EPRI-Steam Turbine Generator Notes

July 2008

Contents Upgrade to Guide for On-Line Testing and Monitoring of Turbine Generators .................... ....................................... ...................................... ...................................... ........................ ..... 2 Shutdown Protection Protection of Steam Turbines Using Dehumidified Dehumidified Air ............. 3 Advanced Labyrinth Seal Proj Project ect ................................. .................................................... ..................... .. 3 Additions to Guidelines for Reducing the Time and Cost of TurbineGenerator Maintenance Overhauls and Inspections .......................... ............................ .. 4 EPRI Turbine-Generator Program Holds 2007 Steam Turbine-Generator Workshop/V Worksho p/Vendor endor Expo and Summer 2007 Users Group Meeting ....... 6 EPRI Turbine-Generator Users Group Holds Winter 2008 Workshop/ Meeting in San S an Diego .......................................... .............................................................. ......................... ..... 6 Tracking Laser Coordinate Measurement System Application Project Completed ................... ...................................... ....................................... ....................................... ........................ ..... 7 Boiler/Reactor Boiler /Reactor Feedpump Turbine Rotor End-of-Life Proj Project ect .................... 7 The Effect Ef fect of Organi Organics/ cs/Amines Amines on Tur Turbine bine Performance ..................... ....................... .. 7 Turbine and Generator Compliance to NERC Standards Interest Group Workshop Worksho p ................. .................................... ....................................... ....................................... ........................... ........ 8 Evaluation of Low-Pressure Turbine Stator Coatings to Reduce Erosion on Rotor Blades .................................................... ....................................................................... ........................ ..... 8 Reference Book for Steam Tur Turbine-Generator bine-Generator Products ......................... ......................... 8 Generator High-Voltage High-Voltage Bushin Bushing g Installati Installation on Guide.................. .............................. ............ 9 Non-Intrusive Methods to Validate NERC Standards: Steam Turbine Frequency Response (MOD-027)................ (MOD-027)................................... ................................... ................ 10 Inspection Criteria for Generator Rotors Subjected to Abnormal Negative Sequence Curr Current ent ....................... .......................................... ................................... ................ 10 New Turbine-Generator Projects Delivered in 2007 ...........................11 Fifth EPRI Turbine-Generator Program Technology Transfer Workshop and Summer 2008 TGUG Meeting ................................................12 Productivity Productiv ity Improv Improvement ement Expert Review Reviewss 2008 .................................1 .................................12 2 Improving the Financial Risk of an Aging Turbine-Generator Fleet ..........12 Steam Turbine Valve Actuator Condition Assessment Guide .................13 Valve Metallurgy Guides for U.S. and International Turbine Units...........14 Additions to the Turbine-Generator Preventive Maintenance Database ................... ...................................... ...................................... ...................................... ..........................1 .......15 5 Evaluation of Electrohydraulic Control Fluid ......... ................. ................. .................. ............15 ...15 Steam Turbine Bolting Maintenance Guide .......................................16 Looking Forward: Program 65 and NSTI ..........................................17 Stress Corrosion Cracking and Corrosion Fatigue Workshop to Be Held ................. .................................... ...................................... ...................................... ..............................1 ...........18 8 2009 European TGUG Workshop and Meeting ...............................18 2008 Boiler and Reactor Feed Pump Turbine (B/RFPT) Workshop ........18 Turbine-Generator Turb ine-Generator Supplemental Proj Projects ects .................. ..................................... ........................1 .....19 9 Axial Entry Disk Blade Attachment NDE Performance Demonstration .....21 Determination of β Parameter for 12% Cr Turbine Blades Using Fatigue Sensor Techno Technology logy ................. .................................... ....................................... ........................2 ....21 1 Guide for Inspection of Low-Pressur Low-Pressuree Turbine Blades ................... .......................... ....... 22 Optimization of Fatigue Sensor Measurement for Curved Blade Surfaces ................. .................................... ...................................... ....................................... ............................. ......... 22 Upcoming Events .................. ..................................... ...................................... ................................... ................ 23 Program Prog ram Staff ................. .................................... ...................................... ...................................... ...................... ... 23 Steam Turbine Blade Failure Failure Root Cause Analysis Guide .................... .................... 23

Fossil and Nuclear Steam Turbine-Generators

Mechanical Hydraulic Control System Maintenance Guide in Progress Turbine mechanical hydraulic control (MHC) systems are still in wide use today on units that ar e 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 maintai ning and troubleshooting MHC systems. In response to to these issues, early this year, work began on completion of an MHC system maintenance guide. The report will be completed by March 2009.

