1、Designation: E 571 98 (Reapproved 2003)e1Standard Practice forElectromagnetic (Eddy-Current) Examination of Nickel andNickel Alloy Tubular Products1This standard is issued under the fixed designation E 571; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes made throughout the standard in July 2003.1. Scope1.1 This practice2c
3、overs the procedures for eddy-currentexamination of nickel and nickel alloy tubes. These 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 r
4、ange recommended, by contractual agreementbetween the purchaser and the producer.1.2 The procedures described in this practice make use offixed encircling coils or probe systems.1.3 The values stated in inch-pound units are to be regardedas the standard.NOTE 1For convenience, the term “tube” or “tub
5、ular 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 establish appro-priate safety and health practices and determine th
6、e applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 309 Practice for Eddy-Current Examination of Steel Tu-bular Products Using Magnetic Saturation3E 543 Practice for Agencies Performing NondestructiveTesting3E 1316 Terminology for Nondestructive Examin
7、ations32.2 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-410 Certification and Qualification of NondestructivePersonnel
8、(Quality Assurance Committee)53. Terminology3.1 Standard terminology relating to electromagnetic ex-amination may be found in Terminology E 1316, Section C,Electromagnetic Testing.4. Summary of Practice4.1 Examination is usually performed by the use of one oftwo general techniques:4.1.1 Encircling C
9、oil 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 tube dimensions, electrical conduc-tivity, saturating magnet
10、ic 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 activates an audible or visual signalingdevice or a mechanical
11、 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 generallysmall and does not encircle the tube, it examines only a
12、 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 products, only theweld is examined by scanning along the weld
13、zone.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 magnetictubular products can cause spurious test results. A usefulsolution to this problem involves the application of a st
14、rong1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Methods.Current edition approved July 10, 2003. Published September 2003. Originallyapproved in 1976. Last previous edition approved
15、 in 1998 as E 571 - 98.2For ASME Boiler and Pressure Vessel Code applications see related PracticeSE-571 in Section II of that Code.3Annual Book of ASTM Standards, Vol 03.03.4Available from The American Society for Nondestructive Testing (ASNT), P.O.Box 28518, 1711 Arlingate Lane, Columbus, OH 43228
16、-0518.5Available from Aerospace Industries Association of America, Inc., 1250 EyeStreet, N.W., Washington, DC 20005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.external magnetic field in the region of the examining coil orprobe.
17、This technique, known as magnetic saturation, causes amagnetic material to exhibit sufficiently small magnetic char-acteristics of permeability, hysteresis, etc., so that the materialunder examination is effectively rendered nonmagnetic. Whenachieved, this condition allows an eddy-current system tom
18、easure and detect electrical resistivity and geometrical varia-tions (including defects) independent of concurrent variationsin magnetic properties.NOTE 2Practice E 309 may be used for strongly magnetic materials.4.2.1 During the examination of slightly magnetic tubingthe signals resulting from the
19、variation of magnetic permeabil-ity can mask the signals resulting from small imperfections. Amagnetic saturation technique can be used to reduce thisinterference to an acceptable level.5. Significance and Use5.1 Eddy-current examination is a nondestructive method oflocating discontinuities in metal
20、lic materials. Signals can beproduced by discontinuities originating on either the externalor internal surfaces of the tube or by discontinuities totallycontained within the wall. Since the density of eddy currentsdecreases nearly exponentially with increasing distance fromthe surface nearest the co
21、il, the response to deep-seated defectsdecreases correspondingly. Phase changes are also associatedwith changes in depth, allowing the use of phase analysistechniques.5.2 The response from natural discontinuities can be signifi-cantly different than that from artificial discontinuities, such asdrill
22、ed holes or notches. For this reason, sufficient work shouldbe done to establish the sensitivity level and setup required todetect 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 i
23、rrelevant 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
24、level shall betreated as a relevant indication until it can be demonstrated thatit is irrelevant.5.4 Generally, eddy-current 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 unif
25、orm over the full length of the tube may notalways be detected with differential encircling coils or probesscanned along the 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 sign
26、al-to-noise ratio intubing that exhibits slight residual magnetism.6. Basis of Application6.1 The following criteria may be 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
27、, dimensions, and number of artificial disconti-nuities to be placed in the reference standard.6.1.3 Extent of examination; 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 in
