kSIST FprEN 17391:2021

Non-destructive testing - Acoustic emission testing – In-service acoustic emission monitoring of metallic pressure equipment and structures - General requirements

This standard describes acoustic emission (AE) monitoring for in service detection, location and grading of AE sources with application to metallic pressure equipment and structures. The monitoring can be periodic, temporary or continuous, on site or remote controlled, supervised or automated. The objectives of AE monitoring are to define regions which are acoustically active as a result of damage or defect evolution.

Zerstörungsfreie Prüfung - Schallemissionsprüfung - Überwachung der Schallemission von metallischen Druckgeräten und -strukturen im Betrieb - Allgemeine Grundsätze

Dieses Dokument beschreibt die Überwachung der Schallemission (AE) für die Erkennung, Lokalisierung und Einstufung von AE-Quellen im Einsatz bei der Anwendung auf metallische Druckgeräte und andere Konstruktionen, wie Brücken, Brückenseile, Krane, Speicherbehälter, Rohrleitungen, Windkrafttürme, Marineanwendungen, Offshore-Bauwerke usw. Die Überwachung kann periodisch, temporär oder konti-nuierlich, vor Ort oder ferngesteuert, überwacht oder automatisiert erfolgen. Ziel der AE-Überwachung ist es, Regionen zu definieren, die aufgrund von Schäden oder Defektentwicklungen akustisch aktiv sind.

Essais non destructifs - Contrôle par émission acoustique - Surveillance en service par émission acoustique des équipements et structures métalliques sous pression - Exigences générales

Le présent document spécifie les exigences générales relatives à la surveillance en service par émission acoustique (EA). Il porte sur la détection, la localisation et le classement des sources d’EA, avec une application aux équipements sous pression et autres structures métalliques tels que ponts, câbles de pont, grues, réservoirs de stockage, pipelines, mâts d’éoliennes, applications maritimes, structures offshore. La surveillance peut être périodique, temporaire ou continue, sur site ou à distance, supervisée ou automatisée. Les objectifs de la surveillance par EA sont de définir les zones qui sont acoustiquement actives à la suite de l’évolution d’un dommage ou d’un défaut.

Neporušitvene preiskave - Akustična emisija - Nadzorovanje akustične emisije pri uporabi kovinske tlačne opreme in drugih kovinskih struktur - Splošne zahteve

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Jul-2019
• ICS: 19.100 - Non-destructive testing
• Technical Committee: PKG - Testing of metallic materials
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 16-Dec-2020
• Due Date: 03-Feb-2021
• Completion Date: 13-Jan-2021
• Ref Project: EN 17391:2021 - Non-destructive testing - Acoustic emission testing - In-service acoustic emission monitoring of metallic pressure equipment and structures - General requirements

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 17391:2019
01-julij-2019
Neporušitvene preiskave - Akustična emisija - Nadzorovanje akustične emisije pri
uporabi kovinske tlačne opreme in drugih kovinskih struktur - Splošne zahteve

Non-destructive testing - Acoustic emission testing – In-service acoustic emission

monitoring of metallic pressure equipment and structures - General requirements

Zerstörungsfreie Prüfung - Schallemissionsprüfung - Überwachung der Schallemission

von metallischen Druckgeräten und -strukturen im Betrieb - Allgemeine Grundsätze
Ta slovenski standard je istoveten z: prEN 17391
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
oSIST prEN 17391:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 17391:2019
DRAFT
EUROPEAN STANDARD
prEN 17391
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2019
ICS 19.100
English Version
Non-destructive testing - Acoustic emission testing - In-
service acoustic emission monitoring of metallic pressure
equipment and structures - General requirements
Zerstörungsfreie Prüfung - Schallemissionsprüfung -
Überwachung der Schallemission von metallischen
Druckgeräten und -strukturen im Betrieb - Allgemeine
Grundsätze

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 138.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17391:2019 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Personnel qualification ................................................................................................................................. 7

5 Preliminary information .............................................................................................................................. 7

5.1 Structural information .................................................................................................................................. 7

5.2 Operating conditions ..................................................................................................................................... 7

5.3 AE event mechanisms .................................................................................................................................... 8

5.3.1 General ................................................................................................................................................................ 8

5.3.2 Crack growth ..................................................................................................................................................... 8

5.3.3 Corrosion ............................................................................................................................................................ 9

5.3.4 Friction, fretting and cavitation erosion ................................................................................................. 9

6 Monitoring methodology .............................................................................................................................. 9

6.1 Periodic, temporary or continuous monitoring ................................................................................... 9

6.2 On-site or remote-controlled monitoring ........................................................................................... 10

6.3 Supervised or automated monitoring .................................................................................................. 11

