221531471 Boiler Tube Assessment

Babcock & Wilcox 1

G.J. NakonecznyR.D. Murphy

Babcock & WilcoxBarberton, Ohio, U.S.A.

R.M. TilleyElectric Power Research InstituteCharlotte, North Carolina, U.S.A.

Presented to:ICOLM (International Conference on Life Managementand Life Extension of Power Plant)May 2000Xian, P.R. China

Application of EPRI/B&W Developed EMAT Systems forAssessing Boiler Tubes

BR-1693

AbstractBoiler tube failures continue to be the main cause of boiler

forced outages.[1] This fact is not surprising considering the milesof linear feet of boiler tubing in the furnace enclosures and con-vection passes that are subject to deterioration from both nor-mal and abnormal wear. One of the emerging technologies toaddress the assessment of boiler tubes is Electromagnetic Acous-tic Transducers or EMATs. Although the concept and theory ofEMATs was first demonstrated many years ago, it is only inrecent years that field-portable applications have been devel-oped and deployed to help the power industry. Babcock &Wilcox working with EPRI on a project to develop advancednondestructive testing (NDT) techniques for the assessment ofboiler components developed a versatile EMAT testing system,named the FST-GAGE test system by B&W. The FST-GAGE,or Fast Scanning Thickness Gage, was developed specificallyto scan boiler tubes and provide a continuous measurement oftube wall thickness. Early generations of the device, first intro-duced in 1994, proved to be a very effective NDT system fordetection of isolated inside diameter (ID)-initiated tube dam-age such as hydrogen damage and under deposit corrosion. Ex-perience after scanning more than one million linear feet of tub-ing has proven the benefits and allowed boiler owners to findand selectively replace only damaged material. Responding tothe need of boiler owners to find cracking as well as thinning,modified probes for the FST-GAGE have been developed whichdetect ID tube cracking. In 1998 the next generation of the EMATtube thickness system which incorporated electronic data ac-quisition and storage was completed and tested. This latest ad-vancement of the FST-GAGE allows for continuous thicknessmapping of boiler tubing.

Continuing the development of applications using the EMATtechnology, EPRI sponsored a separate project to develop a sys-tem for the detection of cracking in boiler tubes associated withcorrosion fatigue. The system developed for corrosion fatiguehas unique characteristics that enhance its ability to scan pastwelds and attachments and scan the full circumference of theboiler tube. The corrosion fatigue EMAT system has proven veryeffective for crack detection under laboratory conditions and isnow being deployed for testing under field conditions.

Presented below are the applications of EMATs for boilertube assessment and the experience gained from deployment ofthe FST-GAGE and corrosion fatigue testing systems.

IntroductionUltrasonic-based techniques for nondestructive measurement

and volumetric examination have been around for more thanhalf a century. Ultrasonic testing is an indispensable part ofnondestructive examinations in support of quality control inmanufacturing, as well as evaluation of materials exposed toservice to assess their integrity and fitness for continued use.Historically, ultrasonic testing utilizes piezoelectric transduc-ers to develop the ultrasonic wave in the test material, in whichan electrical field is applied to a piezoelectric crystal and con-verted into a mechanical pulse. To impart this mechanical pulsefrom the transducer into the test material requires a couplantsuch as water, oil, grease or one of the commercially availablegel-type couplants. The requirement of a couplant can hinderinspection applications where scanning is required to cover largeareas. An alternate technique for introducing ultrasonic wavesinto a test material called Electromagnetic Acoustic Transduc-

2 Babcock & Wilcox

ers or EMATs was first introduced more than thirty years ago.EMATs have unique advantages over piezoelectric transducersfor certain applications. In the 1990s advances in computersand electronics made it commercially feasible to develop por-table EMAT-based systems for nondestructive testing in fieldapplications.

The Electric Power Research Institute (EPRI), Babcock &Wilcox (B&W) and McDermott Technologies, Inc. 1 (MTI) de-veloped a boiler tube inspection system which utilizes EMATtechnology. The new system, named the FST-GAGE systemby B&W, has been used to provide commercial testing servicessince 1994. The inherent advantage of the FST-GAGE test forboilers is its ability to rapidly scan large areas of the tubing todetect isolated damage. Prior to the development of this sys-tem, testing of boiler tubes was primarily limited to spot checksof wall thinning using conventional ultrasonic thickness gaugesduring outages. This resulted in only a small fraction of the tubewall area being tested. With EMATs, the FST-GAGE systemcan, if necessary, scan the entire furnace to detect thinning anda variety of other boiler tube failure mechanisms such as pittingand hydrogen damage. Experience in more than seventy boilersurveys in which well over one million feet (> 300 km) of tub-ing was tested has proven the value of this system to boiler own-ers. Building on the success of the FST-GAGE instrument de-velopment, efforts continue on EMAT-based systems and appli-cations for detecting boiler tube cracking associated with mecha-nisms such as corrosion-fatigue and stress-assisted corrosion.

