SIST EN ISO 20485:2018
(Main)Non-destructive testing - Leak testing - Tracer gas method (ISO 20485:2017)
Non-destructive testing - Leak testing - Tracer gas method (ISO 20485:2017)
This standard describes the techniques to be applied for the detection of a leak, using a tracer gas and a tracer gas specific leak detector
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Prüfgasverfahren (ISO 20485:2017)
Dieses Dokument beschreibt die anzuwendenden Verfahren zur Erkennung eines Lecks durch ein Prüfgas und einen prüfgasspezifischen Leckdetektor
Essais non destructifs - Contrôle d'étanchéité - Méthode par gaz traceur (ISO 20485:2017)
ISO 20485:2017 décrit les techniques à appliquer pour la détection d'une fuite à l'aide d'un gaz traceur et d'un détecteur de fuites spécifique au gaz traceur utilisé.
Neporušitveno preskušanje - Preiskava tesnosti - Metoda slednega plina (ISO 20485:2017)
Ta standard opisuje tehnike za zaznavanje uhajanja z uporabo indikatorskega plina in detektorja uhajanja, namenjenega za uporabo z indikatorskim plinom.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 20485:2018
01-julij-2018
1DGRPHãþD
SIST EN 13185:2002
SIST EN 13185:2002/A1:2004
Neporušitveno preskušanje - Preiskava tesnosti - Metoda slednega plina (ISO
20485:2017)
Non-destructive testing - Leak testing - Tracer gas method (ISO 20485:2017)
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Prüfgasverfahren (ISO 20485:2017)
Essais non destructifs - Contrôle d'étanchéité - Méthode par gaz traceur (ISO
20485:2017)
Ta slovenski standard je istoveten z: EN ISO 20485:2018
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
SIST EN ISO 20485:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 20485:2018
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SIST EN ISO 20485:2018
EN ISO 20485
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2018
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 13185:2001
English Version
Non-destructive testing - Leak testing - Tracer gas method
(ISO 20485:2017)
Essais non destructifs - Contrôle d'étanchéité - Zerstörungsfreie Prüfung - Dichtheitsprüfung -
Méthode par gaz traceur (ISO 20485:2017) Prüfgasverfahren (ISO 20485:2017)
This European Standard was approved by CEN on 26 November 2017.
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, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20485:2018 E
worldwide for CEN national Members.
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SIST EN ISO 20485:2018
EN ISO 20485:2018 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 20485:2018
EN ISO 20485:2018 (E)
European foreword
This document (EN ISO 20485:2018) has been prepared by Technical Committee ISO/TC 135 "Non-
destructive testing" in collaboration with Technical Committee CEN/TC 138 “Non-destructive testing”,
the secretariat of which is held by AFNOR.
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 August 2018, and conflicting national standards shall
be withdrawn at the latest by August 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 13185:2001.
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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 20485:2017 has been approved by CEN as EN ISO 20485:2018 without any modification.
3
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SIST EN ISO 20485:2018
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SIST EN ISO 20485:2018
INTERNATIONAL ISO
STANDARD 20485
First edition
2017-11
Non-destructive testing — Leak testing
— Tracer gas method
Essais non destructifs — Contrôle d'étanchéité — Méthode par gaz
traceur
Reference number
ISO 20485:2017(E)
©
ISO 2017
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SIST EN ISO 20485:2018
ISO 20485:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, 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
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copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 20485:2018
ISO 20485:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles of detection. 1
5 Generation and detection of tracer gas flow . 2
5.1 Tracer gas flows into the object (Group A techniques) . 2
5.2 Tracer gas flows out of the object (Group B techniques) . 2
6 Apparatus . 2
7 Object preparation . 2
8 Group A techniques, tracer gas flows into the object. . 3
8.1 General . 3
8.2 Initial system set-up procedure . 3
8.3 Vacuum technique (total) test procedure (A.1) . 4
8.4 Vacuum technique (partial) test procedure (A.2) . 5
8.5 Vacuum technique (local) test procedure (A.3) . 5
9 Group B techniques, tracer gas flows out of object . 6
9.1 General . 6
9.2 Initial system set up procedure . 7
