1、Designation: E 1139 07Standard Practice forContinuous Monitoring of Acoustic Emission from MetalPressure Boundaries1This standard is issued under the fixed designation E 1139; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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.1. Scope1.1 This practice provides guidelines for continuous moni-toring of acoustic emission (AE) from metal pressure bound
3、-aries in industrial systems during operation. Examples arepressure vessels, piping, and other system components whichserve to contain system pressure. Pressure boundaries otherthan metal, such as composites, are specifically not covered bythis document.1.2 The functions of AE monitoring are to dete
4、ct, locate,and characterize AE sources to provide data to evaluate theirsignificance relative to pressure boundary integrity. Thesesources are those activated during system operation, that is, nospecial stimulus is applied to produce AE. Other methods ofnondestructive testing (NDT) may be used, when
5、 the pressureboundary is accessible, to further evaluate or substantiate thesignificance of detected AE sources.1.3 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 saf
6、ety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificprecautionary statements, see Section 6.2. Referenced Documents2.1 ASTM Standards:2E 543 Specification for Agencies Performing Nondestruc-tive TestingE 569 Practice for Acoustic Emission Mon
7、itoring of Struc-tures During Controlled StimulationE 650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE 750 Practice for CharacterizingAcoustic Emission Instru-mentationE 976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor ResponseE 1316 Terminology for Nondestruc
8、tive ExaminationsE 2374 Guide for Acoustic Emission System PerformanceVerification2.2 Aerospace Industries Association:3NAS-410 Certification and Qualification of NondestructiveTesting Personnel2.3 Other Documents:4SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and
9、CertificationANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice, refer toTerminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 continuous monitor
10、ingthe process of monitoring apressure boundary continuously to detect acoustic emissionduring system operation and also during system shut-downtesting such as hydrostatic testing.3.2.2 raw datadata values determined directly from mea-surement of analog inputs. These could include emission countor e
11、mission event count, or both, relative time of signal arrivalat different sensors (delta time), signal rise time, peak signalamplitude, RMS signal level, pressure system pressure andtemperature, and the like.3.2.3 processed datadata resulting from analysis of rawdata. Included would be AE source loc
12、ation coordinates, AEversus time from a given source area, AE signal amplitudeversus time, and the like.4. Summary of Practice4.1 This practice describes the use of a passive monitoringsystem to detect, locate, and characterize AE sources, in orderto evaluate their significance to the integrity of m
13、etal pressureboundaries.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.04 onAcoustic Emission Method.Current edition approved Dec. 1, 2007. Published January 2008. Originallyapproved in 1987. Last previou
14、s edition approved in 2002 as E1193 - 02.2For 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 to the standards Document Summary page onthe ASTM website.3Available from Aero
15、space Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.4Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.1Copyright ASTM Int
16、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 The practice provides guidelines for selection, qualifi-cation, verification, and installation of the AE monitoringsystem. Qualification of personnel is also addressed.4.3 The practice provides guidel
17、ines for using the AEinformation to estimate the significance of a detected AEsource with respect to continued pressure system operation.5. Significance and Use5.1 Acoustic emission examination of a structure requiresapplication of a mechanical or thermal stimulus. In this case,the system operating
18、conditions provide the stimulation. Dur-ing operation of the pressurized system, AE from activediscontinuities such as cracks or from other acoustic sourcessuch as leakage of high-pressure, high-temperature fluids canbe detected by an instrumentation system using sensorsmounted on the structure. The
19、 sensors are acoustically coupledto the surface of the structure by means of a couplant materialor pressure on the interface between the sensing device and thestructure. This facilitates the transmission of acoustic energy tothe sensor. When the sensors are excited by acoustic emissionenergy, they t
20、ransform the mechanical excitations into electri-cal signals. The signals from a detected AE source areelectronically conditioned and processed to produce informa-tion relative to source location and other parameters needed forAE source characterization and evaluation.5.2 AE monitoring on a continuo
21、us basis is a currentlyavailable method for continuous surveillance of a structure toassess its continued integrity. The use of AE monitoring in thiscontext is to identify the existence and location of AE sources.Also, information is provided to facilitate estimating thesignificance of the detected
22、AE source relative to continuedpressure system operation.5.3 Source location accuracy is influenced by factors thataffect elastic wave propagation, by sensor coupling, and bysignal processor settings.5.4 It is possible to measure AE and identify AE sourcelocations of indications that cannot be detec
23、ted by other NDTmethods, due to factors related to methodological, material, orstructural characteristics.5.5 In addition to immediate evaluation of the AE sources,a permanent record of the total data collected (AE plus pressuresystem parameters measured) provides an archival recordwhich can be re-e
24、valuated.6. Hazards6.1 WarningApplication of this practice will inherentlyinvolve work in an operating plant. This may involve potentialexposure to hazardous materials and equipment and, in the caseof nuclear power plants, exposure to nuclear radiation. Awritten safety plan shall be prepared for eac
25、h monitoringinstallation which defines requirements to be observed toprotect personnel safety, safety of the plant system, and to meetadministrative and legal needs. This plan shall be approved byall parties prior to start of work on the plant.7. Basis of Application7.1 The following items are subje
26、ct to contractual agree-ment between the parties using or referencing this practice.7.2 Personnel Qualification7.2.1 If specified in the contractual agreement, personnelperforming examinations to this practice shall be qualified inaccordance with a nationally or internationally recognizedNDT personn
27、el qualification practice or standard such asANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similardocument and certified by the employer or certifying agency,as applicable. The practice or standard used and its applicablerevision shall be identified in the contractual agreement be-tween the using parti
