ASTM E1211/E1211M-17

Standard Practice for Leak Detection and Location Using Surface-Mounted Acoustic Emission Sensors

SIGNIFICANCE AND USE
4.1 Leakage of gas or liquid from a pressurized system, whether through a crack, orifice, seal break, or other opening, may involve turbulent or cavitational flow, which generates acoustic energy in both the external atmosphere and the system pressure boundary. Acoustic energy transmitted through the pressure boundary can be detected at a distance by using a suitable acoustic emission sensor.  
4.2 With proper 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 that may enhance the acoustic signals used to detect leakage.  
4.3 This practice is not intended to provide a quantitative measure of leak rates.
SCOPE
1.1 This practice describes a passive method for detecting and locating the steady state source of gas and liquid leaking out of a pressurized system. The method employs surface-mounted acoustic emission sensors (for non-contact sensors see Test Method E1002), or sensors attached to the system via acoustic waveguides (for additional information, see Terminology E1316), and may be used for continuous in-service monitoring and hydrotest monitoring of piping and pressure vessel systems. High sensitivities may be achieved, although the values obtainable depend on sensor spacing, background noise level, system pressure, and type of leak.  
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two 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 responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2017
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.04 - Acoustic Emission Method

Relations

• Replaces: ASTM E1211/E1211M-12 - Standard Practice for Leak Detection and Location Using Surface-Mounted Acoustic Emission Sensors
• Effective Date: 01-Jun-2017
• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM E750-15(2020) - Standard Practice for Characterizing Acoustic Emission Instrumentation
• Effective Date: 01-Jun-2020
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM E1316-17a - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2017
• Refers: ASTM E1316-17 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2017
• Refers: ASTM E1316-16a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Aug-2016
• Refers: ASTM E1316-16 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2016
• Refers: ASTM E1316-15a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2015
• Refers: ASTM E750-15 - Standard Practice for Characterizing Acoustic Emission Instrumentation
• Effective Date: 01-Dec-2015
• Refers: ASTM E2374-15 - Standard Guide for Acoustic Emission System Performance Verification
• Effective Date: 01-Dec-2015
• Refers: ASTM E1316-15 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Sep-2015
• Refers: ASTM E1316-14 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014

Overview

ASTM E1211/E1211M-17: Standard Practice for Leak Detection and Location Using Surface-Mounted Acoustic Emission Sensors establishes a passive, nondestructive testing method for detecting and locating steady-state gas and liquid leaks from pressurized systems. It utilizes surface-mounted acoustic emission (AE) sensors, providing a systematic approach for in-service and hydrostatic monitoring of piping, pressure vessels, and related components. This standard focuses on maximizing leak detection sensitivity while addressing the influence of sensor spacing, background noise, system pressure, and leak type. Combined use of SI and inch-pound units enhances international applicability.

Key Topics

• Leak Detection Principle: Uses the acoustic energy generated by turbulent or cavitational flow at leak sites. AE sensors detect this energy through the pressure boundary, providing both detection and location options.
• Sensor Strategy: Emphasizes the use of contact-based, surface-mounted sensors or sensors with acoustic waveguides for continuous monitoring. Wideband or resonant piezoelectric sensors are recommended for optimal signal quality.
• Signal Processing: Detection is based on continuous, broadband signal measurement (RMS amplitude, average signal level). Multi-sensor analysis allows for approximate leak location.
• Noise Management: Proper frequency selection, typically below 100 kHz for certain applications, helps maximize leak sensitivity by filtering background noise and potential mechanical resonances.
• Performance Verification: Periodic calibration and in-situ sensitivity checks are outlined for maintaining reliable system performance.
• Personnel Qualification: Highlights the importance of qualified and certified nondestructive testing (NDT) personnel, referencing key certification standards.

Applications

ASTM E1211/E1211M-17 is widely used in industries where the integrity of pressurized systems is critical:

• Oil, Gas, and Petrochemical: Detects leaks in pipelines, valves, and vessel systems during commissioning, operation, and maintenance.
• Power Generation: Monitors critical pressure components, such as safety or relief valves and boiler tubing, for potential failures.
• Marine and Offshore: Facilitates leak detection in submerged piping, ball valves, and transfer lines under dynamic environmental conditions.
• Manufacturing and Chemical Processing: Used during hydrotesting and regular operational monitoring of tanks, vessels, and process lines to ensure containment.