9.2.1 Ammonia test with colour-change reagents (B.1) . 7
9.2.2 Tracer gas flowing out of the object (B.2, B.3, B.4, B.6) . 7
9.2.3 Pressurisation — Evacuation test (B.5) . 8
9.3 Ammonia test procedure (B.1) . 8
9.3.1 General. 8
9.3.2 Test object preparation . 8
9.3.3 Reagent application . 8
9.3.4 Ammonia pressurization . 8
9.3.5 Impregnation time. 9
9.3.6 Visual examination . 9
9.3.7 Post test cleaning . 9
9.4 Vacuum box test procedure (B.2.1, B.2.2) . 9
9.4.1 General. 9
9.4.2 Vacuum box technique for closed objects B.2.1 . 9
9.4.3 Vacuum box technique for open objects B.2.2 .10
9.5 Accumulation technique (B.3) .10
9.5.1 General.10
9.5.2 Accumulation technique procedure (B.3) .10
9.6 Sniffing test (B.4) .12
9.7 Bombing technique (B.5) .12
9.8 Vacuum chamber technique (B.6) .14
9.9 Carrier gas technique (B.7) .15
10 Test report .16
Annex A (informative) Accumulation technique: calibrated leak connected to enclosure of
unknown volume .17
Bibliography .19
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SIST EN ISO 20485:2018
ISO 20485:2017(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 voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 6, Leak testing.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 20485:2018
INTERNATIONAL STANDARD ISO 20485:2017(E)
Non-destructive testing — Leak testing — Tracer gas method
1 Scope
This document describes the techniques to be applied for the detection of a leak, using a tracer gas and
a tracer gas specific leak detector.
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 20484, Non-destructive testing — Leak testing — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20484 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 http://www.electropedia.org/
4 Principles of detection
A partial pressure difference of tracer gas is created across the boundary of the object to be tested. The
tracer gas, having passed through the leak, is revealed by its physical or chemical properties. Chemical
detection is generally based on reactions that cause a local colour change (the object surface shall
therefore be visible).
Detection based on physical properties usually involves a sensor, for example:
— a mass spectrometer, tuned for the specific tracer gas used (generally helium-4);
— an alkali ion diode, for halogen gas, and electron-capture equipment (i.e. for SF );
6
— a Pirani gauge, for tracer gas with thermal conductivity different from that of the ambient
atmosphere;
— a photometer, with band-pass filter in the frequency range of the tracer gas absorption or emission.
These types of detection generally give an electrical signal which varies with the tracer gas partial
pressure.
The reference conditions should be selected and agreed between a leak tester and a customer. The
reference conditions should be clearly stated and claimed by a leak tester in the test report (see
Clause 10).
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SIST EN ISO 20485:2018
ISO 20485:2017(E)
5 Generation and detection of tracer gas flow
5.1 Tracer gas flows into the object (Group A techniques)
A pressure difference across the wall is obtained either by evacuation of the object, e.g. through a
connection or by placing it in a pressurized chamber. Usually the test object is evacuated. Tracer gas
is then applied to the external surface using a probe jet or by enclosing the object (totally or partially)
in a hood or chamber filled with the tracer gas. Tracer gas leakage into the test object is detected by a
sensor within or connected to the internal volume.
5.2 Tracer gas flows out of the object (Group B techniques)
The object is filled with a tracer gas. A pressure difference across the wall is obtained either by
pressurization of the object, e.g. through a connection or by placing it in a vacuum chamber. The tracer
gas is collected on the outside surface by a sampling probe, a carrier gas flow or by accumulation into a
hood or chamber. Tracer gas can also be detected by chemical reactions.
A special technique (bombing) may also be used. This involves the pressurization of a sealed object
to force the tracer gas into its internal cavities, if a leak exists. The object is then placed in a vacuum
chamber and escaping tracer gas is detected (this procedure is generally used only with helium-4).
This method is applicable to specimens with small free internal volumes (in the order of a few cubic
centimetres).
6 Apparatus
The test apparatus may include part or all of the following:
6.1 Leak detector or chemical reagents able to detect the selected tracer gas.
6.2 Calibrated leaks, calibrated for discharge into vacuum and/or against atmospheric pressure;
refer to ISO 20486.
