ASTM E427-95(2000)
(Practice)Standard Practice for Testing for Leaks Using the Halogen Leak Detector (Alkali-Ion Diode)
Standard Practice for Testing for Leaks Using the Halogen Leak Detector (Alkali-Ion Diode)
SCOPE
1.1 This practice covers procedures for testing and locating the sources of gas leaking at the rate of 2.2 X 10 -14 mol/s (5 X 10 -10 Std cm3/s). The test may be conducted on any device or component across which a pressure differential of halogen tracer gas may be created, and on which the effluent side of the area to be leak tested is accessible for probing with the halogen leak detector.
1.2 Five methods are described:
1.2.1 Method A -Direct probing with no significant halogen contamination in the atmosphere.
1.2.2 Method B -Direct probing with significant halogen contamination in the atmosphere.
1.2.3 Method C -Shroud test.
1.2.4 Method D -Air-curtain shroud test.
1.2.5 Method E -Accumulation test.
1.3 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate.
1.4 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.
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Designation:E427–95 (Reapproved 2000)
Standard Practice for
Testing for Leaks Using the Halogen Leak Detector
(Alkali-Ion Diode)
This standard is issued under the fixed designation E427; 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.
1. Scope ANSI/ASNTCP-189 ASNTStandard for Qualification and
Certification of Nondestructive Testing Personnel
1.1 This practice covers procedures for testing and locating
−14
the sources of gas leaking at the rate of 2.2 310 mol/s
3. Terminology
−10 3
(5 310 Std cm /s). The test may be conducted on any
3.1 Definitions—For definitions of terms used in this stan-
device or component across which a pressure differential of
dard, see Terminology E1316, Section E.
halogen tracer gas may be created, and on which the effluent
side of the area to be leak tested is accessible for probing with
4. Summary of Practice
the halogen leak detector.
4.1 Section1.8ofNASA’s Leakage Testing Handbook will
1.2 Five methods are described:
be of value to some users in determining which leak test
1.2.1 MethodA—Directprobingwithnosignificanthalogen
method to use. Section 11 of the ASNT Testing Handbook may
contamination in the atmosphere.
also be of value.
1.2.2 Method B—Direct probing with significant halogen
4.2 These methods require halogen leak detection equip-
contamination in the atmosphere.
−13
ment with a full-scale readout of at least 1.3 310 mol/s
1.2.3 Method C—Shroud test.
−10 3
(3 310 Std cm /s) on the most sensitive range, a maxi-
1.2.4 Method D—Air-curtain shroud test.
mum1mindriftof0andsensitivitydriftof 615percentoffull
1.2.5 Method E—Accumulation test.
scale on this range, and 65 percent or less on others (see
1.3 The values stated in inch-pound units are to be regarded
8.1.5).
as the standard. The metric equivalents of inch-pound units
4.3 MethodA(Fig.1)isthesimplesttest,requiringonlythat
may be approximate.
a halogen tracer-gas pressure be created across the area to be
1.4 This standard does not purport to address all of the
tested, and the searching of the atmospheric side of the area
safety concerns, if any, associated with its use. It is the
with the detector probe. This method detects leakage and
responsibility of the user of this standard to establish appro-
locatesitssourceorsources,whenusedinatestareafreefrom
priate safety and health practices and determine the applica-
significant halogen contamination in the atmosphere (see 7.1).
bility of regulatory limitations prior to use.
−10
Experience has shown that leak detection down to 4.5 310
−5 3 2
2. Referenced Documents mol/s (1 310 Std cm /s) in factory environments will
usually be satisfactory if reasonable precautions are taken
2.1 ASTM Standards:
3 against releasing halogens in the building. If a test booth is
E1316 Terminology for Nondestructive Examinations
constructedsoastobepurgedwithcleanoutdoorair,thislevel
2.2 Other Documents:
−12 −7 3 2
may be reduced to 4.5 310 mol/s (1 310 Std cm /s).
ASNT “Leak Testing Handbook” Volume One of “Nonde-
−13 −9 3
4 Testingdownto4.5 310 mol/s(1 310 Stdcm /s) will
structive Testing Handbook”
require additional halogen removal. This can be accomplished
SNT-TC-1A Recommended Practice for Personnel Qualifi-
4 by passing the test-booth purge air through a bed of activated
cation and Certification in Nondestructive Testing
charcoal.
4.4 Method B (Fig. 2) is essentially the same as MethodA,
except that the amount of air drawn by the probe from the test
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
area is reduced, and the required sample flow is made up with
structive Testing and is the direct responsibility of Subcommittee E07.08 on Leak
pure (that is, zero-halogen) air.This reduced sample intake has
Testing Method.
Current edition approved Sept. 10, 1995. Published November 1995. Originally the disadvantage of reducing the vacuum-cleaner effect of the
published as E427–71. Last previous edition E427–94.
