1、Designation: E2930 13Standard Practice forPressure Decay Leak Test Method1This standard is issued under the fixed designation E2930; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses
2、 indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a method for determining theleakage rate of a vessel subject to a positive pressure differ-ence. The technique is based upon evaluat
3、ion of the change ofmass within the test object based on a pressure decay measure-ment. The pressure decay measurement uses the ideal gasequation of state and the measured pressures, temperatures, andtime to determine the mass loss from the vessel. This methoddoes not apply to deformable vessels.1.2
4、 This standard does not purport to address all of thesafety concerns, 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 Docu
5、ments2.1 ASTM Standards:2E479 Guide for Preparation of a Leak Testing SpecificationE543 Specification for Agencies Performing NondestructiveTestingE1316 Terminology for Nondestructive Examinations2.2 ANSI/ASNT Standards:3ANSI/ASNT-CP-189 Standard for Qualification and Certifi-cation of Nondestructiv
6、e Testing PersonnelSNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and Certification2.3 AIA Document:4NAS-410 Certification and Qualification of NondestructiveTesting Personnel2.4 ASME Standards:5ASME Boiler and Pressure Vessel Code Section VArticle 10(paragraph T-10
7、44)2.5 ISO Standards:6ISO/IEC Guide 983 Uncertainty of Measurement Part 33. Terminology3.1 Definitions:3.1.1 pressure decay test resolutionthe resolution of thetest that can be derived from the test equipment specificationsand the volume of the test vessel. The test resolution isdetermined by evalua
8、tion of the individual resolutions of thepressure measurement, temperature measurement, and timemeasurement for a known vessel volume. The method fordetermining the test resolution is give in Annex A1.3.1.2 pressure decay test accuracythe test accuracy is theestimated accuracy of the test based on a
9、 combination of themeasurement accuracies of contributing variables. The methodfor determining the test accuracy is given in Annex A2.4. Summary of Test Method4.1 This practice requires a known volume and the use ofthe pressure rate of decay technique for quantitative measure-ment of leakage rates.
10、The practice is written to be usable overa wide range of pressures and system volumes. This method isonly applicable to the test of non-deformable volumes ordevices. Test devices which may have significant changes involume due to pressurization should not be tested with thismethod. The method requir
11、es the measurement of the systempressure and temperature as a function of time and as suchrequires that these measurements be made with calibratedinstrumentation. The range of the measurement technique canvary significantly but is generally applicable in the rangegreater than110-8mol/s (2.2 10-4std
12、cc/s)5. Significance and Use5.1 The equipment, test duration, and technique should bedetermined before commencement of the test based on the1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.08 on LeakTesting
13、 Method.Current edition approved June 1, 2013. Published June 2013. DOI: 10.1520/E2930132For 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 Summa
14、ry page onthe ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928,
15、http:/www.aia-aerospace.org.5Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.6Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/
16、www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1required test sensitivity or accuracy (see Annex A1 and AnnexA2). If the test is used to certify that the vessel has a minimumspecified leakage rate, then the test equipment
17、 and test durationshould be chosen to have a resolution ten times less than thespecification and an accuracy which is four times less than thespecification. The test should be designed so that the totalpressure change is less than 10 % of the starting pressure. Leaktest specifications should specify
18、 the vessel test pressure ordifferential pressure. If the test specification does not specify atest pressure, then a safe test pressure should be used thatcomplies with the applicable safety standards7.6. Basis of Application6.1 The following items are subject to contractual agree-ment between parti
19、es using or referencing this practice.6.2 Personnel Qualification:6.2.1 If specified in the contractual agreement, personnelperforming examinations to this practice shall be qualified inaccordance with a national or internationally recognized NDTpersonnel qualification practice or standard such as A
20、NSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similar documentand certified by the employer or certifying agency, as appli-cable. The practice or standard used and its applicable revisionshall be identified in the contractual agreement between theusing parties.6.3 Qualification of Nondestructive Agencie
