1、Designation: E2907/E2907M 13Standard Practice forExamination of Paper Machine Rolls Using AcousticEmission from Crack Face Rubbing1This standard is issued under the fixed designation E2907/E2907M; the number immediately following the designation indicates the yearof original adoption or, in the case
2、 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.1. Scope1.1 This practice provides guidelines for acoustic emission(AE) examinations of non-pressure, pa
3、per machine rolls.1.2 This practice utilizes a slow rotation of the roll toproduce a full load cycle where load is provided by the weightof the roll suspended from its bearings or other journal supportmechanism(s).1.3 This practice is used for detection of cracks and otherdiscontinuities in rolls th
4、at produce frictional acoustic emissionduring rotation.1.4 The AE measurements are used to detect or locateemission sources, or both. Other nondestructive test (NDT)methods must be used to evaluate the significance of AEsources. Procedures for other NDT techniques are beyond thescope of this practic
5、e. See Note 1.NOTE 1Traditional AE examination, magnetic particle examination,shear wave ultrasonic examination and radiography are commonly used toestablish the exact position and dimensions of flaws that produce AE.1.5 The values stated in either SI units or inch-pound unitsare to be regarded sepa
6、rately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standards.1.6 This standard does not purport to address all of thesafety concer
7、ns, 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 the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.
8、1 ASTM Standards:2E543 Specification for Agencies Performing NondestructiveTestingE650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE976 Guide for Determining the Reproducibility ofAcousticEmission Sensor ResponseE1316 Terminology for Nondestructive ExaminationsE2075 Practice for Verifyi
9、ng the Consistency of AE-SensorResponse Using an Acrylic RodE2374 Guide for Acoustic Emission System PerformanceVerificationE2598 Practice for Acoustic Emission Examination of CastIron Yankee and Steam Heated Paper Dryers2.2 ASNT Standards:3SNT-TC-1A Recommended Practice for NondestructiveTesting Pe
10、rsonnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certifi-cation of Nondestructive Testing Personnel2.3 AIA Document4NAS-410 Certification and Qualification of NondestructiveTesting Personnel3. Terminology3.1 DefinitionsSee Terminology E1316 for general termi-nol
11、ogy applicable to this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 crack face rubbingphysical displacement of existingcrack surfaces as load is changed.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of
12、Subcommittee E07.04 onAcoustic Emission Method.Current edition approved June 1, 2013. Published June 2013. DOI: 10.1520/E2907_E2907M132For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
13、rmation, refer to the standards Document Summary page onthe ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wils
14、on Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 crack face rubbing emissionacoustic emission pro-duced by (frictional mechanisms) within existing cracks t
15、hatare subjected to a change in load.3.2.3 crack-face-rubbing emissionis one form of tribo-acoustic emission.3.2.4 tribo-acoustic emissionstress waves produced byrubbing of surfaces.4. Summary of Practice4.1 The type of paper machine roll that has been mostcommonly examined using this technique is k
16、nown as a “felt”roll.4.2 The felt must be removed or loosened such that a feltroll can be rotated without causing background noise. Electro-magnetically “jogging” the roll may be a possibility, dependingon the availability of electricity in the mill.4.3 The roll is slowly rotated through 360 degrees
17、, thenrotated back to the original 0 degrees orientation. (Test time isapproximately 60 seconds.)4.4 This examination procedure describes a techniquewhereby AE is detected from the rubbing of existing cracksurfaces. Excessive loading to induce crack propagation is notrequired.4.5 The AE sensors are
18、mounted on each end of the roll(bearing journal or shell, or both).4.6 Sensors are connected to an acoustic emission signalprocessor. The signal processor uses single channel data forzone location and measured times of arrival to determine linearlocation of emissions sources.4.7 If measured emission
19、 exceeds a prescribed level (that is,specific areas produce enoughAE activity), then such locationsare considered NDT indications and should receive secondaryNDT examination to determine the severity of the indication.4.8 Secondary examination confirms presence of flaws andmeasures flaw dimensions.4
20、.9 If one dimension of the flaw aspect ratio exceeds aprescribed limit (that is, a conservative limit that is based onconstruction material, wall thickness, fatigue crack growthestimates, and fracture critical flaw depth calculations), thenthe roll must be removed from service.5. Significance and Us
