SIST EN 13184:2002
(Main)Non-destructive testing - Leak testing - Pressure change method
Non-destructive testing - Leak testing - Pressure change method
This standard describes the techniques for the determination of the rate of leakage across the boundary of an isolated object, subjected to a pressure difference. The techniques are based on the evaluation of the change of the mass of gas within the test object. The ideal gas equation states the relationship between mass, pressure, temperature and volume of the gas contained in the internal free volume of the object. In some circumstances one or more variables may be considered constant and so the mass change can, for example, be assessed by monitoring the pressure or pressure-temperature changes within the test object.
Zerstörungsfreie Prüfung - Dichtheitsprüfung - Druckänderungsverfahren
1 Anwendungsbereich
Diese Europäische Norm legt die Verfahren zur Bestimmung der Strömung durch Lecks in der Umwandung
eines abgeschlossenen Prüfobjektes, das einem Druckgefälle ausgesetzt ist, fest. Die Verfahren beruhen auf
der Auswertung der Änderung der Gasmasse innerhalb des Prüfobjektes. Die Zustandsgleichung für ideale
Gase gibt das Verhältnis zwischen Masse, Druck, Temperatur und Volumen des Gases an, das im freien Innen-volumen
des Prüfobjektes enthalten ist. Unter bestimmten Umständen dürfen eine oder mehrere Variable als Seite 3
EN 13184:2001
konstant angenommen werden, und damit kann die Massenänderung zum Beispiel durch Kontrolle der
Druckänderung oder der Druck-Temperatur-Änderung innerhalb des Prüfobjektes beurteilt werden.
Die Volumenänderung des Prüfobjektes (aufgrund von Druck- und Temperaturänderung bei der Prüfung) sollte
berücksichtigt werden. In den meisten industriellen Anwendungen ist diese Änderung jedoch so klein, dass sie
vernachlässigt werden kann. Im größten Teil dieser Norm wird deshalb das Volumen während der Prüfung als
konstant angenommen.
Die Verformbarkeit des Prüfobjektes wird üblicherweise bei der Planung der Prüfspezifikation berücksichtigt
werden, und wenn die Prüfgenauigkeit durch eine Volumenänderung beeinflusst werden kann, können alternative
Formeln oder Verfahren, bei denen der Druck konstant gehalten wird (Strömungsmessung), angewendet
werden.
Essais non destructifs - Contrôle d'étanchéité - Méthode par variation de pression
Ce projet de norme décrit les techniques de détermination des flux de fuite de part et d'autre de la paroi d'un objet isolé, soumis a une différence de pression. Ces techniques se basent sur l'évaluation de la variation de la masse de gaz a l'intérieur de l'objet contrôlé. L'équation d'un gaz parfait établit la relation entre masse, pression, température, et volume d'un gaz présent dans le volume interne vide de l'objet. Dans certaines circonstances, une ou plusieurs variables peuvent etre considérées comme constantes et ainsi, toute variation de masse peut etre évaluée en surveillant, par exemple, les variations de pression ou de pression-température survenant a l'intérieur de l'objet contrôlé.
Il y a lieu de tenir compte des variations de volume de l'objet (dues a des variations de température ou de pression pendant le test). Cependant, dans la plupart des applications industrielles, ces modifications sont si infimes qu'elles peuvent etre considérées comme négligeables. En regle générale, dans la présente norme, le volume sera considéré comme une constante pendant le test.
La déformabilité de l'objet contrôlé est généralement prise en compte pour établir les spécifications du test et si la précision du test peut etre affectée par une variation de volume, d'autres formules ou des techniques permettant de maintenir la pression constante (mesure de flux) peuvent etre utilisées.
