ASTM E432-91(2017)e1
(Guide)Standard Guide for Selection of a Leak Testing Method
Standard Guide for Selection of a Leak Testing Method
ABSTRACT
This guide deals with the selection of the appropriate leak testing method for either leak measurement or location for a particular system being tested (test system), which may consist either of open units or sealed units. The leak testing method may either be dynamic or static, with the dynamic test method requiring shorter time but lesser sensitivity as compared to static techniques. The choice of the appropriate leak testing method shall involve most importantly the optimization of the sensitivity, cost, and reliability of the test. In the case where various testing methods are available for a particular test system, each shall be examined separately and then ranked according to test system sensitivity. However, when determining the sensitivity, it is important to be able to differentiate the sensitivity associated with the instrument used to measure leakage from the sensitivity of the test system followed using the instrument. While the sensitivity of a specific test is dependent on the sensitivity of the instrument used, the choice of instrument and the test system are both influenced by the range of temperatures or pressures and the kinds of fluids involved.
SCOPE
1.1 This guide2 is intended to assist in the selection of a leak testing method.3Fig. 1 is supplied as a simplified guide.
FIG. 1 Guide for Selection of Leakage Testing Method
1.2 The type of item to be tested or the test system and the method considered for either leak measurement or location are related in the order of increasing sensitivity.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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´1
Designation: E432 − 91 (Reapproved 2017)
Standard Guide for
Selection of a Leak Testing Method
This standard is issued under the fixed designation E432; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Withdrawn Terminology replaced with Terminology E1316 editorially in July 2017.
1. Scope 4.2 The various testing methods must be individually ex-
2 amined to determine their suitability for the particular system
1.1 Thisguide isintendedtoassistintheselectionofaleak
being tested. Only then can the appropriate method be chosen.
testing method. Fig. 1 is supplied as a simplified guide.
For example, radioactive gases are not generally employed as
1.2 The type of item to be tested or the test system and the
atracerforleaklocationbecauseofthehazardsassociatedwith
method considered for either leak measurement or location are
their use. However, such gases are employed in leakage
related in the order of increasing sensitivity.
detection equipment when they can be safely added to, and
1.3 This standard does not purport to address all of the
removed from, a test chamber on a periodic basis.
safety concerns, if any, associated with its use. It is the
4.3 It is important to distinguish between the sensitivity
responsibility of the user of this standard to establish appro-
associated with the instrument employed to measure leakage
priate safety and health practices and determine the applica-
and the sensitivity of the test system followed using the
bility of regulatory limitations prior to use.
instrument. The sensitivity of the instrument influences the
1.4 This international standard was developed in accor-
sensitivity that can be attained in a specific test. The range of
dance with internationally recognized principles on standard-
temperatures or pressures, and the types of fluids involved,
ization established in the Decision on Principles for the
influence both the choice of instrument and the test system.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 4.4 The sensitivity of various test systems differ. For
example, a test utilizing a mass spectrometer leak detector
Barriers to Trade (TBT) Committee.
−15
normally has an ultimate sensitivity of 4.4×10 mol/s when
2. Referenced Documents
the procedure involves the measurement of a steady-state gas
2.1 ASTM Standards:
leakage rate.The sensitivity of the test may be increased under
−19
E1316Terminology for Nondestructive Examinations
special conditions to 4.4×10 mol/s by allowing an accu-
mulation of the leakage to occur in a known volume before a
3. Terminology
measurement of leakage is made. In the first case, the sensi-
3.1 Definitions—The definitions of terms relating to leak
tivity of the test equals the sensitivity of the instrument;
testing which appear in Terminology E1316 shall apply to the 4
whereas in the second case, the sensitivity of the test is 10
terms in this guide.
times greater than that of the instrument. If the test system
utilizes a mass spectrometer operating in the detector-probe
4. Selection of System
2 4
mode, the sensitivity of the test can be 10 to 10 smaller than
4.1 The correct choice of a leak testing method optimizes
that of the mass spectrometer itself.
sensitivity, cost, and reliability of the test. One approach is to
rank the various methods according to test system sensitivity.
