Gas cylinders - Refillable seamless steel gas cylinders and tubes - Acoustic emission examination (AT) and follow-up ultrasonic examination (UT) for periodic inspection and testing (ISO 16148:2016)

ISO 16148:2016 gives procedures for the use of acoustic emission examination (AT) and ultrasonic examination (UT) follow-up during the periodic inspection and testing of seamless steel cylinders and tubes with a water capacity of up to 3 000 l used for compressed and liquefied gases. This examination provides acoustic emission (AE) indications and locations that are evaluated by a secondary examination using UT for a possible flaw in the cylinder or tube. Methods other than UT for the secondary examination are not covered by this International Standard.
ISO 16148:2016 does not cover composite cylinders.
CAUTION ? Some of the tests specified in this International Standard involve the use of processes which could lead to a hazardous situation.

Gasflaschen - Wiederbefüllbare nahtlose Gasflaschen und Großflaschen aus Stahl - Schallemissionsprüfung und nachfolgende Ultraschallprüfung für die wiederkehrende Inspektion und Prüfung (ISO 16148:2016)

Diese Internationale Norm gibt Verfahren für die Anwendung der Schallemissionsprüfung (AT) und der nachfolgenden Ultraschallprüfung (UT) während der wiederkehrenden Inspektion und Prüfung von nahtlosen Flaschen und Großflaschen aus Stahl mit einem Fassungsraum bis zu 3 000 l für verdichtete und verflüssigte Gase an. Diese Prüfung ergibt AE-Befunde (AE) und -Ortungen, die durch eine weitere auf Ultraschallprüfung basierende Untersuchung auf eine mögliche Kerbe in der Flasche oder Großflasche bewertet werden. Neben der Ultraschallprüfung könnten andere Verfahren als weitere Prüfung angewendet werden, welche jedoch nicht in den Anwendungsbereich dieser Internationalen Norm fallen.
Diese Internationale Norm gilt nicht für Verbundflaschen.
VORSICHT — Einige der in dieser Norm beschriebenen Prüfungen beinhalten die Anwendung von Verfahren, die zu einer Gefährdungssituation führen können.

Bouteilles à gaz - Bouteilles à gaz rechargeables en acier sans soudure et tubes - Essais d'émission acoustique et examen ultrasonique complémentaire pour l'inspection périodique et l'essai (ISO 16148:2016)

ISO 16148:2016 décrit des modes opératoires de l'essai d'émission acoustique (EA) suivi du contrôle par ultrasons (UT) lors du contrôle et des essais périodiques des bouteilles et tubes en acier sans soudure, d'une capacité en eau allant jusqu'à 3 000 l, utilisés pour les gaz comprimés et liquéfiés. Cet examen par émission acoustique (EA) fournit des indications et des localisations qui sont évaluées par un deuxième examen utilisant les ultrasons (UT) pour déterminer un éventuel défaut dans la bouteille ou le tube. Pour ce deuxième examen, les méthodes autres que le contrôle UT ne sont pas couvertes par l'ISO 16148:2015.
ISO 16148:2016 ne couvre pas les bouteilles composites.

Plinske jeklenke - Ponovno polnljive plinske jeklenke in velike jeklenke iz celega - Preskus z akustično emisijo in ultrazvočni preskus pri periodičnem pregledu in preskušanju (ISO 16148:2016)

Ta mednarodni standard določa postopke za uporabo preskusa z akustično emisijo (AT) in ultrazvočnega preskusa (UT) med rednim pregledom in preskušanjem jeklenk in velikih jeklenk iz celega jekla z vodno prostornino do 3000 l za stisnjene in utekočinjene pline.
S tem preskusom se zagotovijo vrednosti in lokacije akustičnih emisij, ki so ovrednotene s
sekundarnim ultrazvočnim preskusom za ugotavljanje morebitne napake v jeklenki ali veliki jeklenki. Druge metode sekundarnega preskusa v tem mednarodnem standardu niso zajete.
Ta mednarodni standard ne zajema kompozitnih jeklenk.
POZOR – Nekateri preskusi, podani v tem mednarodnem standardu, vključujejo uporabo postopkov, ki lahko vodijo v nevarno stanje.