Neporušitveno preskušanje - Preskušanje tesnosti - Metoda spremembe tlaka
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Neporušitveno preskušanje - Preskušanje tesnosti - Metoda spremembe tlakaZerstörungsfreie Prüfung - Dichtheitsprüfung - DruckänderungsverfahrenEssais non destructifs - Contrôle d'étanchéité - Méthode par variation de pressionNon-destructive testing - Leak testing - Pressure change method19.100Neporušitveno preskušanjeNon-destructive testingICS:Ta slovenski standard je istoveten z:EN 13184:2001SIST EN 13184:2002en01-junij-2002SIST EN 13184:2002SLOVENSKI
STANDARD
SIST EN 13184:2002
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13184March 2001ICS 19.100English versionNon-destructive testing - Leak testing - Pressure change methodEssais non destructifs - Contrôle d'étanchéité - Méthodepar variation de pressionZerstörungsfreie Prüfung - Dichtheitsprüfung -DruckänderungsverfahrenThis European Standard was approved by CEN on 18 January 2001.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2001 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13184:2001 ESIST EN 13184:2002
Page 2EN 13184:2001ContentsPageForeword.31Scope.42Normative references.43Terms and definitions.44Personnel qualification.45General Requirements.56Calibration.67Pressure Decay Technique - See EN 1779, Technique D.1.68Pressure Rise Technique - See EN 1779, Technique D.2.109Bell Pressure Change Technique - See EN 1779, Technique D.3.1110Flow Measurement Technique - See EN 1779, Technique D.4.1311Test Report.14Annex A (normative)
Calculations for pressure change methods.17Annex B (informative)
Determination of the leakage rate in the presence of outgassing and permeation.19Annex C (informative)
Check for leakage across the isolation valve.21Annex ZA (informative)
Clauses of this European Standard addressing essential requirements or otherprovisions of EU Directives.22SIST EN 13184:2002
Page 3EN 13184:2001ForewordThis European Standard has been prepared by Technical Committee CEN/TC 138 "Non-destructive testing", thesecretariat 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 orby endorsement, at the latest by September 2001, and conflicting national standards shall be withdrawn at thelatest by September 2001.This European Standard has been prepared under a mandate given to CEN by the European Commission and theEuropean Free Trade Association, and supports essential requirements of EU Directive(s).For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this standard.Annex A is normative, the annexes B and C are informative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,Switzerland and the United Kingdom.SIST EN 13184:2002
Page 4EN 13184:20011 ScopeThis document describes the techniques for the determination of the leakage rates across the boundary of anisolated object, subjected to a pressure difference. The techniques are based on the evaluation of the change ofthe mass of gas within the test object. The ideal gas equation states the relationship between mass, pressure,temperature, volume of the gas contained in the internal free volume of the object. In some circumstances one ormore variables may be considered constant and so the mass change can, for example, be assessed by monitoringthe pressure or pressure-temperature changes within the test object.The volume change of the object (due to pressure and temperature changes during the test) should be taken intoaccount. In most industrial applications, however, this change is so small that can be neglected. Therefore the mainpart of this standard considers the volume as a constant during the test.The deformability of the object under test is normally be considered in drafting of the test specification and, if testprecision can be affected by a volume change, alternative formulas or some techniques of keeping the pressureconstant (flow measurement) can be used.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).EN 473
Qualification and certification of NDT personnel - General principlesEN 1330-8
Non destructive testing - Terminology- Part 8 - Terms used in leak tightness testingEN 1779
Non destructive testing - Leak testing
- Criteria for method and technique selectionEN 13185:2001
Non destructive testing
-Leak testing - Tracer gas methodprEN 13625:2001
Non destructive testing
- Leak test - Guide to the selection of instrumentation for themeasurement of gas leakage3 Terms and definitionsFor the purposes of this European Standard, the following terms and definitions given in EN 1330-8 and thefollowing apply.3.1differential pressure gaugeinstrument measuring the difference between two pressures4 Personnel qualificationIt is assumed that leak tightness testing is performed by qualified and capable personnel. In order to prove thisqualification, it is recommended to certify the personnel according to EN 473 or equivalent.NOTEFor pressure equipment see directive 97/23/EC (Annex I, paragraph 3.1.3) : "For pressure equipment in categoriesIII and IV, the personnel must be approved by a third party organization recognized by a Member State"SIST EN 13184:2002
Page 5EN 13184:20015 General Requirements5.1 SafetyThe design of the object under test shall be checked to ensure its integrity under the pressure differential, at thetemperature of the test, having regard for the effects of the temperature increases due to ambient changes, solarheating, etc. Specific devices to prevent excessive pressure gradients may have to be provided in accordance withlocal safety regulations to assure that the design limits cannot be exceeded.5.2 FeasibilityThe leakage rate determines the change in the total pressure that takes place over a given period of time. Becauseof this, the resolution of gauges should be such that the pressure change can be determined accurately.
