ASTM E499-95(2000)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E499–95 (Reapproved 2000)
Standard Test Methods for
Leaks Using the Mass Spectrometer Leak Detector in the
,
Detector Probe Mode
This standard is issued under the fixed designation E499; 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 (e) indicates an editorial change since the last revision or reapproval.
This specification has been approved for use by agencies of the Department of Defense.
1. Scope 4. Summary of Test Methods
1.1 These test methods cover procedures for testing and 4.1 Section1.8oftheLeakageTestingHandbook willbeof
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locating the sources of gas leaking at the rate of 4.5 310 value to some users in determining which leak test method to
−8 3
mol/s (1 310 Std cm /s) or greater. The test may be use.
conductedonanydeviceorcomponentacrosswhichapressure 4.2 These test methods require a leak detector with a
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differential of helium or other suitable tracer gas may be full-scale readout of at least 4.5 310 mol/s (1 310 Std
3 3
created, and on which the effluent side of the leak to be tested cm /s) on the most sensitive range, a maximum 1-min drift of
is accessible for probing with the mass spectrometer sampling zero and sensitivity of 65% of full scale on this range, and
probe. 62% or less on others (see 7.1). The above sensitivities are
1.2 Two test methods are described: those obtained by probing an actual standard leak in atmo-
1.2.1 Test Method A—Direct probing, and sphere with the detector, or sampling, probe, and not the
1.2.2 Test Method B—Accumulation. sensitivityofthedetectortoastandardleakattacheddirectlyto
1.3 This standard does not purport to address all of the the vacuum system.
safety concerns, if any, associated with its use. It is the 4.3 Test Method A, Direct Probing (see Fig. 1), is the
responsibility of the user of this standard to establish appro- simplest test, and may be used in parts of any size, requiring
priate safety and health practices and determine the applica- only that a tracer gas pressure be created across the area to be
bility of regulatory limitations prior to use. tested, and the searching of the atmospheric side of the area be
with the detector probe. This test method detects leakage and
2. Referenced Documents
its source or sources. Experience has shown that leak testing
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2.1 ASTM Standards:
down to 4.5 310 mol/s (1 310 Std cm /s) in factory
E1316 Terminology for Nondestructive Examinations environments will usually be satisfactory if reasonable precau-
2.2 Other Documents:
tionsagainstreleasinggaslikethetracergasinthetestareaare
SNT-TC-1A Recommended Practice for Personnel Qualifi- observed, and the effects of other interferences (Section 6) are
cation and Certification in Nondestructive Testing
considered.
ANSI/ASNT CP-189 ASNT Standard for Qualification and 4.4 Test Method B, Accumulation Testing (see Fig. 2),
Certification of Nondestructive Testing Personnel
provides for the testing of parts up to several cubic metres in
volumeasinFig.2(a)orinportionsoflargerdevicesasinFig.
3. Terminology
2(b). This is accomplished by allowing the leakage to accu-
3.1 Definitions—For definitions of terms used in this stan-
mulate in the chamber for a fixed period, while keeping it well
dard, see Terminology E1316, Section E.
mixed with a fan, and then testing the internal atmosphere for
an increase in tracer gas content with the detector probe. The
practical sensitivity attainable with this method depends pri-
These test methods are under the jurisdiction of ASTM Committee E07 on
marilyontwothings:first,onthevolumebetweenthechamber
NondestructiveTestingandarethedirectresponsibilityofSubcommitteeE07.08on
and the object; and second, on the amount of outgassing of
Leak Testing.
tracer gas produced by the object. Thus, a part having consid-
Current edition approved Sept. 10, 1995. Published November 1995. Originally
published as E499–73. Last previous edition E499–94. erable exposed rubber, plastic, blind cavities or threads cannot
(Atmospheric pressure external, pressure above atmospheric internal). This
be tested with the sensitivity of a smooth metallic part. The
document covers the Detector Probe Mode described in Guide E432.
The gas temperature is referenced to 0°C. To convert to another gas reference
temperature, T , multiply the leak rate by (T +273)/273.
ref ref
4 6
Annual Book of ASTM Standards, Vol 03.03. Marr,J.William,“LeakageTestingHandbook,”preparedforLiquidPropulsion
Available from American Society for Nondestructive Testing, 1711 Arlingate Section,JetPropulsionLaboratory,NationalAeronauticsandSpaceAdministration,
Plaza, P.O. Box 28518, Columbus, OH 43228-0518. Pasadena, CA, Contract NAS 7-396, June 1961.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E499–95 (2000)
FIG. 1 Method A
time in which a leak can be detected is directly proportional to gas.Heliumisnormallyused.Thetestmethodisusedtolocate
the leak rate and inversely proportional to the volume between leaks but cannot be used to quantify except for approximation.
the chamber and the part. In theory, extremely small leaks can Care must be taken to provide sufficient ventilation to prevent
bedetectedbythistestmethod;however,thetimerequiredand increasing the helium background at the test site. Results are
the effects of other interferences limit the practical sensitivity limited by the helium background and the percentage of the
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of this test method to about 4.5 310 mol/s (1 310 Std leaking trace gas captured by the probe.