28、es.7.3 Qualification of Nondestructive Agencies7.3.1 If specified in the contractual agreement, NDT agen-cies shall be qualified and evaluated as described in PracticeE 543. The applicable edition of Practice E 543 shall bespecified in the contractual agreement.7.4 Qualification of Nondestructive Te
29、sting AgenciesIfspecified in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E 543. Theapplicable edition of E 543 shall be specified in the contractualagreement.7.5 Timing of ExaminationThe timing of examinationshall be continuous, in accordance with
30、 1.1 unless otherwisespecified.7.6 Extent of ExaminationThe extent of examination shallbe that part of the pressure boundary in the coverage range ofthe mounted acoustic emission sensors, unless otherwise speci-fied.7.7 Reporting Criteria/Acceptance CriteriaReporting cri-teria for the examination re
31、sults shall be in accordance withSection 14 unless otherwise specified. Since acceptance criteria(for example, for reference radiographs) are not specified inthis practice, they shall be specified in the contractual agree-ment.7.8 Reexamination of Repaired/Reworked ItemsReexamination of repaired/rew
32、orked items is not addressed inthis practice and if required shall be specified in the contractualagreement.7.9 Routine operation of the acoustic emission system forcollection and a cursory review of the data may be performedby a competent plant engineer not necessarily specialized inacoustic emissi
33、on. However, acoustic emission system opera-tion and data interpretation should be verified by a qualifiedacoustic emission specialist on approximately six-month inter-vals or sooner if the system appears to be malfunctioning or thedata appear unusual.8. Monitoring System Functional Requirements and
34、Qualification8.1 Functional Requirements:8.1.1 The monitoring system must include the functionalcapabilities shown in Fig. 1 which also shows a suggestedsequence of monitoring system functions.8.1.2 Signal DetectionThe AE sensor together with theacoustic coupling to the structure must have sensitivi
35、ty suffi-cient to detect AE signals while the pressure system isoperating. In most cases, this determination must be performedwhen the pressure system is not operating.AE system responseto normal operational noise, which must be considered here, isdiscussed in 9.1. One method of performing the requi
36、redE1139072evaluation is to use a pencil lead break as a signal source. Withthe sensor in place and connected to the amplifier(s), theresponse at the amplifier output to fracturing a 0.3-mm pencillead against the surface being monitored, at a distance of 150to 300 mm (6 to 12 in.) from the sensor sh
37、ould show aminimum signal-to-noise (electronic plus process noise) ratioof 4 to 1 in a frequency range suitable for the plannedmonitoring environment. A differential sensor should be con-sidered to minimize interference from electronic transients.The sensor must be capable of withstanding the monito
38、ringenvironment (temperature, moisture, nuclear radiation, me-chanical vibration, and the like) for an extended period ofcontinuous exposure. The minimum length of this period willbe dictated by accessibility to the location to change sensors,and by economic considerations.8.1.3 Signal Amplification
39、Appropriate signal amplifica-tion in the range of 0 to 60 dB is usually required to achieve anadequateAE signal level for measurement of signal parametersin digital AE systems. Due to the very small magnitude ofenergy involved in an AE source, it is desirable to locate thesignal amplification as nea
40、r as possible to the output of thesensor. This is beneficial in controlling noise interference andAE signal transmission loss. These preamplifiers must havelow inherent electronic background noise. Resistance of theamplifier circuits to the environment (temperature, moisture,nuclear radiation, mecha
41、nical vibration, and the like) must beconsidered and appropriate steps taken to protect them.NOTE 1When used herein, peak means zero to peak voltage.8.1.4 Monitoring Frequency BandThe frequency re-sponse of the sensor or amplifier combination must be selectedfor the given application. The AE signal
42、being a transient pulseis detectable over a broad range of frequencies. Because theacoustic attenuation in engineering materials is frequencydependent, it is desirable to use a low monitoring frequency(50 to 100 kHz) to maximize the distance from the AE sourceover which the AE event can be detected.
43、 The low end of themonitoring frequency will usually be controlled by the back-ground noise present in the monitoring environment. In someapplications such as operating nuclear reactors, the backgroundnoise may require a low frequency cut-off point of 400 to 500kHz. In cases of severe continuous bac
44、kground noise, inductivetuning of the sensor at the preamplifier input may be effective.The high end of the frequency response band may be limited to1.0 MHz to help reduce amplifier electronic noise.8.1.5 Signal Measurement:8.1.5.1 The signal measurement section will receive thefully-amplified analo
45、g signal. Generally its operation will becontrolled by a voltage threshold circuit which will limitaccepted data to that exceeding the voltage amplitude thresh-old. AE parameters measured may include AE count, AE eventcount, signal amplitude, time from threshold crossing to signalpeak, signal durati
46、on, difference in time of signal arrival atvarious sensors making up a source location array, clock time,data, and the value of any process system parameters (tem-perature, pressure, strain, and the like) available to the AEmonitoring system. If the AE monitoring system is to performdetection of pre
47、ssure system leaks, it must measure the averagesignal level or AE rms voltage for each sensing channel.8.1.5.2 It is desirable that the signal measurements include afunction to assess the characteristics of an acoustic emissionsignal to determine if it matches those originating from crackgrowth. The
48、 function should provide a “flag” for those signalswhich have characteristics similar to those known to originatefrom crack growth as determined by an AE specialist.8.1.5.3 The output from the signal measurement subsystemshould be in digital form to facilitate storage of large quantitiesof data.8.1.
49、6 Raw Data StorageThe AE monitoring system mustinclude a raw digital data storage feature to facilitate retentionof the output from the signal measurement subsystem. Thisserves as a backup in the event that the data analysis processmalfunctions, for example, incorrect operation of the dataanalyzer or loss of power which might destroy data in acomputer memory. The raw data storage device must becompact with a high capacity and be nonvolatile. The dataretention period will be governed by the operating character-istics of the pressure system and by plant procedures. Thestor
