ASTM E570-20

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
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Designation: E570 − 15 E570 − 20
Standard Practice for
Flux Leakage Examination of Ferromagnetic Steel Tubular
Products
This standard is issued under the fixed designation E570; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorially corrected 10.1.1 in March 2016.
1. Scope*
1.1 This practice covers the application and standardization of equipment using the flux leakage test method for detection of
outer surface, inner surface, and subsurface surface and inner surface discontinuities in ferromagnetic steel tubular products (Note
1) of uniform cross section, such as seamless and welded tubing. While this method may be sensitive to subsurface discontinuities,
it is not the primary method used to identify these types of discontinuities. A secondary method, such as Ultrasonic Testing, should
be considered for assessment of these types of discontinuities.
NOTE 1—The term “tube” or “tubular product” will be used to refer to both pipe and tubing.
1.2 This practice is intended for use on tubular products having outside diameters from approximately ⁄2 to 24 in. (12.7 to 610
mm) with wall thicknesses to ⁄2 in. (12.7 mm). These techniques have been used for other sizes, however, and may be so specified
upon contractual agreement between the purchaser and the supplier.
1.3 This practice does not establish acceptance criteria; they must be specified by the using parties.
1.4 Units—The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are
mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
E543 Specification for Agencies Performing Nondestructive Testing
E1316 Terminology for Nondestructive Examinations
2.2 Other Documents:
SNT-TC-1A Recommended Practice for Personnel Qualification and Certification of Nondestructive Testing Personnel
ANSI/ASNT CP-189 ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel
NAS-410 NAS Certification and Qualification of Nondestructive Personnel (Quality Assurance Committee)
ISO 9712 Non-destructive Testing—Qualification and Certification of NDT Personnel
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.07 on Electromagnetic
Method.
Current edition approved June 1, 2015June 1, 2020. Published July 2015June 2020. Originally approved in 1976. Last previous edition approved in 20092015 as
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E570 - 09.E570 – 15 . DOI: 10.1520/E0570-15E01.10.1520/E0570-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from Aerospace Industries Association of America, Inc., 1250 Eye St., NW, Washington, DC 20005.(AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA
22209, http://www.aia-aerospace.org.
Available from International Organization for Standardization (ISO), 1, ch. de 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
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E570 − 20
3. Terminology
3.1 Definitions of terms relating to flux leakage examination are provided in Terminology E1316.
4. Summary of Practice
4.1 This method consists of the following steps:
4.1.1 The tube wall is magnetized at the area under examination to a proper level approaching magnetic saturation.
NOTE 2—Tubes subjected to magnetic inspections can retain various strengths and configuration of residual magnetic fields depending upon the
magnetization technique. If the residual field resulting from a given technique can interfere with subsequent applications of the tube, then a supplemental
demagnetization process may be required.
4.1.2 A flux sensor containing magnetic transducers is placed on or above the outside surface of the tube in the magnetized area.
4.1.3 Either the tube or the flux sensor is moved at a constant speed in the direction of the magnetic field so that the sensor scans
the entire surface of the tube.
4.1.4 Each magnetic transducer in the flux sensor is connected to an electronic console which amplifies, filters, and
electronically processes the signals such that significant discontinuities are indicated (visually, audibly), and marked with paint,
or automatically removed from the production line, or both.
4.1.5 A suitable means for assuring near magnetic saturation of the product (subject to periodic check or calibration) must be
provided as part of the examination to verify the capability of detection of outside diameter and inside diameter discontinuities.
5. Significance and Use
5.1 This practice outlines a procedure for examining ferromagnetic tubular products using the flux leakage method. If properly
applied, this method is capable of detecting the presence and location of significant longitudinally or transversely oriented
discontinuities, such as pits, scabs, slivers, gouges, roll-ins, laps, seams, cracks, holes, and improper welds in ferromagnetic tubes
under inspection. In addition, the severity of a discontinuity may be estimated and a rejection level set with respect to the
magnitude of the electromagnetic indication produced by the discontinuity.
5.2 The response from natural discontinuities can be significantly different from the response for artificial discontinuities, such
as drilled holes or notches of equivalent depth. For this reason, sufficient work should be done to determine the conditions
necessary to detect and mark natural discontinuities whose characteristics will adversely affect the serviceability of the tube, in
order to establish acceptance criteria between the supplier and purchaser.
