ASTM E426-98
(Practice)Standard Practice for Electromagnetic (Eddy-Current) Examination of Seamless and Welded Tubular Products, Austenitic Stainless Steel and Similar Alloys
Standard Practice for Electromagnetic (Eddy-Current) Examination of Seamless and Welded Tubular Products, Austenitic Stainless Steel and Similar Alloys
SCOPE
1.1 This practice covers procedures that may be followed for eddy-current examination of seamless and welded tubular products made of stainless steel and similar alloys such as nickel alloys. Austenitic chromium-nickel stainless steels, which are generally considered to be nonmagnetic, are specifically covered as distinguished from the martensitic and ferritic straight chromium stainless steels which are magnetic.
1.2 This practice is intended as a guide for eddy-current examination both seamless and welded tubular products using either an encircling coil or a probe-coil technique. Coils and probes are available that can be used inside the tubular product; however, their use is not specifically covered in this document. This type of examination is usually employed only to examine tubing which has been installed such as in a heat exchanger.
1.3 This practice covers the examination of tubular products ranging in diameter from 0.125 to 5 in. (3.2 to 127.0 mm) and wall thicknesses from 0.005 to 0.250 in. (0.127 to 6.4 mm).
1.4 The values stated in inch-pound units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety problems, 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 426 – 98
Standard Practice for
Electromagnetic (Eddy-Current) Examination of Seamless
and Welded Tubular Products, Austenitic Stainless Steel
and Similar Alloys
This standard is issued under the fixed designation E 426; 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 (e) indicates an editorial change since the last revision or reapproval.
This specification has been approved for use by agencies of the Department of Defense.
1. Scope SNT-TC-1A Recommended Practice for Personnel Qualifi-
cation and Certification in Nondestructive Testing
1.1 This practice covers procedures that may be followed
ANSI/ASNT CP-189 ASNT Standard for Qualification and
for eddy-current examination of seamless and welded tubular
Certification of Nondestructive Testing Personnel
products made of stainless steel and similar alloys such as
MIl-STD-410E Nondestructive Testing Personnel Qualifi-
nickel alloys. Austenitic chromium-nickel stainless steels,
cation and Certification
which are generally considered to be nonmagnetic, are specifi-
NAS-410 NAS Certification and Qualification of Nonde-
cally covered as distinguished from the martensitic and ferritic
structive Personnel (Quality Assurance Committee)
straight chromium stainless steels which are magnetic.
1.2 This practice is intended as a guide for eddy-current
3. Terminology
examination both seamless and welded tubular products using
3.1 Standard terminology relating to electromagnetic ex-
either an encircling coil or a probe-coil technique. Coils and
amination may be found in Terminology E 1316, Section C,
probes are available that can be used inside the tubular product;
Electromagnetic Testing.
however, their use is not specifically covered in this document.
This type of examination is usually employed only to examine
4. Summary of Practice
tubing which has been installed such as in a heat exchanger.
4.1 The test is conducted using one of two general tech-
1.3 This practice covers the examination of tubular products
niques shown in Fig. 1. One of these techniques employs one
ranging in diameter from 0.125 to 5 in. (3.2 to 127.0 mm) and
or more exciter and sensor coils which encircle the pipe or tube
wall thicknesses from 0.005 to 0.250 in. (0.127 to 6.4 mm).
and through which the tubular product to be inspected is
1.4 The values stated in inch-pound units are to be regarded
passed. Some circuit configurations employ separate exciter
as the standard.
and sensor coils; whereas other configurations employ one or
1.5 This standard does not purport to address all of the
more coils that concurrently function as both exciters and
safety problems, if any, associated with its use. It is the
sensors. Alternating current passes through the exciting coil
responsibility of the user of this standard to establish appro-
which by reason of its proximity induces current in the tubular
priate safety and health practices and determine the applica-
product. The sensor coil detects the resultant electromagnetic
bility of regulatory limitations prior to use.
flux related to these currents. The presence of discontinuities in
2. Referenced Documents the tubular product will affect the normal flow of currents and
this change is detected by the sensor. The encircling coil
2.1 ASTM Standards:
technique is capable of inspecting the entire 360-deg expanse
E 543 Practice for Agencies Performain Nondestructive
3 of the tubular product.