21、e5.1 Paper machine rolls can range in size from 2.4 to9m8to 30 ft long, with a shell thickness of from 12.5 to 75 mm 0.5to 3 in., and 300 to 1200 mm 12 to 48 in. diameter.Depending on purpose, paper machine rolls can weigh as littleas 60 000 kg 13 000 lb to as much as 27 500 kg 60 000 lb.5.2 If indi
22、cations are found during this procedure it can berepeated, with additional sensors to refine source locationaccuracy.5.3 Removal of rolls for traditional NDT examination maybe impractical and may not be sensitive enough to locate smalldefects.5.4 Traditional AE examination, whereby the roll is sub-j
23、ected to load greater than service load to detect crackextension, risks damage to the roll and is best employed as afollow-up NDT examination.5.5 Manual rotation through a full revolution subjects ex-isting cracks to tensile and compressive forces which can openand close existing cracks, and cause f
24、riction at the cracksurfaces.5.6 Excess background noise (overhead cranes, nearbymaintenance activities) may distort AE data or render ituseless. Users must be aware of the following common sourcesof background noise: bearing noise (lack of lubrication,spalling, and so forth), mechanical contact wit
25、h the roll byother objects, electromagnetic interference (EMI) and radiofrequency interference (RFI) from nearby broadcasting facili-ties and from other sources. This practice should not be used ifbackground noise cannot be eliminated or controlled.5.7 Other Non-destructive test methods may be used
26、toevaluate the significance of AE indications. Traditional AE hasbeen used to confirm the existence of the AE indication andfine tune the location. Magnetic particle, ultrasonic and radio-graphic examinations have been used to establish the position,depth and dimensions of the indication. Procedures
27、 for usingother NDT methods are beyond the scope of this practice.6. Basis of Application6.1 The following items are subject to contractual agree-ment between the parties using or referencing this practice.6.2 Personnel QualificationIf specified in the contractualagreement, personnel performing exam
28、inations to this standardshall be qualified in accordance with a nationally or interna-tionally recognized NDT personnel qualification practice orstandard such asANSI/ASNT-CP-189, SNT-TC-1A, NAS-410,or a similar document and certified by the employer orcertifying agency, as applicable. The practice
29、or standard usedand its applicable revision shall be identified in the contractualagreement between the using parties.6.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543. The applicableeditio
30、n of Practice E543 shall be specified in the contractualagreement.6.4 Extent of ExaminationThe extent of examination in-cludes the entire roll unless otherwise specified.6.5 Reporting Criteria/Acceptance CriteriaReporting cri-teria for the examination results shall be in accordance withSection 11 un
31、less otherwise specified. Since acceptance criteria(for example, reference radiographs) are not specified in thispractice, they shall be specified in the contractual agreement.6.6 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed inthis practice and, i
32、f required, shall be specified in the contrac-tual agreement.E2907/E2907M 1327. Apparatus7.1 Essential features of the apparatus required for thispractice are provided in Fig. 1. Full specifications are in AnnexA1.7.2 Couplant must be used to acoustically connect sensorsto the (bare metal) vessel su
33、rface. Adhesives that have accept-able acoustic properties, and adhesives used in combinationwith traditional couplants, are acceptable.7.3 Sensors may be held in place with magnets, elasticstrips, adhesive tape, or other mechanical means.7.4 The AE sensors are used to detect frictionally inducedstr
34、ess waves emanating from the crack surface. Sensors mustbe held in contact with the roll to ensure adequate acousticcoupling.7.5 A preamplifier may be enclosed in the sensor housing orin a separate enclosure. If a separate preamplifier is used, cablelength, between sensor and preamp, must not exceed
35、2m6ft.7.6 Power/signal cable length (that is, cable between pre-amp and signal processor) shall not exceed 150 m 500 ft. SeeA1.5.7.7 Signal processors are computerized instruments withindependent channels that filter, measure, and convert analoginformation into digital form for display and permanent
36、 stor-age.Asignal processor must have sufficient speed and capacityto independently process data from all sensors simultaneously.The signal processor should provide capability to filter data forreplay. A printer should be used to provide hard copies ofexamination results.7.7.1 A video monitor should
37、 display processed examina-tion data in various formats. Display format may be selected bythe equipment operator.7.7.2 A data storage device, such as a hard drive, may beused to provide data for replay or for archives.7.7.3 Hard copy capability should be available from aprinter or equivalent device.