7 Monitoring instrumentation .................................................................................................................... 11

7.1 General requirement .................................................................................................................................. 11

7.2 Sensors and Preamplifiers ........................................................................................................................ 11

7.2.1 General ............................................................................................................................................................. 11

7.2.2 Typical frequency ranges (band width) ............................................................................................... 12

7.2.3 Coupling agent ............................................................................................................................................... 12

7.2.4 Mounting method ......................................................................................................................................... 12

7.2.5 Temperature range, wave guide usage ................................................................................................ 13

7.2.6 Use in explosive atmosphere ................................................................................................................... 13

7.2.7 Immersed sensors ........................................................................................................................................ 13

7.2.8 Integral electronics (amplifier, band pass filter, RMS converter, ASL converter) ................ 13

7.2.9 Grounding requirements ........................................................................................................................... 13

7.2.10 External preamplifiers ............................................................................................................................... 13

7.2.11 Sensor and preamplifier cables .............................................................................................................. 14

7.3 Portable AE equipment .............................................................................................................................. 14

7.4 Single- and multi-channel AE equipment ............................................................................................ 14

7.5 Measured parameters ................................................................................................................................ 14

7.5.1 Burst signal parameters ............................................................................................................................ 14

7.5.2 Continuous signal parameters ................................................................................................................ 14

7.6 Verification of sensor sensitivity and coupling quality .................................................................. 15

7.7 External parameters ................................................................................................................................... 15

7.8 AE system ........................................................................................................................................................ 15

7.9 Monitoring in hazardous areas ............................................................................................................... 16

8 Pre-Monitoring measurements ............................................................................................................... 16

8.1 Wave propagation behaviour .................................................................................................................. 16

8.1.1 General ............................................................................................................................................................. 16

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8.1.2 Liquid or gas containment ......................................................................................................................... 16

8.1.3 Thickness of the wall (material) ............................................................................................................. 17

8.1.4 Geometry of the structure ......................................................................................................................... 17

8.1.5 Insulation ......................................................................................................................................................... 17

8.1.6 Surface preparation ..................................................................................................................................... 17

8.2 Background noise measurements .......................................................................................................... 17

8.2.1 Representative location ............................................................................................................................. 17

8.2.2 Process noise .................................................................................................................................................. 17

8.2.3 Other disturbance noise ............................................................................................................................. 18

8.2.4 Noise sampling period ................................................................................................................................ 18

8.3 Sensitivity of AE monitoring using linear or planar location ....................................................... 18

9 Monitoring procedure ................................................................................................................................. 18

9.1 Sensor positioning ........................................................................................................................................ 18

9.2 External parameters .................................................................................................................................... 19

9.3 Instrumentation verification and performance ................................................................................ 19

9.4 Data acquisition and online filtering ..................................................................................................... 19

10 Data analysis .................................................................................................................................................. 19

10.1 General ............................................................................................................................................................. 19

10.2 Online analysis .............................................................................................................................................. 20

10.3 Data processing ............................................................................................................................................. 20

10.3.1 Background noise analysis ........................................................................................................................ 20

10.3.2 Pre-location data analysis ......................................................................................................................... 20

10.3.3 AE event location .......................................................................................................................................... 21

10.3.4 Cluster analysis ............................................................................................................................................. 21

10.3.5 Pattern recognition ...................................................................................................................................... 21

11 AE source interpretation and evaluation ............................................................................................. 22

11.1 Interpretation of AE results ...................................................................................................................... 22

11.2 Source evaluation criteria ......................................................................................................................... 22

11.3 Grading and severity of AE sources ........................................................................................................ 25

11.4 Verification of AE sources and follow-up NDT ................................................................................... 25

12 Documentation and reporting ................................................................................................................. 26

Annex A (informative) Fatigue crack growth and associated acoustic emission applied to

monitoring of marine structures ............................................................................................................ 27

A.1 Definitions ....................................................................................................................................................... 27

A.1.1 General ............................................................................................................................................................. 27

A.1.2 Acoustic emission power ........................................................................................................................... 27

A.1.3 Acoustic emission energy .......................................................................................................................... 27

A.1.4 Acoustic emission intensity ...................................................................................................................... 27

A.2 AE power and resulting waves from a micro-fracture event (AE source) ................................ 27

A.3 AE detectability ............................................................................................................................................. 29

A.4 Fatigue crack growth ................................................................................................................................... 30

A.5 Critical crack depth ...................................................................................................................................... 31

A.6 Crack growth rate and required duration of monitoring............................................................... 32

A.7 AE fatigue monitoring of ship hull structure ...................................................................................... 35

Bibliography ................................................................................................................................................................. 37

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European foreword

This document (prEN 17391:2019) has been prepared by Technical Committee CEN/TC 138 “Non-

destructive testing”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
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Introduction

Acoustic emission testing (AT) is well established for the detection of discontinuities in metallic

structures. Furthermore, AT is widely accepted and applied during hydraulic or pneumatic test. In

service acoustic emission (AE) monitoring can provide global surveillance of structural details for early

detection of active cracks and damage evolution. It allows through life damage assessment guiding

subsequent non-destructive testing (NDT) for damage verification and damage sizing purposes.