Electromagnetic Acoustic TransducersAn EMAT, in contrast to piezoelectric transducers, gener-

ates and transmits an ultrasonic wave into the test materialthrough electromagnetic acoustic interaction with the test piece

1 McDermott Technologies, Inc., formerly called the Babcock &

Wilcox Research Division.

itself and does not require intimate contact with the material.Since the ultrasonic pulse is developed in the material to betested, EMAT can only be used on electrically conductive ma-terials. The FST-GAGE instrument is designed specifically fortesting of ferromagnetic material, which requires unique instru-ment design parameters as opposed to systems that are designedto test strictly non-magnetic materials. The basics of the EMATare illustrated in Figure 1. A strong magnetic field (B) is pro-duced at the surface of the test piece by using an electromagnetor permanent magnet. Eddy currents (J) are induced in the sur-face of the test material. An RF current flow introduced in awire, in the presence of the magnetic field (B) generates a Lorentzforce (F), which in turn produces a stress wave in the material.

FST-GAGE SystemIn practice, the operation of the FST-GAGE instrument is

more complex (see Figure 2). The system is comprised of threebasic componentsthe probe, the display panel, and the instru-ment box. The instrument box houses the power supplies, digi-tizer, timing circuits and processor. The display panel or opera-tor interface allows the operator to set up, adjust and calibratesystem parameters in a Windows program environment. Thedisplay also provides output to the operator during the inspec-tion. The probe is the working end of the system with its majorcomponents being the pulse magnet along with separate trans-mit and receive EMAT coils. A strong pulsed magnet is used toproduce a magnetic field (B). RF currents (4 to 5 Megahertz)are produced in the transmit EMAT coil by the EMAT pulsecircuitry. A separate receiver coil is synchronized with the trans-mit pulse to effectively receive the return pulse in the test mate-rial. By using the two EMAT coils the FST-GAGE operates ina pitch-catch mode. To set up the FST-GAGE for thicknessmeasurement, the transit time for the ultrasonic wave to travelfrom transmitter EMAT coil through the tube material back tothe receiver EMAT coil is calibrated on a known thickness stan-

Figure 1 Electromagnetic Acoustic Transducer (EMAT).

Magnet

EddyCurrentCoil

ConductingMaterial

B (Magnetic Force)

Ultrasonic Wave

J (Eddy Currents)

F (Lorentz Force)

Magnetic field (B) interacts with eddycurrents (J), producing Lorentz force(F=JxB), generating a mechnicalwave

Ultrasonic (mechnical) wave propa-gates through material detectingflaws

Electromagnetic AcousticTransducers (EMAT)

Babcock & Wilcox 3

dard. The FST-GAGE measures tube wall thickness with anaccuracy of 0.005 (0.127 mm) on thicknesses from 0.1 (2.54mm) to 0.5 (12.7 mm), and diameters between 0.875 (22.2mm) to 3 (76.2 mm) OD.

Prior to 1998 the first generation FST-GAGE was used pri-marily for surveys to identify isolated tube damage. Many in-spections were performed on units that had experienced failuredue to hydrogen damage or internal corrosion and where theowner needed to isolate the damaged tube material for selectedreplacement. The early generation FST-GAGE did not havedata acquisition and storage capability, which limited its usefor thickness surveys. In 1998 the second generation FST-GAGE was built and deployed. The newest systems incorpo-rate improved software, the addition of an encoder on the FST-GAGE probe to indicate position on the tube, and data storagecapability. The current FST-GAGE instrument is therefore wellsuited to perform boiler thickness mapping surveys in additionto the role of scan and detect surveys.

To perform an inspection, the FST-GAGE probe is manu-ally scanned along individual boiler tubes. System sampling atrates greater than 65 samples per second supports rapid scan-ning of tubes. During a scan, the system provides an immediatedisplay and disposition of tube wall thickness. At the conclusionof each scan, a complete record of each inspection is electronicallystored and traceable to each unique boiler tube and position.