Practical benefits include improved safety, environmental protection, reduction in unplanned downtime, and cost-effective asset management. The method is valued for its ability to detect leaks in real time without system shutdown or invasive procedures.

Related Standards

ASTM E1211/E1211M-17 is harmonized with other key standards for acoustic emission leak detection and nondestructive examination:

• ASTM E1002: Practice for Leaks Using Ultrasonics (non-contact sensor option)
• ASTM E650: Guide for Mounting Piezoelectric Acoustic Emission Sensors
• ASTM E750: Practice for Characterizing Acoustic Emission Instrumentation
• ASTM E976: Guide for Determining Reproducibility of AE Sensor Response
• ASTM E2374: Guide for AE System Performance Verification
• ASTM E543: Agencies Performing Nondestructive Testing
• ASTM E1316: Terminology for Nondestructive Examinations
• SNT-TC-1A, ANSI/ASNT CP-189, NAS 410: NDT personnel qualification and certification
• ISO 9712: Non-Destructive Testing - Qualification and Certification of NDT Personnel

By adhering to these standards, organizations ensure robust leak detection performance, regulatory compliance, and alignment with internationally recognized best practices in nondestructive testing.

Keywords: acoustic emission, leak detection, nondestructive testing, pressure vessels, piping systems, surface-mounted sensors, hydrotest, continuous monitoring, ASTM E1211/E1211M