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1 Scope

This document describes acoustic emission (AE) monitoring for in-service detection, location and

grading of AE sources with application to metallic pressure equipment and other structures such as

bridges, bridge ropes, cranes, storage tanks, pipelines, wind turbine towers, marine applications,

offshore structures etc. The monitoring can be periodic, temporary or continuous, on site or remote-

controlled, supervised or automated. The objectives of AE monitoring are to define regions which are

acoustically active as a result of damage or defect evolution.
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.

EN 1330-1:2015, Non-destructive testing - Terminology - Part 1: List of general terms

EN 1330-2:1998, Non destructive testing - Terminology - Part 2: Terms common to the non-destructive

testing methods

EN 1330-9:2017, Non-destructive testing - Terminology - Part 9: Terms used in acoustic emission testing

EN 13477-1:2001, Non-destructive testing - Acoustic emission - Equipment characterisation - Part 1:

Equipment description

EN 13477-2:2013, Non-destructive testing - Acoustic emission - Equipment characterisation - Part 2:

Verification of operating characteristics

EN 13554:2011, Non-destructive testing - Acoustic emission testing - General principles

EN 14584:2013, Non-destructive testing - Acoustic emission testing - Examination of metallic pressure

equipment during proof testing - Planar location of AE sources

EN 15495:2007, Non Destructive testing - Acoustic emission - Examination of metallic pressure equipment

during proof testing - Zone location of AE sources

EN ISO/IEC 17025:2017, Non-destructive testing - General requirements for the competence of testing

and calibration laboratories
EN 60529:2014, Degrees of protection provided by enclosures (IP Code)
3 Terms and definitions

For the purpose of this document, the terms and definitions given in EN 1330-1:2015, EN 1330-2:1998

and EN 1330-9:2017 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
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4 Personnel qualification

It is assumed that acoustic emission monitoring is performed by qualified and capable personnel. In

order to prove this qualification, it is recommended to certify the personnel in accordance with

EN ISO 9712:2013.
5 Preliminary information
5.1 Structural information

The monitoring of the structure depends on the historical operational data. The knowledge of the

operating conditions (e.g. maximum load level, cycling, environmental conditions) and possible repairs

are key factors for the determination of the monitoring strategy.

The accessibility of the structure shall be considered when the monitoring task is planned, designed and

performed.

The type and size of the structure (as well as other factors below) shall determine if the monitoring can

be global or local. If damage is expected in some specific areas of the structure, the sensor configuration

shall focus on these areas to monitor for possible damage evolution. In this case the monitoring may be

restricted to:
— a known damage mechanism at a specific location from experience; or

— highly stressed areas (hot spots) of known or predicted susceptibility to failure (e.g. finite element

analysis).
5.2 Operating conditions

In the case of a potentially explosive environment, the instrumentation used and its installation should

conform to Directive 2014/34/EU (ATEX) [1]. In particular sensors and preamplifiers shall be ATEX

certified.

For structures operating above or below a certain temperature level (e.g. above +80 °C or below

−40 °C), specific high/low temperature instrumentation shall be used. Appropriate attention shall be

given to the sensor coupling agent (see Subclause 7.2.3).

A high operating temperature, either by itself or in combination with the load, may influence the

damage mechanisms in the structure (e.g. high-temperature corrosion requires a high temperature

environment).

In case of low temperature operating conditions, attention shall be paid to the fracture toughness

(ductile-to-brittle transition) of the structure material. If the structure is insulated, as in many cases, the

formation of frost in the insulation windows should be avoided so that cracking of the frozen product

does not disturb AE monitoring.

Where the structure is located outside (in the open air), natural phenomena like wind, rain or hail can

disturb the AE monitoring. Such phenomena shall be taken into account during the preparation of the

monitoring methodology. If the structure cannot be protected from the environment, these natural

phenomena shall be measured as well as recorded and the data of the associated parametric inputs

correlated with the AE data.
In case of aggressive and/or corrosive environment such as:
— marine or offshore structures (e.g. saline mist, waves, storms…);
— chemical plant structures (e.g. acid); or
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— nuclear plants (e.g. radiation);

special care shall be taken for the protection of all the exposed AE instrumentation, sensors and

preamplifiers. The acquisition system shall be located as far as possible away from the above risks.