6. Basis of Application
6.1 The following criteria may be specified in the purchase specification, contractual agreement, or elsewhere, and may require
agreement between the purchaser and supplier:
6.1.1 Acceptance criteria.
6.1.2 Type, dimensions, location, and number of artificial discontinuities to be placed on the reference standard.
6.1.3 Size and type of tubing to be examined.
6.1.4 Extent of examination (that is, full length, weld zone only if welded, etc.).
6.1.5 Disposition of material with discontinuity indications.
6.1.6 Methods of verifying dimensions of artificial discontinuities and allowable tolerances.
6.1.7 Time of inspection, that is, the point(s) in the manufacturing process at which the material will be inspected.
6.1.8 Nondestructive testing (NDT) personnel shall be qualified in accordance with a nationally recognized NDT personnel
qualification practice or standard such as ANSI/ASNT CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a similar document. The
practice or standard used and its applicable revision shall be specified in the purchase specification or contractual agreement
between the using parties.
6.1.9 If specified in the purchase specification or contractual agreement, NDT agencies shall be evaluated and qualified as
described in PracticeSpecification E543. The applicable edition of PracticeSpecification E543 shall be identified in the purchase
specification or contractual agreement between the using parties.
7. Interferences
7.1 There are some manufacturing processes that produce tubing with surface conditions that could interfere with or obscure
signals related to inner surface discontinuities. In the examination of heavy-walled tubing having these conditions, the ability to
examine reliably for inner surface discontinuities may be affected.
7.2 When examining tubes with large rapid surface variations, false signals may be caused by the sensors bouncing along the
surface of the tubes.
7.3 For active pole magnetizing systems, a small air gap between the magnetizing system and material under examination could
cause a heavy accumulation of scale buildup on the pole pieces.
E570 − 20
DETECTION OF LONGITUDINAL DISCONTINUITIES
8. Apparatus
8.1 Rotary Mechanism—The rotary mechanism shall be capable of rotating a magnetizing system or flux leakage sensors, or
both, in unison around tubing that is being translated axially through the mechanism, thereby producing a helical scan over the
surface. Good examination practices require that the pole pieces of the magnetizing system rotate uniformly about the tube and
that the flux sensor ride on the tube or be spaced uniformly above the surface of the tube during rotation.
8.2 Spin Feed Mechanism—The spin feed mechanism shall be capable of positioning a magnetizing system or flux leakage
sensors, or both, on or near the surface of a translating rotating tube such that there is a uniform spacing between the pole pieces
of the magnetizing system and the tube. The flux leakage sensors shall ride on the surface of the tube or be held uniformly from
the surface of the tube during examination.
8.3 Magnetizing System:
8.3.1 An active field magnetizing system consists of a suitable means of applying a strong adjustable transverse magnetic field
to the region of the tube under the flux sensors and shall be capable of bringing that region of the tube to near saturation. Typical
systems employ either permanent magnets or controllable electromagnets. If permanent magnets are used, a means shall be
provided to adjust the spacing of the pole pieces in order to reach the proper magnetization level. Refer to Section 13 for
application of longitudinal magnetic fields.
8.3.2 A residual field magnetizing system consists of a means of applying a circular residual magnetic field to an entire tube
before the tube is inspected. Typical systems employ a centrally positioned conducting rod through which a high direct current is
passed; alternatively, the current may be conducted through the tube itself. The current produces a circular active magnetic field
which is concentric with the current distribution. When the current ceases, there remains a residual magnetic field which is circular,
concentric with the tube, and wholly contained within the tube wall.
8.4 Flux Leakage Sensors:
8.4.1 The flux sensor shall consist of magnetic field transducers that respond to variations in magnetic flux density. These
sensors generally consist of one of the following types: electromagnetic coils, Hall probes, magneto diodes, magnistors, or
magnetoresistors. These sensors are normally used to detect the flux leakage directly from the discontinuity in the tube; however,
they may also be used to detect flux leakage patterns that have been transferred from the tube to a strip of magnetic tape. The flux
sensors should be of sufficient number and length so as to provide 100 % coverage while scanning the tube surface to be examined
at the desired examination speed. Their location (with respect to the magnetic pole pieces and the tubular product) should result
in maximum response to the leakage field caused by a discontinuity in the tubular product.
8.4.2 The depth and orientation of a discontinuity below the outside surface will affect the magnitude of the signal
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