SIST EN ISO 20486:2018
(Main)Non-destructive testing - Leak testing - Calibration of reference leaks for gases (ISO 20486:2017)
Non-destructive testing - Leak testing - Calibration of reference leaks for gases (ISO 20486:2017)
This draft European Standard specifies the calibration of those leaks that are used for the adjustment of leak detectors for the determination of leakage rate in everyday use. The preferred calibration method in this case is a comparison with a standard leak. In this way the leaks used for routine use become traceable to a primary standard as the ISO 9000 series of standards require. The comparison procedures are preferably applicable to helium leaks, because this test gas can be selectively measured by a mass spectrometer leak detector (MSLD) (the definition of MLSD is given in EN 1330-8). Calibration by comparison (see methods A and B below) with known standard leaks is easily possible for leaks with reservoir and leakage rates below 10-7Pa.m3/s. From 10-7 Pa.m3/s to 10-4 Pa.m3/s no leaks reliable enough to be used as transfer standard exist. Leaks in this range can only be calibrated by measurement of flow in a calibrated capillary tube (see method C below). Leakage rates greater than 10-4 Pa.m3/s can be measured by flow meters calibrated against primary national standards.
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Kalibrieren von Referenzlecks für Gase (ISO 20486:2017)
Dieser Entwurf einer Europäischen Norm spezifiziert die Kalibrierung der Lecks, die für die Justierung von Leckdetektoren für die Bestimmung von Leckageraten im täglichen Gebrauch verwendet werden. Eine Art des Kalibrierverfahrens ist ein Vergleich mit einem normierten Leck. Auf diese Weise werden die Lecks zur routinemäßigen Verwendung auf eine primäre Norm rückführbar, wie es nach der Normenreihe ISO 9000 erforderlich ist. Bei anderen Kalibrierverfahren wurde QpV direkt gemessen oder QpV wurde über ein bekanntes Volumen berechnet.
Die Vergleichsverfahren gelten vorzugsweise für Heliumlecks, da dieses Prüfgas selektiv mithilfe eines Massenspektrometerleckdetektors (en: mass spectrometer leak detector, MSLD) gemessen werden kann (die Definition des MSLD wird in ISO/DIS 20484 angegeben).
Die Kalibrierung durch Vergleich (siehe Verfahren A, As, B und Bs unten) mit bekannten Normlecks ist ein-fach möglich für Lecks mit Reservoir und Leckageraten unter 10–7 Pa m3/s.
Bild 1 zeigt einen Überblick, in dem Bereiche verschiedener Kalibrierverfahren empfohlen werden.
...
Bild 1a — Kalibrierbereich für Kalibrierung durch Vergleich
...
Bild 1b — Kalibrierbereich für Kalibrierung durch
Essais non destructifs - Contrôle d'étanchéité - Étalonnage des fuites de référence des gaz (ISO 20486:2017)
ISO 20486:2017 spécifie l'étalonnage des fuites utilisées dans le réglage des détecteurs de fuites et la détermination des flux de fuite, dans le cadre d'un usage quotidien. Un type de méthode d'étalonnage est une comparaison avec une fuite de référence. Ainsi, les fuites faisant l'objet d'un usage courant deviennent traçables par rapport à un étalon primaire. Dans d'autres méthodes d'étalonnage, la valeur de la pression de vapeur était mesurée directement ou calculée sur un volume connu.
Les modes opératoires d'étalonnage par comparaison sont de préférence applicables aux fuites d'hélium, car ce gaz d'essai peut être mesuré individuellement au moyen d'un détecteur de fuites à spectromètre de masse (DFSM) (la définition de DFSM est donnée dans l'ISO 20484).
L'étalonnage par comparaison (voir méthodes A, As, B et Bs ci-dessous) qui utilise des fuites de référence connues est facilement applicable aux fuites de réservoir et à celles dont les flux de fuite sont inférieurs à 10−7 Pa·m3/s.
