ISO 24367:2023

Non-destructive testing - Acoustic emission testing - Metallic pressure equipment

This document specifies an acoustic emission testing (AT) technique for metallic pressure equipment and the classification and evaluation of results. This document applies to acoustic emission (AE) detection and monitoring of active sources of newly manufactured and in-service metallic pressure equipment. This document does not apply to leak detection and in-service monitoring using AE. This testing method is not intended to be a stand-alone method for testing and evaluation of the pressure equipment. Other non-destructive testing (NDT) methods may be used to verify and supplement the AT results.

Essais non destructifs — Contrôle par émission acoustique — Équipements sous pression métalliques

General Information

• Status: Published
• Publication Date: 05-Dec-2023
• ICS: 19.100 - Non-destructive testing
• Technical Committee: ISO/TC 135/SC 9 - Acoustic emission testing
• Drafting Committee: ISO/TC 135/SC 9/WG 8 - Acoustic emission testing of metallic structures
• Current Stage: 6060 - International Standard published
• Start Date: 06-Dec-2023
• Due Date: 30-May-2023
• Completion Date: 06-Dec-2023

Overview

ISO 24367:2023 - Non-destructive testing - Acoustic emission testing - Metallic pressure equipment establishes requirements for acoustic emission (AE) testing of metallic pressure equipment. The standard defines an AE testing (AT) technique, the classification and evaluation of AE results, and requirements for equipment, on-site operation and documentation. It applies to AE detection and monitoring of active sources in newly manufactured and in‑service pressure equipment, but does not apply to leak detection or continuous in‑service AE monitoring. ISO 24367:2023 is not intended as a stand‑alone NDT method; other non‑destructive testing (NDT) techniques are expected to verify and supplement AT results.

Key Topics and Requirements

• Scope and limits: AE for metallic pressure-bearing shells (boilers, pressure vessels, piping, safety valves); excludes leak detection workflows.
• Personnel qualification: Competence requirements for AE operators and analysts.
• Testing equipment: Specifications and verification for AE systems, sensors, signal/power cables, preamplifiers, filters, couplant and instruments; maintenance and calibration guidance.
• On-site operation: Pre‑test preparation (preliminary information, site investigation), sensor array design and mounting, pressurization sequences, determination of system testing threshold and attenuation curve.
• Instrument settings & checks: Sensitivity checks, verification of location systems, intensity analysis and stop criteria for live testing.
• Data handling: Data acquisition, on‑line and off‑line analysis, AE clustering and source location (zone/planar/computed methods).
• Classification & evaluation: Defined classification methods for AE sources, determination of activity/intensity, and interpretation rules to support decision making.
• Acceptance criteria & documentation: Requirements for test instructions, records and final test reports; Annex with sensor placement guidelines.

Applications and Who Uses It

ISO 24367:2023 is intended for practical use in:

• NDT service providers performing proof testing and manufacturing inspections
• Plant owners / asset integrity teams managing pressure vessels and piping
• Inspection bodies and regulators setting test procedures and acceptance criteria
• Maintenance and reliability engineers integrating AE results with other NDT methods
  Use cases include locating active discontinuities in welds and parent metal during proof tests, supporting fitness-for-service decisions, and guiding follow‑up inspections using complementary NDT (UT, RT, PT).

