1、DEUTSCHE NORM June 1998 Non-destructive testing Leak test i ng EN 1518 Characterization of mass spectrometer leak detectors English version of DIN EN 1518 ICs 19.100 Descriptors: Non-destructive testing, leak testing. Zerstrungsfreie Prfung - Dichtheitsprfung - Charakterisierung von massenspektromet
2、rischen Leckdetektoren European Standard EN 1518: 1998 has the status of a DIN Standard. A comma is used as the decimal marker. National foreword This standard has been prepared by CEN/TC 138. The responsible German body involved in its preparation was the Normenausschu Materialprfung (Mate- rials T
3、esting Standards Committee), Technical Committee Dichtheitsprfung. EN comprises 24 pages. No pari of this standard may be reproduced without the prior permission of Ref. No. DIN EN 1518 : 1998-0 V Deutsches Institut fr Nonung e. V., Berlin. Luth Verlag GmbH, D-10772 Berlin, has the exclusive right o
4、f sale for German Standards (DIN-Normen). . English price group 10 Sales No . . 1110 12.98 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 1518 April 1998 ICs 19.100 Descriptors: Non-destructive testing, leak testing. English version Non-destructive testing Characterization of mass spectrometer
5、 leak detectors Leak test i ng Essais non destructifs - Contrles dtanchit - Caractrisation des dtecteurs de fuite spectromtrie de masse Leckdetektoren Zerstrungsfreie Prfung - Dichtheitsprfung - Charakterisierung von massenspektrometrischen This European Standard was approved by CEN on 1998-03-25. C
6、EN members are bound to comply with the CENKENELEC 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 stand- ards may be obtained on a
7、pplication to the Central Secretariat or to any CEN member. The European Standards exist 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 ha
8、s the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom. CE
9、N European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, 8-1050 Brussels O 1998. CEN - All rights of exploitation in any form and by any means reserved worldwide for CEN national members. Ref. No. EN 1518 : 1998 E
10、 Page 2 EN 1518 : 1998 Contents Foreword 1 Scope 2 Normative references 3 Definitions 4 Description of a MSLD 5 Apparatus for methods of characterization 6 Reference conditions for characterization 7 Test procedures 8 Results 9 Test report Page 2 3 3 3 6 9 11 11 16 21 Foreword This European Standard
11、 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 national standard, either by publication of an identical text or by endorsement, at the latest by October 1998, and conflic
12、ting national standards shall be withdrawn at the latest by October 1998. According to the CENICENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germ
13、any, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Page 3 EN 1518: 1998 1 Scope This European Standard specifies terms and procedures for the characterization of mass spectrometer leak detectors (MSLD). It is not intend
14、ed to give a complete set of specifications for an acceptance test but a description of procedures that can be used without particular calibration equipment. An MSLD has an integral high vacuum system for maintaining the sensing element (mass spectrometer) at low operating pressure and for establish
15、ing a partial pressure related to the incoming gas flow. This pressure is measured quantitatively by the mass spectrometer. Such instruments are able to selectively measure the flow of a tracer gas. In most cases the tracer gas will be helium, flowing idout of an object through a leak. The methods d
16、escribed in this standard are applicable without restictions to helium as the tracer gas. For other gases, additional precautions may be necessary. These methods are applicable to commonly-available MSLD, based on the present level of technology, which may be able to measure leak rates down to 1 O-*
17、 Pa.m3/s. 2 Normative references This European 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 amendments to
18、 or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. prEN 1330-8 Non-destructive testing - Terminology Pari 8: Terms used in testing for leak
19、 tightness 3 Definitions For the purposes of this standard, the definitions given in prEN 1330-8 apply together with the following: 3.1 Terms 3.1.1 compression ratio of the counterflow stages of the high vacuum pump for tracer gas: With zero flow, the ratio of partial pressure of tracer gas at the e
20、xhaust of the counterflow stages of the high vacuum pump to the partial pressure at the inlet of the mass spectrometer (M S ) . Page 4 EN 1518: 1998 3.1.2 display: A device which indicates visually the leakage rate measured. The units in which the leakage rate is expressed may be selectable. NOTE: T
