1、Designation: E 570 97 (Reapproved 2004)e1Standard Practice forFlux Leakage Examination of Ferromagnetic Steel TubularProducts1This standard is issued under the fixed designation E 570; 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEEditorial changes were made
3、throughout the standard in January 2004.1. Scope1.1 This practice covers the application and standardizationof equipment using the flux leakage test method for detectionof outer surface, inner surface, and subsurface discontinuitiesin ferromagnetic steel tubular products (Note 1) of uniformcross sec
4、tion such as seamless and welded tubing.NOTE 1The term “tube” or “tubular product” will be used to refer toboth pipe and tubing.1.2 This practice is intended for use on tubular productshaving outside diameters from approximately12 to 24 in. (12.7to 610 mm) with wall thicknesses to12 in (12.7 mm). Th
5、esetechniques have been used for other sizes, however, and maybe so specified upon contractual agreement between thepurchaser and the supplier.1.3 This practice does not establish acceptance criteria; theymust be specified by the using parties.1.4 This standard does not purport to address the safety
6、concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 543 Practice for Evaluating Agencies
7、that Perform Non-destructive TestingE 1316 Terminology for Nondestructive Examinations2.2 Other Documents:SNT-TC-1A Recommended for Personnel Qualification andCertification of Nondestructive Testing Personnel3ANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing
8、 Personnel3NAS-410 NAS Certification and Qualification of Nonde-structive Personnel (Quality Assurance Committee)43. Terminology3.1 Definitions of terms relating to flux leakage examinationare provided in Terminology E 1316.4. Summary of Practice4.1 This method consists of the following steps:4.1.1
9、The tube wall is magnetized at the area under exami-nation to a proper level approaching magnetic saturation.NOTE 2Tubes subjected to magnetic inspections can retain variousstrengths and configuration of residual magnetic fields depending upon themagnetization technique. If the residual field result
10、ing from a giventechnique can interfere with subsequent applications of the tube, then asupplemental demagnetization process may be required.4.1.2 A flux sensor containing magnetic transducers isplaced on or above the outside surface of the tube in themagnetized area.4.1.3 Either the tube or the flu
11、x sensor is moved at aconstant speed in the direction of the magnetic field so that thesensor scans the entire surface of the tube.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Metho
12、d.Current edition approved January 1, 2004. Published February 2004. Originallyapproved in 1976. Last previous edition approved in 1997 as E 570 - 97.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStand
13、ards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from The American Society for Nondestructive Testing (ASNT), P.O.Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.4Available from Aerospace Industries Association of America, Inc., 1250 EyeSt.,
14、NW, Washington, DC 20005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.4 Each magnetic transducer in the flux sensor is con-nected to an electronic console which amplifies, filters, andelectronically processes the signals such
15、that significant dis-continuities are indicated (visually, audibly), and marked withpaint, or automatically removed from the production line, orboth.4.1.5 A suitable means for assuring near magnetic saturationof the product (subject to periodic check or calibration) must beprovided as part of the ex
16、amination to verify the capability ofdetection of outside diameter and inside diameter discontinui-ties.5. Significance and Use5.1 This practice outlines a procedure for examining ferro-magnetic tubular products using the flux leakage method. Ifproperly applied, this method is capable of detecting t
17、hepresence and location of significant longitudinally or trans-versely oriented discontinuities such as pits, scabs, slivers,gouges, roll-ins, laps, seams, cracks, holes, and improper weldsin ferromagnetic tubes under inspection. In addition, theseverity of a discontinuity may be estimated and a rej
18、ectionlevel set with respect to the magnitude of the electromagneticindication produced by the discontinuity.5.2 The response from natural discontinuities can be signifi-cantly different from the response for artificial discontinuitiessuch as drilled holes or notches of equivalent depth. For thisrea
19、son, sufficient work should be done to determine theconditions necessary to detect and mark natural discontinuitieswhose characteristics will adversely affect the serviceability ofthe tube, in order to establish acceptance criteria between thesupplier and purchaser.6. Basis of Application6.1 The fol
