ASTM E432-1991(2017)e1 6875 Standard Guide for Selection of a Leak Testing Method《选择检漏法的标准指南》.pdf
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1、Designation: E432 91 (Reapproved 2017)1Standard Guide forSelection of a Leak Testing Method1This standard is issued under the fixed designation E432; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEWithdrawn Terminology replaced with Terminology E1316 editorially in July 2017.1. Scope1.1 This guide2is intended to assist in the selection of a
3、leaktesting method.3Fig. 1 is supplied as a simplified guide.1.2 The type of item to be tested or the test system and themethod considered for either leak measurement or location arerelated in the order of increasing sensitivity.1.3 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.1.4 This international standard was developed in accor-dance with internationally reco
5、gnized 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:E1316 Terminology for
6、 Nondestructive Examinations3. Terminology3.1 DefinitionsThe definitions of terms relating to leaktesting which appear in Terminology E1316 shall apply to theterms in this guide.4. Selection of System4.1 The correct choice of a leak testing method optimizessensitivity, cost, and reliability of the t
7、est. One approach is torank the various methods according to test system sensitivity.4.2 The various testing methods must be individually ex-amined to determine their suitability for the particular systembeing tested. Only then can the appropriate method be chosen.For example, radioactive gases are
8、not generally employed asa tracer for leak location because of the hazards associated withtheir use. However, such gases are employed in leakagedetection equipment when they can be safely added to, andremoved from, a test chamber on a periodic basis.4.3 It is important to distinguish between the sen
9、sitivityassociated with the instrument employed to measure leakageand the sensitivity of the test system followed using theinstrument. The sensitivity of the instrument influences thesensitivity that can be attained in a specific test. The range oftemperatures or pressures, and the types of fluids i
10、nvolved,influence both the choice of instrument and the test system.4.4 The sensitivity of various test systems differ. Forexample, a test utilizing a mass spectrometer leak detectornormally has an ultimate sensitivity of 4.4 1015mol/s whenthe procedure involves the measurement of a steady-state gas
11、leakage rate. The sensitivity of the test may be increased underspecial conditions to 4.4 1019mol/s by allowing an accu-mulation of the leakage to occur in a known volume before ameasurement of leakage is made. In the first case, the sensi-tivity of the test equals the sensitivity of the instrument;
12、whereas in the second case, the sensitivity of the test is 104times greater than that of the instrument. If the test systemutilizes a mass spectrometer operating in the detector-probemode, the sensitivity of the test can be 102to 104smaller thanthat of the mass spectrometer itself.5. Leakage Measure
13、ment5.1 In general, leakage measurement procedures involvecovering the whole of the suspected region with tracer gas,while establishing a pressure differential across the system byeither pressurizing with a tracer gas or by evacuating theopposite side. The presence and concentration of tracer gas on
14、the lower pressure side of the system are determined and thenmeasured.5.2 A dynamic test method can be performed in the shortesttime. While static techniques increase the test sensitivity, thetime for testing is also increased.1This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc
15、-tive Testing and is the direct responsibility of Subcommittee E07.08 on Leak TestingMethod.Current edition approved June 1, 2017. Published July 2017. Originally approvedin 1971. Last previous edition approved in 2011 as E432 - 91 (2011). DOI:10.1520/E0432-91R17E01.2For ASME Boiler and Pressure Ves
16、sel Code applications see related Recom-mended Guide SE-432 in the Code.3Additional information may be obtained from Marr, J. W., Leakage TestingHandbook, Report No. CR-952, NASA, Scientific and Technical InformationFacility, P. O. Box 33, College Park, MD 20740 (Organizations registered withNASA) o
17、r Clearing House for Federal, Scientific and Technical Information, Code410.14, Port Royal Road, Springfield, VA 22151.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with interna
18、tionally 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.15.3 Equipment or devices that are the object of le
19、akagemeasurement fall into two categories: (1) open units, which areaccessible on both sides, and (2) units that are sealed. Thesecond category is usually applied to mass-produced itemsincluding gas and vacuum tubes, transistors, integrated circuitmodules, relays, ordnance units, and hermetically se
20、aled in-struments.5.3.1 Open or Single-Sealed UnitsEither evacuation orpressurization of one side of a unit that is accessible on bothsides, may be employed to test for leakage across a unit.5.3.1.1 Systems Leaking to VacuumIn the order of increas-ing sensitivity for testing an evacuated system, the
21、 methodsinclude: flow measurement, absolute pressure measurement,the alkaline-ion diode halogen detector, and the helium massspectrometer leak detector.(a) The first approach to the testing of units that may beevacuated is to determine if there is an inherent tracer in thesystem. This gas should be
22、utilized if possible.(b) When one side is evacuated, leakage of the tracer intothe vacuum will reach the detector quickly if there is essen-tially no stratification. However, evacuation does not alwaysallow the most sensitive and reliable measurement. If theevacuated region is extremely large, high
23、pumping speeds willbe required and the leakage gas will tend to follow streamlinesto the pump port. The amount of tracer gas that reaches thedetector may then be substantially reduced depending on thelocation of the detector in the evacuated region.(c) When no inherent tracer is available, the next
24、approachshould be to determine if there is a gage in the system thatmight be used for leakage measurement. This gage might be anionization gage or, in some fortunate circumstances, a massspectrometer in the system as part of the analytical instrumen-tation. Consideration should be given not only to
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