FST-GAGE Service Experience

Hydrogen Damage DetectionHydrogen damage is a serious failure mechanism that con-

tinues to affect many boilers in the electric utility industry.Hydrogen damage is a potential problem found in waterwalltubes of drum-type boilers. The problem is most often associ-ated with waterside deposits (a dirty boiler) coupled with an

abnormally corrosive environmentmost often a low pH ex-cursion in the boiler water chemistry. Deregulation in the U.S.electric utility industry has, more than ever, placed a premiumon lowering the O&M costs. One effect has been to extend thetime between chemical cleaning of the boilers. As a result thepotential for hydrogen damage and other waterside damage dueto corrosion has increased in many instances. For hydrogen dam-age to occur, corrosion occurs beneath waterside deposits. Thiscorrosion process releases atomic hydrogen that diffuses intothe metal structure of the tube, reacts with the carbides in thecarbon steel and forms methane (CH4). The large methane mol-ecules, trapped in the grain structure of the metal, produce in-tergranular cracking and embrittlement of the tube wall. Fail-ures tend to be sudden and catastrophic with a blow out of ma-terial. B&W has years of experience in inspection of boilers todetect hydrogen damage using FHyNES, a patented inspec-tion method based on ultrasonic testing.[2]

Hydrogen damage in tube material reduces (attenuates) anultrasonic signal passing through the affected material. This at-tenuating effect is the basis of past ultrasonic detection tech-niques as well as the EMAT technique. Hydrogen damage nor-mally occurs in a random pattern. After a failure has occurred itis imperative to locate the affected material for replacement ifrepeat failures are to be avoided. Since EMAT does not requireda fluid or gel-type couplant, scanning can be done much fasterthan UT-based techniques. Additionally, EMAT testing is moretolerant of tube surface conditions such that tube cleaning re-quirements may be less demanding than for UT.

The ability of the FST-GAGE system to detect hydrogendamage was verified in the laboratory. Two boiler tube sampleswith hydrogen damage were examined with the instrument andit was shown that damaged areas could be detected by signalattenuation (see Figures 3 and 4).

Forty-two (42) FST-GAGE surveys have been conductedfor detection of hydrogen damaged tubes in boilers. In all of the

Figure 2 FST-GAGE instrument system.

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Figure 3 EMAT scan away from area of hydrogen damage. Figure 4 EMAT scan on hydrogen damage.

Start of scangood tube

Hydrogen DamageAmplitude 86%Thickness.259

Start of hydrogen damageacceptable thickness,unacceptable amplitude loss

Hydrogen DamageAmplitude 51%Thickness.245

surveys, the indications were confirmed by UT, visual, and/ordestructive testing. Table 1 gives a sampling of boilers tested,the time it took to perform the test and the number of indica-tions identified. The EMAT system has proven to be very sensi-tive for detection of damaged tubes while maintaining scan ratesmore than five times those of previous ultrasonic techniquessuch as FHyNES.

Detection of Pitting or Wall LossThe FST-GAGE instrument has also demonstrated good sen-

sitivity for the detection of pittinganother isolated damagemechanism that is very difficult to detect when scanning byconventional UT-based methods. Just as with hydrogen dam-

age, pitting is a result of corrosion. Pitting is generally associ-ated with boilers that have experienced ingress of excessiveoxygen in the boiler water, or, sustained idle periods with inad-equate storage provisions. Less severe, from the standpoint ofdetection, is wall loss from caustic gouging. Similar to pitting,caustic gouging is associated with corrosion and wall loss butaffects a larger area of the tube and is therefore less difficult todetect and quantify.

As part of the development work on the system, the abilityof the FST-GAGE to detect pitting on tube ID surfaces wasevaluated. Six different samples having both real and simulatedpitting were tested using three different EMAT coil configura-tions. In general, pits with a diameter of 0.125 (3.2 mm) or

Table 1FST-GAGE Surveys for Hydrogen Damage Detection

Test reference, Hours Linear feet Indications Indications confirmedregion and unit number for test (meters) examined identified

Survey A 80 5,400 (1,646) 144 Verified initial cutoutsSouthern U.S.A., Unit 2 All confirmed

Survey B 24 17,200 (5,243) 158 Same as aboveEastern U.S.A., Unit 3

Survey C 16 9,800 (2,987) 9 Same as aboveSouthwestern U.S.A., Unit 3

Survey D 96 79,600 (24,262) 91 Same as aboveNortheastern U.S.A., Unit 4

Survey E 144 43,400 (13,228) 900 Same as aboveSouthern U.S.A., Unit 3

Survey F 32 25,850 (7,879) 54 Same as aboveSouthwestern U.S.A., Unit 3

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Table 2Campaign for Mitigation of Failures due to Pitting