Theinstrument sensitivity is related to the final reading: this sensitivity should be at minimum five to ten times higherthan the pressure to be expected.The instrument resolution has to be defined with the acceptance criteria.5.3 Test intruments5.3.1 Types of gauges - see prEN 13625:2001 Vacuum gauges suitable for the test pressure range; Pressure gauges: Absolute or differential pressure gauges may be used.
When differential pressure gaugesare used, reference pressure variations shall be monitored and taken into account; Thermometers: Resistance thermometers are generally used for temperature measurements, but otherdevices may be employed; Hygrometer: For the measurements of the humidity or the dew point of test gas, capacitive or resistive typeinstruments may be used; Flowmeters may be of mass or volumetric types, with an integrator device.All instruments shall have ranges, resolution, accuracy, and repeatability compatible with the acceptance criteria.5.3.2 LocationFor pressure measurement either single or a small number of sensors are normally used.NOTESensors should be placed in the most appropriate position in the test object.With large vessels or complex systems, the temperature and dew point at several positions shall be monitoredsince these can vary across a system, particularly if there are thermally isolated, occluded or dead volumes. Suchvariation shall be taken into account in the calculations.Dials and indicating/recording devices shall be readily accessible to the operator.In long term tests, an appropriate number of sensors shall be used so that the failure of one or more sensors willnot invalidate the test.5.4 Auxiliary equipmentAuxiliary equipment used in the performance of the test includes: compressors or vacuum pump systems; pressure regulators, dryers, tight chambers;SIST EN 13184:2002
Page 6EN 13184:2001 valves, vent lines, safety devices against over pressure or high vacuum.6 CalibrationAll the instruments shall be calibrated against devices that are traceable to National Standards.7 Pressure Decay Technique - See EN 1779, Technique D.17.1 ApplicationThis method is applicable to test objects or systems that can withstand an internal overpressure withoutdeformation or significant variation of the volume. The internal free volume shall be known, unless the leakage rateis specified as a rate of pressure fall within the pressure involved.If the test is carried out under conditions different from those characteristics of normal operation (different operatingfluids, different pressure), this shall be taken into account in the test procedures and in the test acceptance limits.7.2 Working principleThe object under test is subjected to a positive differential pressure (either by pressurization or by placing it in avacuum chamber). The pressure source is then isolated and, after a suitable temperature stabilization time, thepressure and the temperature reading (dew point readings if required) are recorded at regular intervals.Two techniques may be used:7.2.1 Absolute techniqueThe indicated pressure is the absolute pressure.7.2.2 Reference vessel techniqueThe pressure within the test object is compared to the pressure inside a reference object. The latter may be asealed volume located within the test object, of such a geometry that it can assume the temperature of theatmosphere of the object. The reference volume shall have a pressure slightly lower than the object and shall betested for tightness before and after the test; its temperature shall also be recorded.7.3 Free volume measurementThe internal free volume of the object shall be accurately assessed if the leakage rate is to be stated as a massflow.Volume can be estimated, for example, from several measurements of a significant pressure fall over a short giventime caused by a measured leakage rate through a valve. The volume can be estimated from the average value ofthe pressure drop and the total gas lost.If the leakage rate is expressed as a percentage of the total mass of enclosed gas lost per unit time, then aknowledge of the enclosed free volume is not required.7.4 Procedure7.4.1 Object preparationThe object shall be clean and dry. All internal components that cannot withstand the test pressure shall beremoved. Part of the system not subjected to the test shall be isolated, using suitable devices, including temporaryblank flanges, welded if necessary.SIST EN 13184:2002
Page 7EN 13184:2001Large thin-walled tanks should be monitored (strain gauges) in order to take into account sudden volume changesdue to boundary instability.Care shall be taken where trapped or poorly- accessible volumes may be encountered (double bead welds, settles,double-gasket penetrations) because they can increase the stabilization time and the uncertainty of the test.If the procedure requires the reference vessel, this shall be placed in position, with temperature sensors fitted.Air circulating systems, such as fans, can be installed in large vessels to increase the uniformity of conditions, butthe system heat sources shall be taken into account.7.4.2 PressurizationThe object shall be pressurized using gas clean, free of contaminants and as dry as possible.Cylinder gases or air compressors with a dryer system may be used. To