BS EN 1779-1999 Non-destructive testing - Leak testing - Criteria for method and technique selection《无损检验 漏泄试验 方法和技术选择标准》.pdf

1、BRITISH STANDARD BS EN 1779:1999 Incorporating Amendment No. 1 Non-destructive testing Leak testing Criteria for method and technique selection The European Standard EN 1779:1999, with the incorporation of amendment A1:2003, has the status of a British Standard ICS 19.100 BS EN 1779:1999 This Britis

2、h Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 November 1999 BSI 10 February 2004 ISBN 0 580 32931 3 National foreword This British Standard is the English language ver

3、sion of EN 1779:1999, including amendment A1:2003. The UK participation in its preparation was entrusted to Technical Committee WEE/46, Non-destructive testing, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-r

4、eferences The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of Bri

5、tish Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; prese

6、nt to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front co

7、ver, the EN title page, pages 2 to 18, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments 14968 10 February 2004 Revision to Foreword page and deletion of A

8、nnex ZAEUROPEAN STANDARD EN 1779 August 1999 NORME EUROPENNE + A1 December 2003 EUROPISCHE NORM ICS 91.040.70 English version Non-destructive testing - Leak testing - Criteria for method and technique selection (includes amendment A1:2003) Essais non destructifs - Contrles dtanchit - Critres de choi

9、x de la mthode et de la technique (inclut lamendement A1:2003) Zerstrungsfreie Prfung Dichtheitsprfung - Kriterien zur Auswahl eines Prfverfahrens (enthlt nderung A1:2003) This European Standard was approved by CEN on 10 July 1999, and amendment A1 was approved by CEN on 20 November 2003. CEN member

10、s 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

11、 to the Central Secretariat 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 Central Secretariat has the sam

12、e status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom

13、. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1999 All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1779:1999 + A1:200

14、3 E Page 2 EN 1779:1999 Contents Page Foreword 3 1 Scope 4 2 Normative references 4 3 Definitions 4 4 Personnel qualification 4 5 Units 4 6 Tightness requirements 4 7 Leak testing 5 8 General principles of method and technique selection 9 Annex A (normative) Specific features of leak testing methods

15、 12 Annex B (informative) Conversion factors for leakage rate units 18 Page 3 EN 1779:1999 Foreword This European Standard has been prepared by 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 na

16、tional standard, either by publication of an identical text or by endorsement, at the latest by February 2000, and conflicting national standards shall be withdrawn at the latest by February 2000. This document has been prepared under a mandate given to CEN by the European Commission and the Europea

17、n Free Trade Association. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg

18、, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Foreword to amendment A1 This document EN 1779:1999/A1:2003 has been prepared by Technical Committee CEN/TC 138 “Non-destructive testing”, the secretariat of which is held by AFNOR. This Amendment to the European Sta

19、ndard EN 1779:1999 shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2004, and conflicting national standards shall be withdrawn at the latest by June 2004. This document has been prepared under a mandate given to CE

20、N by the European Commission and the European Free Trade Association. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany,

21、 Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Page 4 EN 1779:1999 1 Scope This European Standard describes criteria for the selection of the most suitable method and technique for the assessme

22、nt of leak tightness by indication or measurement of a gas leakage. Annex A, normative, allows a comparison of standard test methods. Leak detection using hydrostatic tests, ultrasonic or electromagnetic methods is not included in this document. This standard can be used for equipment which can be e

23、vacuated or pressurized. 2 Normative references This standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendme

24、nts to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references the latest edition of the reference applies. EN 473 Qualification and certification of NDT personnel - General principles EN 1330-8 Non-destructive te

25、sting - Terminology - Part 8: Terms used in leak tightness testing 3 Definitions For the purposes of this standard, the definitions given in EN 1330-8 apply. 4 Personnel qualification It is assumed that leak testing is performed by qualified and capable personnel. In order to prove this qualificatio

26、n, it is recommended to certify the personnel in accordance with EN 473. 5 Units The leakage rate is defined as the pV-throughput of a specific fluid which passes through a leak under specific conditions and is expressed in Pascals cubic metre per second. In the past, the leakage rate was expressed

27、in various units, these are given in informative Annex B. 6 Tightness requirements The leak tightness of an object is usually determined by measurement of its gas leakage rate. Leak tightness is commonly described as the flow rate of fluid into or from the test object. For a gas, leak tightness may

28、be conveniently indicated by the variation of pressure with time under specified conditions. For testing, however, i.e. when drafting specifications and procedures, the leak tightness shall be expressed as leakage rate in units of gas throughput (Pa m 3 /s) for a specific gas at specified temperatur

29、e and at specified pressure conditions. Zero leakage rate shall not be specified. The required leak tightness shall be related to the function of the object under consideration. Page 5 EN 1779:1999 NOTE 1: Examples of relationship between leakage rate and the object: - leakage rates in the order of

30、5 x 10 -4Pa m 3 /s can be acceptable for compressed air cylinders (this corresponds to a pressure variation of 5000 Pa in a 10 l volume in 24 hours or 0,5 l loss measured at atmospheric pressure); - a leakage rate of 10 -10Pa m 3 /s is typical for cardiac pacemakers (this corresponds to a loss of 1

