ASTM E479-91(2006)
(Guide)Standard Guide for Preparation of a Leak Testing Specification (Withdrawn 2014)
Standard Guide for Preparation of a Leak Testing Specification (Withdrawn 2014)
SIGNIFICANCE AND USE
For any product to be tested the geometrical complexity will vary widely. However, the basic concept of determining an operative leakage specification regardless of geometries is much the same for all, whether it be simple, ordinary, or complex.
The data required for writing the OS, which is total leakage (moles), time(s), and pressure difference across the leak, are either available or can be determined by tests or measurements.
A user who selects values to be used in a leakage specification as a result of someone else having used the value or simply because of prestige reasons, may find the value or values unsatisfactory for the product.
A specification that is too restrictive may result in excessive leak testing costs. A specification that is not restrictive enough may result in premature product failure, or increased warranty costs, or both.
A typical illustration for determining a leakage specification, using the complex geometry of a refrigerant system for an example, will be used throughout this recommended guide. It is well to point out that the user should realize that the values and test methods selected do not necessarily represent the best or typical ones for this application.
SCOPE
1.1 This standard is intended as a guide. It enumerates factors to be considered in preparing a definitive specification for maximum permissible gas leakage of a component, device, or system. The guide relates and provides examples of data for the preparation of leak testing specifications. It is primarily applicable for use in specifying halogen leak testing methods.
1.2 Two types of specifications are described:
1.2.1 Operational specifications (OS), and
1.2.2 Testing specifications (TS):
Total, and
Each leak.
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.
WITHDRAWN RATIONALE
This standard is intended as a guide. It enumerates factors to be considered in preparing a definitive specification for maximum permissible gas leakage of a component, device, or system. The guide relates and provides examples of data for the preparation of leak testing specifications. It is primarily applicable for use in specifying halogen leak testing methods. Formerly under the jurisdiction of Committee E07 on Nondestructive Testing, this test method was withdrawn in July 2014. This standard is being withdrawn without replacement because it is too halogen-specific or refrigerant-oriented.
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 ASTM website.
General Information
Relations
Standards Content (Sample)
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:E479 −91(Reapproved 2006)
Standard Guide for
Preparation of a Leak Testing Specification
This standard is issued under the fixed designation E479; 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 3.1.2 testing specification (TS)—a specification for the
detection, location, or measurement, or a combination thereof,
1.1 This standard is intended as a guide. It enumerates
of leakage. The operational fluid usually is not detectable with
factors to be considered in preparing a definitive specification
commercially available leak detectors. The leak test must be
for maximum permissible gas leakage of a component, device,
performed with a suitable test gas containing a tracer to which
or system.The guide relates and provides examples of data for
the detector is sensitive. The pressure magnitude and pressure
the preparation of leak testing specifications. It is primarily
direction may vary greatly from operational conditions. These
applicable for use in specifying halogen leak testing methods.
and other factors are to be considered and evaluated when the
1.2 Two types of specifications are described:
leaktestingperformedtotherequirementsoftheTSistoresult
1.2.1 Operational specifications (OS), and
in a product that meets most of the OS requirements. In
1.2.2 Testing specifications (TS):
addition, should a product be tested with a detector or tracer
1.2.2.1 Total, and
probe from point to point, allowance should be made for the
1.2.2.2 Each leak.
possibilityoftwoormoreleaks,eachcausinglessleakagethan
1.3 This standard does not purport to address all of the thetotalleakagemaximum,butaddinguptoanamountgreater
safety concerns, if any, associated with its use. It is the
than allowed.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Specification Content and Units
bility of regulatory limitations prior to use.
4.1 The content and units of the specification should relate
the following data:
2. Referenced Documents
4.1.1 Mass flow per unit of time, preferably in moles per
2.1 ASTM Standards:
second (mol/s).