Related Standards

ISO 24367 references and complements existing AE and NDT standards such as ISO 12714, ISO 12716, ISO/TR 13115, and relevant EN standards for AE equipment and AE location methods (e.g., EN 14584, EN 15495, EN 13477 series). These form a useful normative framework when implementing AE for metallic pressure equipment.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 24367
First edition
2023-12
Non-destructive testing — Acoustic
emission testing — Metallic pressure
equipment
Essais non destructifs — Contrôle par émission acoustique —
Équipements sous pression métalliques
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General principles . 3
5 Personnel qualification .3
6 Testing equipment . 3
6.1 Acoustic emission testing system. 3
6.2 Acoustic emission sensors . 4
6.3 Acoustic emission signal cables . 4
6.4 Couplant . 4
6.5 Preamplifiers . 4
6.6 Power signal cables . 4
6.7 Filters . 5
6.8 Acoustic emission instrument . 5
6.9 Maintenance and verification of testing equipment . 6
6.10 Pressure gauge . 6
7 On-site operation .6
7.1 Preparation . 6
7.1.1 Preliminary information . 6
7.1.2 Site investigation . 7
7.1.3 Preparation of acoustic emission testing instruction and record sheets . 7
7.1.4 Determination of the system testing threshold . 7
7.1.5 Determination of the attenuation curve . 7
7.1.6 Sensor array . 7
7.1.7 Pressurization sequence . 8
7.2 Sensor mounting . 8
7.3 Settings of the acoustic emission instrument. 8
7.3.1 General requirements . 8
7.3.2 Sensitivity check . 8
7.3.3 Verification of the location system . . 9
7.3.4 Intensity analysis . 9
7.4 Performing the test. 9
7.4.1 Pressurization sequence . 9
7.4.2 Data acquisition and observations during acoustic emission testing . 11
7.4.3 On-line data analysis and stop criteria .12
8 Interpretation and evaluation of AE data .13
8.1 General .13
8.2 Off-line data analysis .13
8.3 Classification of the acoustic emission sources of the test object . 14
8.3.1 Determination of the area of an acoustic emission cluster or zone . 14
8.3.2 Classification system for acoustic emission sources . 14
8.3.3 Classification method 1 . 15
8.3.4 Classification method 2 . 17
8.3.5 Classification method 3 . 18
9 Acceptance criteria .21
10 Documentation .21
10.1 General . 21
10.2 Written acoustic emission testing instruction . 22
iii
10.3 Test records .22
10.4 Test report . 23
Annex A (informative) Guidelines for acoustic emission sensor placement .24
Bibliography .27
iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 9, Acoustic emission testing.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
Industrial applications of acoustic emission testing for pressure equipment are expanding along
with remarkable improvement of acoustic emission testing technologies. The effectiveness of any
application of acoustic emission testing depends upon proper and correct usage of the acoustic emission
instruments and testing techniques. In addition, the existing international acoustic emission standards
lack specification of a classification system with associated recommendations for maintenance.
The purpose of this document is to provide requirements for testing equipment, testing procedures and
the classification system for acoustic emission testing of pressure equipment in the field of industrial
non-destructive testing. The establishment of this document can address the lack of an ISO standard
for acoustic emission testing for pressure equipment. The main parties who might benefit from this
document are testing organizations and owners/users of pressure equipment.
vi
INTERNATIONAL STANDARD ISO 24367:2023(E)
Non-destructive testing — Acoustic emission testing —
Metallic pressure equipment
1 Scope
This document specifies an acoustic emission testing (AT) technique for metallic pressure equipment
and the classification and evaluation of results.
This document applies to acoustic emission (AE) detection and monitoring of active sources of newly
manufactured and in-service metallic pressure equipment.
This document does not apply to leak detection and in-service monitoring using AE.
This testing method is not intended to be a stand-alone method for testing and evaluation of the pressure
equipment. Other non-destructive testing (NDT) methods may be used to verify and supplement the AT
results.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 12714, Non-destructive testing — Acoustic emission inspection — Secondary calibration of acoustic
emission sensors
ISO 12716, Non-destructive testing — Acoustic emission inspection — Vocabulary
ISO/TR 13115, Non-destructive testing — Methods for absolute calibration of acoustic emission transducers
by the reciprocity technique
EN 14584:2013, Non-destructive testing —Acoustic emission testing — Examination of metallic pressure
equipment during proof testing — Planar location of AE sources
EN 15495, Non-destructive testing — Acoustic emission — Examination of metallic pressure equipment
during proof testing — Zone location of AE sources
EN 13477-1, Non-destructive testing — Acoustic emission — Equipment characterisation — Part 1:
Equipment description
EN 13477-2, Non-destructive testing — Acoustic emission — Equipment characterisation — Part 2:
Verification of operating characteristic