Typical Cam Shaft/Roller MHC System Controls

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. continued on page 2

Mechanical Hydraulic Control System Maintenance Guide in Progress continued from page 1

Because just six nuclear units in the world still employ these types of

2. Inspection. This section will include inspection criteria for

turbine control systems (as opposed to the more modern electrohydrau lic

the GE and Westinghouse turbine control devices. Copies of

control systems), systems), the initial report w ill contain only limited in formation

data sheets used to record measurements and condition will

about nuclear units. As the project progresses, we will investigate the

be included. The criteria for inspecting the controls system

possibility of adding more nuclear MHC information to the final report.

will be given. Included will be common adjustments, such as

Including nuclear information greatly expands the original scope of the

setting (measuring) regulation, CV crack point, and overspeed

project.

set points. 3. Maintenance. The maintenance section will include

The current outline of most of the information to be included in the

preventive and corrective maintenance tasks for the GE and

report is as follows:

Westinghouse turbine control devices. Applicable procedures

1. Technical Description. This section will include a general

for disassembly disa ssembly,, repair, and reassembly of the components

description of the GE, Westinghouse 300#, and Westinghouse

will be included, and any special tooling will be listed. Any

150# MHC systems, with an emphasis on front standard

safety considerations for working on the control devices will

(pedestal) components, lube oil tank components specifically

be given. Included will be references to partial upgrades or

related to control functions (but excluding the lube oil system

modifications that have typically been performed.

itself), valve hydraulic cabinet components, and mid-standard

Post-Maintenance -Maintenance Commissioning. This section will 4. Post

components. The components included are as follows:

describe activities required to set up and perform pre-

a. For GE units: speed/load changer, load limiter, speed

operational checks on the controls system prior to starting the

governor, secondary speed relay, acceleration rel ay,

unit following a major outage, whether or not major work was

secondary pilot valve, linkages, cutout governor, initial

performed on the controls system.

pressure regulator, stop valve bypass valve controller,

5. Troubleshooting. This section will include a guide to

intercept valve (IV) speed governor, IV dashpot breakdown

troubleshooting operational problems. Common operational

link, overspeed trip, backup overspeed trip, main stop

problems, symptoms, causes, and solutions will be included.

valve/reheat stop valve trip devices, trip anticipator, test

For more information on this project, contact Alan Grunsky, 704.595.2056, 704.5 95.2056, [email protected] [email protected]. m.

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 Westinghouse (150# (150# and 300#) units: speed/load

valve (CV) servomotor, IV servomotor, multiple orifices

Upgrade to Guide for On-Line Testing and Monitoring of Turbine Generators

and check valve, and control rotor

The EPRI report Guide for On-Line Testing and Monitoring

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

of Turbine Generators (1006861), released in 2002, provides information about failure mechanisms for all major generator

Steam Turbin urbinee-Generator Generator Notes

manufacturers and identifies the most appropriate on-line detection systems.

Is published by the Elect ric Power Research I nstitute's (EPRI's)

The objectives of the project are to add guidance for off-line

Fossil and Nuclear Steam Turbine-Generator Program

testing and to refine the assignment of appropriate failure 1300 W.T. Harris Blvd., Charlotte, NC 28262, fax 704.595.2867 NSTI/Program 65 Contact: Alan Grunsky, 704.595.2056, [email protected]

Steam Turbine-Generator Notes

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].

2

July 2008

Shutdown Protection of Steam Turbines Using Dehumidified 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 existin g units alike. Consistent with EPRI’s guidi ng principles for shutdown protection, the comprehensive approach considers shutdown protection requi rements 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 Dehumidification 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 a nalysis methodology will be tried and repor ted. 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].


3

July 2008

Additions to Guidelines for Reducing the Time and Cost of TurbineGenerator Maintenance Overhauls and Inspections Over a period of more than seven years, the

and balancing, pre-startup checks,

stator, generator excitation system,

EPRI

and post-outage activities. Volume 1

turbine insulation, complete turbine

accumulated information that can assist

also contains, as appendices, a sample

outage services, and turbine bolting.

utilities/plants with TG maintenance. This

TG outage report, more than 150

Volume 5: Turbine Directory and Database

information is contained in the seven-volume

sample data sheets, and a TG FME

– The fifth volume presents a directory

set Guidelines for Reducing the Time and Cost

program/process guidance document.

Turbine-Generator

(TG)

Program

and database of large (>75 megawatts

of Turbine-Generator Maintenance Overhauls .