20、lowing criteria may be specified in the purchasespecification, contractual agreement, or elsewhere, and mayrequire agreement between the purchaser and supplier:6.1.1 Acceptance criteria.6.1.2 Type, dimensions, location, and number of artificialdiscontinuities to be placed on the reference standard.6
21、.1.3 Size and type of tubing to be examined.6.1.4 Extent of examination (that is, full length, weld zoneonly if welded, etc.).6.1.5 Disposition of material with discontinuity indications.6.1.6 Methods of verifying dimensions of artificial discon-tinuities and allowable tolerances.6.1.7 Time of inspe
22、ction, that is, the point(s) in the manu-facturing process at which the material will be inspected.6.1.8 Nondestructive testing (NDT) personnel shall bequalified in accordance with a nationally recognized NDTpersonnel qualification practice or standard such as ANSI/ASNT CP-189, SNT-TC-1A, MIL-STD-41
23、0, NAS-410, or asimilar document. The practice or standard used and itsapplicable revision shall be specified in the purchase specifi-cation or contractual agreement between the using parties.NOTE 3MIL-STD-410 is canceled and has been replaced with NAS-410, however, it may be used with agreement bet
24、ween contracting parties.6.1.9 If specified in the purchase specification or contractualagreement, NDT agencies shall be evaluated and qualified asdescribed in Practice E 543. The applicable edition of PracticeE 543 shall be identified in the purchase specification orcontractual agreement between th
25、e using parties.7. Interferences7.1 There are some manufacturing processes that producetubing with surface conditions that could interfere with orobscure signals related to inner surface discontinuities. In theexamination of heavy-walled tubing having these conditions,the ability to examine reliably
26、 for inner surface discontinuitiesmay be affected.7.2 When examining tubes with large rapid surface varia-tions, false signals may be caused by the sensors bouncingalong the surface of the tubes.7.3 For active pole magnetizing systems, a small air gapbetween the magnetizing system and material under
27、 examina-tion could cause a heavy accumulation of scale buildup on thepole pieces.DETECTION OF LONGITUDINALDISCONTINUITIES8. Apparatus8.1 Rotary MechanismThe rotary mechanism shall becapable of rotating a magnetizing system or flux leakagesensors, or both, in unison around tubing that is beingtransl
28、ated axially through the mechanism, thereby producing ahelical scan over the surface. Good examination practicesrequire that the pole pieces of the magnetizing system rotateuniformly about the tube and that the flux sensor ride on thetube or be spaced uniformly above the surface of the tubeduring ro
29、tation.8.2 Spin Feed MechanismThe spin feed mechanism shallbe capable of positioning a magnetizing system or flux leakagesensors, or both, on or near the surface of a translating rotatingtube such that there is a uniform spacing between the polepieces of the magnetizing system and the tube. The flux
30、leakage sensors shall ride on the surface of the tube or be helduniformly from the surface of the tube during examination.8.3 Magnetizing System:8.3.1 An active field magnetizing system consists of asuitable means of applying a strong adjustable transversemagnetic field to the region of the tube und
31、er the flux sensorsand shall be capable of bringing that region of the tube to nearsaturation. Typical systems employ either permanent magnetsor controllable electromagnets. If permanent magnets are used,a means shall be provided to adjust the spacing of the polepieces in order to reach the proper m
32、agnetization level. Referto Section 13 for application of longitudinal magnetic fields.8.3.2 A residual field magnetizing system consists of ameans of applying a circular residual magnetic field to an entiretube before the tube is inspected. Typical systems employ acentrally positioned conducting ro
33、d through which a highdirect current is passed; alternatively, the current may beconducted through the tube itself. The current produces acircular active magnetic field which is concentric with thecurrent distribution. When the current ceases, there remains aresidual magnetic field which is circular
34、, concentric with thetube, and wholly contained within the tube wall.E 570 97 (2004)e128.4 Flux Leakage Sensors:8.4.1 The flux sensor shall consist of magnetic field trans-ducers that respond to variations in magnetic flux density.These sensors generally consist of one of the following types:electro