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12716 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
acoustic emission testing
AT
testing of a test object during controlled stimulation using acoustic emission instrumentation to detect
and analyse sources of acoustic emission
3.2
acoustic emission source
AE source
spatial element in the material where transient elastic waves are generated by the release of energy
3.3
acoustic emission source location
AE source location
determination of the spatial position of an AE source (3.2) at the test object based on the arrival time
measurement using an array of sensors
Note 1 to entry: Several approaches to AE source location are used, including zonal location, computed location
and continuous location. The spatial element can be represented by one or more location clusters in planar or
linear location when using computed location method based on time difference or by a location zone when using
zone location
3.4
activity of acoustic emission source
activity of AE source
total number of AE events obtained from one or more location clusters or zones assigned to one AE
source at a certain spatial area of the test object
3.5
intensity of acoustic emission source
intensity of AE source
characterization of the AE source (3.2) by using intensity related parameters from one or more location
clusters or zones assigned to one AE source at a certain spatial area of the test object
Note 1 to entry: Intensity of AE source for burst related parameters are, e.g. peak amplitude, energy, ring-down
counts
3.6
active discontinuity
discontinuity which is generating transient elastic waves under controlled stimulation
3.7
pressure equipment
steam boilers, pressure vessels, piping, safety valves and other components and assemblies subject to
pressure loading
3.8
Hsu-Nielsen source
device to simulate an AE event using the fracture of a brittle graphite lead in a suitable fitting
Note 1 to entry: Device given in Figure 1
Key
1 pencil
2 guide ring
3 graphite lead
hardness grade 2H
diameter 0,5 mm
length 3 mm ± 0,5 mm
Figure 1 — Hsu-Nielsen source
3.9
acoustic emission detectability parameter
K
AE
difference between the evaluation threshold and the system testing threshold in units dB
4 General principles
The main purpose of AT on pressure equipment is to detect and to locate AE sources within the volume
or at the surface of the parent metal or welds.
a) The AT shall comprise 100 % of the pressure-bearing shell. Only in exceptional cases and when not
directly affecting the safe pressurization of the equipment, the AT may be limited to specific parts
agreed upon with the owner/operator at the time of enquiry or order.
b) The AT shall be done during the loading process, which includes the pressure loading, load holding
unloading and reloading.
c) The AE sensors shall be arranged on the surface of pressure equipment under test in order to detect
the transient elastic waves released by AE sources and transform them into electric signals.
d) These electricals signals shall be conditioned and transmitted to an AE instrument for measuring,
recording, interpretation and evaluation.
5 Personnel qualification
The AT shall be performed by competent personnel. In order to ensure that this is the case, it is
recommended that the personnel meet the requirements of ISO 9712 or equivalent.
6 Testing equipment
6.1 Acoustic emission testing system
An AT system employs an AE instrument, AE sensors, preamplifiers, and interconnecting cables.
This combination together with mounting devices for holding the sensors forms the AT system.
All essential parts of the system shall be specified in a written AT instruction agreed between purchaser
and supplier at the time of enquiry or order (see 10.2).
6.2 Acoustic emission sensors
It is recommended to use sensors in the frequency range between 100 kHz and 400 kHz.
A lower frequency range for sensors can be advantageous in case of high attenuation.
The requirements are as follows.
-1
a) The minimum sensitivity shall be equivalent or greater than 60 dB referred to 1 V/(m∙s ).
b) Sensors shall be shielded against electromagnetic interference by proper shielding practice or
by differential element design, or both. The metallic case of each AE sensor shall be electrically
isolated from a metallic test object.
c) The AE sensors shall be stable over the response frequency and temperature range of use, and shall
not exhibit sensitivity changes greater than 3 dB over this range.
d) The verification of the sensors should be performed according to ISO 12714 or with ISO/TR 13115
when applicable.
e) AE sensors mounted on the surface of pressure equipment shall be electrically insulated from each
other.
6.3 Acoustic emission signal cables
The AE signal cables connecting sensors and preamplifiers shall be shielded against electromagnetic
interference. Its length shall not exceed 1 m, unless the length-depending signal loss is considered and
acceptable. This may be omitted where the preamplifier is mounted inside the shielded sensor housing.
6.4 Couplant
The couplant shall aid to keep good surface motion tracking and minimum acoustic impedance transfer
effect during testing.
6.5 Preamplifiers