In case of high or low temperature operating structure, preliminary measurements shall be performed

in conditions as close as possible to real operating conditions.

The influence of the process noise on the sensitivity of the monitoring shall be identified before starting

the monitoring itself.
All information on the various phases of the process shall be provided by the

customer/owner/operator. The severest process periods shall be taken into account to determine if the

monitoring is possible continuously or periodically.
5.3 AE event mechanisms
5.3.1 General

In technical application, detectability of early stages of structural degradation or damage due to e.g.

fatigue and stress corrosion, is supported by material embrittlement (low temperature, hydrogen or

radiation induced embrittlement, hardened heat effected zone of weld, etc.). Detectability can be

enhanced by major induced AE events in the material volume from secondary effects or processes.

Secondary effects are often of greater importance for early detectability compared to stable crack

growth.

Simultaneously occurring secondary effects or processes can create intense sources of high AE activity

and/or higher burst signal maximum amplitudes from overlapping of many single low energy events

e.g.:

— dislocation avalanche processes within an extended plastic zone at the tip of large cracks;

— fretting of (non-corroded or corroded) crack faces or stress transfer induced local interfacial

friction during opening/closure actions of fatigue cracks without any crack growth itself;

— AE emitting processes due to material morphology caused by local stress fields around/ahead of

crack tips, e.g. breakage of hard inclusions or high melting impurity phases in the ferrite grain or of

grain boundary precipitations;

— breakage of corrosion products (e.g. rust particles) internally or on corroded crack faces etc.

5.3.2 Crack growth

Fatigue is the most common cause of mechanical failure of e.g. machinery and structures subjected to

cyclic loading. Stress corrosion cracking (SCC) is one of the common causes for failure in e.g. chemical

reactors and fluid transmission lines.

AE is sensitive to the brittle microscopic fracture events accompanying stable fatigue crack propagation

and corrosion related fracture events. The relationship between the acoustic emission from stable crack

growth in metals and the associated damage mechanisms, whether fatigue or stress corrosion cracking,

requires greater understanding of the physics of plastic deformation and fracture on the crystal

microstructure scale.

Annex A gives expressions for the key deformation and fracture parameters associated with acoustic

emission from stable fatigue crack growth. The driving force behind crack growth is the stress

concentration at the crack tip. Unless the crack is continually supplied with strain energy it will cease to

propagate.
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Other stable crack growth mechanisms giving rise to acoustic emission include hydrogen cracking and

thermally induced cracks. AE monitoring may be used also for detection of hydrogen blistering,

delamination, creep and aging (material degradation).
5.3.3 Corrosion

The mechanisms of corrosion are different to stable crack growth. General corrosion is usually a surface

oxidation over a large area. The AE activity and intensity depends on the severity of the ongoing

corrosion process.

Furthermore, stress due to pressure or temperature cycling usually leads to cracking and de-bonding of

the brittle oxide layer resulting in high AE activity over the corroded area.

Other localized corrosion processes may lead to damage with local stress concentration and subsequent

crack initiation (e.g. at the area of pin holes or pitting).
5.3.4 Friction, fretting and cavitation erosion
These damage mechanisms are particularly intense sources of acoustic emission.

Cavitation in a liquid leads to the implosion of bubbles that generates strong intensity (up to 1000 MPa)

and short duration (approximately µs) pressure waves. Notably AE from cavitation results in discrete

events, whose acoustic energy is at least an order of magnitude higher than those events generated by

turbulence phenomenon.

Fretting and friction phenomena generate AE of high energy and these mechanisms can be produced

within a crack during loading and unloading of the structure.
6 Monitoring methodology
6.1 Periodic, temporary or continuous monitoring

The integrity or health of a structure can be investigated by AE monitoring at any time of its working

life (i.e. in-service under normal operating loads, start up and shutdowns, etc.) provided that possible

variations of operating conditions do not come into conflict with the technical specifications of the AE

instrumentation or the measurement setup during data acquisition.

Large-scale and/or complex structures, e.g. ship hulls, offshore platforms or bridges permit AE

monitoring only for areas identified as highly stressed and fatigue and/or corrosion sensitive.

Different in-service AE monitoring methodologies can be adapted depending on the objective of the

measurement, e.g.:

— temporary (short or medium term), if the monitoring is performed for a single short (hours/days)

or medium (weeks/month) time interval;

— periodic, if the monitoring is done repeatedly on the same structure for specific time periods not

necessarily based on the same time interval;

— continuous, if the monitoring is conducted permanently on the same structure for a long duration

(months or years).

The methodology and the time period of AE monitoring are selected taking into account:

— type of known or expected d
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