21、he display may be analog or quasi-analog (continuous scale with definite divisions) or digital (numbers with a definite number of digits) or a combination of both. 3.1.3 inlet pumping speed: The volume rate of flow at the test port of a MSLD when the instrument is operating with the MS below its max
22、imum working pressure. NOTE: The inlet pumping speed may be different for different gases and different modes of operation. The inlet pumping speed for the tracer gas determines the response time for the volume under test. 3.1.4 internal leak port: A flange directly behind the inlet valve, used to c
23、onnect a small leak for zero drift determination. 3.1.5 intrinsic pumping speed: In a direct flow leak detector, the volume rate of flow of tracer gas at the inlet of the MS. 3.1.6 ion collector: The part of the MS where ions are collected and neutralized producing a current in the collector which i
24、s a measure of the number of neutralized ions. 3.1.7 sensitivity control: An electrical hardware or software control which may be used to adjust the sensitivity of the instrument so that a calibrated leak is indicated with its true leakage rate. 3.1.8 sensitivity of the MS: The ratio of the ion curr
25、ent at the output of the MS to the corresponding partial pressure of tracer gas inside the MS. 3.1.9 zero control: An electrical hardware or software control which may be used to shift the output indication of the leak detector, to a determined point of the scale range in use, usually zero. 3.2 Term
26、s related to the operation of the MSLD 3.2.1 peak (noun): The trace showing a maximum on the chart recorder when the leak detector is scanned with respect to mass with gas present, usually the tracer gas, to which the detector is tuned. 3.2.2 peak (verb): To set the scanning control (see 3.2.3) of a
27、 leak detector so that the output due to a given tracer gas input is maximized. It is a form of tuning (see 3.2.4). Page 5 EN 1518: 1998 3.2.3 scan (verb): To adjust the accelerating voltage (or other equivalent operating parameter) of a leak detector, particularly across that range of voltage which
28、 includes the voltage necessary to produce a tracer gas peak. 3.2.4 tune (verb): In leak detection, to adjust one or more of the controls of a leak detector so that its response to a tracer gas is maximized. Tuning by means of the scanning control only is called “peaking“ (see 3.2.2). 3.3 Terms rela
29、ted to the specification of the MSLD 3.3.1 Operating conditions 3.3.1.1 General For the definition of operating conditions see prEN 1330-8. NOTE: The operating conditions are normally given by the manufacturer. 3.3.1.2 optimum working pressure: The pressure in the MS, at which the minimum detectable
30、 concentration can be measured. 3.3.1.3 maximum working pressure: The pressure in the MS above which normal operation is no longer possible. 3.3.1.4 maximum inlet pressure: The maximum pressure at the test port at which the MSLD is able to detect leaks in a given mode of operation. NOTE: For a MSLD
31、to be connected directly to a system under test, the total pressure in the system has to be less than the maximum inlet pressure of the MSLD. 3.3.1.5 maximum gas load: The maximum pV-throughput of all gases emerging from the test specimen that the MSLD can pump during leak detection in a given mode
32、of operation. NOTE: For component testing, the MSLD is normally ready for measurement when the desorption of water vapour from the inner surfaces is less than the maximum gas load. 3.3.2 Tracer gas background signal 3.3.2.1 background signal drift: The relatively slow change in background signal, gi
33、ven by the maximum change in a given period of time. 3.3.2.2 background signal noise: The relatively rapid change in background signal given by an average measure of scatter in a specified period of time. Page 6 EN 1518 : 1998 3.3.3 Detection limit 3.3.3.1 minimum detectable concentration ratio: The
34、 smallest concentration of a given tracer gas in an air mixture that can be detected unambiguously when the mixture is fed into the MSLD at such a rate as that is at its optimum working pressure. 3.3.4 resolving power: The ratio of a given mass number to the peak width measured at a specified (for e
35、xample 1 O %) height of the peak (in units of mass numbers). 3.3.5 Display resolution 3.3.5.1 general: A quantitative expression of the ability of the leakage rate-display device to distinguish meaningfully between closely adjacent values of the leakage rate indicated. 3.3.5.2 linear display resolut