The preamplifiers may be separate or may be mounted inside the sensor housing.
The requirements are as follows.
a) The RMS voltage of preamplifiers circuit noise shall be less than 7 μV.
b) The preamplifiers shall be stable over the response frequency and temperature range of use, and
shall not exhibit gain changes greater than 3 dB over this range.
c) The preamplifiers response frequency shall match with that of the sensors, and the gain of the
preamplifiers, usually 40 dB or 34 dB, shall not cause saturation of the measurement chain up to a
100 dB signal peak amplitude.
AE
d) If the preamplifiers are of differential design, a minimum of 40 dB of common-mode rejection shall
be provided.
6.6 Power signal cables
The signal loss of cables depends on type of cable, frequency and length. The requirements are as
follows.
a) The cable providing power to the preamplifier and conducting the amplified signal to the main
processor shall be shielded against electromagnetic noise.
b) Signal loss shall be no more than 1 dB per 30 m of cable length.
c) With cable length above 30 m, the resulting attenuation and the voltage drop-off of the DC-supply
shall be evaluated and considered in the data analysis.
d) 150 m is the recommended maximum cable length to avoid excessive signal attenuation.
6.7 Filters
The response frequency of filters in the preamplifiers and the AE instrument shall match with that of
the AE sensors.
6.8 Acoustic emission instrument
The requirements for AE instruments are as follows.
a) The AE instrument shall have enough AE channels to cover the area to be tested.
b) For each channel, the AE instrument shall display and record arrival time, threshold, peak
amplitude, ring-down count, energy, rise time, and duration for each hit as a minimum.
c) The individual sampling frequency of each channel for acquisition of waveforms shall be not less
than 10 times the sensors’ centre response frequency.
d) The measurement inaccuracy for threshold above 40 dB shall not exceed ±1 dB.
AE
e) The measurement inaccuracy for ring-down counts shall not exceed ±5 %.
f) The AE instrument shall be capable to process, store and display at least 20 hits per second and per
channel.
g) The delay and display from the arrival of the AE hits shall not exceed 2 seconds.
h) An alarm shall occur if the hit rate exceeds the capability of the instrument.
i) A warning shall occur when the storage space runs short.
j) The measurement inaccuracy for peak amplitudes above 40 dB shall not exceed ±1 dB.
AE
k) The usable dynamic range shall be a minimum of 65 dB.
l) The measurement inaccuracy for energy above 40 dB shall not exceed ±5 %.
AE
m) The resolution of the rise time, duration and arrival time for each channel shall not exceed 1 μs.
n) The error of arrival time measurement between all channels shall be not more than 2 µs.
o) The electronic noise levels shall be equal to or below 20 dB in the frequency range from 100 kHz
AE
to 400 kHz.
p) It is preferred that the instrument is able to receive and record also external electric signals, such
as pressure and temperature. The measurement inaccuracy for the external parametric inputs
shall not exceed 1 % of the full range.
q) During data acquisition, AE software shall be capable to display the following diagrams:
1) any AE parameter versus time or load;
2) one AE parameter versus another AE parameter;
3) linear, planar and/or zone locations.
r) The update time for all real-time testing diagrams shall be not more than 5 s.
s) The AE analysis software shall provide functions to replay and to analyse the recorded AT data.
1) Linear and planar location algorithms shall be provided by the AT system manufacturer. Event
location in this regard is based on Δt measurements and processes the sensor positions as
well as the speed of sound. Application of linear location requires at least two sensors, and
application of planar location requires at least three sensors.
2) Zone location is based on arrival sequence of channels. The event shall be assigned to the first
hit sensor location.
6.9 Maintenance and verification of testing equipment
The performance of the AT system shall be verified at specified intervals in conformity with the
methods provided by the manufacturer of the AE instrument, or refer to EN 13477-1 and EN 13477-2.
6.10 Pressure gauge
The requirements are as follows.
a) A pressure gauge shall be installed on the pressure equipment prior to the test. It is recommended
to use a pressure gauge with valid calibration certificate.
b) The pressure gauge shall have a range that is between 1,5x and 2x the maximum test pressure.
c) The pressure reading from the control room may be used provided a printout and/or digital data,
both covering the total test period, are made available.
d) The accuracy of the pressure gauge shall be within 1 % of full range.
7 On-site operation
7.1 Preparation
7.1.1 Preliminary information
a) Prior to the testing, the following shall be specified:
1) the purpose of the test and the amount of testing, e.g. 100 % of the pressure-bearing shell;
2) the details of the pressure equipment to be tested;
3) the physical location of the area where the test shall be performed;
4) the requirements for surface preparation;
5) the acceptance criteria;
