ASTM E749/E749M-17(2021)

Standard Practice for Acoustic Emission Monitoring During Continuous Welding

SIGNIFICANCE AND USE
4.1 Detection and location of AE sources in weldments during fabrication may provide information related to the integrity of the weld. Such information may be used to direct repair procedures on the weld or as a guide for application of other nondestructive evaluation (NDE) methods. A major attribute of applying AE for in-process monitoring of welds is the ability of the method to provide immediate real-time information on weld integrity. This feature makes the method useful to lower weld costs by repairing defects at the most convenient point in the production process. The AE activity from discontinuities in the weldment is stimulated by the thermal stresses from the welding process. The AE activity resulting from this stimulation is detected by AE sensors in the vicinity of the weldment, which convert the acoustic waves into electronic signals. The AE instrumentation processes signals and provides means for immediate display or indication of AE activity and for permanent recordings of the data.  
4.2 Items to be considered in preparation and planning for monitoring should include but not be limited to the following:  
4.2.1 Description of the system or object to be monitored or examined,  
4.2.2 Extent of monitoring, that is, entire weld, cover passes only, and so forth,  
4.2.3 Limitations or restrictions on the sensor mounting procedures, if applicable,  
4.2.4 Performance parameters to be established and maintained during the AE system verification procedure (sensitivity, location accuracy, and so forth),  
4.2.5 Maximum time interval between AE system verification checks,  
4.2.6 Performance criteria for purchased equipment,  
4.2.7 Requirements for permanent records of the AE response, if applicable,  
4.2.8 Content and format of test report, if required, and  
4.2.9 Operator qualification and certification, if required.
SCOPE
1.1 This practice provides recommendations for acoustic emission (AE) monitoring of weldments during and immediately following their fabrication by continuous welding processes.  
1.2 The procedure described in this practice is applicable to the detection and location of AE sources in weldments and in their heat-affected zone during fabrication, particularly in those cases where the time duration of welding is such that fusion and solidification take place while welding is still in progress.  
1.3 The effectiveness of acoustic emission to detect discontinuities in the weldment and the heat-affected zone is dependent on the design of the AE system, the AE system verification procedure, the weld process, and the material type. Materials that have been monitored include low-carbon steels, low-alloy steels, stainless steels, and some aluminum alloys. The system performance must be verified for each application by demonstrating that the defects of concern can be detected with the desired reliability.  
1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately 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 standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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-Oct-2021
• ICS: 17.140.20 - Noise emitted by machines and equipment
• ICS: 25.160.01 - Welding, brazing and soldering in general
• ICS: 25.160.10 - Welding processes
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.04 - Acoustic Emission Method

Relations

• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• 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 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
• Refers: ASTM E1316-14e1 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-13d - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2013
• Refers: ASTM E1316-13c - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2013
• Refers: ASTM E1316-13b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2013

Overview

ASTM E749/E749M-17(2021): Standard Practice for Acoustic Emission Monitoring During Continuous Welding details procedures for the acoustic emission (AE) monitoring of weldments during and immediately after fabrication by continuous welding processes. The standard, developed by ASTM Committee E07 on Nondestructive Testing, provides guidance for detecting and locating AE sources in welds and their heat-affected zones, promoting improved weld quality and cost-effective in-process defect handling. Real-time monitoring allows for immediate feedback on weld integrity, supporting timely repair and efficient application of other nondestructive evaluation (NDE) methods.

Key Topics

• Scope and Significance

  • Recommendations for AE monitoring during fabrication by continuous welding.
  • Applicability to detection and location of AE sources in weldments and heat-affected zones.
  • Real-time assessment and immediate data display, enabling fast decision-making and focused repairs.
  • Suitability for materials including low-carbon steels, low-alloy steels, stainless steels, and some aluminum alloys.

• Planning and Preparation

  • System or object description: Clearly define what will be monitored or examined.
  • Extent of monitoring: Determine if this includes the entire weld or specific passes.
  • Sensor mounting: Address limitations or restrictions, ensuring sensors remain operational within specified temperature ranges and are not disturbed by welding equipment.
  • Verification parameters: Establish and maintain AE system criteria such as sensitivity and location accuracy.
  • Operator qualifications: Utilize personnel certified according to recognized NDT qualification practices (e.g., ISO 9712, SNT-TC-1A, ANSI/ASNT CP-189).

• Instrumentation

  • Proper selection and placement of AE sensors for optimal response from weldments.
  • Use of frequency bandpass filters to minimize noise from non-welding sources.
  • Adjustments to system gain and calibration verified through AE simulators.
  • Procedures for single-, two-, or three-channel monitoring, and considerations for stationary or moving sensors.