Neporušitveno preskušanje - Preiskava tesnosti - Umerjanje referenčne tesnosti za plin (ISO 20486:2017)
Ta osnutek evropskega standarda določa umerjanje uhajanj, ki se uporabljajo za nastavitev detektorjev uhajanja z namenom določanja stopnje uhajanja pri vsakodnevni uporabi. Prednostna metoda umerjanja je v tem primeru primerjava s standardnim uhajanjem. Na ta način postanejo uhajanja pri rutinski uporabi sledljiva na podlagi primarnega standarda, kakor zahteva skupina standardov ISO 9000. Postopki primerjave se prednostno uporabljajo za uhajanje helija, saj je ta preskusni plin mogoče selektivno meriti z detektorjem uhajanja z masnim spektrometrom (MSLD) (opredelitev MSLD je podana v standardu EN 1330-8). Umerjanje na podlagi primerjave (glejte metodi A in B v nadaljevanju) z znanimi standardnimi uhajanji je enostavno izvedljivo za uhajanje iz rezervoarja in stopnjo uhajanja pod 10-7 Pa x m3/s. V območju od 10-7 Pa x m3/s do 10-4 Pa x m3/s uhajanja niso dovolj zanesljiva, da bi jih lahko uporabili kot standard za prenos. Uhajanja v tem območju je mogoče umerjati samo z merjenjem pretoka v umerjeni kapilarni cevi (glejte metodo C v nadaljevanju). Stopnje uhajanja, ki so večje od 10-4 Pa x m3/s je mogoče izmeriti z merilniki pretoka, ki so umerjeni v skladu s primarnimi nacionalnimi standardi.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 20486:2018
01-julij-2018
1DGRPHãþD
SIST EN 13192:2002
SIST EN 13192:2002/AC:2004
1HSRUXãLWYHQRSUHVNXãDQMH3UHLVNDYDWHVQRVWL8PHUMDQMHUHIHUHQþQHWHVQRVWL]D
SOLQ ,62
Non-destructive testing - Leak testing - Calibration of reference leaks for gases (ISO
20486:2017)
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Kalibrieren von Referenzlecks für Gase
(ISO 20486:2017)
Essais non destructifs - Contrôle d'étanchéité - Étalonnage des fuites de référence des
gaz (ISO 20486:2017)
Ta slovenski standard je istoveten z: EN ISO 20486:2018
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
SIST EN ISO 20486:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 20486:2018
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SIST EN ISO 20486:2018
EN ISO 20486
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2018
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN 13192:2001
English Version
Non-destructive testing - Leak testing - Calibration of
reference leaks for gases (ISO 20486:2017)
Essais non destructifs - Contrôle d'étanchéité - Zerstörungsfreie Prüfung - Dichtheitsprüfung -
Étalonnage des fuites de référence des gaz (ISO Kalibrieren von Referenzlecks für Gase (ISO
20486:2017) 20486:2017)
This European Standard was approved by CEN on 23 December 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 20486:2018 E
worldwide for CEN national Members.
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SIST EN ISO 20486:2018
EN ISO 20486:2018 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 20486:2018
EN ISO 20486:2018 (E)
European foreword
This document (EN ISO 20486:2018) 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 13192:2001.
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 20486:2017 has been approved by CEN as EN ISO 20486:2018 without any modification.
3
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SIST EN ISO 20486:2018
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SIST EN ISO 20486:2018
INTERNATIONAL ISO
STANDARD 20486
First edition
2017-12
Non-destructive testing — Leak
testing — Calibration of reference
leaks for gases
Essais non destructifs — Contrôle d'étanchéité — Étalonnage des
fuites de référence des gaz
Reference number
ISO 20486:2017(E)