General Information

Status
Published
Publication Date
26-Apr-2016
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
27-Apr-2016
Completion Date
27-Apr-2016

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SLOVENSKI STANDARD
SIST EN ISO 16148:2016
01-junij-2016
1DGRPHãþD
SIST EN ISO 16148:2006

3OLQVNHMHNOHQNH3RQRYQRSROQOMLYHSOLQVNHMHNOHQNHLQYHOLNHMHNOHQNHL]FHOHJD

3UHVNXV]DNXVWLþQRHPLVLMRLQXOWUD]YRþQLSUHVNXVSULSHULRGLþQHPSUHJOHGXLQ
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Gas cylinders - Refillable seamless steel gas cylinders and tubes - Acoustic emission

examination (AT) and follow-up ultrasonic examination (UT) for periodic inspection and

testing (ISO 16148:2016)
Gasflaschen - Wiederbefüllbare nahtlose Gasflaschen und Großflaschen aus Stahl -

Schallemissionsprüfung und nachfolgende Ultraschallprüfung für die wiederkehrende

Inspektion und Prüfung (ISO 16148:2016)

Bouteilles à gaz - Bouteilles à gaz rechargeables en acier sans soudure et tubes - Essais

d'émission acoustique et examen ultrasonique complémentaire pour l'inspection
périodique et l'essai (ISO 16148:2016)
Ta slovenski standard je istoveten z: EN ISO 16148:2016
ICS:
23.020.35 Plinske jeklenke Gas cylinders
SIST EN ISO 16148:2016 de

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

---------------------- Page: 1 ----------------------
SIST EN ISO 16148:2016
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SIST EN ISO 16148:2016
EN ISO 16148
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2016
EUROPÄISCHE NORM
ICS 23.020.30 Supersedes EN ISO 16148:2006
English Version
Gas cylinders - Refillable seamless steel gas cylinders and
tubes - Acoustic emission examination (AT) and follow-up
ultrasonic examination (UT) for periodic inspection and
testing (ISO 16148:2016)

Bouteilles à gaz - Bouteilles à gaz rechargeables en Gasflaschen - Wiederbefüllbare nahtlose Gasflaschen

acier sans soudure et tubes - Essais d'émission und Großflaschen aus Stahl - Schallemissionsprüfung

acoustique et examen ultrasonique complémentaire und nachfolgende Ultraschallprüfung für die

pour l'inspection périodique et l'essai (ISO wiederkehrende Inspektion und Prüfung (ISO

16148:2016) 16148:2016)
This European Standard was approved by CEN on 28 November 2015.

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. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16148:2016 E

worldwide for CEN national Members.
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SIST EN ISO 16148:2016
EN ISO 16148:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 16148:2016
EN ISO 16148:2016 (E)
European foreword

This document (EN ISO 16148:2016) has been prepared by Technical Committee ISO/TC 58 “Gas

cylinders” in collaboration with Technical Committee CEN/TC 23 “Transportable gas cylinders” the

secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by October 2016, and conflicting national standards shall

be withdrawn at the latest by October 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN ISO 16148:2006.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: 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, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 16148:2016 has been approved by CEN as EN ISO 16148:2016 without any modification.

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SIST EN ISO 16148:2016
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SIST EN ISO 16148:2016
INTERNATIONAL ISO
STANDARD 16148
Second edition
2016-04-15
Gas cylinders — Refillable seamless
steel gas cylinders and tubes —
Acoustic emission examination (AT)
and follow-up ultrasonic examination
(UT) for periodic inspection and testing
Bouteilles à gaz — Bouteilles à gaz rechargeables en acier sans
soudure et tubes — Essais d’émission acoustique et examen
ultrasonique complémentaire pour l’inspection périodique et l’essai
Reference number
ISO 16148:2016(E)
ISO 2016
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Operational principles ................................................................................................................................................................................... 3

5 Personnel qualification ................................................................................................................................................................................. 3

6 Special considerations to ensure valid tests ............................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Acoustic emission examination methods ......................................................................................................................... 4

6.3 Pressurization .......................................................................................................................................................................................... 4

6.4 Safety precautions ................................................................................................................................................................................ 5

7 Acoustic emission examination equipment ............................................................................................................................. 5

8 Acoustic emission examination calibration and equipment verification .................................................7

8.1 Calibration .................................................................................................................................................................................................. 7

8.2 Equipment verification .................................................................................................................................................................... 7

9 Overall procedure................................................................................................................................................................................................ 7