38、8. Safety Precautions8.1 If the roll has been allowed to cool to a very low level,the operator should be aware of the ductile-brittle transitiontemperature of the rolls construction material.9. Calibration and Verification9.1 Annual calibration and verification of signal processor(particularly the s
39、ignal processor time reference), and AEelectronic waveform generator should be performed. Equip-ment should be adjusted so that it conforms to the equipmentmanufacturers specifications. Instruments used for calibra-tions must have current accuracy certification that is traceableto the National Insti
40、tute for Standards and Technology (NIST)or equivalent.9.2 Routine electronic evaluation of the signal processorshould be performed monthly and any time there is concernFIG. 1 Essential Features of the ApparatusE2907/E2907M 133about signal processor performance. An AE electronic wave-form generator s
41、hould be used in making evaluations. Eachsignal processor channel must respond with peak amplitudereading within 62 dBV of the electronic waveform generatoroutput.9.3 Routine evaluation of the sensors should be performedmonthly. An accepted procedure for this purpose is found inPractice E2075 and Gu
42、ide E976.9.4 Pre-examination and post-examination system perfor-mance verification must be conducted immediately before andafter each examination. System performance verification uses amechanical (or electro-mechanical) device to induce stresswaves into the roll at a specified distance from each sen
43、sor.Induced stress waves stimulate a sensor in the same way asemission from a flaw. System performance verification con-firms performance of the entire system (including sensors,cables, and couplant). Procedures for system performanceverification are found in Guide E2374.9.4.1 The preferred techniqu
44、e for conducting a systemperformance verification is a pencil lead break (PLB). Leadshould be broken on the roll surface no less than 10 cm 4 in.from the sensor. The 2H lead, 0.3 mm 0.012 in. diameter, 3mm 0.120 in. long should be used (see 4.3.2 of Guide E976).9.4.2 Auto Sensor Test (AST)An electro
45、mechanical devicesuch as piezoelectric pulser (and sensor which contains thisfunction) can be used in lieu of or in conjunction with pencillead break as a means to ensure system performance.10. Procedure10.1 Obtain a drawing of the paper machine indicating thedesignation and position of each roll to
46、 be examined.10.2 Visually examine accessible exterior surfaces of theroll to be examined. Note observations in examination report.10.3 Verify that the roll is isolated from extraneous noisesources. Felt must be removed or loosened to allow freerotation of the roll without friction. When the roll ca
47、nnot becompletely isolated, indicate, in the examination report, exter-nal sources which could have produced emission.10.4 Clean the area on which the sensor is to be mounteddown to bare metal. This can generally be done with a paintscraper.10.5 Mount an AE sensor at each end of the roll (see Fig. 1
48、for typical sensor placement). Use procedures specified inGuide E650. Sensors must be at the same angular position andshould be located at each end of the roll so that the AE systemcan determine axial locations of sources in as much of the rollas possible. See Note 2.NOTE 2Sensors must be mounted as
49、 close to the roll end as possibleto optimize linear source location accuracy (refer to Fig. 1). Mounting onthe bearing journal or on the shell, close to the end, is acceptable.10.6 Align the sensor connector/cable such that the cablewill not pull on the sensor as the roll is rotated.10.7 Adjust signal processor settings. See Appendix X1 forexample.10.8 Perform a pre-examination, system performance veri-fication at each sensor (see 9.4). Verify that peak amplitude isgreater than a specified value (see Table X1.1). Verify that theAE system displa
