ASTM E432-91(1997)
(Guide)Standard Guide for Selection of a Leak Testing Method
Standard Guide for Selection of a Leak Testing Method
SCOPE
1.1 This guide is intended to assist in the selection of a leak testing method. Figure 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 the safety problems 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.
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Designation: E 432 – 91 (Reapproved 1997)
Standard Guide for
Selection of a Leak Testing Method
This standard is issued under the fixed designation E 432; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope detection equipment when they can be safely added to, and
2 removed from, a test chamber on a periodic basis.
1.1 This guide is intended to assist in the selection of a leak
4.3 It is important to distinguish between the sensitivity
testing method. Fig. 1 is supplied as a simplified guide.
associated with the instrument employed to measure leakage
1.2 The type of item to be tested or the test system and the
and the sensitivity of the test system followed using the
method considered for either leak measurement or location are
instrument. The sensitivity of the instrument influences the
related in the order of increasing sensitivity.
sensitivity that can be attained in a specific test. The range of
1.3 This standard does not purport to address all of the
temperatures or pressures, and the types of fluids involved,
safety concerns, if any, associated with its use. It is the
influence both the choice of instrument and the test system.
responsibility of the user of this standard to establish appro-
4.4 The sensitivity of various test systems differ. For ex-
priate safety and health practices and determine the applica-
ample, a test utilizing a mass spectrometer leak detector
bility of regulatory limitations prior to use.
−15
normally has an ultimate sensitivity of 4.4 3 10 mol/s when
2. Referenced Documents
the procedure involves the measurement of a steady-state gas
leakage rate. The sensitivity of the test may be increased under
2.1 ASTM Standards:
−19
special conditions to 4.4 3 10 mol/s by allowing an accu-
E 425 Terminology Relating to Leak Testing
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-
tivity of the test equals the sensitivity of the instrument;
3.1 Definitions—The definitions of terms relating to leak
whereas in the second case, the sensitivity of the test is 10
testing which appear in Terminology E 425 shall apply to the
times greater than that of the instrument. If the test system
terms in this guide.
utilizes a mass spectrometer operating in the detector-probe
2 4
4. Selection of System
mode, the sensitivity of the test can be 10 to 10 smaller than
that of the mass spectrometer itself.
4.1 The correct choice of a leak testing method optimizes
sensitivity, cost, and reliability of the test. One approach is to
5. Leakage Measurement
rank the various methods according to test system sensitivity.
5.1 In general, leakage measurement procedures involve
4.2 The various testing methods must be individually ex-
covering the whole of the suspected region with tracer gas,
amined to determine their suitability for the particular system
while establishing a pressure differential across the system by
being tested. Only then can the appropriate method be chosen.
either pressurizing with a tracer gas or by evacuating the
For example, radioactive gases are not generally employed as
opposite side. The presence and concentration of tracer gas on
a tracer for leak location because of the hazards associated with
the lower pressure side of the system are determined and then
their use. However, such gases are employed in leakage
measured.
5.2 A dynamic test method can be performed in the shortest
This guide is under the jurisdiction of ASTM Committee E-7 on Nondestructive
time. While static techniques increase the test sensitivity, the
Testing and is the direct responsibility of Subcommittee E07.08 on Leak Testing.
time for testing is also increased.
Current edition approved April 15, 1991. Published June 1991. Originally
e1 5.3 Equipment or devices that are the object of leakage
published as E 432 – 71. Last previous edition E 432 – 71 (1984) .
For ASME Boiler and Pressure Vessel Code applications see related Recom- measurement fall into two categories: (1) open units, which are
mended Guide SE-432 in the Code.
accessible on both sides, and (2) units that are sealed. The
Additional information may be obtained from Marr, J. W., Leakage Testing
second category is usually applied to mass-produced items
Handbook, Report No. CR-952, NASA, Scientific and Technical Information
including gas and vacuum tubes, transistors, integrated circuit
Facility, P. O. Box 33, College Park, MD 20740 (Organizations registered with
NASA) or Clearing House for Federal, Scientific and Technical Information, Code
modules, relays, ordnance units, and hermetically sealed in-
410.14, Port Royal Road, Springfield, VA 22151.
struments.
Annual Book of ASTM Standards, Vol 03.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 432 – 91 (1997)
FIG. 1 Guide for Selection of Leakage Testing Method
5.3.1 Open or Single-Sealed Units—Either evacuation or be an ionization gage or, in some fortunate circumstances, a
pressurization of one side of a unit that is accessible on both mass spectrometer in the system as part of the analytical
sides, may be employed to test for leakage across a unit. instrumentation. Consideration should be given not only to
5.3.1.1 Systems Leaking to Vacuum—In the order of in- gages that are normally used for leak detection, but to any gas
creasing sensitivity for testing an evacuated system, the meth- concentration detection equipment that may be used for leak-
ods include: flow measurement, absolute pressure measure- age measurement if it happens to be available. Equipment not
ment, the alkaline-ion diode halogen detector, and the helium originally intended for pressure measurement may be used; for
mass spectrometer leak detector. example, it is possible to detect the pressure rise in a leaking
(a) (a) The first approach to the testing of units that may be vacuum tube by operating the grid at a positive and an anode
evacuated is to determine if there is an inherent tracer in the at a negative potential, and noting an increase in anode current
system. This gas should be utilized if possible. with time.
(b) (b) When one side is evacuated, leakage of the tracer (d) (d) When there is no inherent tracer or gage within the
into the vacuum will reach the detector quickly if there is system, a standard testing method must be chosen based on the
essentially no stratification. However, evacuation does not sensitivity desired.
always allow the most sensitive and reliable measurement. If 5.3.1.2 Systems Leaking to Atmosphere—The choice of a
the evacuated region is extremely large, high pumping speeds testing method
...
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