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
3 5
Annual Book of ASTM Standards, Vol 03.03. Marr, J. William, Leakage Testing Handbook, prepared for Liquid Propulsion
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 1967.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E427–95 (2000)
FIG. 4 Simple Shroud Leak Test, Method C
itemswhichhaveanapproximatecross-sectiondimensionof2
in.(50mm),butmaybeaslongas30ft(10m).Inthismethod,
air, either atmospheric or purified, is passed over the halogen-
FIG. 1 Halogen Leak Detector, Method A
pressurized part, which is inside a close-fitting container. The
discharge air from the container is sampled by the halogen
detector, and any additional halogen content indicated. The
shroud principle may be applied in a manner as simple as Fig.
4, wherein a piece of tape is applied around a flanged joint to
be tested, or as complete as in Fig. 3. The latter provides
isolation of the detector from atmospheric halogens, a pure-air
reference supply, and a convenient calibration means. This
−12
enables detection of leaks as small as 4.5 310 mol/s
−7 3
(1 310 Std cm /s).
FIG. 2 Proportioning Probe, Halogen Leak Detector, Method B
4.6 Method D (Fig. 5) is useful for high-production testing
of small items such as transistors which have been previously
subjected to a halogen gas pressure above atmospheric
larger flow and thus requires closer and more careful probing. (bombed), or testing the sealed-off end of a fill tube, and the
However, the tolerance to atmospheric halogen can be in- like. In this method, the end of the shroud is always open, and
creased up to 100 times.Also, large leaks beyond the range of the detector always draws a sample from the lower end.
Method A can be accurately located (but not measured) by Atmospheric halogens are prevented from entering by a
Method B. laminar-flow pure-air curtain. When any leaking object is
4.5 Method C (Fig. 3 and Fig. 4) is suited for leak testing inserted below the flow division level, the leakage is then
FIG. 3 Shroud Leak Test, Method C
E427–95 (2000)
2 3 −9
system of 10 cm net volume, or a 2.2 310 mol/s
−5 3 2 7 3
(5 310 Std cm /s) leak in a 10 -cm system. Where
variables,time,volume,andleakratepermit,valuesofreadout
−12 −13 −7
should be set in the 4.5 310 or 4.5 310 mol/s (10 or
−8 3
10 Std cm /s) range for less critical operation. Methods C,
D, and E are well adapted for automation of valving and
material handling.
5. Personnel Qualification
5.1 It is recommended that personnel performing leak test-
FIG. 5 Air-Curtain-Shroud Leak Test, Method D
ing attend a dedicated training course on the subject and pass
a written examination.The training course should be appropri-
ate for NDT level II qualification according to Recommended
picked up by the detector. This method is useful for detecting
−12 −7 3 2
Practice No. SNT-TC-1Aof theAmerican Society for Nonde-
leaksdownto4.5 310 mol/s(1 310 Stdcm /s) insize.
structive Testing, or ANSI/ASNT Standard CP-189.
4.7 MethodE(Fig.6)issimilartoMethodC(Fig.3),except
it provides for testing parts up to several cubic meters in
6. Significance and Use
volume. This is accomplished by allowing the leakage to
accumulate in the chamber for a fixed period, while keeping it
6.1 Halogen leak testing can be used to indicate the pres-
wellmixedwithafan,andthentestingtheinternalatmosphere ence, location and magnitude of leaks in a closed vessel. This
for an increase in halogen content. The practical sensitivity
test method is normally used for production examination. Its
attainable with this method depends primarily on two things.
use with halogenated refrigerant gases has been declining
First, on the volume between the shroud and the object; and
because of concerns about the effect of these gases on the
second, on the amount of halogen outgassing produced by the
ozone layer.
object.Thus,apartcontainingrubber,plastics,blindcavitiesor
threads cannot be tested with the sensitivity obtainable with a
7. Interferences
smoothmetallicpart.Thesensitivityofthetestandnetvolume
7.1 Atmospheric Halogens—Whendirectprobing(Methods
of the system are related as follows:
A and B) is used to locate leaks, the leak detector probe is
A 5 LF/V (1)
drawing in air from the atmosphere. If the atmosphere is
s
contaminated with halogen to a degree that produces a notice-
where:
able indication on the detector, the detection of halogen from
A = rate of halogen increase in the volume, mol/s,
s
leaks becomes much more difficult. Significant atmospheric
L = leak rate into the volume, mol/s,
contamination with halogen is defined as the level where the
F = flow rate in the detector probe, mol/s, and
detectorresponse,whentheprobeismovedfromzero-halogen
V = net volume of the system, cm .
air to test-area atmosphere, exceeds that expected from the
For practical operating considerations, the minimum value
−16 smallest leak to be detected. For reliable testing, atmospheric
of A that should be used is about 8.9 310 mol/s (2 310
s
2 halogen must be kept well below this level.
−11 Std cm /s). (This will give a detector readout of
−11 −13 −9 3 2 7.2 Halogens Outgassed from Absorbent Materials—When
100 310 or 4.5 310 mol/s (1 310 Std cm /s) after
leak testing is done in enclosures which prevent atmospheric
a 50-s accumulation period.) Thus, (based on F=mol/s) a
−14
−10 3 2 contamination from interfering with the test (Methods A, B,
2.2 310 mol/s (5 310 Std cm /s) may be detected in a
and C), halogen absorbed in various nonmetallic materials
(suchasrubberorplastics)maybereleasedintheenclosure.If
the amount released starts to approach the amount from the
leak in the same period of time, then a reliable leak test
becomes more difficult. The amount of such materials in the
enclosure,ortheirexposuretohalogenmustthenbereducedto
obtain a meaningful test.
