ASTM E498-95(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E498–95 (Reapproved 2006)
Standard Test Methods for
Leaks Using the Mass Spectrometer Leak Detector or
,
1 2
Residual Gas Analyzer in the Tracer Probe Mode
This standard is issued under the fixed designation E498; 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.
This specification has been approved for use by agencies of the Department of Defense.
1. Scope 2.2 Other Documents:
SNT-TC-1A Recommended Practice for Personnel Qualifi-
1.1 These test methods cover procedures for testing and
−14
cation and Certification in Nondestructive Testing
locating the sources of gas leaking at the rate of 4.5 310
−9 3
3 ANSI/ASNT CP-189 ASNT Standard for Qualification and
mol/s (1 310 Std cm /s) or greater. The test may be
Certification of Nondestructive Testing Personnel
conducted on any object to be tested that can be evacuated and
to the other side of which helium or other tracer gas may be
3. Terminology
applied.
3.1 Definitions—For definitions of terms used in this stan-
1.2 Three test methods are described:
dard, see Terminology E1316, Section E.
1.2.1 Test Method A—For the object under test capable of
being evacuated, but having no inherent pumping capability.
4. Summary of Test Methods
1.2.2 Test Method B—Fortheobjectundertestwithintegral
4.1 Thesetestmethodsrequireaheliumleakdetectorthatis
pumping capability.
−15 −10
capableofdetectingaleakof4.5 310 mol/s(1 310 Std
1.2.3 Test Method C—For the object under test as in Test
3 3
cm /s).
MethodB,inwhichthevacuumpumpsoftheobjectundertest
4.2 Test Method A—This test method is used to helium leak
replace those normally used in the leak detector.
test objects that are capable of being evacuated to a reasonable
1.3 This standard does not purport to address all of the
testpressurebytheleakdetectorpumpsinanacceptablelength
safety concerns, if any, associated with its use. It is the
of time. This requires that the object be clean and dry and
responsibility of the user of this standard to establish appro-
usually no larger than a few cubic feet in volume.Also to cope
priate safety and health practices and determine the applica-
with larger volumes or relatively“ dirty” devices, auxiliary
bility of regulatory limitations prior to use. A specific hazard
vacuum pumps having greater capacity than those in the mass
statement can be found in 19.2.
spectrometer leak detector (MSLD) may be used in conjunc-
tion with the MSLD. The leak test sensitivity will be reduced
2. Referenced Documents
4 under these conditions.
2.1 ASTM Standards:
4.3 Test Method B—This test method is used to leak test
E1316 Terminology for Nondestructive Examinations
equipmentthatcanprovideitsownvacuum(thatis,equipment
that has a built-in pumping system) at least to a level of a few
These test methods are under the jurisdiction of ASTM Committee E07 on
hundred pascals (a few torr) or lower.
Nondestructive Testing and is the direct responsibility of Subcommittee E07.08 on
4.4 Test Method C—When a vacuum system is capable of
Leak Testing Method.
−2
Current edition approved Dec. 1, 2006. Published January 2007. Originally
producing internal pressures of less than 2 3 10 Pa
approvedin1973.Lastpreviouseditionapprovedin2000asE498-95(2000).DOI: −4
(2 310 torr) in the presence of leaks, these leaks may be
10.1520/E0498-95R06.
located and evaluated by the use of either a residual gas
(Atmospheric pressure external, vacuum internal). This document covers the
Tracer Probe Mode described in Terminology E1316. analyzer(RGA)orbyusingthespectrometertubeandcontrols
The gas temperature is referenced to 0°C. To convert to another gas reference
from a conventional MSLD, provided, of course, that the
temperature, T , multiply the leak rate by (T +273)/273.
ref ref
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
the ASTM website. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E498–95 (2006)
leakage is within the sensitivity range of the RGA or MSLD 7.1.5 Casings with internal voids.
under the conditions existing in the vacuum system.
7.1.6 Flat polymer gaskets.
7.1.7 Unvented O-ring grooves.
5. Personnel Qualification
7.2 In general, the solution is in proper design to eliminate
5.1 It is recommended that personnel performing leak test-
theseconditions;however,whendoublesealsmustbeused,an
ing attend a dedicated training course on the subject and pass
accessportbetweenthemshouldbeprovidedforattachmentto
a written examination.The training course should be appropri-
the MSLD. Leaks may then be located from each side of the
ate for NDT level II qualification according to Recommended
seal and after repair, the access port can be sealed or pumped
Practice No. SNT-TC-1A of theAmerican Society for Nonde-
continuously by a “holding” pump (large vacuum systems).
structive Testing or ANSI/ASNT Standard CP-189.