6) the requirements of the test report;
7) the details of qualification of test personnel;
b) The following documents for the pressure equipment to be tested shall be provided by the owner/
operator before performing an AT:
1) manufacturing documents, e.g. declaration of conformity, drawing documents;
2) operation recording documents, e.g. operating conditions and parameters, medium, loading
fluctuations, abnormal situation in operation;
3) previous inspection and testing reports;
4) repairs, modifications and maintenance documents.
7.1.2 Site investigation
Prior to testing, a site investigation shall be carried out to find all interference factors, such as friction
of scaffold, electromagnetic interference, vibration. The interference of these factors shall be eliminated
or sufficiently reduced during on-site testing.
7.1.3 Preparation of acoustic emission testing instruction and record sheets
The AT instruction and record sheets shall be prepared in accordance with the AT procedure, pressure
equipment and site conditions. The instrument, applicable sensors, testing place, surface conditions
and pressurization cycle of the pressure equipment shall be specified.
7.1.4 Determination of the system testing threshold
The determination of the system testing threshold shall meet the following requirements.
a) The background noise of the testing environment shall be determined by lowering the system
testing threshold to obtain the hit rate of not more than 1 hit per second for each and every channel.
b) The background noise measurement of newly manufactured pressure equipment and in-service
pressure equipment being off-line shall be not less than 5 min.
c) For the in-service pressure equipment being on-line, the measurement shall be not less than 15 min.
d) The system testing threshold of each channel shall be higher than the background noise by at least
6 dB.
e) If the background noise level is close to AE signal peak amplitude caused by the active discontinuities
in the pressure equipment, the background noise shall be reduced or eliminated, or the sensor
spacing shall be reduced, otherwise it is not suitable to perform the AT.
7.1.5 Determination of the attenuation curve
The attenuation of the AE waves on the test pressure equipment to be tested shall be determined. This
is necessary for determining the sensor spacing for effective detection of AE sources and recalculation
of signal peak amplitude to source location.
The attenuation shall be determined away from the discontinuous structure such as manholes and
nozzles using simulated AE sources.
The procedure for the correction of signal peak amplitudes with distance shall be done according to
EN 14584:2013, Annex A.
If attenuation data from the same testing conditions are already available, it is not necessary to
determine the attenuation again, but the attenuation data shall be indicated in the record sheets and
the test report.
7.1.6 Sensor array
The requirements are as follows.
a) A sufficient number of sensors shall be mounted on the surface of the pressure equipment to enable
AE signal detection and source location, according to the dimension of the equipment and the
purpose of the testing.
b) The allowed maximum sensor spacing shall be determined based on measured attenuation curve
of AE peak amplitude, in accordance with EN 14584 and EN 15495.
c) The spacing difference between adjacent sensors in the same triangle or square array shall be as
low as possible.
d) All the sensors shall be numbered and indicated in the schematic diagram of the pressure
equipment to be tested. Annex A provides guidelines for sensor placement for some types of
pressure equipment.
7.1.7 Pressurization sequence
The requirements are as follows.
a) The pressurization sequence shall be established according to the purpose of AT and the real
condition of the pressure equipment.
b) The communication of the AT operator with the pressurization operator shall be included in the AT
instruction.
7.2 Sensor mounting
The mounting of sensors shall meet the following requirements.
a) The sensors shall be installed according to the specified sensor array. The sensors shall keep a
minimum distance of 50 mm to manholes, nozzles, flanges, supports, pillars, backing plates and
welds during the whole testing of the pressure equipment. For local testing the testing area shall be
near but not in the centre of the sensor array.
b) The place for the mounting of a sensor on the structure shall be smooth and showing the metallic
lustre. The coating can be kept when it is smooth and compacted and the determined attenuation is
acceptable.
c) Efficient couplants such as vacuum grease or petroleum jelly are recommended.
d) The temperature class of the couplant shall be matched to the surface temperature of the pressure
equipment.
e) Firmly fixing of the sensors with the pressure equipment shall be performed by a magnetic holding
device, by an adhesive tape or other method, keeping the electrical insulation.
f) For low-temperature or high-temperature pressure equipment, AE waveguides (rods) shall be used
to improve the coupling temperature of the sensor.
g) The effect of the waveguide on the attenuation and localization characteristics of the AE signals
shall be determined.