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1211/E1211M − 17
Standard Practice for
Leak Detection and Location Using Surface-Mounted
Acoustic Emission Sensors
ThisstandardisissuedunderthefixeddesignationE1211/E1211M;thenumberimmediatelyfollowingthedesignationindicatestheyear
of original adoption or, 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* E543 Specification for Agencies Performing Nondestructive
Testing
1.1 This practice describes a passive method for detecting
E650 Guide for Mounting Piezoelectric Acoustic Emission
and locating the steady state source of gas and liquid leaking
Sensors
out of a pressurized system. The method employs surface-
E750 Practice for Characterizing Acoustic Emission Instru-
mounted acoustic emission sensors (for non-contact sensors
mentation
see Test Method E1002), or sensors attached to the system via
E976 GuideforDeterminingtheReproducibilityofAcoustic
acoustic waveguides (for additional information, seeTerminol-
Emission Sensor Response
ogy E1316), and may be used for continuous in-service
E1002 Practice for Leaks Using Ultrasonics
monitoring and hydrotest monitoring of piping and pressure
E1316 Terminology for Nondestructive Examinations
vessel systems. High sensitivities may be achieved, although
E2374 Guide for Acoustic Emission System Performance
the values obtainable depend on sensor spacing, background
Verification
noise level, system pressure, and type of leak.
2.2 ASNT Documents:
1.2 Units—The values stated in either SI units or inch-
SNT-TC-1A Recommended Practice for Nondestructive
pound units are to be regarded as standard.The values stated in
Testing Personnel Qualification and Certification
each system may not be exact equivalents; therefore, each
ANSI/ASNT CP-189 Standard for Qualification and Certifi-
system shall be used independently of the other. Combining
cation of Nondestructive Testing Personnel
values from the two systems may result in non-conformance
2.3 AIA Document:
with the standards.
NAS 410 Certification and Qualification of Nondestructive
1.3 This standard does not purport to address all of the
Testing Personnel
safety concerns, if any, associated with its use. It is the
2.4 ISO Standard:
responsibility of the user of this standard to establish appro-
ISO 9712 Non-Destructive Testing: Qualification and Certi-
priate safety and health practices and determine the applica-
fication of NDT Personnel
bility of regulatory limitations prior to use.
1.4 This international standard was developed in accor- 3. Summary of Practice
dance with internationally recognized principles on standard-
3.1 This practice requires the use of contact sensors, ampli-
ization established in the Decision on Principles for the
fier electronics, and equipment to measure their output signal
Development of International Standards, Guides and Recom-
levels. The sensors may be mounted before or during the
mendations issued by the World Trade Organization Technical
examination period and are normally left in place once
Barriers to Trade (TBT) Committee.
mounted rather than being moved from point to point.
3.2 Detection of a steady-state leak is based on detection of
2. Referenced Documents
the continuous, broadband signal generated by the leak flow.
2.1 ASTM Standards:
Signal detection is accomplished through measurement of
some input signal level, such as its root-mean-square (RMS)
1 amplitude or average signal level.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.04 on
Acoustic Emission Method.
Current edition approved June 1, 2017. Published June 2017. Originally AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
approved in 1987. Last previous edition approved in 2012 as E1211 - 12. DOI: 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
10.1520/E1211_E1211M-17. Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
For referenced ASTM standards, visit the ASTM website, www.astm.org, or WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from International Organization for Standardization (ISO), ISO
Standards volume information, refer to the standard’s Document Summary page on Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
the ASTM website. Geneva, Switzerland, http://www.iso.org.
*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
E1211/E1211M − 17
3.3 The simplest leak test procedure involves only detection 6. Interferences
of leaks, treating each sensor channel individually. A more
6.1 External or internal noise sources can affect the sensi-
complex examination requires processing the signal levels
tivity of an acoustic emission leak detection system. Examples
from two or more sensors together to allow computation of the
of interfering noise sources are:
approximate leak location, based on the principle that the leak
6.1.1 Turbulent flow or cavitation of the internal fluid,
signal amplitude decreases as a function of distance from the
6.1.2 Noise from grinding or machining on the system,
source.
6.1.3 Airborne acoustic noise, in the frequency range of the
4. Significance and Use measuring system,
6.1.4 Metal impacts against, or loose parts frequently strik-
4.1 Leakage of gas or liquid from a pressurized system,
ing the pressure boundary, and
whether through a crack, orifice, seal break, or other opening,
6.1.5 Electrical noise pick-up by the sensor channels.
may involve turbulent or cavitational flow, which generates
acoustic energy in both the external atmosphere and the system
6.2 Stability or constancy of background noise can also
pressure boundary. Acoustic energy transmitted through the
affect the maximum allowable sensitivity, since fluctuation in
pressure boundary can be detected at a distance by using a
background noise determines the smallest change in level that
suitable acoustic emission sensor.
can be detected.
4.2 With proper selection of frequency passband, sensitivity
6.3 The acoustic emission sensors must have stable charac-
to leak signals can be maximized by eliminating background
teristics over time and as a function of both the monitoring
noise. At low frequencies, generally below 100 kHz, it is
structure and the instrumentation system examination
possible for a leak to excite mechanical resonances within the
parameters, such as temperature.
structure that may enhance the acoustic signals used to detect
6.4 Improper sensor mounting, electronic signal conditioner
leakage.
noise, or improper amplifier gain levels can decrease sensitiv-
4.3 This practice is not intended to provide a quantitative
ity.
measure of leak rates.
5. Basis of Application
7. Basic Information
5.1 The following items are subject to contractual agree-
7.1 The following items must be considered in preparation