Volume 2: Repair Procedures

electric) turbines that operate with

In 2007, new material was added to Volume

– The second volume provides detailed

last-stage buckets of 23 inches (58

2, Repair Procedures, and Volume 4, Blade and

repair procedures to guide the

centimeters) or longer. The list now

Rotor Procurement Specifications .

pre-bid, inspection, disassembly,

contains U.S. and international

Any company that is currently in a multi-year

and repair of critical turbine and

units. Presented in this database are

(at least three years) contractua l commitment to

generator components. Examples of

original turbine manufacturers and

Program 65 can order the entire seven volumes

these procedures are bearing spin-

their equipment designations and

as a four-CD set. If you meet this requ irement,

casting/repuddling, diaphragm and

plant/unit status (as of 2001). To

you can order the 2007 EPR I product 1014134.

nozzle block partition repair, blade

further assist users of this directory in

This four-CD set is also available to Nuclear

tenon repair, hydrogen seal repair,

identifying operators who might have

Steam Turbine Initiative funders.

horizontal joint casing repair, main

units that share common features, the

steam stop valve cap repair, generator

data are sorted and presented by L-0

hydrogen seal inspection/repair,

bucket length and the manufacturer’s

alterrex inspection/maintenance,

design designation (where this could

inspection/testing/re-wedging

be identified). Included are plants/

generator stators, and collector ring/

units that have been shut down and

brush rigging maintenance.

plants/units that have been cancelled.

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 sevenvolume 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

Volume 3: Balancing and Alignment Specifications

A table listing North American and

– The third volume contains

major component replacements/

international units that have completed modifications is also included.

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

•

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

maintenance activities that are

specifications for the procurement

turbine blades/disks. This information

usually associated with an outage:

of turbine buckets, to include blade

aids turbine maintenance personnel

TG condition assessment (in-serv ice),

frequency testing and tuning guidance,

in assessing solid particle erosion,

pre-outage planning and bidding, unit

high-pressure/intermediate-pressure/

high-cycle fatigue (HCF), low-cycle

shutdown procedures, disassembly

low-pressure (HP/IP/LP) fossil rotors,

fatigue (LCF), and creep rupture

and recording clearances, foreign

HP/LP nuclear rotors, generator

damage to HP and IP blading.

material exclusion (FME) process

rotor rewind, a new generator rotor,

information, TG condition assessment

generator stator rewind, new generator

continued on page 5

(off-line), oil flushing, rotor alignment


4

July 2008

Additions to Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections continued from page 4

•

CD 3

– Specifications for purchasing new

turbine bolting as a new Section

Volume 7: LP Blade/Disk Design and Inspection Specifications

11 and an example of a turbine bolting procurement RFQ

– The seventh volume presents blade/

disk design audit and inspection

•

– A new Appendix K, to supplement

procedures for LP blades/disks.

the existing purchase specifications

This information aids turbine

for turbine blading that appear

maintenance personnel in assessing

in Section 1, titled “Guidelines

stress corrosion cracking (SCC), HCF,

for Blade Frequency Testing

and LCF damage to LP blading.

and Tuning Acceptance”

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.

•

•

•

•

•

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 Turbineto discuss potential additions. The following Generator Maintenance Overhauls information will be added to the Guidelines and Inspections, contact Alan Grunsky, 704.595.2056, [email protected]. You can CD set in 2008 based on budget constraints also ask Alan about becoming a multi-year and availability of the information: funder of Program 65 or about your company’s Best practices for hydrogen seal current participation level. installation and long-term preventive maintenance for hydrogen seals The TAG met again by web cast in March 2008

•

•

Best practices for optimizing TG rotor centerline alignment

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 20 07: 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

Recutting a Worn-Out Helical Groove


5

July 2008

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 Ex position

•

Generator upgrades and maintenance

•

Steam turbine R&D

•

Generator rotor turns and grid disturbance detection

•

Use of monitoring data

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,

Summer Turbine-Generator Users Group Meeting

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 summer 2007 Turbine-Generator Users Group (TGUG) meeting

the three-day workshop and 48 vendors participati ng in the vendor expo

was held August 16–17 in conjunction with the 10th Steam Turbine-

that was held Monday and Tuesday evenings.

Generator Workshop at the same hotel in Phoenix, Arizona. On Thursday evening, an additional session was conducted. This was the

On Monday morning, two pre-workshop/vendor expo workshops were

Generator Clip-to-Strand TGUG working group, led by Tom Phelan of

conducted. One was a tutorial on boiler/reactor feedpump turbine

Constellation Energy; the session had approximately 25 attendees.

design, and the topic of the second was generator core testing.

All information shared during the week’s meeting/workshop can

Multiple sessions were conducted in parallel over the three days, with

be viewed on the EPRI web site through the following address:

the following topics discussed: Steam turbines

http://www.epri.com/tgug/pastmeetings.html.

•

•

Nondestructive evaluation for TGs

•

Generator on-line monitoring and condition assessment

•

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

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

EPRI Turbine-Generator Users Group Holds Winter 2008 Workshop/ Meeting in San Diego The 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/Regu lations/Issues f rom the Turbine-Generator Perspective.” On Tuesday, two workshop sessions were conducted; the title of the turbine session was “TG Upgrades: Pla nning, Procurement, and Installat ion,” 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].


6

July 2008

Tracking Laser Coordinate Measurement System Application Project Completed 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].