7.3 Settings of the acoustic emission instrument
7.3.1 General requirements
Connect the sensors and preamplifiers with the corresponding input channels of the AE instrument by
cables, turn on the AE instrument and wait until the testing equipment is in proper working condition.
7.3.2 Sensitivity check
The sensitivity of each channel shall be checked using a simulated AE source.
The requirements are as follows:
a) The simulated AE source shall be the Hsu-Nielsen source.
b) The detected peak amplitude of the simulated event shall be at a fixed distance from the centre of
the sensor, and the responsive value shall be the average of more than 3 measurements.
c) The generated AE signal shall have a peak amplitude of at least 90 dB at a distance of
AE
50 mm ± 5 mm from the centre of the sensor.
d) The average peak amplitude of any sensor shall be within ±3 dB of the average of all sensors.
e) The sensitivity check for all channels shall be done before and after the testing. The use of an
electronic pulser to check that there is no subsequent change in sensitivity, by comparison with
that obtained prior to the test, is an acceptable alternative to repeating the Hsu-Nielsen source
check.
7.3.3 Verification of the location system
The verification of the location system shall meet the following requirements.
a) When using the computed localization, the simulated AE source, i.e. a Hsu-Nielsen source minus
the AE detectability parameter K , shall be received at least by the minimum number of sensors
AE
required by the used location algorithm, and shall be located solely within the sensor array on the
test object. The error of location shall be no more than ±5 % of the sensors spacing.
b) When using the zone location, the simulated AE source shall be received by at least one sensor in
that area.
7.3.4 Intensity analysis
For the intensity analysis of Δt-based located events, the peak amplitude at the point of source shall be
derived from the measured peak amplitude at the first-hit sensor and the calculated distance from the
first-hit sensor to the calculated point of source, as described in EN 14584:2013, Annex A.
7.4 Performing the test
7.4.1 Pressurization sequence
7.4.1.1 General requirements
The pressurization sequence shall generally meet the following requirements.
a) For newly manufactured pressure equipment, the pressurized medium shall be water or another
safe medium.
b) For in-service pressure equipment being off-line, the pressurized medium shall be water, gas
utilized during the process, inert gas such as nitrogen or another safe medium.
c) For in-service pressure equipment being on-line, the pressurized medium shall be its working
medium.
d) The highest test pressure and pressurization sequence for AT shall be determined by the operating
manual and design documents of the pressure equipment, relevant safety technical specifications,
standards and contractual requirements.
e) The rates of pressurization shall be determined by the operating manual, design documents or
design standards of the pressure equipment. If there is no special requirement, it shall be generally
not more than 5 % of highest test pressure per minute in case of hydraulic pressurization and not
more than 1 % of highest test pressure per minute in case of pneumatic pressurization.
f) If the AE signal appears continuously during the pressurization or hold period with a large number,
the pressurization shall be stopped or reduced as soon as possible and the cause for the high
activity of the AE source shall be investigated.
g) If the AE signal appears continuously during the hold period with a small number, the hold period
shall be extended appropriately until the AE signals converge.
h) The hold period shall be terminated early if no AE signal appears within 5 min.
7.4.1.2 Pressurization sequence for newly manufactured pressure equipment
The AT of the newly manufactured pressure equipment may be carried out during the hydrostatic
pressure test.
Figure 2 gives an example for the pressurization sequence for newly manufactured pressure equipment.
The pressurization sequence shall meet the following requirements.
a) The AT shall start before the equipment pressure reaches 20 % of the design pressure P (or
D
nominal pressure or rated working pressure).
b) The pressure shall be held at least 10 min when the pressure reaches the design pressure P and at
D
least 30 min for the highest test pressure P . P shall be equal to the hydraulic test pressure.
T1 T1
c) If the first loading data indicates a possible active discontinuity or is inconclusive, the equipment
shall be repressurized from P .
D
d) The highest test pressure of the second pressurization P shall be above 97 % of P and below
T2 T1
P .
T1
Key
X time
Y pressure
1 P the highest test pressure of the first pressurization
T1,
2 P the highest test pressure of the second pressurization
T2,
3 P the design pressure
D,
Figure 2 — Example of the pressurization sequence for newly manufactured pressure
equipment (minimum requirement)
7.4.1.3 Pressurization sequence for in-service pressure equipment
Figure 3 gives an example for the pressurization sequence for in-service pressure equipment.
a) For in-service pressure equipment being off-line, the pressurization sequence shall meet the