March 1995 Detected by FST-GAGE and removed 23

95/96 Leaks repaired from 3/95 to 3/96 9








99/present Leaks repaired from 3/99 to present 0

larger were detectable as indicated by a decrease in signal am-plitude. Although the system can effectively detect pitting, siz-ing (determination of remaining wall) of the pits is difficult.Just as with normal ultrasonic testing, sizing of pits was stronglyinfluenced by the shape and depth of the defect as well as thecalibration range of the instrument. For example, it was typi-cally easier to size a flat bottom hole (FBH) than a hole with aconical or spherical shape due to the scattering of sound by thelatter shapes. Laboratory tests indicated that the threshold forsizing was a pit size of approximately 0.25 (6.4 mm) diameteror larger. Accuracy in sizing was not within typical thicknessmeasurements, 0.005 (0.127 mm). However, in almost allcases, there was sufficient accuracy to enable an operator todetermine whether the pitting depth was a significant fractionof the total tube wall.

It was noted that the calibration of the instrument has aneffect upon sizing capability since the smallest thickness of thecalibration standard used sets a lower limit on the thickness read-ings of the EMAT system. In practice, the FST-GAGE is usedto scan and detect areas of pitting. Sizing, if required, is done infollow up with either the EMAT test or UT thickness methods.

A utility in the southeastern U.S.A. was experiencing forcedoutages due to furnace wall pitting. The pitting was caused bycopper layout that resulted from an ineffective chemical clean-ing. The FST-GAGE was used to inspect the boiler five (5)times over a four (4) year period reducing their forced outagesfrom water wall failures from five (5) per year prior to inspec-tion to no water wall leaks by the third year. Table 2 gives theresults of the inspections and the subsequent tube leaks duringthe year after the inspections.

Corrosion FatigueWaterside corrosion fatigue is a serious boiler tube failure

mechanism. The failures usually occur close to attachments suchas buckstay welds or windbox attachment welds. The combina-tion of thermal fatigue stresses and corrosion leads to ID-initi-ated cracking that is oriented along the tube axis. The result canbe a tube leak on the external side of the boiler wall. If failuresoccur in enclosures such as the windbox, vestibules or pent-house, there is the potential for pressurization and failure of thecasing as well. Corrosion fatigue cracking can also occur on thefire side of the tubes and is dependent upon boiler design,stresses and stress cycles, as well as water chemistry.

FST-GAGE ApplicationOne detection method, based on EMAT technology, was de-

veloped as a modified use of the FST-GAGE system. Specialcoils and filtering were adapted to the FST-GAGE for detec-tion of corrosion fatigue cracking that is oriented axially alongthe tube crown or adjacent to the tube membrane. The FST-GAGE is applicable for detection of damage where tube ac-cess is available on the same side of the tube as the damageoccurs. For this special application EMAT coils are modified asillustrated in Figure 5. The pitch-catch coils are located betweenthe poles of the magnet and oriented in a side angle. The signalfrom the transmitter coil propagates as shown in Figure 5. With-out a flaw, there is no received signal. If a flaw is present, soundis reflected into the receiver coil and an indication is observedon the instrument display. Figure 6 illustrates a typical indica-tion. The indication is from an EDM notch with dimensions 1(25.4 mm) long x 0.050(1.27 mm) deep on the ID of the crown

of boiler tube in a membrane panel with tubes having a diam-eter of 1.25 (31.75 mm) and a wall thickness of 0.188(4.8mm). In Figure 6, the notch has been scanned multiple times toverify the repeatability of the measurement. As shown, the sig-nal to noise ratio of this simulated defect was very good.

With the corrosion fatigue configuration, one scan will de-tect cracks on the crown of the tube. Additional scans can de-tect cracks along the membrane welds. This technique provedthat the FST-GAGE equipment can be used for the detectionof one type of corrosion fatigue damage. The technique has beenused successfully in commercial inspections. The largest scopeinspection with this variation of the FST-GAGE was done at aWest Coast utility that was experiencing tube failures due tocorrosion fatigue at the membrane area in their waterwall tubes.The FST-GAGE, with the modified EMAT coils, was used toscan approximately 98,000 linear feet (29,870 m) of membranetube welds. Numerous indications were found on all four walls.A representative sample was removed for verification of sys-tem sensitivity. The system was capable of identifying internalcorrosion fatigue with a through-wall depth of 0.015 (0.381mm).

