ASTM E2024-2005 Standard Test Methods for Atmospheric Leaks Using a Thermal Conductivity Leak Detector《用导热泄漏探测器测定大气泄漏的标准试验方法》.pdf

1、Designation: E 2024 05Standard Test Methods forAtmospheric Leaks Using a Thermal Conductivity LeakDetector1This standard is issued under the fixed designation E 2024; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover procedures for detecting thesources of gas leaking at the rate of 4.5 3 109mol/s (1 3 104standar

3、d cm3/s) or greater. The tests may be conducted on anyobject that can be pressurized with a tracer gas that isdetectable by a thermal conductivity detector. The test sensi-tivity will vary widely depending on the tracer gas used.1.2 This standard does not purport to address all of thesafety concerns

4、, if any, 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.2. Referenced Documents2.1 ASTM Standards:2E 543 Practice for Agencies Performing Nond

5、estructiveTestingE 1316 Terminology for Nondestructive Testing2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive TestingANSI/ASNT CP-189 Standard for Qualification and Certi-fication of Nondestructive Testing Personnel2.3 AIA Standard:

6、NAS-410 Certification and Qualification of NondestructiveTest Personnel43. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods, see Terminology E 1316, Section E.4. Summary of Test Method4.1 Scanning MethodThis test method sets minimumrequirements for a thermal conductivity

7、leak detector. Itprovides for calibration of the detector and gives proceduresfor pressurizing the test object, locating leaks and estimatingthe leakage rate.4.2 Accumulation MethodThe accumulation method issometimes the only practical method for accessing complexshaped flanges or sections of pressu

8、rized vessels to be leaktested. It may be achieved by entrapping or enclosing an areaof a test component with a suitable covering and sampling thebuildup of tracer gas concentration with the thermal conduc-tivity leak detector. The acceptance criteria is based on thetracer gas concentration detected

9、 by the thermal conductivitydetector after an accumulation time from leakage from theleak(s) into the known sample volume.5. Significance and Use5.1 These test methods are useful for locating and estimat-ing the size of pressurized gas leaks, either as quality controltests or as field inspection pro

10、cedures. Also, they are valuableas pretests before other more time consuming and moresensitive leak tests are employed. These test methods aresemi-quantitative techniques used to locate leaks but cannot beused to quantify except for approximation. These test methodsmay be used in an accept-reject te

11、st mode.6. Basis of Application6.1 The following items are subject to contractual agree-ment between the parties using or referencing these testmethods:6.2 Personnel Qualification6.2.1 If specified in the contractual agreement. Personnelperforming examinations to these test methods shall be quali-fi

12、ed in accordance with a nationally or internationally recog-nized NDT personnel qualification practice or standard such asANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or similar docu-ment and certified by the employer or certifying agency, asapplicable. The practice or standard used and its applicablerevis

13、ion shall be identified in the contractual agreement.1These test methods are under the jurisdiction of ASTM Committee E07 onNondestructive Testing and are the direct responsibility of Subcommittee E07.08 onLeak Testing Method.Current edition approved Dec. 1, 2005. Published December 2005. Originally

14、approved in 1999. Last previous edition approved in 1999 as E 2024 - 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AS

15、TM website.3Available from the American Society for Nondestructive Testing, 1711 Arlin-gate Plaza, P.O. Box 28518, Columbus, OH 432280518.4Available from the Aerospace Industries Association of America, Inc., 1250Eye Street, N.W., Washington, DC 20005.1Copyright ASTM International, 100 Barr Harbor D

16、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E 543. The applicableedition of Practice E 543 shall be specified in the cont

17、ractualagreement.6.4 Re-examination of Repaired/Reworked ItemsRe-examination of repaired/reworked items is not addressed inthese test methods, they shall be specified in the contractualagreement7. Interferences7.1 Background GasesThermal conductivity detectors aresensitive to all gases that have a t

18、hermal conductivity valuedifferent from air and their sensitivity changes with the degreeof difference. Background gases in the test area may signifi-cantly alter the test sensitivity to a particular tracer gas.7.2 Cleanliness of Test SurfaceThe areas to be tested mustbe free of oil, grease, paint,

19、water, and other contaminants thatmight mask a leak or be drawn into the leak detector and clogthe probe.7.3 Pressurizing with Test GasIn order to evaluate leak-age accurately, the test gas in all parts of the device or systemmust contain substantially the same concentration of tracer gas.When the d

20、evice contains air prior to the introduction of testgas, or when an inert gas and a tracer gas are added separately,this may not be true. Devices in which the effective diameterand length are not greatly different, such as tanks, may betested satisfactorily by simply adding tracer gas; however,when

21、long or restricted systems (piping) are to be tested, moreuniform tracer gas distribution will be obtained by firstevacuating to less than 100 Pa (.75 torr), and then filling withthe tracer gas or by employing proper purge technique.7.4 Unknown Tracer Gas ConcentrationWhen perform-ing the calibratio

22、n of the leak detector, a capillary standard leakgenerally is used that contains 100 % concentration of thetracer gas. Leak testing often is done on devices or systems thatdo not contain this same gas concentration as the standard leak.Doing so will cause the test sensitivity (detector response) to