6.3 Pressure and temperature gauges.
6.4 Tracer gas or certified gas mixture.
6.5 Auxiliary vacuum systems.
6.6 Hood, vacuum or pressurizing chamber, jet or sampling probe.
6.7 Purging dry gas, liquid nitrogen (for cold trap), if necessary.
6.8 Equipment for tracer gas treatment-recovery.
6.9 Equipment for test area ventilation.
6.10 Data recording equipment.
7 Object preparation
The object to be tested shall be adequately cleaned, degreased and dried. Openings and apertures which
are not involved in the test shall be closed with test seals, e.g. plugs, welding, suitable material and
gaskets. Whenever possible, testing should be carried out before plating, painting or the application of
2 © ISO 2017 – All rights reserved
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SIST EN ISO 20485:2018
ISO 20485:2017(E)
ultrasonic couplant. If the object needs to be evacuated, the presence of porous or plastic materials should
be avoided. This helps to avoid spurious indications (virtual leaks), and shortens the clean-up time.
The connections between the object, the pumping system, the leak detector (LD) and the calibrated
leaks used shall be suitable and checked for tightness.
8 Group A techniques, tracer gas flows into the object.
8.1 General
These techniques are applicable to an object that can be evacuated or withstand an external test
pressure. The tracer gas is applied on the outer surface of the object and the LD is connected to the
internal volume. If the LD is of mass spectrometer type (MSLD), the pumping system of the MSLD itself
can be used to directly evacuate small items under test.
Larger objects need an auxiliary pumping system parallel to the LD. In this case, the loss of sensitivity
shall be considered, as only part of the tracer gas will enter the LD.
Three techniques may be used — refer to EN 1779:
— Vacuum technique (Total) (A.1)
The object, placed in an enclosure (a bag or a chamber), is evacuated and connected to the detector.
The enclosure is then filled with the tracer gas or a gas mixture containing the tracer gas. This
technique allows the evaluation of the leakage rate but does not permit precise location of the leaks.
When the purpose of the leak testing is the determination of the acceptability of the test object
against a specified leakage rate, only the "total" technique shall be used. In this case, the tracer
gas concentration, pressure and temperature shall be measured and the homogeneity of the gas
mixture shall be ensured. Further the enclosure shall be gas-tight and, preferably, rigid.
— Vacuum technique (Partial) (A.2)
The object to be tested is evacuated and connected to the detector. Suspect areas are then covered
by a suitable gas-tight enclosure filled with tracer gas.
— Vacuum technique (Local) (A.3)
The object to be tested is evacuated and connected to the detector. Suspect areas on the external
surface of the object are sprayed with tracer gas. Leaks can be localized using this technique but it
is not possible to measure the total leakage rate.
8.2 Initial system set-up procedure
8.2.1 The LD shall be adjusted in accordance with manufacturer’s instructions, using a calibrated leak.
If a MSLD is used, a leak for discharge to vacuum shall be connected directly to the inlet of the LD, or the
built-in leak for the calibration is to be used.
8.2.2 The object is connected to the LD and then evacuated to a suitable pressure, either by LD pumping
system or by an auxiliary pumping system. This is determined by the maximum inlet pressure of the LD.
8.2.3 The initial background signal shall be measured.
8.2.4 The maximum signal for the specified calibrated leak connected to the object shall be recorded
to verify the system sensitivity. The ratio of the pumping speed of the LD to the pumping speed of the
auxiliary system shall not be altered.
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ISO 20485:2017(E)
8.2.5 For large objects or complex systems, the response time of the system shall be measured by
means of a suitable calibrated leak, the rate of leakage of which is as near as possible to the specified
maximum allowable leakage. Unless otherwise specified, this leak shall be connected to the object under
test, via an isolation valve, in the most unfavourable position, to determine the response time.
An auxiliary line should be provided, if possible, to evacuate the volume between the leak outlet and the
isolation valve. In any case, care should be taken to avoid the inlet of the accumulated gas in the system.
The response time is the time from opening of the valve until the 90 % of the maximum stable signal is
reached.
NOTE Although in ISO 20484:2017, 6.1.7, the term "response time" is defined by a signal rise, the practical
measurement is normally based on the signal decay (see ISO 20484:2017, 6.3.1).
