ASTM E690-15(2020)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E690 − 15 (Reapproved 2020)
Standard Practice for
In Situ Electromagnetic (Eddy Current) Examination of
Nonmagnetic Heat Exchanger Tubes
This standard is issued under the fixed designation E690; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* E543 Specification for Agencies Performing Nondestructive
Testing
1.1 Thispracticedescribesprocedurestobefollowedduring
E1316 Terminology for Nondestructive Examinations
eddy current examination (using an internal, probe-type, coil
2.2 Other Documents:
assembly) of nonmagnetic tubing that has been installed in a
SNT-TC-1A Recommended Practice for Personnel Qualifi-
heat exchanger. The procedure recognizes both the unique
cation and Certification in Nondestructive Testing
problems of implementing an eddy current examination of
ANSI/ASNT-CP-189 ASNT Standard for Qualification and
installed tubing, and the indigenous forms of tube-wall dete-
Certification of Nondestructive Testing Personnel
rioration which may occur during this type of service. The
NAS-410 NAS Certification and Qualification of Nonde-
document primarily addresses scheduled maintenance inspec-
structive Personnel (Quality Assurance Committee)
tion of heat exchangers, but can also be used by manufacturers
ISO 9712 Non-destructive Testing—Qualification and Cer-
ofheatexchangers,eithertoexaminetheconditionofthetubes
tification of NDT Personnel
after installation, or to establish baseline data for evaluating
subsequent performance of the product after exposure to
3. Terminology
various environmental conditions. The ultimate purpose is the
detection and evaluation of particular types of tube integrity
3.1 Standard terminology relating to electromagnetic ex-
degradation which could result in in-service tube failures.
amination may be found in Terminology E1316, Section C,
Electromagnetic Testing.
1.2 This practice does not establish acceptance criteria; they
must be specified by the using parties.
4. Summary of Practice
1.3 This standard does not purport to address all of the
4.1 The examination is performed by passing an eddy
safety concerns, if any, associated with its use. It is the
current probe through each tube. These probes are energized
responsibility of the user of this standard to establish appro-
with alternating currents at one or more frequencies. The
priate safety, health, and environmental practices and deter-
electrical impedance of the probe is modified by the proximity
mine the applicability of regulatory limitations prior to use.
of the tube, the tube dimensions, electrical conductivity,
1.4 This international standard was developed in accor-
magnetic permeability, and metallurgical or mechanical dis-
dance with internationally recognized principles on standard-
continuities in the tube. During passage through the tube,
ization established in the Decision on Principles for the
changes in electromagnetic response caused by these variables
Development of International Standards, Guides and Recom-
in the tube produce electrical signals which are processed so as
mendations issued by the World Trade Organization Technical
to produce an appropriate combination of visual displays,
Barriers to Trade (TBT) Committee.
alarms, or temporary or permanent records, or combination
2. Referenced Documents thereof, for subsequent analysis.
2.1 ASTM Standards:
5. Significance and Use
5.1 Eddy current testing is a nondestructive method that can
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
be used to locate discontinuities in tubing made of materials
structive Testing and is the direct responsibility of Subcommittee E07.07 on
Electromagnetic Method.
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved
in 1979. Last previous edition approved in 2015 as E690 – 15. DOI: 10.1520/ AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
E0690-15R20. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
Standards volume information, refer to the standard’s Document Summary page on Available from International Organization for Standardization (ISO), 1, ch. de
the ASTM website. la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E690 − 15 (2020)
that conduct electricity. Signals can be produced by disconti- 6.1.14 If specified in the contractual agreement, personnel
nuities located either on the inner or outer surfaces of the tube, performing examinations to this practice shall be qualified in
or by discontinuities totally contained within the tube wall. accordance with a nationally recognized NDT personnel quali-
When using an internal probe, the density of eddy currents in fication practice or standard such as ANSI/ASNT-CP-189,
the tube wall decreases very rapidly as the distance from the SNT-TC-1A, NAS-410, ISO 9712 or a similar document and
internalsurfaceincreases;thustheamplitudeoftheresponseto certifiedbythecertifyingagency,asapplicable.Thepracticeor
outer surface discontinuities decreases correspondingly. standard used and its applicable revision shall be identified in
the contractual agreement between the using parties.