©
ISO 2017
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SIST EN ISO 20486:2018
ISO 20486:2017(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
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 2017 – All rights reserved
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Nominal leakage rates . 3
5 Classification of leaks . 3
5.1 Permeation leak . 3
5.2 Conductance leaks . 3
5.2.1 Capillary leak . 3
5.2.2 Aperture leak (orifice) . 4
5.2.3 Compressed powder leak . 4
6 Calibration by comparison . 4
6.1 Methods A, A , B and B .
s s 4
6.2 Applicability of comparison methods . 4
6.3 Preparation of leaks and apparatus . 5
6.3.1 Leak detector . 5
6.3.2 Connection to the leak detector . 5
6.3.3 Temperature accommodation . 7
6.4 Measurement . 7
6.4.1 Set-up . 7
6.4.2 General measurement sequence . 7
6.5 Evaluation for methods A, A , B and B (Comparison) . 8
s s
6.5.1 Determination of leakage rate . 8
6.5.2 Influence factors to measurement uncertainty . 9
7 Volumetric calibration.10
7.1 Direct flow (Method C) .10
7.1.1 General.10
7.1.2 Equipment .10
7.1.3 Preparation of leaks and apparatus .10
7.1.4 Measurement .11
7.1.5 Evaluation for Method C (direct flow measurement) .13
7.2 Leak measurement under water (Method D) .14
7.2.1 General.14
7.2.2 Equipment .14
7.2.3 Preparation of leaks and apparatus .14
7.2.4 Measurement .15
7.2.5 Evaluation for Method D .16
7.2.6 Influence factors to measurement uncertainty .17
7.3 Calibration by (volumetric) gas meter (Method E) .17
7.3.1 General.17
7.3.2 Equipment .18
7.3.3 Preparation of leaks and apparatus .18
7.3.4 Measurement .18
7.3.5 Evaluation for Method E (gas meter) .18
7.3.6 Influence factors to measurement uncertainty .19
7.4 Calibration by pressure change in a known volume (Method F) .19
7.4.1 General.19
7.4.2 Preparation of leaks and apparatus .20
7.4.3 Measurement .22
7.4.4 Special situation in vacuum chambers .23
7.4.5 Evaluation for Method F (pressure change) .25
7.4.6 Influence factors to measurement uncertainty .25
© ISO 2017 – All rights reserved iii
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
7.5 Calibration by volume change at constant pressure (Method G) .26
7.5.1 Equipment .26
7.5.2 Preparation of leaks and apparatus .26
7.5.3 Measurement .26
7.5.4 Evaluation for Method G (volume change at constant pressure).27
8 General influences .28
9 Report .28
10 Labelling of reference leaks .29
11 Handling of reference leaks .29
11.1 General .29
11.2 Permeation leaks (normally with reservoir fitted the leak outlet) .29
11.3 Conductance leaks (normally without reservoir) .29
Annex A (informative) Calculation of leakage rate decrease due to tracer gas depletion in
the reservoir .30
Bibliography .32
iv © ISO 2017 – All rights reserved
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SIST EN ISO 20486:2018
ISO 20486:2017(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.
© ISO 2017 – All rights reserved v
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SIST EN ISO 20486:2018
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SIST EN ISO 20486:2018
INTERNATIONAL STANDARD ISO 20486:2017(E)
Non-destructive testing — Leak testing — Calibration of
reference leaks for gases
1 Scope
This document specifies the calibration of those leaks that are used for the adjustment of leak detectors
for the determination of leakage rate in everyday use. One type of calibration method is a comparison
with a reference leak. In this way, the leaks used for routine use become traceable to a primary standard.
In other calibration methods, the value of vapour pressure was measured directly or calculated over a
known volume.
The comparison procedures are preferably applicable to helium leaks, because this test gas can be
selectively measured by a mass spectrometer leak detector (MSLD) (the definition of MSLD is given in
ISO 20484).
Calibration by comparison (see methods A, A , B and B below) with known reference leaks is easily
s s
−7 3
possible for leaks with reservoir and leakage rates below 10 Pa·m /s.
Figure 1 gives an overview of the different recommended calibration methods.
a) Calibration by comparison
© ISO 2017 – All rights reserved 1
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
b) Calibration by direct measurement
Key
3
X leakage rate in Pa·m /s C Method C
A Method A D Method D
B Method B E Method E
A Method A F Method F
s s
B Method B G Method G
s s
normal range possible range
Figure 1 — Calibration ranges
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 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 http://www.electropedia.org/
2 © ISO 2017 – All rights reserved
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
3.1
unknown leak
leak having a stable and repeatable leakage rate of known order of magnitude that can be determined
by calibration
3.2
reference leak
calibrated leak which may be used to calibrate another leak
Note 1 to entry: The uncertainty of the reference leak is lower than the required uncertainty of the leak to be
calibrated.
3.3
calibration
set of operations which establish, under specified conditions, the relationship between leakage rate
values represented by an unknown leak and the corresponding known values of the leakage rate
Note 1 to entry: In the case of calibration by comparison, the known values of the leakage rate are represented by
a reference leak.
Note 2 to entry: Normally, the result of a calibration is given as the leakage rate value for the reference leak with
a standard uncertainty.
3.4
nominal leakage rate
leakage rate of a leak calculated for specified reference conditions
3
Note 1 to entry: In leak detection, leakage rates are commonly given in units of pV-throughput (Pa·m /s, mbar l/s,
3
Std cm /min). These are only a precise measure of gas flow if the temperature is given and kept constant. Flow
units such as mass flow (g/y) or molar flow (mol/s) are sometimes used to overcome this problem.
