ASTM E571-98(2007)e1
(Practice)Standard Practice for Electromagnetic (Eddy-Current) Examination of Nickel and Nickel Alloy Tubular Products
Standard Practice for Electromagnetic (Eddy-Current) Examination of Nickel and Nickel Alloy Tubular Products
SIGNIFICANCE AND USE
Eddy-current examination is a nondestructive method of locating discontinuities in metallic materials. Signals can be produced by discontinuities originating on either the external or internal surfaces of the tube or by discontinuities totally contained within the wall. Since the density of eddy currents decreases nearly exponentially with increasing distance from the surface nearest the coil, the response to deep-seated defects decreases correspondingly. Phase changes are also associated with changes in depth, allowing the use of phase analysis techniques.
The response from natural discontinuities can be significantly different than that from artificial discontinuities, such as drilled holes or notches. For this reason, sufficient work should be done to establish the sensitivity level and setup required to detect natural discontinuities of consequence to the end use of the product.
Some indications obtained by this method may not be relevant to product quality; for example, an irrelevant indication may be caused by minute dents or tool chatter marks, which are not detrimental to the end use of the product. Irrelevant indications can mask unacceptable discontinuities. Relevant indications are those which result from discontinuities. Any indication that exceeds the rejection level shall be treated as a relevant indication until it can be demonstrated that it is irrelevant.
Generally, eddy-current examination systems are not sensitive to discontinuities adjacent to the ends of the tube (end effect).
Discontinuities such as scratches or seams that are continuous and uniform over the full length of the tube may not always be detected with differential encircling coils or probes scanned along the tube length.
For material that is magnetic, a strong magnetic field shall be placed in the region of the examining coil. A magnetic field may also be used to improve the signal-to-noise ratio in tubing that exhibits slight residual magnetism.
SCOPE
1.1 This practice covers the procedures for eddy-current examination of nickel and nickel alloy tubes. These procedures are applicable for tubes with outside diameters up to 2 in. (50.8 mm), incl, and wall thicknesses from 0.035 to 0.120 in. (0.889 to 3.04 mm), incl. These procedures may be used for tubes beyond the size range recommended, by contractual agreement between the purchaser and the producer.
1.2 The procedures described in this practice make use of fixed encircling test coils or probe systems.
1.3 The values stated in inch-pound units are to be regarded as the standard.
Note 1—For convenience, the term “tube” or “tubular product” will hereinafter be used to refer to both pipe and tubing.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E571 – 98 (Reapproved 2007)
Standard Practice for
Electromagnetic (Eddy-Current) Examination of Nickel and
Nickel Alloy Tubular Products
This standard is issued under the fixed designation E571; 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.
´ NOTE—Editorially changed “examination coils” to “test coils” in December 2007.
1. Scope cation and Certification in Nondestructive Testing
2 ANSI/ASNT-CP-189 ASNT Standard for Qualification and
1.1 This practice covers the procedures for eddy-current
Certification of Nondestructive Testing Personnel
examination of nickel and nickel alloy tubes.These procedures
NAS-410 Certification and Qualification of Nondestructive
are applicable for tubes with outside diameters up to 2 in. (50.8
Personnel (Quality Assurance Committee)
mm), incl, and wall thicknesses from 0.035 to 0.120 in. (0.889
to 3.04 mm), incl. These procedures may be used for tubes
3. Terminology
beyond the size range recommended, by contractual agreement
3.1 Standard terminology relating to electromagnetic ex-
between the purchaser and the producer.
amination may be found in Terminology E1316, Section C,
1.2 The procedures described in this practice make use of
Electromagnetic Testing.
fixed encircling test coils or probe systems.
1.3 The values stated in inch-pound units are to be regarded
4. Summary of Practice
as the standard.
4.1 Examination is usually performed by the use of one of
NOTE 1—For convenience, the term “tube” or “tubular product” will
two general techniques:
hereinafter be used to refer to both pipe and tubing.
4.1.1 Encircling Coil Technique—Examination is per-
1.4 This standard does not purport to address all of the formedbypassingthetubelengthwisethroughacoilenergized
safety concerns, if any, associated with its use. It is the
with alternating current at one or more frequencies. See Fig. 1.
responsibility of the user of this standard to establish appro- The electrical impedance of the coil is modified by the
priate safety and health practices and determine the applica-
proximity of the tube, the tube dimensions, electrical conduc-
bility of regulatory limitations prior to use. tivity, saturating magnetic field, magnetic permeability, and
metallurgical or mechanical discontinuities in the tube. As the
2. Referenced Documents
tube passes through the coil, the changes in electromagnetic
2.1 ASTM Standards:
response caused by these variables in the tube change the coil
E309 Practice for Eddy-Current Examination of Steel Tu-
impedance, which activates an audible or visual signaling
bular Products Using Magnetic Saturation
device or a mechanical marker.
E543 Specification for Agencies Performing Nondestruc-
4.1.2 Probe Coil Technique—Probe coils are positioned in
tive Testing
close proximity to the outside diameter or to the inside
E1316 Terminology for Nondestructive Examinations
diameter, or to both diameter surfaces, of the tubular product
2.2 Other Documents:
beingexaminedasshowninFig.1.Sincetheprobeisgenerally
SNT-TC-1A Recommended Practice for Personnel Qualifi-
small and does not encircle the tube, it examines only a limited
area in the vicinity of the probe. When required to examine the
entire volume of the tubular product, it is common practice to
1 rotate either the tubular product or the probe around the tube.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.07 on Frequently, in the case of welded tubular products, only the
Electromagnetic Method.
weld is examined by scanning along the weld zone.
