1、Designation:E121107 Designation: E1211/E1211M 12Standard Practice forLeak Detection and Location Using Surface-MountedAcoustic Emission Sensors1This standard is issued under the fixed designation E1211/E1211M; the number immediately following the designation indicates the yearof original adoption or
2、, in the case 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. Scope*1.1 This practice describes a passive method for detecting and locating the steady
3、 state source of gas and liquid leaking out ofa pressurized system. The method employs surface-mounted acoustic emission sensors (for non-contact sensors see Test MethodE1002), or sensors attached to the system via acoustic waveguides (for additional information, see Terminology E1316), and maybe us
4、ed for continuous in-service monitoring and hydrotest monitoring of piping and pressure vessel systems. High sensitivitiesmay be achieved, although the values obtainable depend on sensor spacing, background noise level, system pressure, and type ofleak.1.2The values stated in inch-pound units are to
5、 be regarded as the standard. SI units are provided for information only.1.2 UnitsThe values stated in either SI units or inch-pound units are to be regarded as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Co
6、mbining values from thetwo systems may result in non-conformance with the standards.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and
7、 determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive TestingE650 Guide for Mounting Piezoelectric Acoustic Emission SensorsE750 Practice for Characterizing Acoustic Emission Instrumenta
8、tionE976 Guide for Determining the Reproducibility of Acoustic Emission Sensor ResponseE1002 Practice for Leaks Using UltrasonicsE1316 Terminology for Nondestructive ExaminationsE2374 Guide for Acoustic Emission System Performance Verification2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for No
9、ndestructive Testing Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certification of Nondestructive Testing Personnel2.3 AIA Document:NAS 410 Certification and Qualification of Nondestructive Testing Personnel43. Summary of Practice3.1 This practice requires
10、 the use of contact sensors, amplifier electronics, and equipment to measure their output signal levels.The sensors may be mounted before or during the examination period and are normally left in place once mounted rather than beingmoved from point to point.3.2 Detection of a steady-state leak is ba
11、sed on detection of the continuous, broadband signal generated by the leak flow. Signal1This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 onAcoustic EmissionMethod.Current edition approved July 1, 2007. Pub
12、lished July 2007. Originally approved in 1987. Last previous edition approved in 2002 as E1211-02. DOI: 10.1520/E1211-07.Current edition approved June 15, 2012. Published August 2012. Originally approved in 1987. Last previous edition approved in 2007 as E1211 - 07. DOI:10.1520/E1211_E1211M-12.2For
13、referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Available from American Society for Nondestructive Testing (ASN
14、T), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.1This document is not an ASTM standard and is intended onl
15、y to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versi
16、onof the standard as published by ASTM is to be considered the official document.*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.detection is accomplished through measu
17、rement of some input signal level, such as its root-mean-square (RMS) amplitude oraverage signal level.3.3 The simplest leak test procedure involves only detection of leaks, treating each sensor channel individually.Amore complexexamination requires processing the signal levels from two or more sens
18、ors together to allow computation of the approximate leaklocation, based on the principle that the leak signal amplitude decreases as a function of distance from the source.4. Significance and Use4.1 Leakage of gas or liquid from a pressurized system, whether through a crack, orifice, seal break, or
19、 other opening, mayinvolve turbulent or cavitational flow, which generates acoustic energy in both the external atmosphere and the system pressureboundary. Acoustic energy transmitted through the pressure boundary can be detected at a distance by using a suitable acousticemission sensor.4.2 With pro
20、per selection of frequency passband, sensitivity to leak signals can be maximized by eliminating background noise.At low frequencies, generally below 100 kHz, it is possible for a leak to excite mechanical resonances within the structure thatmay enhance the acoustic signals used to detect leakage.4.
21、3 This practice is not intended to provide a quantitative measure of leak rates.5. Basis of Application5.1 The following items are subject to contractual agreement between parties using or referencing this practice.5.2 Personnel Qualification5.2.1 If specified in the contractual agreement, personnel
22、 performing examinations to this practice shall be qualified inaccordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT CP-189, SNT-TC-1A, NAS 410, or a similar document and certified by the employer or certifying agency, as applic
23、able.The practice or standard used and its applicable revision shall be identified in the contractual agreement between the using parties.5.3 Qualification of Nondestructive AgenciesIf specified in the contractual agreement, NDT agencies shall be qualified andevaluated as described in Practice E543.