4 Nominal leakage rates
Calibrated leaks are only comparable under the same reference conditions. Nominal leakage rates shall
be used for comparison. Recommended reference conditions are:
— Ambient temperature: 20 °C
— Atmospheric exhaust pressure: 1 000 mbar
— Vacuum exhaust pressure: < 100 mbar
The reference inlet pressure is given by the leak reservoir pressure or the application requirement.
5 Classification of leaks
5.1 Permeation leak
This type of leak is normally made with a tracer gas reservoir. It has the best long-term stability but an
appreciable temperature coefficient (approximately 3,5 %/K). Typical leakage rates are in the range
−10 3 −4 3
from 10 Pa·m /s to 10 Pa·m /s.
5.2 Conductance leaks
5.2.1 Capillary leak
This type of leak is available with or without a tracer gas reservoir. It has a low temperature coefficient
(approximately 0,3 %/K) but easily blocks if not handled with care. Typical leakage rates are greater
−7 3
than 10 Pa·m /s.
© ISO 2017 – All rights reserved 3
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
5.2.2 Aperture leak (orifice)
Orifices are seldom used as reference leaks in practice, as they are difficult to manufacture and even
more prone to blocking than capillaries.
NOTE Critical flow orifices are a form of aperture leak that is commonly found in industry, but are out of the
scope of this document.
5.2.3 Compressed powder leak
This type of leak uses metal powder compressed into a tube. They are usually offered without reservoir.
They are used for routine check of the sensitivity of leak detectors but they are not stable enough to be
used as calibrated leaks. Their suitability depends on how well controlled the storage and operating
conditions are, and on the required uncertainty.
6 Calibration by comparison
6.1 Methods A, A , B and B
s s
There are two ways of calibrating leaks by comparison with known reference leaks. Both methods
require the knowledge of the order of magnitude of the leakage rate to be measured. The methods
differ in using one or two reference leaks, resulting in different uncertainties of measurement. In the
following, the two methods are designated as A and B:
— Method A: Comparison to one reference leak normally with a leakage rate of the same order of
magnitude, calibration with vacuum method.
— Method A : Comparison to one reference leak normally with a leakage rate of the same order of
s
magnitude, calibration with sniffing method.
— Method B: Comparison to two reference leaks with leakage rates normally lying on either side of the
unknown leakage rate, calibration with vacuum method.
— Method B : Comparison to two reference leaks with leakage rates normally lying on either side of
s
the unknown leakage rate. Calibration with sniffing method.
Method A is most suitable for use on site as only one reference leak is used. It is generally applicable
but is most reliable when the leakage rate of the unknown is close to that of the reference leak. This is
because the measurement uncertainty is directly dependent on the linearity of the leak detector in use.
As the linearity error cannot be measured independently, it needs to be estimated. To keep the linearity
error small, the operating characteristics of leak detector should not change during calibration (e.g.
automatic ranging should be disabled).
For more precise calibrations, where a more reliable measure of uncertainty is required or if a reference
leak with a leakage rate close to the unknown is not available Method B should be used. By the use of
two reference leaks, the non-linearity of the leak detector is accounted for.
6.2 Applicability of comparison methods
Since comparison of leaks is not a fundamental measurement method, it relies on the stability of the
transfer device and cleanliness of the ambient gas atmosphere. Moreover, the temperature dependence
of the reference and unknown leaks shall be taken into account.
The most stable and clean conditions are achieved for leaks with exhaust into vacuum and a mass
spectrometer leak detector as transfer device measuring the partial pressure generated by the leaks in
vacuum. Under these conditions, all interfering background gases are reduced to a minimum so that the
zero point of the transfer device is defined and stable.
4 © ISO 2017 – All rights reserved
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SIST EN ISO 20486:2018
ISO 20486:2017(E)
For leaks with exhaust into the atmosphere and measurement by sniffing gas, more conditions shall be
controlled. These are:
— the background level of tracer gas shall be as low as possible and as stable as possible;
— the total gas flow rate of the sniffer shall be high enough to take up the total tracer gas flow out of
the leak;
— the aspiration of the sniffer (the coupling to the leak exhaust) shall be of suitable geometry to make
sure that the atmospheric gas flow across the leak exhaust takes up the whole tracer gas flow from
the leak opening.