5. Leakage Measurement
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc- 5.1 In general, leakage measurement procedures involve
tiveTestingandisthedirectresponsibilityofSubcommitteeE07.08onLeakTesting
covering the whole of the suspected region with tracer gas,
Method.
while establishing a pressure differential across the system by
CurrenteditionapprovedJune1,2017.PublishedJuly2017.Originallyapproved
either pressurizing with a tracer gas or by evacuating the
in 1971. Last previous edition approved in 2011 as E432-91 (2011). DOI:
10.1520/E0432-91R17E01.
opposite side. The presence and concentration of tracer gas on
For ASME Boiler and Pressure Vessel Code applications see related Recom-
the lower pressure side of the system are determined and then
mended Guide SE-432 in the Code.
measured.
Additional information may be obtained from Marr, J. W., Leakage Testing
Handbook, Report No. CR-952, NASA, Scientific and Technical Information
5.2 Adynamic test method can be performed in the shortest
Facility, P. O. Box 33, College Park, MD 20740 (Organizations registered with
time. While static techniques increase the test sensitivity, the
NASA) or Clearing House for Federal, Scientific and Technical Information, Code
410.14, Port Royal Road, Springfield, VA 22151. time for testing is also increased.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
E432 − 91 (2017)
FIG. 1 Guide for Selection of Leakage Testing Method
5.3 Equipment or devices that are the object of leakage be required and the leakage gas will tend to follow streamlines
measurementfallintotwocategories:(1)openunits,whichare to the pump port. The amount of tracer gas that reaches the
accessible on both sides, and (2) units that are sealed. The detector may then be substantially reduced depending on the
second category is usually applied to mass-produced items location of the detector in the evacuated region.
including gas and vacuum tubes, transistors, integrated circuit (c)When no inherent tracer is available, the next approach
modules, relays, ordnance units, and hermetically sealed in- should be to determine if there is a gage in the system that
struments. mightbeusedforleakagemeasurement.Thisgagemightbean
5.3.1 Open or Single-Sealed Units—Either evacuation or ionization gage or, in some fortunate circumstances, a mass
pressurization of one side of a unit that is accessible on both spectrometer in the system as part of the analytical instrumen-
sides, may be employed to test for leakage across a unit. tation.Considerationshouldbegivennotonlytogagesthatare
5.3.1.1 Systems Leaking to Vacuum—Intheorderofincreas- normally used for leak detection, but to any gas concentration
ing sensitivity for testing an evacuated system, the methods detectionequipmentthatmaybeusedforleakagemeasurement
include: flow measurement, absolute pressure measurement, ifithappenstobeavailable.Equipmentnotoriginallyintended
the alkaline-ion diode halogen detector, and the helium mass for pressure measurement may be used; for example, it is
spectrometer leak detector. possibletodetectthepressureriseinaleakingvacuumtubeby
(a)The first approach to the testing of units that may be operating the grid at a positive and an anode at a negative
evacuated is to determine if there is an inherent tracer in the potential, and noting an increase in anode current with t
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: E432 − 91 (Reapproved 2011) E432 − 91 (Reapproved 2017)
Standard Guide for
Selection of a Leak Testing Method
This standard is issued under the fixed designation E432; the number immediately following the designation indicates the year of
original adoption or, in 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.
ε NOTE—Withdrawn Terminology replaced with Terminology E1316 editorially in July 2017.
1. Scope
2 3
1.1 This guide is intended to assist in the selection of a leak testing method. Fig. 1 is supplied as a simplified guide.
1.2 The type of item to be tested or the test system and the method considered for either leak measurement or location are related
in the order of increasing sensitivity.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E425E1316 Definitions of Terms Relating to Leak TestingTerminology for Nondestructive Examinations (Withdrawn 1991)
3. Terminology
3.1 Definitions—The definitions of terms relating to leak testing which appear in Terminology E425E1316 shall apply to the
terms in this guide.
4. Selection of System
4.1 The correct choice of a leak testing method optimizes sensitivity, cost, and reliability of the test. One approach is to rank
the various methods according to test system sensitivity.