Testing
3 4.2 Another technique employs a probe coil with one or
E 1316 Terminology for Nondestructive Testing
more exciters and sensors which is brought in close proximity
2.2 Other Documents:
of the surface of the tubular product to be examined. Since the
This practice is under the jurisdiction of ASTM Committee E-7 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.07 on
Electromagnetic Methods. Available from American Society for Nondestructive Testing, 1711 Arlingate
Current edition approved Dec. 10, 1998. Published February 1999. Originally Plaza, P.O. Box 28518, Columbus, OH 43228–0518.
published as E 426 – 71. Last previous edition E 426 – 92. Available from Standardization Documents Order Desk, Bldg. 4, Section D,
For ASME Boiler and Pressure Vessel Code applications see related Practice 700 Robbins Ave., Phila., PA 19111–5904, Attn: NPODS.
SE-426 in Section II of that Code. Available from Aerspace Industries Association of America, Inc., 1250 Eye
Annual Book of ASTM Standards, Vol 03.03. Street, N.W., Washington, DC 20005.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E426–98
accordance with a nationally recognized NDT personnel quali-
fication practice or standard such as ANSI/ASNT-CP-189,
SNT-TC-1A, MIL-STD-410E, NAS-410, ASNT-ACCP, or a
similar document and certified by the certifying agency, as
applicable. The practice or standard used and its applicable
revision shall be identified in the contractual agreement be-
tween the using parties.
NOTE 1—MIL-STD-410 is canceled and has been replaced with NAS-
410, however, it may be used with agreement between contracting parties.
6.2 If specified in the contractual agreement, NDT agencies
shall be qualified and evaluated in accordance with Practice
E 543. The applicable edition of Practice E 543 shall be
specified in the contractual agreement.
7. Apparatus
7.1 Electronic Apparatus—The electronic apparatus shall
be capable of energizing the test coils or probes with alternat-
ing currents of suitable frequencies and shall be capable of
sensing the changes in the electromagnetic response of the
sensors. Equipment may include a detector, phase discrimina-
tor, filter circuits, modulation circuits, magnetic-saturation
devices, recorders, and signaling devices as required for the
particular application.
7.2 Test Coils—Test coils shall be capable of inducing
current in the tube and sensing changes in the electrical
characteristics of the tube.
NOTE 2—Fill factor effect is an important consideration since coupling
variations can affect the test significantly.
7.3 Probe Coils—Probe coils shall be capable of inducing
FIG. 1 Sketch Showing Encircling-Coil and Probe-Coil
current in the tube and sensing changes in the electrical
Techniques for Electromagnetic Examining of Tubular Products
characteristics of the tube (Note 3). Probes generally consist of
an exciting coil and sensing coil or Hall element mounted in a
probe is generally small and does not encircle the article being
common holder. A Hall element is a semiconductor that by
examined, it examines only a limited area in the vicinity of the
reason of the Hall effect is capable of responding in a manner
probe. If it is desired to examine the entire volume of the
directly proportional to magnetic-flux density. However, when
tubular product, it is common practice to either rotate the
used with an exciting coil, it should be remembered that
tubular product or the probe. In the case of welded tubular
eddy-current flow is influenced by the excitation frequency.
products frequently only the weld is examined by scanning
NOTE 3—Lift-off effect is an important consideration since coupling
along the weld zone.
variations can affect the test significantly.
5. Significance and Use
7.4 Driving Mechanism—A mechanical device capable of
5.1 Eddy-current testing is a nondestructive method of passing the tube through the test coil or past the probe. It shall
locating discontinuities in a product. Changes in electromag- operate at a uniform speed with minimum vibration of coil,
netic response caused by the presence of discontinuities are probe, or tube and maintain the article being examined in
detected by the sensor, amplified and modified in order to proper register or concentricity with the probe or test coil.
actuate audio or visual indicating devices, or both, or a Where required, the mechanism shall be capable of uniformly
mechanical marker. Signals can be caused by outer surface, rotating the tube or probe.
inner surface, or subsurface discontinuities. The eddy-current 7.5 Reference Standard—The standard used to adjust the
test is sensitive to many factors that occur as a result of sensitivity setting of the apparatus shall be sound and of the
processing (such as variations in conductivity, chemical com- same nominal alloy, temper, and nominal dimensions as the lot
position, permeability, and geometry) as well as other test of tubes or pipes to be tested on a production basis. It shall be
factors not related to the tubing. Thus, all received indications of sufficient length to permit the required spacing of the
are not necessarily indicative of defective tubing.
artificial discontinuities (at least 4 ft, and preferably longer).
Artificial discontinuities made in the tube or pipe shall be
6. Basis of Application
centered as nearly as possible on one inside or outside diameter
6.1 If specified in the contractual agreement, personnel surface of the tube and shall preferably be of one of the
performing examinations to this practice shall be qualified in following types:
NOTICE: This standard has either be
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