As a consequence, the measurement uncertainty is appreciably higher for sniffer leaks than for
vacuum leaks.
Methods by comparison are therefore applicable but not preferable for the calibration of sniffer leaks
(with exhaust to atmosphere).
6.3 Preparation of leaks and apparatus
6.3.1 Leak detector
The leak detector (LD) used as a transfer device shall be set up according to the manufacturer’s manual.
The warm-up time shall be at least 2 h.
6.3.2 Connection to the leak detector
The reference and unknown leaks are connected to the leak detector used as the transfer instrument.
The connection shall be kept continuously until the measurement is completed. This includes thermal
[1]
accommodation .
In the case of vacuum leaks, they are connected to the inlet flange and pumped with their valves (if any)
open for at least 30 min to remove any tracer gas that can have accumulated in seals or valves. For the
calibration of more than one leak, a separate pumping syste
...
SLOVENSKI STANDARD
oSIST prEN ISO 20486:2016
01-oktober-2016
1HSRUXãLWYHQRSUHVNXãDQMH3UHVNXãDQMHWHVQRVWL8PHUMDQMHUHIHUHQþQHWHVQRVWL
]DSOLQ ,62',6
Non-destructive testing - Leak testing - Calibration of reference leaks for gases (ISO/DIS
20486:2016)
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Kalibrieren von Referenzlecks für Gase
(ISO/DIS 20486:2016)
Essais non destructifs - Contrôle d'étanchéité - Étalonnage des fuites de référence des
gaz (ISO/DIS 20486:2016)
Ta slovenski standard je istoveten z: prEN ISO 20486
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
oSIST prEN ISO 20486:2016 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN ISO 20486:2016
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oSIST prEN ISO 20486:2016
DRAFT INTERNATIONAL STANDARD
ISO/DIS 20486
ISO/TC 135/SC 6 Secretariat: JISC
Voting begins on: Voting terminates on:
2016-08-30 2016-11-21
Non-destructive testing — Leak testing — Calibration of
reference leaks for gases
Essais non destructifs — Contrôle d’étanchéité — Étalonnage des fuites de référence des gaz
ICS: 19.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 20486:2016(E)
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. ISO 2016
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oSIST prEN ISO 20486:2016
ISO/DIS 20486:2016(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
---------------------- Page: 4 ----------------------
oSIST prEN ISO 20486:2016
ISO/DIS 20486:2016(E)
Contents Page
Foreword . v
1 Scope .1
2 Normative references .2
3 Terms and definitions .2
4 Reference conditions for nominal leakage rates .3
5 Classification of leaks .3
5.1 Permeation leak .3
5.2 Conductance leaks .4
5.2.1 Capillary leak .4
5.2.2 Aperture leak (orifice) .4
5.2.3 Compressed powder leak .4
6 Calibration by comparison .4
6.1 Methods A, A , B and B .4
s s
6.2 Applicability of comparison methods .5
6.3 Preparation of leaks and apparatus .5
6.3.1 Warm-up of leak detector .5
6.3.2 Temperature accommodation .5
6.3.3 Connection to the leak detector .5
6.4 Measurement .6
6.4.1 Set-up .6
6.4.2 General measurement sequence .6
6.5 Evaluation for methods A, A , B and B (Comparison) .7
s s
6.5.1 Determination of leakage rate .7
7 Volumetric calibration .9
7.1 Direct flow (Method C) .9
7.1.1 General .9
7.1.2 Equipment .9
7.1.3 Preparation of leaks and apparatus .9
7.1.4 Measurement . 10
7.1.5 Evaluation for Method C (direct flow measurement) . 11
7.2 Leak measurement under water (Method D) . 13
7.2.1 General . 13
7.2.2 Equipment . 13
7.2.3 Preparation of leaks and apparatus . 13
7.2.4 Measurement . 14
7.2.5 Evaluation for Method D . 15
7.2.6 Calculation of measurement uncertainty . 16
7.3 Calibration by gas meter (Method E) . 16
7.3.1 Equipment . 16
7.3.2 Preparation of leaks and apparatures . 16
7.3.3 Measurement . 16
7.3.4 Evaluation for Method E (gas meter) . 17
7.4 Calibration by pressure change in a known volume (Method F) . 18
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7.4.1 General . 18
7.4.2 Preparation of leaks and apparatus . 18
7.4.3 Measurement . 21
7.4.4 Special situation in vacuum chambers . 22
7.4.5 Evaluation for Method F (pressure change) . 23
7.4.6 Calculation of measurement uncertainty . 24
7.5 Calibration by volume change at constant pressure (Method G) . 24
7.5.1 Equipment . 24
7.5.2 Preparation of leaks and apparatus . 25
7.5.3 Measurement . 25
7.5.4 Evaluation for Method G (volume change at constant pressure) . 26
8 General influences . 27
9 Report . 27
10 Labelling of reference leaks . 28
11 Handling of reference leaks. 28
11.1 General . 28
11.2 Permeation leaks (normally with reservoir fitted the leak outlet) . 28
11.3 Conductance leaks (normally without reservoir) . 28
(informative) Calculation of leakage rate decrease due to tracer gas depletion in
the reservoir . 29
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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.