ment between parties using or referencing this practice.
and planning for monitoring:
7.1.1 Knownexistingleaksandtheirdistancefromtheareas
5.2 Personnel Qualification
5.2.1 If specified in the contractual agreement, personnel to be monitored should be noted so that their influence on the
capabilities of the method can be evaluated.
performing examinations to this practice shall be qualified in
accordance with a nationally or internationally recognized
7.1.2 Type of vessel, pipeline, or installation to be
NDT personnel qualification practice or standard such as examined, together with assembly, or layout drawings, or both,
ANSI/ASNT CP-189, SNT-TC-1A, NAS 410, ISO 9712, or a
giving sufficient detail to establish dimensions, changes of
similar document and certified by the employer or certifying shape likely to affect flow characteristics, positions of welds,
agency, as applicable. The practice or standard used and its and the location of components such as valves or flanges, and
applicable revision shall be identified in the contractual agree- attachments to the vessel or pipe such as pipe hangers where
ment between the using parties. leaks are most likely to arise. Regions with restricted accessi-
bility due to walls, the existence or location of cladding,
5.3 Qualification of Nondestructive Agencies—If specified
insulation, or below surface components must be specified.
in the contractual agreement, NDT agencies shall be qualified
7.1.3 When location of the peak is of primary interest,
and evaluated as described in Practice E543. The applicable
quantitative information regarding the leakage rates of interest
edition of Practice E543 shall be specified in the contractual
and whenever possible the type of leak is necessary.
agreement.
7.1.4 Extent of monitoring, for example, entire volume of
5.4 Timing of Examination—The timing of examination
pressure boundary, weld areas only, etc.
shall be in accordance with 7.1.7 unless otherwise specified.
7.1.5 Material specifications and type of surface covering
5.5 Extent of Examination—The extent of examination shall
(for example paint or other coating) to allow the acoustic
be in accordance with 7.1.4 and 10.1.1.1 unless otherwise
propagation characteristics of the structure to be evaluated.
specified.
7.1.6 Proposed program of pressure application or process-
5.6 Reporting Criteria/Acceptance Criteria—Reporting cri-
pressure schedule, specifying the pressurization schedule to-
teria for the examination results shall be in accordance with
gether with a layout or sketch of the pressure-application
10.2.2 and Section 11 unless otherwise specified. Since accep-
system and specifying the type of fluid used during the
tance criteria are not specified in this practice, they shall be
examination, for example, gas, water, or oil.
specified in the contractual agreement.
7.1.7 Time of monitoring, that is, the point(s) in the manu-
facturing process, or service life at which the system will be
5.7 Reexamination of Repaired/Reworked Items—
monitored, or both.
Reexamination of repaired/reworked items is not addressed in
this practice and if required shall be specified in the contractual 7.1.8 Frequency range to be used in the monitoring equip-
agreement. ment.
E1211/E1211M − 17
7.1.9 Environmental conditions during examination that the equipment under laboratory conditions. This procedure is
may affect instrumentation and interpretation of results; for beyond the scope of this practice (see Practice E750) but the
example, temperature, moisture, radioactivity, vibration, results must be made available to the system owners if
pressure, and electromagnetic interference. requested. The second stage concerns in-situ verification to
7.1.10 Limitations or restrictions on the sensor mounting check the sensitivities of all channels and the satisfactory
procedure, if applicable, including restrictions on couplant operation of the detection equipment. For every verification
materials. operation, a written procedure shall be prepared.
7.1.11 The location of sensors or waveguides and prepara-
9.2 In-situ sensitivity check of all sensors should be per-
tion for their installation to provide adequate coverage of the
formed by placing a leak signal simulator (see Guide E976)at
areas specified in 7.1.3. Where particular sections are to be
a specified distance from each sensor and recording the
examined with particular sensors, the coverage of the vessel or
resulting output level from the amplifier, as referred to the
system by sensor subgroups shall be specified. The sensor
amplifier input terminal. Amplifier gains may also be adjusted
locations must be given as soon as possible, to allow position-
as appropr
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: E1211/E1211M − 12 E1211/E1211M − 17
Standard Practice for
Leak Detection and Location Using Surface-Mounted
Acoustic Emission Sensors
This standard is issued under the fixed designation E1211/E1211M; the number immediately following the designation indicates the year
of original adoption or, 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 state source of gas and liquid leaking out of
a pressurized system. The method employs surface-mounted acoustic emission sensors (for non-contact sensors see Test Method
E1002), or sensors attached to the system via acoustic waveguides (for additional information, see Terminology E1316), and may
be used for continuous in-service monitoring and hydrotest monitoring of piping and pressure vessel systems. High sensitivities
may be achieved, although the values obtainable depend on sensor spacing, background noise level, system pressure, and type of
leak.
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two 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 responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E543 Specification for Agencies Performing Nondestructive Testing
E650 Guide for Mounting Piezoelectric Acoustic Emission Sensors
E750 Practice for Characterizing Acoustic Emission Instrumentation
E976 Guide for Determining the Reproducibility of Acoustic Emission Sensor Response
E1002 Practice for Leaks Using Ultrasonics
E1316 Terminology for Nondestructive Examinations
E2374 Guide for Acoustic Emission System Performance Verification
2.2 ASNT Documents:
SNT-TC-1A Recommended Practice for Nondestructive Testing Personnel Qualification and Certification
ANSI/ASNT CP-189 Standard for Qualification and Certification of Nondestructive Testing Personnel
2.3 AIA Document:
NAS 410 Certification and Qualification of Nondestructive Testing Personnel
2.4 ISO Standard:
ISO 9712 Non-Destructive Testing: Qualification and Certification of NDT Personnel