3 3
cm /s) for small parts. 6.2 Test Method B is used to increase the concentration of
trace gas coming through the leak by capturing it within an
5. Personnel Qualification
enclosure until the signal above the helium background can be
detected. By introducing a calibrated leak into the same
5.1 It is recommended that personnel performing leak test-
volume for a recorded time interval, leak rates can be mea-
ing attend a dedicated training course on the subject and pass
sured.
a written examination.The training course should be appropri-
ate for NDT level II qualification according to Recommended
7. Interferences
Practice No. SNT-TC-1A of the American Society for Nonde-
structive Testing or ANSI/ASNT Standard CP-189.
7.1 Atmospheric Helium—The atmosphere contains about
five parts per million (ppm) of helium, which is being
6. Significance and Use
continuously drawn in by the detector probe. This background
6.1 Test Method A is frequently used to test large systems must be “zeroed out” before leak testing using helium can
and complex piping installations that can be filled with a trace proceed. Successful leak testing is contingent on the ability of
E499–95 (2000)
FIG. 2 Method B
the detector to discriminate between normal atmospheric 7.4 Dirt and Liquids—Astheorificeinthedetectorprobeis
helium, which is very constant, and an increase in helium due very small, the parts being tested should be clean and dry to
to a leak. If the normally stable atmospheric helium level is avoid plugging. Reference should be frequently made to a
increased by release of helium in the test area, the reference standard leak to ascertain that this has not happened.
level becomes unstable, and leak testing more difficult.
7.2 Helium Outgassed from Absorbent Materials—Helium 8. Apparatus
absorbed in various nonmetallic materials (such as rubber or
8.1 Helium Leak Detector, equipped with atmospheric de-
plastics) may be released during the test. If the rate and
tector probe. To perform tests as specified in this standard, the
magnitude of the amount released approaches the amount
detector should be adjusted for testing with helium and should
released from the leak, the reliability of the test is decreased.
have the following minimum features:
Theamountofsuchmaterialsortheirexposuretoheliummust
8.1.1 Sensor Mass Analyzer.
then be reduced to obtain a meaningful test.
8.1.2 Readout, analog or digital.
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7.3 Pressurizing with Test Gas—In order to evaluate leak-
8.1.3 Range (linear)—A signal equivalent to 4.5 310
age accurately, the test gas in all parts of the device must −6 3 3
mol/s (1 310 Std cm /s) or larger must be detectable.
contain substantially the same amount of tracer gas. When the
8.1.4 Response time,3sor less.
devicecontainsairpriortotheintroductionoftestgas,orwhen
8.1.5 Stability of Zero and Sensitivity— A maximum varia-
an inert gas and a tracer gas are added separately, this may not
tionof 65%offullscaleonthemostsensitiverangewhilethe
be true. Devices in which the effective diameter and length are
probe is active; a maximum variation of 62% of full scale on
notgreatlydifferent(suchastanks)maybetestedsatisfactorily
other ranges for a period of 1 min.
by simply adding tracer gas. However, when long or restricted
NOTE 1—Variations may be a function of environmental interferences
systems are to be tested, more uniform tracer distribution will
rather than equipment limitations.
be obtained by first evacuating to less than 100 Pa (a few torr),
and then filling with the test gas. The latter must be premixed 8.1.6 Controls:
if not 100% tracer. 8.1.6.1 Range, prefereable in scale steps of 33 and 103.
E499–95 (2000)
8.1.6.2 Zero, having sufficient range to null out atmospheric 11. Procedure
helium. Automatic null to zero is preferred.
11.1 General Considerations:
8.2 Helium Leak Standard—To perform leak tests as speci-
11.1.1 Test Specifications—A testing specification shall be
fied in this standard, the leak standard should meet the
in hand. This shall include:
following minimum requirements:
11.1.1.1 The gas pressure on the high side of the device to
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8.2.1 Ranges—4.5 310 to 4.5 310 mol/s (10 to
betested;alsoonthelowsideifitneeddifferfromatmospheric
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10 Std cm /s) full scale calibrated for discharge to atmo-
pressure.
sphere.
