1、Designation: E571 12Standard Practice forElectromagnetic (Eddy-Current) Examination of Nickel andNickel Alloy Tubular Products1This standard is issued under the fixed designation E571; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice2covers the procedures for eddy-currentexamination of nickel and nickel alloy tubes. These
3、 proceduresare applicable for tubes with outside diameters up to 2 in. (50.8mm), incl, and wall thicknesses from 0.035 to 0.120 in. (0.889to 3.04 mm), incl. These procedures may be used for tubesbeyond the size range recommended, by contractual agreementbetween the purchaser and the producer.1.2 The
4、 procedures described in this practice make use offixed encircling test coils or probe systems.1.3 UnitsThe values stated in inch-pound units are to beregarded as standard. The values given in parentheses aremathematical conversions to SI units that are provided forinformation only and are not consi
5、dered standard.NOTE 1For convenience, the term “tube” or “tubular product” willhereinafter be used to refer to both pipe and tubing.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establ
6、ish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E309 Practice for Eddy-Current Examination of Steel Tu-bular Products Using Magnetic SaturationE543 Specification for Agencies Performing No
7、ndestruc-tive TestingE1316 Terminology for Nondestructive Examinations2.2 Other Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing4ANSI/ASNT-CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel4NAS-
8、410 Certification and Qualification of NondestructivePersonnel (Quality Assurance Committee)53. Terminology3.1 Standard terminology relating to electromagnetic testingmay be found in Terminology E1316, Section C, Electromag-netic Testing.4. Summary of Practice4.1 Examination is usually performed by
9、the use of one oftwo general techniques:4.1.1 Encircling Coil TechniqueExamination is per-formed by passing the tube lengthwise through a coil energizedwith alternating current at one or more frequencies. See Fig. 1.The electrical impedance of the coil is modified by theproximity of the tube, the tu
10、be dimensions, electrical conduc-tivity, saturating magnetic field, magnetic permeability, andmetallurgical or mechanical discontinuities in the tube. As thetube passes through the coil, the changes in electromagneticresponse caused by these variables in the tube change the coilimpedance, which acti
11、vates an audible or visual signalingdevice or a mechanical marker.4.1.2 Probe Coil TechniqueProbe coils are positioned inclose proximity to the outside diameter or to the insidediameter, or to both diameter surfaces, of the tubular productbeing examined as shown in Fig. 1. Since the probe is general
12、lysmall and does not encircle the tube, it examines only a limitedarea in the vicinity of the probe. When required to examine theentire volume of the tubular product, it is common practice torotate either the tubular product or the probe around the tube.Frequently, in the case of welded tubular prod
13、ucts, only theweld is examined by scanning along the weld zone. In the casewhere the tubular products are joined by welding and the probeis rotated, the probe is orbited about the central axis of the tubesuch that a circumferential examination of the tube and/or weld1This practice is under the juris
14、diction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Method.Current edition approved Aug. 1, 2012. Published September 2012. Originallyapproved in 1976. Last previous edition approved in 2007 as E571 - 98(2007). DOI:10.152
15、0/E0571-12.2For ASME Boiler and Pressure Vessel Code applications see related PracticeSE-571 in Section II of that Code.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
16、 to the standards Document Summary page onthe ASTM website.4Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.5Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suit
17、e 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.1*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.may be made. The depth of penetration of the interrogatingm
18、agnetic fields into the tubular product may be smaller for thistype of probe coil compared to the encircling coil.4.2 The magnetic permeability of magnetic materials se-verely limits the depth of penetration of induced eddy currents.Furthermore, the permeability variations inherent in magnetictubula
