ASTM E499 E499M-11(2017) Standard Practice for Leaks Using the Mass Spectrometer Leak Detector in the Detector Probe Mode1 2.pdf

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1、Designation: E499/E499M 11 (Reapproved 2017)Standard Practice forLeaks Using the Mass Spectrometer Leak Detector in theDetector Probe Mode1,2This standard is issued under the fixed designation E499/E499M; the number immediately following the designation indicates the yearof original adoption or, in

2、the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.

3、1 This practice covers procedures for testing and locatingthe sources of gas leaking at the rate of 1 107Pa m3/s(1108Std cm3/s)3or greater. The test may be conducted onany device or component across which a pressure differentialof helium or other suitable tracer gas may be created, and onwhich the e

4、ffluent side of the leak to be tested is accessible forprobing with the mass spectrometer sampling probe.1.2 Two test methods are described:1.2.1 Test Method ADirect probing, and1.2.2 Test Method BAccumulation.1.3 UnitsThe values stated in either SI or std-cc/sec unitsare to be regarded separately a

5、s standard. The values stated ineach system may not be exact equivalents: therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This standard does not purport to address all of thesafety concerns, if an

6、y, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized

7、principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:4E1316 Terminology for Nonde

8、structive Examinations2.2 Other Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing5ANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel53. Terminology3.1 DefinitionsFor definitions of term

9、s used in thisstandard, see Terminology E1316, Section E.4. Summary of Practice4.1 Section 1.8 of the Leakage Testing Handbook6will be ofvalue to some users in determining which leak test method touse.4.2 The test methods covered in this practice require a leakdetector with a full-scale readout of a

10、t least 1 106Pa m3/s(1107Std cm3/s)3on the most sensitive range, a maximum1-min drift of zero and sensitivity of 65 % of full scale on thisrange, and 62 % or less on others (see 7.1). The abovesensitivities are those obtained by probing an actual standardleak in atmosphere with the detector, or samp

11、ling, probe, andnot the sensitivity of the detector to a standard leak attacheddirectly to the vacuum system.4.3 Test Method A, Direct Probing (see Fig. 1), is thesimplest test, and may be used in parts of any size, requiringonly that a tracer gas pressure be created across the area to betested, and

12、 the searching of the atmospheric side of the area bewith the detector probe. This test method detects leakage and1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.08 on LeakTesting Method.Current edition ap

13、proved June 1, 2017. Published July 2017. Originally approvedin 1973. Last previous edition approved in 2011 as E499 - 11. DOI: 10.1520/E0499_E0499M-11R17.2(Atmospheric pressure external, pressure above atmospheric internal). Thisdocument covers the Detector Probe Mode described in Guide E432.3The g

14、as temperature is referenced to 0C. To convert to another gas referencetemperature, Tref, multiply the leak rate by (Tref+ 273) 273.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inform

15、ation, refer to the standards Document Summary page onthe ASTM website.5Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.6Marr, J. William, “Leakage Testing Handbook,” prepared for Liquid PropulsionSectio

16、n, Jet Propulsion Laboratory, NationalAeronautics and SpaceAdministration,Pasadena, CA, Contract NAS 7-396, June 1961.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internat

17、ionally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1its source or sources. Experience has shown that le

18、ak testingdown to 1 105Pa m3/s (1 106Std cm3/s)3in factoryenvironments will usually be satisfactory if reasonable precau-tions against releasing gas like the tracer gas in the test area areobserved, and the effects of other interferences (Section 6) areconsidered.FIG. 1 Method AFIG. 2 Method BE499/E

19、499M 11 (2017)24.4 Test Method B, Accumulation Testing (see Fig. 2),provides for the testing of parts up to several cubic metres involume as in Fig. 2(a) or in portions of larger devices as in Fig.2(b). This is accomplished by allowing the leakage to accu-mulate in the chamber for a fixed period, wh

20、ile keeping it wellmixed with a fan, and then testing the internal atmosphere foran increase in tracer gas content with the detector probe. Thepractical sensitivity attainable with this method depends pri-marily on two things: first, on the volume between the chamberand the object; and second, on th