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic Emission
Method.
Current edition approved June 15, 2012June 1, 2017. Published August 2012June 2017. Originally approved in 1987. Last previous edition approved in 20072012 as
E1211 - 07.E1211 - 12. DOI: 10.1520/E1211_E1211M-12.10.1520/E1211_E1211M-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http://www.aia-aerospace.org.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
*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
E1211/E1211M − 17
3. Summary of Practice
3.1 This practice requires 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 being
moved from point to point.
3.2 Detection of a steady-state leak is based on detection of the continuous, broadband signal generated by the leak flow. Signal
detection is accomplished through measurement of some input signal level, such as its root-mean-square (RMS) amplitude or
average signal level.
3.3 The simplest leak test procedure involves only detection of leaks, treating each sensor channel individually. A more complex
examination requires processing the signal levels from two or more sensors together to allow computation of the approximate leak
location, based on the principle that the leak signal amplitude decreases as a function of distance from the source.
4. Significance and Use
4.1 Leakage of gas or liquid from a pressurized system, whether through a crack, orifice, seal break, or other opening, may
involve turbulent or cavitational flow, which generates acoustic energy in both the external atmosphere and the system pressure
boundary. Acoustic energy transmitted through the pressure boundary can be detected at a distance by using a suitable acoustic
emission sensor.
4.2 With proper 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 that
may enhance the acoustic signals used to detect leakage.
4.3 This practice is not intended to provide a quantitative measure of leak rates.
5. Basis of Application
5.1 The following items are subject to contractual agreement between parties using or referencing this practice.
5.2 Personnel Qualification
5.2.1 If specified in the contractual agreement, personnel performing examinations to this practice shall be qualified in
accordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/
ASNT CP-189, SNT-TC-1A, NAS 410, ISO 9712, or a similar document and certified by the employer or certifying agency, as
applicable. 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 Agencies—If specified in the contractual agreement, NDT agencies shall be qualified and
evaluated as described in Practice E543. The applicable edition of Practice E543 shall be specified in the contractual agreement.
5.4 Timing of Examination—The timing of examination shall be in accordance with 7.1.7 unless otherwise specified.
5.5 Extent of Examination—The extent of examination shall be in accordance with 7.1.4 and 10.1.1.1 unless otherwise specified.
5.6 Reporting Criteria/Acceptance Criteria—Reporting criteria for the examination results shall be in accordance with 10.2.2
and Section 11 unless otherwise specified. Since acceptance criteria are not specified in this practice, they shall be specified in the
contractual agreement.
5.7 Reexamination of Repaired/Reworked Items—Reexamination of repaired/reworked items is not addressed in this practice
and if required shall be specified in the contractual agreement.
6. Interferences
6.1 External or internal noise sources can affect the sensitivity of an acoustic emission leak detection system. Examples of
interfering 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 striking the pressure boundary, and
6.1.5 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 in
background noise determines the smallest change in level that can be detected.
6.3 The acoustic emission sensors must have stable characteristics over time and as a function of both the monitoring structure
and the instrumentation system examination parameters, such as temperature.
6.4 Improper sensor mounting, electronic signal conditioner noise, or improper amplifier gain levels can decrease sensitivity.
E1211/E1211M − 17
7. Basic Information
7.1 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 the
capabilities of the method can be evaluated.
7.1.2 Type of vessel, pipeline, or installation to be examined, together with assembly, or layout drawings, or both, giving
sufficient detail to establish dimensions, changes of shape likely to affect flow characteristics, positions of welds, and the location
of components such as valves or flanges, and attachments to the vessel or pipe such as pipe hangers where leaks are most likely
to arise. Regions with restricted accessibility due to walls, the existence or location of cladding, insulation, or below surface
components must be specified.
7.1.3 When location of the peak is of primary interest, quantitative information regarding the leakage rates of interest and
whenever possible the type of leak is necessary.
7.1.4 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 other coating) to allow the acoustic propagation
characteristics of the structure to be evaluated.
7.1.6 Proposed program of pressure application or process-pressure schedule, specifying the pressurization schedule together
with a layout or sketch of the pressure-application system and specifying the type of fluid used during the examination, for
example, 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 be
monitored, or both.
7.1.8 Frequency range to be used in the monitoring equipment.
7.1.9 Environmental conditions 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 couplant materials.
7.1.11 The location of sensors or waveguides and preparation for their installation to provide adequate coverage of the areas
specified in 7.1.3. Where particular sections are to be examined with particular sensors, the coverage of the vessel or system by
sensor subgroups shall be specified. The sensor locations must be given as soon as possible, to allow positioning difficulties to be
identified.
7.1.12 The communications procedure between the acoustic emission staff and the control staff, the time intervals at which
pressure readings are to be taken, and the procedure for giving warning 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. Apparatus
8.1 Sensors—The acoustic emission sensors are generally piezoelectric devices and should be mounted in accordance with
Practice E650 to ensure proper signal coupling. The frequency range of the sensors may be as high as 1 MHz, and either wideband
or resonant sensors may be employed. The higher frequencies can be used to achieve greater discrimination against airborne or
mechanical background noise.
8.2 Amplifiers—Amplifiers
...