21、sIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543. The applicablerevision of Practice E543 shall be in the contractual agreement.7. Interferences7.1 Interferences in the reported leak values could resultfrom desorption of gases from
22、 the vessel or adsorption of gasesinto the vessel. In addition, the effect of permeation of gasesout of the test vessel may be significant for very low leak ratemeasurements. Eq A2.3 of Annex A2 can be modified toincorporate these additional effects if appropriate. This testassumes a nominal isother
23、mal testing environment.8. Apparatus8.1 The required test equipment includes a pressure gauge/transducer of the appropriate range, automated or manualtiming system for data collection, and a temperature measure-ment device along with proper fixtures as shown in Fig. 1.9. Reagents and Materials9.1 A
24、non-condensable, inert gas is required for pressuriza-tion of the test vessel. If air is used, the dew point temperaturemust be lower than the tested temperature range.10. Hazards10.1 In no instance should the test pressure exceed themaximum allowed vessel design limits.11. Sampling, Test Specimens,
25、 and Test Units11.1 The units for test should be in mol/s or pressure basedunits of Pa m3/s or std cc/s with the units referenced to astandard temperature of 0C or 273.15 K (unless otherwisespecified in the test specification). The actual test temperaturescan vary over the specified operable ranges
26、of theinstrumentation, as long as the temperature is stable enough tomeet the test resolution requirements.12. Preparation of Apparatus12.1 Vessel PreparationThe test vessel should be cleanand dry. Hydrostatic, bubble, and liquid penetrant testingshould not be performed prior to a pressure decay tes
27、t. Allinternal components subject to deformation or failure should beremoved. Care should be taken where trapped or poorlyaccessible volumes may be encountered (double gasket seals)because they can increase the uncertainty of the test.13. Calibration and Standardization13.1 The test equipment (press
28、ure measurement, tempera-ture measurement, and time measurement) must be appropri-ately calibrated and traceable to national or internationalstandards. The accuracy of the method depends on the deter-mination of the test vessel volume as outlined in Annex A3.13.2 Commercial pressure decay systems of
29、ten use aninternal leak standard to determine the volume of the testsystem. In this case the manufacturer should specify theaccuracy of the determined volume as outlined in Annex A3.14. Conditioning14.1 The volume and test equipment should be allowed tothermally equilibrate before commencing the tes
30、t. The testvessel should not be pressurized beyond the pressure specifi-cations (or design limits).15. Procedure15.1 Assemble the test system and determine the systemvolume (see Annex A3). An isolation valve should be usedbetween the test vessel and test system for isolation purposes.7See ASME Boile
31、r and Pressure Vessel Code Section V Article 10 (paragraphT-1044)FIG. 1 Test ApparatusE2930 13215.2 Perform a leak test of the test system with the isolationvalve closed and ensure that the leakage of the test system isless than 1 % of the target test value for the test vessel.15.3 Determine the tes
32、t parameters (initial pressure and testtime) and calculate the test resolution and accuracies accordingto Annex A1 and Annex A2. Ensure that the calculated testresolution is at least ten times less than the target leakage rate.Ensure that the test accuracy is at least four times less than thetarget
33、leakage rate.15.4 Pressurize the vessel to the target pressure and closethe isolation valve 2.15.5 Stabilization Time (Setting Time)Afterpressurization, the temperature and pressure should be moni-tored as a function of time over the test duration previouslyestablished in 5.1. The pressure should be
34、 recorded at aminimum of ten time intervals during the test sequence. Thetemperature should be recorded at the beginning and end of thetest to ensure that the temperature is stable to within thepreviously assumed limits. Illustrative pressure decay leak testdata is shown in Fig. 2. During the charge
35、 phase, gas is addedto the test system. The pressure in the test system will naturallydecay due to a number of factors (pressure equilibrating withinthe test system, gas temperature equilibrating, and so forth).The settling time will be dependent on the geometry of the testsystem, the test pressures
36、 filling times, type of gas used, andother environmental factors.The leak rate should be calculated from the individualmeasurements with the following equations:N 5 PV!RTt!,mol/s (1)N 5 PV!t!TRT!,Pa m3s, or Std cc/s (2)where:V = the vessel volumeR = the universal gas constant 8.3144 J/mol K (8.3144
37、 Pam3/(mol K)T = the vessel temperature, KTR= the reference temperature for the units (typically273.15 K)P = the change in pressure between successive pointsglyph507t = the change in time in seconds between successivepointsExamples are provided in Eq 3 and 4where:glyph507P = 10000 Pa (0.1 atm)V = 0.