Current edition approved Dec. 1, 2007. Published January 2008. Originally
4.2 The magnetic permeability of magnetic materials se-
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approved in 1976. Last previous edition approved in 2003 as E571 - 98(2003) .
verely limits the depth of penetration of induced eddy currents.
DOI: 10.1520/E0571-98R07E01.
For ASME Boiler and Pressure Vessel Code applications see related Practice
SE-571 in Section II of that Code.
3 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
the ASTM website. WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E571 – 98 (2007)
contained within the wall. Since the density of eddy currents
decreases nearly exponentially with increasing distance from
the surface nearest the coil, the response to deep-seated defects
decreases correspondingly. Phase changes are also associated
with changes in depth, allowing the use of phase analysis
techniques.
5.2 The response from natural discontinuities can be signifi-
cantly different than that from artificial discontinuities, such as
drilled holes or notches. For this reason, sufficient work should
be done to establish the sensitivity level and setup required to
detect natural discontinuities of consequence to the end use of
the product.
5.3 Some indications obtained by this method may not be
relevant to product quality; for example, an irrelevant indica-
tion may be caused by minute dents or tool chatter marks,
which are not detrimental to the end use of the product.
Irrelevant indications can mask unacceptable discontinuities.
Relevant indications are those which result from discontinui-
ties. Any indication that exceeds the rejection level shall be
treated as a relevant indication until it can be demonstrated that
it is irrelevant.
5.4 Generally, eddy-current examination systems are not
sensitive to discontinuities adjacent to the ends of the tube (end
effect).
5.5 Discontinuities such as scratches or seams that are
continuousanduniformoverthefulllengthofthetubemaynot
always be detected with differential encircling coils or probes
scanned along the tube length.
5.6 For material that is magnetic, a strong magnetic field
shall be placed in the region of the examining coil.Amagnetic
field may also be used to improve the signal-to-noise ratio in
FIG. 1 Encircling-Coil and Probe-Coil Techniques for
tubing that exhibits slight residual magnetism.
Electromagnetic Examination of Tubular Products
6. Basis of Application
Furthermore, the permeability variations inherent in magnetic
6.1 The following criteria may be specified in the purchase
tubular products can cause spurious test results. A useful
specification contractual agreement, or elsewhere, and may
solution to this problem involves the application of a strong
require agreement between the purchaser and the supplier.
external magnetic field in the region of the examining coil or
6.1.1 Acceptance criteria.
probe. This technique, known as magnetic saturation, causes a
6.1.2 Type, dimensions, and number of artificial disconti-
magnetic material to exhibit sufficiently small magnetic char-
nuities to be placed in the reference standard.
acteristics of permeability, hysteresis, etc., so that the material
6.1.3 Extent of examination; that is, full circumference of
under examination is effectively rendered nonmagnetic. When
outside or inside diameter, or both, or weld only, if welded.
achieved, this condition allows an eddy-current system to
6.1.4 Operator qualifications, if required (see 6.1.6 below).
measure and detect electrical resistivity and geometrical varia-
tions (including defects) independent of concurrent variations 6.1.5 Standardization intervals.
in magnetic properties. 6.1.6 If specified in the contractual agreement, personnel
performing examinations to this practice shall be qualified in
NOTE 2—Practice E309 may be used for strongly magnetic materials.
accordance with a nationally recognized NDT personnel quali-
4.2.1 During the examination of slightly magnetic tubing
fication practice or standard such as ANSI/ASNT-CP-189,
the signals resulting from the variation of magnetic permeabil-
SNT-TC-1A, NAS-410, ASNT-ACCP, or a similar document
ity can mask the signals resulting from small imperfections. A
and certified by the certifying agency as applicable. The
magnetic saturation technique can be used to reduce this
practice or standard used and its applicable revision shall be
interference to an acceptable level.
identified in the contractual agreement between the using
parties.
5. Significance and Use
NOTE 3—MIL-STD-410 is canceled and has been replaced with NAS-
5.1 Eddy-current examination is a nondestructive method of
410, however, it may be used with agreement between contracting parties.
locating discontinuities in metallic materials. Signals can be
produced by discontinuities originating on either the external 6.1.7 If specified in the contractual agreement, NDT agen-
or internal surfaces of the tube or by discontinuities totally cies shall be qualified and evaluated in accordance with
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E571 – 98 (2007)
Practice E543.The applicable edition of Practice E543 shall be
specified in the contractual agreement.
7. Apparatus
7.1 Electronic Apparatus—The electronic apparatus shall
be capable of energizing the encircling coils or probes with
alternating current of suitable frequencies and shall be capable
of sensing changes in impedance of the encircling coils or
probes. Equipment may include any appropriate signal pro-
cessing circuits such as a phase discriminator, filter circuits,
etc., as required for the particular application.
7.2 Encircling Coil Assembly—The encircling coil assem-
a = longitudinal notch (milled or EDM)
bly shall consist of one or more electrical coils which encircle
b = transverse notch (milled, filed, or EDM)
the article being examined. The inside
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