E427PracticeforTestingforLeaksUsingtheHalogenLeak
4.1.2 The pressure differential across the two sides of
Detector Alkali-Ion Diode (Withdrawn 2013)
possible leaks, and the direction, in pounds per square inch
E432Guide for Selection of a Leak Testing Method
(psi) or moles (mol).
4.1.3 Any special restrictions or statement of facts that
3. Terminology
might prohibit the use of a particular type of leak testing
3.1 Definitions:
method.
3.1.1 operational specification (OS)—a specification from
4.1.4 The methods of the leakage specification shall not be
which the others are derived. The specification specifies and
limited to any one particular method unless it is the only one
states the limits of the leakage rate of the fluid to be used for
suitable. Specific leak testing methods can be selected when
the product using criteria such as failure to operate, safety, or
careful consideration of the facts is outlined (refer to Guide
appearance.
E432 or the other applicable documents of Section 2).
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
5. Significance and Use
tiveTestingandisthedirectresponsibilityofSubcommitteeE07.08onLeakTesting
Method.
5.1 For any product to be tested the geometrical complexity
Current edition approved May 1, 2006. Published June 2006. Originally
willvarywidely.However,thebasicconceptofdeterminingan
approvedin1973.Lastpreviouseditionapprovedin2000asE479-91(2000).DOI:
operative leakage specification regardless of geometries is
10.1520/E0479-91R06.
For ASME Boiler and Pressure Vessel Code applications see related Guide
much the same for all, whether it be simple, ordinary, or
SE-479 in Section II of that Code.
complex.
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
5.2 The data required for writing the OS, which is total
Standards volume information, refer to the standard’s Document Summary page on
leakage (moles), time(s), and pressure difference across the
the ASTM website.
4 leak, are either available or can be determined by tests or
The last approved version of this historical standard is referenced on
www.astm.org. measurements.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E479−91 (2006)
5.3 A user who selects values to be used in a leakage because of the requirements of the testing specification that
specification as a result of someone else having used the value these and other factors are considered, and that required leak
or simply because of prestige reasons, may find the value or
testing at levels to ensure acceptable quality levels in the final
values unsatisfactory for the product. productismadewiththeconsiderationforalessertestingcost.
Often it is necessary to divide the leakage allowance equitably
5.4 A specification that is too restrictive may result in
among various components, taking into account the statistical
excessive leak testing costs. A specification that is not restric-
probability of the largest allowable leakage occurring in a
tive enough may result in premature product failure, or
number of a given set of components.
increased warranty costs, or both.
6.3.2.1 Division of Leakage Allowance Among System
5.5 A typical illustration for determining a leakage
Components—Assume in the previous example that the
specification, using the complex geometry of a refrigerant
compressor, condensing and evaporating coils, the expansion
system for an example, will be used throughout this recom-
valve, capacity control valve, and sealed thermostat all have to
mendedguide.Itiswelltopointoutthattheusershouldrealize
be considered.Also assume that the compressor and evaporat-
that the values and test methods selected do not necessarily
ing coil will both be tested separately before assembly into the
represent the best or typical ones for this application.
system, as each has a number of fabricated joints more prone
to leakage than the condensing coil. The condensing coil,
6. Procedure
considered a continuous length of tubing, can be tested at the
6.1 The example that follows is to be construed as appli-
final system test. All components except the thermostat make
cable to the equipment and testing method cited, and is not to
upsomeportionoftherefrigerantcircuit.Howthenshouldthe
be construed as setting up mandatory leakage rates for any
leakage allowance be divided among them? The usually
other equipment or method of testing. The example used to
equitable way is to make the division on the basis of the
illustrate the use of this guide is as follows: An automotive
number of joints in each, considering 25 mm of seam as one
air-conditioning system using Refrigerant-12 (R-12, dichlo-
“joint.” A tabulation example on this basis follows:
rodifluoromethane)andconsistingofacompressor,condensing
No. of Joints % of Total
coil, thermostatic expansion valve, evaporating coil, vacuum-
operated hot gas bypass capacity control valve, and a sealed
Compressor 36 28
temperature control thermostat.