following requirements.
1) The highest test pressure P shall be at least 110 % of the maximum working pressure P of
T1 W
past 12 months. The pressure equipment operator shall provide this information on basis of
operational data in digital format or as print-out covering the past 12 months period prior to
the date of test.
2) The AT shall start before the equipment pressure reaches 50 % of the maximum working
pressure.
3) The pressure shall be held at least for 30 min when the pressure reaches the highest test
pressure P .
T1
4) If the first loading data indicates a possible active discontinuity or is inconclusive, the
equipment shall be repressurized from 50 % of the P .
T1
5) The highest test pressure of the second pressurization P shall be above 97 % of P and below
T2 T1
P .
T1
b) For in-service pressure equipment being on-line, the pressurization sequence shall meet the
following requirements.
1) The highest test pressure P shall be at least 110 % of the maximum working pressure P
T1 W
of past 12 months. The pressure equipment operator shall provide this information on basis
of operational data in digital format or as print-out covering the past 12 months period prior
to the date of test. The highest test pressure P shall be lower than the design pressure P . If
T1 D
these requirements are not possible, it shall be considered to take the pressure equipment out
of operation and apply the procedure described under 7.4.1.3 a).
2) The working pressure shall be reduced as low as possible at least 5 days prior to AT to the start
test pressure P .
TS
3) The AT shall start at the beginning of the pressurization.
4) The pressure shall be held at least for 10 minutes when the pressure reaches the maximum
working pressure P and at least for 30 minutes for the highest test pressure P .
W T1
Key
X time
Y pressure
1 P the highest test pressure
T1,
2 P the maximum working pressure
W,
3 P the start test pressure
TS,
Figure 3 — Example of the pressurization sequence for in-service pressure equipment
(minimum requirement)
7.4.2 Data acquisition and observations during acoustic emission testing
The requirements for data acquisition and observations during AT are as follows:
a) The data acquisition shall include the parameters given in 6.8 b).
b) Using software filters or graphic data display analysis methods, the non-correlated AE signals shall
be separated from relevant AE signals, and indicated in the test records.
c) For AE source location clusters in computed location method based on time difference, the spatial
area shall be confirmed by simulated AE sources.
d) The arrival times of AE signals shall be collected when using source location based on the time
difference between channels.
e) The trend of the AE hits and/or AE events versus time shall be observed during the test.
f) For an area bristled with located AE events, it shall be checked whether there is external
interference.
g) During the test, the background noise shall be monitored. Periods of obvious noise interference
shall be marked.
7.4.3 On-line data analysis and stop criteria
7.4.3.1 General
In the process of AT, the AE signals shall be observed and analysed on-line for the whole duration of
the test. If disturbance noise occurs during the testing, it shall be treated according to 7.4.3.2. Data
observations and analysis during testing shall be performed according to 7.4.2 and 7.4.3.3.
7.4.3.2 Noise during testing
Attention must be given to the following factors that can affect the testing results:
a) injection of medium;
b) excessively high pressurization rate;
c) external mechanical vibration;
d) movement or pressure burst of internal components, tooling, scaffolding, apparatus;
e) electromagnetic interference;
f) weather conditions, such as interference from wind, rain, hail;
g) leakage.
7.4.3.3 Data analysis during testing
The trend of the AE hits versus pressure or time shall be observed during the test.
For source location based on time difference between channels, the trend of located AE events versus
pressure or time shall be observed during the test. For an area with widespread located AE sources, it
shall be checked whether there is external interference.
7.4.3.4 Stop criteria
A decision to stop the test shall be made in the case of increasing the activity of the AE source and/or
intensity of the AE source during a loading sequence.
a) If there is a large amount of AE signals during loading, the pressurization shall be stopped and the
testing shall be paused.
b) If AE signals with very high peak amplitudes appear during the testing (depends on the material
and construction of the pressurized equipment), the pressurization shall be stopped and the testing
shall be paused.
c) After reaching pressure hold, if AE signals are still being generated, there is a possibility of crack
propagation without further loading. The pressure shall be decreased until no new AE signal is
generated.
The AT operator shall investigate the reasons for these AE signals through data analysis and on-site
observation. If necessary, other non-destructive testing methods may be required for clarifying the
found indication. If a noise si
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