4.2 The various testing methods must be individually examined to determine their suitability for the particular system being
tested. Only then can the appropriate method be chosen. For example, radioactive gases are not generally employed as a tracer for
leak location because of the hazards associated with their use. However, such gases are employed in leakage detection equipment
when they can be safely added to, and removed from, a test chamber on a periodic basis.
4.3 It is important to distinguish between the sensitivity associated with the instrument employed to measure leakage and the
sensitivity of the test system followed using the instrument. The sensitivity of the instrument influences the sensitivity that can be
attained in a specific test. The range of temperatures or pressures, and the types of fluids involved, influence both the choice of
instrument and the test system.
4.4 The sensitivity of various test systems differ. For example, a test utilizing a mass spectrometer leak detector normally has
−15
an ultimate sensitivity of 4.4 × 10 mol/s when the procedure involves the measurement of a steady-state gas leakage rate. The
−19
sensitivity of the test may be increased under special conditions to 4.4 × 10 mol/s by allowing an accumulation of the leakage
to occur in a known volume before a measurement of leakage is made. In the first case, the sensitivity of the test equals the
This guide is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.08 on Leak Testing Method.
Current edition approved July 1, 2011June 1, 2017. Published July 2011July 2017. Originally approved in 1971. Last previous edition approved in 20042011 as E432 - 91
(2004).(2011). DOI: 10.1520/E0432-91R11.10.1520/E0432-91R17E01.
For ASME Boiler and Pressure Vessel Code applications see related Recommended Guide SE-432 in the Code.
Additional information may be obtained from Marr, J. W., Leakage Testing Handbook, Report No. CR-952, NASA, Scientific and Technical Information Facility, P. O.
Box 33, College Park, MD 20740 (Organizations registered with NASA) or Clearing House for Federal, Scientific and Technical Information, Code 410.14, Port Royal Road,
Springfield, VA 22151.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
E432 − 91 (2017)
FIG. 1 Guide for Selection of Leakage Testing Method
sensitivity of the instrument; whereas in the second case, the sensitivity of the test is 10 times greater than that of the instrument.
2 4
If the test system utilizes a mass spectrometer operating in the detector-probe mode, the sensitivity of the test can be 10 to 10
smaller than that of the mass spectrometer itself.
5. Leakage Measurement
5.1 In general, leakage measurement procedures involve covering the whole of the suspected region with tracer gas, while
establishing a pressure differential across the system by either pressurizing with a tracer gas or by evacuating the opposite side.
The presence and concentration of tracer gas on the lower pressure side of the system are determined and then measured.
5.2 A dynamic test method can be performed in the shortest time. While static techniques increase the test sensitivity, the time
for testing is also increased.
5.3 Equipment or devices that are the object of leakage measurement fall into two categories: (1) open units, which are
accessible on both sides, and (2) units that are sealed. The second category is usually applied to mass-produced items including
gas and vacuum tubes, transistors, integrated circuit modules, relays, ordnance units, and hermetically sealed instruments.
5.3.1 Open or Single-Sealed Units—Either evacuation or pressurization of one side of a unit that is accessible on both sides,
may be employed to test for leakage across a unit.
5.3.1.1 Systems Leaking to Vacuum—In the order of increasing sensitivity for testing an evacuated system, the methods include:
flow measurement, absolute pressure measurement, the alkaline-ion diode halogen detector, and the helium mass spectrometer leak
detector.
(a) The first approach to the testing of units that may be evacuated is to determine if there is an inherent tracer in the system.
This gas should be utilized if possible.
(b) When one side is evacuated, leakage of the tracer into the vacuum will reach the detector quickly if there is essentially no
stratification. However, evacuation does not always allow the most sensitive and reliable measurement. If the evacuated region is
´1
E432 − 91 (2017)
extremely large, high pumping speeds will be required and the leakage gas will tend to follow streamlines to the pump port. The
amount of tracer gas that reaches the detector may then be substantially reduced depending on the location of the detector in the
evacuated region.
(c) When no inherent tracer is available, the next approach should be to determine if there is a gage in the system that might
be used for leakage measurement. This gage might be an ionization gage or, in some fortunate circumstances, a mass spectrometer
in the system as par
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