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

Boiler/Reactor Feedpump Turbine Rotor End-of-Life Project

The Effect of Organics/Amines on Turbine Performance

In an effort to address a rising number of problems with the

As the demand for power reaches critical points and the cost of

power industry’s boiler/reactor feedpump turbines (B/RFPTs),

electricity production rises, so does the need for better turbine

EPRI has initiated several activities aimed at helping our

efficiency. Program 65/NSTI is proceeding with the organics/

members solve these issues. In 2007, a survey was taken to

amines (O/As) project to investigate the increase in perf ormance

identify prevalent problems in the industry, and the results will

when O/As are injected into the steam path. EPRI will monitor

be augmented by another survey. Along with this effort, EPRI

the difference in nucleation of steam after O/As have been

is kicking off an industry B/RFPT rotor end-of-life project

injected into the steam path: specifically, the steam will pass

that will address the flow path problems that members are

through a converging/diverging nozzle and will be monitored

encountering today. We ask that you take time to participate in

for performance improvements. Results of this project will be

upcoming survey efforts or that you send this survey to someone

available March 2009.

within your utility who will.

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

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


7

July 2008

Turbine and Generator Compliance to NERC Standards Interest Group Workshop A 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 Capabilit y, PRC-019 Coordination of Generator Voltage Regulator Controls with Unit Capabilities a nd 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-anda-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].

Reference Book for Steam Turbine-Generator Products

Evaluation of Low-Pressure Turbine Stator Coatings to Reduce Erosion on Rotor Blades

Since its inception, the EPRI Steam Turbine-Generator Program has created a multitude of reports and other products. A

This supplemental project is investigating the potential benefits

compilation of more than 125 product summaries that describe

of stator surface coatings in reducing erosion damage produced

EPRI research performed over the past 20 years is contained

by water droplets. This investigative project, which is taking place

in the EPRI report Description of Past Research: EPRI Fossil and

at the University of Tennessee Space Institute, involves applying

Nuclear Steam Turbines and Generators—Volume 4 (1016900).

hydrophobic coatings to the stator surface in order to change the

The summaries are arranged by categories related to generators,

characteristics of the coarse water droplets discharged from the

steam turbines, software, Technology Innovation reports, and

stator trailing edge.

other related miscellaneous subject areas. Each product summary

The cascade sections have been constructed, and the wind tunnel

includes an abstract; a description of the report’s objective,

configuration is being put into place. A high-speed camera

approach, and results; and EPRI’s perspective. The report is a

captures the water droplet size coming off the trailing edge of the

useful references for EPRI-member organizations that are seeking

stator blades. For comparison, there is a baseline cascade section

past reports on specif ic topics of interest. EPRI updates this report

along with cascade sections with the hydrophobic coatings.

yearly to include new research reports and software.

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

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


8

July 2008

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 flan ge 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 t he 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

– Sealants

– Magnetic versus non-magnetic bolting

– A list of OEM technical information letters,

service bulletins, and notices

– Impact of lubricated versus unlubricated bolts •

– Gasket material selection versus bolt torque requirements

– Area preparation

– Terminal plate material versus bolt torque

– Work area egress

and bolt material considerations

– Rigging and handling the weights of the bushings, current

– The impact of sealants on gasket sealing

transformers, and neutral/isolated phase bus duct enclosures

– The impact of bushing flange and terminal plate surface

– Foreign material exclusion considerations

finish and preparation on gasket sealing characteristics

– Tools and tool staging

– Bolt engagement design considerations in the

– Proper handling of high-voltage bushings

flange-to-terminal-plate interface

during removal and installation

– Torque application methods (tooling)

– Electrical field testing of the replacement

– Bolt locking methods

bushing; high-potential (Hipot) testing

– Inspection requirements and testing before and after installation

– Mechanical (for example, pressure) field

– Handling to prevent corrosion or accidental cracks and breakage

testing of the replacement bushing

– Maintenance check intervals and installation

– The amount of contact required on the connection

– Proper bolting of the flexible links to isophase bus conductors •

between the bushing and generator lead

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

– Termination taping •

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

Replacement criteria and spares, including the following topics: – Inspection frequency and scope

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

– Replacement criteria

differences, and assembly/disassembly methods

– When to keep spares and how many to keep

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

Removal and installation, including the following topics:

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

– Recommendation for reinspection and bolt

– Porcelain versus alternative insulators

– Storage requirement (for example, vertical storage)

re-tightening intervals

– Refurbished bushings

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

– Leak-checking methods

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


9

July 2008

Non-Intrusive Methods to Validate NERC Standards: Steam Turbine Frequency Response (MOD-027) MOD-027 requires the generator operator to verify the generator

(for example, loss of a major generator that results in system frequency

unit frequency response (that is, the megawatt response of the unit to

deviations) that are automatically captured during ambient monitoring.

deviations in system frequency) for use in models for reliability studies.