23、beless than that from the standard leak.7.5 Operator Scanning VariationsThe leak detector re-sponse will change when the test operator varies the scanningparameters because the scanning distance and speed deter-mines the tracer gas concentration that the leak detectormeasured. Any change in scanning

24、 parameters from those usedfor calibration may cause a reduction in test sensitivity andinstrument response.7.6 Gas CompatibilitySome gases, such as hydrogen andammonia, may permanently alter the instrument sensitivity andstability. Refer to the instrument manufacturers manual.8. Apparatus8.1 Therma

25、l Conductivity Leak DetectorThis detectorshould have a minimum detectable leak rate of 4.5 3 109mol/s (1 3 104Std cm3/s). To perform tests as specified inthese test methods, the detector should have the followingminimum features:8.1.1 Thermal conductivity sensor.8.1.2 Device to maintain a stable pro

26、be air velocity.8.1.3 Controls to zero detector.8.1.4 Battery status indicator for portable instruments. Theinstrument sensitivity for a portable detector shall not varyprior to a low battery indication.8.2 Standard Leaks of Both Fixed and Variable TypeTheleak rate of the standard leak used for the

27、system calibrationshall be equal to the acceptance level (maximum permissibleleakage rate). The leak rate of the standard leak may be lessthan the acceptance level when the system tracer concentrationis less than 100 % for testing.8.3 Test Component/System Enclosure, either a rigid struc-ture or hea

28、vy plastic cover, to contain partially or totallysurround the test part with tracer gas. The enclosure must notrestrict flow to the leak detector.9. Calibration of Leak Detector9.1 The detector shall be turned on and allowed to warm upand zeroed as specified by the manufacturer. The probe(sensor) th

29、en shall be moved across the standard leak at adistance of not more than 1 mm 0.04 in. from the standardleak orifice and moved not faster than 20 mm/s 0.8 in./s, andthe detectors response observed. The standard shall bescanned several times and the average indicated leakage rate isthe test acceptanc

30、e reading. The scanning speed and distancemay have to be adjusted during calibration to improve thedetector response. These scanning parameters established dur-ing calibration shall not be exceeded while scanning the testsystem.9.2 The capsule leak should be stored with the shutoff valve,if present,

31、 closed, and the leak should be allowed to stabilizefor approximately 5 min after opening.9.3 Calibration shall be performed prior to, upon comple-tion of, and during testing at intervals not to exceed 1 h. Failureof a calibration check to obtain the same or greater response asthe previous check sha

32、ll require that an evaluation or retest ofall tested parts or areas examined be performed.9.4 For the accumulation method, the thermal conductivitydetector needs to be checked against a known standardconcentration of the tracer gas in air into the test volume duringthe accumulation time. For volumes

33、 different from the testvolume, a proportional adjustment shall be made.10. Procedure10.1 Evacuate the device or test system to remove air andpressurize with tracer gas to the specification test pressure.When the test system cannot be evacuated, either the systemmust be purged sufficiently with the

34、tracer gas or the tracer gasconcentration calculated. When testing is performed with atracer gas concentration less than 100 %, then the output shallbe scaled appropriately to correct the instrument response.10.2 Calibrate the leak detector in accordance with 9.1. Thiscalibration shall be performed

35、in the test area to allow theprobe to sample the background gases.10.3 Probe Areas Suspected of LeakingThe thermal con-ductivity sensor shall be held not more than 1 mm 0.04 in.from the test surface and moved not faster than 20 mm/s 0.8in./s. The gases, scanning rate, and distance shall be equal tot

36、hat used in the calibration performed in 9.1. Any detectorresponse shall be verified by moving the probe away from thearea and then rescanning the area. Any verified response lessE2024052than the instrument response established from sampling theleak standard in accordance with 9.1 is acceptable, and

37、 leakagereadings equal to or greater than that instrument response isunacceptable.10.4 When surface scanning is hindered by adverse atmo-spheric or testing conditions, such as wind, drafts, or wetsurfaces, an enclosure may be used to protect and accumulatethe tracer gas. An exact quantitative measur

38、ement under theseconditions usually is not possible.10.5 Check calibration as specified in 9.1.11. Precision and Bias11.1 PrecisionThe uncertainties in these test methods thatare measured statistically, are referred to as Type A uncertain-ties. These uncertainties can be evaluated by making repeated

39、measurements. Typically, these values may be no better than20 % of the leak rate. These uncertainties will be affected bythe following:11.1.1 The ability of the test technician to duplicate the testprocedure (scanning rate, calibration, etc.);11.1.2 The variability in interferences caused by air cur

40、rentsand the local air composition; and,11.1.3 The stability of the sensing instrument.11.2 BiasThe uncertainties in these test methods that areevaluated by nonstatistical means, are referred to as Type Buncertainties. The bias uncertainties will be composed of theuncertainties in the calibrated lea

41、k used for the instrumentcalibration, the uncertainties associated with the readability ofthe instrument, the test uncertainties concerned with theassumptions of the tracer gas concentration, uniformity, andeffects due to test conditions including blockage of leaks withcondensable gases or particles

42、 and air currents within thetesting environments. Estimates of the bias uncertaintiesshould be made at the time of testing.12. Keywords12.1 conductivity leak test; leak testing; sensitive leak test;thermal conductivity leak testASTM International takes no position respecting the validity of any pate

43、nt rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision

44、at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comme

45、nts will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted

46、 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E2024053