24、 The applicable edition of Practice E543 shall be specified in the contractual agreement.5.4 Timing of ExaminationThe timing of examination shall be in accordance with 7.1.7 unless otherwise specified.5.5 Extent of ExaminationThe extent of examination shall be in accordance with 7.1.4 and 10.1.1.1 u
25、nless otherwisespecified.5.6 Reporting Criteria/Acceptance CriteriaReporting criteria for the examination results shall be in accordance with 10.2.2and Section 11 unless otherwise specified. Since acceptance criteria are not specified in this practice, they shall be specified in thecontractual agree
26、ment.5.7 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed in this practiceand if required shall be specified in the contractual agreement.6. Interferences6.1 External or internal noise sources can affect the sensitivity of an acoustic emission leak de
27、tection system. Examples ofinterfering noise sources are:6.1.1 Turbulent flow or cavitation of the internal fluid,6.1.2 Noise from grinding or machining on the system,6.1.3 Airborne acoustic noise, in the frequency range of the measuring system,6.1.4 Metal impacts against, or loose parts frequently
28、striking the pressure boundary, and6.1.5 Electrical noise pick-up by the sensor channels.6.2 Stability or constancy of background noise can also affect the maximum allowable sensitivity, since fluctuation inbackground noise determines the smallest change in level that can be detected.6.3 The acousti
29、c emission sensors must have stable characteristics over time and as a function of both the monitoring structureand the instrumentation system examination parameters, such as temperature.6.4 Improper sensor mounting, electronic signal conditioner noise, or improper amplifier gain levels can decrease
30、 sensitivity.7. Basic Information7.1 The following items must be considered in preparation and planning for monitoring:7.1.1 Known existing leaks and their distance from the areas to be monitored should be noted so that their influence on thecapabilities of the method can be evaluated.7.1.2 Type of
31、vessel, pipeline, or installation to be examined, together with assembly, or layout drawings, or both, givingsufficient detail to establish dimensions, changes of shape likely to affect flow characteristics, positions of welds, and the locationof components such as valves or flanges, and attachments
32、 to the vessel or pipe such as pipe hangers where leaks are most likelyto arise. Regions with restricted accessibility due to walls, the existence or location of cladding, insulation, or below surfacecomponents must be specified.7.1.3 When location of the peak is of primary interest, quantitative in
33、formation regarding the leakage rates of interest andwhenever possible the type of leak is necessary.E1211/E1211M 1227.1.4 Extent of monitoring, for example, entire volume of pressure boundary, weld areas only, etc.7.1.5 Material specifications and type of surface covering (for example paint or othe
34、r coating) to allow the acoustic propagationcharacteristics of the structure to be evaluated.7.1.6 Proposed program of pressure application or process-pressure schedule, specifying the pressurization schedule togetherwith a layout or sketch of the pressure-application system and specifying the type
35、of fluid used during the examination, forexample, gas, water, or oil.7.1.7 Time of monitoring, that is, the point(s) in the manufacturing process, or service life at which the system will bemonitored, or both.7.1.8 Frequency range to be used in the monitoring equipment.7.1.9 Environmental conditions
36、 during examination that may affect instrumentation and interpretation of results; for example,temperature, moisture, radioactivity, vibration, pressure, and electromagnetic interference.7.1.10 Limitations or restrictions on the sensor mounting procedure, if applicable, including restrictions on cou
37、plant materials.7.1.11 The location of sensors or waveguides and preparation for their installation to provide adequate coverage of the areasspecified in 7.1.3. Where particular sections are to be examined with particular sensors, the coverage of the vessel or system bysensor subgroups shall be spec
38、ified. The sensor locations must be given as soon as possible, to allow positioning difficulties to beidentified.7.1.12 The communications procedure between the acoustic emission staff and the control staff, the time intervals at whichpressure readings are to be taken, and the procedure for giving w
39、arning of unexpected variations in the pressure system.7.1.13 Requirements for permanent records, if applicable.7.1.14 Content and format of examination report, if required.7.1.15 Acoustic Emission Examiner qualifications and certification, if required.8. Apparatus8.1 SensorsThe acoustic emission se
40、nsors are generally piezoelectric devices and should be mounted in accordance withPractice E650 to ensure proper signal coupling. The frequency range of the sensors may be as high as 1 MHz, and either widebandor resonant sensors may be employed. The higher frequencies can be used to achieve greater
41、discrimination against airborne ormechanical background noise.8.2 AmplifiersAmplifiers/preamplifiers should have sufficient gain to allow the signal processing equipment to detect the levelof acoustic background noise on the pressurized system. The sensor/amplifier bandwidth should be selected to mi
42、nimizebackground noise.8.3 Signal ProcessorThe signal processor measures the RMS level, the acoustic emission signal power, the average signallevel, or any other similar parameters of the continuous signal.Aleak location processor to compute the source location from signallevels and attenuation data
43、 may be included. Alarm setpoints may also be included as a processor function.8.4 Leak Signal Simulator:8.4.1 A device for simulating leaks should be included to evaluate the effectiveness of the monitoring system. The followingcould be considered: a sensor on the pressure boundary driven from a ra
44、ndom-noise generator, a small water jet, or a gas jet.8.4.2 When leak location processing is to be performed, leak simulation should be carried out initially over a sufficiently largenumber of diverse points to verify proper operation of the location algorithm.9. System Performance Verification9.1 S
45、ystem performance verification consists of two stages. The first stage concerns periodic calibration and verification of theequipment under laboratory conditions. This procedure is beyond the scope of this practice (see Practice E750) but the results mustbe made available to the system owners if req
46、uested. The second stage concerns in-situ verification to check the sensitivities ofall channels and the satisfactory operation of the detection equipment. For every verification operation, a written procedure shallbe prepared.9.2 In-situ sensitivity check of all sensors should be performed by placi
47、ng a leak signal simulator (see Guide E976) at a specifieddistance from each sensor and recording the resulting output level from the amplifier, as referred to the amplifier input terminal.Amplifier gains may also be adjusted as appropriate to correct for sensitivity variations.9.3 Periodic system v
48、erification checks shall be made prior to the examination and during long examinations (days) or if anyenvironmental changes occur. The relative verification check is accomplished by driving various sensors or activating various leaksimulation devices such as water or gas jets (see Guide E2374) and
49、measuring the outputs of the receiving sensors. The ratio ofthe outputs of two receiving sensors for a given injection point should remain constant over time. Any change in the ratio indicatesa deviation in performance. In this way, all sensors on a system may be compared to one or several reference signals and properadjustments made (see Guide E976).9.4 When leak location calculations are to be performed, the acoustic attenuation between sensors should be characterized overthe frequency band of interest, especially if the presence of discontinuities, such as pipe joints,