The primary objective is to investigate and prove whether ambient

Each North American Electric Reliability Council (NERC) region

monitoring can be used to capture disturbance data and thus be used

must maintain procedures for the verification of frequency response, with automated software to fit the parameters of the turbine-governor including the following: The response time, to be modeled up to 30 seconds for steam units

model for large steam turbines.

•

•

•

The project includes the following tasks:

The verified manufacturer and type of turbine speed governor controls

1. Model and method development for large steam turbines 2. A staged test of a large steam turbine at a host utility

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

3. Ambient monitoring for system events at a host utility (for the same unit tested in Task 2)

In 2007, three utilities fu nded a supplemental project to derive generator,

4. A comparison of models developed by both methods

excitation system, and governor parameters from off-line and on-line

5. Presentation at the Generation Advisory Meeting

tests (see EPRI report 1015241, Power Plant Modeling and Parameter

6. Publication of the final report

Derivation for Power System Studies ). The Power Plant Parameter

7. Delivery of prototype software to the EPRI Software

Derivation (PPPD) software allows engineers to derive parameters for

Engineering Team

standard (that is, Institute of Electrical and Electronics Engineers)

8. Workshop

generator and exciter models and for combustion turbine governor

9. Software release in 2009

models.

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

The objective of this project is to extend the PPPD softwa re to calculate

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

steam turbine parameters from staged tests and system disturbances

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 defi ne 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. For more information, contact Jan Stein, 650.855.2390, [email protected]. Steam Turbine-Generator Notes

10

July 2008

New Turbine-Generator Projects Delivered in 2007 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 React ive Power Capability, Excitation System Functions, and Frequency Response Report 1014911

avoid interruptions, and protect equipment.

metallurgical evaluation for the assessment

This report summarizes various methods of

of cracking are addressed. Considerations

obtaining the model data and describes the

to make when deciding when to initiate a

benefits and drawbacks of each.

crack repair—repair methods for turbine

Negative Sequence Effects on Generator Rotors Report 1014910

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

See p. 10 for article.

documented.

Steam Turbine Blade Failure Root Cause Analysis Guide Report 1014137

Steam Turbine On-Line Blade Condition Assessment Report 1014143


This report evaluates commercially available and emerging technology for on-line

Boresonic Inspection Primer Report 1014140

condition assessment of large steam turbine

Turbine rotor reliability and remaining life

that can detect changes in blade vibrational

prediction are areas of concern for utilities that

characteristics associated with propagating

are interested in component life extension and

cracks. Finite element modeling and analysis

longer inspection outage intervals. Boresonic

in combination with fracture analysis was

inspection of the highly stressed rotor bore

used to assess the effects of crack propagation

area provides the nondestructive inspection

on measurable L-0 blade characteristics.

data that are among the inputs used in

Provided in the report are recommendations

determining rotor operability and remaining

for appropriate monitoring technologies

life. Determination of the boresonic system’s

that are based on the analyses. Industry

performance

experience with currently available on-line

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

blades, with concentration on technologies

blade monitoring technology is included.

Steam Turbine Bolting Maintenance Guide Report 1013341

well as guidance in the evaluation and selection of boresonic inspection providers.


Inspection and Damage Assessment of Turbine Casing Cracks Report 1014138

Accurate simulation models of power This report presents guidance on determining system equipment are beneficial to al l power run/repair/retire options for cracked casings. system participants: such models maximize

Nondestructive evaluation techniques and

equipment availability, minimize losses,


11

July 2008

Fifth EPRI Turbine-Generator Program Productivity Improvement Expert Technology Transfer Workshop and Reviews 2008 Summer 2008 TGUG Meeting Access to the Productivity Improvement Expert Reviews (PIER ) web The EPRI Turbine-Generator (TG) Program will hold its Fifth

site for 2008 is limited to companies participating in this project.

Technology Transfer Workshop and a summer Turbine-Generator Users

EPRI, its technical staff, and its expert consultants have developed

Group (TGUG) meeting the week of August 11, 2008 in Concord,

this web site to provide critically evaluated information of direct

North Carolina (near Charlotte, North Carolina) at the Embassy Suites

value in improving the availability, efficiency, and profitability of

Convention Center.

fossil steam power plants.

The workshop will be conducted Monday and Tuesday, with three

Over the last 10 years, this site has become a valuable resource to

workshop tracks running in parallel. Track 1 will feature the presentations

generating companies by summarizing successful applications that

“Steam Turbine Design 101,” “Steam Turbine Performance 101,” “Steam

have already proved to be of significant value to other operating

Turbine Chemistry 101,” “Turbine Water Induction 101,” and “Turbine

units. Hundreds of critically assessed case studies are documented

Life Cycle Management/R emaining Life 101.” Track 2 is the Conference

in the site’s pages, and this has allowed others to duplicate these

on Generator Predictive Maintenance, Generator Stator Winding High-

successes. Additionally, the site tracks creative new ideas that are

Potential Testing, and Generator DC High-Potential Ramp Testing.

very close to broad power plant use. These current items of interest

Track 3 will include presentations on the newly released Steam Turbine

alert readers to technology on the brink of commercial application.