5.2 Some indications obtained by this method may not be
6.1.15 If specified in the contractual agreement, NDT agen-
relevant to product quality. For example, an irrelevant signal
cies shall be qualified and evaluated in accordance with
may be caused by metallurgical or mechanical variations that
Specification E543. The applicable edition of Specification
are generated during manufacture but that are not detrimental
E543 shall be specified in the contractual agreement.
to the end use of the product. Irrelevant indications can mask
unacceptable discontinuities occurring in the same area. Rel-
7. Apparatus
evant indications are those that result from nonacceptable
discontinuities.Any indication above the reject level, which is
7.1 Electronic Apparatus:
believed to be irrelevant, shall be regarded as unacceptable
7.1.1 The electronic apparatus shall be capable of energiz-
until it is proven to be irrelevant. For tubing installed in heat
ing the probe coils with alternating currents of suitable
exchangers, predictable sources of irrelevant indications are
frequencies, and shall be capable of sensing changes in the
lands (short unfinned sections in finned tubing), dents,
electromagnetic response of the probes. It is important to note
scratches, tool chatter marks, or variations in cold work.
that a differential coil probe system tends to maximize the
Rolling tubes into the supports may also cause irrelevant
response from abrupt changes along the tube length, while a
indications, as may the tube supports themselves. Eddy current
single coil probe system usually responds to all changes.
examination systems are generally not able to separate the
7.1.2 Since many gradual changes are irrelevant, a differen-
indication generated by the end of the tube from indications of
tial coil system may permit higher gain than an absolute coil
discontinuities adjacent to the ends of the tube (end effect).
system, which enhances the response to small, short defects.
Therefore, this examination may not be valid at the boundaries
Electrical signals produced in this manner may be processed so
of the tube sheets.
as to actuate an audio or visual readout, or both. When
necessary, these signals may also be further processed to
6. Basis of Application
produce a permanent record. The apparatus should have some
6.1 The following criteria may be specified in the purchase means of providing relative quantitative information based
specification, contractual agreement, or elsewhere, and may upon the amplitude or phase of the electrical signal, or both.
require agreement between the purchaser and the supplier. This may take many forms, including calibrated sensitivity or
6.1.1 Type of eddy current system, and probe (coil assem- attenuation controls, multiple alarm thresholds, or analog or
digital readouts, or combination thereof.
bly) configuration,
6.1.2 Location of heat exchanger, if applicable,
7.2 Readout Devices, which require operator monitoring,
6.1.3 Size, material, and configuration of tubes to be
such as an oscilloscope or impedance plane presentation, may
examined,
be used when necessary to augment the alarm circuits. This
6.1.4 Extentofexamination,thatis,length,tubesheetareas,
may be necessary, for example, to find small holes, indications
straight length only, minimum radius of bends, etc.,
of which tend to be nearly in phase with the response from
6.1.5 Time of examination, that is, the date and location of
lands in skip-fin tubing. Since the lands cause very large
the intended examination, and the expected environmental
signals to occur, phase discrimination may not prevent irrel-
conditions,
evant alarms from tube support, if the alarm is set to reject the
6.1.6 The source and type of material to be used for
hole. By observing an oscilloscope or oscillograph, however,
fabricating the reference standard, the ability to detect this type of defect may be improved,
6.1.7 The type(s), method of manufacture, location, especially in areas between the tube supports.
dimensions, and number of artificial discontinuities to be
7.3 Examination Coils—Examination coils shall be capable
placed on the reference standard,
of inducing current in the tube and sensing changes in the
6.1.8 Allowable tolerances for artificial discontinuities, and
electrical characteristics of the tube. The examination coil
methods for verifying compliance,
diameter shall be selected to yield the largest practical fill-
6.1.9 Methods for determining the extent of end effect,
factor. The configuration of the examination coils may permit
6.1.10 Maximum time interval between equipment refer-
sensing both small, localized conditions, which change rapidly
ence checks,
along the tube length, such as pitting or stress corrosion cracks,
6.1.11 Criteria to be used in interpreting and classifying
and those which may change slowly along the tube length or
observed indications,
from tube to tube, such as steam cutting, mechanical erosion,
6.1.12 Disposition of examination records and reference
ormetallurgicalchanges.Thechoiceofcoildiametershouldbe
standard,
based upon requirements judged to be necessary for the
6.1.13 Contents of examination report, and particular examination situation.
E690 − 15 (2020)
7.4 Single-Coil or Differential-Coil Probe Systems: The tube-wall deviations in a particular heat exchanger can be
7.4.1 Single-Coil Probe Systems—In a single-coil probe monitored over subsequent shutdowns, or be corrected, at the
discretion of the user or through administration of a code
system, the signal obtained from the interaction between the
examinationcoil,andtheportionofthetestspecimenwithinits specific to a class of users. Specific types and sizes of artificial
discontinuities should be chosen to reflect both the purpose of
influence is often balanced against an off-line reference coil in
a similar specimen, often with the aid of electrical
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