7.3 Temporarily plugged leaks often occur because of poor
manufacturing techniques. Water, cleaning solvent, plating,
6. Significance and Use
flux, grease, paint, etc., are common problems. To a large
6.1 TestMethodAisthemostfrequentlyusedinleaktesting
extent,theseproblemscanbeeliminatedbyproperpreparation
components which are structurally capable of being evacuated
of the parts before leak testing. Proper degreasing, vacuum
−3
to pressures of 0.1 Pa (approximately 10 torr). Testing of
baking, and testing before plating or painting are desirable.
smallcomponentscanbecorrelatedtocalibratedleaks,andthe
7.4 In a device being tested, capillary tubing located be-
actualleakratecanbemeasuredoracceptancecanbebasedon
tween the leak and the leak detector can make leak testing
a maximum allowable leak. For most production needs accep-
extremely difficult as test sensitivity is drastically reduced and
tance is based on acceptance of parts leaking less than an
responsetimeincreased.Ifthereisavolumeateachendofthe
established standard which will ensure safe performance over
capillary, each such volume should be attached to the leak
the projected life of the component. Care must be exercised to
detector during testing. If this is impossible, the device should
ensure that large systems are calibrated with reference leak at
be surrounded with a helium atmosphere while attached to the
a representative place on the test volume. Leak rates are
leak detector for a long time to assure leak tightness. When
determinedbycalculatingthenetgainorlossthroughaleakin
unusually long pumping times are necessary, the connections
thetestpartthatwouldcausefailureduringtheexpectedlifeof
to the leak detector (and all other auxiliary connections) that
the device.
are exposed to the helium should be double-sealed and the
6.2 TestMethodBisusedfortestingvacuumsystemseither
space between the seals evacuated constantly by a small
as a step in the final test of a new system or as a maintenance
auxiliary roughing pump to avoid allowing helium to enter the
practice on equipment used for manufacturing, environmental
system through seals that are not a part of the device to be
test or for conditioning parts.As the volume tends to be large,
tested.
a check of the response time as well as system sensitivity
should be made. Volume of the system in liters divided by the
TEST METHOD A—HELIUM LEAK TESTING OF
speed of the vacuum pump in L/s will give the response time
SMALL DEVICES USING THE MSLD
to reach 63% of the total signal. Response times in excess of
a few seconds makes leak detection difficult.
8. Apparatus
6.3 Test Method C is to be used only when there is no
8.1 Helium Mass Spectrometer Leak Detector, having a
convenientmethodofconnectingtheleakdetectortotheoutlet
minimumdetectableleakrateasrequiredbythetestsensitivity.
ofthehighvacuumpump.Ifaheliumleakdetectorisusedand
8.2 Auxiliary Pumps, capable of evacuating the object to be
the high vacuum pump is an ion pump or cryopump, leak
tested to a low enough pressure so that the MSLD may be
testingisbestaccomplishedduringtheroughingcycleasthese
connected.
pumps leave a relatively high percentage of helium in the high
vacuum chamber.This will obscure all but large leaks, and the
NOTE 1—If the object under test is small and clean and the MSLD has
trace gas will quickly saturate the pumps.
a built-in roughing pump, the auxiliary pumps are not required.
8.3 Suitable Connectors and Valves, to connect to the
7. Interferences
MSLD test port. Compression fittings and metal tubing should
7.1 Series leaks with an unpumped volume between them
be used in preference to vacuum hose.
present a difficult if not impossible problem in helium leak
8.4 Standard Leaks of Both Capsule Type (Containing its
testing. Although the trace gas enters the first leak readily
own Helium Supply) and Capillary Type (anActual Leak which
enough since the pressure difference of helium across the first
is Used to Simulate the Reaction of the Test System to Helium
leak is approximately one atmosphere, it may take many hours
Spray)—The leak rate from the capsule-type leak should be
to build up the partial pressure of helium in the volume
adequate to demonstrate the minimum allowable sensitivity of
betweenthetwoleakssothatenoughheliumentersthevacuum
the MSLD. The capillary type should be slightly smaller than
system to be detected by the MSLD. This type of leak occurs
the test requirement.
frequently under the following conditions:
8.5 Vacuum Gage, to read the pressure before the MSLD is
7.1.1 Double-welded joints and lap welds.
connected.
7.1.2 Double O-rings.
7.1.3 Threaded joints. 8.6 Helium Tank and Regulator,withattachedheliumprobe
7.1.4 Ferrule and flange-type tubing fittings. hose and jet.
E498–95 (2006)
9. Calibration of MSLD 10.7 Afterthefirstleakhasbeenfoundandsealed,thesame
technique is continued until all leaks have been similarly
9.1 Attach the capsule leak to the MSLD and tune the
treated.
MSLD to achieve maximum sensitivity in accordance with the
10.8 After all leaks have been found and repaired, it is
manufacturer’s instruction. Allow sufficient time for the flow
desirable to enclose the entire device in a helium envelope
rate from the capsule leak to equilibrate. The capsule leak
(which can be a plastic bag or a large bell jar) to determine the
should be stored with the shutoff valve
...