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).

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,

The TGUG meeting will include presentations by General Electric,

TR-114910, and 1006315) quickly sold out. The contents of the

Siemens, Toshiba, Hitachi, Mitsubishi, and Alstom, as well as

third edition can be accessed instantly on this site.

presentations on topics such as electrohydraulic control retrof its, Detroit

In addition to the web site, hardcover annual summary reports of

Edison’s on-line monitoring program, and Electrobrás Termonuclear's

Productivity Improvement Case Studies are available and have found

overview of its TG program. On Thursday afternoon, the group will

their way into operating power plants for quick reference by plant

tour the nearby Pioneer Bearing Motor Company facilities and attend a

staff. Every year, members of the PIER group are able to request

dinner at the Lowe’s Motor Speedway hosted by Pioneer Bearing Motor

copies of these annual summaries for all their operating power

Company.

plants, and members have found these hard copies to be a useful

Complete meeting details can be found on EPRI’s web site through the following

address:

supplement to the web-based versions.

http://guest.cvent.com/EVENTS/info/summary.

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

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


12

July 2008

Steam Turbine Valve Actuator Condition Assessment Guide In early 2008, work began to produce a guide on valve actuators which

3. Technical Description. It is expected

will complement the EPRI report Guidelines and Procedures for Turbine

that this section will include a general description of the

Valve Condition Assessments (1010211) published in 2005. The new

mechanical/hydraulic and the electrohydraulic turbine control

report will provide detailed instruction on valve component inspection

systems, with emphasis on the hydraulic actuator function for

and assessment criteria during disassembly and specifications for proper

the steam turbine valves. The components of the hydraulic

valve reassembly clearances. Turbine Valve Actuator Condition Assessment

cylinder and actuator assembly for the turbine valves will be

will cover the hydraulic valve actuators for the turbine valves addressed

explained.

in Guidelines and Procedures for Turbine Valve Condition Assessments.

4. Inspection. It is expected that this section will include inspection criteria for GE and Siemens Westinghouse

The following steam turbine valve applications will be discussed in the

turbine valve actuators. Copies of data sheets for recording

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

measurements and condition should be included, and the

•

•

•

•

criteria for inspecting the actuators should be given. 5. Maintenance. The maintenance section will most likely

GE nuclear valves: control, stop, reheat stop, and intercept valves Siemens Westinghouse fossil valves: throttle, governor, intercept, and reheat stop valves

include preventive and corrective maintenance tasks for GE

Siemens Westinghouse nuclear valves: governor and throttle valves

procedures for disassembly, repair, and reassembly of the

and Siemens Westinghouse turbine valve actuators. Applicable actuators should be included. This section is also likely to list

A technical advisory group (TAG) consisting of nuclear and fossil plant

any special tooling and safety considerations for working on

representatives was formed. The TAG members are as follows: Bob Bjune, South Texas Project

valve actuators.

•

•

Tony Khalid, Exelon/Corporate

The development of the report began in April 2008, and a conference

•

Tom Kordick, Ameren/Corporate

call with the TAG members occurred on May 15, 2008. A survey was

•

Mark Miller, Duke Energy/Catawba

sent in June 2008. Review of a first draft is planned for July 2008, with project completion scheduled for the end of this year.

Jim Olson, Tennessee Valley Authority, Corporate

•

•

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

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.

A Sample Turbine Valve Hydraulic Cylinder Dimension Chart


13

July 2008

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 Wear Resistance Versus Hardness of Turbine Valve Materials (Courtesy of TVA) international members. •

It was decided to develop one comprehensive

Intercept/combined reheat-intercept valves

report that would cover the metallurgical

The steam valve components to be covered in

aspects of the steam tu rbine valve components,

the reports include the following: Bushings

including the use of alternative materials,

•

•

Metallurgy: microstructure, heat treatment, and coatings

•

Damage mechanisms

•

Life assessment

•

Repairs: welding, coatings,

•

Main and bypass valve disks

international members. These reports will

•

Pressure seal heads

be funded by members of EPRI programs

•

Seats

It will be necessar y to conduct extensive research

•

Stems

into the valve materials used on the U.S. and

for U.S. members and another report for

65/NSTI and 87.

and heat treatment

The steam turbine valves used in the United

The metallurgical topics to be covered for each

international steam turbine valve components.