reduce the temperature stabilization time,the inlet gas temperature should be close to that of the air in the object.7.4.3 Stabilization timeAfter the test pressure is reached the pressure source is insulated. A stabilization period of not less than 1 h isnecessary, mainly for temperature and moisture equalization. However, with vessels or systems having a largecapacity (e.g. several hundreds of m3), stability can be considered to have been reached when the temperature,averaged over 1 h, does not deviate by more than 0,5°C from the average change over the previous 2 h.7.4.4 Test procedureIt is desirable to minimize the effects of draughts and sunlight.After the stabilization period, the test commences and the actual pressure is recorded. The temperature and dewpoint (moisture content) are also recorded if required. The pressure or the pressure decay (referred to the initialpressure), corrected for the temperature effect, is plotted against the elapsed time. If, during the test, in all areas ofthe object and at any temperature conditions, the relative humidity remains below 90%, perfect gas behaviour canbe assumed. This assumption is possible in most industrial conditions because in this range the change of thespecific volume of the moist air, due to the temperature changes, at constant specific humidity, differs less than0,1% from that of the dry air change. If these conditions are not fulfilled, the calculations shall be performed using apsychrometric chart, in order to take into account the specific volume changes of the moist air and the possiblecondensation of water (assume volume 0 for condensed phase).If the pressure reading is relative to atmospheric pressure, the barometric pressure shall also be recorded.7.4.5 Test durationThe duration of the test depends on the dimensions of the test object or the test accuracy or scope (e.g. shortduration tests for pass/fail differentiation). If calculations are required however to determine the actual leakagevalue, the duration of the test period shall be sufficient to enable adequate data to be accumulated to calculate theleakage rate. Furthermore, statistical analysis of the results and the upper confidence limit may be required. In thiscase, a minimum of 20 sets of data points, at approximately equal time intervals, should be available and the testshould not last less than 8 h, after initial stabilization.For large vessels, complex systems or outdoor vessels in the sunlight, a period of 24 h (or multiples of this) isrecommended, to reach similar ambient conditions at the beginning and end of the test.7.4.6 CalculationsThe mass of the contained test gas is determined at any point from the application of the ideal gas law:TRMmVpTRVMpmSIST EN 13184:2002
Page 8EN 13184:2001TppTRVMmvwhereVis the internal free volume in cubic metres;Ris the universal gas constant, in joules per mole and kelvin;pis the total pressure, in pascals;pv(T)is the partial pressure of water vapour, in pascals, at temperature T, in kelvins;mis the
total mass of non-condensable gas, in kilograms;Mis the molar mass of the test gas, in kilograms per mole;Tis the temperature of the test gas, in kelvins;m’is the mass of the test gas, in kilograms.The mass loss is:22v211v121TTppTTppRVMmmwhere the subscripts 1, 2
refer to the
test gas at the beginning and the end of the test respectively.Within the limits of 7.4.4 for relative humidity, water vapour can be considered to behave as an ideal gas and theexpression results:221121TpTpRVMmmThe mass loss can be converted to a volume loss at standard conditions pS, TS , since:ssspTRnVwith Mmnwherenis the number of molesSo, the leakage rate given as pV throughput becomes:2211spTpTp tTV Vqwheretis the duration of the test;SIST EN 13184:2002
Page 9EN 13184:2001and the leakage rate, expressed as a percentage of loss (mass, pressure):1001%2112TpTp7.5 Data analysis and confidence interval(The procedure described apply only to high precision tests or to large critical components)Analysis should be carried out on the mass versus time plot throughout the test period. It is suggested that themass loss obtained from the readings is checked
every four hours at time t0, t4, t8,. repeating a second series attime t2, t6, t10,.The spread of the result in each sequence or between the two sequences can indicate the importance
of the effectof unforeseen variables on the test.The average between these values may sometimes be sufficient for determining leakage rate.If required however or if the spread of the results is too large, a linear regression in the form of:y = A + B Twhereyis the calculated quantity (mass) at time t;Ais the intercept of the line on y-axis;Bis the slope of the line;Tis the time elapsed from the beginning of the test;shall be calculated and an upper confidence limit shall be defined.NOTEIt is assumed that the difference between the initial and final test pressure is small compared with the pressuredifference
across the boundary in order to consider the flow rate constant and to apply the linear regressionExamples of application are given in annex A.7.6 Verification of leakage test accuracy (The procedure described applies only to high precision tests or to large
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