EPRIDedicated EMAT Technique for Detectionof Corrosion Fatigue Damage

McDermott Technology, Inc., under contract with EPRI hasdeveloped an EMAT technique for detection of corrosion fa-tigue cracks from the opposite tube wall, i.e. detect cold side(boiler external) cracks from the fire side (boiler inside furnace)tube surface. The great advantage of and advancement in thistechnique is that boiler tubes experiencing the cold side attach-ment cracking due to corrosion fatigue can be examinednondestructively from the hot side of the tube where access isreadily available. The system under development will providegreater than 180 coverage of the tube cold side (boiler exter-nal) surface. This technique uses a unique instrumentation plat-form which, unlike the FST-GAGE, utilizes toneburst signalgeneration. The toneburst EMAT signal generation allows theuse of horizontally polarized shear waves (SH waves). A fulldiscussion of wave modes has been presented previously[3], how-ever, a unique feature of SH waves is that they are much lesssusceptible to mode conversion at weldsa critical requirement

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Figure 5 Thickness gauge modified to detect corrosion fatigue.

SoundPath

Poles of Pulsed Magnet

TransmitterCoil

ReceiverCoil

Flaw

TubePoles of Pulsed Magnet

Figure 6 Corrosion fatigue; scan of an EDM notch 1 (25.4 mm)long x 0.050 (1.27 mm) deep on the ID of the crown of a tube ina membrane panel.

for the system to detect cracking adjacent to external tube at-tachment welds. The prototype of this system have been devel-oped and tested by MTI in the laboratory with excellent results.Table 3 illustrates evaluation of the system and probe on 3 (76.2mm) diameter tubes with 1 (25.4 mm) long EDM notches thatvary in depth at 0.020 (0.50 mm), 0.050 (1.27 mm), and 0.100(2.54 mm). In all cases the system scanned past membrane weldsto detect notches on the opposite side of the tube. Currently thesystem is scheduled for field trials under actual boiler condi-tions to determine its detection capabilities.

Tube Thickness on Composite TubesAs noted above, the current generation FST-GAGE instru-

ment can efficiently measure and save data for wall thicknesson conventional carbon steel tube materials found in boiler fur-naces. The thickness gauge, in its usual configuration, reliesupon the presence of magnetostriction within a distance of oneelectromagnetic skin depth from the surface of a ferromagneticconductor. When there is a cladding overlay of anonferromagnetic material on the tube (as with a compositetube), then EMAT transduction with a pulsed magnet cannotoccur. Since composite tubes are used extensively in industriessuch as pulp and paper, the ability of the FST-GAGE to mea-sure tube wall thickness through a stainless steel layer was ad-dressed in the design. Instead of the pulsed magnet, a perma-nent magnet probe is used for tubes having a nonferromagneticcladding. This type of probe has proven to be very effective formeasuring the thickness of composite tubes with the same de-gree of accuracy as found on carbon steel tubes. The systemconfigured for composite tubes can measure wall thickness inthe range of 0.100(0.254 mm) to 0.500(1.27 mm), with0.005 (0.127 mm) accuracy.

Other EMAT ApplicationsJust as with ultrasonic testing, as EMAT techniques are de-

livered in field-portable systems other applications have beeninvestigated to address unique problems. The researchers atMcDermott Technologies, Inc. have the equipment and exper-

tise to apply the EMAT technology to applications where itsunique properties have an advantage over conventional UT tech-niques. An example of an application in which an EMAT testwas developed by MTI and then implemented by MTI and B&Wincludes the following.

Surface wave EMAT testing of tubesIn 1998, B&W was asked by one of its customers if an EMAT

test was available for detection of surface indications includingaxially oriented cracks in boiler tubes. The customer has threeheat recovery steam generator (HRSG) boilers that were expe-riencing surface cracking on the tube crown due to thermal fa-tigue. Conventional surface nondestructive test methods wereunsatisfactory because they lacked adequate sensitivity and hadslow production rates for testing of large areas. B&W workedwith its R&D group at MTI to test whether a suitable applica-tion was available. MTI determined that a tone burst EMAT tech-nique would meet the need and developed a system for the test.Testing was successfully performed on the customers unit 2Ain which 6,550 linear feet (1,996 m) of tubing were examined.The test uses a bi-directional focused surface wave EMAT thatworks at 1 MHz frequency. The surface wave is generated inthe tube and follows the tube surface circumferentially until thesignal is reflected back from a longitudinally oriented OD crack.The test is capable of detecting axially oriented surface indica-tions as small 0.005 (0.127 mm) depth at scanning rates of upto 6 inches per second (152 mm/sec). Based upon the successof the testing on unit 2A, the customer contracted B&W to per-form testing during three subsequent outages on the HRSG units(see Table 4).