11.1.1.2 Thetestgascomposition,ifthereisneedtospecify
8.2.2 Adjustability—Adjustable leak standards are a conve-
it.
nience but are not mandatory.
11.1.1.3 Themaximumallowableleakrateinstandardcubic
8.2.3 Accuracy, 625% of full-scale value or better.
centimetres per second.
8.2.4 Temperature Coeffıcient, shall be stated by manufac-
11.1.1.4 Whether the leak rate is for each leak or for total
turer.
leakage of the device.
8.3 Helium Leak Standard, as in 8.2 but with ranges of
11.1.1.5 Ifan“eachleak”specification,whetherornotother
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4.5 310 or 4.5 310 mol/s (10 or 10 Std cm /s).
than seams, joints, and fittings needs to be tested.
8.4 Other Apparatus—Fixtures or other equipment specific
11.1.2 Safety Factor—Where feasible, it should be ascer-
to one test method are listed under that test method.
tainedthatareasonablesafetyfactorhasbeenallowedbetween
the actual operational requirements of the device and the
9. Material
maximum specified for testing. Experience indicates that a
9.1 Test Gas Requirements: factor of at least 10 should be used when possible. For
example, if a maximum total leak rate for satisfactory opera-
9.1.1 To be satisfactory, the test gas shall be nontoxic,
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tionofadeviceis2.2 310 mol/s(5 310 Stdcm /s) ,the
nonflammable, not detrimental to common materials, and
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test requirement should be 2.2 310 mol/s (5 310 Std
inexpensive. Helium, or helium mixed with air, nitrogen, or
someothersuitableinertgasmeetstherequirements.Ifthetest cm /s) or less.
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specification allows leakage of 4.5 310 mol/s (1 310 11.1.3 Test Pressure—The device should be tested at or
Std cm /s) or more, or if large vessels are to be tested, above its operating pressure and with the pressure drop in the
consideration should be given to diluting the tracer gas with normal direction, where practical. Precautions should be taken
another gas such as dry air or nitrogen. This will avoid sothatthedevicewillnotfailduringpressurization,orthatthe
excessive helium input to the sensor and in the case of large operator is protected from the consequences of a failure.
vessels, save tracer gas expense (Note 2).
11.1.4 Disposition or Recovery of Test Gas—Test gas
9.1.2 Producing Premixed Test Gas—If the volume of the should never be dumped into the test area if further testing is
deviceorthequantitytobetestedissmall,premixedgasescan planned. It should be vented outdoors or recovered for reuse if
be conveniently obtained in cylinders. The user can also mix the volume to be used makes this worthwhile.
gases by batch in the same way. Continuous mixing using 11.1.5 Detrimental Effects of Helium Tracer Gas—This gas
calibrated orifices is another simple and convenient method is quite inert, and seldom causes any problems with most
when the test pressure does not exceed 50% of the tracer gas materials, particularly when used in gaseous form for leak
pressure available. testing and then removed. When there is a question as to the
compatibility of the tracer with a particular material, an
NOTE 2—When a vessel is not evacuated prior to adding test gas, the
authority on the latter should be consulted. This is particularly
latter is automatically diluted by one atmosphere of air.
true when helium is sealed in contact with glass or other
9.2 Liquid Nitrogen, or other means of cold trap refrigera-
barriers that it may permeate.
tion as specified by the maker of the leak detector.
11.1.6 Correlation of Test Gas Leakage with Other Gases or
Liquids at Different Operating Pressures:
10. Calibration
11.1.6.1 Given the normal variation in leak geometry, accu-
rate correlation is an impossibility. However, if a safety factor
10.1 The leak detectors used in making leak tests by these
test methods are not calibrated in the sense that they are taken of ten or more is allowed, in accordance with 11.1.2, adequate
correlation for gas leakage within these limits can usually be
to the standards laboratory, calibrated, and then returned to the
job. Rather, the leak detector is used as a comparator between obtained by assuming viscous flow and using the equation:
a leak standard (8.2) (set to the specified leak size) which is 2 2 2 2
Q 5 ~Q N /N !@~P 2 P !/~P 2 P !#
2 1 1 2 2 1 4 3
part of the instrumentation, and the unknown leak. However,
the sensitivity of the leak detector is checked and adjusted on
where:
the job so that a leak of specified size will give a readily
3 3
Q = test leakage, Pa·m /s (standard cm /s),
observable, but not off-scale reading. More specific details are 2
3 3
Q = operational leakage, Pa·m /s (standard cm /s),
giveninSection11underthetestmethodbeingused.Toverify 1
N = vi
...