28、tervals.6.1.6 If specified in the contractual agreement, personnelperforming examinations to this practice shall be qualified 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 c
29、ertified by the certifying agency as applicable. Thepractice or standard used and its applicable revision shall beidentified in the contractual agreement between the usingparties.NOTE 3MIL-STD-410 is canceled and has been replaced with NAS-410, however, it may be used with agreement between contract
30、ing parties.6.1.7 If specified in the contractual agreement, NDT agen-cies shall be qualified and evaluated in accordance withPractice E 543. The applicable edition of Practice E 543 shallbe specified in the contractual agreement.FIG. 1 Encircling-Coil and Probe-Coil Techniques forElectromagnetic Ex
31、amination of Tubular ProductsE 571 98 (2003)e127. Apparatus7.1 Electronic ApparatusThe electronic apparatus shallbe capable of energizing the encircling coils or probes withalternating current of suitable frequencies and shall be capableof sensing changes in impedance of the encircling coils orprobe
32、s. 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 AssemblyThe encircling coil assem-bly shall consist of one or more electrical coils which encirclethe article being
33、 examined. The inside geometry of the coilsshould closely approximate the surface geometry of the speci-men so that when the 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 th
34、e examining coils.7.3 Probe AssemblyThe probe coil assembly normallycontains an exciting coil and a sensor, although in some 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 electromagn
35、etic fluxdensity. Good examination practices require that the spacingbetween the probe coil assembly and the tube being examinedbe 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
36、 with minimum vibration ofcoil, probe, or tube and shall maintain the article beingexamined in proper register or concentricity 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 use
37、d to adjust the sensitivity of theapparatus shall be free of interfering discontinuities and of thesame nominal alloy, temper, 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 provi
38、de good signal resolution, and to be mechanicallystable while in the examining position in the apparatus.Artificial discontinuities 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
39、DischargeMachine) or other suitable means. Notches may be placed onthe outer, inner, or both surfaces of the reference standard.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 throug
40、h the tube wall without causing permanentdistortion of the tube wall.8.1.3 Hole size and notch configuration (type, orientation,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 agreemen
41、t betweenthe supplier and the purchaser.9. Adjustment and Standardization of ApparatusSensitivity9.1 Select the apparatus, examining frequency, coil or probeconfiguration or both, magnetic saturation system if used,phase discrimination, and other circuitry, as well as speed ofexamination. Demonstrat
42、e the system capability for detectingartificial discontinuities of the size and type of interest atproduction speed.9.2 Fabricate the applicable reference standard in accor-dance with the agreement between the purchaser and the tubingsupplier. Discard and replace the tube used as the referencestanda
43、rd when erroneous signals are produced from mechani-cal, metallurgical or other damage to the reference standard.9.3 Rotate the 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
44、 the coil to obtain nearly equal responses from theartificial discontinuities regardless of their circumferentialorientation.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 appropriatei
45、ntervals near the end of this special tube. See Fig. 3. Pass thetube through the examination setup at the production speedwith 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 resp
46、onse froma = longitudinal notch (milled or EDM)b = transverse notch (milled, filed, or EDM)c = drilled hole (radially through one wall)FIG. 2 Various Types of Artificial DiscontinuitiesFIG. 3 Location of Artificial Discontinuities (Notches or DrilledHoles) that Can Be Used to Determine Extent of End
47、 EffectE 571 98 (2003)e13successive discontinuities is uniform with a recording devicesuch as a pen recorder or memory oscilloscope. A signalsuppression method (photo relay, mechanical switches, orproximity devices are commonly used) may be used to permitexamination only when the length of tubing ex
48、hibiting uniformsignals is within the examination coil. The section of tubepassing through the examination coil representing the endeffect is not examined.9.5 As an option to 9.4, the length of tubing representing theend effect may be determined by selecting a tube of lowbackground noise and making
49、a hole or notch at a point 6 to 8in. (152 to 203 mm) from the tube end. Pass the tube throughthe examination coil at the production test speed with theartificial discontinuity end first and then with the artificialdiscontinuity end last. If the artificial discontinuity is notdetected, make another artificial discontinuity farther from theend. If it is detected, cut off 0.5-in. (12.7-mm) increments fromthe end of the tube until the artificial discontinuity is no longerdetected. The length from the tube end to the artificialdiscontinuity that can be detected is that length
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