1、Designation: E499/E499M 11Standard 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 the case of revis
2、ion, 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 specification has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This practice
3、covers procedures for testing and locatingthe sources of gas leaking at the rate of 1 3 107Pa m3/s(1 3 108Std 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 effluent sid
4、e 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 as standard.
5、 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 any, associat
6、ed 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.2. Referenced Documents2.1 ASTM Standards:4E1316 Terminology for Nondestructive Examinations2.2 Other Do
7、cuments: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 terms used in this stan-dard, see Term
8、inology 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 at least 1 3 106Pa m3/s(1 3 107St
9、d 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 sampling, probe, andnot the sen
10、sitivity 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 the searching of the atmos
11、pheric side of the area bewith the detector probe. This test method detects leakage andits source or sources. Experience has shown that leak testingdown to 1 3 105Pa m3/s (1 3 106Std cm3/s)3in factoryenvironments will usually be satisfactory if reasonable precau-tions against releasing gas like the
12、tracer gas in the test area areobserved, and the effects of other interferences (Section 6) areconsidered.4.4 Test Method B, Accumulation Testing (see Fig. 2),provides for the testing of parts up to several cubic metres in1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-struct
13、ive Testing and is the direct responsibility of Subcommittee E07.08 on LeakTesting Method.Current edition approved July 1, 2011. Published July 2011. Originally approvedin 1973. Last previous edition approved in 2006 as E499 - 95(2006). DOI:10.1520/E0499_E0499M-11.2(Atmospheric pressure external, pr
14、essure above atmospheric internal). Thisdocument covers the Detector Probe Mode described in Guide E432.3The gas 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, ww
15、w.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, 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 4322
16、8-0518, http:/www.asnt.org.6Marr, J. William, “Leakage Testing Handbook,” prepared for Liquid PropulsionSection, Jet Propulsion Laboratory, NationalAeronautics and SpaceAdministration,Pasadena, CA, Contract NAS 7-396, June 1961.1*A Summary of Changes section appears at the end of this standard.Copyr
17、ight ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.volume 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, while keeping it wellmix
18、ed 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 the amount of outgassing
19、 ofFIG. 1 Method AFIG. 2 Method BE499/E499M 112tracer 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 toth
20、e leak rate and inversely 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 3 107Pa m3/s (1 3
21、108Stdcm3/s)3for small parts.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 RecommendedPrac
22、tice No. SNT-TC-1A of the 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 t
23、o locateleaks but cannot be 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 Tes
24、t Method B is used to increase 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. Inter
25、ferences7.1 Atmospheric HeliumThe 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 de
26、tector to discriminate between 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
27、Outgassed from Absorbent 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 mate
28、rials or their exposure to helium mustthen be reduced to obtain a meaningful test.7.3 Pressurizing with Test GasIn order to evaluate leak-age accurately, the test gas in all parts of the device mustcontain substantially the same amount of tracer gas. When thedevice contains air prior to the introduc
29、tion of test gas, or whenan inert gas and a tracer gas are added separately, this may notbe true. Devices in which the effective diameter and length arenot greatly different (such as tanks) may be tested satisfactorilyby simply adding tracer gas. However, when long or restrictedsystems are to be tes
30、ted, more uniform tracer distribution 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
31、and dry toavoid plugging. Reference should be frequently made to astandard leak to ascertain that this has not happened.8. Apparatus8.1 Helium Leak Detector, equipped with atmospheric de-tector probe. To perform tests as specified in this standard, thedetector should be adjusted for testing with hel
32、ium and shouldhave the following 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 3 105Pam3/s (1 3 106Std cm3/s)3or larger must be detectable.8.1.4 Response time,3sorless.8.1.5 Stability of Zero and Sensitivity A maximum varia-
33、tion of 65 % of full scale 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
34、in scale steps of 103.8.1.6.2 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 Ranges1 3 102to 1 3 106Pa m3/s (103to 107
35、Std cm3/s)3full scale calibrated for 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,asin8.2 but w
36、ith ranges of1 3 105Pa m3/s or 1 3 108Pa m3/s (106or 109Std cm3/s)full scale calibrated for discharge to vacuum shall be used forinstrument calibration.38.4 Other ApparatusFixtures or other equipment specificto one test method are listed under that test method.9. Material9.1 Test Gas Requirements:9.
37、1.1 To be satisfactory, 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 3 104Pa m3/s (1 3 105Stdcm3/s)3or
38、 more, or if large vessels are to be tested, consider-ation should be given to diluting the tracer gas with another gasE499/E499M 113such 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 Prem
39、ixed Test GasIf the volume of thedevice 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 n
40、ot exceed 50 % of the tracer gaspressure 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
41、10.1 The leak detectors used in 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 si
42、ze) which ispart of the instrumentation, 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
43、being used. To verifysensitivity, 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 Considerati
44、ons:11.1.1 Test SpecificationsA 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 Th
45、e maximum allowable leak rate in 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
46、, it should be ascer-tained that 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 sati
47、sfactory opera-tion of a device is 5 3 105Pa m3/s (5 3 106Std cm3/s)3, thetest requirement should be 5 3 106Pa m3/s (5 3 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. Precauti
48、ons 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 gasshould never be dumped into the test area if further testing isplanned. It should be vented outdoors or rec
49、overed for reuse ifthe volume to be used makes this worthwhile.11.1.5 Detrimental Effects of Helium Tracer GasThis gasis quite inert, and seldom causes any problems with mostmaterials, particularly when used in gaseous form for leaktesting and then removed. When there is a question as to thecompatibility of the tracer with a particular material, anauthority on the latter should be consulted. This is particularlytrue when helium is sealed in contact with glass or otherbarriers that it may permeate.11.1.6 Correlation of Test Gas Leakage