7.3 Pressurizing with Test Gas—In order to evaluate leak-
age accurately, the test gas in all parts of the device must
contain substantially the same amount of tracer gas. When the
devicecontainsairpriortotheintroductionoftestgas,orwhen
an inert gas and a tracer gas are added separately, this may not
be true. Devices in which the effective diameter and length are
notgreatlydifferent(suchastanks)maybetestedsatisfactorily
by simply adding tracer gas. However, when long or restricted
systems are to be tested, more uniform tracer distribution will
be obtained by first evacuating to a few torr, and then filling
withthetestgas.Thelattermustbepremixedifnot100percent
FIG. 6 Accumulation Leak Test, Method E tracer.
E427–95 (2000)
8. Apparatus nonhalogen gas through the liquid tracer. This produces test
gas containing the maximum amount of tracer gas.
8.1 Halogen Leak Detector—Toperformleaktestsasspeci-
fied in this standard, the leak detector should meet the
NOTE 2—Caution:The liquid tracer gas supply should not be heated
following minimum requirements:
above ambient temperature.
8.1.1 Sensor—Alkali-ion diode or electron capture.
9.2 Pure Air, Air from Which Halogens Have Been Removed
8.1.2 Readout—Panel instrument or digital readout.
to a Level of Less Than 1 ppb (or Other Suitable Nonhalogen
−11 −14
8.1.3 Range (Linear)—4.5 310 to 1.3 310 mol/s
Gas, Such as Nitrogen).
−6 −9 3 2
(1 310 to 1 310 Std cm /s) full scale.
9.2.1 Requirements:
8.1.4 Response Time—3 s or less.
9.2.1.1 Less than 1 ppb of halogen.
8.1.5 Stability of Zero and Sensitivity—Amaximum varia-
9.2.1.2 Less than 10 ppm of gases reactive with oxygen,
tion of 615 percent of full scale on most sensitive range while
such as petroleum-base solvent vapors.
probeisinpureair;amaximumvariationof 65percentoffull
9.2.1.3 Dew point 18°F (10°C) or more below ambient
scale on other ranges, for a period of 1 min.
temperature.
8.1.6 Controls:
9.2.1.4 Shall be reasonably free from rust, dirt, oil, etc.
8.1.6.1 Range—Preferablyinscalestepsofabout3timesor
9.2.2 Production of Pure Air, or Other Gas—Air or gas of
10 times.
suitable purity, may be produced by first passing it through a
8.1.6.2 Zero—Automatic zeroing option is desirable.
conventional filter-drier (if necessary) and then through acti-
8.2 Halogen Leak Standard—To perform leak tests as
vated charcoal.
specified in this standard, the leak standard should meet the
following minimum requirements:
−10 −14 −5
10. Calibration
8.2.1 Ranges—4.5 310 to 4.5 310 mol/s (10
−9 3
to 310 Std cm /s) full scale.
10.1 The leak detectors used in making leak tests by these
8.2.2 Adjustability—Adjustable leak standards are a conve-
methods are not calibrated in the sense that they are taken to
nience, but are not mandatory.
the standards laboratory, calibrated, and then returned to the
8.2.3 Accuracy—625 percent of full-scale value or better.
job. Rather, the leak detector is used as a comparator between
8.2.4 Temperature Coeffıcient—Shall be stated by manufac-
a leak standard (set to the specified leak size) which is part of
turer.
the instrumentation, and the unknown leak. However, the
8.3 Other Apparatus—Fixtures or other equipment specific
sensitivity of the leak detector is checked and adjusted on the
to one test method are listed under that method.
job so that a leak of specified size will give a readily
observable, but not off-scale reading. More specific details are
9. Material
giveninSection11underthetestmethodbeingused.Toverify
detection,referencetotheleakstandardshouldbemadebefore
9.1 Test Gas:
and after a prolonged test. When rapid repetitive testing of
9.1.1 Test-Gas Requirements—To be satisfactory, the test
many items is required, refer to the leak standard often enough
gas should be nontoxic, nonflammable, not detrimental to
to assure that desired test sensitivity is maintained.
common materials, inexpensive, and have a response factor of
one. R-12 (dichlorodifluoromethane, CCl F ) and R-22
2 2
11. Procedure
(monochlorodifluoromethane, CHClF ) have these character-
istics.R-12iscommonlyusedunlessthehigherpressureofthe
11.1 General Considerations:
more expensive R-22 is needed (130 psig versus 70 psig at 70
11.1.1 Test Specifications—Use a testing specification that
−10
F).Ifthetestspecificationallowsleakageof4.5 310 mol/s
includes the following:
−5 3 2
(1 310 St
...
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