10 Real-time evaluation criteria................................................................................................................................................................... 8

11 AT test report ........................................................................................................................................................................................................... 9

12 Follow-up ultrasonic examination ..................................................................................................................................................10

Annex A (normative) Ultrasonic examination (UT) follow-up to acoustic emission

examination (AT) ..............................................................................................................................................................................................11

Annex B (normative) AT equipment specifications ...........................................................................................................................17

Annex C (normative) Example instrument settings, examination methods and rejection

criteria for MAE...................................................................................................................................................................................................19

Annex D (informative) Alternative method for source location ...........................................................................................22

Annex E (informative) Distance amplitude correction procedures ..................................................................................24

Bibliography .............................................................................................................................................................................................................................27

© ISO 2016 – All rights reserved iii
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
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

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

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 documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 58, Gas cylinders, Subcommittee SC 4,

Operational requirements for gas cylinders.

This second edition cancels and replaces the first edition (ISO 16148:2006), which has been technically

revised. The changes include

a) expansion of the scope to include tubes of water capacity up to 3 000 l used for compressed and

liquefied gases, and

b) addition of procedures for ultrasonic examination (UT) follow-up during periodic inspection, as

described in the new Annex A.
iv © ISO 2016 – All rights reserved
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
Introduction

In recent years, new non-destructive examination (NDE) techniques have been successfully introduced

as an alternative to the conventional testing procedures of gas cylinders, tubes and other cylinders at

the time of periodic inspection and testing.

One of the alternative NDE methods for certain applications is acoustic emission examination (AT),

which has proved to be an acceptable test method applied during periodic inspection and testing in

some countries.

The test method requires pressurization to a level greater than the normal filling pressure.

The pressurization medium can be either gas or liquid.

Acoustic emission (AE) measurements are used to detect and locate emission sources. Other NDE

methods are needed to evaluate the significance of AE detected sources. One of the alternative NDE

methods used as a follow-up to AT is ultrasonic examination (UT), which has proved to be an acceptable

testing method applied during periodic inspection and testing. The purpose of this International

Standard is to provide a procedure for locating, detecting and evaluating the relevance of AE indications

such as those from longitudinally oriented crack-like discontinuities. The shear wave (angle beam) UT

method is intended to be used immediately following AT to evaluate the significance of AE indications.

This International Standard describes two methods of AT, defined as Method A and Method B, and a

method of follow-up UT.

With the agreement of the testing and certifying body approved by the competent authority of the

country of approval, the hydraulic pressure test of cylinders and tubes can be replaced by an equivalent

AT/UT Method A or B.

This International Standard is intended to be used under a variety of national regulatory regimes, but has

[1]

been written so that it is suitable for the application of Reference. Attention is drawn to requirements

in the specified relevant national regulations of the country (countries) where the cylinders are

intended to be used that might override the requirements given in this International Standard. Where

there is any conflict between this International Standard and any applicable regulation, the regulation

always takes precedence.
© ISO 2016 – All rights reserved v
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SIST EN ISO 16148:2016
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SIST EN ISO 16148:2016
INTERNATIONAL STANDARD ISO 16148:2016(E)
Gas cylinders — Refillable seamless steel gas cylinders and
tubes — Acoustic emission examination (AT) and follow-
up ultrasonic examination (UT) for periodic inspection
and testing
1 Scope

This International Standard gives procedures for the use of acoustic emission examination (AT) and

ultrasonic examination (UT) follow-up during the periodic inspection and testing of seamless steel

cylinders and tubes with a water capacity of up to 3 000 l used for compressed and liquefied gases.

This examination provides acoustic emission (AE) indications and locations that are evaluated by a

secondary examination using UT for a possible flaw in the cylinder or tube. Methods other than UT for

the secondary examination are not covered by this International Standard.
This International Standard does not cover composite cylinders.