• Data Recording and Interpretation

  • Requirements for permanent records of AE activity, including equipment settings, sensor locations, and calibration results.
  • Interpretation of AE data against baseline signals from acceptable welds.
  • Need for follow-up NDT methods (visual, ultrasonic, radiography) based on AE monitoring results.
  • Documentation of actions taken (e.g., repairs performed either during or after welding).

Applications

This standard is valuable for professionals in welding fabrication, quality assurance, and maintenance in industries such as:

• Structural Steel Fabrication: Enabling early detection of flaws during the construction of large steel frameworks.
• Pipeline Construction: Monitoring weld integrity during pipeline assembly in oil, gas, and water transport infrastructure.
• Shipbuilding & Aerospace: Ensuring welding quality in critical safety-related applications where reliability is paramount.
• Manufacturing: Supporting an efficient production process with minimal downtime and cost by pinpointing defects when repairs are most convenient.

By applying ASTM E749/E749M-17(2021), organizations can streamline defect detection, minimize the cost of repairs, ensure regulatory compliance, and achieve higher levels of weld quality control.

Related Standards

Acoustic emission monitoring during continuous welding is closely linked to a range of NDE and personnel qualification standards, including:

• ASTM E543: Specification for Agencies Performing Nondestructive Testing
• ASTM E569: Practice for Acoustic Emission Monitoring of Structures During Controlled Stimulation
• ASTM E650: Guide for Mounting Piezoelectric Acoustic Emission Sensors
• ASTM E1316: Terminology for Nondestructive Examinations
• ASNT SNT-TC-1A and ANSI/ASNT CP-189: Recommended practices and standards for NDT personnel qualification and certification
• AIA NAS-410: Certification and Qualification of Nondestructive Testing Personnel
• ISO 9712: Qualification and Certification of NDT Personnel

These related standards provide a comprehensive framework for AE monitoring, personnel qualification, and equipment verification, helping organizations execute continuous welding projects that meet rigorous quality and safety requirements.