SummaryEPRI-sponsored development has led to an EMAT system

(FST-GAGE) that has been proven under field conditions toeffectively measure and map boiler tube wall thickness. Thesystem has also been shown to be effective in detection of hy-drogen damage, pitting, and axial ID cracking. Modificationsto the EMAT coil configuration allow wall thickness measure-

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Table 3Evaluation of 3 (76.2 mm) Corrosion-Fatigue Probe

Description Notch Notch EMAT Side Notch Relative Signal Strength ApproximateDepth Location Location Detectable? % Full Screen Height Angular Offset*

Test 1 0.100" (2.54mm) Crown Opposite Yes 100 174



*The EMAT transmits a multiple skip wave around the tube circumference. Angular movement of the probe is done to optimize the relativesignal strength.

Table 4Surface Wave EMAT Tests

Unit Number Date Tested Linear Feet Examined Indications Found Confirmed Cracks*

2A September 1998 6,550 (1,996 m) 33 23A October 1998 18,580 (5,663 m) 57 71A December 1998 16,170 (4,929 m) 40 132A April 1999 17,200 (5,243 m) 17 0

*Axial cracks were confirmed by visual. Test sensitivity also detected indications associated with small pits, surface dents, weld splatter, etc.on tube surfaces.

Copyright ' 1999 by The Babcock & Wilcox Company,a McDermott company.

All rights reserved.

No part of this work may be published, translated or reproduced in any form or by any means, or incorporated into any information retrieval system,without the written permission of the copyright holder. Permission requests should be addressed to: Market Communications, The Babcock &Wilcox Company, P.O. Box 351, Barberton, Ohio, U.S.A. 44203-0351.

Disclaimer

Although the information presented in this work is believed to be reliable, this work is published with the understanding that The Babcock & WilcoxCompany and the authors are supplying general information and are not attempting to render or provide engineering or professional services.Neither The Babcock & Wilcox Company nor any of its employees make any warranty, guarantee, or representation, whether expressed or implied,with respect to the accuracy, completeness or usefulness of any information, product, process or apparatus discussed in this work; and neither TheBabcock & Wilcox Company nor any of its employees shall be liable for any losses or damages with respect to or resulting from the use of, or theinability to use, any information, product, process or apparatus discussed in this work.

ment in composite or bimetallic tubes. This versatility providesthe system with a wide range of uses from a single instrumenta-tion platform.

EPRI and MTI have developed an EMAT-based test systemdesigned specifically for detection of cracking associated withcorrosion fatigue. The unique characteristics of the SH shearwaves generated by this system make possible the detection ofcracks adjacent to welds. Having been proven under laboratorytest conditions, the corrosion fatigue system is now scheduledto undergo field trials under actual boiler test conditions. AsEMAT techniques are delivered to the field in portable systems,other applications will be identified and developed. The first ofthese new applications has been demonstrated and applied com-mercially for surface inspection of tubes.

AcknowledgmentsPrimary funding for development, testing and commercial-

ization of the FST-GAGE has been provided by EPRI on Con-

tract WO 1890-11, Improved Boiler Inspection Systems. De-velopment of the Corrosion Fatigue EMAT test system has beenfunded through EPRI Contract WO 4674-01, Development ofNDT Techniques for Detection and Sizing of Corrosion-FatigueCracks in Boiler Tubes.

References1. R.B. Dooley, P. Chang, The Current State of Boiler Tube

Failures in Fossil Plants, EPRI.International Conference on Boiler Tube Failures in Fossil

Plants, Nashville, TN, 1997.2. P.J. Latimer, et. al., A NDE Method for Hydrogen Dam-

age Detection in Fossil Boiler Tubes, EPRI Conference on LifeExtension and Assessment of Fossil Plants, Washington D.C. 1986.

3. P.J. Latimer, et. al., Electromagnetic Transducers forGeneration and Detection of Ultrasonic Waves, Acousto-Ul-trasonics, Plenum Publishing Corp. 1988.

221531471 Boiler Tube Assessment

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