38、0001 m3glyph507t = 100 sec.TR= 273.15T = 298 KN 510000Pa!0.0001m3273.15K100s293K5 9.3 31023Pam3s (3)N 50.1atm!100cm3273.15K100s293K5 9.3 31022Std cm3s (4)15.6 Depending upon the test conditions, it may requireseconds to hours for the indicated leak rate to stabilize.Stabilization criteria should be
39、based on point to point varia-tions in the measured leak rate with a target of less than threetimes the calculated test resolution. The test data used in theleak calculation in Section 16 will utilize data collected afterstabilization.15.7 The leak rate calculation can be calculated using one oftwo
40、methods. Method A is preferred as it also allows forestimation of the precision of the test from the standarddeviation of the measurements.FIG. 2 Illustration of Pressure Decay Test DataE2930 13315.7.1 Method AThe average of the calculated leak ratesdetermined from successive pressure measurements a
41、fter sta-bilization.15.7.2 Method BThe leak rate is calculated from a singlepressure reading obtained after stabilization and the pressure atthe end of the test.15.8 Once the stabilization time has been determined for aparticular test system, it is not required to perform multiplepressure measuremen
42、ts when utilizing Method A. The initialpressure after stabilization and the final pressure are sufficient.16. Calculation or Interpretation of Results16.1 The leak rates should be calculated with equation 4 in15.5. The significance of the measured leak rates should beinterpreted from the computed te
43、st resolution and test accuracy.Measured leak rates which are less than or equal to either thetest accuracy or test resolution are not significant.16.2 Method AThe leak rate should be calculated using Eq1 and 2 in 15.5 with the pressure change, glyph507P, calculated as thedifference between the pres
44、sure after stabilization from thepressure at the end of the test. The change in time, glyph507t, is thedifference in elapsed time between the pressure measurements.The temperature, T, should be the average of the beginning andending temperature of the test system.16.3 Method BThe leak rate should be
45、 calculated using Eq1 and 2 in 15.5 with the pressure change, glyph507P, calculated as thedifference between the successive pressure readings afterstabilization. The change in time, glyph507t, is the difference inelapsed time between successive pressure measurements. Thetemperature, T, should be the
46、 average of the beginning andending temperature of the test system. If the temperature isrecorded with each pressure measurement, the average tem-perature between successive pressure measurements may beused. The reported leak rate should be the average of thecomputed leak rates.16.4 It is important
47、to perform multiple tests if possible tounderstand the stability of the measurements. Leak rate mea-surements can be affected by environmental variables and theseeffects can be significant; particularly when testing largevolumes (greater than 100 L).17. Report17.1 Report of TestThe report of the tes
48、t should have thefollowing information:17.1.1 Test Date17.1.2 Test Time17.1.3 Test Technician17.1.4 Test Accuracy17.1.5 Beginning vessel test pressure17.1.6 Ending vessel test pressure17.1.7 Average reference test pressure (pressure outside ofvessel)17.1.8 Average test temperature17.1.9 Duration of
49、test17.1.10 Test gas17.1.11 Average test leak rate in standard units18. Precision and Bias18.1 Precision and BiasThe bias should be calculatedusing Eq A2.4 in Annex A2. The precision may be calculatedwith either of two methods.18.1.1 Single TestIf only one test is performed, the stan-dard deviation of the calculated flows should be used toestimate the test precision (assumes Method B is used).18.1.2 Multiple TestsIf five or more tests are performed,the average and the standard deviation of the five tests shouldbe computed. The sta
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