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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 World Trade Organization (WTO)
principles in the Technical Barriers to Trade (TBT) see the following URL:
www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 138 “Non-destructive testing”, the secretariat of
which is held by JISC.
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DRAFT INTERNATIONAL STANDARD ISO/DIS 20486:2016(E)
Non destructive testing — Leak Test — Calibration of
reference leaks for gases
1 Scope
This draft European Standard specifies the calibration of those leaks that are used for the adjustment of
leak detectors for the determination of leakage rate in everyday use. One type of calibration method is a
comparison with a standard leak. In this way the leaks used for routine use become traceable to a
primary standard as the ISO 9000 series of standards require. At other calibration methods the Q was
pV
measured directly or the Q was calculated over a known volume.
pV
The comparison procedures are preferably applicable to helium leaks, because this test gas can be
selectively measured by a mass spectrometer leak detector (MSLD) (the definition of MLSD is given in
ISO/DIS 20484).
Calibration by comparison (see methods A, A B and B below) with known standard leaks is easily
s s
–7 3
possible for leaks with reservoir and leakage rates below 10 Pa·m /s.
Figure 1 gives an overview in which ranges the different calibration methods are recommended.
Key
3
X – leakage rate in Pa·m /s
A – Method A A – Method A
s s
B – Method B B – Method B
s s
– normal range – possible range
Figure 1a — Calibration range at calibration by comparison
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Key
3
X – leakage rate in Pa·m /s E – Method E
C – Method C F – Method F
D – Method D G – Method G
– normal range – possible range
Figure 1b — Calibration range at calibration by
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 13625, Non-destructive testing — Leak test — Guide to the selection of instrumentation for the
measurement of gas leakage
ISO 20484, Non-destructive testing — Leak testing — Vocabulary
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20484 and the following
apply.
3.1
unknown leak
leak having a stable and repeatable leakage rate of known order of magnitude that can be determined
by calibration
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3.2
reference leak
calibrated leak which may be used to calibrate another leak
Note 1 to entry: The uncertainty of the reference leak is lower than the required uncertainty of the leak to be
calibrated.
3.3
calibration of a reference leak
set of operations which establish, under specified conditions, the relationship between leakage rate
values represented by an unknown leak and the corresponding known values of the leakage rate
Note 1 to entry: In the case of calibration by comparison, the known values of the leakage rate are represented
by a standard leak.
Note 2 to entry: Normally, the result of a calibration is given as the leakage rate value for the reference leak.
3.4
calibrated leakage rate
result of the calibration of a reference leak under the given calibration conditions
3.5
nominal leakage rate
leakage rate of a leak calculated for specified reference conditions
3
Note 1 to entry: In leak detection, leakage rates are commonly given in units of pV-throughput (Pa·m /s,
3
mbar l/s, cm /min). These are only a precise measure of gas flow if the temperature is given and kept constant.
Flow units such as mass flow (g/y) or molar flow (mol/s) are sometimes used to overcome this problem.
4 Reference conditions for nominal leakage rates
To make leaks comparable the nominal leakage rate of a leak shall be given for the following reference
conditions:
Ambient temperature: 20 °C
Atmospheric exhaust pressure: 1 000 mbar
Vacuum exhaust pressure: < 100 mbar
The reference inlet pressure is given by the leak reservoir pressure or the application requirement.
5 Classification of leaks
5.1 Permeation leak
This type of leak is normally made with a tracer gas reservoir. It has the best long-term stability but an
appreciable temperature coefficient (approximately 3,5 %/K). Typical leakage rates are in the range
–10 3 –4 3
from 10 Pa·m /s to 10 Pa·m /s.