CAUTION — Some of the tests specified in this International Standard involve the use of

processes which could lead to a hazardous situation.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for is application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 5577, Non-destructive testing — Ultrasonic inspection — Vocabulary

ISO 6406, Gas cylinders — Seamless steel gas cylinders — Periodic inspection and testing

ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel

ISO 12716, Non-destructive testing — Acoustic emission inspection — Vocabulary

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

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

ASTM E1419, Standard Practice for Examination of Seamless, Gas-Filled, Pressure Vessels using Acoustic

Emission

ASNT SNT-TC-1A, Recommended Practice for Personnel Qualification and Certification in

Nondestructive Testing
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 5577, ISO 12716 and the

following apply.
© ISO 2016 – All rights reserved 1
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
3.1
critical flaw

imperfection or damage that is large enough to exhibit unstable crack growth under certain service

conditions
3.2
working pressure

settled pressure of a compressed gas at a uniform reference temperature of 15 °C in a full gas cylinder

Note 1 to entry: In North America service pressure is often used to indicate a similar condition, usually at 21,1 °C

(70 °F).

Note 2 to entry: In East Asia, service pressure is often used to indicate a similar condition, usually at 35 °C.

[SOURCE: ISO 10286:2015, definition 736]
3.3
normal filling pressure
level to which a cylinder or tube is pressurized during filling

Note 1 to entry: This is usually greater than the marked working pressure due to the heat of compression.

3.4
acoustic emission test pressure
AT pressure
maximum pressure at which acoustic emission testing is performed
3.5
acoustic emission pressure test range
range of pressure during which acoustic emission is monitored
3.6
Method A

acoustic emission testing performed using pneumatic pressurization to at least 110 % of the normal

filling pressure

Note 1 to entry: Normally performed on an assembly of cylinders (e.g. bundle) or tubes (e.g. tube trailer).

3.7
Method B

acoustic emission testing performed during the hydrostatic proof pressurization to the re-test pressure

on each cylinder or tube
3.8
secondary AE sources
emissions not generated by actual crack propagation and plastic deformation

Note 1 to entry: Contact between the surfaces of a discontinuity as the cylinder expands, fracture or rubbing of

mill scale within a discontinuity as the cylinder expands are examples of secondary AE sources.

3.9
calibration ring

section cut from similar cylinder material used for the calibration of the follow-up UT

3.10
distance amplitude correction curve
DAC curve

curve generated during the standardization process that accounts for the loss of amplitude of the

returning signal as a result of signal travel distance
2 © ISO 2016 – All rights reserved
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
3.11
shear wave ultrasonic search unit

block of material that conforms to the curvature of the surface of the test object and orients the

ultrasonic transducer at an angle which transmits and receives shear waves
3.12
ultrasonic couplant

fluid medium that forms a thin, bubble-free layer between the search unit and the test object

3.13
skip distance

in angle beam (shear wave) examination, distance along the test surface from the sound entry point to

the point at which the sound returns to the same surface

Note 1 to entry: It can be considered the top surface distance of a complete wave path of sound in the test material.

3.14
modal acoustic emission
MAE

branch of AE (acoustic emission) focused on the detection and analysis of the actual sound waves

produced at fracture sites from crack growths or surface rubbing
4 Operational principles

When cylinders or tubes containing discontinuities are pressurized, sound waves (AE) can be produced

by several different sources (e.g. secondary sources or actual propagation of cracks). These sources can

produce AE indications at pressures less than, equal to or greater than working pressure. The sound

waves travel throughout the structure.

Piezoelectric sensors mounted on a cylinder or tube surface respond to sound waves. They are

connected to a signal processor, which records the signal parameters associated with the passage of

the waves under the sensor. Sound waves travel at assumed constant speeds. With at least two sensors,

one mounted at each end of a cylinder or tube, the approximate location of event sources is derived

from the measured arrival time of sound waves at the sensors.

If measured emissions exceed the specified levels over a linear distance on the cylinder, then

such locations shall undergo a secondary inspection (e.g. by UT) in order to verify the presence of

discontinuities and to measure their dimensions. From this secondary inspection, if the depth of the

discontinuity exceeds the specified limit (that is, a limit based on a number of factors, i.e. cylinder

material, wall thickness, fatigue crack growth rate estimates, fracture critical size calculations and any

practical experience), then the cylinder shall be removed from service.

If, after the examination, a recalibration of the AT equipment proves negative, the relevant cylinder

shall be re-examined by a non-destructive examination (NDE) method other than AT Method A.