Condensing coil 78 60
Expansion 7 5
6.2 OS, Refrigerant Circuit—It is desirable that the re-
Capacity control valve 9 7
chargeable portions of the system operate three years before Total 130 100
requiring additional refrigerant; for the sealed parts, 5 years.
6.4 Factor of Safety for Leak Testing Accuracy—When
Tests show that 6 oz of the normal charge can be lost before
establishing the data for the factor of safety for leak testing
serious operational inefficiency begins, and the neoprene con-
accuracy and when performed by various people using differ-
necting hoses have a basic permeation rate of 1 oz/year.
ent equipment, facilities, or operating standards, the resulting
Inspectionofthesystemshowsthatthevacuumoperatorofthe
data usually will vary tremendously. Results of a round-robin
capacity valve and the thermostat are not directly connected to
testconductedbyASTMresultedinaspreadofthetestdataof
the refrigerant circuit, and can thus be considered separately.
about one decade. This value is considered valid for leak tests
6.2.1 Calculations:
using procedures and equipment described in Section 2.
Leakage to be detected = 6 oz (total loss) − 1 oz × 3 years = 3 oz
Therefore any operational specification may apply a factor of
Period = 3 years
⁄3 or 0.3.
Rate = 3 oz/3 years = 1 oz/year. Rate (standard units) = 1 oz/year ×
−4 −9
1.8×10 (or 0.00018 = R-12 conversion factor) = 7.308 × 10 moles/s. See
6.5 Factor of Safety for Number of Leaks per System—
6.6.3
Pressure —The maximum operating temperature of the system will be
Whenaunitordevicehasanumberofpointsthatmayleak,the
77°C at which temperature the pressure of the refrigerant will be about 2.07
leak test is to be performed by point-to-point probing.There is
MPa. Pressure difference = 2.07 MPa (internal) − 0.10 MPa
a possibility that the sum of all leaks smaller than the
(atmosphere) = 1.97 MPa.
specification total may add up to an amount in excess of it.
6.2.2 Therefore, the following would appear on the appro-
However, this is dependent upon the number of leak possibili-
priate documents: Leakage Specification (Operational):
−5
ties or on whether there is any distortion of the normal leak
3.6×10 MPa max at 1.97 MPa pressure difference
−9
distribution curve, which covers many decades of sizes. The
(7.308×10 moles/s excluding hose permeation).
factor assigned here may depend upon a judgment of the
6.3 TS, Refrigerant Circuit:
probability of such an event occurring, the degree of confi-
6.3.1 ForaunittobetestedattheOSlevel,anyinaccuracies
dence needed in the leak test, and the safety factor that can be
inthetestcouldcausepossibleunitacceptancewheninfactthe
afforded.Inthisexample,assumethatthecondensingcoilisof
unit may leak in excess of the amount allowed. Most testing
welded aluminum which has a strong tendency to have
conditions cannot duplicate operating conditions. Should a
−10
porosities that leak in the range of 4.06×10 moles/s. For
point-by-point probing technique be used, a number of smaller
this reason, the TS total will be divided by five for this item,
leaksmayallowatotalleakageinexcessofthevaluespecified.
and by three for the others, that is, a factor of 0.2 and 0.3
6.3.2 In addition, some portions of the system may be
respectively.