31、cm 3every 30 years approximately). The total tightness of a system can be considered in terms of tightness for all components of that system. To meet requirements the sum of the leakage rates for each component plus the sum of the leakage rates at each connecting point shall be less than the overall

32、 allowable leakage rate of the system. The tightness of component or system shall be specified under normal operating conditions. NOTE 2 : The following factors have the most significant influence on tightness: - the nature and pressure of the gas; - the operating temperature. The suitability of the

33、 system for a given task is indicated by the functional tightness. NOTE 3 : To take into account factors that are unquantifiable, it may be advisable to adopt leak tightness values lower than this by a factor from three to ten. 7 Leak testing The actual gas flow through the leaks of the test object,

34、 which has been determined in a leak test, shall be converted to the leakage rate with that under operating conditions. The following considerations shall be applied to all methods by which leakage rates are determined. A review of the methods and techniques is given in table 1. Page 6 EN 1779:1999

35、Table 1: Leak testing - Criteria for method and technique selection Flow direction Extent of test Applicability Techniques location B.1, B.2.2, B.4, C.3 gas flow out local area measurement B.2.1, B.3, D.3 of object location C.1, C.2 total area measurement B.3, B.5, D.1, C.1, B.6, D.3, D.4 location A

36、.3 gas flow local area into measurement A.2, D.3 object location total area measurement A.1, D.2, D.3, D.4 Utilization of the table: 1) choose the appropriate flow direction for test; 2) define the extent of the investigation: total or local area; 3) define the aim of test: location or measurement;

37、4) choose the appropriate method (A to D, from the normative Annex A); 5) check any practical difficulties associated with the test. NOTE: Some techniques used for location can also give an estimate of the leakage size, but they are not allowed to demonstrate the compliance with the specifications.

38、7.1 Techniques for leak location and techniques for measurement It is usually not possible to establish in one step the total leakage of a component (or a system) and the location of the leaks. Two techniques shall, therefore, be considered: measurement of the overall leakage rate or location of lea

39、ks for possible elimination. Examples of total (or integral) techniques include the measurement of the pressure variation with time within the object and the accumulation of gas escaping from the object over a period of time. One technique for leak location involves probing the object with a suitabl

40、e tracer gas or sniffing the surface of an object filled with tracer gas. NOTE: In the selection of an appropriate technique for leak assessment, the conditions of the test (pressure, vacuum, type of gas, etc.) should be carefully considered. Some guidance is given in clause 8. 7.2 Time dependence (

41、in tracer gas techniques) The measuring device shall be placed on the opposite side of the boundary to that probed with tracer gas. The tracer gas can be detected only when it has crossed the boundary. Time shall be allowed, therefore, for stabilization. The time taken by the gas to cross the bounda

42、ry depends on the nature of gas, the pressure difference and the geometry of the leak path. It also depends on the temperature, the cleanliness of the object, etc. NOTE: Small leaks can require a long stabilization time. If the flow through the leak is impeded by successive obstacles, such as multip

43、le seals or double weld beads, the test time can be very long. Page 7 EN 1779:1999 7.3 Influence of flow conditions The usual laws governing gas flow shall be used to calculate variation in leakage rate, as a function of pressure, temperature and type of gas. NOTE: In quantitative leak detection two

44、 different flow regimes are normally considered. These are the regimes of viscous laminar or molecular flow. The boundaries between these regimes are not precisely defined. Care shall be taken therefore in the selection of any of the formulas given in 7.3.1, 7.3.2 and 7.3.3. For practical purposes i

45、t is generally accepted that for helium leakage rates less than or equal 10 -7Pam 3 /s, conditions for molecular flow apply. For helium leakage rates greater than 10 -5Pam 3 /s, conditions for viscous laminar flow apply in the case of a single capillary leak. For the different flow regimes the depen

46、dence of leakage rate on pressure, temperature and type of gas is different. 7.3.1 Influence of pressure For a given leak, the dimensions of which are unchanged by the applied pressure, the following expressions shall be used to take into account the effect of pressure change on flow rate: - Molecul

47、ar flow p pq = q 1 2 1 2 with pressure differences p - p = p A B 2 2 2 p - p = p A B 1 1 1 - Viscous laminar flow p pp pq = ) p- p ( ) p- p (q = q 2 1 2 1 2 1 A 2 B 2 A 2 B 1 2 1 1 2 2 with pressure averages 2 A B 1 1 1 ) p p (= p +2 A B 2 2 2 ) p p (= p +Figure 1: Leak Page 8 EN 1779:1999 where p A

48、1and p A 2are different downstream pressures in Pascals; p B 1and p B 2are different upstream pressures in Pascals; q 1and q 2are the leakage rates in Pa m 3 /s associated with the two pressure differences. 7.3.2 Influence of temperature For a given leak, the dimensions of which are not altered by t

49、he temperature change, the following expressions shall be used to take into account the effect of temperature on flow rate: - Molecular flow T Tq = q T T 1 2 1 2 - Viscous laminar flow T T T Tq = q 2 1 1 2 or approximately T Tq = q T T 2 1 1 2 where T 1and T 2are the different temperatures, in Kelvins; q T 2and q T 1are the leakage rates in Pa m 3 /s associated with T 2and T 1 ; T 2and T 1are the different dynamic visocities in Pa s associated with T 1 and