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: E749/E749M − 17 (Reapproved 2021)
Standard Practice for
Acoustic Emission Monitoring During Continuous Welding
This standard is issued under the fixed designation E749/E749M; 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* 2. Referenced Documents
1.1 This practice provides recommendations for acoustic 2.1 ASTM Standards:
emission (AE) monitoring of weldments during and immedi- E543 Specification for Agencies Performing Nondestructive
ately following their fabrication by continuous welding pro- Testing
cesses. E569 Practice for Acoustic Emission Monitoring of Struc-
tures During Controlled Stimulation
1.2 The procedure described in this practice is applicable to
E650 Guide for Mounting Piezoelectric Acoustic Emission
the detection and location of AE sources in weldments and in
Sensors
their heat-affected zone during fabrication, particularly in those
E1316 Terminology for Nondestructive Examinations
cases where the time duration of welding is such that fusion
2.2 ASNT Standards:
and solidification take place while welding is still in progress.
SNT-TC-1A Recommended Practice for Nondestructive
1.3 The effectiveness of acoustic emission to detect discon-
Testing Personnel Qualification and Certification
tinuities in the weldment and the heat-affected zone is depen-
ANSI/ASNT CP-189 Standard for Qualification and Certifi-
dentonthedesignoftheAEsystem,theAEsystemverification
cation of Nondestructive Testing Personnel
procedure, the weld process, and the material type. Materials
2.3 AIA Standard:
that have been monitored include low-carbon steels, low-alloy
NAS-410 Certification and Qualification of Nondestructive
steels, stainless steels, and some aluminum alloys. The system
Personnel (Quality Assurance Committee)
performance must be verified for each application by demon-
2.4 ISO Standard:
strating that the defects of concern can be detected with the
ISO 9712 Non-Destructive Testing: Qualification and Certi-
desired reliability.
fication of NDT Personnel
1.4 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The
3. Terminology
values stated in each system may not be exact equivalents;
3.1 Definitions—For definitions of terms relating to acoustic
therefore, each system shall be used independently of the other.
emission testing, see Section B of Terminology E1316.
Combining values from the two systems may result in non-
conformance with the standard.
4. Significance and Use
1.5 This standard does not purport to address all of the
4.1 Detection and location of AE sources in weldments
safety concerns, if any, associated with its use. It is the
during fabrication may provide information related to the
responsibility of the user of this standard to establish appro-
integrity of the weld. Such information may be used to direct
priate safety, health, and environmental practices and deter-
repair procedures on the weld or as a guide for application of
mine the applicability of regulatory limitations prior to use.
other nondestructive evaluation (NDE) methods. A major
1.6 This international standard was developed in accor-
attribute of applying AE for in-process monitoring of welds is
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
mendations issued by the World Trade Organization Technical
Standards volume information, refer to the standard’s Document Summary page on
Barriers to Trade (TBT) Committee.
the ASTM website.
AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
1 4
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
structive Testing and is the direct responsibility of Subcommittee E07.04 on WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
Acoustic Emission Method.
Current edition approved Nov. 1, 2021. Published November 2021. Originally Available from International Organization for Standardization (ISO), ISO
approved in 1980. Last previous edition approved in 2017 as E749/E749M – 17. Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
DOI: 10.1520/E0749_E0749M-17R21. 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
E749/E749M − 17 (2021)
the ability of the method to provide immediate real-time near the weldment to provide for optimalAE response from all
information on weld integrity. This feature makes the method portions of the weld. If the sensor(s) are piezoelectric, this
useful to lower weld costs by repairing defects at the most location should be such that the maximum temperature stays
convenient point in the production process. The AE activity below manufacturers’specifications of the sensor(s). Take care
from discontinuities in the weldment is stimulated by the in selecting the sensor mounting locations to avoid contact or
thermal stresses from the welding process. The AE activity disturbance, or both, of the sensor by any of the welding or
resulting from this stimulation is detected byAE sensors in the structuralpositioningequipment.Typicaldistancesfrom150to
vicinity of the weldment, which convert the acoustic waves 300 mm [6 to 12 in.] from the heat-affected zone of the weld
into electronic signals. The AE instrumentation processes are usually satisfactory. Typical fixed sensor placement pat-
signals and provides means for immediate display or indication terns that have been successfully used are shown in Figs. 1-3.
of AE activity and for permanent recordings of the data. 6.1.1.1 If a fixed contact sensor(s) is used, clean the area(s)
where attachment will be made to eliminate loose scale,
4.2 Items to be considered in preparation and planning for
welding flux, or other debris, and attach the sensor in accor-
monitoring should include but not be limited to the following:
dance with Guide E650.
4.2.1 Description of the system or object to be monitored or
6.1.1.2 If moving sensors are used, clean the coupling path
examined,
so that uniform sensitivity is maintained as the sensor moves.
4.2.2 Extent of monitoring, that is, entire weld, cover passes
Fig. 4 shows side and top views of a typical configuration for
only, and so forth,
moving sensors.
4.2.3 Limitations or restrictions on the sensor mounting
6.1.2 Position and route the signal cables connecting the
procedures, if applicable,
sensor(s) to theAE instrumentation to avoid contacting the hot
4.2.4 Performance parameters to be established and main-
weld bead or entangling the welding and positioning equip-
tained during theAE system verification procedure (sensitivity,
ment.
location accuracy, and so forth),
6.1.3 Adjustment of Apparatus:
4.2.5 Maximum time interval between AE system verifica-
6.1.3.1 After all sensors are mounted, connected, and op-
tion checks,
erational (without objectionable background noise), the AE
4.2.6 Performance criteria for purchased equipment,
monitoring system can then be adjusted using anAE simulator.
4.2.7 Requirements for permanent records of the AE
6.1.3.2 Gain Adjustment—To set or select the overall gain
response, if applicable,
for a channel (if necessary), locate the acoustic emission
4.2.8 Content and format of test report, if required, and
simulator at a selected distance adjacent to the sensor. Monitor
4.2.9 Operator qualification and certification, if required.
the response to the simulated emission, and adjust the overall
channel gain to a specified amplitude level. Repeat this
5. Basis of Application
proceduretwotimes,placingthesimulatoratthesamedistance
5.1 The following items are subject to contractual agree-
from the sensor but at different azimuthal positions relative to
ment between the parties using or referencing this practice.
theoriginalsimulatorpositions(seeFig.5).Recordtheaverage
5.2 Personnel Qualification: gain for the three simulator positions. Repeat the entire
5.2.1 If specified in the contractual agreement, personnel
procedure for each AE sensor on the structure, and adjust the
performing examinations to this standard shall be qualified in gains.The average gains for all channels should give responses
accordance with a nationally or internationally recognized
to the simulator that have peak voltages identical to within 63
NDT personnel qualification practice or standard such as
dB.
ANSI/ASNT CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a
6.1.4 Determination of Source-Location Accuracy—Check
similar document and certified by the employer or certifying
the operation of the AE source-location function by analyzing
agency, as applicable. The practice or standard used and its
simulated AE signals from several random locations in the
applicable revision shall be identified in the contractual agree-
weld and on the structure, as well as from any specific critical
ment between the using parties.
locations. For each placement of the simulator, determine and
record the precision and accuracy of the AE location function.
5.3 Qualification of Nondestructive Agencies—If specified
It should be noted that the accuracy of locating the simulator
in the contractual agreement, NDT agencies shall be qualified
sourcewillnotnecessarilybethesameasforlocatingarealAE
and evaluated as described in Practice E543. The applicable
source. Du
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