States consist of the General Electric-

of the components are the following:

A survey on valve materia ls will be sent to fossil

manufactured and Siemens Westinghouse-

•

manufactured valves used in fossil and nuclear

by different manufacturers, to

plants. The international turbine manufact urers

include alternative materials

include Alstom, Hitachi, Mitsubishi, Toshiba, Siemens, and Allis Chalmers. The turbine valves to be included in the reports are the following: Main stop/governor •

The alloy standards/materials used

•

Chemical composition

•

Physical properties

•

Mechanical properties: yield

valve part suppliers. We plan to include the following sections and content in the report: 1. Introduction: background, overview of report content, glossary, continued on page 20

strength, tensile strength, hardness,

•

Control/throttle

fracture appearance transition

•

Reheat stop

temperature, and creep rupture


and nuclear plants, manufacturers, and other

14

July 2008

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 softw are (1014971) is the most comprehensive effort u ndertaken 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® Turbof luid 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 f lame resista nce (ISO 14935)

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


15

July 2008

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 retightening between overhauls. It is then

Figure 1. Stress Relaxation

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

2. Glossary. There are 38 pages of terms

7. Inspection, Assessment, and Maintenance Planning. This

and def initions. 3. Technical Description. This

section covers manufacturers’

in this way must continue to meet the design

section includes general information

recommendations, a life assessment

requirement so that the residual stress on the

on design, types of threads, bolt-

approach, approaches to aid in

bolt does not cause the applied load on the

tightening methods, and safety

selecting fasteners for destructive

flange to fall below the steam load.

concerns.

examination, inspection, and actions

Possibly, the most important materi al property for high-temperature bolts is the stress relaxat ion strength of the bolt material. The relaxation strength is usually taken as the relaxed stress after a fixed time, nominally 10,000–30,000

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

to take when a cracked fastener is found. 8. Appendices. The appendices include

assembly procedures, and torquing

information on shaft coupling

assembly procedures.

bolts, a maintenance procedure for

5. Failure Modes. This section covers

tightening, a maintenance procedure

failure through the male threads,

for removal of broken or seized bolts

thread stripping, and other factors;

or studs, metallurgical summaries,

In practice, a joint might experience many

damage mechanisms; and 12 case-

a summary of bolting information

more than six re-tightenings if the source of

study examples of failures.

bulletins, procedures for tracking

hours, as a function of an initial strain level of 0.2%. This is shown in Figure 1.

the operating periods is significantly less than

6. Materials Selection. This section

bolt operating hours and history,

30,000 hours.

includes metallurgical information

ultrasonic examination of studs

In an effort to address this relaxation and many

for chromium molybdenum ferritic

and bolts from the bore surface,

other turbine-generator bolting issues, this

steels, 12% chromium martensitic

ultrasonic examination of studs and

new Steam Turbine Bolting Maintenance Guide

steels, age-hardenable steels, ASTM

bolts from the end surface, resources,

(1016958) contains the following information:

International A286 alloy, nickel-based

1. Introduction. This section covers the

alloys, and Refractalloy 26 materials.

continued on page 20

background and report structure and includes some summary remarks.


16

July 2008

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 followin g is a list of suggested projects tentatively scheduled for deliver y in 2009–2010 by Program 65 and NSTI.

Projects Planned for 20 09–2010 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 Softwa re

2009

Jan Stein

International Update to Metallurgical Guide for Turbine Rotors and Disks

2009

John Shingledecker

International Valve Metallurg y 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 Softwa re

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

Tiffa ni 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


17

July 2008

Stress Corrosion Cracking and Corrosion Fatigue Workshop to Be Held EPRI 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 mitigat ion strategies, wil l encompass past experiences a nd 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].

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

2009 European TGUG Workshop and Meeting

Program 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 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

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

details are finalized. For additional information, contact Alan Grunsky, [email protected]

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, ggolden@epri .com.


18

July 2008

Turbine-Generator Supplemental Projects Demonstration of Fatigue Sensor Technology for Steam Turbine Blades

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

Blade failures are a common reason for unplanned outages related to steam turbines. The damage associated with failure of large low-

Generator shaft keyway cracking has been experienced in two

pressure blades can be extensive and costly. Many nondestructive

nuclear four-pole generators. The cracking initiated in the

inspection methods and technologies exist to provide detection of

inboard side of the shaft keyway as a result of fretting fatigue. The

cracking that has already occurred. However, standard nondestructive

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

Experimental Measurement of a Fatigued Section of a Turbine Blade

for a subsequent repair outage.

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.

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

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

The EPRI supplemental project “Detection of Shaft Keyway Crack ing 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 continued on page 20


19

July 2008

Turbine-Generator Supplemental Projects continued from page 19

inspection with minimal impact on unit availability. Linear phased

that this approach is viable. Verification of the modeling work will

array ultrasonic technology allows steering of the ultrasonic energy

be completed on a full-scale mockup using a variety of manmade

by phasing of the individual probe elements. Because of this featu re,

targets. The flaw detection and sizing capabilities of the developed

it is feasible to inspect the inboard portion of the shaft keyway by

technique will also be evaluated on the mockup. Retired generator

conducting the inspection from the accessible shaft surface adjacent

rotor segments are being used for the full-size mockup.

to the inboard side of the shaft keyway. Mathematical modeling

For additional information on this activity, contact Paul Zayicek,

efforts of this inspection application using EPRI technology indicate

704.595.2154, [email protected].