19、r products can cause spurious test results. A usefulsolution to this problem involves the application of a strongexternal magnetic field in the region of the examining coil orprobe. This technique, known as magnetic saturation, causes amagnetic material to exhibit sufficiently small magnetic char-ac
20、teristics of permeability, hysteresis, etc., so that the materialunder examination is effectively rendered nonmagnetic. Whenachieved, this condition allows an eddy-current system tomeasure and detect electrical resistivity and geometrical varia-tions (including defects) independent of concurrent var
21、iationsin magnetic properties.NOTE 2Practice E309 may be used for strongly magnetic materials.4.2.1 During the examination of slightly magnetic tubingthe signals resulting from the variation of magnetic permeabil-ity can mask the signals resulting from small imperfections. Amagnetic saturation techn
22、ique can be used to reduce thisinterference to an acceptable level.5. Significance and Use5.1 Eddy-current testing is a nondestructive method oflocating discontinuities in metallic materials. Signals can beproduced by discontinuities originating on either the externalor internal surfaces of the tube
23、 or by discontinuities totallycontained within the wall. Since the density of eddy currentsdecreases nearly exponentially with increasing distance fromthe surface nearest the coil, the response to deep-seated defectsdecreases correspondingly. Phase changes are also associatedwith changes in depth, a
24、llowing the use of phase analysistechniques.5.2 The response from natural discontinuities can be signifi-cantly different than that from artificial discontinuities, such asdrilled holes or notches. For this reason, sufficient work shouldbe done to establish the sensitivity level and setup required t
25、odetect natural discontinuities of consequence to the end use ofthe product.5.3 Some indications obtained by this method may not berelevant 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 p
26、roduct.Irrelevant indications can mask unacceptable discontinuities.Relevant indications are those which result from discontinui-ties. Any indication that exceeds the rejection level shall betreated as a relevant indication until it can be demonstrated thatit is irrelevant.5.4 Generally, eddy-curren
27、t examination systems are notsensitive to discontinuities adjacent to the ends of the tube (endeffect).5.5 Discontinuities such as scratches or seams that arecontinuous and uniform over the full length of the tube may notalways be detected with differential encircling coils or probesscanned along th
28、e tube length.5.6 For material that is magnetic, a strong magnetic fieldshall be placed in the region of the examining coil. A magneticfield may also be used to improve the signal-to-noise ratio intubing that exhibits slight residual magnetism.6. Basis of Application6.1 The following criteria may be
29、 specified in the purchasespecification contractual agreement, or elsewhere, and mayrequire agreement between the purchaser and the supplier.6.1.1 Acceptance criteria.6.1.2 Type, dimensions, and number of artificial disconti-nuities to be placed in the reference standard.6.1.3 Extent of examination;
30、 that is, full circumference ofoutside or inside diameter, or both, or weld only, if welded.6.1.4 Operator qualifications, if required (see 6.1.6 below).6.1.5 Standardization intervals.6.1.6 If specified in the contractual agreement, personnelperforming examinations to this practice shall be qualifi
31、ed inaccordance with a nationally recognized NDT personnel quali-fication practice or standard such as ANSI/ASNT-CP-189,SNT-TC-1A, NAS-410, ASNT-ACCP, or a similar documentand certified by the certifying agency as applicable. Thepractice or standard used and its applicable revision shall beidentifie
32、d in the contractual agreement between the usingparties.FIG. 1 Encircling-Coil and Probe-Coil Techniques forElectromagnetic Examination of Tubular ProductsE571 122NOTE 3MIL-STD-410 is canceled and has been replaced with NAS-410, however, it may be used with agreement between contracting parties.6.1.
