3
Feature By Robert Ward Eddy current testing (ET) is fundamentally the same as it was when first introduced in 1879 by David Hughes, yet it remains among the best inspection techniques for use in many cases today. While the technology itself is unchanged, its applications have become much more sophisticated, particularly over the past twenty years. Inspection professionals across manufacturing, oil and gas, aerospace, power, and various other industries are able to perform inspections plus detect and size flaws with greater speed and accuracy than ever before. How and when ET is used has changed remarkably, and the digital age has brought transformational change for inspection technology. Recent advancements in eddy current tools have simplified not only the inspection process, but also the training and collaboration processes involved across industries, increasing the scope of applications and usefulness of the technology. As inspection technologies become more advanced, the need to recruit, train, qualify, and retain skilled nondestructive examination (NDE) personnel becomes increasingly important, especially in an industry where the workforce is rapidly aging. The Move from Analog to Digital One of the key benefits of ET for inspection technicians is its trans- portability, which can be traced back to the early 1990s. This was a turning point for the technology because it allowed technicians to bring the technology they needed into the field. The transition from large, analog technology to more compact, digital systems allowed inspectors to adapt the testing process for more NDE applications. For its previous 100-year history, performing ET required the equipment under review to be brought to a laboratory; now, inspectors could bring the ET equipment to the object in the field. Of course, transportability is a relative term, and in its first outside- the-lab incarnations, ET equipment was transportable on par with a refrigerator or a safe. The difference was significant enough, however, that ET could now be performed on equipment in the workplace. In the early field inspections, ET was used to check steam generators at nuclear power plants, to ensure that high-pressure radioactive steam from inside the reactor was not escaping to the environment. As the technology improved, the number of industries and applications using ET grew. Given the increasing number of facilities and systems that required constant inspection, performing and staffing regular inspections became a major challenge — especially for teams that were top heavy with advanced inspectors. In the 1990s, the company Zetec introduced a new method where an on-site team transmitted inspection data to a centralized analysis team using a satellite or online connection. This advanced process relieved the need for the experts to remain on site for analysis and final decisions. Zetec improved the productivity of Level III inspectors by enabling a given crew to support testing at multiple sites simultaneously. The Internet made data Inspection Trends / Summer 2014 17 Advances in Eddy Current Inspection Technology Eddy current testing has evolved in reaction to technological advances over the past decades, bringing it to new levels of value and performance With the portable Mentor EM from GE, there are no physical dials or other external variables on the device to affect test results; the probe used to perform the inspection is the only external feature. (All photos courtesy of GE Measurement and Control.) Ward Feature IT Summer 2014_Layout 1 8/6/14 10:54 AM Page 17

Advances in Eddy Current Inspection Technology · eddy current testing today. With today’s eddy current equipment, complex inspection projects can be completed in less time, with

  • Upload
    others

  • View
    19

  • Download
    0

Embed Size (px)

Citation preview

FeatureBy Robert Ward

Eddy current testing (ET) isfundamentally the same as it was whenfirst introduced in 1879 by DavidHughes, yet it remains among the bestinspection techniques for use in manycases today. While the technology itselfis unchanged, its applications havebecome much more sophisticated,particularly over the past twenty years.Inspection professionals acrossmanufacturing, oil and gas, aerospace,power, and various other industries areable to perform inspections plus detectand size flaws with greater speed andaccuracy than ever before.

How and when ET is used haschanged remarkably, and the digitalage has brought transformationalchange for inspection technology.Recent advancements in eddy current

tools have simplified not only theinspection process, but also the trainingand collaboration processes involvedacross industries, increasing the scopeof applications and usefulness of thetechnology. As inspection technologiesbecome more advanced, the need torecruit, train, qualify, and retain skillednondestructive examination (NDE)personnel becomes increasinglyimportant, especially in an industrywhere the workforce is rapidly aging.

The Move from Analog toDigital

One of the key benefits of ET forinspection technicians is its trans-portability, which can be traced back tothe early 1990s. This was a turning

point for the technology because itallowed technicians to bring thetechnology they needed into the field.The transition from large, analogtechnology to more compact, digitalsystems allowed inspectors to adapt thetesting process for more NDEapplications. For its previous 100-yearhistory, performing ET required theequipment under review to be broughtto a laboratory; now, inspectors couldbring the ET equipment to the object inthe field.

Of course, transportability is arelative term, and in its first outside-the-lab incarnations, ET equipment wastransportable on par with a refrigeratoror a safe. The difference wassignificant enough, however, that ETcould now be performed on equipmentin the workplace. In the early fieldinspections, ET was used to checksteam generators at nuclear powerplants, to ensure that high-pressureradioactive steam from inside thereactor was not escaping to theenvironment.

As the technology improved, thenumber of industries and applicationsusing ET grew. Given the increasingnumber of facilities and systems thatrequired constant inspection,performing and staffing regularinspections became a major challenge— especially for teams that were topheavy with advanced inspectors. In the1990s, the company Zetec introduced anew method where an on-site teamtransmitted inspection data to acentralized analysis team using asatellite or online connection. Thisadvanced process relieved the need forthe experts to remain on site foranalysis and final decisions. Zetecimproved the productivity of Level IIIinspectors by enabling a given crew tosupport testing at multiple sitessimultaneously. The Internet made data

Inspection Trends / Summer 2014 17

Advances in Eddy Current Inspection TechnologyEddy current testing has evolved in reaction to technological advances over the pastdecades, bringing it to new levels of value and performance

With the portable Mentor EM from GE, there are no physical dials or other externalvariables on the device to affect test results; the probe used to perform the inspection is theonly external feature. (All photos courtesy of GE Measurement and Control.)