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

Steam Turbine Bolting Maintenance Guide

continued from page 14

continued from page 16

2. Valve Bushing Materials: alloy standards (including

and bolts from the bore surface, ultrasonic examination

alternative materials), chemical composition, physical

of studs and bolts from the end surface, resources,

properties, mechanical properties, metallurgy, damage

a questionnaire to utilities, turbine valve bolting

mechanisms, life assessment, repairs

information, and bolting procurement guidelines.

3. Main Valve and Bypass Valve Disk Materials: alloy

The report was made available through the EPRI web site

standards (including alternative materials), chemical

on December 31, 2007, and hardcopy reports were mailed

composition, physical properties, mechanical properties,

to members in March 2008. After the report’s publication, a

metallurgy, damage mechanisms, life assessment, repairs

purchase bid specification for bolting was developed and added

4. Valve Seat Materials: alloy standards (including

to the EPRI report Guidelines for Reducing the Time and Cost


of Turbine-Generator Maintenance Overhauls and Inspections,


Volume 4: Turbine-Generator Component Procureme nt Specifications


(1016346), published March 2008. T his bid specification was a lso

5. Valve Stem Materials: alloy standards (including

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].

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 fina l 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].


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July 2008

Axial Entry Disk Blade Attachment NDE Performance Demonstration The 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-servic e 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

A Cracked Axial Entry Disk Blade Attachment

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

Determination of β Parameter for 12% Cr Turbine Blades Using Fatigue Sensor Technology The 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. For more information on this activity, contact Paul Zayicek, 704.595.2154, [email protected].


21

July 2008

Guide for Inspection of Low-Pressure Turbine Blades Periodic inspection of low-pressure (LP) turbine blades is essential for ea rly 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 exa mination (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].

Complete Fracture of Blade Root in Service

Optimization of Fatigue Sensor Measurement for Curved Blade Surfaces Fatigue 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 accu mulates, 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 strateg y is to explore pulseecho 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. For more information on this activity, contact Paul Zayicek, 704.595.2154, [email protected].


22

July 2008

Upcoming Events

Program Staff

2008 Meetings

Date

Location

Fith Turbine-Generator Technology Transer Workshop and Summer Turbine-Generator Users Group (TGUG) Meeting

Aug. 11–15, 2008

Concord, NC Embassy Suites

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 & Corrosion Fatigue Workshop Boiler/Reactor Feedpump Turbine Workshop

Oct. 1–3, 2008

Nashville, TN Gaylord Opryland Hotel

Nov. 18–20, 2008 Nashville, TN Vanderbilt Marriott Hotel

2009 Meetings

Date

Location

Winter 2009 TGUG Workshop and Meeting with Vendor Fair

Jan. 19–23, 2009

Savannah, GA Hyatt Regency

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

TBD

Summer TGUG Meeting

TBD

Aug. 12–14, 2008

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, agrunsk [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]

Steam Turbine Blade Failure Root Cause Analysis Guide Steam Turbine Blade Failure Root Cause Analysis Guide (1014137) is a reference written for operators to pla n 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].


23

July 2008

The

Export Control Restrictions Access to and use o EPRI Intellectual Property is granted with the specifc understanding and requirement that responsibility or ensuring ull compliance with all applicable U.S. and oreign 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 oreign export laws and regulations. In the event you are uncertain whether you or your company may lawully 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 lawul. Although EPRI may make available on a case-by-case basis an inormal assessment o the applicable U.S. export classifcation or specifc EPRI Intellectual Property, you and your company acknowledge that this

Electric

Power

Research

Institute,

Inc.

(EPRI, www.epri.com) conducts research and development for the global electricity sector. An independent, nonprofit organization, EPRI brings together experts from academia and industry as well as its own scientists and engineers to help address challenges in electricity generation, delivery and use, including health, safety and the environment. EPRI also provides technology, policy and economic analyses to drive longrange research and development planning, and supports research in emerging technologies. EPRI’s members represent more than 90 percent of the electricity generated and delivered in the United States, and international participation extends to 40 countries. EPRI’s principal offices and laboratories are located in Palo Alto, California; Charlotte, North Carolina; Knoxville, Tennessee; and Lenox, Massachusetts.

assessment is solely or inormational purposes and not or reliance purposes. You and your company acknowledge that it is still the obligation o you and your company to make your own assessment o the applicable U.S. export classifcation 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 o EPRI Intellectual Property hereunder that may be in violation o applicable U.S. or oreign export laws or regulations.

1016976

July 2008

Electric Power Research Institute

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EPRI-Steam Turbine Generator Notes

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