36、ion: The constant difference between adjacent scale intervals expressed in % full scale indication. 3.3.5.3 logarithmic display resolution: The constant ratio between two adjacent scale intervals expressed as a percentage of the indicated value. 4 Description of a MSLD 4.1 Main parts of a MSLD A MSL
37、D (see definition given prEN 1330-8) consists basically of a mass spectrometer and a high vacuum pumping system for: - maintaining the MS under appropriate vacuum conditions; - producing a definite partial pressure of tracer gas when a specific throughput of tracer gas enters the leak detector. A MS
38、LD includes also a number of valves and pressure gauges to ensure the appropriate vacuum conditions within the system. The leakrate output can be displayed in a number of ways, for example an electrical meter, or digital displays of different types. In addition, a chart recorder output is usually av
39、ailable, which has to be used for the test procedures in this standard. Page 7 EN 1518: 1998 The general structure of an MSLD is described by the following list. a) Mass spectrometer: - ion source; - separation system; - ion collector. b) Pumping system: - inlet system; - inlet line; - inlet valve;
40、- pump valve; - test port; - vent valve; - internal leak port. c) Sensitivity zero control. d) Display. 4.2 Operating principles of MSLD 4.2.1 Direct flo w leak detectors The leakage rate qx is given by the equation: qx =px x sx where qx is the pV-throughput of tracer gas; Sx is the intrinsic pumpin
41、g speed; px is the partial pressure of tracer gas in the mass spectrometer (MS). Page 8 EN 1518 : 1998 4.2.2 Counterflow leak detectors The leakrate qx is given by the equation: where qx is the pV-throughput of tracer gas; K, is the compression ratio of the counterflow stages of the high vacuum pump
42、 for tracer gas (see 3.1.1); sb,x is the speed of the pumping system, for tracer gas, backing the counterflow stages of the high vacuum pump; px is the partial pressure of tracer gas in the MS. 4.3 MLSD specification The MLSD specification is described by the following list: a) Operating conditions:
43、 - optimum working pressure; - maximum working pressure; - maximum inlet pressure; - maximum gas load. b) Tracer gas background signal: - background signal drift; - background signal noise. c) Non linearity. d) Detection limit: - minimum detectable leakage rate; - minimum detectable concentration ra
44、tio. e) Resolving power. f) Display discrimination. Page 9 EN 1518: 1998 5 Apparatus for methods of characterization 5.1 Leaks For the following tests, two known leaks are required: - a small tracer gas leak for the test of minimum detectable leakage rate; - a large air leak for the determination of
45、 minimum detectable concentration. Both leaks have to have a specified temperature correction. For MSLD using the working principles indicated by 4.2.1 and 4.2.2, depending on measurement range, more than two leaks may be necessary for determination of detection limits and sensitivity according to t
46、he working principle. 5.1.1 Small tracer gas leaks The small known leaks shall be of a size such that the total pressure in the MS is negligibly increased. For the determination of sensitivity drift, the leak should produce a deflection which is not less than 50 times the smallest detectable signal.
47、 For drift measurements, as these leaks are usually of the permeation type and have an appreciable temperature coefficient, ambient temperature variation should also be taken into account. Should it be necessary to have a small known leak for the determination of background signal drift (see 7.2.1 )
48、, this leak has to be small enough to give a signal in the lowest decade of signal output. 5.1.2 Large air leak The large known leak shall be of such a size that, when ambient air is at its entrance and partial flow conditions do not apply, the pressure in the MSLD rises to the optimum working press
49、ure. Such a large leak can be obtained using a fine leak valve of high specification. 5.2 Leak isolation valve (see prEN 1330-8) (Refer to prEN 1330-8). Page 1 O EN 1518: 1998 5.3 Test vessel A test vessel is used for the determination of the inlet pumping speed of the MSLD. It is a vacuum chamber of known volume, preferably cylindrical or spherical, typically 1 O I. For connection to the MSLD, the test vessel shall have a flange of suitable diameter (not less than the diameter of the test port of the MSLD) and a second flange for the connection of a calibrated l
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