8.2.6 To measure the clean-up time, the calibrated leak is closed and the resulting background leakage
rate indication is recorded. Afterwards, the leak is opened and the equilibrium leakage rate indication is
recorded. Then, the leak is closed rapidly and the decay of leakage rate indication is recorded until it has
dropped by 90 % of the equilibrium leakage rate indication with the background indication subtracted.
8.2.7 The signal amplitude and the response time for 90 % signal decrease shall be taken as reference
for the test. The system layout or pumping speed shall not be changed.
8.2.8 To evaluate large leaks that saturate the LD signal, the sensitivity of test can be reduced. This
reduction can be achieved either by lowering the fraction of tracer gas in the mixture or increasing the
pumping speed of the auxiliary system. The response time has to be re-evaluated when the sensitivity of
the test has changed.
8.3 Vacuum technique (total) test procedure (A.1)
8.3.1 After the initial set-up has been performed, the following steps shall be taken.
8.3.2 The object is placed into the auxiliary enclosure (bag or chamber) and it is then evacuated. If the
enclosure is a flexible bag (usually plastic), it shall be sufficiently large to enclose the perimeter of the object.
8.3.3 A preliminary evacuation of the enclosure can be useful. If the enclosure is a flexible bag, it should
lay down well against the object walls (without tearing). After it has been evacuated, the tracer gas is
admitted. If the enclosure has not been evacuated, it should be adequately purged using dry tracer gas,
or a gas mixture containing tracer gas, to ensure that the tracer gas concentration is homogeneous and as
intended. The person performing the test shall note the volume fraction of the tracer gas in the mixture,
so that the corresponding correction in subsequent measurements can be made. If a flexible bag is used,
it shall be filled with gas until it is no longer touching the object walls.
8.3.4 If the enclosure is rigid, pressures shall be recorded before and after tracer gas introduction.
It is possible to calculate the volume fraction of the tracer gas, applying the Boyle-Mariotte law to the
recorded pressures.
8.3.5 The duration of exposure to the full concentration of tracer gas within the auxiliary enclosure
shall be at least twice the response time. When the response time exceeds 20 min, different specifications
for the admission time may be given.
8.3.6 After the appearance of any signal, it is necessary to wait until, either:
— the maximum signal level is obtained: the overall leakage rate can then be calculated by comparison
with the signal generated by the known leak; or
— the signal, corresponding to the maximum allowable leakage rate, is obtained: in this case, the test
can be interrupted for decisions.
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SIST EN ISO 20485:2018
ISO 20485:2017(E)
8.3.7 The total leakage rate of the object, in molecular flow conditions, is calculated according to
Formula (1).
qS×−R
() 1 p
CL LL
atm
q = ×× (1)
G
SR− c p
CL CL
where
q is the total leakage rate;
G
q is the leakage rate of the calibrated leak (pure tracer gas);
CL
S is the leak signal;
L
S is the signal generated by the calibrated leak;
CL
R , R are the background signal associated with signal S and S , respectively;
L CL L CL
c is the volume fraction of the tracer gas in the gas mixture;
p is the total pressure in the auxiliary enclosure;
p is the actual atmospheric pressure.
atm
When the test is carried out with a gas mixture, the volume fraction of tracer gas shall be known
(certified if required) using approved procedures for mixture preparation.
If high accuracy is required, the system calibration shall be performed using a calibrated leak with the
test gas mixture.
8.4 Vacuum technique (partial) test procedure (A.2)
8.4.1 When only a part of an object is to be tested (e.g. welds, thermocouple wells, personnel access
covers, electrical or mechanical feedthroughs), the auxiliary enclosure may be restricted to that area
only. The duration of tracer gas admission shall be indicated in the specification, taking into account the
position of the part under test relative to the pumping system and the LD.
8.4.2 After the initial set-up has been performed, the following steps shall be taken:
8.4.3 Plastic bags or chambers are fitted to the areas to be tested using adhesive tape or suitable
gaskets. These should prevent significant escape of tracer gas during the test.
8.4.4 The object is then evacuated.
8.4.5 Proceed as in 8.3.3 to 8.3.6.
8.5 Vacuum technique (local) test procedure (A.3)
8.5.1 After the initial se
...
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