21、e amount of outgassing oftracer gas produced by the object. Thus, a part having consid-erable exposed rubber, plastic, blind cavities or threads cannotbe tested with the sensitivity of a smooth metallic part. Thetime in which a leak can be detected is directly proportional tothe leak rate and invers

22、ely proportional to the volume betweenthe chamber and the part. In theory, extremely small leaks canbe detected by this test method; however, the time required andthe effects of other interferences limit the practical sensitivityof this test method to about 1 107Pa m3/s (1 108Stdcm3/s)3for small par

23、ts.5. Personnel Qualification5.1 It is recommended that personnel performing leak test-ing attend a dedicated training course on the subject and passa written examination. The training course should be appropri-ate for NDT level II qualification according to RecommendedPractice No. SNT-TC-1A of the

24、American Society for Nonde-structive Testing or ANSI/ASNT Standard CP-189.6. Significance and Use6.1 Test Method A is frequently used to test large systemsand complex piping installations that can be filled with a tracegas. Helium is normally used. The test method is used to locateleaks but cannot b

25、e used to quantify except for approximation.Care must be taken to provide sufficient ventilation to preventincreasing the helium background at the test site. Results arelimited by the helium background and the percentage of theleaking trace gas captured by the probe.6.2 Test Method B is used to incr

26、ease the concentration oftrace gas coming through the leak by capturing it within anenclosure until the signal above the helium background can bedetected. By introducing a calibrated leak into the samevolume for a recorded time interval, leak rates can be mea-sured.7. Interferences,7.1 Atmospheric H

27、eliumThe atmosphere contains aboutfive parts per million (ppm) of helium, which is beingcontinuously drawn in by the detector probe. This backgroundmust be “zeroed out” before leak testing using helium canproceed. Successful leak testing is contingent on the ability ofthe detector to discriminate be

28、tween normal atmospherichelium, which is very constant, and an increase in helium dueto a leak. If the normally stable atmospheric helium level isincreased by release of helium in the test area, the referencelevel becomes unstable, and leak testing more difficult.7.2 Helium Outgassed from Absorbent

29、MaterialsHeliumabsorbed in various nonmetallic materials (such as rubber orplastics) may be released during the test. If the rate andmagnitude of the amount released approaches the amountreleased from the leak, the reliability of the test is decreased.The amount of such materials or their exposure t

30、o helium mustthen be reduced to obtain a meaningful test.7.3 Pressurizing with Test GasIn order to evaluate leakageaccurately, the test gas in all parts of the device must containsubstantially the same amount of tracer gas. When the devicecontains air prior to the introduction of test gas, or when a

31、ninert gas and a tracer gas are added separately, this may not betrue. Devices in which the effective diameter and length are notgreatly different (such as tanks) may be tested satisfactorily bysimply adding tracer gas. However, when long or restrictedsystems are to be tested, more uniform tracer di

32、stribution willbe obtained by first evacuating to less than 100 Pa (a few torr),and then filling with the test gas. The latter must be premixedif not 100 % tracer.7.4 Dirt and LiquidsAs the orifice in the detector probe isvery small, the parts being tested should be clean and dry toavoid plugging. R

33、eference should be frequently made to astandard leak to ascertain that this has not happened.8. Apparatus,8.1 Helium Leak Detector, equipped with atmospheric de-tector probe. To perform tests as specified in this standard, thedetector should be adjusted for testing with helium and shouldhave the fol

34、lowing minimum features:8.1.1 Sensor Mass Analyzer.8.1.2 Readout, analog or digital.8.1.3 Range (linear)A signal equivalent to 1 105Pam3/s (1 106Std cm3/s)3or larger must be detectable.8.1.4 Response time, 3 s or less.8.1.5 Stability of Zero and Sensitivity A maximum varia-tion of 65 % of full scale

35、 on the most sensitive range while theprobe is active; a maximum variation of 62 % of full scale onother ranges for a period of 1 min.NOTE 1Variations may be a function of environmental interferencesrather than equipment limitations.8.1.6 Controls:8.1.6.1 Range, preferable in scale steps of 10.8.1.6

