ASTM E908-98(2004)
(Practice)Standard Practice for Calibrating Gaseous Reference Leaks
Standard Practice for Calibrating Gaseous Reference Leaks
ABSTRACT
This practice establishes the standard procedures for calibrating leak artifacts of a specified gas, that may be used for determining the response of leak detectors, or in other situations where a known small flow of gas is required. The purpose of this practice is to establish calibration without reference to other calibrated leaks in as straightforward a manner as possible using the likeliest available equipment. The two types of leaks considered here are Type I, which is pressure to vacuum, and Type II, which is pressure to atmosphere. Three calibration methods are described under each type of reference leak, as follows: Method A—accumulation comparison using a known volume of tracer gas at specified conditions of temperature and pressure as a reference; Method B—accumulation comparison using a reference leak artifact calibrated using Method A; and Method C—direct measurement of leak rate by timing the movement (displacement) of a liquid slug, by the leak, in a capillary tube of known dimensions.
SCOPE
1.1 This practice covers procedures for calibrating leak artifacts of a specified gas, that may be used for determining the response of leak detectors, or in other situations where a known small flow of gas is required. The purpose of this practice is to establish calibration without reference to other calibrated leaks in as straightforward a manner as possible using the likeliest available equipment. While the uncertainties associated with these procedures will most likely be greater than those obtained via traceable calibration chains (on the order of 10 %), these procedures allow independent means of establishing or verifying the leakage rate from leak artifacts of questionable history, or when traceable leak artifacts are not available.
1.2 Two types of leaks are considered:
1.2.1 Type I—Pressure to vacuum.
1.2.2 Type II—Pressure to atmosphere.
1.3 Three calibration methods are described under each type of reference leak:
1.3.1 Method A—Accumulation comparison, using a known volume of gas at specified conditions of temperature and pressure as a reference.
1.3.2 Method B—Accumulation comparison, using a leak artifact calibrated using Method A.
1.3.3 Method C—Displacement of a liquid slug, by the leak, in capillary tube of known dimensions.
1.4 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be appropriate.
1.5 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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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E908 − 98(Reapproved 2004)
Standard Practice for
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Calibrating Gaseous Reference Leaks
This standard is issued under the fixed designation E908; 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.
1. Scope 2. Referenced Documents
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2.1 ASTM Standards:
1.1 This practice covers procedures for calibrating leak
E425Definitions of Terms Relating to Leak Testing (With-
artifacts of a specified gas, that may be used for determining
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drawn 1991)
the response of leak detectors, or in other situations where a
E427PracticeforTestingforLeaksUsingtheHalogenLeak
known small flow of gas is required. The purpose of this
Detector(Alkali-Ion Diode)
practice is to establish calibration without reference to other
E479Guide for Preparation of a Leak Testing Specification
calibrated leaks in as straightforward a manner as possible
F134Test Methods for Determining Hermeticity of Electron
using the likeliest available equipment.While the uncertainties
Devices with a Helium Mass Spectrometer Leak Detector
associated with these procedures will most likely be greater
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(Withdrawn 1996)
than those obtained via traceable calibration chains (on the
2.2 Other Documents:
order of 10%), these procedures allow independent means of
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AVS 2.2-1968Method for Vacuum Leak Calibration
establishing or verifying the leakage rate from leak artifacts of
Recommended Practices for the Calibration and Use of
questionable history, or when traceable leak artifacts are not
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Leaks
available.
1.2 Two types of leaks are considered:
3. Summary of Practice
1.2.1 Type I—Pressure to vacuum.
3.1 Method A—Accumulation comparison, using a known
1.2.2 Type II—Pressure to atmosphere.
volume of tracer gas:
3.1.1 This method uses a closed chamber of nonreactive
1.3 Threecalibrationmethodsaredescribedundereachtype
material having a means of removing all tracer gas and a
of reference leak:
connection to the tracer sensor.
1.3.1 MethodA—Accumulation comparison, using a known
3.1.2 A small, known quantity of tracer gas is discharged
volume of gas at specified conditions of temperature and
intothechamberandtheresponserecordedforaperiodoftime
pressure as a reference.
inwhichitisanticipatedtheunknownleakwillrequiretoreach
1.3.2 Method B—Accumulation comparison, using a leak
the same concentration.
artifact calibrated using Method A.
3.1.3 The tracer gas is removed from the chamber, and the
1.3.3 MethodC—Displacementofaliquidslug,bytheleak,
unknown leak is allowed to discharge into it until the sensor
in capillary tube of known dimensions.
response equals that of 3.1.2.
3.1.4 The leakage rate in mol/s can be calculated as:
1.4 The values stated in inch-pound units are to be regarded
as the standard. The metric equivalents of inch-pound units
Q 5PV ~t·R·T! (1)
m
may be appropriate.
where:
1.5 This standard does not purport to address all of the
P = pressure in known volume in atmospheres (1
safety concerns, if any, associated with its use. It is the
atm=101 325 Pa),
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2
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
the ASTM website.
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This practice is under the jurisdiction of ASTM Committee E07 on Nonde- The last approved version of this historical standard is referenced on
structive Testing and is the direct responsibility of Subcommittee E07.08 on Leak www.astm.org.
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Testing Method. AvailablefromAVS,AmericanVacuumSociety,335E.45thStreet,NewYork,
Current edition approved May 1, 2004. Published June 2004. Originally N.Y., 10017.
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approved in 1982. Last previous edition approved in 1998 as E908-98. DOI: C.D. Ehrlich and J.A. Basford, Journal of Vac. Sci, Technology, A(10), 1992,
10.1520/E0908-98R04. pp. 1–17.
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E908 − 98 (2004)
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NOTE 1—Other gases or detectors, or both, can be used with little
V = the volume of gas in cm introduced in 3.1.2,
difference in procedures or interferences.
t = the time in seconds required for the concentration in
4.1.2 PressureRise—Therewillinevitablybesomepressure
3.1.3 to equal that in 3.1.2,
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R = gas constant=82.06=1 atm cm /mol/K, and
riseinaclosedevacuatedchamber,duetooutgassingandsmall
T = absolute temperature, K
...
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