5 Personnel qualification

The AT and UT equipment shall be operated, and its operation supervised, by competent personnel who

meet the requirements of ISO 9712 or an equivalent standard (e.g., ASNT SNT TC 1A) as authorized by

the Level III operator. The operator shall meet the requirements for Level I and shall be supervised by a

Level II person. The testing organization shall retain a Level III operator (company employee or a third

party) to oversee the entire AT and UT programme.
© ISO 2016 – All rights reserved 3
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SIST EN ISO 16148:2016
ISO 16148:2016(E)
6 Special considerations to ensure valid tests
6.1 General

In order to prevent invalid AT when using Method A and to overcome the Kaiser effect, the AT pressure

shall exceed that pressure previously exerted on the cylinder or tube during service, i.e. normal filling

pressure for compressed gases, and the developed pressure at the maximum service temperature (e.g.

65 °C) for liquefied gases.

NOTE 1 The Kaiser effect is characterized by the absence of AE until the previous maximum applied load level

has been exceeded.

If the pressure of the cylinder or tube exceeds 110 % of its normal filling pressure, e.g. exposure to high

ambient temperatures, it shall be recorded [see NOTE to Clause 11 d)].

After pressurization to more than the AT pressure, Method A shall not be performed within a time

period of less than one year or before a sufficient number of pressurization cycles have occurred, since

such practice can decrease the sensitivity of the examination.

NOTE 2 The number of pressurization cycles is related to the design parameters, particularly the material

composition, of the cylinder or tube undergoing periodic inspection and testing. This number of pressurization

cycles at the working pressure of the cylinder or tube is typically between 75 and 100.

If a pressure greater than the normal filling pressure has been applied and a time period equal to or

greater than one year or a sufficient number of pressurization cycles has not elapsed, then the AT shall

be 10 % above this excessive pressure, but shall not exceed the design test pressure (TP) of the cylinder

or tube. If at any stage a receptacle for liquefied gases has been overfilled, this shall be reported to the

re-tester by the cylinder or tube owner or operator. If the AT would result in a pressure greater than

TP, then Method A shall not be applied. Only Method B or a hydrostatic proof pressure test shall be

performed.

WARNING — Take appropriate measures to ensure safe operation and to contain any energy

that could be released during pressure testing. It should be noted that pneumatic pressure tests

require more precautions than hydrostatic proof pressure tests since, regardless of the size

of the container, any error in carrying out this test is highly likely to lead to a rupture under

gas pressure. Therefore, these tests should be carried out only after ensuring that the safety

measures satisfy the safety requirements.
6.2 Acoustic emission examination methods

One of the two AT methods (A or B) may be used during periodic inspection and testing of seamless

steel cylinders in accordance with this International Standard. In both methods, UT follow-up of the AE

indications shall be in accordance with the applicable test method described in Annex A.

Once a method (A or B) has been selected, its result shall be final.
6.3 Pressurization

General practice in the gas industry is to use low pressurization rates. This practice promotes safety

and reduces equipment investment. AT should be performed with pressurization rates low enough to

allow cylinder deformation to be in equilibrium with the applied load. Pressurization should proceed at

rates that do not produce noise from the pressurizing medium. For Method A, typical current practice is

to use pressurization rates that approximate 35 bar/h (3,5 MPa/h) for tubes.

NOTE For smaller cylinders a higher pressurization rate can be suitable provided it is demonstrated that

all detrimental defects can be detected and the pressurization rate is slow enough to allow the pressurization

to be stopped before bursting of the cylinder. Pressure holds are not necessary; however, they can be useful for

reasons other than measurement of AE.
2 5 2
1) 1 bar = 0,1 MPa = 0,1 N/mm = 10 N/m .
4 © ISO 2016 – All rights reserved
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SIST EN ISO 16148:2016
ISO 16148:2016(E)

Secondary AE sources can produce emissions throughout pressurization. Crack growth normally

produces emissions at pressures higher than the normal filling pressure.

When pressure within a vessel is low and gas is the pressurizing medium, flow velocities are relatively

high. Flowing gas (turbulence) can produce measurable emissions. Considering this, acquisition of AE

data shall commence at some pressure greater than the starting pressure (for example, one-half of the

AT pressure).

Secondary sources in serious flaws can produce more AE than flaw growth. When cylinders are

pressurized, flaws can produce emissions at pressures less than normal filling pressure. An AT

pressure that is at least 10 % greater than normal filling pressure allows measurement of emissions

from secondary sources in flaws and from flaw growth.

Excess background noise can distort AE data or render them useless. Users shall be aware of the

following common sources of background noise:
— high gas fi
...

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