Ward Feature IT Summer 2014_Layout 1 8/6/14 10:54 AM Page 17

transfer even simpler and, not longafter, software emerged to improve thequality and analysis of data, laying thefoundation for how ET is used today.

Making Smarter Machines

Eddy current testing equipmenthas tremendous sensitivity. Thetechnology can detect defects that arewell defined and discern defects eventhrough significant noise in the datasignal. This also means that very minorpatterns in a sample — for example,tooling marks left by the process oflathing during manufacture — couldgive a response very similar to a defectsignal. Noise, or signal interference,can be caused by naturally occurringfactors such as temperature, changes in

conductivity, and magneticpermeability.

The creation of noise-filteringtechnology opens the use of ET to abroader, constantly growing range ofapplications. Researchers discovered thatvarious types of signal noise occurred inrecognizable or predictable patterns.Anticipating and eliminating theseeffects using software-based processingon the source data essentially erasesnoise signals and leaves the rest of thepicture, allowing ET to reliably provideclear diagnostic images.

The effect of noise-filteringalgorithms on ET has been profound.Research led by Professor Lalita Updaat Michigan State University validatedthe accuracy of noise filteringalgorithms and led the Electric Power

Research Institute, a worldwideconsortium of utility companies, torecommend to member utilities that useof defect recognition software be theprimary means for signal identification.Experts are used in supporting andverification roles, to corroborate andvalidate the indications called out bythe software.

Advancements in technology havevastly improved the inspection process.For instance, the nuclear plant steamgenerator inspection that originallyrequired six inspectors working up to28 days can now be completed in undera week — with half the staff and withfar greater confidence in the data.

With technological advancementsalso come training advancements.Because ET devices provide clearinterpretations of scan results, lessexperienced inspectors are capable ofmaking critical decisions thatpreviously required the approval ofLevel II and III certified inspectors.Moreover, as ET equipment becomessmaller and less costly, its use expandsfar beyond the nuclear reactor, airplanemanufacturing floor, and petrochemicalprocessing operations that have longbeen its focus. One can now find high-end auto mechanics using ETequipment to detect whether parts aresuitable for use or require replacement.

New Frontiers for EddyCurrent Testing

There are a number of current andemerging trends that promise to furtherrevolutionize ET for the next phase ofinspection. One notable trend is therecent emergence of powerful,networked portable devices.

Previous generations ofinspection technology often requiredthe testing technician to carrycumbersome equipment, diagrams,maps, and numerous other paperdocuments for information on thetesting process and the standardrequirements for the test. Given thecomplex and often harsh industrialenvironments inspectors work in, thisprocess was far from ideal andintroduced a number of variables thatcould affect the accuracy of testresults.

This year, GE launched MentorEM. With this portable device, thetesting process is automated on-screen,including all relevant information ontest metrics, procedures, and standards.

Inspection Trends / July 201418

The recent emergence of powerful, networked portable devices is one of the notable trends ineddy current testing today.

With today’s eddy current equipment, complex inspection projects can be completed in lesstime, with fewer staff involved, and with far greater confidence in the data.

Ward Feature IT Summer 2014_Layout 1 8/6/14 10:54 AM Page 18

There are no physical dials or otherexternal variables on the device toaffect test results; the probe used toperform the inspection is the onlyexternal feature.

Where previous ET devices havebeen standalone units that perform areading — essentially like a veryadvanced pocket compass — MentorEM incorporates a comprehensiveinformation system. Not only cantechnicians capture its readings onto anetwork database, but future versionsof the system will be capable offinding and opening information onthe network. The inspector can berelieved of carrying paper documents,which instead are directly viewed onthe instrument’s tablet. Printeddocuments expire; onlinedocumentation can be managed toprovide only current information.

The new system also has theability to create standardizedinspection workflows. It can automatethe test process, which again is aseemingly small advancement thatcould have tremendous implications.Large organizations with numerous

inspectors at multiple facilities mightfind that their ET is performeddifferently, with slightly differentresults achieved by each individual.By developing a standard practice, thecompany can be confident that all ofits weld inspections, for example, arebeing performed in exactly the sameway, with results that can beduplicated by any one of its testtechnicians.

Through the use of connectivitytechnology, technicians can bringothers into the inspection process asneeded, without having to wait forthem to physically arrive on site,saving time and money. In addition, ahigher-level engineer locatedanywhere in the world can work withthe inspection technician, directing allof his or her actions to achieveunambiguous results. The equipmentalso offers the foundation for a broadrethinking of the process of ETinspection within a company, perhapsrealizing untold means of efficiency oradvancement of skill and corporateknowledge.

Conclusion

Eddy current inspection hasbecome one of today’s most useful andessential modalities for NDE. It hasachieved this status by evolving inreaction to technological advances overthe past decades.

As of 2014, a number of newadvances have been introduced to ET,including networked communications,collaborative features, and anapplication programming interface, thatpromise to expand the horizons of thistest modality dramatically, making itfeasible for a far wider range ofapplications and bringing newtechnicians and operators up to speedmore quickly and efficiently.

Inspection Trends / Summer 2014 19

ROBERT WARD is seniorproject manager for Ultrasonic Testing

(UT) and Electromagnetics (EM)Innovation at GE Measurement andControl, a division of GE Oil & Gas,

Lewistown, Pa.,www.ge-mcs.com/microsites/mentor/.

Ward Feature IT Summer 2014_Layout 1 8/6/14 10:54 AM Page 19