition Assessment 704.595.2154, [email protected]

2008 Meetings Date Location

Fifth Turbine-Generator Aug. 11–15, 2008 Concord, NC Technology Transfer Workshop Embassy Suites and Summer Turbine-Generator Users Group (TGUG) Meeting

NERC Interest Group Aug. 21–22, 2008 Detroit, MI DTE Headquarters

EMI Interest Group Sept. 10, 2008 Groveport, OH AEP’s John E. Dolan Engineering Laboratory

Stress Corrosion Cracking & Oct. 1–3, 2008 Nashville, TN Corrosion Fatigue Workshop Gaylord Opryland Hotel

Boiler/Reactor Feedpump Nov. 18–20, 2008 Nashville, TN Turbine Workshop Vanderbilt Marriott Hotel

2009 Meetings Date Location

Winter 2009 TGUG Workshop Jan. 19–23, 2009 Savannah, GA and Meeting with Vendor Fair Hyatt Regency

11th EPRI Steam Turbine Generator Aug. 10–11, 2009 TBD Workshop and Vendor Expo

Summer TGUG Meeting Aug. 12–14, 2008 TBD

Upcoming Events

Steam Turbine Blade Failure Root Cause Analysis GuideSteam Turbine Blade Failure Root Cause Analysis Guide (1014137) is a reference written for operators to plan and conduct an investigation into the most probable causes of a steam turbine blade (bucket) failure. The report provides both an overview and step-by-step approach to identifying the damage mechanisms most common to turbine blade failures. It also shows how damage mechanisms are related to the operating history prior to blade failure and how they are evaluated to establish their role as principal (root) causes versus secondary contributors.

The report, released in March 2008, is currently available.

For more information, contact Justin Thibault, 704.595.2103, [email protected].

Export Control Restrictions

Access to and use of EPRI Intellectual Property is granted with the

specific understanding and requirement that responsibility for ensur-

ing full compliance with all applicable U.S. and foreign export laws

and regulations is being undertaken by you and your company. This

includes an obligation to ensure that any individual receiving access

hereunder who is not a U.S. citizen or permanent U.S. resident is

permitted access under applicable U.S. and foreign export laws and

regulations. In the event you are uncertain whether you or your com-

pany may lawfully obtain access to this EPRI Intellectual Property, you

acknowledge that it is your obligation to consult with your company’s

legal counsel to determine whether this access is lawful. Although

EPRI may make available on a case-by-case basis an informal as-

sessment of the applicable U.S. export classification for specific EPRI

Intellectual Property, you and your company acknowledge that this

assessment is solely for informational purposes and not for reliance

purposes. You and your company acknowledge that it is still the ob-

ligation of you and your company to make your own assessment

of the applicable U.S. export classification and ensure compliance

accordingly. You and your company understand and acknowledge

your obligations to make a prompt report to EPRI and the appropriate

authorities regarding any access to or use of EPRI Intellectual Prop-

erty hereunder that may be in violation of applicable U.S. or foreign

export laws or regulations.

1016976 July 2008

Electric Power Research Institute 3420 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 USA 800.313.3774 • 650.855.2121 • [email protected] • www.epri.com

© 2008 Electric Power Research Institute (EPRI), Inc. All rights reserved. Electric Power Research Institute, EPRI, and TOGETHER...SHAPING THE FUTURE OF ELECTRICITY are registered service marks of the Electric Power Research Institute.

Printed on recycled paper in the United States of America

The Electric Power Research Institute, Inc.(EPRI, www.epri.com) conducts research and developmentfor the global electricity sector. An independent, nonprofitorganization, EPRI brings together experts from academia andindustry as well as its own scientists and engineers to helpaddress challenges in electricity generation, delivery and use,including health, safety and the environment. EPRI also pro-vides technology, policy and economic analyses to drive long-range research and development planning, and supportsresearch in emerging technologies. EPRI’s members representmore than 90 percent of the electricity generated and deliveredin the United States, and international participation extends to40 countries. EPRI’s principal offices and laboratories are locat-ed in Palo Alto, California; Charlotte, North Carolina;Knoxville, Tennessee; and Lenox, Massachusetts.

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