35、magnetic coils, Hall probes, magneto diodes, magnis-tors, or magnetoresistors. These sensors are normally used todetect the flux leakage directly from the discontinuity in thetube; however, they may also be used to detect flux leakagepatterns that have been transferred from the tube to a strip ofmag
36、netic tape. The flux sensors should be of sufficient numberand length so as to provide 100 % coverage while scanning thetube surface to be examined at the desired examination speed.Their location (with respect to the magnetic pole pieces and thetubular product) should result in maximum response to t
37、heleakage field caused by a discontinuity in the tubular product.8.4.2 The depth and orientation of a discontinuity below theoutside surface will affect the magnitude of the signal receivedfrom it. Sensitivity decreases significantly as the distancebetween the flux leakage sensor and the tube under
38、examina-tion is increased. Therefore, the sensors should remain cleanand have uniform contact with the tube surface, or if air ridingthe sensors should be held at a uniform distance above thesurface of the tube.8.5 Electronic InstrumentationThe electronic apparatusshall be capable of amplifying sign
39、als from the flux sensors andprocessing them for the operation of alarms. Multiple probesmay be used to increase the speed of examination. The signalsmay be processed in two separate channels to result in adifferentiation between inner and outer surface discontinuities.Each of the two sets of electr
40、onic channels should contain itsown sensitivity and threshold triggering controls for indepen-dent setting of percentage of wall rejection levels.8.6 Driving MechanismA mechanical drive mechanismshall be used which is capable of rigidly holding and passingthe tube through the inspection apparatus at
41、 constant speed andconcentric with the inspection apparatus. As required, thedriving mechanism shall be capable of rotating and advancing,or just advancing the tube with a constant speed.9. Principles of Examination9.1 Conduct the examination of tubular products for longi-tudinal discontinuities emp
42、loying a transverse magnetic fieldand flux leakage detectors using one or more of the followingtechniques:9.1.1 Obtain a transverse magnetic field by either (1)positioning north and south poles of a magnet on opposite sidesof a tube on a diameter or chord as shown in Fig. 1(a) and 1(b);or (2) passin
43、g a high direct current through a conducting rodcentrally positioned in the tube under examination.9.1.2 Position a flux sensor (or sensors) containing magneticfield transducers on or near the tube surface and move at auniform speed over the area being magnetized.9.1.3 At a discontinuity in the tube
44、 wall, the flux lines aredistorted, producing a leakage field. The maximum flux leak-age for a discontinuity normally occurs when magnetization isperpendicular to the discontinuity.9.1.4 For active pole magnetization, rotation of the magne-tizing system about the tube results in transverse magnetiza
45、tionof the tube wall that is periodically perpendicular to all radii ofthe tube (Fig. 2(a). Rotation of the tube with the magnetizingpoles held stationary will also produce the same effect (Fig.2(b).9.1.5 Relative motion between the flux sensor and the fluxleakage field caused by the discontinuity i
46、s generally utilized togenerate a voltage in the flux sensor. The amplitude of thevoltage generated by the sensor is generally indicative of theseverity of the discontinuity when all other factors are constant.The flux leakage field measured at the outside surface of thetube resulting from an inside
47、 surface discontinuity is muchbroader than the leakage field from a discontinuity of equalseverity located on the outer surface of the tube, resulting in alower signal frequency for the inner surface discontinuity (Fig.3(a) and 3(b). Several types of equipment utilize this infor-mation to determine
48、whether the discontinuity is located on theinner or outer surface of the tube.9.1.6 Near saturation is required to provide repeatable andreliable indications for the presence of outer surface, innersurface, or subsurface discontinuities. A suitable measuringmeans or reference samples or both are req
49、uired to properlyadjust the equipment for operation at the required sensitivityand magnetization level.9.2 The examination of tubular products for transversediscontinuities utilizing a longitudinal magnetic field is dis-cussed in Section 14.10. Reference Standard10.1 The tubes selected for reference standards should befirst examined to ascertain that they are free of interferingnatural discontinuities prior to the introduction of artificialdefects. The standard tube shall be of the same alloy, temper,and nominal dimensions as the tubes to be examined on aproduction basis.