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5.2 Conductance leaks
5.2.1 Capillary leak
This type of leak is available with or without a tracer gas reservoir. It has a low temperature coefficient
(approximately 0,3 %/K) but easily blocks if not handled with care. Typical leakage rates are greater
–7 3
than 10 Pa·m /s
5.2.2 Aperture leak (orifice)
Orifice leaks are seldom used in practice, as they are difficult to manufacture and even more prone to
blocking than capillaries.
5.2.3 Compressed powder leak
This type of leak uses metal powder compressed into a tube. They are usually offered without reservoir.
They are used for routine check of the sensitivity of leak detectors but they are not stable enough to be
used as calibration leaks.
6 Calibration by comparison
6.1 Methods A, A , B and B
s s
There are two ways of calibrating leaks by comparison with known standard leaks. Both methods
require the knowledge of the order of magnitude of the leakage rate to be measured. The methods differ
in using one or two standard leaks, resulting in different uncertainties of measurement. In the following,
the two methods are designated as A, A , B and B :
s s
Method A: Comparison to one standard leak normally with a leakage rate of the same order of
magnitude, calibration with vacuum method
Method A : Comparison to one standard leak normally with a leakage rate of the same order of
s
magnitude, calibration with sniffing method
Method B: Comparison to two standard leaks with leakage rates normally lying on either side of the
unknown leakage rate, calibration with vacuum method
Method B : Comparison to two standard leaks with leakage rates normally lying on either side of the
s
unknown leakage rate. Calibration with sniffing method
Method A is most suitable for use on site as only one standard leak is used. It is generally applicable but
is most reliable when the leakage rate of the unknown is close to that of the standard leak. This is
because the measurement uncertainty is directly dependent on the linearity of the leak detector in use.
(See 8.1.2.1). As the linearity error cannot be measured independently, it has to be estimated. To keep
the linearity error small, the operating characteristics of leak detector should not change during
calibration (e.g. automatic ranging should be disabled).
For more precise calibrations, where a definite measure of uncertainty is required or if a standard leak
with a leakage rate close to the unknown is not available Method B should be used. By the use of two
reference leaks, the non-linearity of the leak detector is accounted for (see 8.1.2.2).
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6.2 Applicability of comparison methods
Since comparison of leaks is not a fundamental measurement method it relies on boundary conditions,
mainly the stability of the transfer instrument and cleanliness of the ambient gas atmosphere.
Moreover, the temperature dependence of the reference and unknown leaks must be taken into
account.
The most stable and clean conditions are achieved for leaks with exhaust into vacuum and a mass
spectrometer leak detector (“transfer instrument”) measuring the partial pressure generated by the
leaks in vacuum. Under these conditions all interfering background gases are reduced to a minimum so
that the zero point of the transfer instrument is defined and stable.
For leaks with exhaust into the atmosphere and measurement by sniffing gas some more conditions
must be controlled. These are:
— the background level of tracer gas must be as low as possible and as stable as possible;
— the total gas flow rate of the sniffer shall be high enough to take up the total tracer gas flow out of
the leak;
— the aspiration of the sniffer (the coupling to the leak exhaust) shall be of suitable geometry to make
sure that the atmospheric gas flow across the leak exhaust takes up the whole tracer gas flow from
the leak opening.
As a consequence, the measurement uncertainty is appreciably higher for sniffer leaks than for vacuum
leaks.
Methods by comparison are therefore applicable but not preferable for the calibration of sniffer leaks
(with exhaust to atmosphere).
6.3 Preparation of leaks and apparatus
6.3.1 Warm-up of leak detector
The leak detector used as a transfer device shall be set up according to the manufacturer’s manual. The
warm-up time shall be at least 2 h.
6.3.2 Temperature accommodation
The unknown leak and the standard leak(s) for the comparison shall be stored in the same room where
the test is to be carried out for at least 12 h to allow for temperature equilibration (an air-conditioned
room is not necessary if there are no rapid temperature changes. Because of temperature fluctuations,
an air-conditioning system can even increase the measurement uncertainty). Vacuum leaks shall be
pumped during the phase of thermal accommodation. After temperature accommodation, to prevent
any temperature changes during measurement, thermally insulating hoods (made of plastic foam or
similar material) should be put over the leaks.