33、7 If specified in the contractual agreement, NDT agen-cies shall be qualified and evaluated in accordance withSpecification E543. The applicable edition of SpecificationE543 shall be specified in the contractual agreement.7. Apparatus7.1 Electronic ApparatusThe electronic apparatus shallbe capable o
34、f energizing the encircling coils or probes withalternating current of suitable frequencies and shall be capableof sensing changes in impedance of the encircling coils orprobes. Equipment may include any appropriate signal pro-cessing circuits such as a phase discriminator, filter circuits,etc., as
35、required for the particular application.7.2 Encircling Coil AssemblyThe encircling coil assem-bly shall consist of one or more electrical coils which encirclethe article being examined. The inside geometry of the coilsshould closely approximate the surface geometry of the speci-men so that when the
36、specimen is passed through the coils allpoints on the outer circumference of the specimen are effec-tively equidistant from, and in close proximity to, the innersurfaces of the examining coils.7.3 Probe AssemblyThe probe coil assembly normallycontains an exciting coil and a sensor, although in some
37、casesthe exciter and the sensor are one and the same. The sensormay consist of one or more electrical coils or a semiconductordevice that responds to variations in electromagnetic fluxdensity. Good examination practices require that the spacingbetween the probe coil assembly and the tube being exami
38、nedbe both small and uniform.7.4 Driving MechanismThe mechanical device capable ofpassing the tube through the examining coil or past the probeshall operate at a uniform speed with minimum vibration ofcoil, probe, or tube and shall maintain the article beingexamined in proper register or concentrici
39、ty with the probe orcoil. Where required, the mechanism shall be capable ofrotating the tube or probe with a uniform rotational speed.8. Reference Standard8.1 The standard used to adjust the sensitivity of theapparatus shall be free of interfering discontinuities and of thesame nominal alloy, temper
40、, and nominal dimensions as the lotof tubes to be examined on a production basis. It shall be ofsufficient length to permit the spacing of artificial discontinui-ties to provide good signal resolution, and to be mechanicallystable while in the examining position in the apparatus.Artificial discontin
41、uities placed in the tube shall be of thefollowing types (see Fig. 2):8.1.1 NotchLongitudinal or transverse notches, or both,may be produced by milling, filing, EDM (Electric DischargeMachine) or other suitable means. Notches may be placed onthe outer, inner, or both surfaces of the reference standa
42、rd.NOTE 4Longitudinal notch standards are normally used when exam-ining with rotating probe systems.8.1.2 HoleThe holes shall be drilled radially partially orcompletely through the tube wall without causing permanentdistortion of the tube wall.8.1.3 Hole size and notch configuration (type, orientati
43、on,length, depth, size, etc.) influence the eddy-current response.These factors, plus the method and tolerances used in theirmeasurement, shall be as specified in the agreement betweenthe supplier and the purchaser.9. Adjustment and Standardization of ApparatusSensitivity9.1 Select the apparatus, ex
44、amining frequency, coil or probeconfiguration or both, magnetic saturation system if used,phase discrimination, and other circuitry, as well as speed ofexamination. Demonstrate the system capability for detectingartificial discontinuities of the size and type of interest atproduction speed.9.2 Fabri
45、cate the applicable reference standard in accor-dance with the agreement between the purchaser and the tubingsupplier. Discard and replace the tube used as the referencestandard when erroneous signals are produced from mechani-cal, metallurgical or other damage to the reference standard.9.3 Rotate t
46、he reference standard in either 90 or 120increments to determine the location of the electrical center inthe examining coil. Mechanically adjust the position of thetube within the coil to obtain nearly equal responses from theartificial discontinuities regardless of their circumferentialorientation.
47、9.4 The length of tubing not examined due to the end effectmay be determined by selecting a tube of low backgroundnoise and making a series of holes or notches at appropriateintervals near the end of this special tube. See Fig. 3. Pass thetube through the examination setup at the production speedwit
48、h the artificial discontinuities end first, and then with theartificial discontinuities end last. Determine the distance fromthe tube end to the point at which the signal response fromsuccessive discontinuities is uniform with a recording devicesuch as a pen recorder or memory oscilloscope. A signal
49、suppression method (photo relay, mechanical switches, orproximity devices are commonly used) may be used to permitexamination only when the length of tubing exhibiting uniformsignals is within the test coil. The section of tube passingthrough the test coil representing the end effect is not exam-ined.9.5 As an option to 9.4, the length of tubing representing theend effect may be determined by selecting a tube of lowa = longitudinal notch (milled or EDM)b = transverse notch (milled, filed, or EDM)c = drilled hole (radially through one wall)FIG. 2 Various Types of Artifi
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