36、.2 Zero, having sufficient range to null out atmospherichelium.8.2 Helium Leak StandardTo perform leak tests as speci-fied in this standard (system calibration), the leak standardshould meet the following minimum requirements:8.2.1 Ranges1102to1106Pa m3/s (103to 107Std cm3/s)3full scale calibrated f

37、or discharge to atmosphere.8.2.2 AdjustabilityAdjustable leak standards are a conve-nience but are not mandatory.8.2.3 Accuracy, 615 % of full-scale value or better.8.2.4 Temperature Coeffcient, shall be stated by manufac-turer.8.3 Helium Leak Standard, as in 8.2 but with ranges of1105Pa m3/s or 1 1

38、08Pa m3/s (106or 109Std cm3/s)full scale calibrated for discharge to vacuum shall be used forinstrument calibration.3E499/E499M 11 (2017)38.4 Other ApparatusFixtures or other equipment specificto one test method are listed under that test method.9. Material9.1 Test Gas Requirements:9.1.1 To be satis

39、factory, the test gas shall be nontoxic,nonflammable, not detrimental to common materials, andinexpensive. Helium, or helium mixed with air, nitrogen, orsome other suitable inert gas meets the requirements. If the testspecification allows leakage of 1 104Pa m3/s (1 105Stdcm3/s)3or more, or if large

40、vessels are to be tested, consider-ation should be given to diluting the tracer gas with another gassuch as dry air or nitrogen. This will avoid excessive heliuminput to the sensor and in the case of large vessels, save tracergas expense (Note 2).9.1.2 Producing Premixed Test GasIf the volume of the

41、device or the quantity to be tested is small, premixed gases canbe conveniently obtained in cylinders. The user can also mixgases by batch in the same way. Continuous mixing usingcalibrated orifices is another simple and convenient methodwhen the test pressure does not exceed 50 % of the tracer gasp

42、ressure available.NOTE 2When a vessel is not evacuated prior to adding test gas, thelatter is automatically diluted by one atmosphere of air.9.2 Liquid Nitrogen, or other means of cold trap refrigera-tion as specified by the maker of the leak detector.10. Calibration,10.1 The leak detectors used in

43、making leak tests by thesetest methods are not calibrated in the sense that they are takento the standards laboratory, calibrated, and then returned to thejob. Rather, the leak detector is used as a comparator betweena leak standard (8.2) (set to the specified leak size) which ispart of the instrume

44、ntation, and the unknown leak. However,the sensitivity of the leak detector is checked and adjusted onthe job so that a leak of specified size will give a readilyobservable, but not off-scale reading. More specific details aregiven in Section 11 under the test method being used. To verifysensitivity

45、, reference to the leak standard should be madebefore and after a prolonged test. When rapid repetitive testingof many items is required, refer to the leak standard oftenenough to ensure that desired test sensitivity is maintained.11. Procedure11.1 General Considerations:11.1.1 Test SpecificationsA

46、testing specification shall bein hand. This shall include:11.1.1.1 The gas pressure on the high side of the device tobe tested; also on the low side if it need differ from atmosphericpressure.11.1.1.2 The test gas composition, if there is need to specifyit.11.1.1.3 The maximum allowable leak rate in

47、 standard cubiccentimetres per second.11.1.1.4 Whether the leak rate is for each leak or for totalleakage of the device.11.1.1.5 If an “each leak” specification, whether or not otherthan seams, joints, and fittings needs to be tested.11.1.2 Safety FactorWhere feasible, it should be ascer-tained that

48、 a reasonable safety factor has been allowed betweenthe actual operational requirements of the device and themaximum specified for testing. Experience indicates that afactor of at least 10 should be used when possible. Forexample, if a maximum total leak rate for satisfactory opera-tion of a device

49、is 5 105Pa m3/s (5 106Std cm3/s)3, thetest requirement should be 5 106Pa m3/s (5 107Stdcm3/s)3or less.11.1.3 Test PressureThe device should be tested at orabove its operating pressure and with the pressure drop in thenormal direction, where practical. Precautions should be takenso that the device will not fail during pressurization, or that theoperator is protected from the consequences of a failure.11.1.4 Disposition or Recovery of Test GasTest gas shouldnever be dumped into the test area if furthe