6.3.3 Connection to the leak detector
The standard and unknown leaks are connected to the leak detector used as the transfer instrument
after temperature accommodation.
In the case of vacuum leaks they are connected to the inlet flange and pumped with their valves (if any)
open for at least 30 min to remove any tracer gas that may have accumulated in seals or valves. For the
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calibration of more than one leak, a separate pumping system and set of valves is useful to keep all the
leaks pumped until they are measured.
In the case of sniffer leaks the connection to the leak detector sniffing tip is made by an adapter which
makes a tight connection to the leak outlet and enables atmospheric air to be continuously sucked
across the leak exhaust so that the whole leak gas flow is taken up by the sniffer tip. The air inlet
opening shall not throttle the free flow of air to maintain atmospheric pressure in front of the sniffer tip.
Key
1 gasket 4 test leak with leak opening
2 sniffer tip 5 adapter body with gasket
3 air inlet 6 sniffer opening with cross-wise slot
Figure 2 — Example for a coupling adaptor for sniffer leaks
6.4 Measurement
6.4.1 Set-up
It is important to ensure that the effective pumping speed at the leak detector inlet respectively the
sniffer gas flow is not changed during the measurements. If possible, either with the leak detector or in
an auxiliary device a long averaging time may be used to decrease the statistical measurement
uncertainty. All the measurement instruments should be adjusted in such a way that they give nearly
full-scale deflections for the biggest leak.
6.4.2 General measurement sequence
Generally, each reading shall be obtained only after the signal of the transfer instrument has stabilized.
A sufficient number of readings have to be taken to achieve the lowest possible statistical uncertainty.
In this way a measure of statistic deviation can also be found. The general sequence of measurements is
as follows:
a) zero signal determination: all valves closed for vacuum leaks, respectively sniffer tip in pure
ambient air for sniffing leaks;
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b) connect standard leak no. 1, wait for steady flow and measure the resulting output signal
(Method A, A , B and B );
s s
c) disconnect standard leak no.1;
d) connect standard leak no. 2, wait for steady flow and measure the resulting output signal (only
Method B and B );
s
e) disconnect standard leak no. 2;
f) connect unknown leaks, wait for steady flow and measure the resulting output signal;
g) repeat a) to f) at least three times.
NOTE Leak valves should be kept closed for as short a time as possible to prevent extensive helium
accumulation resulting in long equilibration time.
6.5 Evaluation for methods A, A , B and B (Comparison)
s s
6.5.1 Determination of leakage rate
6.5.1.1 Method A and A : Result of comparison to one standard leak
s
The following formula is used to calculate the unknown leakage rate Q from the reading R of the
u ref
standard leak with leakage rate Q and the reading R of the unknown leak:
std u
𝑅
u
𝑄 = 𝑄
(1a)
𝑢 ref
𝑅
ref
This formula is only valid, if the temperature coefficients and the temperatures of all leaks are equal.
Otherwise, the following formula shall be used:
( )
𝑅 1 + 𝛼 ⋅ 𝛥𝑇
u ref ref
𝑄 = 𝑄 ⋅ [ ] (1b)
u ref
𝑅 (1 + 𝛼 ⋅ 𝛥𝑇 )
ref u u
where
Q Q are the leakage rates of the reference and unknown leak respectively;
ref, u
R , R the readings of the reference and unknown leak respectively;
ref u
, are the temperature coefficients of the reference and unknown leak respectively;
ref u
T , T are the departures of the temperature of the leaks from the reference temperature of
ref u
the standard and unknown leak respectively.
The readings can be in any consistent units, as only ratios are considered.
NOTE 1 The readings (R and R ) are obtained from the leak detector display as the difference of the output
ref u
signals with leak connected and disconnected (resp. valve opened and closed).
NOTE 2 The temperature coefficient of the reference leak will normally be stated. If the temperature coefficient
of the unknown leak is not given it can be assumed that for a quartz permeation leak it is approximately 3,5 %/K
and for conductance type leaks 0,3 %/K.
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6.5.1.2 Method B and Bs: Result of comparison to two reference leaks
To keep this procedure practical, only the case of equal temperature coefficients and temperatures of all
leaks is considered. In this case the following simplified formula holds:
𝑅 − 𝑅
u 1
𝑄 = (𝑄 − 𝑄 ) ( ) + 𝑄
u 2 1 1
𝑅
...
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