purchasedasacompletedoperativecomponent.Theirpotential
contribution to the total system leakage must be limited. It is 6.6 Factor of Safety for Test versus Operating Conditions:
E479−91 (2006)
6.6.1 Pressure—As a recommendation, the leakage is as- (1) Refrigerant System Side Specifications: Test
sumedtobeproportionaltothedifferenceofthesquaresofthe Specification, Total—In the tabulation example in 6.3.2.1 an
pressures on each side of the leak. However, for this example, allowance of 5% for the expansion valve compartment was
itisassumedthata2.76MPapressuredifference,highpressure established. Applying this to the similar system specification:
−9 −11
internal, is needed. This would allow combining the leak test 7.308×10 ×0.05=36.54×10 moles/s. (This allowance
with the burst test which is fixed at 2.86 MPa, absolute might be increased on a statistical basis if desired.) Thus the
internal−0.10 MPa, absolute external=2.76 MPa. This pres- specification for this component can be tabulated as follows:
sure will possibly reveal leaks that can only develop with Maximum Leakage at 2.76 MPa Differential,
higher stress. With the operating condition at 2.07 MPa, gage
Pressure Internal (Note Appendix Table X1.1, Nos. 5–8)
max, greater leakage can be expected at the higher test
pressure. Calculate the Factor of Safety as follows: Maximum
Type of Leakage,
2 2 2 2 2
FactorofSafety 5 P 2 P / P 2 P 5 2.76
~
~ 2 1 ! ~ 3 1 ! Specification Seller User moles/s
2 2 2
20.1 / 2.07 20.1 51.8
! ~ ! −11
Testing, total X 36.54 × 10
−12
Testing, total X 36.54 × 10
where:
−11
Testing, each leak X 12.18 × 10
−12
Testing, each leak X 12.18 × 10
P = pressure, atmospheric,
P = high pressure (internal), and
Observethatafactorof ⁄3hasbeenappliedforprobetesting
P = pressure, operating.
3 versus total leakage testing.
(2) Operator Assembly Specifications—This is an indepen-
Therefore, a factor of 1.8 can be applied to the operational
dent system, and the operational specification must be estab-
specification.
lished as before. Make the following calculations:
6.6.2 Test Gas—Except at high ambient temperatures, most
Maximum loss of R-12 before malfunction: 2 standard cm
refrigerant gases normally used in a system will liquefy before
Time limit: 5 years
the test pressure is reached. Nonetheless, other gases or
Pressure (internal) 0.6 MPa
mixture of gases, will be required for leak testing. The more
7 −13
suitable gases, such as helium, nitrogen, air, etc., have a Operational specification = 2/(5 × 3.15 × 10 )=5.3×10 moles/s
−4 −4
viscosity of about 1.9×10 P, compared to 1.2×10 for
Using factors previously discussed, the specifications may
most halogenated refrigerants, compared to 1×10 for water
be tabulated as follows:
and 1×10 for lubricating oils. The leakage of a fluid is
Maximum Leakage at 0.48 MPa Differential,
inverselyproportionaltoitsviscosity.Therefore,thecorrection
Pressure Internal (Note Appendix Table X1.1, Nos. 9–13)
for test fluid is extremely important, particularly when liquids
Maximum
−4
are involved. In this example a factor of 1.2×10 divided by Type of Leakage,
−4
Specification Seller User moles/s
1.9×10 =0.6 will be used.
−13
6.6.3 Test Specifications—From an operational specification
Operational X 5.3 × 10
−9
−14
Testing, total X 16.24 × 10
of 7.308×10 moles/s. (excluding hoses) the testing specifi-
−14
Testing, total X 4.06 × 10
cation for the completed system is derived (Note Appendix
−14
Testing, each leak X 12.18 × 10
−14
Table X1.1, Nos. 1–4). Test specification, to-
Testing, each leak 4.06 × 10
−5
tal=1.8×10 ×0.3 (equipment accuracy)×1.8 (gas pres-
Note that the factors used are larger than normal, as the
−5 −6
sure)×0.6 (gas viscosity)=1.8×10 ×0.32=5.8×10 .
sensitivity limit for the detection of halogen has been ap-
Round the coefficient to the nearest whole number. The total
proached. (See Practice E427).
for all leaks will be: “Leakage specification, testing, total:
6.6.4.2 Control Valve—There are two separate leakages to
−10
24.36×10 moles/s. max at 2.76 MPa press
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.